US3689788A

US3689788A - Rollability prediction system

Info

Publication number: US3689788A
Application number: US83365A
Authority: US
Inventors: Peter J Wong; Dale W Ross; Kenneth W Gardiner
Original assignee: Southern Pacific Transportation Co
Current assignee: Southern Pacific Transportation Co
Priority date: 1970-10-23
Filing date: 1970-10-23
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: AT319328B; CH534603A; AU3162971A; DE2150833C2; NO136034C; AU463767B2; FR2110937A5; GB1335480A; CA937314A; NO136034B; JPS5543939B1; SE376738B; IT942079B; DE2150833A1

Abstract

In a railway classification yard a car''s rollability is measured several times as it is traveling through the upper yard. These measurements are employed to predict the car''s rollability on the bowl track. From the predicted rollability, means are provided to determine what the car''s velocity should be when it leave the last retarder just prior to entering the bowl portion of the yard in order that it travel the distance required to couple to a stationary car at the proper velocity.

Description

United States Patent 7 Wong et al. Sept. 5, 1972 [54] 'ROLLABILITY PREDICTION SYSTEM FOREIGN PATENTS OR APPLICATIONS [72] Inventors: Peter J- g, Menlo Park; Dale 924,205 4/1963 Great Britain ..246/l82 A Ross, Sunnyvale; Kenneth W. Gardmer Menlo. Park n of Cahf- Primary Examiner-Gerald M. Forlenza [73] Assignee: Southern Pacific Transportation Assistant Examiner 6e0rge Libman Company, San Francisco, Calif. Attorney-Lindenberg, Freilich & Wasserman [if] lllrled: N Oct. 23, 1970 [57] ABSTRACT PP- 83,365 In a railway classification yard a car.s rollability is I measured several times as it is traveling through the [52] US. Cl. ..246/ 182 A upper d, These measurements are employed to pre- Clthe car's on the track FfQm the [58] Field of Search ..246/182 A; 275/ 150.2 predicted rollability means are provided to determine what the cars velocity should'be when it leave the last [56] Refergnces C'ted retarder just prior to entering the bowl portion of the UNITED STATES PATENTS yard in order that it travel the distance required to 1 cou le to a stationa car at the r0 r veloci 3,054,893 9/1962 Dasburg ..246/ 182 A p ry 'l ty 3,014,658 12/1961 Hermes 246/182 A 4 Claims, Drawing 22 ,26 4

F t \2 V L MA$TER 72? Y EETARDER COMPUTER ,3'6 Rm (DMPUTER ,so vELocn'Y cbfivirr n I58 coM 5TER R5 comm 122mm CONTROL BOWI TRACK EPEED DETECTOR rmmtnszr 5 m2 sum 1 or 2 PATENTEDSEP 5 I972

sum

2 or 2 SUMMER MULTWUER MUL'HPUER CKT SUMMER MULT! PLIER CKT HJB RACT R DETECTOR I VELOCITY vumPueR cm DETECTOR 2 W we m v m 5 MULTlPUERl SUBTRAGDR BOM ROLLABILITY PREDICTION SYSTEM BACKGROUND OF THE INVENTION This invention relates to railway classification yards and more particularly to an improved automatic control system therefor.

One crucial calculation in the successful operation of a railroad hump yard is the ability to predict accurately the rolling behavior of a car on the bowl track on the basis of upper yard measurements. If the car is a harder roller than predicated, then the car will stop short of couplingto cars on the bowl track. Conversely if the the path of the car on its way to the bowl track are used to provide the car with the proper velocity.

It is known that a cars rollability changes during the course of its travel and therefore a single rollability measurement does not always provide the proper answer for controlling the cars velocity.

OBJECTS AND-SUMMARY OF THE INVENTION An object of this invention is the provision of a system for increasing the accuracy of the prediction of the cars rollability on a bowl track.

Another-object of this invention is the provision of a novel car retarder control system.

Yet another object of this invention is the provision of a novel and useful car control system.

The foregoing and other objects of the invention are achieved by making several measurements of the cars rolling behavior in the course of its transition through the upper yard from which a fairly accurate prediction of the cars rolling behavior on the bowl track can be calculated. With this data, and from a knowledge of the distance the car has .to roll, it is a simple matter to calculate the velocity required for the car to reach its train. From a knowledge of the velocity required, one can measure the velocity of the car passing through the tangent point retarder, which is the last retarder just before the car is upon the bowl track. The retarder is energized to bring the cars velocity down to the calculated value.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of an embodiment of this invention.

FIG. 2 is a block schematic drawing of a rollability predicting circuit which may be employed in this invention.

FIG. 3 is a block schematic diagram of a bowl rollability predicting circuit.

FIG. 4 is a block schematic diagram of an arrangement for controlling the last retarder before the bowl track in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS the From Newtons second law of motion of relationship between the car velocity and its rollability can beexpressed by the differential equation:

where r dV/dt time rate of change of cars velocity (ft/sec?) ft. of vertical drop if gmle or ft. of horizontal run g gravity constant, ==32.l 6 ft/sec) R rollability A car traveling from the hump to the bowl track will normally travel over a rollability measurement station, as a result of which, as indicated previously the retarders are controlled to determine the cars bowl track velocity. I

Referring now to FIG. 1, there is shown schematically a track section 10in a railway classification yard and along the upper track section there is a master retarder 12, followed by a group retarder 14, followed by .a tangent point'retarder 16, which is positioned just before the bowl track 18. In accordance with this invention, velocity is measured at more than one point along the upper track. This occurs for example by determining the velocity with velocity detectors. A velocity'detector 20 measures the velocity of a car as it comes out of the master retarder 12. A second velocity detector 22 measures the velocity of the car as it enters the group retarder 14. From the difference in velocities measured between these two detectors, one can compute, using the formula (1) a rollability for the car which is designated as R1. This computation is provided by an R1 computer, 24. 1 I

The velocity of the car as it leaves the group retarder v is measured by a velocity detector 26. The velocity of the car a distance downstream from the exit from the group retarder is again measured by a fourth velocity detector 28. Thedifference in velocities between the

detectors

26 and 28 are entered into an R2 computer, 30, which provides a second rollability quantity designated as R2.

The rollability is again measured by using a velocity detector 32 to measure the velocity of the'car as it passes a given point on the track. The velocity of the car just before it enters the tangent point retarder 16 is measured by a velocity detector 34. The difference between these two velocities is entered into an R3 computer to produce a quantity R3.

The three (or more if desired) rollabilitymeasurements R1, R2 and R3 are entered into an R Bowl Computer 36. This measures R Bowl and applies it to a V Computer (retarder velocity) 38. This V Computer produces at its output the velocity required for the car when it leaves the tangent point retarder. A suitable speed detector 42, such as a radar detector, measures control 44. Another input to the retarder control is the.

calculated Vs from the computer 38. The retarder control compares these velocities and controls the retarder to slow down the car until equality is established at which point-the car may be released with the proper velocity.

From equation (1), the term R can be expressed in terms of two velocity measurements and the other quantities as:

' KiZKfi M where V measured car "velocity at point No. l (ft/sec) V, measured car velocity at a point No. 2, further down the track (ft/sec) d linear distance along the track between points No. l and No. 2 (ft.) estimated value of the average track grade between points No.1 and 2. (ft. of verticaldrop/ft.

of horizontal run between points 1 and 2). lg;- gravity constant (=32. l 6 ft/s'ec) R rollability (lbs. per ton) FIG. Zshows a schematic diagram illustrative of an R1, or R2 or R3 computer. It is an analog computer derived from the equation (2).

The outputs of the first two

velocity detectors

20, 22 for example are applied to a summer 50, and to a subtractor 52 respectively providing V, V and V V outputs. These are applied to a multiplier 54. Its output, which is V} V, is applied across a potentiometer 56, the slider of which is set to provide as output,

where the function f (R R,,R is unknown and to bedetermined by a curve fitting process.

From the mathematical theory associated with functions, it is known that if f(R R R is well behaved,

then it can be approximated by a power series expansion in the variable R R and R The degree of accuracy to the approximation depends on the highest order terms. The greater the number of terms in the expansion the more accurate the approximation.

The simplest power series approximation to the unknown function flR R R is to assume that it is linear, i;e.,

FIG. 3 is a schematic drawing of how equation (3) may be implemented so that the term R can be automatically derived from the quantities. The constants a, through a are respectively derived (in a mariner to be shown later herein) by using the

respective potentiometers

64, 66, 68, and 70, which are connected across potential sources respectively 72, 74, 76 and 78. a is multiplied with R by a multiplier circuit 80. a, is multiplied with R, by a multiplier circuit 82. A multiplier circuit 84 multiplies a and R The outputs of the three multiplier circuits together with a, are applied to a summing circuit 86. Its output is R Now in order to determine the coefficients a through a a large number of cars, say 100 is run through the yard and for each car one measures the quantities R R, and R,. In addition one takes a velocity measurement to calculate R This last measurement is taken in the same manner as the previous rollability measurements by measuring the velocity of a car as it leaves the tangent point'retarder and also at a predetermined location downstream from this and using equation 1. a

One now has a large collection of data consisting of. R R, and R and R foreach car. One then uses a least square error fit technique to find those coefficients a a a and a in equation (3) that minimize the sum of the square errors, that is, if there are any cause for which the experimental data has been taken, one solves for the coefficients that minimize the quantity all)? There are several computer programs available commercially which can solve this problem and find the bowl The desired coupling speed is normally a constant. From a knowledge of the length of track and the number of cars already sent to form a train d is easily determined and can be automatically totaled.

FIG.- 4 shows an analog computer for calculating quantity V,, which is the output velocity desiredfrom the tangent point retarder. The product R g is determined by a multiplier having as one input the constant 3, derived from a potentiometer 92 across a v potential source 94. The other input is derived from a potentiometer 96 across which is applied the previously calculated quantity R The setting of the potentiometer provides an output bowl .290

The output of the multiplier is applied to a subtractor 98, having as its other input the constant term 0 g. This is derived from a potentiometer 100 connected across a derived by establishing an analog quantity V by means of a potentiometer 108 connected across a potential source 110. The output of the potentiometer is connected to a squaring circuit 112. This provides the quantity V The output of the summing circuit 106 is connected to a square root circuit 114 whose output is the term V,. 'As previously pointed out in connection with FIG. 1, V, is compared with the actual velocity measured for the car as it is passing through the tangent point retarder which is instructed by any quantity to retard the car until V, and the actual measured velocity are the same.

The circuits shown herein, being comprised of mu]- tiplier and subtraction circuits, summers, squaring circuits and square root circuits, are all Well known operational amplifier circuits which are commercially purchasable. Velocity, detectors also known as speed detectors are well known in the art as is the radar speed measuring system.

Accordingly, there has been described and shown herein a novel and useful arrangement for providing a substantially accurate measurement of the rollability of a car from which one can determine the proper entrance velocity of a car upon the bowl track.

What is claimed is: I 1. In a railway classification yard of the type having a hump over which a track extends down to a bowl track section, and there is a master retarder at the hump track section, a tangent point retarder at the commencement of the bowl track section, and at least one group retarder positioned along the track section between the master retarder and the tangent point retarder, the improvement comprising:

means for measuring a car rollability along several sections of track between the master retarder and the tangent point retarder, computer means to which the rollability measurements taken along said several sections of track are applied for solving the equation,

where R is car bowl rollability, R R R,, are the rollability measurement made at each of said several sections of track, a, a a a,, are empirically predetermined rollability coefficients for each track sections along which a rollability measurement is made,

means for determining a required velocity from the derived bowl rollability for said car, I

means for measuring the velocity of said car within said tangent point retarder, and

means for controlling said tangent point retarder responsive to said measured velocity and said required velocity to provide said car with said required velocity as it leaves said tangent point re- 2. l i i i'fiilway classification yard as recited in claim 1 wherein said means for determining a required velocity from the derived bowl rollability towards said car comprises a computer means for solving the equation means for measuring the car rollability between the master retarder and the group retarder, the second-and third means for respectively measuring the car rollability along spaced distances between said group retarder and said tangent point retarder.

4. In a railway distribution yard having a hump and a track extending thereover down to a bowl track, and including a master retarder at said hump, and a tangent point retarder at the commencement of said bowl track, a method of establishing a proper coupling velocity for a car entering said bowl track comprising:

measuring the rollability of a car at a plurality of locations as said car moves from said hump down toward said bowl track, multiplying each rollability measurementby a rollability coefficient previously determined for each track section along which a rollability measurement is made, adding the results of all said multiplications to obtain the bowl rollability, deriving from said bowl rollability a proper coupling velocity for said car' to enter upon said bowl track, measuring the velocity of said car within said tangent point retarder, comparing said measured velocity with said proper coupling velocity, and controlling said tangent point retarder to retard the velocity of said car until its measured and computed velocity are the same.

Claims

1. In a railway classification yard of the type having a hump over which a track extends down to a bowl track section, and there is a master retarder at the hump track section, a tangent point retarder at the commencement of the bowl track section, and at least one group retarder positioned along the track section between the master retarder and the tangent point retarder, the improvement comprising: means for measuring a car rollability along several sections of track between the master retarder and the tangent point retarder, computer means to which the rollability measUrements taken along said several sections of track are applied for solving the equation, Rbowl ao+a1.R1+a2.R2+ . . . an.Rn, where Rbowl is car bowl rollability, R1, R2 . . . Rn are the rollability measurement made at each of said several sections of track, ao, a1, a2 . . . an are empirically predetermined rollability coefficients for each track sections along which a rollability measurement is made, means for determining a required velocity from the derived bowl rollability for said car, means for measuring the velocity of said car within said tangent point retarder, and means for controlling said tangent point retarder responsive to said measured velocity and said required velocity to provide said car with said required velocity as it leaves said tangent point retarder.

2. In a railway classification yard as recited in claim 1 wherein said means for determining a required velocity from the derived bowl rollability towards said car comprises a computer means for solving the equation where Vr is the required velocity, Vc is the desired coupling speed, g is the gravity constant, theta is the estimated value of the average track grade, dr is the distance between the output side of the tangent retarder and the coupling point of the car.

3. In a railway classification yard as recited in claim 1 wherein said means for measuring a car rollability along several sections of track between the master retarder and the tangent point retarder include a first means for measuring the car rollability between the master retarder and the group retarder, the second and third means for respectively measuring the car rollability along spaced distances between said group retarder and said tangent point retarder.

4. In a railway distribution yard having a hump and a track extending thereover down to a bowl track, and including a master retarder at said hump, and a tangent point retarder at the commencement of said bowl track, a method of establishing a proper coupling velocity for a car entering said bowl track comprising: measuring the rollability of a car at a plurality of locations as said car moves from said hump down toward said bowl track, multiplying each rollability measurement by a rollability coefficient previously determined for each track section along which a rollability measurement is made, adding the results of all said multiplications to obtain the bowl rollability, deriving from said bowl rollability a proper coupling velocity for said car to enter upon said bowl track, measuring the velocity of said car within said tangent point retarder, comparing said measured velocity with said proper coupling velocity, and controlling said tangent point retarder to retard the velocity of said car until its measured and computed velocity are the same.