SPREADER POSITION CONTROL

Abstract

A method of providing position control information for controlling the movement of a spreader (400) of a crane (10) towards a spreader target position is disclosed. The method comprises measuring both the distance to the loading/unloading target position (32, 36) and the distance to a position of the spreader (400) for determining both a loading/unloading target position (32, 36) and the position of the spreader (400) in a fixed coordinate system. The method also comprises causing position control information corresponding to the position of the spreader (400) and the loading/unloading target position (32, 36) to be transmitted to the crane (10).

Claims

1. An apparatus for providing position control information corresponding to a position of a spreader of a crane and a loading/unloading target position, the apparatus comprising: one or more detectors for measuring distance; and a transmitter for causing position control information to be transmitted to the crane; wherein the apparatus is arranged to measure, using the one or more detectors both the distance to the loading/unloading target position and the distance to the position of the spreader for determining both the loading/unloading target position and the position of the spreader in a fixed coordinate system; and cause, using the transmitter, position control information corresponding to the position of the spreader and the loading/unloading target position to be transmitted to the crane; wherein the one or more detectors are arranged to be positioned in terminal infrastructure.

2. An apparatus according to claim 1, wherein determining the loading/unloading target position comprises determining the position of a container on a vehicle and/or the position of one or more twistlocks on a vehicle.

3. An apparatus according to claim 1, wherein the loading/unloading target position is determined from a three-dimensional point cloud.

4. An apparatus according to claim 1, wherein the fixed coordinate system is a block coordinate system corresponding to a single block in a terminal.

5. An apparatus according to claim 1, wherein the apparatus is arranged to measure the distance to the position of the spreader when the spreader has been moved by the crane into a measurement space having one or more of the following: a target altitude of the spreader, a threshold for maximum altitude of the spreader and a threshold for minimum altitude of the spreader.

6. An apparatus according to claim 5, wherein the apparatus is arranged to have a field-of-view which simultaneously includes both the measurement space and the loading/unloading target position.

7. An apparatus according to claim 1, wherein the apparatus is arranged to provide position control information for a plurality of loading/unloading lanes at a terminal.

8. An apparatus according to claim 1, wherein the apparatus is arranged to measure, with an additional measurement using the one or more detectors, the distance to the position of the spreader when the spreader is coupled to a container for loading/unloading and the container is positioned at the loading/unloading target position.

9. A system for providing position control information for controlling the movement of a spreader of a crane towards a spreader target position, the system comprising: a first apparatus arranged to be installed in the crane the first apparatus comprising a receiver for receiving position control information and a controller for controlling the movement of the spreader; and a second apparatus for providing position control information corresponding to a position of the spreader and a loading/unloading target position, the second apparatus comprising one or more detectors for measuring distance and a transmitter for causing position control information to be transmitted to the first apparatus; wherein the second apparatus is arranged to measure, using the one or more detectors both the distance to the loading/unloading target position and the distance to the position of the spreader for determining both the loading/unloading target position and the position of the spreader in a fixed coordinate system; and cause, using the transmitter, position control information corresponding to the position of the spreader and the loading/unloading target position to be transmitted to the first apparatus wherein the one or more detectors are arranged to be positioned in terminal infrastructure.

10. A system according to claim 9, wherein the first apparatus is arranged to direct the spreader into a measurement space for determination of the position of the spreader.

11. A system according to claim 9, wherein the first apparatus is arranged to slow or stop the movement of the spreader for determination of the position of the spreader.

12. A system according to claim 9, wherein the system is arranged, when a container is carried by the spreader, to use position control information corresponding to the position of the spreader to determine, in the fixed coordinate system, an outer boundary of the container.

13. A system according to claim 9, wherein the first apparatus comprises one or more inclination sensors for measuring the inclination of the spreader.

14. A system according to claim 9, arranged to calibrate the determination of the position of the spreader using a measured distance to the position of the spreader when the spreader is coupled to a container for loading/unloading and the container is positioned at the loading/unloading target position.

15. A method of providing position control information for controlling the movement of a spreader of a crane towards a spreader target position, the method comprising: measuring both the distance to the loading/unloading target position and the distance to a position of the spreader for determining both a loading/unloading target position and the position of the spreader in a fixed coordinate system; and causing position control information corresponding to the position of the spreader and the loading/unloading target position to be transmitted to the crane the measurement is performed using one or more detectors which are arranged to be positioned in terminal infrastructure.

16. A method according to claim 15, comprising: measuring, with an additional measurement, the distance to the position of the spreader when the spreader is coupled to a container for loading/unloading and the container is positioned at the loading/unloading target position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are included to provide a further understanding and constitute a part of this specification, illustrate embodiments and together with the description help to explain the principles of the invention. In the drawings:

[0049] FIG. 1 schematically illustrates a system according to an embodiment in a perspective view,

[0050] FIG. 2 illustrates a block diagram of a system according to an embodiment,

[0051] FIG. 3 illustrates a flow diagram of a method according to an embodiment,

[0052] FIG. 4 illustrates a spreader according to an embodiment in a side view (left) and an overhead view (right), and

[0053] FIG. 5 illustrates providing position control information according to an embodiment.

[0054] Like references are used to designate equivalent or at least functionally equivalent parts in the accompanying drawings.

DETAILED DESCRIPTION

[0055] The detailed description provided below in connection with the appended drawings is intended as a description of the embodiments and is not intended to reprsent the only forms in which the embodiment may be constructed or utilized. However, the same or equivalent functions and structures may be accomplished by different embodiments.

[0056] FIG. 1 schematically shows a system 100 for providing position control information for controlling the movement of a spreader 400 of a crane 10 towards a spreader target position. The system 100 may be arranged to be used in a terminal such as a container freight terminal, for example at a port. The terminal may comprise at least one block with a loading/unloading area. The loading/unloading area may comprise one or more loading/unloading lanes 40, 42 (referred here also as lanes). The lanes 40, 42 may be arranged as traffic lanes for vehicles 30, 34 such as trucks and/or trains. The lanes 40, 42 may be parallel with respect to each other. The lanes 40, 42 are arranged so that vehicles 30, 34, may drive through them and stop for loading/unloading by one or more cranes 10. A vehicle 36, 38 may comprise one or more twistlocks 38 for fixing the load 20 to the vehicle 30, 34. As an example, one crane 10 may be arranged to handle loading/unloading in one loading/unloading ar-ea. The loading/unloading area may comprise a desig-nated area for the load 20. The terminal comprises terminal infrastructure 50 such as buildings and fixed structures.

[0057] A crane 10 is arranged to move in the loading/unloading area for loading/unloading the load 20 to and/or from one or more vehicles 30, 34. The crane may comprise a bridge and/or a gantry. The crane 10 may comprise a trolley 12 which may be arranged to move along the bridge. The crane 10 comprises a spreader 400 for moving the load 20. Typically, the spreader 400 is arranged to hang from ropes and/or cables 14, which may be adjusted to alter the altitude of the spreader 400. Optionally, the spreader 400 may be connected to a headblock 510. This allows the spreader 400 to be exchanged with a new one, if necessary, without detaching the ropes and/or cables 14. The spreader 400 may be coupled to a trolley 12 for moving the spreader 400 laterally. The coupling may be also indirect, for example when the spreader 400 is connected to a headblock 510 which, in turn, is coupled to a trolley 400. The coupling is arranged to allow the spreader 400 to be moved vertically, for example by ropes and/or cables 14. The spreader 400 can be arranged to be moved horizontally by moving the crane horizontally, for example so that the whole bridge and/or gantry moves horizontally.

[0058] The system 100 comprises a first apparatus 250, which may be installed in the crane 10. The first apparatus 250 is arranged to receive position control information and use the position control information to control the movement of the spreader 400 towards the spreader target position. As an example, the first apparatus 250 may be arranged to be installed at the trolley 12 but it may also be installed in other parts of the crane 10. The first apparatus 250 may also be implemented as a distributed system with some components installed separately from other components.

[0059] The system 100 comprises a second apparatus 200 for providing position control information corresponding to the position of a spreader 400 of a crane 10 and a loading/unloading target position 32, 36. The loading/unloading target position 32, 36 may be on a vehicle 30, 34, e.g. on its trailer. The loading/unloading target position 32, 36 can be used to determine a spreader target position for loading/unloading. The spreader target position is therefore typically slightly above the loading/unloading target position, the distance being determined based on the height of the load. The system 100 or the second apparatus 200 may be arranged to provide position control information corresponding to a position of the spreader 400 and the loading/unloading target position 32, 36 for loads 20 of varying sizes. For example, the system 100 may be arranged to receive and/or determine, for example by measurement, the height of the load 20 for determining the spreader target position based on the loading/unloading target position 32, 36 and the height of the load 20. Also, the second apparatus 200 may be arranged to simultaneously observe the position of the spreader 400 and the loading/unloading target position 32, 36 for providing position control information even when the height of the load 20 is not fixed. During unloading, the loading/unloading target position 32 can be a position of the load 20, for example a position of a container. This position 32 may be determined based on one or more features of the load 20 such as one or more twistlocks of a container and/or one or more corners of a container 20. During loading, the loading/unloading target position 36 can be a position of a loading platform, for example the position of a loading platform, such as a trailer, of a vehicle 30, 34. This position 36 may be determined based on one or more features of the loading platform such as one or more twistlocks 38 of a vehicle 30, 34 and/or one or more corners of a vehicle 30, 34.

[0060] The second apparatus 200 has a field of view 210 for providing position control information corresponding to the position of a spreader 400 of a crane 10 and a loading/unloading target position 32, 36. The field-of-view 210 may extend across one or more lanes 40, 42. The field-of-view 210 may be fixed. The field of view 210 may be continuous or it may be arranged to extend discontinuously across two or more lanes 40, 42, which may be adjacent. The second apparatus 200 may be arranged to be positioned between two lanes 40, 42. The second apparatus 200 can thereby be arranged to provide position control information for these two lanes 40, 42. The second apparatus 200 may even be arranged to use a single detector 222 for providing position control information for these two lanes 40, 42. Also, this allows reducing distance between the second apparatus 200 and the loading/unloading target position 32, 36 allowing the second apparatus 200 to be configured for reduced distance measurement, improving accuracy.

[0061] A measurement space 212 may be used to initiate some or all parts of the process of providing position control information corresponding to the position of a spreader 400 of a crane 10, in particular the measurement process where the distance to the position of the spreader 400 is measured for determining the position of the spreader 400 (referred here also as spreader measurement process). The loading/unloading target position 32, 36 may be determined simultaneously and/or separately, for example before initiating the spreader measurement process. The spreader measurement process may, however, also comprise determining the loading/unloading target position 32, 36 one or more times. The crane 10 may be arranged to move the load and/or the spreader 400 to the measurement space 212 to initiate the spreader measurement process, for example when the second apparatus 200 detects the load and/or the spreader 400 in the measurement space 212. The measurement space 212 may be fixed and its coordinates in the block coordinate system can be used by the system 100, for example by the first apparatus 250 and/or the second apparatus 200. This allows, for example, the crane 10 to automatically move the spreader 400 and/or the load 20 to the measurement space 212. One or more lanes 40, 42 may be associated with their own measurement space 212 to allow the spreader 400 and/or the load 20 to be moved to the measurement space 212 of the lane 40, 42 automatically. The measurement space 212 may be located above the location where a vehicle 30, 34 is to be stopped for loading/unloading but it may also be located on the side of that location. The movement of the spreader 400 in the measurement space 212 may be slowed down or stopped to allow detection of the spreader 400 by the second apparatus 200. The measurement space 212 may be one, two or three dimensional space. For example, the measurement space 212 may comprise one or more of the following: a target measurement position for the spreader, a target altitude of the spreader, a threshold for maximum altitude of the spreader and a threshold for minimum altitude of the spreader. Alternatively or additionally, the measurement space 212 may comprise a two- or three-dimensional measurement window for the spreader 400. The system 100 and/or the second apparatus 200 may be arranged to continue the spreader measurement process, with repeated and/or continuous measurement, once it has been initiated. This way, the measurements provided by the second apparatus 200 can be used for providing feedback to the first apparatus 250 controlling the movement of the spreader 400. The spreader 400 may be lowered to the measurement space 212 from above. This allows the spreader 400 to safely approach the vehicle 30, 34.

[0062] The position control information provided by the second apparatus 250 can be transmitted to the first apparatus 200 directly. Alternatively or in addition, the system 100 may comprise one or more mediators 150 such as communication equipment and/or computing servers through which the position control information can be transmitted. For example, the system 100 may comprise one or more monitoring centers located inside or outside the terminal for this purpose. The one or more mediators 150 may comprise one or more computing servers, which may be arranged to monitor and/or control one or more cranes 10. The one or more mediators 150 may be arranged for automated loading/unloading with the crane 10. The one or more mediators 150 may be arranged to perform some or all of the processing for determining control instructions for moving the spreader 400 to the spreader target position. However, any combination of the mediator system 100, first apparatus 250 or second apparatus 200 can be arranged to determine the spreader target position based on the loading/unloading target position 32, 36 determined by the second apparatus 200. Moreover, any combination of the mediator system 100, first apparatus 250 or second apparatus 200 can be arranged to determine instructions for moving the spreader 400 to the spreader target position or towards the spreader target position, based on the loading/unloading target position 32, 36 and the position of the spreader 400 determined by the second apparatus 200.

[0063] FIG. 2 illustrates a block diagram of a system 100 according to an embodiment. The system 100 comprises a first apparatus 250 and a second apparatus 200. The system 100 may also comprise one or more mediators 150.

[0064] The first apparatus 250 comprises a receiver 270 for receiving position control information, which receiver 270 can also be a transmitter-receiver. The receiver 270 can be arranged for wireless or wired transfer of information. The first apparatus 250 also comprises a controller for controlling the movement of the spreader 400. The first apparatus 250 may also comprise one or more sensors 272. The one or more sensors 272 may be arranged, for example for determining the position and/or orientation of the spreader 400. In particular, the one or more sensors may comprise one or more inclination sensors for determining the inclination of the spreader 400 and/or the headblock 510. The one or more inclination sensors may be arranged to be installed in the spreader 400 and/or the headblock 510. The inclination may be determined with respect to one or more axes. Alternatively or additively, the one or more sensors 272 may be arranged to determine the position and/or orientation of the crane 10, for example that of the gantry and/or the bridge. The first apparatus 250 may further comprise a memory 280, which may comprise program instructions for controlling the operation of the crane 10, e.g. the movement of the spreader 400. For example, an operating system 282 and/or application software 284 for operating the crane 10 can be stored in the memory 280.

[0065] The second apparatus 200 comprises a transmitter 220 for transmitting position control information, which transmitter 220 can also be a transmitter-receiver. The transmitter 220 can be arranged for wireless or wired transfer of information.

[0066] The second apparatus 200 also comprises one or more detectors 222 for measuring distance. The one or more detectors 222 may comprise a two- or three-dimensional laser scanner. Alternatively or additionally, the one or more detectors 222 may comprise, for example, one or more optical detectors and/or pattern recognition devices. The one or more detectors 222 are arranged so that they can be used by the apparatus 200 to measure the distance to the loading/unloading target position 32, 36 for determining the loading/unloading target position 32, 36 in a fixed coordinate system. The one or more detectors 222 are also arranged so that they can be used by the apparatus 200 to measure the distance to the position of the spreader 400 in the fixed coordinate system for determining the position of the spreader 400 in a fixed coordinate system. In either or both cases, measuring the distance may actually comprise multiple measurements and/or multiple different distances measured with respect to different points of the target to be measured. At least one detector 222, such as a laser scanner, can be arranged for determination of both the loading/unloading target position 32, 36 and the position of the spreader 400 in a fixed coordinate system. The detector 222 may be arranged to do this with fixed orientation.

[0067] The one or more detectors 222 can be arranged to be installed in the crane 10 and/or in terminal infrastructure. The one or more detectors 222 can be installed at an elevated position to extend the field of view 210 across the one or more lanes 40, 42, even across all the lanes 40, 42 of the loading/unloading area. For example, the one or more detectors 222 may be arranged to be installed at an elevation of 4-5 meters or more, for example at an elevation of 6-8 meters or even more. As an example of installation in the crane 10, some or all of the one or more detectors 222 can be arranged to be installed at one or both sides of the crane 10, e.g. at a vertical leg of the crane 10 or the gantry of the crane 10. As an example of installation in terminal infrastructure, some or all of the one or more detectors 222 can be arranged to be installed at a post or a pole but also atop a building or some other elevated structure. In terminal infrastructure, the one or more detectors 222 may be arranged to be installed in a stationary position. The field-of-view 210 of the second apparatus 200 can be covered with one detector 222 and/or with multiple detectors 222. For example, at least one 222 may be arranged to monitor one or more lanes 40, 42, even all the lanes of a loading/unloading area for providing position control information. Conversely, when the loading/unloading area has multiple lanes 40, 42, one or more lanes 40, 42, even all the lanes, may have a separate detector 222 arranged to monitor the lane for providing position control information. The one or more detectors 222 may be arranged to face downwards and/or substantially horizontally. For example, the one or more detectors 222 may be arranged so that their field-of-view 210 extends at most 0-10 degrees above the horizontal level. The one or more detectors 222 may be arranged to be positioned on the altitude of the measure space 212 and/or above it. For example, the one or more detectors 222 may be arranged to be positioned on the altitude of the measurement space 212 or at most 1-2 meters above the measurement space 212.

[0068] The second apparatus 200 may comprise a processor 224. The processor 224 may be arranged to process the position control information before it is transmitted by the transmitter 220 of the second apparatus 200. For example, the processor 224 may be arranged to determine the loading/unloading target position 32, 36 based on the measured distance to the loading/unloading target position 32, 36. Alternatively or additionally, the processor 224 may be arranged to determine the position of the spreader 400 based on the measured distance to the position of the spreader 400 400. As one further example, the processor 224 may be arranged to determine the spreader target position based on the position of the spreader and the loading/unloading target position 32, 36 determined by the apparatus 200. The second apparatus 250 may further comprise a memory 230, which may comprise program instructions for controlling the operation of the second apparatus 200. For example, an operating system 232 and/or application software 234 for operating the crane 10 can be stored in the memory 230.

[0069] The first apparatus 250 and the second apparatus 200 may be arranged to communicate directly 110 and/or indirectly 112 through one or more mediators 150. The first apparatus 250 and the second apparatus 200 may be arranged to communicate only in one direction so that position control information is transmitted from the second apparatus 200 to the first apparatus 250.

[0070] However, it is also possible for the second apparatus 200 to be arranged to receive information such as crane position information, for example from the first apparatus 250 and/or the mediator 150. Correspondingly, the first apparatus 250 may also comprise a transmitter and, alternatively or additionally, the second apparatus 200 may also comprise a receiver.

[0071] FIG. 3 illustrates a flow diagram of a method according to an embodiment. The method comprises measuring 310, for example by an apparatus such as the second apparatus 200, the distance to the loading/unloading target position 32, 36 for determining the loading/unloading target position 32, 36 in a fixed coordinate system. Based on the determined loading/unloading target position 32, 36 the crane 10 can be positioned 330 for loading/unloading, for example by the system 100 or, specifically, by an apparatus such as the first apparatus 100. This may involve moving the gantry and/or trolley 12 of the crane 10 in position. The alignment process may be arranged so that after positioning 330 of the crane 10, the spreader 400 is above the loading/unloading target position 32, 36.

[0072] The method also comprises measuring 350, by the same apparatus as in the measurement for the loading/unloading target position 32, 36, the distance to the position of the spreader 400 for determining the position of the spreader 400 in the same fixed coordinate system. The loading/unloading target position 32, 36 may be determined before the position of the spreader 400 is measured 350. This allows the presence and location of the target, e.g. a vehicle 30, 34 and/or a load 20, to be determined before the spreader 400, which may have a load 20 coupled to it, is moved 340 close to the area where the loading/unloading is to take place. For measuring 350 the position of the spreader 400, the spreader 400 is moved 340, e.g. lowered, towards the loading/unloading target position 32, 36. At this point the loading/unloading target position 32, 36 may have been already determined 310 but it need not necessarily have been, since the position where the loading/unloading takes place is typically known and therefore a coarse approximate of the loading/unloading target position 32, 36 can be used at least in some situations. When the spreader 400 is in the field-of-view 210 of the apparatus 200, its position can be measure 350 by the apparatus 200. For this purpose the spreader 400 can be moved, e.g. lowered, to a measurement space 212. When the spreader 400 is in the measurement space 212 or approaches the measurement space 212, its movement may be slowed down or stopped for measurement of its position 400. The position of the spreader 400 and/or the loading/unloading target position 32, 36 can be determined repeatedly. Alternatively or additionally, either or both of them, in particular the position of the spreader 400, can even be determined continuously. This way, the apparatus 200 can be arranged to provide feedback for moving the spreader 400 towards the spreader target position.

[0073] To provide the position control information for moving 370 the spreader 400 towards the spreader target position, the method comprises causing 320, 360 position control information corresponding to the loading/unloading target position 32, 36 and the position of the spreader 400 to be transmitted to a crane 10.

[0074] The position control information can be transmitted to the crane 10 repeatedly or continuously, for example at least until the spreader 400 is positioned at the spreader target position. The position control information can be transmitted by an apparatus such as the second apparatus 200 and it can be transmitted to the crane 10 either directly from the apparatus or indirectly through one or more mediators 150. Position control information corresponding to the position of the spreader 400 and position control information corresponding to the loading/unloading target position 32, 36 may be transmitted simultaneously or separately.

[0075] By using position control information corresponding to both the loading/unloading target position 32, 36 and the position of the spreader 400, the spreader can be moved 370 towards the spreader target position. The whole process including measuring 310, 350 the loading/unloading target position 32, 36 and the position of the spreader 400, causing 320, 360 position control information to be transmitted to the crane 10 and using 370 position control information to move the spreader 400 towards the spreader target position can be arranged to be performed in an automated sequence. The automated sequence may continue at least until the spreader 400 has been moved to the spreader target position or until one or more interruption conditions, such as emergency stop conditions has been met. Each of the system 100, the first apparatus 250 and the second apparatus 200, may be arranged to cause the automated sequence to be performed.

[0076] After the loading/unloading target position 32, 36 has been determined and the crane 10 has been moved into position for loading/unloading, the spreader 400 can potentially be moved to the spreader target position by spreader movements only, for example using only so-called spreader micromovements. For this purpose, the spreader 400, including parts of the spreader arranged to hold the load, may be arranged to be able to move laterally while the trolley 12 remains stationary. This means that no movement of the crane 10 or the trolley 12 is necessary to move the spreader 400. In one example, the spreader 400 may be arranged for maximal lateral movement of 400-600 millimeters in one or more dimensions, i.e. the maximal lateral movement being+/200-300 from a center point. With advances of technology, it should be understood that the maximal lateral movement may also be higher. When the spreader 400 is connected to a headblock 510, either or both the spreader 400 and the headblock 510 may be arranged to facilitate the movements of the spreader to allow the spreader 400 to be moved independently, i.e. with the trolley 400 and the crane 10 remaining stationary. Correspondingly, the spreader measurement process described above can be adapted for positioning of the spreader 400 so that only spreader movements are required.

[0077] As one example, a system for providing position control information for controlling the movement of a spreader of a crane towards a spreader target position can be implemented as a Truck Lane Measurement System (TLMS). The system comprises at least one detector, which can be installed in terminal infrastructure. At first, the system is used to determine a position of a container on a vehicle, e.g. on a trailer, or a loading target position for placing a container on a vehicle, e.g. on a trailer. The system can also be used to measure reference objects installed in the spreader and/or a headblock of the crane, and to determine the spreader position while lowering the spreader or the container. While the spreader is lowered towards the vehicle, the system can provide feedback for the crane, indicating how the spreader must be controlled in order to get the spreader close to the container on the vehicle or the spreader target position for releasing the container on the vehicle.

[0078] The measurement procedure may comprise some or all of the following steps. First, the vehicle can be measured with one or more detectors of the system to get sufficient amount of measurement data to create a 3D point cloud of vehicle shapes, which may including twistlocks, and/or one or more containers on the vehicle. Second, the measurement data can be processed by the system to detect the positions of container edges and/or target twistlocks in order to determine the container position or a loading target position on the vehicle. Third, the crane's gantry and/or trolley can be driven to the assumed target position. Fourth, the spreader can be lowered to a safe height where the detector of the system is able to detect the spreader, e.g. from reference objects in the spreader and/or headblock. Fifth, the spreader speed may be lowered in order to get sufficient amount of measurement data for the system to determine the spreader position. Sixth, the system can use the position of the spreader to calculate the spreader movements needed in order to control the spreader towards the target. Seventh, while lowering the spreader, feedback of the system can be used to control the spreader.

[0079] FIG. 4 illustrates a spreader 400 according to an embodiment in a side view (left) and an overhead view (right). The spreader 400 comprises a body 410, which may comprise one or more horizontally extending beams for carrying a load 20. The spreader 400 may comprise one or more markers 420, 422, which may be used as reference features for determining the position of the spreader 400. As an example, the spreader 400 may comprise one or more markers 420, 422 at its front edge 412 and/or one or more markers at its rear edge 414. Similarly, to improve detection, the spreader 400 may comprise one or more markers 422 at each of its side edges 416. The one or more markers 420, 422 may be arranged to be identifiable by the second apparatus 200, for example by their color and/or shape. Conversely, the second apparatus 200 may be arranged to identify the one or more markers 420, 422 for determining the position of the spreader 400.

[0080] FIG. 5 illustrates providing position control information according to an embodiment. While various features described above are illustrated in the FIG. with corresponding reference numbers, these features are optional unless otherwise stated.

[0081] Importantly, it has been found that position control for the spreader 400 can be markedly improved by calibrating the determination for the distance to the position of the spreader 400 by using an additional measurement for the distance to the position of the spreader 400 during a crane ground job, i.e. when the spreader 400 is coupled to a load 20, such as a container, for loading/unloading and the load 20 is positioned at the loading/unloading target position 32, 36. The additional measurement can be used as a calibration measurement. The additional measurement and/or the determination may be performed automatically. The additional measurement may be performed once it has been determined that the spreader 400 is coupled to the load 20 for loading/unloading and that the load 20 is at the loading/unloading target position, for example at rest on a vehicle 30, 34 and/or a loading/unloading platform. This determination may be performed partially or fully automatically, for example by the second apparatus 200 and/or by one or more parts of the system 100. The additional measurement and/or the determination may be performed repeatedly, for example once or more during for each ground job.

[0082] The additional measurement and/or the determination may be performed, for example, once the load 20 has been successfully positioned at the loading/unloading target position 32, 36.

[0083] Since the load 20 is on the loading/unloading target position 32, 36, the position of the spreader 400 determined from the additional measurement (hereafter also spreader reference position) should ideally correspond to the position of the spreader 400 determined from the measurement for the distance to the loading/unloading target position (hereafter also load-based spreader position). Here, the load-based spreader position may be determined based on the loading/unloading target position 32, 36 and the height of the load 20. However, since the measurement for the distance to the position of the spreader 400 and the measurement for the distance to the loading/unloading target position 32, 36 are different measurements, measurement bias typically arises. This bias can now be determined and compensated for a following loading/unloading operation. In short, a difference between the spreader reference position and the load-based spreader position can be determined and the difference may be used for compensating any following determination for the position of the spreader 400. For example, the difference may be partially or fully add-ed into any determined position of the spreader 400. The difference in position may be determined for one or more variables such as the one or more horizontal position components and/or skew. One or more previous differences may be used for determining a compensated position of the spreader 400. For example, an average of two or more previous difference may be determined and used for compensation. Using a bias memory comprising at least one previous difference whose validi-ty has been confirmed and/or two or more previous differences may be used to improve the robustness of bias determination with respect to temporary malfunction and/or sporadic errors in measurements.

[0084] The system 100 and/or the second apparatus 200 may be arranged to determine whether calibration can be performed. In particular, it has been found that the ability of the system 100 to detect the spreader 400 may be improved by increasing the detector angle 520 for the one or more detectors 222 with respect to vertical direction. The detector angle 520 may be defined, for example, as corresponding to the angle between the vertical direction and the viewing direction, or a limit thereof, of the one or more detectors 222. A minimum detector angle may be used as a threshold for performing the calibration. The system 100 and/or the second apparatus 200 may be arranged to determine whether the detector angle 520 is equal or larger than a threshold angle. The additional measurement and/or the calibration can be conditional on the detector angle 520 being equal or larger than a threshold angle. The detector angle 520 may depend on any combination of the height at which the one or more detectors 222 are mounted, the height of the load 20, the height of the loading/unloading target position 32, 36, e.g. the height of a vehicle 30, 34 or its trailer, and the horizontal coordinates of the loading/unloading target position 32, 36, e.g. the horizontal position of a vehicle 30, 34 or its trailer. As an example, the detector angle 520 may become smaller when any of the following conditions is satisfied: the loading/unloading target position 32, 36 is low, the height of the load 20 is small and the loading/unloading target position 32, 36 is horizontally close to the one or more detectors 222. Higher loading/unloading target position 32, 36, larger height of the load 20 or horizontally increased distance between the loading/unloading target position 32, 36 and the one or more detectors 222 may be used to increase the detector angle 520.

[0085] The system 100 can be implemented as TLMS, also for calibration. As an example of a calibration process sequence, in a truck lane ground job, when the crane has lowered the container successfully on the trailer, an indication can be caused to be transmitted to the system, for example by a programmable logic controller (PLC), that the load is in loading/unloading target position. Similarly, spreader position information may be transmitted. The system may be arranged to always control the detector(s) to follow the spreader until the very end of the grounding of the load. When the system receives the indication, the system can evaluate if the spreader is in such a position, relative to detector(s) of the system, that calibration is possible. If it is, the system can measure spreader reference object(s) and determine the position of the spreader (e.g. x-coordinate, y-coordinate and/or skew: denoted here x.sub.1, y.sub.1, s.sub.1, respectively). Then, the system can take the previous ground job measurement re-sult from its memory (x.sub.0, y.sub.0, s.sub.0). The system can also calculate the bias of spreader measurement, compared to the ground job measurement (x.sub.bias=x.sub.1-x.sub.0, y.sub.bias=y.sub.1-y.sub.0, s.sub.bias=s.sub.1-s.sub.0). The system can then start to compensate its bias in the following spreader measurements (x.sub.compensated=x.sub.measuredx.sub.bias, y.sub.compensated=y.sub.measuredy.sub.bias, s.sub.compensated=s.sub.measureds.sub.bias).

[0086] Any apparatus and/or the system may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The application logic, software or instruction set may be maintained on any one of various conventional comput-er-readable media. A computer-readable medium may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A com-puter-readable medium may comprise a computer-readable storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The exemplary embodiments can store information relating to various processes described herein. This information can be stored in one or more memories, such as a hard disk, optical disk, magneto-optical disk, RAM, and the like. One or more databases can store the information used to implement the exemplary embodiments of the present inventions. The databases can be organized using data structures (e.g., records, tables, arrays, fields, graphs, trees, lists, and the like) included in one or more memories or storage devices listed herein. The databases may be located on one or more devices comprising local and/or remote devices such as servers. The processes described with respect to the exemplary embodiments can include appropriate data structures for storing data collected and/or generated by the processes of the devices and subsystems of the exemplary embodiments in one or more databases.

[0087] All or a portion of the exemplary embodiments can be implemented using one or more general purpose processors, microprocessors, digital signal processors, mi-cro-controllers, and the like, programmed according to the teachings of the exemplary embodiments, as will be appreciated by those skilled in the computer and/or software art(s). Appropriate software can be readily prepared by programmers of ordinary skill based on the teachings of the exemplary embodiments, as will be appreciated by those skilled in the software art. In addition, the exemplary embodiments can be implemented by the preparation of application-specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be appreciated by those skilled in the electrical art(s). Thus, the exemplary embodiments are not limited to any specific combination of hardware and/or software.

[0088] The different functions discussed herein may be performed in a different order and/or concurrently with each other.

[0089] Any range or device value given herein may be extended or altered without losing the effect sought, unless indicated otherwise. Also any embodiment may be combined with another embodiment unless explicitly disallowed.

[0090] Although the subject matter has been described in lan-guage specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0091] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to an item may refer to one or more of those items.

[0092] The term comprising is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0093] It will be understood that the above description is given by way of example only and that various modifi-cations may be made by those skilled in the art. The above specification, examples and data provide a com-plete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make nu-merous alterations to the disclosed embodiments without departing from the spirit or scope of this specification.