Stacking control system

Abstract

This invention provides a stacking control system that can appropriately stack pallets at specified intervals relative to existing pallets. [Solution] The stacking control system 1 includes a positional displacement calculation unit 35 that calculates the amount of lateral displacement Δd of the forklift 2 with respect to the travel path R of the forklift 2, a follow control unit 39 that controls the travel drive unit 24 to make the forklift 2 follow along the travel path R in a direction in which the amount of lateral displacement Δd of the forklift 2 approaches zero, and a stacking control unit 40 that controls the cargo handling drive unit 25 so that the pallet to be stacked 17B is stacked at the stacking position P. Based on the amount of lateral displacement Δd calculated by the positional displacement calculation unit 35, the stacking control unit 40 controls the side shift cylinder 16 so that the distance between the existing pallet 17A and the pallet to be stacked 17B becomes a specified distance G, and also controls the lift cylinder 13 so that the pallet to be stacked 17B is placed on the loading platform 19.

Description

[Technical Field]

[0001] This invention relates to a stacking control system. [Background technology]

[0002] Conventional loading control systems include, for example, the one described in Patent Document 1, which uses external sensors such as laser sensors to detect the position of an object, extracts points representing the loading platform based on point cloud data which is a set of points representing the positions of the objects, and determines the loading position on the loading platform for loading cargo. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-30983 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, when a forklift is used to arrange and load pallets onto the bed of a truck or other vehicle, the forklift detects the bed, calculates the loading position and the travel path to the loading position, and moves to the loading position following the calculated travel path. In this case, it may be required to load pallets at specified intervals from existing pallets already loaded on the bed. However, due to factors such as the amount of lateral displacement relative to the forklift's travel path, it may be difficult to load pallets at specified intervals.

[0005] The objective of the present invention is to provide a stacking control system that can appropriately stack pallets at specified intervals relative to existing pallets. [Means for solving the problem]

[0006] (1) One aspect of the present invention is a stacking control system for stacking 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 driving unit for moving the forklift; a cargo handling drive unit including a lift cylinder for raising and lowering the forks and a side shift cylinder for moving the forks in the left and right directions of the forklift; a self-position estimation unit for estimating the self-position of the forklift; a pallet detection unit for detecting the position of existing pallets already placed on the loading platform; a stacking position calculation unit for calculating the stacking position of the next pallet to be stacked on the loading platform based on the position of the existing pallet detected by the pallet detection unit; and a system for generating a driving path for the forklift to the stacking position calculated by the stacking position calculation unit. The system includes a road generation unit, a positional deviation calculation unit that calculates the amount of lateral deviation of the forklift relative to the travel path based on the travel path of the forklift generated by the path generation unit and the self-position of the forklift estimated by the self-position estimation unit, a follow control unit that controls the travel drive unit to make the forklift follow the travel path in a direction that approaches zero as calculated by the positional deviation calculation unit, and a loading control unit that controls the cargo handling drive unit so that the pallets to be loaded are loaded at the loading position. The loading control unit controls the side shift cylinder so that the distance between the existing pallet and the pallet to be loaded becomes a specified distance based on the amount of lateral deviation calculated by the positional deviation calculation unit, and controls the lift cylinder so that the pallets to be loaded are placed on the loading platform.

[0007] In this type of stacking control system, a side shift cylinder is controlled to move the forks in the left-right direction of the forklift based on the amount of lateral displacement of the forklift relative to its travel path to the stacking position of the next pallet to be stacked on the loading platform. This is done so that the distance between an existing pallet already on the loading platform and the pallet to be stacked becomes a specified distance. As a result, even if the forklift has lateral displacement relative to its travel path when it reaches the stacking position, the side shift cylinder will control the forks to move in the left-right direction so that the distance between the existing pallet and the pallet to be stacked becomes a specified distance. Consequently, the pallet to be stacked can be appropriately stacked at a specified distance from the existing pallet.

[0008] (2) In (1) above, the stacking control system further comprises a determination unit that makes a decision based on the calculation result by the position deviation calculation unit, the position deviation calculation unit calculates the amount of lateral deviation and angular deviation of the forklift with respect to the travel path based on the travel path of the forklift and the position of the forklift, the follow control unit controls the travel drive unit to make the forklift follow along the travel path in a direction in which the amount of lateral deviation and angular deviation of the forklift approaches zero, the determination unit determines whether the angular deviation of the forklift calculated by the position deviation calculation unit is smaller than a predetermined threshold, and if the determination unit determines that the angular deviation is smaller than the threshold, the stacking control unit may control the side shift cylinder so that the distance between the existing pallet and the pallet to be stacked becomes a specified distance based on the amount of lateral deviation calculated by the position deviation calculation unit.

[0009] In this configuration, even if there is an angle deviation of the forklift relative to the travel path, if the angle deviation is small, for example, by setting the specified interval slightly larger, control is executed to move the forks left and right so that the distance between the existing pallet and the pallet to be loaded becomes the specified interval, without specifically considering the angle deviation. This simplifies the calculation process.

[0010] (3) In (2) above, the stacking control system further includes a proximity calculation unit that calculates the closest proximity point on the stacking target pallet to an existing pallet based on the amount of lateral displacement and angular displacement of the forklift, and the stacking control unit may, if the judgment unit determines that the angular displacement is greater than or equal to a threshold, control the side shift cylinder so that the distance between the proximity point calculated by the proximity calculation unit and the existing pallet becomes a specified distance.

[0011] In this configuration, because the angle deviation of the forklift relative to the travel path is relatively large, if there is a large difference between the distance between the front corner of the existing pallet and the pallet to be stacked, and the distance between the existing pallet and the rear corner of the pallet to be stacked, the forks are moved left and right in the direction of the forklift so that the distance between the closest adjacent part of the pallet to be stacked and the existing pallet becomes the specified distance. This prevents the distance between the pallet to be stacked and the existing pallet from becoming smaller or larger than the specified distance.

[0012] (4) In (3) above, the stacking control system further includes a relative angle detection unit that detects the relative angle of the stacking target pallet with respect to the forks, and the proximity calculation unit may calculate the proximity based on the amount of lateral displacement and the relative angle detected by the relative angle detection unit when the judgment unit determines that the angular displacement is greater than or equal to a threshold.

[0013] In this configuration, the relative angle of the pallet to be stacked with respect to the fork is also taken into consideration when calculating the proximity of the pallet to be stacked. Therefore, even if a gap is created between the back of the fork and the pallet to be stacked, resulting in a relatively large relative angle of the pallet to the fork, the pallets to be stacked can be properly stacked so that the distance between the proximity of the pallet to be stacked and the existing pallet is the specified distance.

[0014] (5) In any one of the above (1) to (4), the stacking control system further includes a specified interval determination unit that determines a specified interval based on the state of the goods placed on at least one of the existing pallet and the pallet to be stacked, and the stacking control unit may control the side shift cylinder so that the interval between the pallet to be stacked and the existing pallet becomes the specified interval determined by the specified interval determination unit.

[0015] In such a configuration, even when the goods placed on at least one of the existing pallet and the pallet to be stacked protrude in the width direction of the pallet from the pallet, the interval between the goods placed on one of the existing pallet and the pallet to be stacked and the other of the existing pallet and the pallet to be stacked, or the interval between the goods placed on the existing pallet and the pallet to be stacked respectively can be prevented from becoming extremely narrow.

Effect of the Invention

[0016] According to the present invention, a pallet can be appropriately stacked at a position with a specified interval from an existing pallet.

Brief Description of the Drawings

[0017] [Figure 1] It is a block diagram showing the configuration of the stacking control system according to the first embodiment. [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 an example of the procedure of the pallet position detection process executed by the pallet detection unit shown in FIG. 1. [Figure 4] It is a plan view and a schematic front view showing a state of detecting the position of an existing pallet placed on the loading platform of a truck using a laser sensor mounted on the side of a forklift. [Figure 5] It is a plan view showing a state of running a forklift holding a pallet to be stacked toward a stacking position. [Figure 6]Figure 5 is a side view showing the state in which the pallets to be stacked are stacked at the stacking position indicated. [Figure 7] Figure 1 is a flowchart illustrating an example of the processing steps performed by the controller shown. [Figure 8] This is a plan view showing how a forklift holding a stacking pallet acquires the amount of lateral displacement and angular displacement relative to the travel path when it arrives on the truck bed. [Figure 9] This is a plan view showing how the pallets to be loaded are moved towards the existing pallets by the side shift cylinder when a forklift holding the pallets to be loaded arrives on the truck bed without being tilted relative to the travel path. [Figure 10] This is a plan view illustrating an example of how a pallet to be loaded is moved towards an existing pallet by a side shift cylinder when a forklift holding a pallet to be loaded arrives on the truck bed at an inclination relative to its travel path. [Figure 11] This is a plan view illustrating another example of how a pallet to be loaded is moved towards an existing pallet by a side shift cylinder when a forklift holding a pallet to be loaded arrives on the truck bed at an inclination relative to its travel path. [Figure 12] This is a block diagram showing the configuration of the stacking control system according to the second embodiment. [Figure 13] This is a plan view showing how a pallet to be stacked is moved towards an existing pallet by a side shift cylinder while it is tilted relative to the forks. [Figure 14] This is a block diagram showing the configuration of the stacking control system according to the third embodiment. [Figure 15] This is a plan view showing how pallets containing goods are loaded onto the bed of a truck. [Modes for carrying out the invention]

[0018] 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.

[0019] Figure 1 is a block diagram showing the configuration of a stacking control system according to the first 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. The forklift 2 is a reach forklift. The forklift 2 comprises a traveling device 3 and a cargo handling device 4 positioned in front of the traveling device 3 for handling cargo.

[0020] 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.

[0021] The cargo handling device 4 includes a mast 10 positioned between each reach leg 6 and movable along the reach legs 6 in the longitudinal direction of the vehicle body 5; a pair (2) of forks 12 on the left and right sides that are mounted on the mast 10 so as to be able to be raised and lowered via a side shift bracket 15 and a lift bracket 11 to hold a pallet 17 (see Figures 4 and 5); a lift cylinder 13 that raises and lowers the forks 12 via the side shift bracket 15 and the lift bracket 11; a reach cylinder 14 (see Figure 1) that moves the forks 12 in the longitudinal direction of the vehicle body 5 by moving the mast 10 in the longitudinal direction of the vehicle body 5; and a side shift cylinder 16 (see Figure 1) that moves the forks 12 in the left-right direction (in the width direction of the forklift 2) via the lift bracket 11.

[0022] The fork 12 is formed in an L-shape when viewed from the side of the forklift 2. The fork 12 has a rear portion 12a that extends in the vertical direction and an insertion portion 12b that extends from the lower end of the rear portion 12a toward the front of the forklift 2. The fork 12 is detachably attached to the lift bracket 11 at the rear portion 12a.

[0023] Pallet 17 is a loading platform for carrying cargo (not shown). Pallet 17 is, for example, a flat pallet. In plan view, pallet 17 has a roughly rectangular shape. Pallet 17 is provided with two fork holes 17a into which the insertion portion 12b of each fork 12 is inserted (see Figure 6). The fork holes 17a extend from the front 17b of pallet 17 to the rear.

[0024] The loading control system 1 is a system that uses a forklift 2 to load pallets 17 onto the loading bed 19 of a truck 18 (see Figures 4 to 6). The loading control system 1 sequentially loads the pallets 17 onto the loading bed 19 from the front to the rear of the truck 18 while maintaining a specified interval G. The specified interval G is, for example, the interval provided to insert cushioning material (not shown) between adjacent pallets 17. In this embodiment, the specified interval G is a predetermined fixed interval. The loading control system 1 sequentially loads the pallets 17 onto the loading bed 19 while maintaining the specified interval G so that they are adjacent to each other in the front-to-rear direction (specified direction D1) of the truck 18.

[0025] In this embodiment, the width W of the pallets 17 stacked on the cargo bed 19 is, for example, all equal. Also in this embodiment, it is assumed that at least one pallet 17 is already placed on the loading surface 19a of the cargo bed 19 of the truck 18 as an existing pallet 17A (see Figures 4 to 6).

[0026] 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.

[0027] 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 17 from the higher-level system management device 27 and transmits status information of the forklift 2 to the higher-level system management device 27.

[0028] 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.

[0029] The laser sensor 21 is a first laser sensor that detects 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. As the laser sensor, for example, a 3D LIDAR can be used.

[0030] 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.

[0031] 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.

[0032] The laser sensor 23 is a second laser sensor that detects the distance to the existing pallet 17A by shining a laser beam towards the existing pallet 17A already placed on the cargo bed 19 of the truck 18 and receiving the reflected laser light.

[0033] The horizontal and vertical irradiation ranges of the laser emitted by the laser sensor 23 are defined angles θ1 and θ2, respectively (see Figure 4). The defined angle θ1 is the angle at which, when the forklift 2 is positioned in front of the existing pallet 17A, the laser emitted from the laser sensor 23 hits the entire front surface 17b of the existing pallet 17A. For example, a 3D LIDAR can be used as the laser sensor 23.

[0034] 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.

[0035] The cargo handling drive unit 25 is a drive unit that moves the forks 12. The cargo handling drive unit 25 includes the lift cylinder 13, reach cylinder 14, and side shift cylinder 16, etc.

[0036] The controller 26 consists of a CPU, RAM, ROM, and an input / output interface, etc. The controller 26 includes a self-position estimation unit 30, a pallet detection travel control unit 31, a pallet detection unit 32, a stacking position calculation unit 33, a path generation unit 34, a position deviation calculation unit 35, a position deviation direction determination unit 36, an angle deviation determination unit 37 (determination unit), a proximity calculation unit 38, a follow control unit 39, and a stacking control unit 40.

[0037] 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 uses sensor data and map data to estimate the self-position.

[0038] The pallet detection travel control unit 31 controls the travel drive unit 24 so that the forklift 2 travels to just before the existing pallet 17A. At this time, the pallet detection travel control unit 31 drives the forklift 2 to just before the existing pallet 17A that is placed at the very rear of the truck bed 19 of the truck 18. The existing pallet 17A that is placed at the very rear of the truck bed 19 of the truck 18 is the pallet 17 that was previously loaded onto the truck bed 19.

[0039] The pallet detection travel control unit 31 controls the travel drive unit 24 so that the forklift 2 stops with the forklift 2 facing sideways to the existing pallet 17A (see Figure 4(a)). At this time, the pallet detection travel control unit 31 stops the forklift 2 in a position where the laser sensor 23 is facing the center of the existing pallet 17A in the width direction.

[0040] The pallet detection unit 32 detects the position of existing pallets 17A placed on the loading platform 19 based on the point cloud data from the laser sensor 23. At this time, the pallet detection unit 32 detects the position of the existing pallet 17A placed at the rearmost end of the loading platform 19. The pallet detection unit 32 detects the position coordinates and tilt angle of the existing pallet 17A as the position of the existing pallet 17A.

[0041] The pallet detection unit 32 works in cooperation with the laser sensor 23 to form a pallet detection unit that detects the position of the existing pallet 17A.

[0042] Figure 3 is a flowchart showing the procedure for pallet position detection processing performed by the pallet detection unit 32. In Figure 3, the pallet detection unit 32 first acquires point cloud data from the laser sensor 23 (second laser sensor) (procedure S111).

[0043] Next, the pallet detection unit 32 extracts a point cloud representing the front surface 17b of the existing pallet 17A based on the point cloud data from the laser sensor 23 (procedure S112). Subsequently, the pallet detection unit 32 calculates the plane equation of the front surface 17b of the existing pallet 17A using a robust estimation method such as RANSAC or the least squares method (procedure S113).

[0044] Next, the pallet detection unit 32 calculates the position coordinates and inclination angle of the existing pallet 17A relative to the forklift 2 using a known method that utilizes the plane equation of the front surface 17b of the existing pallet 17A (procedure S114). The position coordinates of the existing pallet 17A relative to the forklift 2 are the three-dimensional position coordinates of the front surface 17b of the existing pallet 17A relative to the laser sensor 23. The inclination angle of the existing pallet 17A relative to the forklift 2 are the yaw angle, pitch angle, and roll angle of the existing pallet 17A relative to the laser sensor 23. This gives the position of the existing pallet 17A.

[0045] Returning to Figure 1, the stacking position calculation unit 33 calculates the stacking position P (see Figure 5) of the next pallet to be stacked on the truck bed 19, based on the position of the existing pallet 17A detected by the pallet detection unit 32. Stacking position P is the position on the truck bed 19 where the second and subsequent pallets to be stacked are placed. Stacking position P is the position adjacent to the rear of the existing pallet 17A that is placed at the rearmost position on the truck bed 19.

[0046] The stacking position calculation unit 33 calculates the stacking position P based on the width W of the existing pallet 17A. Specifically, the stacking position calculation unit 33 calculates the stacking position P as a position offset from the existing pallet 17A to the rear of the truck 18 by a distance equal to the width W of the existing pallet 17A plus a specified interval G. In other words, the stacking position calculation unit 33 calculates the stacking position P as a position offset from the existing pallet 17A in a specified direction D1 by a distance equal to the width W of the existing pallet 17A plus a specified interval G. As mentioned above, the width W of the pallet 17B to be stacked is equal to the width W of the existing pallet 17A.

[0047] The route generation unit 34 generates the travel route R of the forklift 2 to the loading position P calculated by the loading position calculation unit 33 (see Figures 5 and 8). The route generation unit 34 generates the travel route R from, for example, the starting position of the forklift 2 to the loading position P. The starting position of the forklift 2 is in front of the existing pallet 17A that is placed at the rearmost position on the loading platform 19.

[0048] Furthermore, the path generation unit 34 generates a travel path R that includes a first straight section R1, a second straight section R2, and a curved section R3 (see Figure 8). The forklift 2 travels in the order of the first straight section R1, the curved section R3, and the second straight section R2.

[0049] The first straight section R1 is a travel section that extends along the specified direction D1 (the longitudinal direction of the truck 18). The second straight section R2 is a travel section that extends along the width direction D2 (the direction perpendicular to the specified direction D1) of the truck 18 toward the loading position P. In this example, the second straight section R2 is connected to the rear end (the rear side of the truck 18) of the first straight section R1 via a curved section R3. The curved section R3 connects the first straight section R1 and the second straight section R2. The curved section R3 connects the rear end of the truck 18 of the first straight section R1 and the end of the second straight section R2 opposite to the loading bed 19 in an arc shape. The curved section R3 is a section for changing the direction of travel of the forklift 2 from the specified direction D1 to the width direction D2.

[0050] When forklift 2 travels through the first straight section R1, it maintains a constant distance from the loading platform 19. Then, by traveling through the second straight section R2 and the curved section R3, it approaches the loading platform 19 and arrives just before the loading position P. Here, just before the loading position P is, for example, the position where the tips of the forks 12 before raising do not come into contact with the loading platform 19.

[0051] The positional deviation calculation unit 35 calculates the lateral deviation Δd and angular deviation Δθ of the forklift 2 relative to the travel path R, which is generated by the path generation unit 34, and the self-position of the forklift 2 estimated by the self-position estimation unit 30 (see Figure 8). The lateral deviation Δd is the amount of deviation of the forklift 2 relative to the travel path R in a direction perpendicular to the travel path R. The angular deviation Δθ is the amount of deviation related to the angle of the direction of travel of the forklift 2 relative to the travel path R.

[0052] The positional displacement direction determination unit 36 ​​determines, based on the travel path R of the forklift 2 and the position of the forklift 2, whether the forklift 2 is shifted toward the existing pallet 17A side or toward the opposite side of the existing pallet 17A relative to the travel path R. In this embodiment, it is assumed that the forklift 2 is shifted toward the opposite side of the existing pallet 17A relative to the travel path R.

[0053] The angle deviation determination unit 37 makes a determination based on the calculation result by the position deviation calculation unit 35. Specifically, the angle deviation Δθ of the forklift 2 calculated by the position deviation calculation unit 35 is determined by a predetermined threshold θ. c We determine whether the value is above or below this threshold θ. c This angle is such that, for example, even if the pallet 17B to be stacked is stacked without considering the angular misalignment Δθ, a sufficient gap is secured between the existing pallet 17A and the pallet 17B to be stacked to allow for the appropriate placement of cushioning material (as described above). c This is not limited to the above and can be set arbitrarily.

[0054] The proximity calculation unit 38 calculates the closest proximity point 17c on the pallet 17B to be stacked, based on the lateral displacement Δd and angular displacement Δθ of the forklift 2 (see Figures 10 and 11). In this example, the proximity calculation unit 38 calculates one of the two corners (angles) on the existing pallet 17A side of the pallet 17B to be stacked as the proximity point 17c. Here, of the two corners on the existing pallet 17A side, the corner on the forklift 2 side (front side) is designated as the front corner 17c1, and the corner on the opposite side of the forklift 2 (back side) is designated as the back corner 17c2.

[0055] The proximity calculation unit 38 uses the lateral displacement Δd, the angular displacement Δθ, and the width W of the stacking target pallet 17B to calculate the position of the corner that is closest in distance to the existing pallet 17A, between the front corner 17c1 and the back corner 17c2, as the proximity section 17c.

[0056] The tracking control unit 39 controls the driving drive unit 24 to make the forklift 2 follow the driving path R in a direction that brings the lateral displacement Δd and angular displacement Δθ of the forklift 2, calculated by the position displacement calculation unit 35, closer to zero.

[0057] Specifically, the tracking control unit 39 performs a first process of controlling the travel drive unit 24 in a direction that brings the lateral displacement Δd of the forklift 2 closer to zero, and a second process of controlling the travel drive unit 24 in a direction that brings the angular displacement Δθ of the forklift 2 closer to zero.

[0058] The loading control unit 40 controls the cargo handling drive unit 25 so that the pallet 17B to be loaded is loaded at the loading position P calculated by the loading position calculation unit 33 after the forklift 2 has reached the position P.

[0059] Specifically, the stacking control unit 40 controls the lift cylinder 13 to raise the forks 12 so that the pallet 17 held by the forks 12 reaches directly above the stacking position P, and also controls the reach cylinder 14 to move the forks 12 forward of the vehicle body 5 (reach out). Subsequently, the stacking control unit 40 controls the lift cylinder 13 to lower the forks 12. The specific processing procedures performed by the stacking control unit 40 will be described later.

[0060] In the stacking control system 1 described above, when stacking pallets 17, the forklift 2 first travels to a pallet storage area (not shown) near the rear of the truck 18 and unloads the pallets 17B to be stacked.

[0061] Specifically, for example, a laser is shone from the laser sensor 23 toward the pallet 17B to be stacked, point cloud data from the laser sensor 23 is acquired, and the position of the pallet 17B to be stacked is detected. Then, the forklift 2 travels to the front of the pallet 17B, and the reach cylinder 14 moves forward so that the forks 12 are inserted into the fork holes 17a (see Figure 6) of the pallet 17B. After that, the lift cylinder 13 raises the forks 12 so that the pallet 17B is held by the forks 12.

[0062] Then, as shown in Figures 4(a) and 4(b), the forklift 2 moves in reverse along one side of the truck 18 until it reaches the front 17b of the existing pallet 17A that is placed on the truck bed 19. At this time, the forklift 2 stops with itself facing sideways to the existing pallet 17A. In this state, a laser is shone from the laser sensor 23 toward the existing pallet 17A, and point cloud data from the laser sensor 23 is acquired.

[0063] Then, based on the point cloud data from the laser sensor 23, the position coordinates of the existing pallet 17A relative to the forklift 2 are calculated. Then, as shown in Figures 5 and 6, the loading position P of the pallet to be loaded 17B on the loading platform 19 is calculated based on the position coordinates of the existing pallet 17A. After that, a travel path R from the tracking start position to the loading position P is generated.

[0064] Here, the loading position P of the pallet 17B to be loaded is offset from the existing pallet 17A by a distance equal to the sum of the width W of the pallet 17 and the specified interval G, on the rear side of the truck 18. If there are multiple existing pallets 17A loaded, the loading position P of the pallet 17B to be loaded is offset from the existing pallet 17A loaded at the rearmost end of the truck bed 19 by a distance equal to the sum of the width W of the pallet 17 and the specified interval G, on the rear side of the truck 18.

[0065] Next, as shown in Figure 5, forklift 2 slightly reverses to the starting position for following, and then travels along the travel path R to just before the loading position P. Specifically, forklift 2 travels sequentially through the first straight section R1, the curved section R3, and the second straight section R2 of the travel path R (see Figure 8). After that, forklift 2 uses the reach cylinder 14 to extend the forks 12 so that the pallet 17B to be loaded, held by the forks 12, reaches directly above the loading position P. Then, as shown in Figure 6, the forks 12 are lowered using the lift cylinder 13, and the pallet 17B to be loaded is placed on the loading position P.

[0066] Referring to Figures 7 to 11, the control processes performed by the controller 26 will be explained in detail. Figure 7 is a flowchart showing the procedure of the processes executed by the controller 26. Figure 7 shows the processes executed by the controller 26 when the pallet to be stacked 17B is stacked at the stacking position P after the travel path R to the stacking position P has been generated by the path generation unit 34.

[0067] First, the controller 26 controls the drive unit 24 to move the forklift 2 toward the loading position P in the order of the first straight section R1, the curved section R3, and the second straight section R2 (procedure S201). At this time, the controller 26 performs a first process to control the drive unit 24 so that the lateral displacement Δd of the forklift 2 approaches zero, and a second process to control the drive unit 24 so that the angular displacement Δθ of the forklift 2 approaches zero.

[0068] Next, the controller 26 determines whether the forklift 2 has reached the loading position P based on the self-position of the forklift 2 estimated by the self-position estimation unit 30 (procedure S202).

[0069] If the controller 26 determines that the forklift 2 has reached the loading position P, it controls the lift cylinder 13 to raise the forks 12 and the reach cylinder 14 to move forward (reach out) until the forks 12 are above the loading position P (procedure S203). If the controller 26 determines that the forklift 2 has not reached the loading position P, it repeats procedure S201.

[0070] After performing procedure S203, the controller 26 calculates the lateral displacement Δd and angular displacement Δθ of the forklift 2 relative to the travel path R, based on the travel path R of the forklift 2 and the position of the forklift 2, as shown in Figure 8 (procedure S204).

[0071] Next, the controller 26 determines that the angular deviation Δθ of the forklift 2 is a predetermined threshold θ c Determine whether it is smaller than (step S205).

[0072] As shown in Figure 9, the controller 26 sets the angular deviation Δθ to the threshold θ. cIf it is determined to be smaller than the specified distance G, the side shift cylinder 16 is controlled based on the lateral displacement Δd of the forklift 2 so that the distance between the existing pallet 17A and the pallet to be loaded 17B becomes the specified distance G, and the lift cylinder 13 is controlled so that the pallet to be loaded 17B is placed on the loading platform 19 (procedure S206).

[0073] Figure 9 shows the forklift 2 in a state where it is not tilted relative to the travel path R (i.e., the angular deviation Δθ of the forklift 2 relative to the travel path R is zero). In Figure 9, the position of the pallet to be loaded 17B before the controller 26 controls the side shift cylinder 16 is shown by a dashed line, and the position of the pallet to be loaded 17B after the controller 26 controls the side shift cylinder 16 is shown by a solid line. The same applies to Figures 10 and 11.

[0074] Specifically, the controller 26 controls the side shift cylinder 16 to move the forks 12 to the existing pallet 17A side by a distance equivalent to the lateral displacement Δd relative to the travel path R of the forklift 2. In addition, the controller controls the lift cylinder 13 to lower the forks 12, thereby placing the pallet 17B to be loaded onto the loading platform 19.

[0075] On the other hand, in step S205, the controller 26, as shown in Figures 10 and 11, sets the angular deviation Δθ to the threshold θ. c If it is determined that the above conditions are met, the nearest adjacent point 17c on the pallet 17B to be stacked is calculated based on the lateral displacement Δd and angular displacement Δθ of the forklift 2 (procedure S207). Specifically, the controller 26 uses the lateral displacement Δd, angular displacement Δθ, and the width W of the pallet 17B to be stacked to calculate the position of the adjacent point 17c, whichever of the front corner 17c1 or rear corner 17c2 is closest to the existing pallet 17A.

[0076] Next, the controller 26 controls the side shift cylinder 16 so that the distance between the proximity section 17c and the existing pallet 17A becomes the specified distance G, and also controls the lift cylinder 13 so that the pallet to be loaded 17B is placed on the loading platform 19 (procedure S208).

[0077] Specifically, the controller 26 controls the side shift cylinder 16 to move the forks 12 in the left-right direction toward the existing pallet 17A so that the distance between the proximity part 17c and the existing pallet 17A becomes the specified distance G. The controller 26 also controls the lift cylinder 13 to lower the forks 12, thereby placing the pallet 17B to be loaded onto the loading platform 19. Procedures S207 and S208 will be explained in more detail below.

[0078] As shown in Figure 10, if the rear corner 17c2 of the pallet 17B to be stacked is located closer to the existing pallet 17A than the front corner 17c1 (i.e., the distance between the rear corner 17c2 and the existing pallet 17A is shorter than the distance between the front corner 17c1 and the existing pallet 17A), the controller 26 calculates the rear corner 17c2 as the adjacent portion 17c (procedure S207). In this case, the controller 26 controls the side shift cylinder 16 so that the distance between the rear corner 17c2 and the existing pallet 17A becomes the specified distance G, and also controls the lift cylinder 13 so that the pallet 17B to be stacked is placed on the loading platform 19 (procedure S208).

[0079] On the other hand, as shown in Figure 11, if the front corner 17c1 of the pallet 17B to be stacked is located closer to the existing pallet 17A than the rear corner 17c2 (i.e., the distance between the front corner 17c1 and the existing pallet 17A is shorter than the distance between the rear corner 17c2 and the existing pallet 17A), the controller 26 calculates the front corner 17c1 as the adjacent portion 17c (procedure S207). In this case, the controller 26 controls the side shift cylinder 16 so that the distance between the front corner 17c1 and the existing pallet 17A becomes the specified distance G, and also controls the lift cylinder 13 so that the pallet 17B to be stacked is placed on the loading platform 19 (procedure S208).

[0080] Here, in the controller 26, the positional deviation calculation unit 35 executes procedure S204. The angle deviation determination unit 37 executes procedure S205. The proximity calculation unit 38 executes procedure S207. The tracking control unit 39 executes procedures S201 and S202. The stacking control unit 40 executes procedures S203, S206 and S208.

[0081] As described above, in this embodiment, the side shift cylinder 16 is controlled to move the forks 12 in the left-right direction of the forklift 2 based on the amount Δd of lateral displacement of the forklift 2 with respect to the travel path R of the forklift 2 to the loading position P of the pallet 17B to be loaded next on the loading platform 19, so that the distance between the existing pallet 17A already placed on the loading platform 19 and the pallet 17B to be loaded becomes a specified distance G. As a result, even if the forklift 2 has lateral displacement with respect to the travel path R when it reaches the loading position P, for example, the side shift cylinder 16 will execute control to move the forks 12 in the left-right direction so that the distance between the existing pallet 17A and the pallet 17B to be loaded becomes a specified distance G. As a result, the pallet to be loaded can be appropriately loaded at a position with a specified distance G between it and the existing pallet 17A.

[0082] Furthermore, in this embodiment, even if there is an angular misalignment Δθ of the forklift 2 with respect to the travel path R, if the angular misalignment Δθ is small, for example, by setting the specified interval G slightly larger, control is performed to move the forks 12 in the left-right direction so that the distance between the existing pallet 17A and the pallet 17B to be stacked becomes the specified interval G, without specifically considering the angular misalignment Δθ. This simplifies the calculation process.

[0083] Furthermore, in this embodiment, because the angular deviation Δθ of the forklift 2 with respect to the travel path R is relatively large, if there is a large difference between the distance between the existing pallet 17A and the front corner 17c1 of the pallet 17B to be stacked, and the distance between the existing pallet 17A and the rear corner 17c2 of the pallet 17B to be stacked, then control is performed to move the forks 12 in the left-right direction of the forklift 2 so that the distance between the closest adjacent part 17c of the pallet 17B to the existing pallet 17A and the existing pallet 17A becomes the specified interval G. This prevents the distance between the pallet 17B to be stacked and the existing pallet 17A from becoming smaller or larger than the specified interval G.

[0084] Figure 12 is a block diagram of the stacking control system 1A according to the second embodiment. Compared to the stacking control system 1 according to the first embodiment, the stacking control system 1A according to the second embodiment is equipped with two distance sensors 50, a relative angle calculation unit 41 that calculates the relative angle of the stacking target pallet 17B with respect to the fork 12, and a proximity calculation unit 38A that calculates the relative angle θ calculated by the relative angle calculation unit 41 based on the lateral displacement Δd and the angular displacement Δθ. r It differs in that it calculates the proximity portion 17c based on the above (see Figure 13). The two distance sensors 50 and the relative angle calculation unit 41 calculate the relative angle θ of the stacking target pallet 17B with respect to the fork 12. r It comprises a relative angle detection unit that detects the angle.

[0085] The two distance sensors 50 are positioned spaced apart in the width direction (left-right direction) of the forklift body 5. For example, the two distance sensors 50 are positioned on the rear surfaces 12a of the two forks 12. Each distance sensor 50 detects the distance from the rear surface 12a of each fork 12 to the front surface of the pallet 17B (the surface facing the rear surface 12a of each fork 12) when the forks 12 are holding the pallet 17B to be stacked.

[0086] As shown in FIG. 13, the relative angle calculation unit 41 calculates the relative angle θ of the pallet 17B to be attached with respect to the fork 12 based on the distances detected by the two distance sensors 50. r The relative angle θ r is, for example, the angle of the front surface of the pallet 17B to be attached with respect to the left - right direction of the forklift 2. When the distances detected by each distance sensor 50 are equal, since the front surface of the pallet 17B to be attached is orthogonal to the fork 12, the relative angle θ r becomes zero.

[0087] When it is determined by the angular deviation determination unit 37 that the angular deviation Δθ is greater than or equal to the threshold value θ c , the lateral deviation amount Δd and the angular deviation Δθ of the forklift 2 with respect to the travel path R, and the relative angle θ r calculated by the relative angle calculation unit 41 (detected by the relative angle detection unit) are used to calculate the proximity portion 17c.

[0088] By the way, when the pallet 17B to be attached is in contact with both of the back surfaces 12a of the two forks 12, the relative angle θ r of the pallet 17B to be attached with respect to the fork 12 becomes zero. However, in order to prevent the fork 12 from contacting the load and causing damage, there may be a case where the load is taken while leaving a gap between the back surface 12a of the fork 12 and the pallet 17B to be attached (see FIG. 13). In this case, the relative angle θ r of the pallet 17B to be attached with respect to the fork 12 may become relatively large.

[0089] On the other hand, in the attachment control system 1A according to the second embodiment, the proximity calculation unit 38A calculates the proximity portion 17c of the pallet 17B to be attached in consideration of the relative angle θ r of the pallet 17B to be attached with respect to the fork 12. For this reason, due to the generation of a gap between the back surface 12a of the fork 12 and the pallet 17B to be attached, the relative angle θ rEven if the size is relatively large, the pallets to be stacked 17B can be properly stacked so that the distance between the adjacent part 17c of the pallet to be stacked 17B and the existing pallet 17A becomes the specified distance G.

[0090] Figure 14 is a block diagram of the stacking control system 1B according to the third embodiment. The stacking control system 1B according to the third embodiment differs from the stacking control system 1 according to the first embodiment in that it includes a designated interval determination unit 42 that determines a designated interval G, and the stacking control unit 40 controls the side shift cylinder 16 so that the distance between the stacking target pallet 17B and the existing pallet 17A becomes the designated interval G determined by the designated interval determination unit 42.

[0091] The designated interval determination unit 42 determines the designated interval G based on the state of the cargo M (see Figure 15) placed on the existing pallet 17A, for example. Specifically, the designated interval determination unit 42 predicts the state of the cargo M relative to the existing pallet 17A based on the width dimension Wm of the cargo M placed on the existing pallet 17A, and determines the designated interval G1 between the existing pallet 17A and the pallet 17B to be stacked. Here, the state of the cargo M relative to the existing pallet 17A is the amount of overhang (protrusion in the width direction) of the cargo M relative to the existing pallet 17A. The width dimension Wm of the cargo M is obtained from information transmitted from the higher-level system management device 27. Note that the amount of overhang of the cargo M in the width direction relative to the existing pallet 17A may be obtained based on point cloud data from the laser sensor 23.

[0092] The designated interval determination unit 42, for example as shown in Figure 15, will determine a different designated interval G for each stacking target pallet 17B if the width dimension Wm of the cargo M obtained from the designated interval determination unit 42 is relatively large and the cargo M extends beyond the existing pallet 17A in the width direction of the existing pallet 17A. In this way, the designated interval determination unit 42 may determine a different designated interval G for each stacking target pallet 17B.

[0093] The stacking control unit 40 controls the side shift cylinder 16 so that the distance between the stacking target pallet 17B and the existing pallet 17A becomes the specified distance G1 determined by the specified distance determination unit 42, and also controls the lift cylinder 13 so that the stacking target pallet 17B is placed on the loading platform 19.

[0094] Even with the stacking control system 1B according to the third embodiment, just like the stacking control system 1 according to the first embodiment, it is possible to appropriately stack the pallet to be stacked 17B at a position with a specified spacing G between it and the existing pallet 17A. Furthermore, even when the cargo M placed on the existing pallet 17A protrudes from the existing pallet 17A in the width direction of the existing pallet 17A, it is possible to prevent the spacing between the cargo M on the existing pallet 17A and the pallet to be stacked 17B from becoming extremely narrow. For example, it is possible to prevent contact between the cargo M placed on the existing pallet 17A and the cargo M (not shown) placed on the pallet to be stacked 17B.

[0095] The present invention is not limited to the above embodiments. In the above embodiments, the controller 26 had an angular displacement determination unit 37, but the invention is not limited to such a configuration, and the controller 26 does not have to have an angular displacement determination unit 37. In this case, the controller 26 may control the side shift cylinder 16 based only on the lateral displacement amount Δd, regardless of the magnitude of the angular displacement Δθ, so that the distance between the existing pallet 17A and the pallet to be stacked 17B becomes a specified distance G. Alternatively, the controller 26 may control the driving unit 24 to cause the forklift 2 to follow the travel path R in a direction that brings the lateral displacement amount Δd of the forklift 2 closer to zero.

[0096] In the above embodiment, the controller 26 had a proximity calculation unit 38, but the controller 26 is not limited to such an embodiment, and the controller 26 does not have to have a proximity calculation unit 38. In this case, the controller 26 uses an angle deviation determination unit 37 to determine when the angle deviation Δθ is a threshold θ cEven if it is determined that the above is true, the side shift cylinder 16 may be controlled based solely on the lateral displacement amount Δd, regardless of the determination of the angle displacement determination unit 37, so that the distance between the existing pallet 17A and the pallet to be stacked 17B becomes the specified distance G. Alternatively, the controller 26 may control the travel drive unit 24 so that the forklift 2 follows the travel path R in a direction that brings the lateral displacement amount Δd of the forklift 2 closer to zero.

[0097] In the above embodiment, the forklift 2 was shifted to the opposite side of the existing pallet 17A relative to the travel path R, but the embodiment is not limited to this configuration, and the forklift 2 may be shifted to the side of the existing pallet 17A relative to the travel path R. In this case, the controller 26 may move the forks 12 in the left-right direction of the forks 12 to the opposite side of the existing pallet 17A by controlling the side shift cylinder 16 so that the distance between the proximity part 17c and the existing pallet 17A becomes a specified distance G.

[0098] In the second embodiment described above, the relative angle detection unit was composed of two distance sensors 50 and a relative angle calculation unit 41, but it is not limited to such a configuration. The relative angle detection unit may also include laser sensors or cameras installed in local infrastructure such as buildings, and the relative angle θ of the stacking target pallet 17B with respect to the fork 12 is used with respect to the data acquired by these laser sensors or cameras. r It may be detected.

[0099] In the third embodiment described above, the designated interval determination unit 42 determined the designated interval G based on the state of the cargo M placed on the existing pallet 17A, but it is not limited to such a configuration. The designated interval determination unit 42 only needs to determine the designated interval G based on the state of the cargo M placed on at least one of the existing pallet 17A and the pallet to be stacked 17B. For example, the designated interval determination unit 42 may determine the designated interval G based only on the amount of overhang of the cargo M placed on the pallet to be stacked 17B. Alternatively, the designated interval determination unit 42 may determine the designated interval G based on the amount of overhang of the cargo M placed on both the existing pallet 17A and the pallet to be stacked 17B.

[0100] Furthermore, in the above embodiment, the forklift 2 has one pair (two) forks 12, but it is not limited to this form and may have multiple forks 12, for example, two pairs (four or more) of forks 12 on the left and right sides.

[0101] Furthermore, in the above embodiment, the pallets 17 are stacked on the cargo bed 19 of the truck 18 in order from the front to the rear of the truck 18, but the configuration is not limited to this. The pallets 17 may also be stacked on the cargo bed 19 of the truck 18 in order from the rear to the front of the truck 18. In addition, the stacking direction of the pallets 17 may be instructed by the higher-level system management device 27.

[0102] Furthermore, in the above embodiment, the widths W of all pallets 17 are equal, but the configuration is not limited to this. If the width W of the next pallet 17B to be stacked is known, multiple pallets 17 with different widths W may be sequentially stacked on the truck bed 19 of the truck 18. In addition, the width information of the next pallet 17B to be stacked may be obtained from the higher-level system management device 27.

[0103] Furthermore, in the above embodiment, the stacking control unit 40 controlled only the cargo handling drive unit 25, but the system is not limited to this configuration, and the stacking control unit 40 may control the travel drive unit 24 in addition to the cargo handling drive unit 25. In this case, for example, the stacking control unit 40 may extend the forks 12 and move the forklift 2 forward so that the pallet 17 held by the forks 12 reaches directly above the stacking position P.

[0104] Furthermore, in the above embodiment, the self-position estimation unit 30 estimated the self-position of the forklift 2 using point cloud data from the laser sensor 21, but it is not limited to this configuration. For example, the self-position estimation unit 30 may estimate the self-position of the forklift 2 using data acquired by laser sensors or cameras installed on infrastructure such as buildings at the site. In this case, the loading control system 1 does not need to be equipped with the laser sensor 21.

[0105] Furthermore, in the above embodiment, the position of the existing pallet 17A was detected by the pallet detection unit 32 after the loading of the pallet 17B was performed, but the system is not limited to this configuration. The pallet detection unit 32 may also detect the position of the existing pallet 17A in advance, before loading the pallet 17B.

[0106] Furthermore, in the above embodiment, the pallets 17 are stacked on the cargo bed 19 of the truck 18, but the cargo bed on which the pallets 17 are stacked is not limited to the truck 18, but may be, for example, a truck berth or the like.

[0107] Furthermore, while forklift 2 is a reach forklift in the above embodiment, it goes without saying that it may also be a counterbalanced forklift. [Explanation of symbols]

[0108] 1,1A,1B...Stacking control system, 2...Forklift, 12...Fork, 13...Lift cylinder, 16...Side shift cylinder, 17...Pallet, 17A...Existing pallet, 17B...Pallet to be stacked, 17c...Proximity unit, 19...Loading platform, 24...Drive unit for travel, 25...Drive unit for cargo handling, 30...Self-position estimation unit, 32...Pallet detection unit, 33...Stacking position calculation unit, 34...Path generation unit, 35...Position deviation calculation unit, 37...Angle deviation judgment unit (judgment unit), 38,38A...Proximity calculation unit, 39...Follow-up control unit, 40...Stacking control unit, 41...Relative angle calculation unit (relative angle detection unit), 42...Specified interval determination unit, 50...Distance sensor (relative angle detection unit), D1...Specified direction, G,G1,G2...Specified interval, M...Cargo, P...Stacking position, R...Travel path, Δd...Lateral deviation amount, Δθ...Angular deviation, θ c ...threshold, θ r ...relative angle.

Claims

1. A stacking control system for stacking pallets sequentially on a loading platform so that they are adjacent to each other in a specified direction, using a forklift having multiple forks for holding pallets, The aforementioned forklift is driven by a drive unit, A cargo handling drive unit including a lift cylinder for raising and lowering the forks, and a side shift cylinder for moving the forks in the left-right direction of the forklift, A self-position estimation unit for estimating the self-position of the forklift, A pallet detection unit that detects the position of an existing pallet already placed on the aforementioned loading platform, A stacking position calculation unit calculates the stacking position of the next pallet to be stacked on the loading platform based on the position of the existing pallet detected by the pallet detection unit, A path generation unit generates the travel path of the forklift to the stacking position calculated by the stacking position calculation unit, A position deviation calculation unit calculates the amount of lateral displacement of the forklift relative to the travel path, based on the travel path of the forklift generated by the path generation unit and the self-position of the forklift estimated by the self-position estimation unit. A tracking control unit controls the driving drive unit to move the forklift along the driving path in a direction that causes the amount of lateral displacement of the forklift calculated by the position displacement calculation unit to approach zero, and The system includes a loading control unit that controls the cargo handling drive unit so that the pallets to be loaded are loaded at the loading position, The stacking control unit controls the side shift cylinder so that the distance between the existing pallet and the pallet to be stacked becomes a specified distance based on the amount of lateral displacement calculated by the position displacement calculation unit, and also controls the lift cylinder so that the pallet to be stacked is placed on the loading platform, thereby creating a stacking control system.

2. The system further includes a determination unit that makes a determination based on the calculation results from the positional deviation calculation unit, The positional displacement calculation unit calculates the amount of lateral displacement and angular displacement of the forklift relative to the travel path, based on the travel path of the forklift and the position of the forklift itself. The tracking control unit controls the driving unit to cause the forklift to follow the driving path in a direction that brings the lateral displacement and angular displacement of the forklift closer to zero. The determination unit determines whether the angular displacement of the forklift calculated by the positional displacement calculation unit is smaller than a predetermined threshold, The stacking control system according to claim 1, wherein the stacking control unit controls the side shift cylinder based on the amount of lateral displacement calculated by the position displacement calculation unit when the determination unit determines that the angular displacement is smaller than the threshold, so that the distance between the existing pallet and the pallet to be stacked becomes the specified distance.

3. The system further includes a proximity calculation unit that calculates the closest proximity point on the stacking target pallet to the existing pallet based on the lateral displacement and angular displacement of the forklift, The stacking control system according to claim 2, wherein the stacking control unit controls the side shift cylinder so that the distance between the proximity unit and the existing pallet, calculated by the proximity calculation unit, becomes the specified distance when the determination unit determines that the angular displacement is greater than or equal to the threshold.

4. The system further includes a relative angle detection unit for detecting the relative angle of the stacking target pallet with respect to the fork, The stacking control system according to claim 3, wherein the proximity calculation unit calculates the proximity portion based on the lateral displacement amount, the angular displacement, and the relative angle detected by the relative angle detection unit, when the determination unit determines that the angular displacement is greater than or equal to the threshold.

5. The system further includes a designated interval determination unit that determines the designated interval based on the condition of the cargo placed on at least one of the existing pallet and the pallet to be stacked, The stacking control system according to claim 1, wherein the stacking control unit controls the side shift cylinder so that the distance between the stacking target pallet and the existing pallet becomes the specified distance determined by the specified distance determination unit.

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