EP0668237B1 - Method for handling a load with a crane - Google Patents

Description

The invention relates to a method for conveying a load by means of a crane according to the preamble of claim 1.

Cranes, e.g. Container cranes serve to carry loads on one predetermined place to record them over a known Promote route and at a specified destination, for example a target container. This results in practice the problem that for the promotion of the load in Direction towards the target is not the exact actual position of the target is known. Instead, a target position of the target is known which, for example, by the middle of a given Target area can be defined.

A method according to the preamble of claim 1 is known from the DE magazine "Funding and lifting", Volume 42 (1992), No. 11, Pages 890 to 892. In this procedure, means the actual position of the load detected and fed a path control, which is dependent on the difference between the detected actual position of the load and a predetermined target position of the target controls the load towards the target. This method is, however, for a precise positioning of the load on Cannot use target.

The object of the invention is the known method to be modified in such a way that precise positioning the load on a target is possible.

This object is achieved in that in The actual position of the target by means of a sensor device Load and the actual position of the target relative to each other be fed and the path control, which is dependent the difference between the actual position of the load and the actual position of the target on the positioning of the load controls the target, taking as the load approaches the target between the different, fed the route control Position sizes is blended.

When conveying the load towards the goal, the Actual position of the load preferably by means of a path measuring device that constantly measures the position of a cat, to which the load hangs. With the measuring device it can is, for example, a displacement sensor or a laser distance measuring device act that the distance between the cat and a fixed reference position.

This enables a more precise determination of the actual position of the load achieved that in addition the pendulum angle of the load measured and together with the measured position of the Cat used to calculate the actual position of the load becomes. On the basis of the actual position thus measured Last it is possible for the path regulation, the promotion of the Regulate the load in such a way that the load oscillates during the conveyance and especially when arriving at the target position of the Target largely avoided. The measurement of the pendulum angle the load can be, for example, by an optical scanning device, such as B. a camera or preferably laser range finders, done on the cat is arranged and in a scanning angle range open downwards scans the outer edges of the load.

In a particularly simple manner and with particular achievement short measuring times the pendulum angle of the load is measured that in the area of the load a marking with reflective Surface is arranged that on the crane the marking directed lighting device and a line camera also pointed at the marking with a image sensor line aligned along the pendulum direction is arranged and that downstream of the image sensor line Evaluation device from the signal of the image sensor line one corresponding to the current position of the marking Output signal is generated. This measuring principle can alone or together with the measurement by the mentioned Laser distance profile measuring devices can be used. The measurement of the pendulum angle with the help of laser distance profile measuring devices and / or line scan camera is in EP-A-0 596 330 explained in detail.

When the load approaches the target, the Position control supplied position variables from the measured Actual position of the load and the target position of the target on the actual position detected relative to each other by the sensor device the load and actual position of the target are superimposed. Crossfading will cause a sudden change in the path control prevents sizes, so that jerky Load movements can be prevented.

The cross-fading is preferably carried out by the sensor device triggered. This can be an optical scanner comprise, which is arranged in the region of the crane and in a scanning angle range open downwards Outer edges of the load and the underlying environment of the Load scans, which is the optical scanner around a camera or preferably around laser distance profile measuring devices acts. The transition between the different position values supplied to the position control takes place when the sensor device simultaneously the load and the goal are grasped. After the transition then depending on the difference between that of the Sensor device determined actual positions of the load and the The goal is to position the load precisely on the target regulated.

As an alternative to the arrangement of the sensor device Scanning device on the crane can also in the Be arranged in the area of the load and in an open downward Scanning angle range scan the area around the load. In this case, the crossfade is triggered as soon as that Target is detected by the scanner. Because the scanner is located in the area of the load, it detects automatically the position of the target relative to each current position of the load. Such in the field of Load arranged scanner is in the European Patent application 93 10 9943.6 explained in detail.

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 hangenden Last mit einer an dem Containerkran angeordneten Zeilenkamera und mit Laser-Entfernungsprofilmeßgeräten an 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

FIG. 1

the basic process of conveying a load by means of a container crane from a starting position to a target position,

FIG 2

a container crane carrying the load, the trolley of which is equipped with laser distance profile measuring devices and a line scan camera,

FIG 3

a top view of the load,

FIG 4

a container crane for transporting a load hanging on a load suspension frame with a line camera arranged on the container crane and with laser distance profile measuring devices on the load suspension frame and

FIG 5

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 by the individual phases in FIG. 1, this load 3 is to be picked up at the starting position x ₀ 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 target 4 is not known, but only a target position x _Z *, which is defined, for example, as the center of a target area Δx _Z *. When the load 3 is conveyed from the start position x ₀ to the target 4, as will be explained later, the actual position x _{L 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 ϕ _{L of} the load 3 are continuously measured and the actual position x _{L of} the load 3 is determined from them. Depending on the difference between the actual position x _{L of} the load 3 and the target position x _Z * of the target 4, the trolley 1 is moved in the direction of the target 4 by a path 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, the actual position x _{L 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 as a function thereof 3 controlled on the target 4.

2 shows schematically the boom 2 with the movable thereon Cat 1 in the area of the target container 4. On the Cat 1 winches 5 are arranged, on which ropes 6 a load suspension frame (spreader) 7 for the to be transported Load 3 hangs. The load 3 should be on the one already parked Target container 4 are placed exactly in position. By starting and braking the cat 1 but also by external interference such. B. wind forces, the load 3 be put into a pendulum motion. The following will assumed that load 3 oscillations essentially in the direction of travel x of the cat 1, with additional load 3 can still oscillate.

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 instantaneous position x _{L 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 arranged above 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 or 13 perpendicular to the respective laser distance profile measuring device 10 or 11. In FIG 1, those locations 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 starting position x ₀ (FIG. 1) in the direction of the target container 4, the current pendulum angle Last _{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 uses the actual position x _{K of} the cat 1 to determine the actual position x _{L of} the load 3. As has already been explained with reference to FIG. 1, the actual position x _{L of} the load 3 thus obtained 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 determine the actual position x _{L of} the load 3 and the target position x _Z * of the target 4, but instead the position deviation between the load determined by the two laser distance profile measuring devices 10 and 11 3 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 range finders 10 and 11 in the x direction is not immediately over the respective outer edges 12 and 13 of the load suspension frame 7, but somewhat outside of it, so that below the Outer edges 12 and 13 none for laser beams 14 and 15 inaccessible blind spot. Like the top view on 3 shows the load suspension frame 7, are also the two laser range finders 10 and 11 with their Scanning angle ranges 14 and 15 transverse to the x direction, that is in z-direction offset. This makes it possible, except Pendulum movements in the x direction also include the pendulum To measure the load, which is expressed in the fact that the laser beams 14 and 15 measured x coordinates of the outer edges Change 12 and 13 differently. Because containers are different Can have constructions, the Outer edges 12 and 13 are the safest in the area of all Scan containers with the same corner fittings of container 4. Because containers also have different lengths can, are the two laser range finders 10 and 11 arranged in the z-direction on the trolley 1.

To detect the pendulum angle of the load, i.e. the position the load 3 in relation to the trolley 1 is supplementary the two laser distance profile measuring devices 10 and 11 a mark 16 is attached to the load-bearing frame 7, which from one at rest of the load 3 vertically above this headlights 17 held on the cat 1 is illuminated, the light reflected by the marker 16 from a arranged immediately next to or in the headlight 15 Line camera 18 is detected. The mark 16 consists of a rectangular, with an edge side parallel to Pendulum direction x aligned reflective surface, which is surrounded by a non-reflecting surface 19. The reflective surface 16 consists of a plurality of triple reflector elements, not shown here, on them reflect incident light in the direction from which it has come. This ensures that the the headlight 17 emitted light from the reflective Surface 16 in the headlight 17 immediately adjacent Line camera 18 is reflected back, independently from the respective amount of the pendulum deflection x. The Line camera 16 is arranged on the trolley 1 in such a way that their scanning plane 20 marks 16 along the pendulum direction x cuts. To record the position of the marking 16 becomes the serial output signal of the line camera 18 after the occurrence of the two brightness changes with each searched the greatest contrast and in this way the edges of the reflecting edges running transversely to the scanning direction 20 Area 16 detected. From the middle between the the position is determined for both detected brightness changes the middle of the mark 16 determined and as an output signal the line camera 18 provided. The difference to the two laser distance profile measuring devices 10 and 11 result considerably in the measurements with the line camera 18 shorter measuring times, what for the regulation of load oscillations and an advantage for load positioning control is.

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 associated outer edge 12 and 13 respectively of the load-bearing frame 7 scans the open angle range 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 x _{L of} the load 3, ie the difference between these two actual positions x _Z and x _{L, is} determined by means of the laser distance profile measuring devices 21 and 22.

Otherwise, the embodiment differs FIG 4 not of that of FIG 2, so that the same parts are 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 x _{L 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 x ₀ to the destination 4. The difference between the measured actual position x _{L of} the load 3 and the predetermined target position x _Z * of the target 4 is formed in a subtracting node 26 and is fed via a controllable switchover 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 x and 11 measured by the two laser distance profile measuring devices 10 and 11 _{L of} 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.

Relate 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, with the load (3) being picked up at a starting position (x₀), being conveyed over a horizontal section up to a target (4) and being deposited there, wherein by means of a position detection device (8, 10, 11, 18) the actual position (x_L) of the load (3) is detected and is supplied to a position control system (28), which controls the conveyance of the load (3) in the direction of the target (4) in dependence upon the difference between the detected actual position (x_L) of the load (3) and a specified desired position (x_Z*) of the target (4), characterized in that 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 in the vicinity of the target by means of a sensor device (10, 11; 21, 22) and are supplied to the position control system (28) which, in dependence upon the difference between the actual position (x_L) of the load (3) and the actual position (x_Z) of the target (4) controls the positioning of the load (3) at the target (4), wherein, when the load (3) approaches the target (4) there is mixing between the different position variables supplied to the position control system (28).
2. Method according to claim 1, characterized in that during the conveyance of the load (3) in the direction of the target (4) the actual position (x_L) of the load (3) is detected by means of a position measuring device (8) which continuously measures the position of a trolley carriage (1) on which the load (3) hangs.
3. Method according to claim 2, characterized in that in addition the swing angle (ϕ) of the load (3) is measured and is used together with the measured position (x_K) of the trolley carriage (1) to calculate the actual position (x_L) of the load (3).
4. Method according to claim 3, characterized in that a marking (16) with a reflective surface is arranged in the region of the load (3), in that a lighting device (17) directed to the marking (16) and a line camera (18) likewise directed to the marking (16) and having an image sensor line aligned longitudinally with respect to the swinging direction (x) are arranged on the crane, and in that in an evaluating device downstream of the image sensor line (18) an output signal corresponding to the instantaneous position of the marking (16) is generated from the signal of the image sensor line.
5. Method according to one of the preceding claims, characterized in that the mixing between the different position variables supplied to the position control system (28) is initiated by the sensor device (10, 11; 21, 22).
6. Method according to one of the preceding claims, characterized in that the sensor device comprises an optical scanning device (10, 11) which is arranged in the region of the crane, and in a scan angle region (14, 15) open to the bottom scans the outer edges (12, 13) of the load (3) and the environment of the load (3) lying beneath.
7. Method according to one of claims 1 to 5, characterized in that the sensor device comprises an optical scanning device (21, 22) which is arranged in the region of the load (3), and in a scan angle region (25) open to the bottom scans the environment of the load (3).

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