WO2004002871A1

WO2004002871A1 - Straddle carrier position guidance system

Info

Publication number: WO2004002871A1
Application number: PCT/AU2003/000811
Authority: WO
Inventors: Michael Hildebrandt; Vincent Rouillard
Original assignee: Satellite Telemetry (Aust) Pty. Limited
Priority date: 2002-06-27
Filing date: 2003-06-27
Publication date: 2004-01-08
Also published as: AUPS325302A0

Abstract

The invention is a method of positioning a straddle carrier relative to a ship to shore (STS) crane including the steps of providing at least one signal generator mounted on the STS crane which generator produces a signal, providing a target mounted on the straddle carrier which can be viewed by a straddle carrier operator and moving the straddle carrier until the signal and target are aligned.

Description

STRADDLE CARRIER POSITION GUIDANCE SYSTEM

Technical area:

This invention relates to the area of vehicle position guidance systems and in particular to guidance systems for use in the accurate positioning of straddle carriers beneath ship cranes.

Background to the invention:

Straddle carriers customarily are driven over loads to be lifted or otherwise handled and comprise side bodies joined by transverse beams and having a locomotion means operated either from one side or above the carrier. Difficulties arise in the positioning of such devices particularly as many are operated manually and positioned accordingly.

In order to optimise the container ship loading process, straddle carriers are required to set down container boxes along a specific line perpendicular to the dock beneath the ship crane. This eliminates the need for continuous re-adjustment of the ship crane position in the longitudinal plane parallel to the dock.

At present, the ship crane operator lowers the spreader at the required location on the wharf and a chalk line is drawn to provide a visual reference mark to be used by straddle carrier drivers. Although effective, this method has a number of drawbacks and requires re-setting each time the ship crane is moved. Where an operator is required to visually locate a straddle carrier difficulty can be experienced in doing this accurately particularly where an operator's field of view is limited.

Outline of the invention:

It is an object of this invention to provide an automated system which will provide straddle carrier drivers with a position guidance system for any lane beneath the ship crane.

The invention is a method of positioning a straddle carrier relative to a ship to shore (STS) crane including the steps of:

- providing at least one signal generator mounted on the STS crane which generator produces a signal.

- providing a target mounted on the straddle carrier which can be viewed by a straddle carrier operator and

- moving the straddle carrier until the signal and target are aligned.

It is preferred that the target be indicators marked on at least one display panel.

It is preferred that the display panel be viewed directly by the operator however it may also be preferred that the display panel may alternatively be viewed on a display screen. It is further preferred that this display screen be a component of a monochrome camera/video monitoring system visible to the operator.

While any appropriate signal or receiver may be used it is preferred that the signal be one or more vertically oriented light sheets generated from a laser light source mounted on the STS crane. It is further preferred that any resulting light sheet be displayed directly onto a horizontal display panel mounted on the straddle carrier within the operator's field of view. In this configuration the vertical light sheets are directed across the travel lanes from behind the straddle carrier operator in clear view of the display panel positioned in front of the operator.

It is also preferred that the laser be mounted overhead on structures fitted on the main gantry rail structure of the STS crane and directed downwards towards the display panel of the straddle carrier. It may however be preferred that the lasers be mounted in a horizontal configuration, preferably on a column fitted to the main frame of the STS crane at a height corresponding with the display panel.

It may also be preferred that the display panel be connected to a visual display and audio alarm unit mounted in the straddle carrier cabin within the field of view of the operator. ln order that the invention may be more readily understood we shall describe by way of non limiting example specific embodiments thereof with reference to the accompanying drawings.

Brief Description of the Drawing Figures

Fig. 1 Shows a plan view of the components of the invention where the laser sensors are vertically oriented.

Fig. 2 Shows a schematic perspective view of the straddle carrier, laser light source and display panel.

Fig. 3 Shows a plan view of an embodiment of the invention wherein the laser is oriented horizontally.

Description of a Preferred Embodiment of the Invention.

Figure 1 shows a ship 10 alongside wharf 11 with travel line markers 12. As shown also in Figure 2 a straddle carrier 20 is driven along lines 12 under STS crane 33 having footprint 30. Figure 1 shows the loaded straddle carrier 20 positioned generally centrally between the STS crane main rails 32 when the fan shaped narrow beam 41 from laser source 40 is located between lines (target) 52 on the display panel 50 located outside the windscreen of the operator's cabin 60 of the straddle carrier 20.

In this embodiment of the invention a plurality of laser locations 40 are shown mounted on the STS crane 33 and generating a vertical light sheet 41 as shown in Figure 2.

In an alternative embodiment of the invention at least one laser 40 is mounted onto a column fitted to the main frame of the STS crane at a height corresponding to that of the display panel 50 as shown in Figure 3.

The light emitted by this laser is narrow horizontally and fan shaped or non-divergent parallel in the vertical plane as in the previous embodiment . In this configuration the vertical light sheet is directed across the travel lines 12 from behind the straddle carrier operator in clear view of the display panel positioned in front of the operator.

In both configurations, the orientation of the reference light sheets are such that they intersect the travel lanes at right angles. The light sheets are positioned at pre-set distances from the centre-line of the STS crane. These distances are such that the light sheets coincide with a mark on the display panel when the centre of the container (hence the straddle carrier) is aligned with the centre of the STS crane spreader. From the operator's point of view, as the straddle gets within a suitable distance (say 600 mm) from the container set-down zone, a section of the laser line will appear on the forward most extremity of the display panel and, with forward motion of the straddle, the line will appear to move toward the right (toward the markers 52 on the display panel). The operator uses the position of the laser line on the display panel as a direct indication of the distance remaining to reach the container set-down zone.

Because the system relies on visible light it is important that the laser reference light sheet can be clearly seen with the naked eye under all possible ambient sunlight conditions. The visible wavelengths of the solar spectrum correspond to that section of the spectrum that contains the most energy and intense light. In contrast, the optical power output of visible lasers must, for safety reasons, be restricted to a few milliwatts.

A compromise between visibility and safety needs to be made while ensuring that adequate contrast between the laser reference light sheet and ambient sunlight is achieved. This requires: a. Careful selection of the laser wavelength. b. Careful selection and management of the laser intensity. c. Making use of optical filters. ln addition safety regulations pertaining to lasers vary between countries and even States of a given country. The effective optical intensity of the lasers used in this system are kept safe by: a. Using holographic line generation which effectively spreads the optical power contained within the laser spot into a long thin line which has the effect of diluting the optical intensity to safe levels. b. Using eye-safe lasers (sich as Lasiris® or similar) which produce laser line generators with a uniform (flat) intensity distribution as opposed to Gaussian intensity distributions produced by standard lasers. This has the effect of eliminating the optical "hot spot" found in standard line generators. c. Locating the laser light source such that access is restricted. d. Locating control of the laser light sources within the STS crane control cabin to ensure that the light sources are on only when the crane is in operation.

The system uses one or more commercially available CW (continuous wave) laser line generators along with, when required, a suitable cylindrical lens in order to generate a parallel, non-divergent light sheet. This ensures that the intensity of the light sheet across the entire operational range remains more constant than with a divergent light beam.

The laser wavelength should be such as to maximise visibility in ambient sunlight eg: 635 nm or other suitable visible wavelength. Alternatively, if the display panel is to be viewed via a camera and suitable filter, or any other appropriate means, other non- visible wavelengths may be used such as eyesafe wavelengths (greater than 1500 nm).

The laser intensity used is sufficiently high to be clearly visible by the operator without exceeding the safety limits as prescribed by the relevant regulations. The device may also be fitted with an intensity controller which is adjustable either manually or automatically to compensate for variation in ambient conditions (ie: ambient light, snow, rain and fog). The automatic adjustment is made by continually monitoring the local atmospheric conditions with a reference light beam and the ambient light conditions can also be continually monitored. These parameters can be fed into a controller which, in turn, controls the intensity of the laser light.

The display panel is mounted on the straddle carrier at a location suitable for easy viewing by the straddle operator while remaining within sight of the reference light sheet. The target zone, corresponding with the desired container set down location, is clearly identified on the display panel. The display panel is to be suitably long to provide the operator with adequate warning upon approach of the target zone.

Operator visibility of the reference laser line on the display panel is enhanced by: Careful selection of the display panel surface material whereby optimum reflection and partial scattering is achieved. Partial scattering is required in order to enhance visibility over a range of viewing positions (operator eye position). A mirror-like reflection is not desired. Galvanised steel has been found to offer such desirable attributes.

It is also preferred that the display panel is of such shape so as to direct the reflected scattered light toward a focal point corresponding with straddle operator's eyes. This is effected by using a parabolic shaped display panel. To enhance visibility, an optical filter positioned over the display panel in such a way that it affects both the incident laser light and the scattered light from the display panel. The filter, the dimensions of which need to match those of the display panel, are of the absorptive type. Alternatively, interference filters may be used.

The filter needs to match the laser wavelength and have the narrowest possible bandwidth while ensuring that wavelength shift due to thermal effects are not problematic. In the case of polarised light sources, in order to maximise optical transmission through windows in enclosures and various optical filters, these should be set at Brewster's angle to maximise transmission. If polarised, the laser should be polarised in an orientation suitable to the filters and the geometrical arrangement of the system. If required, the laser polarisation may be rotated by means of an optical retarder (1/2 wave plate).

Should geometrical constraints on the straddle carrier prevent positioning of the display panel in direct view of the operator, viewing of the display panel is achieved via a monochrome video camera / monitor system. This system offers further advantages in that the camera can be fitted with a readily available high-quality, narrowband interference filter to further enhance visibility.

Furthermore, this system can be used to monitor an additional display target oriented in such a way as to allow detection of the laser reference light emanating from either direction (behind and forward). This system can be used to allow straddles to operate in those lanes outside the SRS crane footprint while having the laser mounted horizontally on the STS crane. In such a configuration, all lanes can be used in both directions with just two laser line generators mounted horizontally on the shipside of the STS crane.

The invention as described remains operational for any combination of straddle carrier and ship crane. The concept of the invention could however be adapted for use where any moveable device is sought to be located relative to a fixed object such as the ship crane in the example described. In addition while a visible signal is preferred it is envisaged that the concept of the invention could include any form of transmitted signal with an appropriate receiver, use of a visible signal is of course the least expensive option.

The preferred embodiment of the invention described is thus extremely cost effective and reliable despite replacing the fairly primitive means of positioning a straddle carrier in relation to a ship crane. The main advantages of the invention are as follows:

1. The system provides a continuous visual display directly analogous to the position of the straddle carrier relative to the target container set-down location. This inherent simplicity makes it operator-friendly as it provides direct and continuous location information to the operator.

2. No re-adjustment of the system is required - the laser(s) are securely mounted on the ship to shore (STS) crane and as the crane moves, so do the laser(s), and the reference lines.

3. The light sheet produced by each laser accounts for a range of straddle carrier heights due to variations in vehicle type, load and surface topography.

4. In the vertical configuration, reference light sheets will be generated for each travel lane which will enable all lanes to be used simultaneously and by any straddle carrier. In the horizontal configuration, a single reference light sheet will be generated across all travel lanes which will enable all lanes to be used by any straddle carrier.

5. In the case where direct view is possible, viewing of the display panel is passive and does not require power, electronic circuitry, signal conditioning, processing or calibration. Where a camera is necessary, only readily available surveillance grade monochrome camera / monitor systems need be included in the straddle carrier.

6. The system's simplicity and the absence of "black boxes" will lead to a better understanding of operation of the system by the drivers and hence an increased likelihood of acceptance. 7. The system is operational for any combination of straddle carrier and ship crane.

8. In the case where the working area is restricted to the footprint of the STS crane, only two lasers are required for bi-directional traffic while each straddle carrier is be fitted with a display panel.

Whilst we have described herein two specific embodiments of the invention it is envisaged that other embodiments of the invention will exhibit any number of and any combination of the features previously described and it is to be understood that variations and modifications in this can be made without departing from the spirit and scope of the invention.

Claims

The claims defining the invention are as follows:

1. A method of positioning a straddle carrier relative to a ship to shore (STS) crane including the steps of:

- moving the straddle carrier until the signal and target are aligned.

2. A method as claimed in claim 1 wherein the target is located on at least one display panel.

3. A method as claimed in claim 2 wherein the display panel can be viewed directly by the straddle carrier operator.

4. A method as claimed in claim 2 wherein the display panel may be viewed on a display screen which display screen is a component of a monochrome camera/video monitoring system visible to the operator.

5. A method as claimed in claim 3 or claim 4 wherein the signal is provided from one or more vertically oriented light sheets generated from a laser light source mounted on the STS crane.

6. A method as claimed in claim 5 wherein, when signal and target are aligned, the resulting light sheet is displayed directly onto a horizontal display panel mounted on the straddle carrier within the operator's field of view.

7. A method as claimed in claim 6 wherein the laser light source is mounted overhead on structures fitted on the main gantry rail structure of the STS crane and directed downwards towards the display panel of the straddle carrier.

8. A method as claimed in claim 3 or claim 4 wherein the signal is provided from one or more vertically oriented light sheets generated from a laser light source mounted in a horizontal configuration on a column fitted to the main frame of the STS crane at a height corresponding with the display panel.

9. A method as claimed in claim 8 wherein, when signal and target are aligned, the resulting light sheet is displayed directly onto a horizontal display panel mounted on the straddle carrier within the operator's field of view.

10. A method substantially as herein described.