Unmanned operating method for a crane and the apparatus thereof

Abstract: A method and apparatus for the unmanned operation of a crane for moving containers e.g. for use on a harbour dockside which compensates for disturbances such as the wind during operation of the crane, detects the position and attitude of the spreader (40) and crane, thereby allowing the container (10) to be attached and detached automatically.

Description: The present invention relates to a method for operating a crane and more particularly, but not exclusively, to such a method for use with a crane situated in a harbour dockside. Generally, a crane is used for loading a ship with containers piled in a yard on a harbour dockside or for unloading containers from a ship. The crane is generally provided with a spreader for holding and releasing the container, a hoist for moving the container vertically and a trolley for moving the spreader horizontally. When the crane is operated manually, the trolley is driven horizontally at maximum speed and is then rapidly decelerated at a constant rate to reach a target position. In this case, it is difficult to make the trolley stop at the target position and severe spreader sway is generated. It therefore takes a long time to pick up or drop off a container when operating the crane manually. To overcome this problem, a method for the unmanned operation of a crane is proposed. According to this method the trolley and the hoist are driven according to a predetermined driving speed pattern to minimize spreader sway when the target position is reached. The relationship between the driving speed pattern in the unmanned operating method and the trolley and hoist will be described with reference to Figure 1. Figures 1A and 1B illustrate a method for the unmanned operation of a conventional crane, in which Figure 1A is a graph showing an example of the driving speed pattern for the conventional unmanned operating method and Figure 1B is a schematic diagram of the trolley and hoist for a general crane. According to the conventional unmanned operating method, a constant driving speed pattern is preset as shown in Figure 1A, and the trolley 20 or hoist 30 is operated to move the container 10 shown in Figure 1B. The driving speed pattern of the trolley 20 and hoist 30 are each obtained experimentally or empirically. For example, if the driving speed pattern illustrated in Figure 1A is for the trolley 20, the horizontal travelling speed of the trolley 20 is increased from a starting time at a constant ratio and is then decreased at a constant point of time and is then increased again to reach its maximum speed. The trolley is then maintained at its maximum speed for a predetermined interval. To stop the trolley 20, its horizontal travelling speed is decreased at a constant ratio, is increased at a point of time and is then decreased again. This conventional method for varying and adjusting the driving speed of the trolley 20 and hoist 30 has been used so that the spreader or container sways less when the trolley 20 stops at its target position. However, this conventional unmanned operating method generates frequent errors due to the initial vibration of the spreader, the vibration of the control system or the wind and other external factors. Thus, it is difficult to accurately control the sway of the spreader or the position of the trolley. Furthermore, it is difficult to hold and release the container without manual assistance resulting in the crane not being fully automatic. One method of operating a crane is known (see Proceedings of the IECON '93, Volume 1, 15/11/1993, pages 161-164, Osumu Itoh et al) and comprises the steps of inputting position information relating to an initial position and a target position of a trolley 20 and hoist 30, calculating a primary reference driving speed pattern of the trolley 20 and the hoist 30 based on said position information, obtaining an actual reference driving speed pattern by compensating the primary reference driving speed pattern, determining information relating to the sway angle and position of a spreader for holding and releasing a container suspended from the trolley 20 and hoist 30 during movement of the spreader under the control of a fuzzy operation controller, and supplying said information to the fuzzy operation controller such that the spreader releases the container at the target position. Other methods of controlling a crane are known for example, F&H Fördern und Weben, Vol. 42 (1992) pages 890-892, J. Hipp, and EP-A-0342655 both disclose methods by which the positions of a spreader and a container may be detected using sensors and scanning laser beams. An object of the present invention is to provide a method for operating a crane which enables a spreader to reach an exact target position with less sway than occurs with the conventional method so that a container may be easily attached and detached from the spreader. According to the invention there is provided a method for operating a crane comprising the step of obtaining an actual reference driving speed pattern by compensating the primary reference speed pattern in dependence on external error factors, said error factors being determined by a speed pattern generator in accordance with predetermined information relating to the movement of the container from the initial to the target position. The invention will now be described, by way of example only, with reference to the attached drawings, in which: Figures 1A and 1B are diagrams explaining an unmanned operating method for a conventional crane; Figure 2 is a block diagram of an unmanned driving apparatus for a crane according to the present invention; Figure 3 is a schematic diagram showing an example of the position detector shown in Figure 2; Figure 4 is a perspective view of a trolley for a crane to which the position detector shown in Figure 3 may be fitted; Figure 5 is a front view of a crane for use on a harbour dockside; Figure 6 is a side view of the trolley and spreader shown in Figure 5; Figure 7 is a plan view of the spreader in which sway has been generated; Figure 8 is a side view of the trolley and spreader when viewed in the arrow direction shown in Figure 7; FIGURE 9 a plan view of the spreader in which skew has been generated; FIGURE 10 is a plan view of the spreader in which both sway and skew have been simultaneously generated; FIGURE 11 is a diagram explaining a method for detecting the position of a spreader or container; FIGURE 12 is a front view of a crane for use on a quayside; FIGURE 13 is a side view of the spreader or container indicating the scanning loci of laser beams; FIGURE 14 is a plan view of the spreader or container indicating the scanning loci of laser beams; FIGURE 15 is a front view showing a crane which uses a position detector to detect the edge of a spreader and container; FIGURE 16 is a diagram explaining an edge detecting method for a spreader and container; FIGURE 17 is a diagram explaining a method for detecting the loading status of the containers piled in a yard using a position detector; FIGURE 18 is a flowchart showing the sequence of a method for determining the position of a spreader and container using a position detector; FIGURES 19A and 19B are flowcharts illustrating the overall operation of the crane on which an unmanned driving apparatus for a crane according to the present invention is installed; FIGURE 20 is a flowchart explaining in detail the pick-up operation shown in Figure 19; and FIGURES 21A and 21B are flowcharts explaining in detail the drop-off operation shown in Figure 19. Figure 2 illustrates an unmanned driving apparatus for a crane according to the present invention which includes a fuzzy logic controller 110, a drive 120 for driving various components of the crane, and a driver 130 driven in response to signals from the drive 120. The apparatus of the invention further includes a position detector 140 for detecting the position and attitude of the spreader and container and includes a sensor 141 and a sensor controller 142, which will be described in more detail with reference to Figure 3. The apparatus of the invention further includes an input key pad 160 for inputting data to the fuzzy logic controller 110, a master switch 170 for operating the crane manually on demand and a switch 150 for selecting a manual or automatic mode. The fuzzy logic controller 110 has a speed pattern generator 111 for obtaining a reference driving speed pattern for the trolley and a fuzzy operation controller 112 for compensating the reference driving speed pattern obtained in speed pattern generator 111 according to the surrounding errors. The speed pattern generator 111 generates each primary reference driving speed pattern V 1 and V 2 of the trolley and hoist by means of a microcomputer depending of the target position input to the input key pad 160 and the present states of the trolley and hoist. Once each primary reference driving speed pattern of the trolley and hoist is obtained, the speed pattern generator 111 carries out a simulation to obtain adjusted values ΔV 1 and ΔV 2 through a fuzzy operation using fuzzy control rules with the input values, i.e. the position of the trolley, the driven state of the hoist, the error between the present position ( x, y, z ) and target position due to the sway angle of the spreader and the error variation, the error between the present speed ( x, y, z ) and target speed and the error variation, and the error between the present accelerated speed ( x, y, z ) and target speed and the error variation. The speed pattern generator 111 adds the adjusted values ΔV 1 and ΔV 2 with V 1 and V 2 respectively, to obtain each reference driving speed pattern of trolley and hoist V T and V H . The fuzzy operation controller 112 operates the trolley and hoist according to the reference driving speed patterns V T and V H obtained from the speed pattern generator 111 and detects error factors such as sway angle of the spreader, disturbance due to wind or present position to compensate the reference driving speed patterns V T and V H through the fuzzy operation. The input values of the fuzzy operation are the error between the present state of the trolley and hoist and target state and the error variation, the error between the present driving speeds of the trolley and hoist and the driving speed by the reference driving speed pattern and the error variation, the error between the present sway angle supplied by the position detector and target sway angle and the error variation, and the error between the disturbances measured by a sensor and the error variation, and the output values are the compensated values of the reference driving speed patterns ΔV T and ΔV H . The input values are deducted by the fuzzy control rules. The fuzzy control rules are established by trial and error. For example, in the case where input variables are X and Y and an output variable is Z, the fuzzy control rules are defined as follows. 1. If X is A 1 and Y is B 1 , then Z is C 1 2. If X is A 2 and Y is B 2 , then Z is C 2 The fuzzy control rules used in the apparatus for the unmanned operation of a crane according to the present invention are as follows. Rule 1. If a vibration angle is X 3 is generated in a negative direction but the position and state (X 1 ,X 2 ) of the trolley/hoist do not reach a target state, then the accelerated speed is increased. Rule 2. If a vibration angle X 3 is generated in a positive direction but the position and state (X 1 ,X 2 ) of the trolley/hoist do not reach a target state, then the accelerated speed is decreased. That is to say, the fuzzy operation controller 112 executes a fuzzy deduction in accordance with the control rules obtained based on trial and error and compensates the reference driving speed patterns. Meanwhile, the position detector 140 detects with a sensor 141 the sway angle of the spreader when moving the trolley and supplies the detected sway angle to the fuzzy operation controller 112. The method of measuring the sway angle with the sensor 141 of the position detector 140 will be described in detail later. Also, the position detector 140 detects the target position and attitude of the container and spreader and supplies them to the controller of the trolley and hoist, thereby enabling the spreader of the crane to pick up or drop off the container at a precise position. The method of detecting the position and attitude of the spreader and container with the position detector 140 will be described in detail later. Figure 3 schematically illustrates the position detector shown in Figure 2 including a sensor 141 which can scan laser beams to measure the distance to the object. The sensor 141 is fixed on the sensor installation equipment 143. The sensor installation equipment 143 is movable along a ballscrew 146 installed on a fitting band 145 by means of a servo motor 144. An encoder 147 for measuring the moving distance of the sensor installation equipment 143 is installed in the servo motor 144. The position detector 140 has a driving panel 148 for controlling the drive to the servo motor 144 installed therein. In other words, the sensor 141 can scan laser beams and at the same time move linearly along the ballscrew 146. Figure 4 is a perspective view of the trolley of the crane on which the position detector shown in Figure 3 may be fitted and illustrates a pair of position detectors 140a and 140b on both ends of the trolley 20. Two position detectors 140a and 140b are preferably positioned diagonally for detecting diagonal edges of the spreader 40 and container 10, as shown. The sensors 141a and 141b installed in the position detectors 140a and 140b can scan laser beams in a direction across the width of the spreader 40 and can be moved in a direction along the length of the spreader 40 at the same time. That is to say, the position detectors 140a and 140b can detect diagonal edges of the container 10 by being moved into a position depending on the length of the container 10. Of course, the position detectors 140a and 140b can detect two diagonal edges of the spreader 40. Such position detectors 140a and 140b can be disposed in a line but it is preferable to dispose the position detectors 140a and 140b diagonally, as shown in Figure 4. The method of measuring the sway angle and skew angle of the spreader using the aforementioned position detectors will be described with reference to Figures 5 to 10. Figure 5 is a front view of the crane for use in a harbour dockside and shows a number of containers 10 beneath the crane. A trolley 20 is installed in the crane 100. The trolley is movable left and right. A sensor 141 of the position detector is installed on one side of the trolley 20 and an operating room 21 is installed on the other side thereof. A spreader 40 hangs from the trolley 20. The laser beams scanned from the sensors 141 face downward towards the spreader 40. Figure 6 is a side view of the trolley and spreader shown in Figure 5. As shown in Figures 5 and 6, the sensors 141 face the edges of the top surface of the spreader 40. The laser beams are scanned by the sensor 141 in a direction across the width of the spreader 40 and the sensor 141 is movable in a direction along the length of the spreader 40 at the same time. When measuring the sway or skew angle, it may not be necessary to move the sensor 141 in a direction along the length of the spreader 40. Figure 7 is a top view of the spreader in which sway has been generated. The dotted line 40a indicates an initial position of the spreader 40 in which no sway or skew has been generated and the solid line 40b indicates the position of the spreader 40 in which sway has been generated. The vertical lines 141d are scanning points at which the laser beams are scanned once in a direction across the width of the spreader 40. Figure 8 is a side view of the trolley 20 and spreader 40 when viewed in the direction of the arrow shown in Figure 7 and shows that the sway angle is known from the distance moved by the spreader when swaying and the length of a cable 41 to which the spreader 40 is hung. That is to say, the sway angle can be known by detecting and comparing the two initial edges of the spreader 40 before the sway is generated with the two edges thereof after the sway is generated. Of course, the length of the cable 41 to which the spreader 40 is hung can be known by installing an encoder to the hoist for adjusting the height of the spreader 40. Figure 9 is a top plan view of the spreader in which skew has been generated. The skew angle is the angle formed between a side of the spreader 40 when no skew has been generated indicated in a dotted line 40a and a side of the spreader 40 where a skew has been generated indicated in a solid line 40b. The skew angle is obtained by the variation of the position of the edges of the spreader from a constant point and the distance between the center of the spreader at that point. That is to say, the variation of the edges of the constant point of the spreader 40 is measured by the position detector, and the distance between the measuring point and the center of the spreader 40 is measured, thereby enabling the skew angle to be found. Of course, in order to know whether only sway is generated in the spreader 40 or not, the variation in position of the edges of the left and right ends should also be detected, as shown in Figure 9. Figure 10 is a top plan view of the spreader in which both sway and skew have been simultaneously generated. In this case, the average moving distance 42 of the spreader 40 generated by the sway is known by measuring the variation in position of the two edges with the position detector and calculating the sway angle from the measured variation and the length of the cable. The skew angle 43 is easily obtained by considering the variation in position of the two edges and the distance between two sensors. Figure 11 is a diagram explaining a method for detecting the position of a spreader or container and shows a top plan view of the spreader or container. In Figure 11, the portions indicated by double-bashed lines 140e are laser beam scanning areas covered by the position detectors, and dotted lines 141d indicated points within the scanning areas which the sensor scans once. That is to say, the sensor of the. position detector scans the laser beams in the direction across the width of the spreader 40 or container 10 and simultaneously moves in a direction along the length of the spreader. In this way, when the sensor reaches the end of the spreader 40 or container 10, the scanning distance changes sharply and the position detector detects both ends of the spreader 40 or container 10, thereby knowing exactly the position and attitude of the spreader 40 or container 10. Thereafter, the two sensors are rotated through a predetermined angle (45 degrees) and laser beams are scanned, thereby detecting the edges of the spreader 40 and container 10 from the trolley and gantry directions. The crane can then change the position and attitude of the spreader 40 or container 10 according to the position information of the spreader 40 or container 10 obtained by the position detector and can then pick up/set down the container exactly. That is to say, the position detector detects the sway of the spreader while the trolley is moving and feeds the information to the fuzzy controller. The position detector also detects the position and attitude of the spreader or container so that the spreader can pick up and set down the container exactly. To detect the spreader and container, at least one position detector may be installed in the lower trolley. An example of this will be described with reference to Figures 12 to 14. Figure 12 is a front view of the crane for use on a harbour dockside, Figure 13 is a side view of the position detector, spreader and container shown in Figure 12. Three position detectors 140a, 140b and 140c are fitted to the crane 100 so that they may move horizontally with the lower trolley 20. Two position detectors 140a and 140b scan laser beams in a direction across the width of the spreader 40 and container 10 as in the aforementioned embodiment, and the other position detector 140c scans laser beams around one end in a direction along the length of the spreader 40 and container 10. The scanning loci of the scanned laser beams are shown in Figure 14. Figure 14 is a top plan view of the spreader or container and shows the scanning loci 140d of two laser beams displayed in the direction across the width of the spreader 40 or container 10 and the other scanning locus displayed in the direction along the length of the spreader 40 or container 10. That is to say, the two position detectors 140a and 140b detect the two side edges of the spreader 40 or container 10 and the other position detector 140c detects an end edge of the spreader 40 or container 10 to accurately determine the attitude of the spreader 40 or container 10. The attitude of the spreader 40 or container 10 can be measured simultaneously by scanning a laser beam once. If the two sensors for scanning laser beams in a direction across the width of the spreader do not move in a direction along the length of the spreader another position detector can be fitted to detect the position and posture of the spreader 40 and the container 10. Figures 15 and 16 shows how the position of the containers loaded in the yard and the gaps therebetween are detected. Here, Figure 15 shows a crane which uses a position detector to detect the edges of the spreader and container. A pair of position detectors 140a and 140b are attached to a trolley 20 which can move to reach a target container 10. When the target container is reached the position detectors 140a and 140b detect the edge of the spreader 40 and container 10 and determine its position and attitude. The way in which the edges are detected will now be described in detail with reference to Figure 16. Figure 16 is a diagram illustrating the edge detecting method for a spreader and container. In Figure 16, the dots marked along the outer surface of the spreader 40 and container 10 represent scanning points of the laser beams scanned by the sensor 141. If the sensor 141 scans the spreader 40 and container 10 positioned beneath it, the scanning points are positioned on the surface of the spreader 40 and container 10. At this time, the positional information of the spreader and container obtained from scanning the laser beams are different. That is to say, scanning points dispersed from the sensor 141 to the ground surface 50 are divided by a distance and areas where the scanning points existing at each distance exceed a predetermined critical number are divided. Particularly as there are no components of the crane between the sensor 140 and spreader 40, the first area among the divided areas to be determined is the area of the spreader 40. Also, to make sure the areas for the spreader 40 and container 10 are correctly divided, the distance between the trolley and spreader, supplied from a hoist encoder (not shown) of the crane is considered and the areas of the scanning points measured near the hoist encoder values are determined as those for the spreader 40. In this manner, among the scanning points existing in the areas for the spreader 40 position information for the scanning point existing at the end thereof is located and the edge of the spreader 40 is detected. In other words, among the scanning points existing in the area for the spreader 40, the scanning point at the end has a sharp distance variation, compared with the next scanning point and is therefore recognized as an edge. As described above, after locating the edge of the spreader 40, among areas composed of the scanning points divided by the critical value, the area of the scanning points excluding the ground surface 50 and the area for the spreader 40 is determined for the container 10. The edge of the container 10 is also detected by the same method as that of detecting the edge of the spreader 40 as described above so that both the edges of the spreader 40 and container 10 are detected, thereby sensing the position and attitude of the spreader 40 and container 10. Figure 17 is a diagram illustrating a method for using a position detector to detect the load status of containers in a yard. As shown, a plurality of containers 10 are loaded on the ground surface 50 in rows and can be several tiers high. The load status of the yard is determined from the height of the containers 10 determined by a sensor 141 of the position detector attached to a movable trolley (not shown). The position detector detects the position of the trolley by means of a trolley encoder and scans laser beams. The number of rows of the containers 10 is detected from the ground surface area and the areas of the scanning points. The number of tiers of containers 10 is determined by obtaining the height of the containers from the ground surface. The number of tiers is calculated using the value of the height of the containers stored in the crane controller. Figure 18 is a flowchart illustrating the method sequences for determining the positions of the spreader and container with a position detector. Laser beams are scanned over the spreader (40) and container (10) with a sensor and the scanning points which are not measured are removed (step 200). The measured scanning points are divided by a interval depending on the distance (step 201). At this time, the divided scanning points are divided into areas where the scanning points exceeding a critical number exist and an area close to the measured value of the hoist encoder is selected for the spreader (steps 202 and 203). The point is detected where the distance changes sharply and is set as the edge of the spreader (step 204). Meanwhile, in the divided areas, the area having the largest critical value is selected among the spreader area and areas between the exposing surface and is determined as the container, a point where the distance variation is sharp is selected and is determined as the edge of the container, as described above (steps 205 and 206). As described above, if the edges of the spreader and container are detected, their positions can be easily determined. Figures 19A and 19B are flowcharts illustrating the overall operation of the crane according to the invention. Referring to Figure 19, the overall operation of the crane will be described. An automatic mode is selected by a console and a first target position for picking up a target container and a second target position for dropping off the target container are input via a key board (step 301 and 302). Coordinates are then input in a matrix with respect to a tier and row of the first and second target positions. A controller compares the first target position and the present position in a state where bo container is picked up and obtains a primary reference driving speed pattern for driving a trolley or hoist through a fuzzy operation (step 303). While travelling according to the obtained primary reference driving speed pattern, the sway angle is measured with a sensor to compensate the primary reference driving speed pattern through the fuzzy operation and the actual speed pattern is obtained. According to the compensated actual speed pattern, the driving speed or position of the hoist/trolley is controlled and the sway is controlled (step 304). Then, after comparing a first target position and a stop position, the trolley/gantry position error and skew angle of the spreader are measured (steps 305 and 306). The position error of the trolley is compensated according to the data obtained by the sensor and the skew angle is also compensated (steps 307 and 308). The spreader then proceeds to a process for picking up the container (step 309), which will be described in detail with reference to Figure 20 later. After the pick-up process, the second target position (termination position) input in step 302 and the present position are compared and a secondary reference driving speed pattern is obtained by a fuzzy operation (step 310). While travelling according to the obtained secondary reference driving speed pattern, the sway angle is measured with a sensor to compensate the secondary reference driving speed pattern through the fuzzy operation and the actual speed pattern is obtained. According to the compensated actual speed pattern, the driving speed or position of the hoist/trolley is adjusted and the sway is controlled (step 311). If the termination position is reached after comparing the termination position with the stop position, the trolley/gantry position error is measured and the skew angle of the spreader is also measured (steps 312 and 313). The position error and skew angle of the trolley are compensated with the thus measured position error and skew angle of the trolley (steps 314 and 315). After compensation, the spreader is descended to set down the container (step 316). The drop-off sequence will be described in detail with reference to Figure 21 later. Figure 20 is a flowchart illustrating in detail the pick-up operation shown in Figure 19. If the trolley stops at a target position, it is determined whether the trolley is in the holding position (step 400). If the trolley is not in the holding position, the position of the trolley is corrected due to the error and the position of the trolley is again determined (steps 401 and 400). When the trolley is in the holding position, the hoist is driven to descend the spreader (step 402). It is then determined whether the spreader has dropped off onto the holding position of the container (step 403). If the spreader has not dropped off, the process is fed back to steps 402 and 403 until the spreader has dropped off onto the container. After which the process proceeds to step 404. When it is determined that the spreader has dropped off the container, the hoist is stopped and the container is held with the spreader to lift the container (steps 404 and 405). Figures 21A and 21B are flowcharts for illustrating in detail the drop-off operation of the spreader shown in Figure 19. If the crane stops travelling in the direction of the gantry and the trolley moves to a target position to stop, it determines whether there are other containers beneath the target container. That is to say, it determines how many tiers there are, and if there is more than one it detects the load positions of the containers beneath the target container to measure the position error of the trolley/gantry direction and the skew angle of the spreader (steps 500 and 501). After compensating for the position error of the trolley and the skew angle of the spreader according to the measure error values, it determines whether the trolley is in the permit position (steps 502, 503 and 504) and if not the steps 501 to 504 are repeated. If the tier of the container is smaller than one, indicating that they are not stacked on top of each other, it determines from the encoder signal whether the trolley is in the permit position of the target position (step 504a). If the target container is not in the permit position, the position compensation is made by the trolley encoder (504b). If the target container is in the permit position, the hoist is driven to descend the spreader holding the container (step 505). In this manner, the processes of determining whether the drop-off is made or not are repeated while descending the spreader. If the container is dropped off, the drive of the hoist is terminated (steps 506 and 507) . After terminating the drive of the hoist, the container is released from the spreader (step 508) and the execution is terminated (step 509). If the container is not released from the spreader, a drop-off failure error is displayed (step 510). As described above with reference to Figures 2 to 21, in the method and apparatus for the unmanned operation of a crane, the sway of the spreader, due to disturbances such as the wind or the position error of the trolley is compensated and is therefore greatly reduced when the spreader stops at a target position. Therefore, using the method and apparatus for the unmanned operation of a crane according to the present invention reduces the time taken to pick up and set down containers. Also, the method and apparatus for the unmanned operation of a crane according to the present invention can detect the positions of the spreader and container accurately and pick up and set down a container without an operator, thereby allowing completely automatic operation.

Claims: A method of operating a crane (100) comprising the steps of inputting position information relating to an initial position and a target position of a trolley (20) and hoist (30), calculating a primary reference driving speed pattern of the trolley (20) and the hoist (30) based on said position information, obtaining an actual reference driving speed pattern by compensating the primary reference driving speed pattern, determining information relating to the sway angle and position of a spreader (40) for holding and releasing a container suspended from the trolley (20) and hoist (30) during movement of the spreader (40) under the control of a fuzzy operation controller (112), and supplying said information to the fuzzy operation controller (112) such that the spreader (40) releases the container at the target position, wherein the method includes the step of obtaining an actual reference driving speed pattern by compensating the primary reference speed pattern in dependence on external error factors, said error factors being determined by a speed pattern generator in accordance with predetermined information relating to the movement of the container (10) from the initial to the target position. A method as claimed in claim 1 including the step of determining the predetermined information relating to movement of the container (10) from the initial position to the target position based on the primary reference driving speed pattern through a simulation carried out by the speed pattern generator (111). A method according to any preceding claim wherein the position detector (140) has a sensor (141) mounted in an installation (143) movable in a direction along the length of the spreader (40) the method including the step of measuring the distance from a predetermined object by scanning a laser beam with a constant angle range. A method according to claim 3 wherein the method includes the step of scanning laser beams in a direction across the width of said spreader (40) using two diagonally disposed position detectors (140a,140b). A method according to claim 6 including the step of scanning laser beams in a direction along the length of said spreader (40), using a position detector (140c) having a sensor (141) provided in the lower portion of said trolley (20). A method as claimed in claims 3 to 5 wherein the step of determining information relating to the sway angle and positions of said spreader (40) includes the steps of detecting two initial edge positions of said spreader (40) having no sway by scanning laser beams, detecting two changed edge positions of said spreader (40) when said trolley (20) is travelling by scanning laser beams and comparing said two initial and changed edge positions of said spreader (40) and determining the sway angle of said spreader (40) by considering the length of a cable from which said spreader (40) is hung. A method as claimed in claim 6 wherein the step of determining the information relating to the sway angle and position of the spreader (40) and container (10) includes the steps of scanning laser beams over said spreader (40) and container (10), dividing scanned points into areas according to a distance value, said areas of said spreader (40) and container (10) being selected based on a predetermined value, the distance value of said spreader (40) being measured by a hoist encoder (147) installed in said crane (100), among said divided areas, and detecting edges of said spreader (40) and container (10) with said selected areas of said spreader (40) and container (10). A method as claimed in claim 7 including the step of scanning the laser beams to a predetermined angle (45 degrees) while moving sensor (141) is moved toward two diagonal edges of said spreader (40) and container (10) in each length direction. A method as claimed in claim 7 wherein the edges of said spreader (40) and container (10) detected in said edge detecting step are boundaries of scanning points at which the distance changes sharply among said detected areas of said spreader (40) and container (10). A method as claimed in claim 9 wherein the step of determining information relating to the sway angle and position of the spreader (40) and container (10) includes the step of detecting a skew angle of said spreader (40) and container (10) by comparing said detected edges of said spreader (40) and container (10) with initial edges thereof. A method as claimed in claim 7 wherein the step of dividing scanned parts include the step of scanning areas where scanning points exceeding a critical number exist and dividing those areas among all areas of scanning points. A method as claimed in claim 7 to 11 wherein the laser beams are scanned in a direction across the width of the spreader (40) while said sensor (141) is moved toward two diagonal edges of said spreader (40) and container (10) in each direction along the length of the spreader (40). A method as claimed in claim 12 wherein the laser beam scanning step, includes further scanning toward one end of said spreader (40) and container (10) along the length of said spreader (40) and container (10). A method as claimed in any of claims 1 to 6 including the steps of descending said spreader (40) by driving said hoist (30), determining whether said spreader (40) is picking-up or not and feeding back to said descending and determining steps if it is determined that said spreader (40) is not picking up. A method as claimed in any of claims 1 to 7 wherein the method includes the steps of descending said spreader (40) by driving said hoist (30), determining whether said spreader (40) is dropped off or not and feeding back to said descending and determining steps if it is determined that said spreader (40) is not dropped off. A method as claimed in any of claims 1 to 15 further comprising the step of detecting the container (10) load status by detecting the height of container (10) depending on the position of said trolley (20) by scanning laser beams along the rows of containers (10) loaded in the yard. A method according to any preceding claim wherein the external error factors include the error between the present states of said trolley (20) and hoist (30) and target states and the error variation, the error between the present driving speeds of said trolley (20) and hoist (30) and the driving speed by said reference driving speed pattern and the error variation, the error between the present sway angle supplied by said position detector (140) and target sway angle and the error variation.

Inventors: KANG MOON-HYUN, KIM JAE-HOON, LEE HYEONG-ROK, KANG, MOON-HYUN, KIM, JAE-HOON, LEE, HYEONG-ROK
Applicants: SAMSUNG HEAVY IND, SAMSUNG HEAVY INDUSTRIES CO., LTD
Application year: 1995
Main classification: B66C13
IPC codes: B66C19, B66C13