Stacking control system

Abstract

This invention provides a stacking control system that can improve the stacking accuracy of pallets when stacking multiple pallets on a loading platform using a forklift. [Solution] The stacking control system 1 includes a loading platform detection unit that detects the position and angle of the side edge 19b of the loading platform 19, a first stacking position calculation unit 33 that calculates the initial stacking position P0 of the first pallet to be stacked 12A1 based on the position and angle of the side edge 19b of the loading platform 19, a first stacking control unit 34 that stacks the first pallet to be stacked 12A1 at the initial stacking position P0, a pallet detection unit that detects the position of the stacked pallet 12B after the first stacking control unit 34 has been executed, a second stacking position calculation unit 36 ​​that calculates the next stacking position P of the second and subsequent second pallets to be stacked 12A2 based on the position of the stacked pallet 12B and the angle of the side edge 19b of the loading platform 19, and a second stacking control unit 37 that stacks the second pallet to be stacked 12A2 at the next stacking position P.

Description

Technical Field

[0001] The present invention relates to a stacking control system.

Background Art

[0002] As a conventional stacking control system, for example, as described in Patent Document 1, the position of an object is detected by an external sensor such as a laser sensor, and a point representing the loading platform is extracted based on point cloud data that is a set of points representing the position of the object, and a stacking position for performing loading on the loading platform is determined.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when stacking a pallet on the loading platform of a truck with a forklift, while the forklift travels in the front-rear direction of the truck, the side edge of the loading platform is detected to calculate the stacking position. In order to detect the side edge of the loading platform in this way, it is necessary for the forklift to travel along the front-rear direction of the truck around the truck to a certain extent. Also, for example, in order to detect the side edge of the loading platform of a truck using a laser sensor, it is necessary for the forklift to travel to a position away from the truck laterally so that the side edge of the loading platform falls within the irradiation range of the laser sensor. Therefore, when the lateral space from the truck is narrow, it is difficult to detect the side edge of the loading platform.

[0005] Therefore, one might consider detecting pallets already loaded on the truck bed and calculating the loading position for the next pallet. However, this method cannot be applied to loading the first pallet. In addition, the accuracy of pallet detection may deteriorate depending on the weather and working environment. In particular, if the accuracy of detecting the pallet angle is poor, the loading angles of the pallets may vary when multiple pallets are loaded sequentially next to each other on the truck bed. In this case, for example, the truck's tailgate may not be able to close.

[0006] The objective of the present invention is to provide a stacking control system that can improve the stacking accuracy of pallets when stacking multiple pallets on a loading platform using a forklift. [Means for solving the problem]

[0007] (1) One aspect of the present invention is a stacking control system for stacking a plurality of pallets on a loading platform in a specified direction adjacent to each other using a forklift having a plurality of forks for holding pallets, comprising: a loading platform detection unit that detects the position and angle of the loading side edge on the loading platform along the specified direction; a first stacking position calculation unit that calculates the stacking position of at least one first pallet to be stacked on the loading platform based on the position and angle of the loading side edge on the loading platform detected by the loading platform detection unit; and a forklift that stacks the first pallet to be stacked at the stacking position calculated by the first stacking position calculation unit. The system includes a first stacking control unit that controls the forklift, a pallet detection unit that detects the position of the previously stacked pallet on the loading platform after the first stacking control unit has been executed, a second stacking position calculation unit that calculates the stacking position of a second target pallet to be stacked on the loading platform after the first target pallet, based on the position of the previously stacked pallet detected by the pallet detection unit and the angle of the loading-side edge on the loading platform detected by the loading platform detection unit, and a second stacking control unit that controls the forklift so that the second target pallet to be stacked is stacked at the stacking position calculated by the second stacking position calculation unit.

[0008] In this type of stacking control device, the position and angle of the stacking edge on the loading side of the loading platform along a specified direction are detected, and the stacking position of at least one first target pallet to be stacked on the loading platform is calculated based on the position and angle of the stacking edge on the loading platform. The forklift is then controlled so that the first target pallet is stacked at that position. Subsequently, the position of the previously stacked pallet on the loading platform is detected, and the stacking position of a second target pallet to be stacked on the loading platform after the first target pallet is calculated based on the position of the previously stacked pallet and the angle of the stacking edge on the loading platform. The forklift is then controlled so that the second target pallet is stacked at that position. In this way, the stacking position of at least one first target pallet is calculated based on the position and angle of the stacking edge on the loading platform. Therefore, even when no pallets have yet been stacked on the loading platform, the first target pallet can be stacked at the appropriate position on the loading platform. Furthermore, the loading position of the second pallet to be loaded onto the truck bed after the first pallet to be loaded is calculated based on the position of the previously loaded pallet and the angle of the loading edge on the truck bed. The detection accuracy of the angle of the loading edge on the truck bed is higher than the detection accuracy of the angle of the pallet loaded on the truck bed. Therefore, the second pallet to be loaded can also be loaded accurately in the appropriate position on the truck bed. As a result, the accuracy of pallet loading is improved when loading multiple pallets onto a truck bed using a forklift.

[0009] (2) In (1) above, the second stacking position calculation unit may calculate the stacking position of the second stacking target pallet as a position offset from the previously stacked stacked pallet by an amount corresponding to the width dimension of the second stacking target pallet in a specified direction. This is done based on the position of the previously stacked stacked pallet and the angle of the edge on the stacking side of the loading platform.

[0010] In this configuration, adjacent pallets in the specified direction will be stacked on the loading platform either without gaps or with gaps between them. If adjacent pallets in the specified direction are stacked without gaps on the loading platform, many pallets can be stacked on the platform in a space-efficient manner. If adjacent pallets in the specified direction are stacked with gaps on the loading platform, for example, cushioning material can be placed between adjacent pallets to protect the goods placed on the pallets.

[0011] (3) In (1) or (2) above, the loading platform detection unit may detect the position and angle of the loading edge on the loading platform while the forklift is traveling along the specified direction, and the pallet detection unit may detect the position of the previously loaded pallet while the forklift is stopped in front of the previously loaded pallet.

[0012] In this configuration, the position and angle of the loading edge on the loading platform are detected in a short time, and the position of the loaded pallets is detected with high accuracy.

[0013] (4) In any of (1) to (3) above, the cargo bed detection unit is mounted on top of the forklift and has a laser sensor that detects the distance to the cargo bed by irradiating a laser toward the cargo bed and receiving the reflected light of the laser, and the position and angle of the loading edge on the cargo bed may be detected based on the point cloud data of the laser sensor.

[0014] In this configuration, the laser sensor is mounted on top of the forklift, allowing it to acquire point cloud data over a wide area around the forklift. Therefore, the position and angle of the loading edge on the loading platform can be detected with high accuracy.

[0015] (5) In any of (1) to (4) above, the pallet detection unit may be mounted on the side of the forklift and have a laser sensor that detects the distance to the stacked pallets by irradiating a laser toward the stacked pallets and receiving the reflected light of the laser, and the position of the stacked pallets may be detected based on the point cloud data of the laser sensor.

[0016] In this configuration, the laser sensor is mounted on the side of the forklift. When the forklift is positioned sideways to the loading platform, the laser is shone towards the stacked pallets on the platform, thereby detecting the position of the stacked pallets. In this case, even when the forklift is brought close to the loading platform, the entire front surface of the stacked pallets is more likely to be within the laser range of the laser sensor. Therefore, the position of stacked pallets can be detected even in narrow aisles or confined factory spaces.

[0017] (6) In any of (1) to (5) above, the first stacking position calculation unit calculates the stacking position of the first first pallet to be stacked on the loading platform based on the position and angle of the loading edge on the loading side of the loading platform, the first stacking control unit controls the forklift so that the first first pallet to be stacked is stacked at the stacking position, the second stacking position calculation unit calculates the stacking position of the second and subsequent second pallets to be stacked on the loading platform based on the position of the previously stacked pallet and the angle of the loading edge on the loading side of the loading platform, and the second stacking control unit controls the forklift so that the second and subsequent second pallets to be stacked are stacked at the stacking position.

[0018] In this configuration, the number of times the forklift needs to travel along a specified direction to calculate the loading position of the pallets based on the position and angle of the loading edge on the loading side of the loading platform can be minimized. Therefore, the time required to load multiple pallets onto the loading platform can be reduced. [Effects of the Invention]

[0019] According to the present invention, when stacking a plurality of pallets on a loading platform using a forklift, the stacking accuracy of the pallets can be improved.

Brief Description of the Drawings

[0020] [Figure 1] It is a block diagram showing the configuration of a stacking control system according to an embodiment of the present invention. [Figure 2] It is a side view of a forklift equipped with the stacking control system shown in FIG. 1. [Figure 3] It is a flowchart showing the procedure of the detection target discrimination process executed by the detection target discrimination unit shown in FIG. 1. [Figure 4] It is a flowchart showing the procedure of the loading platform side edge detection process executed by the loading platform side edge detection unit shown in FIG. 1. [Figure 5] It is a flowchart showing the procedure of the pallet position detection process executed by the pallet position detection unit shown in FIG. 1. [Figure 6] It is a plan view showing a state where a first stacking target pallet is stacked on the loading platform of a truck by a forklift. [Figure 7] It is a plan view and a schematic front view showing a state where the position of a stacked pallet placed on the loading platform of a truck is detected using a laser sensor mounted on the side of a forklift. [Figure 8] It is a side view showing the next stacking position of the stacking target pallet calculated by the second stacking position calculation unit shown in FIG. 1. [Figure 9] It is a plan view showing a state where a forklift holding a stacking target pallet travels toward the next stacking position. [Figure 10] It is a side view showing a state where a stacking target pallet is stacked at the next stacking position shown in FIG. 8. [Figure 11] It is a plan view showing a state where the stacking angles of the pallets stacked on the loading platform of a truck vary. [Figure 12] It is a plan view showing a state where the stacking angles of the pallets stacked on the loading platform of a truck do not vary. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0022] Figure 1 is a block diagram showing the configuration of a stacking control system according to one embodiment of the present invention. In Figure 1, the stacking control system 1 of this embodiment is mounted on a forklift 2 as shown in Figure 2, except for the higher-level system management device 27 which will be described later. The forklift 2 is a reach forklift. The forklift 2 is equipped with a traveling device 3 and a cargo handling device 4 which is located in front of the traveling device 3 and performs cargo handling.

[0023] The running gear 3 comprises a vehicle body 5, a pair of left and right reach legs 6 extending from the lower part of the vehicle body 5 to the front of the vehicle body 5, front wheels 7 which are steering wheels positioned at the tip (front end) of each reach leg 6, and rear wheels 8 which are drive wheels positioned at the left rear of the vehicle body 5. A caster wheel (not shown) is positioned at the right rear of the vehicle body 5.

[0024] The cargo handling device 4 includes a mast 9 positioned between each reach leg 6 and movable along the reach legs 6 in the front-rear direction of the vehicle body 5; a pair of left and right forks 13 attached to the mast 9 via a side shift bracket 10 and a lift bracket 11 so as to be movable (raised and lowered) in the vertical direction and for holding pallets 12 (see Figures 7 to 10); a lift cylinder 14 for raising and lowering the forks 13 via the side shift bracket 10 and the lift bracket 11; a reach cylinder 15 (see Figure 1) for moving the forks 13 in the front-rear direction by moving the mast 9 in the front-rear direction; and a side shift cylinder 16 (see Figure 1) for moving the forks 13 laterally (left-right direction) via the lift bracket 11.

[0025] Pallet 12 is a loading platform for carrying cargo (not shown). Pallet 12 is, for example, a flat pallet. In plan view, pallet 12 has a roughly rectangular shape. Pallet 12 is provided with two fork holes 17 into which each fork 13 is inserted (see Figures 8 and 10). The fork holes 17 extend from the front 12a of pallet 12 to the rear.

[0026] The loading control system 1 is a system that uses a forklift 2 to load pallets 12 onto the loading bed 19 of a truck 18 (see Figures 6 to 10). The loading control system 1 sequentially loads multiple pallets 12 onto the loading bed 19 from the front to the rear of the truck 18, ensuring that there are no gaps. In other words, the loading control system 1 loads the pallets 12 onto the loading bed 19 in order so that they are adjacent to each other in the front-to-back direction (specified direction) of the truck 18. The width W (see Figure 9) of all pallets 12 loaded onto the loading bed 19 is equal.

[0027] The loading control system 1 includes a communication device 20, a laser sensor 21, a map storage unit 22, a laser sensor 23, a driving unit 24, a cargo handling unit 25, and a controller 26.

[0028] The communication device 20 communicates wirelessly with the higher-level system management device 27. The communication device 20 receives information regarding the stacking of pallets 12 from the higher-level system management device 27 and transmits status information of the forklift 2 to the higher-level system management device 27.

[0029] Information regarding the stacking of pallets 12 includes information such as the dimensions of pallets 12, the number and stacking position of pallets 12 on the truck bed 19 of truck 18, and the number of times pallets 12 have been stacked on the truck bed 19. Information regarding the status of forklift 2 includes information such as the position of forklift 2.

[0030] The laser sensor 21 is mounted on top of the forklift 2, as shown in Figure 2. The laser sensor 21 is attached, for example, to the roof 5a of the vehicle body 5 via a mounting bracket 28. The laser sensor 21 emits a laser beam around the forklift 2 and receives the reflected laser light to detect the distance to objects around the forklift 2 and acquire point cloud data. The point cloud is a collection of laser reflection points.

[0031] The laser sensor 21 is a laser sensor for detecting the distance to the cargo bed 19 of the truck 18 by irradiating a laser beam toward the cargo bed 19 and receiving the reflected laser light. The horizontal irradiation range of the laser by the laser sensor 21 is 360 degrees. The vertical irradiation range of the laser by the laser sensor 21 is a specified angle θ0 (not shown). For example, a 3D LIDAR can be used as the laser sensor 21.

[0032] The map storage unit 22 stores map data of the area in which the forklift 2 operates. The map data includes buildings, pillars, shelves, and walls. The map data is created in advance using the laser sensor 21.

[0033] As shown in Figure 2, the laser sensors 23 are mounted on both sides of the forklift 2 (only the left side is shown in Figure 2). The laser sensors 23 are attached, for example, to the outer surface 29a of a mounting column member 29 erected on the vehicle body 5. The laser sensors 23 emit a laser beam toward the side of the forklift 2 and receive the reflected laser light to detect the distance to an object located beside the forklift 2 and acquire point cloud data.

[0034] The laser sensor 23 is a pallet detection laser sensor that detects the distance to the stacked pallets 12B (see Figure 7) already placed on the cargo bed 19 of the truck 18 by shining a laser beam towards the stacked pallets 12B and receiving the reflected light of the laser.

[0035] The horizontal and vertical irradiation ranges of the laser emitted by the laser sensor 23 are specified angles θ1 and θ2, respectively (see Figure 7). Specified angle θ1 is the angle at which the laser emitted from the laser sensor 23 hits the entire front surface 12a of the stacked pallet 12B when the forklift 2 is precisely positioned in front of the stacked pallet 12B. The precise position of the forklift 2 relative to the stacked pallet 12B is such that the laser sensor 23 faces the center of the front surface 12a of the stacked pallet 12B in the width direction. The horizontal irradiation range of the laser emitted by the laser sensor 23 is narrower than the horizontal irradiation range of the laser emitted by the laser sensor 21. For example, a 3D LIDAR can be used as the laser sensor 23.

[0036] The drive unit 24 is the drive unit that moves the forklift 2. The drive unit 24 includes, for example, a drive motor that rotates the rear wheels 8, which are the drive wheels, and a steering motor that steers the front wheels 7, which are the steering wheels, although these are not shown in the figures.

[0037] The cargo handling drive unit 25 is a drive unit that moves the forks 13. The cargo handling drive unit 25 is a drive unit that operates the hydraulic actuators for cargo handling, such as the lift cylinder 14, reach cylinder 15, and side shift cylinder 16.

[0038] The controller 26 is composed of a CPU, RAM, ROM, and an input / output interface, etc. The controller 26 includes a self-position estimation unit 30, a detection target discrimination unit 31, a cargo bed side edge detection unit 32, a first stacking position calculation unit 33, a first stacking control unit 34, a pallet position detection unit 35, a second stacking position calculation unit 36, and a second stacking control unit 37.

[0039] The self-position estimation unit 30 estimates the self-position of the forklift 2 based on the point cloud data from the laser sensor 21 and the map data stored in the map storage unit 22. Specifically, the self-position estimation unit 30 estimates the self-position of the forklift 2 by matching the point cloud data from the laser sensor 21 with the map data, for example, using the SLAM (simultaneous localization and mapping) method. SLAM is a self-position estimation technique that performs self-position estimation using sensor data and map data. At this time, the point cloud data from the laser sensor 21 is converted to a map coordinate system (absolute coordinate system).

[0040] The detection target determination unit 31 determines whether to detect the truck bed 19 or the loaded pallets 12B by determining whether there are already loaded pallets 12B on the truck bed 19 based on the point cloud data from the laser sensor 23.

[0041] Figure 3 is a flowchart showing the procedure for the detection target discrimination process performed by the detection target discrimination unit 31. This process begins when a pallet 12A (see Figures 6 and 7) to be loaded onto the truck bed 19 of the truck 18 is held by the fork 13 in a pallet storage area (not shown) near the truck 18.

[0042] In Figure 3, the detection target discrimination unit 31 first controls the driving drive unit 24 so that the forklift 2 starts traveling along the longitudinal direction of the truck 18 on one side of the truck 18, based on the self-position of the forklift 2 estimated by the self-position estimation unit 30 (procedure S101). At this time, the forklift 2 travels from the rear to the front of the truck 18 at a predetermined distance away from the truck 18.

[0043] Next, the detection target determination unit 31 acquires point cloud data from the laser sensor 23 for pallet detection (procedure S102). Then, based on the point cloud data from the laser sensor 23, the detection target determination unit 31 determines whether or not there are any stacked pallets 12B already placed on the cargo bed 19 of the truck 18 (procedure S103).

[0044] When the detection target determination unit 31 determines that there is a stacked pallet 12B on the cargo bed 19 of the truck 18, it controls the drive unit 24 so that the forklift 2 stops moving in front of the stacked pallet 12B (procedure S104). At this time, the detection target determination unit 31 controls the drive unit 24 so that the forklift 2 stops moving in front of the stacked pallet 12B that was previously stacked on the cargo bed 19. The stacked pallet 12B that was previously stacked on the cargo bed 19 will be described later. Then, the detection target determination unit 31 determines that the stacked pallet 12B is the target for detection (procedure S105).

[0045] If the detection target determination unit 31 determines in step S103 that there are no loaded pallets 12B on the truck bed 19 of the truck 18, it controls the drive unit 24 so that the forklift 2 stops moving in front of the truck bed 19 (step S106). Then, the detection target determination unit 31 determines that the truck bed 19 of the truck 18 is the detection target (step S107).

[0046] Returning to Figure 1, when the detection target determination unit 31 determines that the truck bed 19 of the truck 18 is the target for detection, the cargo bed side edge detection unit 32 detects the position and angle of the loading side edge 19b (see Figure 6) of the cargo bed 19 based on the point cloud data of the laser sensor 21. The side edge 19b of the cargo bed 19 is the edge in the width direction (Y direction) of the cargo bed 19 and extends in the front-rear direction (X direction) of the cargo bed 19. The loading side edge 19b of the cargo bed 19 is the side edge 19b on the side of the cargo bed 19 where the forklift 2 is located.

[0047] The cargo bed side edge detection unit 32 works in cooperation with the laser sensor 21 to constitute a cargo bed detection unit that detects the position and angle of the loading side edge 19b on the cargo bed 19 along the front-rear direction (specified direction). The cargo bed detection unit detects the position and angle of the loading side edge 19b on the cargo bed 19 as the forklift 2 travels along the specified direction.

[0048] Figure 4 is a flowchart showing the procedure for detecting the cargo bed edge, which is performed by the cargo bed edge detection unit 32. This process is executed when the detection target determination unit 31 determines that the cargo bed 19 of the truck 18 is the target for detection.

[0049] In Figure 4, the cargo bed edge detection unit 32 first acquires point cloud data from the laser sensor 21 used for cargo bed detection (procedure S111). The point cloud data from the laser sensor 21 is represented in the sensor coordinate system.

[0050] Next, the cargo bed edge detection unit 32 extracts a point cloud representing the loading surface 19a of the cargo bed 19 of the truck 18 based on the point cloud data from the laser sensor 21 (procedure S112). The loading surface 19a is the surface on the cargo bed 19 on which the pallet 12 is placed. Next, the cargo bed edge detection unit 32 extracts a point cloud representing the loading side edge 19b of the cargo bed 19 from the point cloud representing the loading surface 19a of the cargo bed 19 (procedure S113).

[0051] Next, the cargo bed side edge detection unit 32 calculates the straight line L (see Figure 6(a)) of the loading side edge 19b of the cargo bed 19 using a robust estimation method such as RANSAC (Random Sample Consensus) or the least squares method (procedure S114).

[0052] Next, the cargo bed side edge detection unit 32 calculates the position and angle of the straight line L on the loading side edge 19b of the cargo bed 19 (procedure S115). The position of the straight line L is the XY coordinate position of the straight line L with respect to the laser sensor 21. The angle of the straight line L is the inclination angle (yaw angle) of the straight line L with respect to the laser sensor 21.

[0053] Then, the cargo bed side edge detection unit 32 obtains the position and angle of the loading side edge 19b on the cargo bed 19 by converting the position and angle of the straight line L of the side edge 19b in the sensor coordinate system to the position and angle of the straight line L in the map coordinate system (procedure S116).

[0054] Returning to Figure 1, the first loading position calculation unit 33 calculates the initial loading position P0 of the first pallet to be loaded onto the loading platform 19 (referred to as the first pallet to be loaded 12A1) based on the position and angle of the loading side edge 19b on the loading side of the loading platform 19 detected by the loading platform side edge detection unit 32 (see Figure 6(a)). The initial loading position P0 is the loading position on the loading platform 19 where the first pallet to be loaded 12A1 is loaded.

[0055] The initial loading position P0 is a position at the front end of the truck bed 19 where the front surface 12a of the pallet 12 is slightly further back (inward in the width direction) than the loading-side edge 19b of the truck bed 19. Alternatively, the initial loading position P0 may be a position at the front end of the truck bed 19 where the front surface 12a of the pallet 12 coincides with the loading-side edge 19b of the truck bed 19.

[0056] The first stacking control unit 34 controls the travel drive unit 24 and the cargo handling drive unit 25 so that the first pallet to be stacked 12A1 is stacked at the initial stacking position P0 calculated by the first stacking position calculation unit 33 (see Figure 6(b)).

[0057] Specifically, the first loading control unit 34 controls the driving drive unit 24 so that the forklift 2 travels straight toward the rear of the truck 18, then curves toward the initial loading position P0, and stops just before reaching the initial loading position P0, based on the self-position of the forklift 2 estimated by the self-position estimation unit 30. The first loading control unit 34 then controls the cargo handling drive unit 25 so that the forks 13 move forward and downward to the initial loading position P0. As a result, the first pallet 12A1 to be loaded is placed on the initial loading position P0 of the loading platform 19.

[0058] After the first stacking control unit 34 is executed, the pallet position detection unit 35 detects the position of the previously stacked pallet 12B on the truck bed 19 based on the point cloud data from the laser sensor 23 when the detection target determination unit 31 determines that the previously stacked pallet 12B on the truck bed 19 is the target for detection. If multiple stacked pallets 12B are stacked on the truck bed 19, the stacked pallet 12B located at the rearmost end of the truck bed 19 corresponds to the previously stacked pallet 12B on the truck bed 19.

[0059] The pallet position detection unit 35, in cooperation with the laser sensor 23, constitutes a pallet detection unit that detects the position of the previously loaded pallet 12B on the loading platform 19 after the first loading control unit 34 has been executed. The pallet detection unit detects the position of the previously loaded pallet 12B when the forklift has stopped in front of the previously loaded pallet 12B.

[0060] Figure 5 is a flowchart showing the procedure for pallet position detection processing performed by the pallet position detection unit 35. This process is executed when the detection target determination unit 31 determines that the stacked pallet 12B is a target for detection.

[0061] In Figure 5, the pallet position detection unit 35 first acquires point cloud data from the laser sensor 23 for pallet detection (procedure S121). The point cloud data from the laser sensor 23 is represented in the sensor coordinate system.

[0062] Next, the pallet position detection unit 35 extracts a point cloud representing the front surface 12a of the previously loaded pallet 12B on the loading platform 19 based on the point cloud data from the laser sensor 23 (procedure S122). Subsequently, the pallet position detection unit 35 calculates the plane equation of the front surface 12a of the previously loaded pallet 12B on the loading platform 19 using a robust estimation method such as RANSAC or the least squares method (procedure S123).

[0063] Next, the pallet position detection unit 35 calculates the position of the front surface 12a of the previously loaded pallet 12B using a known method that utilizes the plane equation of the front surface 12a of the loaded pallet 12B that was previously loaded onto the loading platform 19 (procedure S124). The position of the front surface 12a of the loaded pallet 12B is the XY coordinate position of the front surface 12a of the loaded pallet 12B with respect to the laser sensor 23.

[0064] Then, the pallet position detection unit 35 converts the position of the front surface 12a of the stacked pallet 12B in the sensor coordinate system to the position of the front surface 12a of the stacked pallet 12B in the map coordinate system, thereby obtaining the position of the stacked pallet 12B that was previously stacked on the loading platform 19 (procedure S125).

[0065] Returning to Figure 1, the second loading position calculation unit 36 ​​calculates the next loading position P for the second and subsequent loading target pallets 12A (referred to as the second loading target pallet 12A2) to be loaded onto the truck bed 19 of the truck 18, based on the angle of the loading side edge 19b on the loading side of the truck bed 19 detected by the loading side edge detection unit 32 and the position of the previously loaded pallet 12B on the loading bed 19 detected by the pallet position detection unit 35 (see Figures 8 and 9).

[0066] The second pallet to be loaded, 12A2, is a pallet to be loaded onto the loading platform 19 after the first pallet to be loaded, 12A1. The next loading position P is the loading position on the loading platform 19 where the second and subsequent second pallets to be loaded, 12A2, are loaded. The next loading position P is the position adjacent to the previously loaded pallet 12B on the loading platform 19, to the rear.

[0067] The second loading position calculation unit 36 ​​calculates the next loading position P as a position offset by the width W of the second target pallet 12A2 to the rear of the truck bed 19 relative to the previously loaded pallet 12B on the truck bed 19. In other words, the second loading position calculation unit 36 ​​calculates the next loading position P for the second target pallet 12A2 as a position offset by an amount corresponding to the width dimension of the second target pallet 12A2 in the front-rear direction (specified direction) of the truck 18 relative to the previously loaded pallet 12B on the truck bed 19. Note that the width W of the target pallet 12A is equal to the width W of the loaded pallet 12B.

[0068] The second stacking control unit 37 controls the travel drive unit 24 and the cargo handling drive unit 25 so that the second and subsequent second stacking target pallets 12A2 are stacked at the next stacking position P calculated by the second stacking position calculation unit 36.

[0069] Specifically, the second loading control unit 37 first controls the driving unit 24 so that the forklift 2 moves backward a predetermined distance in front of it. Then, based on the self-position of the forklift 2 estimated by the self-position estimation unit 30, the second loading control unit 37 controls the driving unit 24 so that the forklift 2 travels straight toward the rear of the truck 18, then curves toward the next loading position P, and stops just before reaching the next loading position P. Finally, the second loading control unit 37 controls the cargo handling drive unit 25 so that the forks 13 move forward and downward to the next loading position P. As a result, the second and subsequent second loading target pallets 12A2 are placed on the next loading position P on the loading platform 19.

[0070] In the stacking control system 1 described above, when the forklift 2 loads the first pallet to be loaded 12A (first pallet to be loaded 12A1), the forklift 2 first travels to a pallet storage area (not shown) near the rear of the truck 18 and unloads the pallet to be loaded 12A.

[0071] Specifically, for example, a laser is shone from the laser sensor 23 toward the pallet 12A to be stacked, point cloud data from the laser sensor 23 is acquired, and the position and angle of the pallet 12A to be stacked are detected. Then, the reach cylinder 15 moves the fork 13 forward and inserts it into the fork hole 17 (see Figure 8) of the pallet 12A to be stacked, and then the lift cylinder 14 raises the fork 13 so that the pallet 12A to be stacked is held by the fork 13.

[0072] Then, as shown in Figure 6(a), the forklift 2 moves in reverse along the left side of the truck 18. While the forklift 2 is moving, a laser beam is shone from the laser sensor 21 towards the cargo bed 19 of the truck 18, and point cloud data from the laser sensor 21 is acquired.

[0073] Then, based on the point cloud data from the laser sensor 21, the position and angle of the left side edge 19b on the loading platform 19 are detected, and the initial loading position P0 of the first pallet 12A to be loaded on the loading platform 19 is calculated.

[0074] Then, as shown in Figure 6(b), forklift 2 travels straight toward the rear of truck 18 and then turns left toward the initial loading position P0, reaching a position just before the initial loading position P0. At this point, the reach cylinder 15 moves the forks 13 forward to the initial loading position P0, and the lift cylinder 14 lowers the forks 13, so that the first pallet to be loaded, pallet 12A, is placed at the initial loading position P0.

[0075] Next, when loading the second pallet to be loaded, 12A (second pallet to be loaded, 12A2), the forklift 2 travels to the pallet storage area (not shown) and unloads pallet 12A, as described above. Then, as shown in Figure 7, the forklift 2 travels in reverse along the left side of the truck 18 and stops in front of the front 12a of the loaded pallet 12B, which is placed on the initial loading position P0 of the truck bed 19.

[0076] At this time, the forklift 2 stops with its orientation sideways relative to the stacked pallet 12B which is placed at the initial stacking position P0. In this state, a laser beam is shone from the laser sensor 23 toward the stacked pallet 12B, and point cloud data from the laser sensor 23 is acquired.

[0077] Then, based on the point cloud data from the laser sensor 23, the position of the stacked pallet 12B is calculated. Then, as shown in Figure 8, based on the position of the stacked pallet 12B and the angle of the left side edge 19b on the loading platform 19, the next stacking position P of the second pallet to be stacked 12A on the loading platform 19 is calculated.

[0078] Here, the next stacking position P for the second pallet to be stacked, 12A, is offset to the rear of the truck 18 by the width W of the pallet 12, as shown in Figure 9.

[0079] Next, as shown in Figure 9, forklift 2 backs up to the front of truck 18, then moves straight forward toward the rear of truck 18, and then turns left toward the next loading position P, traveling to a position just before the next loading position P. Then, the reach cylinder 15 moves the forks 13 forward to the next loading position P. Then, as shown in Figure 10, the side shift cylinder 16 moves the forks 13 toward the loaded pallet 12B, and the lift cylinder 14 lowers the forks 13, so that the second pallet to be loaded, 12A, is placed at the next loading position P.

[0080] Subsequently, the third and subsequent pallets 12A (second pallet 12A2) are loaded sequentially. At this time, the next loading position P for the third and subsequent pallets 12A is offset to the rear of the truck 18 by the width W of the pallet 12 relative to the already loaded pallet 12B which is placed at the rearmost part of the truck bed 19.

[0081] Incidentally, the position and angle of the stacked pallet 12B are sometimes calculated based on the point cloud data from the laser sensor 23, and the next stacking position P of the pallet to be stacked 12A is calculated based on the position and angle of the stacked pallet 12B. The angle of the stacked pallet 12B is the inclination angle (yaw angle) of the stacked pallet 12B with respect to the side edge 19b on the loading side of the truck bed 19. However, in this case, the following problems arise.

[0082] In other words, the detection accuracy of the pallets 12 can be negatively affected by various factors, such as weather, working environment, the color and shape of the pallets 12, or the accuracy of the learning model. In particular, if the detection accuracy of the angle of the stacked pallets 12B is poor, the stacking angle θ of the pallets 12 may vary when multiple pallets 12 are stacked on the truck bed 19, as shown in Figure 11. In this case, the side panels (not shown) of the truck 18 may not close, or if other pallets 12 are placed on the opposite side of the truck 18 in the width direction (right side in Figure 11), the pallet 12A to be stacked may interfere with other pallets 12.

[0083] To address such challenges, in this embodiment, when the first pallet 12A to be stacked is stacked on the loading platform 19, the position and angle of the loading side edge 19b on the loading side of the loading platform 19 are detected using the laser sensor 21, and the initial stacking position P0 of the first pallet 12A to be stacked is calculated based on the position and angle of that side edge 19b. The detection accuracy of the angle of the side edge 19b of the loading platform 19 using the laser sensor 21 is generally considered to be relatively accurate.

[0084] Therefore, when loading the second and subsequent pallets 12A onto the loading platform 19, the laser sensor 23 is used to detect only the position of the previously loaded pallet 12B on the loading platform 19. Based on the position of the previously loaded pallet 12B and the angle of the side edge 19b of the loading platform 19, the next loading position P of the second and subsequent pallets 12A is calculated sequentially. As a result, as shown in Figure 12, when multiple pallets 12 are loaded onto the loading platform 19, variations in the loading angle θ of the pallets 12 are suppressed.

[0085] As described above, according to this embodiment, the position and angle of the loading-side edge 19b along the longitudinal direction of the truck 18 on the loading bed 19 are detected, and the initial loading position P0 of the first loading target pallet 12A1 to be loaded onto the loading bed 19 is calculated based on the position and angle of the loading-side edge 19b on the loading bed 19. The forklift 2 is then controlled so that the first loading target pallet 12A1 is loaded onto the loading bed 19 at that initial loading position P0. Subsequently, the position of the previously loaded pallet 12B on the loading bed 19 is detected, and the next loading position P of the second loading target pallet 12A2 to be loaded onto the loading bed 19 after the first loading target pallet 12A1 is calculated based on the position of the previously loaded pallet 12B and the angle of the loading-side edge 19b on the loading bed 19. The forklift 2 is then controlled so that the second loading target pallet 12A2 is loaded onto the loading bed 19 at that next loading position P. Thus, the initial loading position P0 of the first pallet to be loaded, 12A1, is calculated based on the position and angle of the loading-side edge 19b on the loading platform 19. Therefore, even when no pallets 12 have been loaded onto the loading platform 19, the first pallet to be loaded, 12A1, can be loaded in the appropriate position on the loading platform 19. Furthermore, the next loading position P of the second pallet to be loaded, 12A2, which will be loaded onto the loading platform 19 after the first pallet to be loaded, is calculated based on the position of the previously loaded pallet 12B and the angle of the loading-side edge 19b on the loading platform 19. The detection accuracy of the angle of the loading-side edge 19b on the loading platform 19 is higher than the detection accuracy of the angle of the pallets 12 loaded on the loading platform 19. Therefore, the second pallet to be loaded, 12A2, can also be loaded accurately in the appropriate position on the loading platform 19. As a result, when loading multiple pallets 12 onto the loading platform 19 using the forklift 2, the stacking accuracy of the pallets 12 is improved. Consequently, it is possible to prevent the side panels (not shown) of the truck 18 from failing to close, or for the pallet 12A to be loaded to interfere with other loaded pallets 12B placed on the opposite side in the width direction of the truck 18.

[0086] Furthermore, in this embodiment, based on the position of the previously loaded pallet 12B and the angle of the loading-side edge 19b on the loading side of the loading platform 19, the next loading position P of the second pallet 12A2 is calculated to be an offset from the previously loaded pallet 12B in the front-rear direction of the truck 18 by an amount corresponding to the width dimension of the second pallet 12A2. In this case, adjacent pallets 12 in the front-rear direction of the truck 18 will be loaded onto the loading platform 19 without any gaps between them. Therefore, many pallets 12 can be loaded onto the loading platform 19 in a space-efficient manner.

[0087] Furthermore, in this embodiment, when the first pallet to be loaded 12A1 is loaded onto the loading platform 19, the forklift 2 travels along the longitudinal direction of the truck 18, and the position and angle of the loading-side edge 19b on the loading platform 19 are detected. When the second and subsequent pallets to be loaded 12A2 are loaded onto the loading platform 19, the forklift 2 stops in front of the previously loaded pallet 12B, and the position of the previously loaded pallet 12B is detected. As a result, the position and angle of the loading-side edge 19b on the loading platform 19 are detected in a short time, and the position of the loaded pallet 12B is detected with high accuracy.

[0088] Furthermore, in this embodiment, the position and angle of the loading-side edge 19b on the loading platform 19 are detected based on the point cloud data from the laser sensor 21 mounted on top of the forklift 2. Because the laser sensor 21 is mounted on top of the forklift 2, it acquires point cloud data over a wide area around the forklift 2. Therefore, the position and angle of the loading-side edge 19b on the loading platform 19 can be detected with high accuracy.

[0089] Furthermore, in this embodiment, the position of the stacked pallets 12B is detected based on point cloud data from a laser sensor 23 mounted on the side of the forklift 2. Because the laser sensor 23 is mounted on the side of the forklift 2, the position of the stacked pallets 12B is detected by shining a laser towards the stacked pallets 12B placed on the truck bed 19 when the forklift 2 is positioned sideways to the truck bed 19. In this case, even when the forklift 2 is brought close to the truck bed 19, the entire front surface 12a of the stacked pallets 12B is more likely to fall within the laser irradiation range of the laser sensor 23. Therefore, the position of the stacked pallets 12B can be detected even in narrow passages or confined factory spaces.

[0090] Furthermore, in this embodiment, the initial loading position P0 of the first pallet 12A1 to be loaded onto the truck bed 19 is calculated based on the position and angle of the loading-side edge 19b on the loading side of the truck bed 19. Also, the next loading position P of the second and subsequent pallets 12A2 to be loaded onto the truck bed 19 is calculated based on the position of the previously loaded pallet 12B and the angle of the loading-side edge 19b on the loading side of the truck bed 19. Therefore, the number of times the forklift 2 is driven along the front-to-back direction of the truck 18 is minimized in order to calculate the loading position of the pallets 12A based on the position and angle of the loading-side edge 19b on the truck bed 19. Consequently, the time required to load multiple pallets 12 onto the truck bed 19 can be reduced.

[0091] It should be noted that the present invention is not limited to the embodiments described above. For example, in the above embodiment, adjacent pallets 12 are stacked without any gaps on the cargo bed 19 of the truck 18, but the present invention is not limited to this configuration, and adjacent pallets 12 may be stacked with gaps between them on the cargo bed 19 of the truck 18.

[0092] At this time, the second loading position calculation unit 36 ​​calculates the next loading position P as a position offset to the rear of the truck bed 19 by the sum of the width W and spacing of the second loading target pallet 12A2 relative to the previously loaded pallet 12B on the truck bed 19. In other words, the second loading position calculation unit 36 ​​calculates the next loading position P for the second loading target pallet 12A2 as a position offset to the front-rear direction (specified direction) of the truck 18 by an amount corresponding to the width dimension of the second loading target pallet 12A2 relative to the previously loaded pallet 12B on the truck bed 19. In this case, for example, by placing cushioning material between adjacent pallets 12, the cargo placed on the pallets 12 can be protected by the cushioning material.

[0093] Furthermore, in the above embodiment, the angle of the loading-side edge 19b of the truck bed 19 is detected using a 3D laser sensor 21 that irradiates a laser around the forklift 2 and receives the reflected laser light, but the system is not limited to this configuration. As the sensor that detects the angle of the loading-side edge 19b of the truck bed 19, a 2D laser sensor may be used, or multiple 1D laser sensors that irradiate a linear laser may be used, or a camera or the like may be used.

[0094] Furthermore, the sensor that detects the angle of the loading side edge 19b of the loading platform 19 does not necessarily have to be mounted on the forklift 2, but may be, for example, a fixed-point camera installed near the truck 18.

[0095] Furthermore, in the above embodiment, the controller 26 has a detection target determination unit 31 that determines whether or not there are stacked pallets 12B already placed on the cargo bed 19 of the truck 18, but such a detection target determination unit 31 is not particularly necessary. For example, based on the information of the number of pallets 12 on the cargo bed 19 and the stacking position information included in the information transmitted from the higher-level system management device 27, it may be determined whether or not there are stacked pallets 12B on the cargo bed 19, and the forklift 2 may be stopped moving at a position in front of the previously stacked pallet 12B on the cargo bed 19.

[0096] Furthermore, although the width W of all pallets 12 is the same in the above embodiment, the system is not limited to this configuration. If the width W of the next pallet 12A to be stacked is known, multiple types of pallets 12 with different widths W may be sequentially stacked on the truck bed 19 of the truck 18. Alternatively, width dimension information of the next pallet 12A to be stacked may be obtained from the higher-level system management device 27.

[0097] Furthermore, in the above embodiment, while the pallet 12A to be loaded is held by the forks 13, the position and angle of the loading-side edge 19b on the truck bed 19 are detected, and the position of the previously loaded pallet 12B on the truck bed 19 is also detected, but the system is not limited to this configuration. After the position and angle of the loading-side edge 19b on the truck bed 19 are detected, the forklift 2 may travel to the pallet storage area, pick up the first pallet 12A to be loaded, and load it onto the truck bed 19. Similarly, after the position of the previously loaded pallet 12B on the truck bed 19 is detected, the forklift 2 may travel to the pallet storage area, pick up the second and subsequent pallets 12A to be loaded, and load them onto the truck bed 19.

[0098] Furthermore, in the above embodiment, the initial stacking position P0 of the first stacking target pallet 12A (first stacking target pallet 12A1) is calculated based on the position and angle of the side edge 19b on the stacking side of the truck bed 19, and the next stacking position P of the second and subsequent stacking target pallets 12A (second stacking target pallet 12A2) is calculated based on the position of the already stacked pallet 12B and the angle of the side edge 19b on the stacking side of the truck bed 19, but the embodiment is not limited to such configurations. The first stacking target pallet 12A1 can be at least the first stacking target pallet 12A.

[0099] For example, the first to third stacking target pallets 12A may be the first stacking target pallet 12A1, and the fourth and subsequent stacking target pallets 12A may be the second stacking target pallet 12A2. In this case, the angle of the side edge 19b on the stacking side of the loading platform 19, obtained when calculating the stacking position of any of the first to third stacking target pallets 12A, may be used when calculating the stacking position of the fourth and subsequent stacking target pallets 12A.

[0100] Furthermore, in the above embodiment, the pallets 12 are stacked sequentially on the cargo bed 19 of the truck 18 from the front to the rear of the truck 18, but the configuration is not limited to this. The pallets 12 may also be stacked sequentially on the cargo bed 19 of the truck 18 from the rear to the front of the truck 18. In this case, the first pallet 12 is stacked at the rear end of the cargo bed 19. The stacking direction of the pallets 12 may also be instructed by the higher-level system management device 27.

[0101] Furthermore, in the above embodiment, when loading the pallet 12 onto the cargo bed 19 of the truck 18, the forks 13 are advanced to the initial loading position P0 or the next loading position P by the reach cylinder 15, but the system is not limited to this configuration. The forks 13 may be advanced to the initial loading position P0 or the next loading position P by advancing the forks 13 with the reach cylinder 15 and simultaneously moving the forklift 2 itself forward, or the forks 13 may be advanced to the initial loading position P0 or the next loading position P simply by moving the forklift 2 itself forward.

[0102] Furthermore, in the above embodiment, the forklift 2 has a pair (2) of forks 13 on the left and right sides, but the present invention is applicable to any forklift having multiple forks. For example, if the forklift has two pairs (4) of forks on the left and right sides, two pallets 12 can be held simultaneously by the two pairs of forks on the left and right sides. In this case, based on the position of either of the two previously loaded pallets 12B and the angle of the loading-side edge 19b on the loading side of the truck bed 19, the loading position of the two pallets 12A to be loaded is calculated to be offset from the two loaded pallets 12B in the front-rear direction of the truck 18 by an amount corresponding to the width dimension of the two pallets 12A to be loaded.

[0103] Furthermore, in the above embodiment, the pallets 12 are stacked on the cargo bed 19 of the truck 18, but the cargo bed on which the pallets 12 are stacked is not limited to the truck 18, but may be, for example, a truck berth or the like.

[0104] Furthermore, although the forklift 2 in the above embodiment has a side shift cylinder 16, the present invention is also applicable to forklifts that are not equipped with a side shift cylinder.

[0105] Furthermore, although forklift 2 is a reach forklift in the above embodiment, it goes without saying that the present invention is also applicable to counterbalanced forklifts. [Explanation of symbols]

[0106] 1...Stacking control system, 2...Forklift, 12...Pallet, 12A...Pallet to be stacked, 12A1...First pallet to be stacked, 12A2...Second pallet to be stacked, 12B...Stacked pallet, 13...Fork, 19...Loading platform, 19b...Side edge (edge), 21...Laser sensor (loading platform detection unit), 23...Laser sensor (pallet detection unit), 32...Loading platform side edge detection unit (loading platform detection unit), 33...First stacking position calculation unit, 34...First stacking control unit, 35...Pallet position detection unit (pallet detection unit), 36...Second stacking position calculation unit, 37...Second stacking control unit, P0...Initial stacking position (stacking position), P...Next stacking position (stacking position), W...Width.

Claims

1. A stacking control system for stacking multiple pallets on a loading platform in a specified direction adjacent to each other, using a forklift having multiple forks for holding pallets, A cargo bed detection unit that detects the position and angle of the loading edge of the cargo bed along the specified direction, A first stacking position calculation unit calculates the stacking position of at least one first stacking target pallet to be stacked on the loading platform based on the position and angle of the stacking side edge of the loading platform detected by the loading platform detection unit, A first stacking control unit controls the forklift so that the first stacking target pallet is stacked at the stacking position calculated by the first stacking position calculation unit, After the first loading control unit is executed, a pallet detection unit detects the position of the previously loaded pallet on the loading platform, A second stacking position calculation unit calculates the stacking position of a second stacking target pallet that will be stacked on the loading platform after the first stacking target pallet, based on the position of the previously stacked stacked pallet detected by the pallet detection unit and the angle of the stacking side edge on the loading platform detected by the loading platform detection unit. A stacking control system comprising: a second stacking control unit that controls the forklift so that the second stacking target pallet is stacked at the stacking position calculated by the second stacking position calculation unit; and a second stacking control unit.

2. The stacking control system according to claim 1, wherein the second stacking position calculation unit calculates the stacking position of the second stacking target pallet as a position offset from the previously stacked stacked pallet by an amount corresponding to the width dimension of the second stacking target pallet in the specified direction, based on the position of the previously stacked stacked pallet and the angle of the edge on the stacking side of the loading platform.

3. The aforementioned cargo bed detection unit detects the position and angle of the loading edge on the cargo bed while the forklift is traveling along the specified direction. The stacking control system according to claim 1, wherein the pallet detection unit detects the position of the previously stacked pallet when the forklift has stopped in front of the previously stacked pallet.

4. The loading control system according to claim 3, wherein the loading platform detection unit is mounted on top of the forklift and has a laser sensor that detects the distance to the loading platform by irradiating a laser toward the loading platform and receiving the reflected light of the laser, and detects the position and angle of the loading edge on the loading side of the loading platform based on the point cloud data of the laser sensor.

5. The stacking control system according to claim 3, wherein the pallet detection unit is mounted on the side of the forklift and has a laser sensor that detects the distance to the stacked pallet by irradiating a laser toward the stacked pallet and receiving the reflected light of the laser, and the position of the stacked pallet is detected based on the point cloud data of the laser sensor.

6. The first stacking position calculation unit calculates the stacking position of the first pallet to be stacked on the loading platform based on the position and angle of the edge on the stacking side of the loading platform, The first stacking control unit controls the forklift so that the first pallet to be stacked is stacked at the stacking position. The second stacking position calculation unit calculates the stacking position of the second and subsequent second stacking target pallets to be stacked on the loading platform based on the position of the previously stacked pallet and the angle of the edge on the loading side of the loading platform. The stacking control system according to claim 1, wherein the second stacking control unit controls the forklift so that the second and subsequent second stacking target pallets are stacked at the stacking position.

Images