Stacking control system

Abstract

This provides a stacking control system that allows pallets to be stacked at the appropriate angle relative to the loading platform. [Solution] The stacking control system 1 includes a positional displacement calculation unit 35 that calculates the lateral displacement Δd and angular displacement Δθ of the forklift 2 with respect to the travel path R of the forklift 2, a follow control unit 38 that controls the travel drive unit 23 so that the forklift 2 follows the travel path R in a direction that brings the lateral displacement Δd and angular displacement Δθ of the forklift 2 calculated by the positional displacement calculation unit 35 closer to zero, and a stacking control unit 39 that controls the cargo handling drive unit 24 so that the pallet to be stacked 17B is stacked at the stacking position P. The follow control unit 38 stops the first process of controlling the travel drive unit 23 in a direction that brings the lateral displacement Δd closer to zero in the section of the travel path R where the forklift 2 approaches the cargo bed 19, and continues the second process of controlling the travel drive unit 23 in a direction that brings the angular displacement Δθ closer to zero.

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] By the way, when loading pallets onto a truck bed using a forklift, the forklift detects the truck bed, calculates the loading position and the route to the loading position, and moves to the loading position following the calculated route. However, there are cases where the forklift cannot keep up with the route and arrives on the truck bed at an angle to the route, and the forklift loads the pallets in this state. In this case, the pallets are loaded at an angle to the truck bed, which may cause, for example, the corners of the pallets to protrude outside the truck bed, potentially preventing the truck's tailgate from closing. Also, the corners of the pallets being loaded at an angle may come into contact with other pallets.

[0005] The objective of the present invention is to provide a stacking control system that enables pallets to be stacked at an appropriate angle relative to the loading platform when stacking pallets onto the platform using a forklift. [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 loading / unloading drive unit including a lift cylinder for raising and lowering the forks; 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; a path generation unit for generating a driving path for the forklift to the stacking position calculated by the stacking position calculation unit; and the driving path of the forklift generated by the path generation unit. A stacking control system comprising: a position deviation calculation unit that calculates the amount of lateral displacement and angular displacement of the forklift relative to the travel path based on the self-position of the forklift estimated by a 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 brings the amount of lateral displacement and angular displacement of the forklift calculated by the position deviation calculation unit closer to zero; and a stacking control unit that controls the cargo handling drive unit so that the pallets to be stacked are stacked at the stacking position, wherein the follow control unit stops a first process of controlling the travel drive unit in a direction that brings the amount of lateral displacement of the forklift closer to zero in the section of the travel path where the forklift approaches the cargo bed, and continues a second process of controlling the travel drive unit in a direction that brings the angular displacement of the forklift closer to zero.

[0007] In such a loading control system, the position of existing pallets already placed on the loading platform is detected, and based on the position of the existing pallets, the loading position of the next pallet to be loaded onto the loading platform is calculated, and a forklift travel path to the loading position is generated. Then, based on the forklift's travel path and its own position, the amount of lateral displacement and angular displacement of the forklift relative to the travel path is calculated, and the driving unit is controlled to make the forklift follow the travel path in a direction that approaches zero for the amount of lateral displacement and angular displacement. Then, the cargo handling drive unit is controlled so that the pallet to be loaded is loaded at the loading position. However, if, for example, the first process is executed to control the driving unit in a direction that approaches zero for the amount of lateral displacement along the entire travel path, when the distance from the forklift to the loading platform is short, the amount of lateral displacement may not be fully corrected, and the forklift may arrive at the loading platform tilted relative to it. On the other hand, in this invention, in the section of the travel path where the forklift approaches the loading platform, the first process of controlling the drive unit to move the forklift's lateral displacement relative to the travel path toward zero is stopped, and the second process of controlling the drive unit to move the forklift's angular displacement toward zero is continued. This prevents the forklift from arriving at the loading platform tilted relative to it. As a result, pallets can be stacked at an appropriate angle relative to the loading platform.

[0008] (2) In (1) above, the stacking control system further includes a position deviation direction determination unit that determines whether the forklift is deviated toward the existing pallet side or toward the opposite side of the existing pallet relative to the travel path, based on the travel path of the forklift and the position of the forklift, and the follow control unit may control the travel drive unit to stop the travel of the forklift and issue a warning when it determines that the forklift is deviated toward the existing pallet side relative to the travel path.

[0009] In this configuration, if the forklift deviates from its travel path towards the existing pallet, the drive unit is controlled to stop the forklift's movement and an alarm is issued. Therefore, contact between the existing pallet and the pallet to be loaded can be suppressed. In addition, the alarm can alert workers around the forklift to the abnormality.

[0010] (3) In (1) above, the stacking control system further includes a position deviation direction determination unit that determines whether the forklift is shifted toward the existing pallet side or toward the opposite side of the existing pallet relative to the travel path, based on the travel path of the forklift and the position of the forklift, and the cargo handling drive unit further includes a side shift cylinder that moves the forks in the left and right directions of the forklift, and the stacking control unit may, when the position deviation direction determination unit determines that the forklift is shifted toward the opposite side of the existing pallet relative to the travel path, control the side shift cylinder to move the forks toward the existing pallet side and also control the lift cylinder to lower the forks.

[0011] In this configuration, if the forklift is shifted to the opposite side of the existing pallet relative to its travel path, the side shift cylinder is controlled to move the forks towards the existing pallet when the pallet to be loaded is placed in the loading position. Therefore, the pallet to be loaded can be properly placed in the loading position on the loading platform.

[0012] (4) In (3) above, the stacking control system further includes a position displacement amount determination unit that determines whether the amount of lateral displacement of the forklift calculated by the position displacement calculation unit is greater than or equal to a predetermined threshold, and the follow control unit controls the travel drive unit to stop the forklift's movement and issues a warning when the position displacement direction determination unit determines that the forklift is shifted toward the existing pallet relative to the travel path and the position displacement amount determination unit determines that the amount of lateral displacement of the forklift is greater than or equal to a threshold, and the stacking control unit controls the side shift cylinder to move the forks to the opposite side of the existing pallet relative to the travel path and the position displacement amount determination unit determines that the amount of lateral displacement of the forklift is less than a threshold, before reaching the stacking position, and then controls the side shift cylinder to move the forks toward the existing pallet and the lift cylinder to lower the forks at the stacking position.

[0013] In this configuration, the forklift is offset towards the existing pallet relative to its travel path. However, if the amount of lateral offset of the forklift is less than a threshold, the side shift cylinder is controlled to move the forks to the opposite side of the existing pallet just before reaching the loading position. Subsequently, when the pallet to be loaded is placed in the loading position, the side shift cylinder is controlled to move the forks towards the existing pallet. Therefore, even if the forklift is offset towards the existing pallet relative to its travel path, if the amount of lateral offset of the forklift is small, the pallet to be loaded can be properly placed in the loading position on the loading platform without stopping the forklift's movement.

[0014] (5) In any of (1) to (4) above, the loading control system further comprises a plurality of distance sensors arranged spaced apart in the left-right direction of the forklift to detect the horizontal distance to the loading platform, and the positional deviation calculation unit calculates the amount of lateral deviation of the forklift relative to the travel path based on the travel path of the forklift and the position of the forklift, and also calculates the angular deviation of the forklift relative to the travel path based on the travel path of the forklift, the position of the forklift and the horizontal distance to the loading platform detected by the plurality of distance sensors.

[0015] In this configuration, multiple distance sensors are positioned spaced apart from the forklift in the left-right direction and detect the horizontal distance to the loading platform. These sensors are used to calculate the forklift's angular deviation from its travel path. As a result, the angular deviation of the forklift relative to its travel path is obtained with high accuracy. Consequently, pallets can be stacked at a more appropriate angle relative to the loading platform.

[0016] (6) In any of (1) to (5) above, the pallet detection unit detects the position of the existing pallet while the forklift is facing sideways to the existing pallet, the path generation unit generates a path as a travel path that includes a first straight section extending along a specified direction, a second straight section extending in a direction perpendicular to the specified direction toward the stacking position, and a curved section connecting the first straight section and the second straight section, and the follow control unit may stop the first process in the second straight section and continue the second process.

[0017] In such a configuration, after the forklift passes through a first straight section and a curve section that extend along a specified direction, in a second straight section that extends along a direction perpendicular to the specified direction toward the stacking position, a first process of controlling the traveling drive unit in a direction in which the lateral displacement amount of the forklift approaches zero is stopped, and a second process of controlling the traveling drive unit in a direction in which the angular displacement of the forklift approaches zero is continued. Therefore, even when the distance of the second straight section is short, the pallet can be stacked on the loading platform at an appropriate angle. As a result, even in an environment where the space in front of the loading platform is narrow, it is possible to stack the pallet on the loading platform by the forklift.

Effect of the Invention

[0018] According to the present invention, when stacking a pallet on a loading platform by a forklift, the pallet can be stacked at an appropriate angle.

Brief Description of the Drawings

[0019] [Figure 1] It is a block diagram showing the configuration of a 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 in which the position of an existing pallet placed on the loading platform of a truck is detected using a laser sensor mounted on the side of a forklift. [Figure 5] It is a plan view showing a state in which a forklift holding a pallet to be stacked is traveling toward the stacking position. [Figure 6] It is a side view showing a state in which the pallet to be stacked is stacked at the stacking position shown in FIG. 5. [Figure 7] It is a flowchart showing an example of the procedure of the process executed by the controller shown in FIG. 1. [Figure 8] This is a plan view showing a forklift holding a stacking pallet, shifted to the opposite side of the existing pallet relative to the second straight section of the travel path. [Figure 9] This is a plan view showing how a forklift holding a stacking pallet is shifted towards the existing pallet relative to the second straight section of its travel path. [Figure 10] This is a plan view showing how a side-shift cylinder moves a stacking pallet towards an existing pallet. [Figure 11] This is a plan view showing how pallets are stacked on the truck bed at an angle. [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 the pallets to be stacked are stacked with space between them and the existing pallets. [Modes for carrying out the invention]

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 each fork 12 is inserted (see Figure 6). The fork holes 17a extend from the front 17b of pallet 17 to the rear.

[0025] 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, ensuring that there are no gaps. In other words, the loading control system 1 loads the pallets 17 onto the loading bed 19 in order so that they are adjacent to each other in the front-to-back direction (specified direction D1) of the truck 18.

[0026] 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).

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

[0028] The laser sensor 20 is mounted on top of the forklift 2, as shown in Figure 2. The laser sensor 20 is attached, for example, to the roof 5a of the vehicle body 5 via a mounting bracket 27. The laser sensor 20 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 20 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 20 is 360 degrees. As the laser sensor, for example, a 3D LIDAR can be used.

[0030] The map storage unit 21 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 20.

[0031] As shown in Figure 2, the laser sensors 22 are mounted on both sides of the forklift 2 (only the left side is shown in Figure 2). The laser sensors 22 are attached, for example, to the outer surface 28a of a mounting column member 28 erected on the vehicle body 5. The laser sensors 22 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 22 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 22 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 22 hits the entire front surface 17b of the existing pallet 17A. For example, a 3D LIDAR can be used as the laser sensor 22.

[0034] The drive unit 23 is the drive unit that moves the forklift 2. The drive unit 23 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 24 is a drive unit that moves the forks 12. The cargo handling drive unit 24 includes the lift cylinder 13, reach cylinder 14, and side shift cylinder 16, etc.

[0036] The warning device 25 emits a warning to inform workers around the forklift 2 of an abnormality. The warning device 25 may include a display and an alarm. The display includes, for example, a flashing light and a display that shows a warning. The alarm includes, for example, a speaker that emits a siren sound or a buzzer sound.

[0037] 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, a position deviation amount determination unit 37, a follow control unit 38, and a stacking control unit 39.

[0038] The self-position estimation unit 30 estimates the self-position of the forklift 2 based on the point cloud data from the laser sensor 20 and the map data stored in the map storage unit 21. 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 20 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.

[0039] The pallet detection travel control unit 31 controls the travel drive unit 23 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.

[0040] The pallet detection travel control unit 31 controls the travel drive unit 23 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 22 is facing the center of the existing pallet 17A in the width direction.

[0041] 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 22. 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.

[0042] The pallet detection unit 32 works in cooperation with the laser sensor 22 to form a pallet detection unit that detects the position of the existing pallet 17A.

[0043] 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 22 (second laser sensor) (procedure S111).

[0044] 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 22 (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).

[0045] 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 22. 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 22. This gives the position of the existing pallet 17A.

[0046] 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.

[0047] 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 by the width W of the existing pallet 17A to the rear side of the truck 18 relative to the existing pallet 17A. In other words, the stacking position calculation unit 33 calculates the stacking position P as a position offset by the width W of the existing pallet 17A in a specified direction D1 relative to the existing pallet 17A. As mentioned above, the width W of the pallet 17B to be stacked is equal to the width W of the existing pallet 17A.

[0048] 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.

[0049] 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.

[0050] 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 in the first straight section R1 and the end of the second straight section R2 opposite to the cargo bed 19 in an arc shape. The curved section R3 is a section for changing the direction of travel of the truck 18 from the specified direction D1 to the width direction D2.

[0051] 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. Therefore, the second straight section R2 and the curved section R3 are the sections in the travel path R where forklift 2 approaches the loading platform 19. Here, the position just before the loading position P is, for example, the position where the tips of the forks 12 do not come into contact with the loading platform 19 before they are raised.

[0052] The positional deviation calculation unit 35 calculates the lateral deviation Δd (see Figure 8) and angular deviation Δθ (see Figure 11) of the forklift 2 relative to the travel path R, based on the travel path R of the forklift 2 generated by the path generation unit 34 and the self-position of the forklift 2 estimated by the self-position estimation unit 30. 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.

[0053] 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.

[0054] The positional displacement amount determination unit 37 determines that the lateral displacement amount Δd of the forklift 2 calculated by the positional displacement calculation unit 35 is a predetermined threshold d c Determine whether the value is above or below. Here, threshold d c This is, for example, the maximum distance over which the lateral displacement Δd can be corrected by the side shift cylinder 16. Threshold d c This is determined, for example, by the maximum stroke length of the side shift cylinder 16. Note that threshold d c This is not limited to the above and can be set arbitrarily.

[0055] The tracking control unit 38 controls the driving drive unit 23 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.

[0056] Specifically, the tracking control unit 38 performs a first process in which, when the forklift 2 is traveling on the first straight section R1 and curved section R3 of the travel path R (when the forklift 2 is traveling on the first straight section R1 and curved section R3), it controls the travel drive unit 23 in a direction that brings the lateral displacement Δd of the forklift 2 closer to zero, and a second process in which it controls the travel drive unit 23 in a direction that brings the angular displacement Δθ of the forklift 2 closer to zero. On the other hand, when the forklift 2 is traveling on the second straight section R2 of the travel path R (when the forklift 2 is traveling on the second straight section R2), the tracking control unit 38 stops the first process and continues the second process. In other words, the tracking control unit 38 stops the first process and continues the second process in the section of the travel path R where the forklift 2 is approaching the loading platform 19. The specific processing procedures performed by the tracking control unit 38 will be described later.

[0057] The loading control unit 39 controls the cargo handling drive unit 24 so that the pallet 17B to be loaded is loaded at the loading position P after the forklift 2 has reached a position in front of the loading position P calculated by the loading position calculation unit 33.

[0058] Specifically, the stacking control unit 39 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 39 controls the lift cylinder 13 to lower the forks 12. The specific processing procedures performed by the stacking control unit 39 will be described later.

[0059] 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.

[0060] Specifically, for example, a laser is shone from the laser sensor 22 toward the pallet 17B to be stacked, point cloud data from the laser sensor 22 is acquired, and the position of the pallet 17B to be stacked is detected. Then, the reach cylinder 14 moves the forks 12 forward so that they are inserted into the fork holes 17a (see Figure 6) of the pallet 17B to be stacked, and the lift cylinder 13 raises the forks 12 so that the pallet 17B to be stacked is held by the forks 12.

[0061] 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 22 toward the existing pallet 17A, and point cloud data from the laser sensor 22 is acquired.

[0062] Then, based on the point cloud data from the laser sensor 22, 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.

[0063] Here, the loading position P of the pallet 17B to be loaded is offset by the width W of the existing pallet 17A to the rear 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 by the width W of the existing pallet 17 to the rear of the truck 18 to the existing pallet 17A that is loaded at the rearmost end of the truck bed 19.

[0064] 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 a position 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 extends the forks 12 using the reach cylinder 14 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.

[0065] Referring to Figures 7 to 10, 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.

[0066] First, the controller 26 controls the drive unit 23 to move the forklift 2 toward the loading position P in the order of the first straight section R1 and the curved section R3 (procedure S201). At this time, the controller 26 performs a first process to control the drive unit 23 so that the lateral displacement Δd of the forklift 2 approaches zero, and a second process to control the drive unit 23 so that the angular displacement Δθ of the forklift 2 approaches zero.

[0067] Next, the controller 26 determines whether the forklift 2 has passed through the curved section R3 based on the position of the forklift 2 estimated by the self-position estimation unit 30 (procedure S202).

[0068] If the controller 26 determines that the forklift 2 has passed through the curved section R3, it determines whether the forklift 2 has shifted toward the existing pallet 17A side relative to the second straight section R2 of the travel path R, based on the travel path R generated by the path generation unit 34 and the self-position of the forklift 2 estimated by the self-position estimation unit 30 (procedure S203). If the controller 26 determines that the forklift 2 has not passed through the curved section R3, it repeats the above procedure S202.

[0069] As shown in Figure 8, when the controller 26 determines that the forklift 2 is shifted to the opposite side of the existing pallet 17A with respect to the second straight section R2 of the travel path R, it stops the first process of controlling the travel drive unit 23 so that the lateral displacement Δd of the forklift 2 approaches zero, and continues the second process of controlling the travel drive unit 23 so that the angular displacement Δθ of the forklift 2 approaches zero (procedure S204).

[0070] After step S204 is performed, the controller 26 determines whether the forklift 2 has reached the position in front of the loading position P based on the self-position of the forklift 2 estimated by the self-position estimation unit 30 (step S205).

[0071] If the controller 26 determines that the forklift 2 has reached the position in front of 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 S206). If the controller 26 determines that the forklift 2 has not reached the position in front of the loading position P, it repeats the above procedure S204.

[0072] Subsequently, the controller 26 controls the side shift cylinder 16 to move the fork 12 toward the existing pallet 17A, and controls the lift cylinder 13 to lower the fork 12, thereby placing the pallet 17B to be loaded onto the loading platform 19 (procedure S207).

[0073] Specifically, the controller 26 controls the side shift cylinder 16 to move the fork 12 toward the existing pallet 17A so that the pallet 17B to be loaded, held by the fork 12, hits (contacts) the existing pallet 17A, and simultaneously controls the lift cylinder 13 to lower the fork 12, thereby placing the pallet 17B to be loaded onto the loading platform 19 (see Figure 10). By controlling the pallet 17B to be loaded, the gap between the existing pallet 17A and the pallet 17B to be loaded can be brought as close to zero as possible.

[0074] On the other hand, as shown in Figure 9, if the controller 26 determines that the forklift 2 is shifted toward the existing pallet 17A side relative to the second straight section R2, the lateral displacement amount Δd of the forklift 2 calculated by the position displacement calculation unit 35 is set to a predetermined threshold d c Determine whether the above conditions apply (procedure S208).

[0075] The controller 26 determines when the lateral displacement Δd of the forklift 2 is at a threshold d c If it is determined that the size is smaller than the existing pallet 17A, the side shift cylinder 16 is controlled to move the fork 12 to the opposite side of the existing pallet 17A at a position in front of the stacking position P (procedure S209).

[0076] Specifically, the controller 26 moves the forks 12 so that the pallet 17B to be stacked is located on the opposite side of the existing pallet 17A in the specified direction D1. This prevents, for example, the pallet 17B to be stacked from coming into contact with the existing pallet 17A. After executing procedure S209, the controller 26 executes the above procedures S204 to S207.

[0077] In the above procedure S208, the controller 26 determines that the lateral displacement amount Δd of the forklift 2 is at threshold d c If the above is determined, the drive unit 23 is controlled to stop the forklift 2 (procedure S210). The controller 26 also issues a warning using the warning device 25 (procedure S211).

[0078] If the forklift 2 stops due to this control, the controller 26 may perform retry control, which involves moving the forklift 2 away from the loading platform 19 and then controlling the drive unit 23 to move the forklift 2 back to the position in front of the loading position P. Alternatively, retry control by the controller 26 may not be necessary, and the position of the forklift 2 may be corrected by manual operation by a person.

[0079] Here, in the controller 26, the positional displacement direction determination unit 36 ​​executes procedure S203. The positional displacement amount determination unit 37 executes procedure S208. The tracking control unit 38 executes procedures S201, S202, S204, S205, S210, and S211. The stacking control unit 39 executes S206, S207, and S209.

[0080] By the way, as shown in Figure 11, when the tracking control unit performs a first process to control the driving unit 23 in a direction that approaches zero lateral displacement along the entire travel path R, if the distance from the forklift 102 to the loading platform 119 is short (for example, when the second straight section R2 is short), the lateral displacement may not be fully corrected, and the forklift 102 may arrive at the loading platform 119 tilted by Δθ relative to the loading platform 119, and in this state the forklift 102 may load the pallets 117. In this case, because the pallets 117 are loaded diagonally to the loading platform 119, for example, the front corner 117a of the pallet 117 may protrude outside the loading platform 119, which could prevent the truck 118's tailgate (not shown) from closing. Also, because the pallets 117 are loaded diagonally to the loading platform 119, the rear corner 117b of the pallet 117 may come into contact with other pallets 117.

[0081] In response to such a problem, in the present embodiment, in a section where the forklift 2 approaches the loading platform 19 on the travel route R (in this example, the second straight section R2), a first process of controlling the travel drive unit 23 in a direction in which the lateral displacement amount Δd of the forklift 2 with respect to the travel route R approaches zero is stopped, and a second process of controlling the travel drive unit 23 in a direction in which the angular displacement Δθ of the forklift 2 approaches zero is continued. Thereby, it is possible to suppress the forklift 2 from arriving at the loading platform 19 while being tilted with respect to the loading platform 19. As a result, the pallet 17B to be loaded can be loaded on the loading platform 19 at an appropriate angle.

[0082] Further, in the present embodiment, when the forklift 2 is shifted to the opposite side of the existing pallet 17A with respect to the second straight section R2 of the travel route R, the side shift cylinder 16 is controlled so as to move the fork 12 to the side of the existing pallet 17A. Thereby, the pallet 17B to be loaded can be appropriately placed at the loading position P of the loading platform 19.

[0083] Further, in the present embodiment, when the forklift 2 is shifted to the side of the existing pallet 17A with respect to the second straight section R2 of the travel route R and the lateral displacement amount Δd of the forklift 2 is the threshold value d c When it is as described above, the travel drive unit 23 is controlled to stop the travel of the forklift 2, and a warning is issued. Thereby, contact between the existing pallet 17A and the pallet 17B to be loaded can be suppressed. Further, by issuing a warning, for example, an operator around the forklift 2 can be notified of an abnormality.

[0084] Further, in the present embodiment, the forklift 2 is shifted to the side of the existing pallet 17A with respect to the second straight section R2 of the travel route R, but the lateral displacement amount Δd of the forklift 2 is the threshold value d cWhen the amount of lateral displacement Δd of the forklift 2 is small, the side shift cylinder 16 is controlled to move the forks 12 to the opposite side of the existing pallet 17A at a position (in front) of the loading position P. Then, when the pallet 17B to be loaded is loaded at the loading position P, the side shift cylinder 16 is controlled to move the forks 12 towards the existing pallet 17A. As a result, even if the forklift 2 is shifted towards the existing pallet 17A side relative to the second straight section R2, if the amount of lateral displacement Δd of the forklift 2 is small, the pallet 17B to be loaded can be properly placed on the loading position P of the loading platform 19 without stopping the movement of the forklift 2.

[0085] Furthermore, in this embodiment, after the forklift 2 has passed through the first straight section R1 and the curved section R3, in the second straight section R2, the first process of controlling the travel drive unit 23 in a direction that approaches zero the lateral displacement Δd of the forklift 2 is stopped, and the second process of controlling the travel drive unit 23 in a direction that approaches zero the angular displacement Δθ of the forklift 2 is continued. As a result, even if the distance of the second straight section R2 is short, the pallets 17 can be loaded at an appropriate angle to the loading platform 19. Consequently, even in environments where the space in front of the loading platform 19 is narrow, the forklift 2 can load the pallets 17 onto the loading platform 19.

[0086] Furthermore, in this embodiment, the position of the existing pallet 17A is detected after the loading of the pallet 17B to be stacked has been completed. Therefore, the pallet 17B to be stacked can be loaded immediately after the position of the existing pallet 17A has been detected. Consequently, the pallet 17B to be stacked can be placed in a more appropriate position.

[0087] Figure 12 is a block diagram of the stacking control system 1A according to the second embodiment. The stacking control system 1A according to the second embodiment differs in that it further includes two distance sensors 29, and the position deviation calculation unit 35A calculates the angular deviation Δθ of the forklift 2 with respect to the travel path R based on the travel path R, the position of the forklift 2 itself, and the horizontal distance to the loading platform 19 detected by the two distance sensors 29.

[0088] The two distance sensors 29 are positioned spaced apart in the width direction (left-right direction) of the forklift 2's body 5. Specifically, the two distance sensors 29 are positioned at the tips of the two forks 12. Each distance sensor 29 detects the distance from the tip of each fork 12 to the loading platform 19 located in front of the forklift 2 (for example, the side panels of the loading platform 19).

[0089] The positional deviation calculation unit 35A calculates the angular deviation Δθ of the forklift 2 relative to the travel path R, based on the travel path R of the forklift 2, the position of the forklift 2 itself, and the horizontal distance to the loading platform 19 detected by the two distance sensors 29. For example, if the distances detected by each distance sensor 29 are equal, the positional deviation calculation unit 35A determines that the direction of travel of the forklift 2 is perpendicular to the specified direction D1 (parallel to the width direction D2).

[0090] Even with the stacking control system 1A according to the second embodiment, pallets 17 can be stacked at an appropriate angle relative to the loading platform 19, similar to the stacking control system 1 according to the first embodiment. Furthermore, since the angular deviation Δθ of the forklift 2 with respect to the travel path R is calculated using two distance sensors 29, the angular deviation Δθ of the forklift 2 with respect to the travel path R can be obtained with high accuracy. Therefore, pallets 17 can be stacked at an even more appropriate angle relative to the loading platform 19.

[0091] The present invention is not limited to the embodiments described above (the first and second embodiments). For example, as shown in Figure 13, the forklift 2B may stack the pallets to be stacked 17B on the loading platform 19 with a gap between them and the existing pallets 17A. In this case, a cushioning material may be provided in the gap (space) between the existing pallets 17A and the pallets to be stacked 17B. In this case, the stacking control unit 39 does not need to perform collision prevention control.

[0092] In the above embodiment, the controller 26 had a position displacement amount determination unit 37, but it is not limited to such an embodiment, and it does not have to have a position displacement amount determination unit 37. In this case, when the position displacement direction determination unit 36 ​​determines that the forklift 2 is shifted toward the existing pallet 17A with respect to the second straight section R2 of the travel path R, the follow control unit 38 may stop the travel of the forklift 2 and issue a warning, regardless of the magnitude of the lateral displacement amount Δd. That is, when the controller 26 determines in step S203 of Figure 7 that the forklift 2 is shifted toward the existing pallet 17A with respect to the travel path R, it may execute steps S210 and S211 without performing the determination in step S208.

[0093] Even in this case, the pallets 17 can be stacked at an appropriate angle to the loading platform 19, similar to the embodiment described above. Furthermore, if the forklift 2 is deviated from the travel path R towards the existing pallet 17A, the travel drive unit 23 is controlled to stop the forklift 2 from moving, and a warning is issued, thereby preventing contact between the existing pallet 17A and the pallet 17B to be stacked. Additionally, issuing a warning can alert workers around the forklift 2 to the abnormality.

[0094] In the above embodiment, the controller 26 had a positional displacement direction determination unit 36, but it is not limited to such an embodiment, and it does not have to have a positional displacement direction determination unit 36. In this case, the follow control unit 38 may stop the first process described above and continue the second process described above in the section of the travel path R where the forklift 2 approaches the loading platform 19 (for example, the second straight section R2), regardless of whether the forklift 2 has shifted toward the existing pallet 17A side relative to the second straight section R2 of the travel path R. That is, if the controller 26 determines in step S202 that the forklift 2 has passed through the curved section R3, it may execute steps S204 to S207 without making the determination in step S203.

[0095] In the above embodiment, the cargo handling device 4 had a side shift cylinder 16, but it is not limited to such a configuration and may not have a side shift cylinder 16. In this case, the loading control unit 39 does not need to perform stop-and-go control.

[0096] In the above embodiment, the follow control unit 38 stopped the first process and continued the second process in the second straight section R2 of the travel path R, but it is not limited to this configuration. The follow control unit 38 only needs to stop the first process and continue the second process in the section of the travel path R where the forklift 2 approaches the loading platform 19, for example, it may stop the first process and continue the second process in the middle of a curved section R3.

[0097] In the above embodiment, when it was determined that the forklift 2 had shifted toward the existing pallet 17A, control was performed to move the forks 12 to the opposite side of the existing pallet 17A (procedure S209). However, the embodiment is not limited to this form. For example, even if it was determined that the forklift 2 had shifted toward the opposite side of the existing pallet 17A, control may be performed to move the forks 12 to the opposite side of the existing pallet 17A. This control may be performed, for example, after the forklift 2 has reached the loading position P (after procedure S205) and before reaching out (before procedure S206). This makes it possible to prevent the loading pallet 17B from coming into contact with the load on the existing pallet 17A, even if the load placed on the existing pallet 17A extends beyond the existing pallet 17A, by moving the forks 12 to the opposite side of the existing pallet 17A.

[0098] 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.

[0099] Furthermore, in the above embodiment, the pallets 17 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 17 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 addition, the stacking direction of the pallets 17 may be instructed by a higher-level system.

[0100] 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 a higher-level system.

[0101] Furthermore, in the above embodiment, the stacking position calculation unit 33 calculated the stacking position P based on the width W of the pallet 17, but it is not limited to such an embodiment. For example, if the width of the cargo placed on the pallet 17B to be stacked is known and the width of the cargo is greater than the width of the pallet 17B to be stacked, the stacking position calculation unit 33 may calculate the stacking position P based on the width of this cargo. This makes it possible to prevent contact between the cargo placed on the existing pallet 17A and the cargo placed on the pallet 17B to be stacked, even if the cargo placed on the pallet 17B to be stacked extends beyond the pallet 17B. Similarly, the stacking position P may be calculated based on the width of the cargo placed on the existing pallet 17A. Moreover, the stacking position P may be calculated based on the widths of the cargo placed on the existing pallet 17A and the pallet 17B to be stacked, respectively. Information regarding the width of the cargo placed on the existing pallet 17A or the pallet 17B to be stacked may be obtained from a higher-level system.

[0102] Furthermore, in the above embodiment, the stacking control unit 39 controlled only the cargo handling drive unit 24, but the system is not limited to this configuration, and the stacking control unit 39 may control the travel drive unit 23 in addition to the cargo handling drive unit 24. In this case, for example, the stacking control unit 39 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.

[0103] 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 20, but the system 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 a laser sensor 20.

[0104] 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.

[0105] 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.

[0106] 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]

[0107] 1,1A…Stacking control system, 2,2B…Forklift, 12…Fork, 13…Lift cylinder, 16…Side shift cylinder, 17…Pallet, 17A…Existing pallet, 17B…Pallet to be stacked, 19…Loading platform, 23…Drive unit for travel, 24…Drive unit for cargo handling, 29…Distance sensor, 30…Self-position estimation unit, 32…Pallet detection unit, 33…Stacking position calculation unit, 34…Path generation unit, 35,35A…Position deviation calculation unit, 36…Position deviation direction determination unit, 37…Position deviation amount determination unit, 38…Follow-up control unit, 39…Stacking control unit, D1…Specified direction, P…Stacking position, R…Travel path, R1…First straight section, R2…Second straight section, R3…Curve section, Δd…Lateral deviation amount, d c ...threshold, Δθ...angle deviation

Claims

1. A stacking control system for stacking pallets on a loading platform in a specified direction adjacent to each other 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, 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 and angular 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 brings the lateral displacement and angular displacement of the forklift, calculated by the position displacement calculation unit, closer to zero. 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 tracking control unit is a loading control system that, in the section of the travel path where the forklift approaches the loading platform, stops a first process of controlling the driving unit in a direction that brings the lateral displacement of the forklift closer to zero, and continues a second process of controlling the driving unit in a direction that brings the angular displacement of the forklift closer to zero.

2. The system further includes a positional displacement direction determination unit that determines whether the forklift is shifted toward the existing pallet side or toward the opposite side of the existing pallet relative to the travel path of the forklift, based on the travel path of the forklift and the position of the forklift itself. The stacking control system according to claim 1, wherein the tracking control unit controls the drive unit to stop the forklift from moving and issues a warning when it determines that the forklift has deviated toward the existing pallet relative to the travel path.

3. The system further includes a positional displacement direction determination unit that determines whether the forklift is shifted toward the existing pallet side or toward the opposite side of the existing pallet relative to the travel path of the forklift, based on the travel path of the forklift and the position of the forklift itself. The cargo handling drive unit further includes a side shift cylinder that moves the forks in the left-right direction of the forklift, The stacking control system according to claim 1, wherein when the positional displacement direction determination unit determines that the forklift is shifted to the opposite side of the existing pallet with respect to the travel path, the stacking control unit controls the side shift cylinder to move the forks toward the existing pallet and controls the lift cylinder to lower the forks.

4. The system further includes a positional displacement determination unit that determines whether the lateral displacement amount of the forklift calculated by the positional displacement calculation unit is greater than or equal to a predetermined threshold, When the tracking control unit determines, based on the position deviation direction determination unit, that the forklift is deviating toward the existing pallet relative to the travel path, and when the position deviation amount determination unit determines that the lateral deviation amount of the forklift is greater than or equal to the threshold, the tracking control unit controls the travel drive unit to stop the forklift from moving and issues a warning. The stacking control system according to claim 3, wherein the stacking control unit determines, based on the positional displacement direction determination unit, that the forklift is shifted toward the existing pallet relative to the travel path, and the positional displacement amount determination unit determines that the amount of lateral displacement of the forklift is less than the threshold, then controls the side shift cylinder to move the forks to the opposite side of the existing pallet before reaching the stacking position, and then controls the side shift cylinder to move the forks toward the existing pallet at the stacking position, and also controls the lift cylinder to lower the forks.

5. The forklift is further equipped with a plurality of distance sensors, which are spaced apart in the left-right direction and detect the horizontal distance to the loading platform. The loading control system according to claim 1, wherein the positional deviation calculation unit calculates the amount of lateral deviation of the forklift relative to the travel path based on the travel path of the forklift and the position of the forklift, and calculates the angular deviation of the forklift relative to the travel path based on the travel path of the forklift, the position of the forklift and the horizontal distance to the loading platform detected by the plurality of distance sensors.

6. The pallet detection unit detects the position of the existing pallet when the forklift is facing sideways to the existing pallet. The route generation unit generates a route as the travel route that includes a first straight section extending along the specified direction, a second straight section extending in a direction perpendicular to the specified direction toward the loading position, and a curved section connecting the first straight section and the second straight section. The stacking control system according to claim 1, wherein the tracking control unit stops the first process and continues the second process in the second straight section.

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