EP0668237A1 - Method for handling a load with a crane - Google Patents

Abstract

To move a load by means of a crane from a start position to a target position, the instantaneous position is continuously assessed and compared with the target position. The target position is assumed to lie within a range e.g. when goods are stacked in layers of several units wide and when the load approaches the general target area, a more exact assessment is made between the instantaneous position and the actual position within the stack where the load is to be placed. The position measurements are made using optical sensors pointing downwards from the grab and they detect the outside edges of the load.

Description

The invention relates to a method for conveying a load by means of a crane, the load being picked up at a starting position, conveyed over a distance to a destination and deposited there.

Cranes, such as B. container cranes are used to pick up loads at a predetermined location, to promote them over a known route and to drop them at a specified destination, such as a destination container. The problem arises in practice that the exact actual position of the target is not known for the conveyance of the load in the direction of the target. Instead, a target position of the target is known, which can be defined, for example, by the center of a predetermined target area.

The invention is based on the object of automating the conveying of the load from the starting position to the target, it being possible for the load to be positioned precisely on the target.

According to the invention, the object is achieved in that in the method of the type specified above, the actual position of the load is detected by means of a path detection device and is fed to a path control which is a function of the difference between the detected actual position of the load and a predetermined target position of the target controls the conveyance of the load in the direction of the target, and that in the vicinity of the target, the actual position of the load and the actual position of the target are detected relative to one another by means of a sensor device and are fed to the path control, which is a function of the difference between the actual position of the load and the Actual position of the target controls the positioning of the load on the target, and when the load approaches the target, the different position variables supplied to the path control are blended.

When the load is conveyed in the direction of the target, the actual position of the load is preferably detected by means of a path measuring device which continuously measures the position of a cat on which the load is attached. The displacement measuring device can be, for example, a displacement sensor or a laser distance measuring device that measures the distance between the cat and a fixed reference position.

A more precise determination of the actual position of the load is achieved by additionally measuring the pendulum angle of the load and using it together with the measured position of the trolley to calculate the actual position of the load. On the basis of the actual position of the load measured in this way, it is possible for the path control to regulate the conveyance of the load in such a way that oscillations of the load are largely avoided during the conveyance and in particular when arriving at the target position of the destination. The measurement of the pendulum angle of the load can, for example, by an optical scanner, such as. B. a camera or preferably laser distance profile measuring devices, which is arranged on the cat and scans the outer edges of the load in a scanning angle range open downwards.

In a particularly simple manner and with the achievement of particularly short measuring times, the pendulum angle of the load is measured in that a marking with a reflecting surface is arranged in the area of the load, that on the crane a lighting device directed at the marking and also a line camera also directed at the marking an image sensor line aligned along the pendulum direction is arranged and that in an evaluation device arranged downstream of the image sensor line, an output signal corresponding to the current position of the marking is generated from the signal of the image sensor line. This measuring principle can be used alone or together with the measurement by the laser distance profile measuring devices mentioned. The measurement of the pendulum angle with the aid of laser distance profile measuring devices and / or line scan cameras is explained in detail in European patent application 93 11 6998.1.

When the load approaches the target, the position variables supplied to the position control are faded from the measured actual position of the load and the target position of the target to the actual position of the load and the actual position of the target detected by the sensor device. The crossfading prevents a sudden change in the variables given to the displacement control, so that jerky load movements are prevented.

The crossfade is preferably triggered by the sensor device. This can comprise an optical scanning device, which is arranged in the region of the crane and scans the outer edges of the load and the surrounding area of the load in a scanning angle range which is open downwards, the optical scanning device being a camera or preferably a laser distance profile measuring device acts. The cross-fading between the different position variables supplied to the displacement control takes place when the sensor device detects the load and the target at the same time. After the cross-fading, the precise placement of the load on the target is then regulated as a function of the difference between the actual positions of the load and the target determined by the sensor device.

As an alternative to the arrangement of the scanning device forming the sensor device on the crane, it can also be arranged in the area of the load and in a scan opened downwards scan the area around the load. In this case, the fade is triggered as soon as the target is detected by the scanner. Since the scanner is arranged in the area of the load, it automatically detects the position of the target relative to the current position of the load. Such a scanning device arranged in the area of the load is explained in detail in European patent application 93 10 9943.6.

• FIG 1 den prinzipiellen Ablauf der Förderung einer Last mittels eines Containerkrans von einer Startposition zu einer Zielposition,
• FIG 2 einen die Last transportierenden Containerkran, dessen Laufkatze mit Laser-Entfernungsprofilmeßgeräten und einer Zeilenkamera bestückt ist,
• FIG 3 eine Draufsicht auf die Last,
• FIG 4 einen Containerkran zum Transport einer an einem Lastaufnahmerahmen hängenden Last mit einer an dem Containerkran angeordneten Zeilenkamera und mit Laser-Entfernungsprofilmeßgerätenan dem Lastaufnahmerahmen und
• FIG 5 das Blockschaltbild einer Steuerungsstruktur für den Containerkran.

For a more detailed explanation of the invention reference is made below to the drawings of the figure; show in detail

• 1 shows the basic sequence of conveying a load by means of a container crane from a starting position to a target position,
• 2 shows a container crane carrying the load, the trolley of which is equipped with laser distance profile measuring devices and a line scan camera,
• 3 shows a plan view of the load,
• 4 shows a container crane for transporting a load hanging on a load-bearing frame with a line camera arranged on the container crane and with laser distance profile measuring devices on the load-bearing frame and
• 5 shows the block diagram of a control structure for the container crane.

1 schematically shows a trolley 1 which can be moved on a jib 2 of a container crane, not shown here, and on which a load 3, here a container, hangs. As shown in the individual phases in FIG. 1, this load 3 is to be picked up at the starting position xo and conveyed over a certain distance to a target position x _z and placed there on a target container 4. However, the actual actual position x _{z of} the target 4 is not known, but only a target position x _z ^* , which is defined, for example, as the center of a target area Ax _z ^* . When the load 3 is conveyed from the start position xo to the target 4, as will be explained later, the actual position _{XL of} the load 3 is continuously measured and compared with the target position x _z ^{* of} the target 4. The actual position x _K of the trolley 1 and the current pendulum angle 4) L of the load 3 are continuously measured and the actual position _{XL of} the load 3 is determined from them. Depending on the difference between the actual position _{XL of} the load 3 and the target position x _z ^{* of} the target 4, the trolley 1 is moved towards the target 4 by rapid control. In this case, the cat 1 is moved along the boom 2, for example, with the travel speed denoted by v _K , so that pendulum movements of the load 3 are largely avoided, in particular when the target 4 is reached. If the load 3 is in the vicinity of the target 4, as will be explained later, the actual position _{XL of} the load 3 and the actual position x _{z of} the target 4 relative to one another are detected by means of a sensor device, and the deposition of the load 3 as a function thereof controlled on target 4.

2 schematically shows the jib 2 with the cat 1 which can be moved thereon in the region of the target container 4. Lifting winches 5 are arranged on the cat 1, on which a load-carrying frame (spreader) 7 for the load 3 to be transported hangs via cables 6. The load 3 is to be placed precisely on the target container 4 which has already been parked. By starting and braking the cat 1 but also by external interference, such as. B. wind forces, the load 3 can be made to oscillate. In the following it is assumed that oscillations of the load 3 take place essentially in the direction of travel x of the trolley 1, with additional oscillations of the load 3 occurring.

To detect the actual position x _{K of} the cat 1, a laser distance measuring device 8 is arranged on it, which measures in the direction of travel x of the cat 1 to a fixed reference position 9 in the form of a reflection mark.

In order to be able to measure the current actual position _{XL of} the load 3 both in relation to the trolley 1 and in relation to the surroundings of the load 3 (target container 4), two scanning devices in the form of laser distance profile measuring devices 10 and 11 are on the trolley 1 Arranged over the two outer edges 12 and 13 of the load-bearing frame 7 which run transversely to the direction of travel x of the cat 1. Each of the two laser distance profile measuring devices 10 and 11 generates a laser beam 14 and 15, respectively, which is deflected in a scanning angle range which is open along the pendulum direction x and the outer edge 12 and 13 perpendicular to the respective laser distance profile measuring device 10 and 11, respectively. In FIG 1, those points on the load-bearing frame 7 or the load 3 and their surroundings, on which the laser beams 14 and 15 impinge, are highlighted by a thicker line width. By evaluating the propagation time of the laser light and the respective instantaneous radiation angle of the laser beam 14 or 15, the position coordinates in the horizontal x-direction and the vertical y-direction can be determined for each point which the laser beam 14 or 15 strikes. While the load 3 is being conveyed from the start position xo (FIG. 1) in the direction of the target container 4, the current pendulum angle φ _{L of} the load 3 is determined with the aid of the two laser distance profile measuring devices 10 and 11 and together with that by the laser distance measuring device 8 specific actual positions tion x _{K of} the cat 1 used to determine the actual position _{XL of} the load 3. As has already been explained with reference to FIG. 1, the actual position _{XL of} the load 3 obtained in this way is compared with the target position x _z ^{* of} the target 4 and the trolley 1 is moved as a function of the comparison result.

As FIG 2 shows, the laser beams 14 and 15 also detect areas of the target container 4 when the load 3 approaches the target container 4. If the target container 4 is identified in this way, the path control for the trolley 1 is no longer dependent on the means of the laser distance measuring device 8 and the two laser distance profile measuring devices 10 and 11 ascertained the actual position _{XL of} the load 3 and the target position x _z ^{* of} the target 4, but instead the position deviation between the load 3 determined by the two laser distance profile measuring devices 10 and 11 and the target container 4 used for further displacement control of the trolley 1. As long as the load 3 is not positioned exactly above the target container 4, the laser beams 14 and 15 also detect areas of the target container 4. As soon as both laser beams 14 and 15 no longer strike the target container 4, the load 3 is positioned directly above the target container 4 and can be lowered onto this.

The optimal position of the two laser distance profile measuring devices 10 and 11 in the x-direction is not directly above the respective outer edges 12 or 13 of the load-bearing frame 7, but somewhat outside thereof, so that there is none for the laser beams 14 and 15 below the outer edges 12 and 13 inaccessible blind spot. As the top view of the load-bearing frame 7 according to FIG. 3 shows, the two laser distance profile measuring devices 10 and 11 with their scanning angle ranges 14 and 15 are also arranged offset with respect to the x direction, that is to say offset in the z direction. This makes it possible to measure not only pendulum movements in the x-direction but also rotary oscillations of the load, which manifest themselves in the fact that the x-coordinates of the outer edges 12 and 13 measured with the laser beams 14 and 15 change differently. Since containers can have different constructions, the outer edges 12 and 13 can be scanned most safely in the area of the corner fittings of container 4 that are the same for all containers. Since containers can also have different lengths, the two laser distance profile measuring devices 10 and 11 are arranged on the trolley 1 so as to be displaceable in the z direction.

To detect the pendulum angle of the load, i.e. the position of the load 3 in relation to the trolley 1, a mark 16 is provided on the load-bearing frame 7 in addition to the two laser distance profile measuring devices 10 and 11, which is vertically moved over by one when the load 3 is at rest this headlight 17 held on the cat 1 is illuminated, the light reflected by the marking 16 being captured by a line camera 18 arranged directly next to or in the headlight 15. The marking 16 consists of a rectangular reflecting surface with an edge side parallel to the pendulum direction x, which is surrounded by a non-reflecting surface 19. The reflecting surface 16 consists of a multiplicity of triple reflector elements, not shown here, which radiate light incident on them in the direction from which it came. This ensures that the light emitted by the headlight 17 is reflected back from the reflecting surface 16 into the line camera 18 directly adjacent to the headlight 17, regardless of the respective amount of the pendulum deflection x. The line camera 16 is arranged on the trolley 1 in such a way that its scanning plane 20 intersects the marking 16 along the pendulum direction x. To detect the position of the marking 16, the serial output signal of the line camera 18 is searched with the greatest contrast in each case after the occurrence of the two brightness changes, and in this way the edges of the reflecting surface 16 running transverse to the scanning direction 20 are detected. The position of the center of the marking 16 is determined from the center between the two detected changes in brightness and is made available to the line camera 18 as the output signal. In contrast to the two laser distance profile measuring devices 10 and 11, the measurements with the line camera 18 result in considerably shorter measuring times, which is advantageous for the regulation of load oscillations and for the load positioning regulation.

In the exemplary embodiment of the container crane shown in FIG. 4, in contrast to the exemplary embodiment according to FIG. 2, no laser distance profile measuring devices are provided on the trolley 1, but instead two, but preferably four, laser distance profile measuring devices 21 and 22 are arranged on the load-bearing frame 7. Each of the laser distance profile measuring devices 21, 22 each generates a laser beam which is deflected in a predetermined scanning angle range. In the area of the outer edges of the load-bearing frame 7, devices 23, 24 for beam deflection are each arranged in such a way that the laser distance profile measuring device, for. B. 21, generated and deflected in the predetermined scanning angle range in the downward direction past the load-bearing frame 7 and the load 3 and thereby the environment of the load-bearing frame 7 and the load 3 in a perpendicular to The course of the assigned outer edge 12 or 13 of the load-bearing frame 7 scans the open angle region 25. Those points where the laser beam deflected in the angular region 25 are highlighted by a thicker line width. By evaluating the transit time of the laser light and the respective instantaneous radiation angle of the laser beam, the position coordinates in the horizontal x-direction and the vertical y-direction can be determined for each point that the laser beam strikes. In this way, the actual position x _{z of} the target container 4 in relation to the actual position _{XL of} the load 3, ie the difference between these two actual positions x _z and _{XL, is} determined by means of the laser distance profile measuring devices 21 and 22.

For the rest, the embodiment of FIG 4 does not differ from that of FIG 2, so that the same parts are also provided with the same reference numerals.

5 shows a simplified block diagram of a control structure for carrying out the method according to the invention. Based on the exemplary embodiment according to FIG. 2, the actual position _{XL of} the load 3 is continuously measured by means of the laser distance measuring device 8 and the two laser distance profile measuring devices 10 and 11 when the load 3 is conveyed from the starting position xo to the destination 4. The difference between the measured actual position _{XL of} the load 3 and the predetermined target position x _z ^{* of} the target 4 is formed in a subtracting node 26 and fed via a controllable switching device 27 to a path control 28 which, depending on the determined difference, drives a drive 29 for moving the Trolley 1 controls. As soon as the load 3 approaches the target 4 so far that it is detected by the laser distance profile measuring devices 10 and 11, the switching device 27 is activated so that now the difference between the actual position _XL measured by the two laser distance profile measuring devices 10 and 11 the load 3 and the actual position x _{z of} the target 4 of the path control 28 is supplied. So that there are no abrupt changes in the control process during the switchover, the input variables supplied immediately before and immediately after the switchover of the position control 28 are temporarily stored in a memory 30 and subtracted from one another. The difference obtained in this way is fed to the input of the displacement control 28 via a device 31 and is added there with a negative sign to the input signal for the displacement control 28 coming from the switching device 27. As a result, the input variable for the position control 28 does not change immediately after the switchover. Within the device 31, the difference formed in the storage device 30 is reduced within a predetermined time interval to the value zero, so that after this time interval the input variable x _Z -x _{L is} fed to the position control 28. In this way, there is a crossfade between the input variables x _Z * -x _L and x _Z -x _L.

The reference numerals given in brackets in FIG. 5 refer to the exemplary embodiment according to FIG. 4.

Claims (7)

1. Method for conveying a load (3) by means of a crane, the load (3) being picked up at a starting position (xo), conveyed over a distance to a destination (4) and deposited there,
characterized,
that the actual position ( _XL ) of the load (3) is detected by means of a path detection device (8, 10, 11, 18) and is fed to a path control (28) which, depending on the difference between the detected actual position (x _L ) of the load (3) and a predetermined target position (x _z ^* ) of the target (4) controls the conveyance of the load (3) towards the target (4), and that in the vicinity of the target by means of a sensor device (10, 11; 21, 22) the actual position (x _L ) of the load (3) and the actual position (x _z ) of the target (4) relative to each other are detected and fed to the path control (28), which is a function of the difference between the actual position ( _XL ) of the load (3) and the actual position (x _z ) of the target (4) controls the positioning of the load (3) on the target (4), whereby when the load (3) approaches the target (4) between the different, the path control (28) supplied position sizes is faded. 2. The method according to claim 1,
characterized,
that when conveying the load (3) towards the target (4) the actual position ( _XL ) of the load (3) is detected by means of a path measuring device (8) which continuously measures the position of a cat (1) at which the Load (3) hangs. 3. The method according to claim 2,
characterized,
that in addition the pendulum angle (φ) of the load (3) is measured and together with the measured position ( _XK ) of the trolley (1) is used to calculate the actual position ( _XL ) of the load (3). 4. The method according to claim 3,
characterized,
that a mark in the area of the load (3) (16) with a reflecting surface is arranged on the crane, a lighting device (17) directed at the marking (16) and a line camera (18) also directed at the marking (16) with an image sensor line aligned along the pendulum direction (x) and that in an evaluation device arranged downstream of the image sensor line (18), an output signal corresponding to the current position of the marking (16) is generated from the signal of the image sensor line. 5. The method according to any one of the preceding claims,
characterized,
that the cross-fading between the different position variables supplied to the path control (28) is triggered by the sensor device (10, 11; 21, 22). 6. The method according to any one of the preceding claims,
characterized,
that the sensor device comprises an optical scanning device (10, 11) which is arranged in the region of the crane and in a scanning angle range (14, 15) which is open at the bottom, the outer edges (12, 13) of the load (3) and the area surrounding the load (3) scans. 7. The method according to any one of claims 1 to 5,
characterized,
that the sensor device comprises an optical scanning device (21, 22) which is arranged in the region of the load (3) and scans the surroundings of the load (3) in a scanning angle region (25) which is open at the bottom.

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