WO2002075361A2 - Geosteering of solid mineral mining machines - Google Patents

Abstract

A rock avoidance control system for solid mineral mining using a forward looking rock/mineral interface (15,16) detector and controlling the miner (10) to cut to the detected rock/mineral interface (15,16). One or more armored gamma ray detectors (20,120) are positioned near the cutter (12) and move with the cuter (12) such that the angular size of the field of view is not reduced. Angular movements of the cutter (12) are measured and used for calculating the rock/mineral interface (15,16) location. A device is incorporated within an armored rock detector (20,120) to sense angular movements of the cutter boom (11) and to correlate changes in gamma radiation (28) to the angular movements, within selected energy ranges. The thickness of the remaining coal (24) is calculated by measuring the rate at which the gamma radiation (28) increases. In one embodiment, rock detectors (20,120) are used to steer the cutting of the leading drum and/or the trailing drum a long-wall mining system.

Description

GEOSTEERING OF SOLID MINERAL MINING MACHINES

[0001] This application claims priority from U.S. provisional application serial no.

60/276,896, filed March 20, 2001, co-pending U.S. application serial no.

09/811,781, filed March 20, 2001, co-pending U.S. application serial no.

09/626,744, filed July 26, 2000, and co-pending U.S. application serial no.

09/471,122, filed December 23, 1999, all of which are incorporated by reference

herein in their entireties.

BACKGROUND

[0002] The present invention generally relates to a method and apparatus for

detecting the presence of rock during coal or ore n ining operations.

[0003] A more effective way to control solid mineral mining equipment, or

miners, has been greatly desired by the mining industry. Many concepts have already

been tried, over a period of many years, to improve mining controls to increase the

amount of coal, or other mineral, cut by the rnining equipment and to decrease the

amount of undesirable rock cut by the mining equipment. Many of these concepts

involve "guidance" systems that direct or point the miner where to cut, based on

predictions or assumptions related to the location of the mineral-rock interface.

These predictions or assumptions are typically based on data or information obtained

from the experience of the mining equipment from previous cuts.

[0004] One seemingly simplified approach employs repetitive cycles. A computer

is instructed by the miner operator to perform specific cycles or the control system is programmed to memorize operator actions over a cycle and duplicate them. This

approach does not work well because of the high variability of the rock and mineral

formations and operational considerations. This approach is particularly ineffective

when applied to continuous miners, because the miner rides on the floor that has

been cut resulting in cutting errors (e.g., leaving an excessive layer of coal on the

floor, or cutting excessively down into the rock on die floor) for one cut tending to

be amplified for subsequent cuts.

[0005] In the case of long- wall mining there is some opportunity to utilize what

has been learned on one pass along the mineral face to improve upon cutting strategy

for the next pass along the face. One approach utilizes a memory system to log the

profiles of the rock face at the floor and roof on one pass and then to use this

knowledge to influence the cutting as the cutters pass along the same face, going in

the opposite direction. This approach has been of only limited success because the

rock face profile on one pass does not exactly reflect the needed rock face profile of

the next pass and because there is much variability in the formations and niining

operations. Consequently, such equipment and operation are limited in their

efficiency in cutting to the rock-coal interface using guidance strategy.

[0006] Gamma detectors have, over the years, shown promise in detecting the

location of the rock- wall interface for both continuous miners and long wall miners,

but typically have not been effective because they have been installed so as to measure

where the rxύning equipment has been rather than where the cutter is going. One

reason that gamma detectors have often been used in a non-effective manner is that the detectors

could not physically survive if subjected to the environment in locations where they

would be most effective.

[0007] Numerous other approaches have already been conceived and tested over

the years for directing or guiding mining equipment. Most of these concepts have

not proven to be commercially successful due to technical deficiencies,

implementation problems, and cost. Many types of sensors have been incorporated

into control systems to monitor the shape, profile and characteristics of the

formations through which the mining equipment is cutting and to make cutting

decisions on where to point subsequent cuts based on this information. Thus, these

approaches fail not only due to practical implementation problems but also because

of a fundamental flaw with the concept. Knowledge about the shapes, profiles, or

characteristics of d e formation being passed through does not provide accurate

information about the formation just ahead, for which the cutting decisions must be

made.

[0008] In most of the examples above, the control systems employed have been

complex and expensive. A typical approach is to use a gravity-referenced or inertial-

referenced control system, with various other sensors added. Some of these control

concepts have been referred to as "horizon control systems." A horizon control

system typically uses the gravity-referenced sensors or inertial-referenced sensors that

keep trad of the orientation of the continuous miner and the profile of the roof and

floor. [0009] In principle, the horizon control system approach is to control the mining

equipment by use of guidance systems adapted to mining applications. However, as

discussed above, guidance systems cannot generate accurate information about the

formation to be cut because d e historical information that they log in detail is not a

valid indicator of what is ahead. Moreover, these guidance systems are complex and

costly.

[0010] It is described in co-pending U.S. application serial no. 09/811,781 that

in underground coal mining, a properly designed and properly positioned, forward-

looking armored gamma detector, in combination witii a suitable control system, can

be effective for reducing the amount of rock taken while extracting an increased

amount of coal or other mineral. A mining control system that incorporates such

forward-looking detectors is referred to as a "rock avoidance system." The use of

rock avoidance systems can help cut the floor of the mine very smoothly and simplify

the job of the operator. Rock avoidance systems allow continuous miner operators to

be positioned further from the coal face, thus reducing health hazards.

[0011] However, even when used with forward-looking rock detectors as

described in co-pending U.S. application serial no. 09/811,781, these horizon

control systems do not utilize the data generated by the rock detectors as fully as it

could be used, because the systems are conceived and designed to guide or point,

determining the direction to move, rather than being appropriately responsive to sources of external intelligence

such as armored gamma detectors. In addition, inertial or gravity referenced systems

are not typically designed to provide precision and timely measurements of cutter

movements that will allow a rock detector to achieve maximum sensing accuracy.

[0012] Rock avoidance systems that rely upon complex guidance systems are

costly and, complicated and have some inherent inefficiency resulting from their

metiiodology. A need now exists to provide an accurate rock avoidance system that

is simple, economical and easy to install and operate. There is also a need for such a

rock avoidance system for use on long- wall mining equipment as well as continuous

niining equipment.

SUMMARY

[0013] These deficiencies are alleviated to an extent by the present invention

which in one aspect provides a rock avoidance system for solid mineral naming using

a forward looking rock/rnineral interface detector and controlling the miner to cut to

the detected rock/mineral interface.

[0014] In anod er aspect, vertical movements of the cutting mechanisms are

measured for the purpose of being used by the rock detector to make more accurate

mathematical calculations of the location of the coal-rock interface. [0015] In another aspect, a method is provided for improving accuracy by

incorporating a device within an armored rock detector to sense angular movements

of die cutter boom and to correlate changes in gamma radiation to the angular

movements, within selected energy ranges. An armored rock detector, so configured,

can make effectively accurate cutting decisions under a wide range of niining

conditions without support from complex control systems. Cutting decisions from

the rock detector are transmitted directiy to the miner control system to slow or stop

the movement of the cutter toward d e coal- rock interface or to a control and display

panel where other constraints and logic may be applied.

[0016] In another aspect, the change in attenuation is determined, and the

thickness of the remaining coal is calculated by measuring the rate at which the

gamma radiation increases. Greater accuracy in the calculations is achieved by

measuring the relative changes in gamma counts for various energy levels. Quick

response is achieved so that the cutter of a continuous miner moving toward the rock

on each cut may be stopped before reaching the rock by employing curve-fitting

techniques tiiat correlate the gamma ray measurements with incremental movements

of the cutters. The rock detector is outfitted with die required logic elements and

algorithms.

[0017] In yet another aspect, a method of geosteering is provided on a continuous

miner is for a shearing down to be slowed slightiy as the floor is approached.

Control of

the shearing is accomplished by signals from the rock detector which operate the solenoids that control the hydraulic system. Following the shearing stroke, the miner

is placed in reverse for a short distance in order to remove the small cusp left: behind

die cutter. During tins backing up, the rock detector will maintain the boom at

constant angle so tiiat die floor will be cut level. Next, die operator moves the miner

forward slowly, simultaneously shearing up, to sump to approximately fifty percent

the diameter of the cutter. If a rock detector is used at the roof, it will slow the cut

slightiy before reaching the rock interface and then stop d e cut. While the boom is

being held at a constant angle by the rock detector, the operator drives the miner

forward to a full sump. At tiiis point, the operator is ready to start the shear down to

repeat the cycle.

[0018] In another aspect, die rock detector is placed near the cutter on a

continuous miner, so that it can detect the radiation passing through the coal in front

of the advancing cutter. When cutting at the floor, the detector moves with the

advancing cutter such that the angular size of the field of view is not reduced as the

cutter moves down toward the bottom portions of the miner.

[0019] In another aspect, the rock detector is placed near the cutter on a long-

wall miner When geosteering the trailing drum, the divergence rock detector is

positioned within a few feet of the bottom edge of the picks so that a divergence

between the tips of the picks and the rock will be detected before coal is left

unmined. Also, the divergence rock detector is positioned close to the picks so that

the cutter can be biased toward divergence without concern for leaving coal

unmined. In another aspect, a convergence rock detector is used on the trailing drum, and positioned close enough

to the cutter to be able to detect rock that is being mined and then rnixed with the

coal. In a preferred embodiment a geosteering system is provided that includes an

armored rock detector, positioned on die boom of a continuous miner to view the

area where coal is being cut, to measure the changes in gamma radiation as a result of

the coal being cut away, to correlate the changes in gamma radiation with

incremental changes in the position of die cutter, and to make logical decisions when

to slow and/or to stop the cutter before cutting into the rock. In order to obtain

precise measurements of rotation of the cutter boom or of the vertical movements of

the cutter, an accelerometer is incorporated into the rock detector.

[0020] In another preferred embodiment, the geosteering syst m includes a

control and display panel that keeps the operator informed about the cutting

progress, particularly in regard to cutting at the roof. This panel accepts data and

decisions from the rock detectors and also displays the position of the cutter relative

to the most recent cuts at the floor. A solid-state accelerometer, in the form of a

micro-chip, is included as part of the electronics. This accelerometer acquires

additional information on the instantaneous motion of the continuous miner and

sends tiiat information to the rock detector so tiiat d e rock detector can subtract

errors resulting from motion of the miner from the measured incremental movement

of the cutter and rock detector. In a typical application, gamma data is correlated to

the incremental movements of the cutter and tiiis information is retained wit^ήin the

control and display panel for at least ten cutting cycles. Detailed, automatic analysis of this data allows refinement of the logical

decisions to be made for future cutting cycles.

[0021] In another embodiment, an encoder and/or a potentiometer are provided

to instantly measure and report to the rock detector, the movement of the boom, on

which the cutter is attached. Such substantially instant, precise data allows the rock

detector to make fast, accurate measurements. When rock detectors are being used

for controlling cutting at the roof, in addition to controlling cutting at the floor,

such auxiliary devices provide supporting information to the rock detector, to the

miner control system, and to die operator. This preferred embodiment includes a

cutter motion indicator, containing an optical encoder and a potentiometer, at the

pivot point of the boom. By combining this precise, high-speed data with the

expanded computational capabilities of other preferred embodiments, advanced

automation at higher speeds of operation are made possible.

[0022] In yet another embodiment, rock detectors are used to steer the cutting of

a long- wall mining system. In some applications, both the leading drum and the

trailing drum of a long -wall shearing system are geo-steered by use of rock detectors.

Whenever the mining equipment reverses direction, the leading drum becomes the

trailing drum. The armored rock detector is placed near the bottom of the cowl for

the trailing drum and allows direct view of the surface being cut by the drum. The

rock detector begins by slowly raising the drum until die rock detector determines

that coal is being left unmined. Raising and lowering of the drum by the rock

detector is accomplished by operating the solenoids that control the hydraulic system. Upon recognition that a

small amount of coal is being left over the rock, die rock detector quickly lowers the

drum by approximately two inches. The amount tiiat the drum is lowered will

depend upon the miner and mining conditions. In one aspect, the rock detector

continues to steer die drum so that the cutting operation cycles between three

conditions (1) removal of only a small amount of rock, (2) preferable removal of all

coal and no rock, and (3) leaving up to one or two inches of coal over the rock. In

the case where die coal bonds well to die rock, typically fire clay, the maximum

amount of coal occasionally left will preferably be less than two inches. The

preferable result is that for most of the cut along the face, almost no floor rock is

mined and very Htde coal is left unmined. For die case where soft coal is not bonded

to the fire clay, preferably substantially all of the coal will be removed substantially all

of the time.

[0023] These and other objects, features and advantages of the invention will be

more clearly understood from the following detailed description and drawings of

preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic view of a continuous miner including a pair of rock

detectors constructed in accordance with a preferred embodiment of the invention.

[0025] FIG. 2 is a graph showing a typical equilibrium energy spectrum for a

homogenous rock formation above and below a coal vein. [0026] FIG. 3 is a graph showing the effects of coal on a typical equilibrium

energy spectrum for a homogenous rock formation.

[0027] FIG. 4 is a partial cross-sectional view of one of the armored rock detectors

of FIG. 1.

[0028] FIG. 5 is a cross-sectional view of one of the rock detectors of FIG. 4.

[0029] FIG. 6 is a view taken along section line VI-NI of FIG. 5, at the

scintillation element.

[0030] FIG. 7 is a view taken along section line VII-NII of FIG. 5, at the photo-

multiplier tube.

[0031] FIG. 8 is a view taken along section line VHI-Nffl of FIG. 5, at the

accelerometer.

[0032] FIGS. 9a and 9b are graphs of gamma ray counts versus time and versus

change of cutter boom angle.

[0033] FIG. 10 is a schematic drawing of a logic element used with a rock

detector constructed in accordance with an embodiment of the invention. [0034] FIG. 11 is a schematic drawing of a logic element and digital signal

processor used with a rock detector constructed in accordance with an embodiment

of die invention.

[0035] FIG. 12 is a schematic drawing of a logic element and digital signal

processor used with a pair of rock detectors constructed in accordance with an

embodiment of die invention.

[0036] FIG. 13 is a schematic drawing of a junction box and cables used in an

embodiment of die invention.

[0037] FIG. 14 is a schematic drawing of a control and display panel and cables

used in an embodiment of the invention.

[0038] FIG. 15 is a schematic drawing of a control and display panel,

accelerometer and cables used in an embodiment of die invention.

[0039] FIG. 16a is a view of a cutter motion indicator used with a rock detector in

accordance with an embodiment of the invention.

[0040] FIG. 16b is a cross-sectional view of the cutter motion indicator of FIG.

16a.

[0041] FIG. 17 is a cross-sectional view of a linkage mechanism used with cutter

motion indicator of FIG. 16a. [0042] FIG. 18 is a schematic view of a longwall shearing system in accordance

with an embodiment of the invention.

[0043] FIG. 19 is a schematic of a pair of rock detectors on die trailing shear of

the long- wall miner of FIG. 18.

[0044] FIG. 20 is a graph of predicted and measured floor depth versus distance

traveled.

[0045] FIG. 21 is a graph of detected gamma ray counts versus coal/rock

interface depth.

[0046] FIG. 22 is a graph like FIG. 21.

[0047] FIG. 23 is a graph like FIG. 21.

[0048] FIG. 24 is a cross-sectional view of a rock detector constructed in

accordance with another embodiment of the invention.

[0049] FIG. 25 is a cross-sectional view taken along line XXV-XXV of FIG. 24.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0050] The present invention provides a more accurate and faster solid mineral

mining by use of a rock avoidance system that applies a new methodology called

geosteering to solid mineral ruining. [0051] Geosteering techniques have been used in oilfield applications as

exemplified in US patents 5,230,386, RE 035,386, and 5,812,068. With

geosteering, the distance to the oilfield bed boundary is measured while in the

formation, and the drill string is steered by direct measurements of the formation so

tiiat it stays in the mineral vein. This technology has advanced to the point where

horizontal wells in excess of one mile are routinely drilled. Further, these wells can

now be drilled with die drill string staying in die reservoir formation throughout the

horizontal section. Such geosteering for oilfield applications was recognized as an

important new methodology and a substantial advance over directional drilling

techniques exemplified by US patents 3,982,431 and 4,905,774.

[0052] The "directional drilling" approach to horizontal chilling in oil and gas

wells is somewhat analogous to currentiy-used "horizon control" that has been used

for mining applications. In both cases of directional-based controls, for oil and for

coal, independent attitudinal and/or inertial reference systems provide the basis for

guiding or pointing the machinery. In each application, the extent and profile of a

solid mineral vein to be mined is not predictable. Indeed, the problem is more

critical in coal mining

than in oil well drilling, because the mining operation needs to be accurate to within

inches compared to the accuracy of feet typically required in oil wells.

[0053] Guidance or pointing based on an inertial or gravity based reference

system does not provide the intelligence needed to accurately make the next cut.

The control functions at any moment must be accomplished by signals from sensors that are measuring relevant parameters for the formation just ahead, where the

cutting will occur. Directional control systems, such as horizon control, used in solid

mineral mining have not produced die successes achieved with directional drilling in

horizontal oil wells. Thus, implementation of geosteering to solid rnineral mining

represents an even greater opportunity for improvement than did the implementation

of geosteering for drilling oil and gas wells.

[0054] The principle of geosteering for continuous miners is to keep the cutter

moving between the boundaries of the coal vein and letting the continuous miner

follow the cutter through the geologic formation. Geosteering is more

straightforward than conventional approaches, and is fundamentally simpler in

concept. The actual profile of the tunnel being cut through the earth during mining,

the vertical excursions of the tunnel, and the slope of d e floor and roof of the tunnel

are not primary the primary objective of geosteering. These parameters can be

derived from data acquired while performing geosteering, and may be of some

interest, but such data are the consequence of geosteering rather than being the

guide for cutting.

[0055] Coal is located in a formation between other materials, generally classified

as rock. An example would be a coal seam having black marine shale at the roof and

fire clay, another form of shale, at the floor. In this example, the shale has a

significandy higher level of natural radiation than die coal. As the shale radiation

passes through the coal from the rock, it is attenuated. The thickness of the coal is reduced as a continuous miner removes the coal. Reduction in the thickness of the

coal results in less attenuation so that the gamma radiation reaching the detector

increases as d e coal is cut away. At the point of contact between the cutter and the

rock, there is no attenuation by coal and the gamma radiation is at a maximum. By

measuring the rate at which the gamma radiation increases, the change in attenuation

can be determined, and the thickness of the remaining coal can be calculated.

[0056] Greater accuracy in die calculations is achieved by measuring the relative

changes in gamma counts for various energy levels. Quick response is required

because the cutter of a continuous miner is moving rapidly toward the rock on each

cut and should be stopped before reaching the rock. Since the cutter picks are on a

rotating drum, die advancing face of the cutter is a curve. As the first picks along the

centerline of the drum begin to enter the rock, bare rock is exposed and pieces of

rock are cut away and dragged on top of the coal pile behind the cutter. If the

cutters actually enter the rock, it is desirable to immediately stop the advance of the

cutter to save wear on the picks and avoid cutting undesirable rock. To achieve faster

response and higher

accuracy, curve-fitting techniques are employed by correlating the gamma

measurements with incremental movements of the cutters. The system includes

associated logic elements and algorithms.

[0057] Geosteering, which relies primarily upon measurements of natural gamma

radiation, can only be properly implemented by understanding the physics of the

processes and physical phenomena involved in making and interpreting the gamma measurements. Physical characteristics of the formations and their radiation

properties are reviewed below. The logic elements included in the preferred

embodiments have been created to accomplish the required decision-making, taking

advantage of this understanding of die physics involved, within the confines of the

protected environment provided within die rock detector.

[0058] Radiation flux from coal/rock usually originates from trace levels of

radioactive potassium, uranium, or thorium that are within the rock. In a typical

case, a discrete spectrum of gamma rays is produced by die radioactive decay of the

trace elements. These gamma rays are transported through the formation, losing

energy through Compton scattering (and possibly pair production), until they are

finally photo-electrically absorbed. Within the rock, an equilibrium spectrum is soon

established reflecting a balance between d e production of gamma rays in radioactive

decays, the downscattering of gamma rays to lower energy, and the absorption of

gamma rays through photoelectric absorption.

[0059] When the flux enters the coal region, this equilibrium is upset. The

production of gamma rays in coal is much lower, reflecting a significandy lower level

of potassium, uranium, and thorium. Since the higher energy regions of the

radiation flux are not replenished, the spectrum shifts to lower energies as the gamma

rays are down-scattered and decreases in magnitude as die gamma rays are absorbed.

[0060] The inverse of this process is observed as coal is mined. First, the gamma

flux is low in magnitude and energy, reflecting the extensive absorption by the thick layer of coal. Then, as coal is removed, the magnitude of the flux increases, and the

mean energy of the flux increases.

[0061] A typical equilibrium spectrum for a homogeneous rock formation above

and below a coal vein is shown in FIG. 2. The broad peak at about 100 kev is the

down-scatter peak. Most of the gamma radiation under this peak has lost energy

dirough Compton scattering. If Compton scattering were the only physical process

involved, a 1/E² distribution would be seen, instead of the down-scatter peak.

However, as gamma rays lose energy, their cross-section for photoelectric absorption

increases. This absorption results in the gamma radiation having the lower energy,

producing the backscatter peak that is observed in FIG. 2.

[0062] The formula for die photoelectric cross-section is given as:

where Z is the average atomic number of the formation. The denominator in this

formula shows die strong energy dependence of die cross-section, and explains the

existence of the backscatter peak. The numerator gives the dependence of the cross-

section on the lithology of the formation. [0063] An oilfield convention for describing this dependence is to consider the

photoelectric cross section at E=30.6 kev. At this energy, the numerator = 0.01 and

we have:

[0064] Using this convention, the photoelectric cross-section of coal is found to

range from about 0.1 to about 0.3 barnes/electron, while the rock above and below

die coal typically ranges from 2-5 barnes/electron. As a result, of this difference in

the

photoelectric cross-section, the down-scatter peak for the rock above and below the

coal is at a higher energy than die down-scatter peak for coal.

[0065] It is somewhat easier to visualize these parameters by starting with only

rock and adding coal on top of the rock, as happens when steering the trailing

shearing drum of a long-wall miner. If the drum is raised, a thin layer of coal is

added on top of the rock and the spectrum is shifted to lower energies. Gamma rays

from the rock lose energy as they are Compton-scattered in the coal. The higher

energy regions of the flux are not replenished, because the natural radioactivity of the

coal is much lower than that of the rock. As more coal is added, the gamma rays are

shifted to sufficiendy low energies to allow absorption to be a significant factor again. The reverse of this description then applies to the removal of coal by the cutters on a

continuous miner.

[0066] FIG. 3 shows an example of this phenomenon, presenting the spectrum at

the surface of bare rock (0 cm) and at die surface of a coal layer on top of that rock at

distances of 10 cm and 20 cm from that rock. From the plots on FIG. 3, it is clear

tiiat the percent of flux per energy unit is greater at d e rock face than that observed

dirough a layer of coal.

[0067] Geosteering accomplishes the steering for solid mineral rnining through

direct measurements made on the formation in the region where the cutting is being

performed. Inertial reference systems, attitudinal reference systems or guidance

systems

are not required for geosteering. The steering is accomplished using rock detectors

that follow die mineral formation.

[0068] In conventional systems, the vertical movements of the cutter are

controlled to be in conformance to a complex profile of the movements and/or

attitudinal parameters of the continuous miner and of the tunnel through which it is

moving. Conventional systems have been arranged primarily to track where the

miner has been, and then attempts to adjust the direction and actions, and point the

cutter based on what is learned during cutting. Geosteering, in contrast, simply

follows the mineral vein within the formation. [0069] Another preferred embodiment includes increasing the computational

capabilities within the rock detector so as to be able to perform more complex

calculations for maldng better cutting decisions. Statistical analyses are performed to

determine the probable accuracy of the decisions made by the rock detector. Data

from this expanded capability supports higher level analyses. This is depicted in FIG.

20. FIG. 20 shows the estimates of the position of the coal/rock interface at the

floor for previous cutting cycles, as well as predictions for the next cutting cycle. This

prediction is used as the "0" reference for the next measured cycle. The position of

the regular measurement of the counts is given in terms of the distance to the

predicted coal/rock interface. A typical measurement is depicted in FIG. 21. It

shows die counts measured in a time interval of 0.25 seconds as a function of depth.

(This time interval is not unique but is given as a typical example.) When these data

points are analyzed, die

predicted rock interface is at -1.67 inches, not 0.0 inches. However, that is not an

error. To illustrate the ability of this technique to pick out changes in slope, the

model formation incorporated a change in slope at 275 inches, which resulted in the

coal/rock interface being 1.5 inches lower than predicted. The measured data were

sufficient to determine this change.

[0070] This measurement will be added to the earlier measurements, the

expanded set of measurements will be fitted, and a prediction will be made for the

next cut. Also, the measurement can be used to extend the present cut to the newly

measured boundary. Immediate use within a pass requires quick decision-making

during the sweep down, since an entire sweep down can occur in just two or three seconds. The processing capability described in this invention (including PICs and a

DSP) have the speed and capability needed to determine the boundary in sufficient

time to affect the cut.

[0071] Anodier feature that should be noted is die ability of such a system to

"learn" from previously obtained data. An example of this would be the observed

count rates as a function of die distance to the interface. As long as the radiation

from the rock above and below the coal is constant, and the thickness of the coal vein

is constant, this function will remain the same. But, as these variables change, so will

die function.

[0072] Typically, these changes occurs at a much slower rate than the change in

die position of the floor. Thus, over the interval used to predict the next floor

position, the

response function can be assumed to be a constant. But, over longer periods, a

change in this function can be noted. Generally, it can be assumed to be constant

over about ten to fifteen mining passes, which should be sufficient to determine the

position of the boundary at the next cut. But, over longer intervals, such as a day of

making cuts, the coal thickness and or the level of radioactivity in the rock above and

below the coal can vary.

[0073] The change in the response pattern produces a signal that can be

distinguished from the signal produced by changes in the position of the coal/rock

interface. There are two ways in which this difference can be observed. First, the

ratio of the count rates in various energy regions changes with die distance to the boundary. An increase in the level of radioactivity will have minimal effect on this

ratio. Second, there is a unique signature when the miner breaks through the

coal/rock interface and start mining into the rock. This signature will be considered

in some detail in d e next example.

[0074] When a change in die thickness of the coal, or the level of radioactivity in

d e formation above or below d e coal crosses a tiireshold of significance, the system

is capable of performing two actions. First, it can alert die person supervising the

niining activities of die change in the conditions. This is done through the use of the

control and display panel. This affords him the opportunity to manually change the

actions of the miner. Second, it can alter the pattern it uses to determine the interface

to reflect die new conditions.

[0075] Another preferred embodiment involves a system with two detectors: one

for die roof and one for the floor. An example is pictured in Fig. 1. In this example,

the roof rock is five times as hot as the floor rock. Examples of the relative signals for

die roof and the floor are shown in Fig. 22, which gives die count rate as a function

of the distance from the miner to the floor.

[0076] The response of the floor detector is much flatter than the response of the

roof detector, as well as much flatter than the floor detector response in the prior

example. This is a result of the heightened background cause by the roof being five

times as radioactive as the floor. [0077] Even with shielding, the floor detector still has some sensitivity to the

radiation from the roof. When, as in the prior example, the roof radiation is

comparable to the floor radiation, die effects of this sensitivity are relatively small.

But, when the roof is five times as hot as the floor, the effects become noticeable.

[0078] Note that die background radiation level from the roof is not a constant.

As the process of mining down towards die floor rock begins, the boom containing

die cutter and die armored rock detectors is typically level or tilted slightly upwards.

As the mining progresses, it tilts down towards the floor. With this motion, there is

maximum sensitivity to the roof radiation at the start of die process, and a reduction

in sensitivity as die miner tilts toward die floor. This results in a decrease in the

count rates due to

the roof radiation, which partially offsets the increase in the count rate that result

from the removal of coal from the floor and the flattened response seen in Figs. 22-

23.

[0079] This reduction in signal combined with an increase in the statistical

uncertainty due to the higher background from the roof results in significandy

greater uncertainty in determining the floor coal/rock interface from measurements

made while cutting coal than from estabfishing the roof coal/rock interface from

measurements made while cutting coal. Given this difference, one might think that

the floor detector will not add to the accuracy of the measurement.

[0080] There is, however, a very significant bed boundary signal that is unique to

the floor detector. It is a significant rise in the count rate as the miner reaches the floor. An example of this is shown in FIG. 23, which shows a step function change in

count rate at the coal/rock interface.

[0081] The reason for this change is tiiat, when the miner reaches the boundary, it

starts mining the radioactive rock instead of die coal. The surface of the coal pile is

quickly covered with shale. Since the coal pile is very close to the detector, the

higher radiation from this region results in a significant increase in the detector count

rate.

[0082] A similar signal is not seen at the roof. When the miner breaks through the

coal/rock interface at the roof, the shale falls to the floor. The roof armored rock

detector is shielded from the floor signal, so it does not show a marked increase right

at die boundary.

[0083] Armored rock detectors may be used for geosteering at the floor and at the

roof of a mining operation. FIG. 1 shows a continuous miner 10 that has been

configured with two armored rock detectors 20, 120. The primary function of these

detectors 20, 120 is to determine when the cutter picks 14 are approaching the coal-

rock interface 15, 16, to slow the movement of the boom 11, and to stop the

movement of the boom 11 whenever all of the coal 18 has been removed.

[0084] Each of these detectors 20, 120 has been strategically positioned to allow

it to receive gamma radiation from the rocks at the coal-rock interface 15, 16 in front

of the advancing cutter picks 14, as well as direcdy behind the cutters. To reach the rock detectors 20, 120, some of the radiation 28 passes between the picks 14. In the

event that the cutter picks 14 overshoot the interface 15 at the floor, and enter the

floor rock 26, the picks will throw rock on top of the coal pile 21 behind the cutter.

This sudden exposure of the rock surface and the loose rock added on top of the coal

pile 21 behind die cutter gives an immediate rise in gamma counts, an indication that

die cutter 12 has gone too far and die shearing is stopped before a significant amount

of rock 26 is removed. By making the rock detectors 20, 120 faster and more

accurate, the cutter 12 can be stopped before cutting into the coal-rock interface 15.

A variety of techniques are employed to increase die accuracy and speed of the

detectors 20, 120.

[0085] Many functional elements are required to make effective the rock detectors

20, 120. As can be seen in FIGS. 1 and 4, the rock detectors 20, 120 are protected

by armor 70 that surrounds, shields, and supports them at a critical location near the

cutter picks 14. A challenge in designing the armored rock detector 20, 120 is the

simultaneous provision of effective protection from the harsh environment and of an

unobstructed path for the gamma rays 28 to enter the scintillation element 50 with as

Htde attenuation as possible. Windows are provided in each portion of the structure

to prevent obstruction of the gamma rays 28 trying to enter the scintillation element

50. FIGS. 6-8, which are cross-sectional views of FIG. 5, show the various elements

that protect the scintillation element 50, the electronics 57 and other sensors. These

multiple levels of protection are described in detail below. [0086] Gamma rays 28 entering the armored rock detector 20, 120, shown in

FIG. 4, pass through a non-metalHc window 71, preferably formed of poly-ether,

ether, ketone (PEEK), in order to reach the scintillation element 50 within the rock

detector 20, 120. Other windows 65 have been cut into a rigid dynamic enclosure

80 which surrounds die scintillation element 50. A gap 65' is provided in a flexible

support sleeve 68 within the rigid dynamic enclosure 80 and a gap 64 is provided in

die flexible support sleeve 61 surrounding the scintillation element 50, inside the

scintillation shield 63. The gaps 65', 64 are aHgned to minimize the amount of metal

in the path of the

gamma rays 28, except for d e scintillation shield 63, which has been made as thin as

possible.

[0087] Next, with reference to FIG. 5, will be described the general functioning

of the detectors 20, 120. A scintillation element 50 responds to gamma rays 28 that

have been emitted from the rock 26 above or below the unmined coal 18. The

response is to produce a tiny pulse of Hght that travels to a window 52 at the window

end of the scintillation element 50 or is reflected into the window 52 by a reflector

67 (FIG. 6) that is wrapped around the scintiHation element 50. The Hght pulse

travels through an optical coupler 51, through the window 52, and through a second

optical coupler 53 into the faceplate of a Hght detecting element, shown here as a

photo-multipfier tube 55. An electrical pulse is generated by the photo-multipHer

tube 55 and sent to electronics element 57. The photo-multipfier tube 55, the

electronics element 57 and an accelerometer 60 are located in an assembly called a photo-metric module 58. Since components within the photo-metric module 58

utilize electricity, it is necessary that it be enclosed in an explosion-proof housing 59

to avoid accidental ignition of gas or dust that may be in the vicinity of the

continuous miner 10 on which d e armored rock detector 20, 120 is instaHed. In

addition to satisfying the explosion-proof safety requirements of the Mine Safety and

Health Administration, d e explosion-proof housing 59 also serves as an effective

barrier that protects die electrical elements 56, 57 and die accelerometer 60 from the

strong electromagnetic fields generated by the heavy electrical equipment on the

miner 10.

[0088] Better details of the protective elements are shown in FIGS. 6-8. The first

view in FIG. 6 shows a flexible support sleeve 61 surrounding the scintiUation

element 50, which protects it from high levels of lower frequency vibrations. The

tight fitting sleeve 61 firmly and uniformly supports the fragile scintillation element

50 at flat portions 63 of the sleeve 61 and provides a high resonant frequency so that

it will not resonate with lower frequency vibrations that pass through the outer

support system. The outer support system consists of the flexible support sleeve 68

inside of the rigid enclosure 80 and a rigid elastomeric shock absorbing sheath 81

which surrounds die enclosure 80. A typical size scintillation element 50 for this

appHcation is 1.4 inches in diameter by 10 inches in length, but may be as large as 2

inches in diameter. The resonant frequency of these outer support elements 68, 81,

80 protect against shock and isolate the scintillation element 50 from high

frequencies. [0089] FIG. 7 iHustrates a view of the photo-multipfier tube 55, which is inside

the photo-metric module 58, which in turn is within the explosion-proof housing 59.

A flexible support sleeve 75 surrounds the photo-multipfier tube 55, another flexible

sleeve 69 surrounds the photo-metric module 58, and die flexible sleeve 68 extends

d e full length of the rigid dynamic enclosure 80 over the explosion-proof housing

59. Likewise, the elastomeric shock-absorbing sheath 81 fuUy covers the entire rigid

dynamic enclosure 80. It should be noted tiiat this sheath 81 serves other useful

purposes. It provides good mechanical compfiance witii the armor 70. This is

particularly important

during instaUation in which dust and particles will be present. Another purpose of

die sheatii 81 is to prevent water or dust from entering dirough the window in the

enclosure 80.

[0090] FIG. 8 iHustrates the accelerometer module 60, which is afforded the same

critical protection from the harsh environment as the photo-multipfier tube 55.

InstaUation of the rock detector 20, 120 into the armor 70 includes rotating the

detector so that an axis of sensitivity 83 of the accelerometer 60 is approximately

paraUel with die floor plane of the miner 10, defined by d e surface upon which the

miner 10 crawler travels. This aHgnment does not have to be exact since the primary

objective is to provide incremental motion inforrnation, not absolute orientation or

position. It is the use of this incremental motion information by the rock detector

20, 120 that assists the geosteering concept to be effective by enabling faster and

more accurate cutting decisions required to stay within the coal vein. This is better

explained below. [0091] If the advance of the cutter picks 14, due to the lowering or raising of the

boom 11 to which the rotating cutter 12 is attached, is at a constant rate, then the

gamma data could be correlated with time. However, diere are many operational

reasons why the rate of movement of the boom 11 is not constant. Another choice

available is to correlate the gamma data with d e actual incremental movement of the

boom, which can be measured. Movement of the boom directiy relates to the

movement of the cutter, though tiiere are potential errors.

[0092] Gamma counts correlated to time might appear as curve 1 in FIG. 9a.

Notice that there is considerable scatter in the data in addition to some erratic trends

within the data set. The general scatter is a result of gamma radiation being statistical

in nature. There is no way to predict when a piece of die formation wiU issue the

next gamma ray. Averaging the data over time is essential. Since the rate of the

gamma counts is increasing as the rock interface is approached, in addition to the

statistical variations, it is useful to use a weU-known method for making predictions

based on weU behaved data that has a statistical component; that is, to correlate the

data to an independent variable that is controUable. The change in the count rate is a

result of the cutter removing the coal. A chaUenge, and an objective of this

invention, is to provide a means to derive an accurate measurement of cutter motion,

over short increments of time. Motion is the cause of die change in count rates as

cutting continues, and precise increments of motion can be used to correlate the

count rates for curve-fitting purposes. [0093] When correlated with actual incremental movements of the cutter (or the

boom), the same data may produce a more useful curve such as curve 2 in FIG. 9b.

The value of die better behaved curve 2 is that it can be used to predict the point at

which a value wiU be reached that corresponds to die value expected at the point

when the cutter picks 14 reach the coal-rock 15 interface. By plotting multiple

curves for each energy range and by applying algorithms to these curves, more

accurate predictions are possible, even for variable operating conditions.

[0094] A logic element 57 is functionaUy depicted in FIG. 10. As explained

earfier, this critical element is weU protected from the harsh environment by an

explosion-proof housing 59 that is dynamicaUy isolated by a support system. The

metafile housing 59 also protects against electromagnetic interference with the miner

electrical systems 55, 56, 57. The logic element 57 receives electrical pulses from an

ampfifϊer 91 after being generated by the photo-multipfier tube 55. The electrical

pulses from the photo-multipfier tube 55 may have amplitudes as low as 30 mN, and

the duration may be as smaU as a few hundred nanoseconds. They are routed

through the buffer 90, which isolates the input signal from the logic element 57

circuitry to prevent degradation to the signal. The ampfifier 91 increases the

amplitude and inverts the signal from a negative aperiodic pulse to a positive

aperiodic pulse. The ampfifier gain may be on the order of twenty. The actual gain

value is dependent upon the voltage range of the input signal, the range and

resolution of an analog- to-digital converter 92, the supply voltages, and the slew rate

of the ampfifier 91. The amplified signal may serve as a trigger signal to inform the microcontroUer 93 that a new pulse is ready for processing. Since the pulse is

aperiodic and short in duration, it is necessary to sample and hold the peak ampHtude

of die amplified pulse until the microcontrofier 93 can act on the trigger signal and

read die ampfitude via the analog-to-digital converter 92.

[0095] Once the amplified pulse amplitude has been sampled, the microcontroller

93 resets die sample-and-hold peak detector of die sampled pulse, while maintaining

running count and/or average count over a given period of time. The pulse counts

may be grouped into two or more energy ranges to form an energy spectrum. In

particular, the counts in each energy spectrum, for each segment of time, such as

0.10 seconds, are correlated with the motion of the cutter since the last time

segment. Discrimination and pattern recognition techniques are then used to

characterize and predict the thickness of the coal, and thus the distance from the

picks 14 to the rock 26. By applying various algorithms to the relationships that

correlate counts with measured incremental movement within the energy spectrums

and d e gross counts, higher accuracy can be achieved under variable operating

conditions.

[0096] A power supply 56 provides high voltage to the photo-multipfier tube 55.

Noise is easily introduced into high impedance circuitry such as is required for the

high voltage photo-multipfier tube 55. Having the power supply 56 inside the

explosion- proof housing 59 protects the circuitry from electricafiy induced noise

from die large motors and other machinery on the miner 10. The housing 59 also protects against this high voltage accidentafiy igniting gas and/or coal dust in the

vicinity of the miner 10. Provisions are made for the microcontroller 93 to control

the voltage from the power supply 56 to the photo-multipfier tube 55 to control its

gain.

[0097] Provisions are made in the logic element 57 to continuously communicate

witii a miner control system 100 or a control and display panel 130 (FIG. 13). Most

of die information is transferred in a serial data stream to minimize the number of

wires. The protocol for the data stream can be changed by selection of components

and

programming to be RS-232, RS-485, IEEE 1394 or other serial communication

standards as may be available. Decisions to stop or pause die cutter 12 are included

in die data stream, though a separate wire 204 and 205, respectively (FIG. 13). The

data stream includes a time stamp, gross counts per time increment, a running

average of the counts over a periods of time such as 0.5 seconds and two seconds,

motion per time increment, and a data scatter/accuracy probabifity coefficient.

Functional, logical, and manual override capability at the control and display panel

130 or in d e miner control center 100 can be provided as desired. The control and

display panel 130 may also be used to track the stop positions of the cutter 12 at the

floor and the roof to produce a profile of the tunnel being produced by the miner for

historical purposes.

[0098] If the cutter 12 overshoots the interface 15 and actuaUy enters the rock 26,

it is important that die cutting be stopped immediately. This is accompfished by keeping a rurining count over a period of time between 2.0 seconds and 4.0 seconds.

A sudden increase in gross counts above the previous running average produces a

stop signal along the stop wire 204. OccasionaUy, diere may be dislocated

radioactive materials inside the coal vein 24. If tins happens and the cutter 12 is

stopped too early, die operator can override by releasing a shear control switch (not

shown) on the miner 10 controls and immediately turn it on again. If precise cutter

motion information is avafiable so that die logic can determine that the stop decision

is not reasonable, it can issue a decision to slow die cutting.

[0099] One benefit of introducing precision geosteering technology into coal

mining is that doing so lays the groundwork for an almost boundless future growth

of software techniques, algorithms, and generaUy smarter controls for use on mineral

mining equipment. Given that the operator is so intimately connected with the

minute-by-minute operation of a continuous miner, the need and opportunity for

continual enhancements in coal mining may be greater in some respects than for oil

weU drilling.

[0100] In order to aUow for growth in computational capability, a more powerful

processor, such as a digital signal processor 104 (FIGS. 11-12) can be used. A

greater number of algorithms may be stored and executed with greater speed. By

adding larger program and data memory in the ROM 110 and RAM 108,

respectively, the digital signal processor 104 can execute multiple algorithms in

paraUel to calculate coal thickness and do so at greatiy increased speed than the microcontroUer 93 alone. If the accuracy coefficient indicates that the data is

inconclusive, the processor can caU up other algorithms and take other actions before

making a final decision. Digital signal processors, currendy available, require a larger

footprint than the microcontroUer 93. As such, only rock detectors having

scintiUation elements that are 1.75 inches in diameter or greater will have sufficient

space in die explosion-proof housing. TypicaUy, a digital signal processor using

current technology can perform 80 million instructions per second (MIPS) or more.

The microcontroUer 93 is generaUy limited by current

technology to 10 MIPS or less and is further limited by its inabifity to access large

amounts of ROM or RAM without additional circuitry.

[0101] The armored rock detectors 20, 120 can be accommodated electronicaUy

and logicaUy by connecting the logic element 57 of the first detector 120 to the

digital signal processor 104 in the second rock detector 20. Electrical junctions

between the two detectors 20, 120 are accompfished in a smaU, standard explosion-

proof junction box 211.

[0102] Use of a rock detector 120 at the roof not only afiows faster, more

accurate cutting decisions at the roof but the information from the roof detector 120

can be used to support a higher level of logical decision-making. For example, it is

known that the thickness of the coal seam varies more slowly than the elevation of

the floor or roof. Therefore, if anomalies exist such that d e accuracy probability

coefficient produced by the floor rock detector 20 is unsatisfactory, reflecting a high level of scatter in the data, the decision on that cut can be based on the last cut at the

roofless the thickness of the coal on the last cut. Or, if the logic element 57 cross¬

checks a decision and determines that tiie decision is not consistent with other known

data from die other detector, die logic element 57 can elect to slow down the cut in

order to obtain more accuracy or can alert the operator to die condition, giving the

operator the opportunity to override. Fortunately, diese situations are anomalies and

do not aU have to be solved in an ideal manner, but provide opportunities to make

future improvements to further the

efficiency of the operation. As the miners become increasingly more automated,

having a variety of software routines diat can be caUed into play wiU be an asset.

[0103] Actual incremental movements of die cutter 12 toward or away from the

rock interfaces 15, 16 can be determined in various ways. A vertical displacement

sensor may be used to determine actual incremental vertical movements of the rock

detector, by measuring the change in distance of the cutter 12 or the boom 11 from

a known position on the floor, roof or waU. Such a sensor might be a mechanical

displacement, optical, acoustic or other gauge. The rock detector performance and

the geosteering control system strategy are not dependent upon the source of the

measurements of the incremental movement.

[0104] Some of the operational aspects of preferred embodiments will now be

discussed in more detaU. An object is to utilize an accelerometer design that has

been proven over many years in rugged and demanding environments, such as directional chilling for ofi. The accelerometer 60, shown in FIG. 8, is oriented so

that whenever the tips of the cutter picks 14 are at a nominal floor position, on a

level floor, the direction of sensitivity of the accelerometer would be paraUel to the

floor, in the same direction as the forward advance of die continuous miner. In that

configuration, die accelerometer 60 would ideaUy indicate a zero reading. However,

if d e boom 11 is raised or lowered, a component of gravity is measured against the

axis of sensitivity 83 of the accelerometer 60. The measurement of the change in

angle can be made very precisely by tiiis method.

[0105] In actual operation, the floor wiU generaUy not be level and so the nominal

zero position of the accelerometer 60 would not produce a zero reading. This is not

a problem since the objective is to measure the change in position, or relative

movement and not the absolute position. Changes in gamma measurements relative

to actual incremental changes in position wiU produce a curve similar to curve 2 in

FIG. 9b.

[0106] There are operational considerations that must be addressed in order to

achieve a high degree of precision from the accelerometer 60. One is vibration. As

the cutter 12 rotates to cut the coal, vibrations are induced into the boom 11.

Vibrations in the vertical direction, generaUy perpendicular to the axis of sensitivity

83 of the accelerometer 60, have only a secondary, smaU effect on the accuracy of the

accelerometer 60. However, vibrations and movements back and forth are also

experienced and such movements are interpreted by the accelerometer 60 as rotation of the boom 11 and vertical movement of the cutter 12. Another effect of the

operation on the accuracy of the accelerometer 60 is that of the vertical movement of

d e front of the miner 10 as a result of the force being appfied to the cutter 12 by the

hydraufic cylinders (not shown) connecting the boom 11 to the body of the miner

10. If left unadjusted, the data would be in error by die amount of vertical

movement of the miner 10 that occurs during the shearing stroke. Both of these

sources of error are addressed below.

[0107] Referring back to FIG. 8, three elements serve to isolate the accelerometer

60 from damaging shock and high frequency vibrations resulting from the mirier 10

mechanisms and from impacts by materials being thrown against the armored rock

detector 20, 120 by the rotating cutter picks 14. These three elements are (1)

elastomeric ridges 82 on the enclosure 81, (2) the flexible support sleeve 68

positioned between the dynamic housing 80 and the explosion-proof housing 59,

and (3) the flexible support sleeve 61 between the accelerometer module 60 and the

explosion-proof housing 59. Lower frequencies will pass through aU three levels of

isolation. The effects of the lower frequencies on die data are minimized by software

techniques. However, the operational methodology that wiU now be described

greatiy reduces these effects before they enter into the data stream.

[0108] There are many situations faced during the operation of continuous miners

10 so that they cannot aU be discussed. Fortunately, an operator can be quickly

trained on how to utilize the geosteering system to simplify his job and to be more effective in most of the situations that he encounters. A typical example of the

procedure for cutting at the coal face 17 (FIG. 1) is to first sump the cutter 12 into

die face near the roof and then to raise the cutter picks 14 to die coal-rock interface

16. Next, the boom 11 is lowered so that the cutter 12 shears down toward the rock

interface 15 at the floor. In most coal formations, this shearing process can be

performed faster than the gathering arms and conveyor on die continuous miner 10

can carry away die coal. It is not

unusual for the operator to temporarUy stop or pause the shearing for two or three

seconds to aUow the coal handling equipment to carry away some coal before cutting

the rest of the way to the floor. This temporary pause, whether performed manuaUy

by the operator or automaticaUy by the geosteering system, is an opportunity to

establish a precise reference position for starting the data correlation process.

[0109] The logic element 57 (FIGS. 10-12) issues a pause command when the

boom 11 reaches a desired angular position, even if the operator does not do so. In

either case, the logic element 57 recognizes that the boom 11 has stopped moving

and quickly determines the precise angle of the accelerometer 60, and thus the rock

detectors 20, 120. It is important to note that it is a simple arithmetic calculation to

convert die angle measured by the accelerometer 60 to a linear distance

perpendicular to the plane of the continuous miner 10 by use of the formula L x sin

(tiieta) where L is the length of the boom 11 and theta is die angle measured by the

accelerometer 60 in the rock detector 20, 120. Further, deterrnining the "height" of

the cutter 12 relative to the plane on which the crawler is theoreticaUy advancing is

not of any significant value to the objective of correlating gamma data being taken by the rock detector 20, 120. The primary objective is to correlate the gamma counts

with precise motion that corresponds to the changes in gamma counts, not

necessarily the measure of absolute "height" above some reference. Therefore, the

incremental change in the angle of the rock detector, which does direcdy relate to the

"height" of the rock detector 20, 120, may be chosen as the parameter which is used

to correlate changes in gamma measurements to produce

die curve 2 shown in FIG. 9b. It is the incremental change in gamma counts versus

an incremental change in angle that is analyzed to predict die intercept of the cutter

picks 14 with the coal-rock interface 15, 16, through curve fitting techniques.

[0110] After the first pause in die shear down stroke is achieved at a selected angle

which might correspond to the cutter 12 being in the range of 6-10 inches above the

nominal zero position, a precise measurement of the angle is made. If the operator

feels that the pause is being commanded too early or too late, he can select a different

setting. Provisions are made for the operator to be able to adjust the duration of

this first pause if desired, and the operator also can override simply by resuming the

down shear. As the selected angle is achieved and motion is stopped, the logic

element 57 acquires gamma counts at intervals of approximately 0.1 seconds. While

loose coal, such as the coal found in the coal pile 21, is fairly transparent to radiation,

it does affect gamma radiation readings. Thus, it may be necessary to pause the sump

midway dirough the sump to enable the rotating picks to clear away the coal.

[0111] Upon die initiation of the pause command, a solenoid that controls the

hydraulic system on the miner 10 closes to stop fluid flow. However, if the operator has driven the cutter 12 hard into the coal, there wiU be some pre-load taken by the

structure and the hydraulics so that the shear down wiU not stop instandy. In some

cases, the front of the miner 10 may be raised a few inches due to the high force

being applied to die cutter 12 so that die cutter is physicaUy higher than the angle

indicated by the accelerometer 60. Fortunately, this tends to be a self-correcting

problem because

die cutter 12 wUl continue to lower, after hydraulic flow has stopped, until the pre¬

load has been relieved and die front of the miner 10 has returned to its unloaded

state.

[0112] Once die cutter 12 has essentiaUy stopped moving down, the logic

element 57 wUl record the angle and begin accumulating gamma counts. The

difference between this angle and die angle at which the last cutting sequence was

stopped is determined and the number and duration of the expected shearing pulses

is calculated. The actual number of pauses wiU depend on where the interface is

actually located. The rock detector will calculate die approximate number of

shearing pulses, based on the position of the cutter 12 relative to the previous shear

down. Pulses of approximately 0.25 second duration will result in the cutter 12

being lowered approximately 1.5 inches. At the end of the pulse, the cutter 12 wiU

not yet have traveled the fuU 1.5 inches but wUl continue for a short time. After the

pulse stops and the solenoid controlling the hydraufics closes, the cutter 12 will

complete its travel and stop. Some vibration wiU continue due to rotation of the

drum 12 and incidental contact with the formation. As soon as the accelerometer 60

determines that vertical movement has essentiaUy stopped, a precise determination of the movement since the last stop is calculated. It is this precise incremental

movement against which the gamma counts are correlated.

[0113] As die cutter 12 nears die angle at which die shearing command was

issued on the last shearing stroke, die duration of die pulses may be reduced,

depending upon die accuracy coefficient that is being continuously calculated. Data

coUected between

diese pause points wiU be assigned a position value between the position

corresponding to die pause points. Through this metiiodology, very little time wiU

be consumed in die pauses. The operator camiot actuaUy see a stop in motion of the

boom. Since the cutter 12 can usuaUy extract coal faster tiian the miner 10 can carry

it away, the addition of pauses does not slow die niining process. The cutter wiU

continue to remove coal as fast as the rest of the system can remove and transport it.

Instead, the effect is to increase speed because only coal is being mined. By not

mining rock, room is made avafiable on the conveyor and in shuttie cars for more

coal. Total coal production is increased while the mining of rock is reduced.

[0114] As data is accumulated, the logic element 57 develops a curve and begins

to make a prediction as to the location of the coal-rock interface 15, 16. Upon

reaching the angle associated with the location of the coal- rock interface 15, 16, the

logic element 57 wiU issue a stop command and signal die operator that the shearing

stroke has been concluded. In a more automated arrangement, such as for high-waU

mining, this stop signal can, instead, be sent to the automated control system. [0115] The rotating drum 12 that supports the cutter picks 14 on the front of a

continuous miner, is supported on a boom 11 that moves up and down in order to

force the picks 14 into the coal being cut. During the shearing stroke, the miner 10

frame is not moving forward. By precisely measuring die rotation of the boom

relative to the stationary miner 10, tiiis angular measurement can be used to correlate

gamma counts to the incremental motion. A source of error is that the miner 10

frame itself may move

away from the floor due to the high forces exerted by die continuous miner as it

forces the cutter 12 down into the coal. As the miner 10 moves, it changes the

vertical position of the pivot point for the boom 11. When the control process

described above is used, diis motion has no effect on the results. If the coal is very

hard and the cutting is very fast, it may be desirable to compensate for this motion in

other ways as described below.

[0116] Although the miner control center 100 can be configured to respond to

the cutting decisions from the rock detector 20, 120, the addition of the control and

display panel 130 is desirable (S. 13, 15, 16). If a control and display panel 130 is

provided for the rock detector, a smaU acceleration micro-chip 131 may be included

to automaticaUy correct for errors that result from vertical movement of a pivot pin

22 (FIG. 1) about which the cutter boom 11 rotates. The smaU solid-state

accelerometer 131 is mounted on a smaU circuit board tiiat measures the tilt of the

miner 10. By measuring the amount that the miner 10 is tilted, and transmitting this

information to the rock detector 20, 120, the rock detector 20, 120 wiU adjust the

data to remove the error. [0117] First, the angular measurements by the accelerometer in the rock detector

are converted to linear height numbers by the simple calculation of L x sin(theta),

where L is the lengtii of the boom and tiieta is the angle measured by the

accelerometer 60 in the armored rock detector 20. Then, die vertical movement of

the pivot pin 22 on the miner frame is calculated by the same equation, except that

d e length is the distance from the pivot pin 22 to d e point on the crawler about

which the frame pivots and the

angle is the tilt of the miner frame as measured by the accelerometer 131 in the

control and display panel 130. This error number is sent to the rock detector 20,

120 where it is subtracted from die height calculated using the accelerometer angle

of the rock detector 20, 120 and boom 11. Making these adjustments permits the

incremental movements to be accurately measured even when the pivot pin 22 is

moving.

[0118] The control and display panel 130 may be configured as needed for the

type of machine and the specific operational requirements for a specific niine. It may

include a liquid crystal display (LCD), light emitting diodes (LED), and/or

incandescent bulbs. TypicaUy an LCD would display system parameters, such as

gamma counts, boom movements, coal thickness calculations and system status

information. LEDs would provide visual indication of the miner status such as

calibrating, cutting, start, pause, stop and rock contact warning. Furthermore, the

operator can change system settings and access data and parameters as needed. [0119] Due to the electrical components in the control and display panel 130, it

must be enclosed in an explosion-proof housing (not shown). Since operational

needs and preferences are subject to change, particularly in a rapidly advancing

technology such as this, there is a need for the control and display panel 130 to be

re-configurable in various ways without having to re-certify the design for Mine

Safety and Health Administration requirements. Frequent re-certification can be

avoided by efiminating penetrations through die pressure proof window or housing,

for switches or controls. Penetrations, other than for standard cable entries, can be

efiminated by use of

electromagnetic switches that are activated by a magnetic wand that that will work

through a certified pressure proof window. Whenever the magnetic wand is moved

on the outside surface of the window, near> a switch that is located on the inside of

die window, the switch wiU trip. Switches may be momentary or may toggle on/off.

Easier to use configurations include incorporation of the wand into a compound

lever so that it can be simply moved to operate a switch and then be returned to a

stowed location. The control and display panel may also be operated remotely by an

RF fink as is routine for the miner control center 100.

[0120] The various embodiments described above produce a faster, more accurate

system, that is simpler and less costiy that conventional systems previously used.

However, other important improvements can be made as described below.

SpecificaUy, a separate cutter motion indicator can be added to the system to provide

very accurate, almost instantaneous measurements of cutter movements. [0121] Every mining company is constantiy looking for ways to advance the

miners at a faster rate in order to mine more coal. Great improvements have, in fact,

been made during recent years, thus helping to keep tiie cost of mining coal in check.

This has contributed somewhat to die problem of mining more rock. As the miner is

moved more quickly, cutting errors are more difficult to avoid by the operator. With

experience, the operators do improve. But, as new operators must be added over

time, loss of production and undesirable mining of rock, a real problem at aU times, is

made worse witii inexperienced operators. Therefore, a chaUenge is to make cutting

decisions

more accurate and quicker. As die miner 10 is then able to advance faster, more

improvements are, again, needed. Some conventional systems employ inclinometers

that respond too slowly to aUow the accuracy and speed that is desired. Even the

very precise accelerometers described in the earlier embodiments, though significant

improvements, may place some limits on speed in some conditions. As miners

generaUy become more automated, speed and robust control become more

important requirements. A separate cutter motion indicator 300 (FIGS. 16a, 16b,

17) can be added to the system to provide almost instantaneous measurements of

cutter movements. The indicator 300 is positioned at the pivot of the boom.

[0122] The cutter motion indicator 300 can be configured in different ways,

depending upon the configuration of the mining equipment and the operational

requirements. When using a cutter motion indicator 300, an accelerometer 60 is

not required inside the rock detector 60. The space normaUy occupied by the

accelerometer 60 may be used for other purposes. [0123] An explosion proof housing 302 is used to contain an optical encoder 303

and electronics 320 to ensure that those components wiU not be able to ignite gas or

dust in die vicinity of die miner 10. Thick steel walls 319 of the enclosure 302 are

capable of withstanding considerable impact without losing pressure integrity. An O-

ring seal (not shown) provides the primary seal between the fid 304 and the housing

walls 319. Multiple seals 311, 312, 313, 317 ensure pressure integrity around a shaft

321 diat transmits the rotation of the boom 11 to the optical encoder 303 inside the

enclosure 300. Dual seals 312 preferably are high pressure seals made of PEEK. In

addition, a bushing 317 around the shaft 321 is provided as added protection. The

dimensions of the shaft 321 and die bushing 317 are controlled such that the

maximum clearance is 0.002 inches. This small gap ensures that even if gas is able to

pass around die non-metallic seals 312, the amount of escaping gas wiU be so smaU

so that it wiU not be hot enough upon exiting the gap to ignite any gas or dust that

might be around the enclosure 302.

[0124] Rotation of the boom 11 is transferred into rotation of the shaft 321

which in turn drives the optical encoder 303. The optical encoder 303 indicates

rotation of the shaft 321 by emitting pulses, a single pulse representing a specific

amount of rotation. Provision is made to indicate the direction of rotation as weU.

Optical encoders, such as the optical encoder 303, are commerciaUy available that are

very precise, accurately indicating rotation of smaU fractions of a degree. Pulses from

the optical encoder 303 representing the amount of rotation are received by a

counter and adder assembly 320. The number of pulses are added and subtracted as

the boom 11 rotates. Incremental movement of the cutter 12 toward the rock interface 15, 16 is calculated by determining the product of the length of the boom

11 and the arc-sine of the angle rotated.

[0125] Though very precise, die optical encoder 303 does not indicate the actual

distance of the cutter 12 above the rock interface 15, only the amount of rotation per

increment of time, typicaUy 0.10 seconds. It should be remembered that it is the

actual distance of die cutter 12 to die rock, or equivalendy, the thickness of the coal

tiiat is not

known. If the distance to the rock could be known witii sufficient accuracy, without

the use of the armored gamma detector 20, 120, die detector would not be needed.

Therefore, die information tiiat can be known to high precision through the use of

the cutter motion indicator 300 is the incremental changes in position as determined

by the optical encoder 303. With this precise data on incremental changes, the

armored gamma detector 20, 120 determines the distance to the rock 15, 16

through the interpretation of the gamma radiation 28 as it relates to these

incremental changes in position.

[0126] Motion of the miner 10 frame during the cutting process, as explained

earlier, is a source of error in the cutter motion data being provided to the armored

rock detector 20, 120 by the cutter motion indicator 300. Accelerometers are

incorporated inside cutter tools for drilling oil weUs for the purpose of determining

angle relative to gravity to a high degree of accuracy. The accelerometer 60 is such a

device. The accelerometer 60 determines if its angle relative to gravity changes,

which is a measurement of any change of the angle of the miner 10 frame relative to the gravity vector. It is also simple to then calculate the instantaneous change in

height of the boom pivot pin 22 that results from this rotation. These calculations

are performed by the counter and adder assembly 320.

[0127] Once precise cutter motion data is available, along with cutting control

decisions from the armored rock detector, additional information can be derived.

TypicaUy, this would be accomplished in die control and display panel 130 or within

control system provided by the continuous miner. For example, the cutter 12

motion for each cut, including die point at which die armored rock detector issued a

stop command, d e actual position that the stop occurred, any indications of contact

with rock, and otiier information is readily available for historical storage and/or

further evaluation or use. Since the stop position at the floor and the roof are known

each cut, relative to the previous cut, tracking these stop points in the control and

display panel would provide a contour of the floor and the roof. Decisions can be

made in the control and display panel 130 to override die rock detector 20, 120 or

decisions can be made independent of the rock detector under certain special

conditions. For example, suppose that a cut is stopped at a particular position.

Then, suppose on the next cut the detector gives a false indication due to an anomaly

in the coal vein, and issues a command to stop the cutter six inches above the

position of the previous cut. Logic can be included in the control and display panel

130 tiiat would override or ignore die armored detector 20 decision. The decision

could be made to stop the cutter 12 at the same height as the last cut, relying upon

the knowledge that the formations will not change six inches over the distance of one cut. Or, alternately, the decision could be to slow the cutter until the rock detector

20, 120 detects that the rock has been contacted, indicated in a sudden jump in gross

gamma counts.

[0128] A suitable structure must be provided for transferring the rotation of the

boom into the shaft 321 in the cutter motion indicator 300. If a continuous miner is

configured such that the pivot pin 22 rotates with die boom 11, then a connection

can

be made direcdy at the center of the pivot pin 22. However, for this configuration,

there are some mechanical chaUenges. The cutter motion indicator 300 is a precise

instrument. Its shaft 321 must be mechanically attached to die boom 11 so that any

rotation of the boom 11 is transmitted to die encoder. However, it is difficult to

locate the cutter motion indicator 300 at a precise distance from the pivot pin 22.

Further, due to the large forces endured by the miner components, some relative

linear motion between the cutter motion indicator 300 and the pivot pin 22 must be

tolerated. This has been accompfished by the use of a spline 342 (FIG. 17).

Similarly, it is not practical to provide an exact aHgnment of the cutter motion

indicator 300 and die pivot pin 22 to which it must be attached. To overcome this

obstacle, a dual universal joint 340, 341 is provided. With these joints 340, 341, 342

in the drive train assembly, linear motion perpendicular to die drive train assembly

wiU not induce forces into the drive train assembly. Similarly, smaU angular

misafignments between d e drive train assembly and the axis of the pivot pin 22

around which the boom 11 is rotating wiU not induce forces into the drive train

assembly. [0129] Addition of the dual universal joints 340, 341 and spline 342 may

introduce a possible backlash problem. Addition of an anti-backlash spring 316

efiminates backlash by removing slack in the universal joints 340, 341 and the spline

342.

[0130] There are multiple methods for obtaining angular rotation of the boom

relative to the frame. One method is to attach a shaft at d e center of the pin upon

which die boom is hinged. However, some miners are designed such the boom

bearing

rotates on the pivot pin 22 such that the pin 22 itself does not rotate. A lever (not

shown) can be attached to the boom 11 that transfers die boom rotation to a point

tiiat is along die bearing axis. Also, the pivot pin 22 on which the boom 11 hinges

usuaUy wears so that it becomes loose. The combination of the spline 342, dual

joints 340, 341, and anti-backlash spring 316 prevent these undesirable linear

movements from entering into the rotational measurement.

[0131] On many miners, the pivot pin 22 does not rotate with the boom 11, the

bearings being on the boom 11 side of the pivot pin 22. In this case, a lever must be

added to the boom 11 to transfer the boom 11 rotation to a point along the axis of

the pivot pin 22 on which it is rotated. The provisions within the drive train

assembly discussed above are effective for relieving relative linear motion and

misafignments on tiiis miner configuration as weU.

[0132] Cafibration of the optical encoder 303 may be accompfished occasionaUy if

needed. This would typicaUy be performed at die beginning of a shift and during major moves of the miner witiiin the mine. To accomplish a calibration, the

continuous miner 10 is driven up to the face of the coal at a location where the floor

is flat, not necessarfiy level, prior to start of the cutting operation. The cutter 12 is

tiien lowered to the floor.

[0133] A cafibration command is sent to the cutter motion indicator 300 from the

control and display panel 130 through wire 206. This calibration command would

also be forwarded to die armored rock detector 20, 120 so that gamma readings can

be

recorded as well. The counter and adder assembly 320 in the cutter motion indicator

300 reads the optical encoder 303 and the accelerometer 60 and accepts that reading

as the zero position. The cutter 12 then is raised to die roof and the cafibration is

repeated and tiiis reading is taken as the zero roof position. During the next cut, the

readings will be referenced to tiiis starting reading. The second cut wiU be referenced

to die first cut, etc.

[0134] The primary source of motion information is from the optical encoder

303. This encoder 303 has a disk with holes that move past a fight source as it is

turned by the boom motion through the drive train assembly described earlier. The

holes in the disk are spaced to provide a certain degree of angular resolution.

TypicaUy, the angular resolution of a commerciaUy available encoder is on the order

of 0.06°. The output signals, A and B, from the optical encoder 303 are pulses that

can be counted by the microcontroUer 93 or other logic. Furthermore, if the pulse

from A leads the pulse from B, then the rotation is clockwise. Thus, the running count of pulses is incremented by one. If the pulse from A lags the pulse from B,

then the rotation is counter-clockwise. Thus, the running count of pulses is

decremented by one. At any given time, the number of pulses counted can be

converted to an angle measurement simply by multiplying the current pulse count by

the angular resolution, thereby giving the angle of the boom 11.

[0135] To sense the tilt of the miner 10 frame, an accelerometer 60 is used inside

die cutter motion indicator 300. An accelerometer 60 can measure angle based on a

change

in orientation with respect to the gravity vector. The gravity vector is the same aU

over ti e earth; it points toward d e center of d e earth. With d e accelerometer 60

fixed to d e miner 10 frame, d e orientation of the accelerometer 60 changes as the

miner 10 tilts up or down. The output signal from the accelerometer 60 is typicaUy

an analog voltage, or current, which can be converted to voltage, that varies as the G

force varies according the resolution of the device. TypicaUy, a commerciaUy

avafiable accelerometer has a resolution of 1 micro-G. The output voltage can be

sampled by an analog-to-digital converter 92. The sampled value can be converted

to angle by referencing it to a G force of 1 and taking the arc-sine. Thus, the tilt of

the miner 10 frame is measured during the shearing stroke and the vertical

movement of the pivot is measured, subtracted from die measurement made by the

optical encoder 303, and the difference is reported to the rock detector 20.

[0136] Another preferred embodiment applies geosteering to long-waU shearing

systems. Long-waU miners have two shearing drums 412, 413, as shown in FIG. 18. When moving one direction, the cutting drum 413 is in the front and is referred to as

d e leading drum. It cuts at the coal/rock interface 16 at the roof and the second

drum 412, referred to as the trailing drum, cuts at d e floor interface 15. TypicaUy,

one operator positions himself near the front of die miner and visuaUy controls the

height of the leading drum 413 so as to remove aU die coal 18 and to remove as little

rock 26 above the coal 18 as practical. A second operator controls the vertical

position of the trailing drum 412 tiiat is located approximately 40 feet behind the

leading drum 413.

Visibility of the trailing drum 412 is usually severely limited due to the shearing

assembly being fiUed with coal. In some operations, rock may fafi from the roof,

obscuring the cutter 412. Coal and rock roU behind a cowl 404 so that the exposed

cut 415 is quickly covered in the region a few feet behind the cowl. Fortunately, the

exposed cut immediately behind and somewhat under the cowl 404 remains free

from debris which is useful.

[0137] Geosteering is accompfished for the trailing drum 412 by placing a rock

detector 401 on the back of the cowl 404 such that it can view the surface that has

just been cut by the cutter drum 412. The purpose of this rock detector 401 is to

differentiate between the condition when the cutter drum 412 is cutting into the

floor rock, typically fire clay, from the condition when picks 407 of the drum 412

(FIG. 19) are above the floor so that coal is being left unmined. The rock detector

401 also can calculate the thickness of the coal being left. In effect, this rock

detector 401 is measuring the distance that the cutter is separating from the

coal/rock interface, or the amount of divergence between them. For that reason, this detector is referred to as the divergence rock detector 401. If the cutter is

beginning to cut into the floor, indicating that the cutter 412 and the floor are

moving toward each od er, ti e detector 410 detects d e rock diat is being mined and

mixed with the coal. This detector is referred to as die convergence rock detector

410.

[0138] The cowl 404 may be located close to die cutter picks 407, as close as

diree inches. In such a circumstance, the divergence rock detector 401 may actuaUy

be

verticaUy beneath d e cutter picks 407, thereby in a position between the picks and

the coal.

[0139] As die miner moves forward, the cowl 404 drags on the newly cut surface

415, dius removing lumps of coal or rock and aU but a smaU amount of coal dust. If

the cutter 412 is cutting into the rock 26, the divergence detector 401 wiU not be

able to measure any change in gamma readings. Therefore, the detector 401 wiU

begin to raise the cutter 412 in smaU steps. For example, die rock detector 401 may

give a command each 10 seconds to raise the cutter by 0.5 inches. If the miner 10 is

moving at the rate of 30 fpm, then the cutter 412 will be raised approximately 0.1

inches for each foot of travel. Once the cutter tips 407 are raised above the

coal/rock interface 15, no rock is being mined.

[0140] If the cutter 412 rises above the rock 26, coal will be left behind,

unmined. Once the coal is approximately one inch thick, the divergence detector

401 wiU detect the layer of coal and stop raising the cutter 412. The detector wiU measure the thickness of the coal and then lower the cutter 412 by that amount.

After 10 seconds, it wiU begin to raise the cutter 412 as before, in 0.5" steps, each 10

seconds and repeat die process.

[0141] Unless a convergence rock detector 410 is being used, the divergence rock

detector 401 wifi continue to raise the drum 412 by 0.5 inches each 10 seconds.

During tiiis time, the coal/rock interface 15 may be rising either toward or dropping

away from the cutter drum 412 and movements of the miner either add or subtract

from diese relative movements. These possible relative movements must be

considered in selecting the rate at which d e divergence rock detector 401 raises the

drum 412. If the drum 412 is raised too rapidly, die cutter tips wiU quickly be

sufficiendy above the rock interface 15 so that coal is left urimined. If the drum is

raised too slowly, at a time when there is rapid convergence between the cutter 412

and the floor interface 15, the cutter 412 may dig into the rock 26 faster than it is

being raised out of the rock 26, until the rate of convergence decreases. Fortunately,

tiiis would be a rare condition, for a reasonable set of control parameters.

[0142] Floor conditions vary from mine to mine. Control parameters in the rock

detector 401 are set to best fit the range of conditions that exist in each mine. Some

floor conditions are very favorable for geosteering even though they may have

traditionally been considered to be poor floor conditions for other types of niining

systems. For example, in some mines, the coal is soft and is not bonded to the fire

clay in the floor. As a result, whenever the cutter 412 is raised out of the floor, such

that the picks 407 do not reach into the fire clay, die coal will continue to break away from the fire clay so that no coal is left unmined. This zone of cutting is caUed the

break away zone. This condition may continue even when the cutter picks 407 are

two inches or more above the fire clay, meaning that the break away zone may be as

much as two inches or more.

[0143] Geosteering can mine almost aU the coal and fittie or none of the rock

when die breakaway zone is greater than one inch. If the cutter 412 is either cutting

into die rock 26 or leaving coal unmined, there is a procedure employed by the rock

detector 401 to recognize this condition and to return the cutter 412 to cut in the

break away zone. Once in the break away zone, die accelerometer 60 inside the rock

detector 401 monitors the angle of die cowl 404 so that any vertical movements of

the cutter 412 are detected. The cowl 404 is riding on the top of the fire clay such

that the position of the cutter 412 can be controUed relative to the fire clay. The

rock detector 401 opens solenoid valves as required to raise or lower the cutter 412

in order to keep the tips of the picks 407 inside the break away zone. For each

movement of the cutter 412, the rock detector 401 pulses the solenoids for a length

of time that is calculated by the rock detector depending upon the response rate of

the hydraufic system.

[0144] Unusual situations may arise from time to time. The geosteering must be

robust to respond to these situations or, at least, quickly recover from any disruptions

in the normal process. For example, the cutter 412 might move up more than

commanded so that the soft coal is no longer being broken away from the fire clay, or the coal might have hard spots so that it remains bonded to the fire clay even

though it is being cut very tiiin. In these cases, the divergence detector 401 wifi

recognize a sudden change in gamma readings and respond by lowering the cutter by

tiie thickness of the coal diat it reads. Also, the accelerometer 60 wiU respond by

reporting a change in the height of

the cowl as it climbs upon die coal that is beginning to be left. This event can also

be included in the logic.

[0145] The more difficult condition to protect against is for the cutter 412 to

begin entering die rock 26 because the divergence detector 401 does see a change in

gamma readings because it is already looking at fire clay with only a little dust on top.

This is solved by performing repetitive cycling once the picks 407 have entered the

breakaway zone. First, the cutter 412 is raised 0.5 inches. The accelerometer 60

immediately registers the cutter 412 being raised. After approximately six seconds

the cowl 404 is seen, by the accelerometer 60, to be fifted up if the cutter 412 was in

fire clay 26. If so, two seconds later, the rock detector 401 issues a command to raise

by one inch. If, after approximately six seconds the cowl 404 jumps up again,

reported by accelerometer 60, die detector 401 issues anotiier up command. It

would have to be a very unusual situation for this process to continue for very many

steps. However, eventuaUy the cutter 412 wiU be out of the rock and into the

breakaway zone, even if the cutter 412 found itself a few inches in the fire clay. Once

entering the breakaway zone, the next step up does not produce a change in the cowl

404 angle so that the rock detector 401 knows that it is in the breakaway zone of the

formation. At this point, repetitive cycling occurs— once up by 0.5 inches foUowed by down by 0.5 inches. So long as the accelerometer 60 confirms that the cutter is in

the desired breakaway zone, the cycling continues. Once the cowl 404 determines

that the cutter 412 has exited die breakaway zone, and is in the fire clay again, the

above sequence is repeated. Meanwhile, if control

is temporarily lost and the cutter 412 begins leaving coal, the accelerometer 60

reports this condition, which is confirmed and corrected by the divergence detector

401, as explained earfier. The rock detector 410 has enough inputs and enough logic

to regain control even if it is lost temporarily due to unusual events or conditions.

[0146] By this geosteering process, the rock detector keeps the drum adjusted at a

height so diat little or no rock is mined and Htde or no coal is left except for unusual,

anomalous conditions. Note that the basis for control is a direct measurement of the

formation being mined and the response by the rock detector is a direct result of the

measurements. A guidance system for the long-waU shearing machine is not

required, nor could it ever be nearly as accurate.

[0147] One significant benefit from geosteering the trailing cutter is that the need

for an operator to steer the cutter is efiminated. Whenever the cutting system is

reversed, the one operator that was controlling the leading cutting drum moves to

the other end of the machine to control what was the trailing drum but is then the

leading drum.

[0148] Under certain dynamic circumstances, the coal/rock interface 406 and the

cutter picks 407 may converge quickly, resulting in more rock 405 being taken. If a

particular mine faces this undesirable condition, a convergence rock detector 410 may be added to detect whenever large amounts of rock are being cut and mixed

with the coal 411. Detection of this condition wiU result in the convergence rock

detector 410 alerting the divergence rock detector 401 which wiU quickly raise the

cutter picks 407.

Since there is the possibility, in some mine conditions, for large amounts of rock to

faU from the roof, the divergence detector 401 will override the convergence rock

detector 410 in the event of a false signal.

[0149] Routing and protection of a power and signal cable to the divergence

detector 401 is difficult due to die continual impact from rock and coal. To solve

this problem, a battery 408 is instaUed in the cowl 404 to supply power to the

divergence detector 401. Signals are transmitted to the miner control center by a

radio link inside the detector 401 (not shown). A receiver module (not shown) in

the miner control center translates the signals to open a solenoid to raise the cutter

412 or to open tiie solenoid to lower the cutter 412, as needed.

[0150] Since the cowl 404 is free to rotate 360 degrees so that it can be reversed

whenever the machine is reversed, the divergence rock detector 401 must be disabled

whenever the cowl 404 is rotated into the leading drum position. An accelerometer

60 is incorporated into the photometric module 58 that detects the orientation of

the detector and disables its control capabifity once the detector 401 is rotated out of

its operating position. Whenever the detector 401 is returned to the proper position

for steering the trailing cutter 412 at the floor, the detector 401 reads the output of

the accelerometer 60 and automaticaUy activates the controls once the detector 401 has returned to its operating position.

[0151] It should be pointed out that in some cases, the accelerometer 60 may be a

smaU solid state device that is incorporated witiiin the electronics 57 inside the

photometric module 58.

[0152] FIG. 24 illustrates a rock detector 220 constructed in accordance with

another embodiment of d e invention. Previously described rock detectors 20, 120

include an accelerometer 60 or a cutter motion indicator 300. The accelerometer 60

determines the angle of the boom 11 relative to gravity and therefore assists in

determining the movement of the boom 11. The cutter motion indicator 300, with

the optical encoder 303, determines the angular movement of the boom 11. The

rock detector 220 includes the accelerometer 60 as weU as a rate gyro 222 (FIGS. 24

and 25).

[0153] As described above, curve fitting of gamma radiation readings are an

important aspect of die invention. The gamma radiation readings taken by the rock

detectors are correlated with measurements of incremental movements of the cutter

12 toward the rock interfaces 15, 16. Since changes in the position of the cutter 12

can be equated with changes in the thickness of uncut coal in front of the advancing

cutter 12, changes in the gamma radiation readings may be correlated to changes in

position of the cutter 12. The rate gyro 222 measures incremental movements of the

cutter 12. SpecificaUy, the rate gyro 222 measures the rotation of the rock detector 220, and since

the rock detector is mounted on the boom 11 the rotation of the rock detector 220

is the same as tiie rotation of the boom 11. The distance from the pivot pin 22 and

d e axis of d e cutter 12 is fixed and so d e movement of die rock detector 220 can

be calculated. By integrating the output of die rate gyro 222 with other measured

information, changes in the position of the cutter 12 and changes in the thickness of

the uncut coal can be known.

[0154] An advantage of the rate gyro 222 is that its output is relatively insensitive

to most vibrations. Only rotational vibration is measured, not lateral vibration, and

rotational vibration can be easily filtered out of the output. Nonetheless, since the

rate gyro 222 is unable to make an independent measurement of the actual

orientation of the boom and since a rate gyro 222 accumulates errors over time, it

may be used in conjunction with d e accelerometer 60, as iUustrate in FIG. 24.

During brief periods of time when lateral vibration is minimal, the accelerometer 60

is used to determine actual orientation of the boom 11 relative to gravity. Then, the

rate gyro 222 is used to determine angular rotation from diat position, even under

high vibration conditions.

[0155] The combination of the rate gyro 222 and the accelerometer 60 allows

precise measurement of boom 11 movement over short periods of time, such as 0.1

seconds, and also afiows determination of position over long periods of time as weU.

Short duration measurements aUow the gamma radiation readings to be accurately

correlated to incremental position changes so that curve fitting procedure is not significandy affected by the harsh vibration environment.

[0156] One methodology for die use of die rate gyro 222 includes automaticaUy

pausing the movement of the boom 11 when the cutter 12 has been determined to

be only a few inches from the predicted location of one of tiie rock interfaces 15, 16.

By pausing movement, the mechanical dynamics of the mining equipment are

minimized for a moment of time. Excess coal is cleared away, the mining equipment

setdes to its nominal position, and the accelerometer 60 estabfishes the position of

the boom 11 relative to the previous cutting stroke. From that point, the rate gyro

222, in combination with the accelerometer 60, accurately tracks the cutter 12 as it

moves toward the rock interface 15, 16.

[0157] Although not iUustrated, a second accelerometer 60 may be used in

conjunction with the rock detector 220. The first accelerometer 60, within the rock

detector 220, is utilized to measure the movement of the boom 11 relative to gravity.

The second accelerometer 60, positioned on the niining equipment, is utilized to

measure the angular movement of the mining equipment.

[0158] The above description and drawings are only iUustrative of preferred

embodiments of the present inventions, and are not intended to limit the present

inventions thereto. For example, although diere are significant technical and

practical benefits derived from incorporating d e logic elements within the explosion-

proof housing of the rock detector, it should understood that this element of the

geosteering system could be re-located into the control and display panel, or into the miner

control system, or otiier chosen places on the continuous miner. Any subject matter

or modification tiiereof which comes witiiin the spirit and scope of the foUowing

claims is to be considered part of the present inventions.

[0159] What is claimed is:

Claims

1. A control system for use with a mining machine having a boom,

comprising:

a gamma detector, comprising:

a scintiUation element; and

an accelerometer for ascertaining incremental movement of the boom.

2. The control system of claim 1, wherein said accelerometer is correlated

to a first position of the boom and is adapted to determine the angle of movement

relative to gravity of the boom from the first position.

3. The control system of claim 2, wherein said gamma detector further

comprises:

a photometric module; and

an optical coupler opticaUy coupling said scintiUation element with said

photometric module.

4. The control system of claim 3, wherein said photometric module

includes a photomultipHer tube, wherein said optical coupler opticaUy coupling said

scintiUation element with said photomultipfier tube.

5. The control system of claim 3, wherein said photometric module is

encased within an explosion proof housing.

6. The control system of claim 5, further comprising a dynamic housing

surrounding said gamma detector.

7. The control system of claim 6, further comprising an outer enclosure

surrounding said dynamic housing.

8. The control system of claim 7, wherein said outer enclosure includes

elastomeric ridges.

9. The control system of claim 6, further comprising a flexible support

sleeve positioned between said dynamic housing and said explosion proof housing.

10. The control system of claim 5, further comprising a flexible support

sleeve positioned between said explosion proof housing and said accelerometer.

11. The control system of claim 2, wherein said gamma detector further

comprises a rate gyro adapted to function in conjunction with said accelerometer to

determine the angle of movement relative to gravity of the boom from the first

position.

12. The control system of claim 11, further comprising a second

accelerometer positioned on the mining machine and adapted to determine angular

movement of the mining machine.

13. A control system for use with a rxiining machine having a boom,

comprising: a gamma detector; and

a cutter motion indicator having an optical encoder adapted to ascertain the

angular movement of die boom.

14. The control system of claim 13, furdier comprising an explosion proof

housing encasing said optical encoder.

15. The control system of claim 13, wherein said cutter motion indicator

includes a shaft, wherein the boom and said shaft are in connection such that rotation

of t e boom is transferable to said shaft.

16. The control system of claim 15, further comprising a pivot pin

connected to said cutter motion indicator.

17. The control system of claim 16, further comprising a drive train

assembly including:

a spline configured to aUow linear motion between said cutter motion

indicator and said pivot pin; and

a dual universal joint connecting said cutter motion indicator to said pivot pin;

wherein said spline and said dual universal joint are adapted to suppress linear

motion that is transverse to said drive train assembly from inducing forces on said

drive train assembly.

18. The control system of claim 17, wherein said drive train assembly

further includes a spring adapted to inhibit backlash by removing slack in said drive

train assembly.

19. The control system of claim 16, further comprising a lever attached to

die boom, said lever being adapted to transfer rotation of the boom to a point along

an axis of rotation of said pivot pin, tiiereby enabling transfer of the rotation of die

boom to said pivot pin.

20. The control system of claim 13, further comprising an accelerometer

adapted to determine angular movement of die mining machine.