forklift

Abstract

Reduce the misalignment angle between the mounting section and the pallet. [Solution] The forklift comprises two forks on which pallets are loaded, a first distance meter, a second distance meter positioned separately from the first distance meter in the left-right direction, and a control device. The control device generates a path to a loading position set on a loading area located above the road surface on which the forklift travels, and moves the forklift along the path and places pallets on the loading area. Placing multiple pallets on the loading area from the same direction constitutes one cycle. When placing a pallet for the first time in a cycle, the control device calculates the displacement angle between the loading area and the pallet based on the detected values ​​of the first distance meter and the second distance meter, and when placing a pallet for the second time or later in a cycle, it corrects the path based on the displacement angle previously calculated within the same cycle.

Description

Technical Field

[0001] The present disclosure relates to a forklift.

Background Art

[0002] The forklift disclosed in Patent Document 1 places a load on the cargo bed of a truck. The forklift includes forks, a laser scanner, and a control device. The forklift travels to the vicinity of the truck while holding a pallet on the forks. Then, after moving along the longitudinal direction of the truck, the forklift turns to face the cargo bed directly. The control device calculates the position of the tip of the tailgate of the truck from the detection result of the laser scanner. The control device advances the forklift to a position a predetermined distance before the position of the tip of the tailgate. Then, the control device operates the forks to place the pallet on the cargo bed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] When placing a pallet on the cargo bed, if the forks enter diagonally relative to the edge of the cargo bed, the pallet will be placed diagonally with respect to the longitudinal direction of the truck.

Means for Solving the Problem

[0005] A forklift that solves the above problem is a forklift comprising two forks on which pallets are loaded, a first distance meter, a second distance meter positioned laterally apart from the first distance meter, and a control device, wherein the control device generates a path to a loading position set on a loading area located above the road surface on which the forklift travels, moves the forklift along the path and places the pallets on the loading area, and places multiple pallets on the loading area from the same direction, so that arranging multiple pallets on the loading area constitutes one cycle, the control device calculates the displacement angle between the loading area and the pallets based on the detected values ​​of the first distance meter and the second distance meter when placing the pallets on the loading area for the first time in the cycle, and corrects the path based on the displacement angle previously calculated within the same cycle when placing the pallets on the loading area for the second time and beyond in the cycle.

[0006] The control device corrects the path based on the previously calculated deviation angle within the same cycle. When a forklift places multiple pallets from the same direction, the deviation angle between the loading area and each pallet tends to be similar. Therefore, by correcting the path based on the previously calculated deviation angle, the deviation angle between the loading area and the pallet can be reduced.

[0007] With respect to the above-mentioned forklift, when placing the pallet on the aforementioned placement area, the control device may calculate the displacement angle between the aforementioned placement area and the pallet based on the detected values ​​of the first distance meter and the second distance meter, and then rotate the forklift in place by the amount of the displacement angle before placing the pallet.

[0008] With respect to the above-mentioned forklift, the control device may correct the path when placing the pallet in the aforementioned placement area for the second time or later in the cycle, based on the displacement angle calculated when the pallet was placed in the aforementioned placement area for the first time within the same cycle. [Effects of the Invention]

[0009] According to the present invention, the misalignment angle between the mounting section and the pallet can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a side view of a forklift. [Figure 2] Figure 2 is a perspective view showing a magnified portion of a forklift. [Figure 3] Figure 3 is a perspective view showing a magnified portion of the cargo handling equipment. [Figure 4] Figure 4 is a schematic diagram of a forklift. [Figure 5] Figure 5 is a plan view of the truck. [Figure 6] Figure 6 is a magnified view of the stepped section and the side panel. [Figure 7] Figure 7 is a flowchart showing the control when placing the pallet for the first time. [Figure 8] Figure 8 shows the deviation in the entry angle of the fork relative to the mounting surface. [Figure 9] Figure 9 shows the relationship between the rangefinder's detected value and time. [Figure 10] Figure 10 is a flowchart showing the control when placing a pallet for the second time or later. [Figure 11] Figure 11 is a plan view of a forklift and a truck. [Figure 12] Figure 12 shows the relationship between the moving average difference of the rangefinder's detected values ​​and time. [Modes for carrying out the invention]

[0011] A first embodiment of the forklift will be described below. In the following description, front, back, left, right, up, and down refer to the front, back, left, right, up, and down relative to the forklift unless otherwise specified. <Forklift> As shown in Figure 1 and Figure 2, the forklift 10 is a reach-type forklift. The forklift 10 automatically performs cargo handling operations.

[0012] The forklift 10 includes a vehicle body 11, two reach legs 12, two front wheels 13, a rear wheel 14, a head guard 15, and a cargo handling device 21. The two reach legs 12 are disposed spaced apart from each other in the left-right direction. The reach legs 12 extend forward from the vehicle body 11. One front wheel 13 is provided on each reach leg 12. The rear wheel 14 is disposed on the vehicle body 11. The rear wheel 14 is a steering wheel. The rear wheel 14 is a drive wheel. The head guard 15 is disposed above the vehicle body 11.

[0013] The cargo handling device 21 is disposed in front of the vehicle body 11. The cargo handling device 21 includes a mast 22, a lift bracket 25, two forks 26, a lift cylinder 31, and a reach cylinder 32.

[0014] The mast 22 is a multi-stage mast. The mast 22 includes an outer mast 23 and an inner mast 24. The inner mast 24 is provided so as to be able to move up and down relative to the outer mast 23.

[0015] The lift bracket 25 is provided so as to be able to move up and down relative to the inner mast 24. The two forks 26 are fixed to the lift bracket 25. As shown in Figure 3, the two forks 26 are disposed spaced apart from each other in the left-right direction. One of the two forks 26 is defined as a first fork 26L, and the other is defined as a second fork 26R. The first fork 26L is, for example, the left fork. The second fork 26R is, for example, the right fork. The fork 26 includes a support portion 27. The support portion 27 extends in the front-rear direction. The support portion 27 has a plate shape.

[0016] As shown in Figure 1, a pallet P is loaded onto the fork 26. The pallet P has holes H. With the support part 27 inserted into the holes H, the upper surface of the support part 27 supports the pallet P, thereby loading the pallet P onto the fork 26.

[0017] The lift cylinder 31 is a hydraulic cylinder. The lift bracket 25 moves up and down by supplying and discharging hydraulic fluid to the lift cylinder 31. The fork 26 moves up and down together with the lift bracket 25.

[0018] The reach cylinder 32 is a hydraulic cylinder. The mast 22 moves in the forward and backward directions by supplying and discharging hydraulic fluid to the reach cylinder 32. The fork 26 moves in the forward and backward directions together with the mast 22.

[0019] As shown in Figure 3, the cargo handling device 21 is equipped with a side shift device 41. The side shift device 41 comprises two finger bars 42 and 43, a shifter 44, and a shift cylinder 45. The two finger bars 42 and 43 are spaced apart in the vertical direction.

[0020] The shifter 44 is mounted to be movable left and right relative to the two finger bars 42 and 43. The shifter 44 comprises two shifter bars 46 and 47 and two connecting members 48 and 49 that connect the two shifter bars 46 and 47. The two shifter bars 46 and 47 are spaced apart in the vertical direction. The two connecting members 48 and 49 are spaced apart in the horizontal direction. The connecting members 48 and 49 connect the ends of the shifter bars 46 and 47. The fork 26 is connected to the shifter bars 46 and 47.

[0021] The shift cylinder 45 is a hydraulic cylinder. The shifter 44 moves left and right by supplying and discharging hydraulic fluid to the shift cylinder 45. The forks 26 also move left and right along with the shifter 44. The side shift device 41 moves the forks 26 left and right while maintaining the distance between the two forks 26.

[0022] As shown in Figure 4, the forklift 10 comprises a drive mechanism 51 and a hydraulic mechanism 52. The drive mechanism 51 is a component for driving the forklift 10. The drive mechanism 51 includes a drive source for driving the rear wheels 14 and a steering mechanism for steering the rear wheels 14. If the forklift 10 uses a motor as its drive source, the drive mechanism 51 includes a motor driver. If the forklift 10 uses an engine as its drive source, the drive mechanism 51 includes a fuel injection device.

[0023] The hydraulic mechanism 52 is a component for controlling the supply and discharge of hydraulic fluid to the hydraulic equipment. The hydraulic equipment includes a lift cylinder 31, a reach cylinder 32, and a shift cylinder 45. The hydraulic mechanism 52 includes a pump for discharging hydraulic fluid and a control valve for controlling the supply and discharge of hydraulic fluid to the hydraulic equipment. The material handling device 21 operates through the supply and discharge of hydraulic fluid by the hydraulic mechanism 52.

[0024] The forklift 10 is equipped with an external sensor 61. The external sensor 61 detects the position of an object in a three-dimensional coordinate system. The external sensor 61 is, for example, a millimeter-wave radar, a stereo camera, a ToF (Time of Flight) camera, or a LIDAR (Laser Imaging Detection and Ranging). In this embodiment, a LIDAR is used as the external sensor 61. The external sensor 61 emits lasers in multiple directions. The external sensor 61 derives the distance to a point by receiving the reflected light reflected from the point where the laser strikes using a photodetector. The point where the laser strikes represents a part of the surface of an object. The position of the point can be expressed in polar coordinates. The coordinates of the point in polar coordinates are converted to coordinates in Cartesian coordinates. The external sensor 61 derives the coordinates of the point in the sensor coordinate system. The sensor coordinate system is a three-axis Cartesian coordinate system with the external sensor 61 as the origin. The external sensor 61 is often placed at a high location so that the laser is not obstructed. For example, the external sensor 61 is located on the head guard 15.

[0025] The forklift 10 includes a first distance meter 62 and a second distance meter 63. The distance meters 62 and 63 are, for example, laser distance meters. The distance meters 62 and 63 detect the distance to the point where the laser strikes by receiving reflected light from the point where the laser strikes. If the distance meters 62 and 63 cannot receive reflected light despite irradiating with a laser, the measured value is set to infinity. An infinity measured value means that there is no point within the measurable distance of the distance meters 62 and 63 where the laser strikes. In this embodiment, the distance meters 62 and 63 are one-dimensional distance meters capable of detecting distance in only one direction.

[0026] The distance meters 62 and 63 are attached to the cargo handling device 21. More specifically, the distance meters 62 and 63 are attached to a point that moves up and down together with the forks 26. For example, the distance meters 62 and 63 are attached to the forks 26.

[0027] The second distance meter 63 is positioned separately from the first distance meter 62 in the left-right direction. The first distance meter 62 is located on the support portion 27 of the first fork 26L. The second distance meter 63 is located on the support portion 27 of the second fork 26R. The distance from the tip of the support portion 27 of the first fork 26L to the first distance meter 62 is the same as the distance from the tip of the support portion 27 of the second fork 26R to the second distance meter 63. In other words, the first distance meter 62 and the second distance meter 63 are located at the same position in the front-rear direction.

[0028] The two distance meters 62 and 63 are arranged such that the lasers emitted from the first distance meter 62 and the lasers emitted from the second distance meter 63 are directed downwards. Therefore, the distance meters 62 and 63 detect the distance to objects below them. The distance meters 62 and 63 are arranged such that the lasers are not obstructed by the pallet P even when the support portion 27 is supporting the pallet P. For example, the distance meters 62 and 63 may be provided in the portion of the support portion 27 that is not inserted into the hole H. The laser emitted from the first distance meter 62 and the laser emitted from the second distance meter 63 are parallel to each other. In this embodiment, "parallel" and "identical" mean that errors caused by dimensional tolerances of each component and mounting of each component are tolerant.

[0029] The forklift 10 is equipped with a reach sensor 64. The reach sensor 64 detects the reach. The reach is the amount of forward movement of the forks 26, with the state where the forks 26 are closest to the vehicle body 11 being defined as 0. In other words, the reach is the distance the forks 26 have moved forward.

[0030] The forklift 10 is equipped with a camera 65 and a pallet detection sensor 66. The camera 65 is, for example, a monocular camera. The camera 65 takes images and generates image data. The camera 65 is mounted to take images of the side of the forklift 10.

[0031] The pallet detection sensor 66 is a sensor for detecting pallet P. The pallet detection sensor 66 is a sensor that can detect the position of an object in a three-dimensional coordinate system. The pallet detection sensor 66 can use a sensor similar to the external sensor 61, for example.

[0032] The control device 71 comprises a processor 72 and a storage unit 73. The processor 72 is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a DSP (Digital Signal Processor). The storage unit 73 includes RAM (Random access memory) and ROM (Read Only Memory). The storage unit 73 stores program code or instructions configured to cause the processor to execute processing. The storage unit 73, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 71 may be composed of hardware circuits such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control device 71, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as an ASIC or FPGA, or a combination thereof.

[0033] The control device 71 acquires point cloud data from the external sensor 61. Point cloud data is point data representing the position of an object in a 3D coordinate system. That is, point cloud data is a set of coordinates in the sensor coordinate system. The control device 71 acquires the detection values ​​from the distance meters 62 and 63. The detection values ​​from the distance meters 62 and 63 are the distances to the object detected by the distance meters 62 and 63. The control device 71 acquires the reach amount from the reach amount sensor 64. The control device 71 acquires image data from the camera 65. The control device 71 acquires point cloud data from the pallet detection sensor 66.

[0034] The forklift 10 is equipped with an auxiliary storage device 74. The auxiliary storage device 74 is a non-volatile storage device that can rewrite data. The auxiliary storage device 74 is, for example, a hard disk drive or a solid-state drive.

[0035] The auxiliary storage device 74 stores map data M1 that shows the environment in which the forklift 10 is used. The map data M1 is information about the physical structure of the environment in which the forklift 10 is used, such as the shape of objects in the environment and the size of the environment. In this embodiment, the map data M1 is data that represents the structure of the environment in which the forklift 10 is used in coordinates of a map coordinate system. The map coordinate system is, for example, a two-axis Cartesian coordinate system. The map coordinate system is a coordinate system with an arbitrary point as the origin.

[0036] The control device 71 estimates the self-position of the forklift 10. The self-position is the coordinates of a point on the map coordinate system of the forklift 10. This point on the forklift 10 can be arbitrary, but for example, it is the horizontal center position of the forklift 10.

[0037] Self-position estimation is performed by comparing point cloud data acquired from the external sensor 61 with map data M1. The control device 71 extracts landmarks with the same shape as the landmarks obtained from the point cloud data from the map data M1. The control device 71 recognizes the position of the landmarks from the map data M1. The positional relationship between the position of the landmarks and the forklift 10 can be determined from the detection results of the external sensor 61. Therefore, the control device 71 can estimate its own position by recognizing the position of the landmarks. Landmarks are objects with features that can be identified by the external sensor 61. Landmarks are physical structures whose position does not change easily. Self-position estimation may be performed by combining self-position estimation using the external sensor 61 with dead reckoning using internal sensors. Self-position estimation may be performed by combining self-position estimation using the external sensor 61 with self-position estimation using satellite signals transmitted from GNSS (Global Navigation Satellite System) satellites.

[0038] The control device 71 controls the driving motion. The control device 71 drives the forklift 10 by controlling the drive mechanism 51. The control device 71 controls the cargo handling motion. The control device 71 causes the cargo handling device 21 to perform cargo handling operations by controlling the hydraulic mechanism 52. The cargo handling operations in this embodiment include a lift operation to raise and lower the forks 26, and a reach operation to move the forks 26 forward or backward.

[0039] The forklift 10 performs loading. Loading is the action of placing the pallet P loaded on the forks 26 onto the loading target. As shown in Figure 5, the cargo storage object in this embodiment is a truck 100. The truck 100 is, for example, a wing truck or a flatbed truck. The truck 100 comprises a truck head 101, a cargo bed 102, and two side panels 105 and 106. The cargo bed 102 is located behind the truck head 101 in the longitudinal direction of the truck 100. The side panels 105 and 106 are provided on both sides of the cargo bed 102. The side panels 105 and 106 include a left side panel 105, which is located on the left side of the cargo bed 102 in the lateral direction of the truck 100, and a right side panel 106, which is located on the right side of the cargo bed 102 in the lateral direction of the truck 100. The upper surface of the cargo bed 102 is a loading area 103 on which the pallet P is placed. The loading area 103 is located above the road surface on which the forklift 10 travels.

[0040] As shown in Figure 6, the cargo bed 102 is provided with a stepped section 104. The stepped section 104 is located below the loading section 103. The stepped section 104 is provided along the side ends E1, which are the ends on both sides of the loading section 103. When loading is performed, at least one of the side panels 105, 106 is open. That is, at least one of the side panels 105, 106 is rotated below the loading section 103. When the side panels 105, 106 are open, a gap 107 is created between the cargo bed 102 and the side panels 105, 106.

[0041] When placing pallets P on the loading section 103, multiple pallets P are arranged side by side. For example, as shown in Figure 5, pallet P1 is placed along the left side 105 and pallet P2 is placed along the right side 106. In this case, the pallet P1 placed along the left side 105 and the pallet P2 placed along the right side 106 are arranged in the front-to-back direction of the truck 100. When placing pallet P1 along the left side 105, the forklift 10 approaches the truck 100 from the left and places pallet P1. When placing pallet P2 along the right side 106, the forklift 10 approaches the truck 100 from the right and places pallet P2.

[0042] Placing multiple pallets P on the loading section 103 from the same direction constitutes one cycle. "Same direction" means that when placing pallets P on the loading section 103, the forklift 10 approaches the loading section 103 from the same direction. In the example shown in Figure 5, one cycle involves approaching the truck 100 from the left and placing three pallets P1. Another cycle involves approaching the truck 100 from the right and placing three pallets P2.

[0043] This section describes the cargo handling control performed by the control device 71 when the forklift 10 places cargo. The cargo handling control includes control performed when the pallet P is placed for the first time, and control performed when the pallet P is placed for the second time or later. Once one cycle is completed, the cargo handling control ends. That is, the following cargo handling controls are performed within the same cycle.

[0044] <When placing the palette for the first time> As shown in Figure 7, in step S1, the control device 71 detects the truck 100. The forklift 10 travels along the side panels 105 and 106 of the truck 100 in the longitudinal direction of the truck 100. The control device 71 detects the truck 100 using point cloud data acquired from the external sensor 61 while the forklift 10 is traveling. For example, the control device 71 detects the top surface of the cargo bed 102 from the point cloud data. The top surface of the cargo bed 102 can be detected, for example, by a method that extracts a horizontal plane from the point cloud data. The method for detecting the truck 100 is arbitrary. For example, the control device 71 may detect the truck 100 from image data acquired from the camera 65 by using object recognition using machine learning.

[0045] Next, in step S2, the control device 71 generates a path. The path indicates the position and orientation of the forklift 10. As shown in Figure 5, the generated path R is the path to the loading position set on the loading section 103. Path R includes a first path R1 extending along the side panels 105 and 106 of the truck 100, and a second path R2 extending from the first path R1 toward the loading position. The first path R1 includes a path Rs extending in the front-rear direction of the truck 100, and a path Rc curving from path Rs toward the second path R2. The second path R2 is the path extending in the left-right direction of the truck 100. The loading position is set at a position on the loading section 103 where a pallet P can be placed. When placing pallets P sequentially from the front to the rear of the truck 100, the loading position may be set as close as possible to the truck head 101. The loading position is, for example, a position that coincides with the center of the front of the pallet P when the pallet P is placed on the loading section 103. That is, the loading position is the target position of the center of the front of the pallet P. The front of pallet P is the surface that faces the forklift 10 when pallet P is being transported by the forklift 10.

[0046] Next, in step S3, the control device 71 performs an approach. The approach is the process of moving the forklift 10 to the front of the loading position. The control device 71 controls the drive mechanism 51 while knowing its own position, causing the forklift 10 to travel so that it follows the first path R1.

[0047] Next, in step S4, the control device 71 moves the forklift 10 forward. The control device 71 controls the drive mechanism 51 while knowing its own position, causing the forklift 10 to travel along the second path R2. As a result, the forklift 10 approaches the loading position.

[0048] Next, in step S5, the control device 71 performs angular misalignment detection. Angular misalignment detection means calculating the misalignment angle θ1 between the mounting section 103 and the pallet P. The misalignment angle θ1 is the angle of the front surface of the pallet P with respect to the front-rear direction of the track 100. The misalignment angle θ1 is caused by a misalignment in the entry angle of the forks 26 relative to the mounting section 103. When the forks 26 are moved to the upper part of the mounting section 103, the misalignment angle θ1 occurs when the two forks 26 enter the side end E1 at an angle.

[0049] As shown in Figure 8, the deviation θ2 of the entry angle of the fork 26 relative to the mounting section 103 is the angle of the line segment L1 relative to the side end E1. The line segment L1 is the line segment connecting the tips of the two support sections 27. When the fork 26 enters perpendicular to the side end E1, the deviation θ2 of the entry angle of the fork 26 is 0. The deviation θ2 of the entry angle of the fork 26 relative to the mounting section 103 can be considered to be the same as the deviation angle θ1. Therefore, by detecting the deviation θ2 of the entry angle of the fork 26 relative to the mounting section 103, the deviation angle θ1 can be detected. Angle deviation detection is performed using the detected values ​​of the first distance meter 62 and the second distance meter 63.

[0050] The control device 71 raises the support section 27 to a position higher than the mounting section 103 and moves the forks 26 forward toward the loading position. For example, the control device 71 moves the mast 22 forward by the reach cylinder 32 by controlling the hydraulic mechanism 52. The control device 71 may also move the forklift 10 forward by controlling the drive mechanism 51.

[0051] As the forklift 26 passes over the tops of the side panels 105, 106 and the cargo bed 102, the first distance meter 62 and the second distance meter 63 detect distances that conform to the shapes of the side panels 105, 106 and the cargo bed 102.

[0052] As shown in Figure 9, before the distance meters 62 and 63 reach the top of the tailgates 105 and 106, the distance meters 62 and 63 detect the distance to the ground. At the location where the truck 100 stops, the ground is often relatively flat, and the change in distance detected by the distance meters 62 and 63 is minimal while the distance to the ground is being detected.

[0053] At the first time point t1, when distance meters 62 and 63 reach the top of the tailgates 105 and 106, distance meters 62 and 63 detect the distance to the tailgates 105 and 106. As the forks 26 move, distance meters 62 and 63 detect the distance following the slope of the tailgates 105 and 106. The tailgates 105 and 106 are sloped so that they move away from the cargo bed 102 as they move from the top to the bottom. Therefore, as the forks 26 move, distance meters 62 and 63 move closer to the top of the tailgates 105 and 106 from the bottom, and the distance detected by distance meters 62 and 63 decreases.

[0054] At the second time point t2, when distance meters 62 and 63 reach the top of gap 107, distance meters 62 and 63 detect the distance to the ground. At the third time point t3, when the distance meters 62 and 63 reach the top of the stepped section 104, they detect the distance to the stepped section 104. Since the stepped section 104 is located above ground level, the distance detected by the distance meters 62 and 63 is short. Because the stepped section 104 has little elevation change, the change in the distance detected by the distance meters 62 and 63 while detecting the distance to the stepped section 104 is minimal.

[0055] Thus, the detected values ​​by the distance meters 62 and 63 change depending on the positional relationship between the distance meters 62 and 63 and the track 100. Therefore, the positional relationship between the distance meters 62 and 63 and the track 100 can be determined from the detected values ​​of the distance meters 62 and 63. For example, at the first time step t1, the distance detected by the distance meters 62 and 63 becomes shorter, so by setting a threshold for the detected values ​​of the distance meters 62 and 63, it can be determined that the distance meters 62 and 63 have begun to detect the distance to the slopes 105 and 106. Alternatively, a threshold can be set for the difference between the current value and the previous value of the detected values ​​of the distance meters 62 and 63. Changes also occur in the detected values ​​of the distance meters 62 and 63 at the second time step t2 and the third time step t3. Therefore, by setting a threshold for the detected values ​​of the distance meters 62 and 63, or by setting a threshold for the difference between the current value and the previous value of the detected values ​​of the distance meters 62 and 63, it is possible to determine the start of detection of the gap 107 and the start of detection of the step 104. In this way, the locations where the positions of rangefinders 62 and 63 can be determined from the detected values ​​of rangefinders 62 and 63 are designated as feature points.

[0056] The smaller the deviation θ2 in the entry angle of the fork 26, the smaller the difference between the time when the feature point is detected by the first rangefinder 62 and the time when the feature point is detected by the second rangefinder 63. Specifically, the smaller the deviation θ2 in the entry angle of the fork 26, the smaller the difference between the first time t1, the second time t2, and the third time t3 between the first rangefinder 62 and the second rangefinder 63.

[0057] The control device 71 calculates the elapsed time by subtracting the time when the first feature point was detected by the first distance meter 62 and the second distance meter 63 from the time when the feature point was detected later. The control device 71 calculates the travel distance X1 as the product of the calculated elapsed time and the travel speed of the fork 26. Then, the control device 71 calculates the deviation θ2 of the entry angle from equation (1).

[0058] The deviation in the entry angle θ² = sin -1 (Movement distance X1 / Separation distance Z)…(1) The separation distance Z is the distance between the first distance meter 62 and the second distance meter 63. Since the separation distance Z is a known value, it can be stored in advance in a memory medium that the control device 71 can read. The travel speed of the forks 26 is the travel speed of the forklift 10 when the forks 26 are moved by the movement of the forklift 10. The travel speed of the forks 26 is the travel speed of the mast 22 when the forks 26 are moved by a reach operation. The travel speed of the forklift 10 can be obtained from the speedometer. The travel speed of the mast 22 can be calculated from the detected value of the reach sensor 64.

[0059] The control device 71 may calculate the travel distance X1 by odometry. For example, the control device 71 starts odometry measurement when one of the first distance meter 62 and the second distance meter 63 detects a feature point. Once odometry measurement has started, the control device 71 accumulates the amount of movement of the fork 26. For example, the control device 71 may accumulate the reach amount obtained from the reach amount sensor 64. The control device 71 may also accumulate the amount of movement using an encoder that detects the rotation speed of the front wheel 13. The control device 71 ends odometry measurement when the other of the first distance meter 62 and the second distance meter 63 detects a feature point. As a result, the amount of movement accumulated from the time one of the two distance meters 62 and 63 detects a feature point until the other detects a feature point is calculated as the travel distance X1.

[0060] Next, in step S6, the control device 71 detects the edge of the cargo bed. The edge of the cargo bed is the upper end of the side panels 105, 106, or the stepped portion 104. The edge of the cargo bed can be detected from either the detected value of the first distance meter 62 or the detected value of the second distance meter 63. The control device 71 may detect the edge of the cargo bed using the detected value of the first distance meter 62, or it may detect the edge of the cargo bed using the detected value of the second distance meter 63. The control device 71 may also detect the edge of the cargo bed by detecting the feature points described above. As an example, the case in which the upper ends of the side panels 105, 106 are detected using a first linear function f1 and a second linear function f2 will be described.

[0061] The first linear function f1 is a linear function that represents the change over time of the detected values ​​obtained from the time the distance meters 62 and 63 began detecting the distance to tilt 105 and 106 until the second timing, which is a predetermined time before the first timing when the latest detected value was obtained. The second linear function f2 is a linear function that represents the change over time of the detected values ​​obtained until the first timing, from the second timing onward. The first linear function f1 and the second linear function f2 can be calculated, for example, by the least squares method.

[0062] While the distances to the sides of the tilt panels 105 and 106 are detected by the distance meters 62 and 63, the slopes of the first linear function f1 and the second linear function f2 are identical. When the distances to the top of the tilt panels 105 and 106 are detected by the distance meters 62 and 63, the change in the detected values ​​of the distance meters 62 and 63 becomes small, causing a difference to occur between the slopes of the first linear function f1 and the second linear function f2.

[0063] The control device 71 identifies the intersection point of the first linear function f1 and the second linear function f2 when the difference between the slopes of the first linear function f1 and the second linear function f2 exceeds a predetermined value. The control device 71 identifies the positions of the distance meters 62 and 63 at the timing of the identified intersection point as the upper ends of the tilt beams 105 and 106. The predetermined value is set so that the difference between the slopes of the first linear function f1 and the second linear function f2 can be determined by detecting the upper ends of the tilt beams 105 and 106.

[0064] Next, in step S7, the control device 71 stops the forks 26. If the forklift 10 is moving, the control device 71 stops the forklift 10. If the mast 22 is moving forward by the reach operation, the control device 71 stops the reach operation.

[0065] Next, in step S8, the control device 71 performs a turn in place of the forklift 10 so that the deviation in the entry angle falls within the allowable range. For example, the control device 71 performs a turn in place by the amount of the deviation in the entry angle θ2 detected in step S5. If the forks 26 are tilted to the left relative to the loading platform 102, the control device 71 turns the forklift 10 to the right by the amount of the deviation in the entry angle θ2. If the forks 26 are tilted to the right relative to the loading platform 102, the control device 71 turns the forklift 10 to the left by the amount of the deviation in the entry angle θ2. Turning in place is an action in which the two front wheels 13 and rear wheels 14 are used as steering wheels and the forklift turns in place, that is, turns in a circular motion. The control device 71 does not have to perform a turn in place if the deviation in the entry angle θ2 detected in step S5 falls within the allowable range. The allowable range can be set arbitrarily.

[0066] Next, in step S9, the control device 71 performs a cargo handling operation. The control device 71 places the pallet P at the loading position by operating the cargo handling device 21. For example, the control device 71 places the pallet P at a predetermined distance from the edge of the loading bed in the depth direction of the loading bed 102. The predetermined distance is set so that the pallet P does not interfere with the side panels 105 and 106 when the pallet P is placed at the loading position. The control device 71 places the pallet P at the loading position by advancing the forks 26 so that the pallet P is positioned above the loading position, and then lowering the forks 26. The control device 71 may also move the pallet P towards the truck head 101 by side-shifting the forks 26 using the side-shift device 41.

[0067] <When placing a palette for the second time or later> The control performed by the control device 71 when placing pallet P for the second time or later will be explained. As shown in Figure 10, in step S11, the control device 71 detects the pallet P. Detecting the pallet P involves detecting the pallet P already placed on the mounting section 103. The control device 71 detects the pallet P using the detection results from the camera 65 and the detection results from the pallet detection sensor 66. The control device 71 acquires image data from the camera 65. Based on the image data, the control device 71 recognizes the pallet P. The control device 71 recognizes the pallet P using, for example, image processing technology utilizing machine learning.

[0068] The control device 71 extracts point cloud data corresponding to pallet P from the point cloud data acquired from the pallet detection sensor 66. This enables detection of pallet P. The position of pallet P is, for example, the 3D coordinate of the center of the front surface of pallet P. The position of the external sensor 61 and the position of the pallet detection sensor 66 are different. The control device 71 may convert the position of pallet P with the pallet detection sensor 66 as the origin to the position of pallet P with the external sensor 61 as the origin, based on the difference between the position of the external sensor 61 and the position of the pallet detection sensor 66.

[0069] Next, in step S12, the control device 71 generates a path R. When placing a pallet P for the second time or later, the placement position may be a predetermined distance away from the pallets P already placed on the loading platform 102 in the longitudinal direction of the truck 100. For example, the placement position is a predetermined distance away from the rear of the truck 100 from the center of the front of the rearmost pallet P already placed on the loading platform 102. The predetermined distance is set so that adjacent pallets P do not interfere with each other when placed at the placement position. The predetermined distance is, for example, the width of the pallet P plus a margin.

[0070] The path R generated in step S12 is the path R corrected by the deviation θ2 of the approach angle detected when the pallet P was placed for the first time, i.e., the deviation angle θ1. The control device 71 generates the path R by adding or subtracting the deviation θ2 of the approach angle detected in step S5 from the attitude.

[0071] Next, in step S13, the control device 71 makes an approach. Step S13 is the same process as in step S3. Next, in step S14, the control device 71 moves the forklift 10 forward. Step S14 is the same process as in step S4.

[0072] Next, in step S15, the control device 71 detects the angular displacement of the pallet P. Step S15 is the same process as in step S5. Next, in step S16, the control device 71 detects the edge of the loading platform. Step S16 is the same process as in step S5.

[0073] Next, in step S17, the fork 26 is stopped. Step S17 is the same process as in step S7. Next, in step S18, the control device 71 performs a rotation of the forklift 10 in place so that the deviation θ2 of the entry angle falls within the allowable range. Step S18 is the same process as step S8. In step S18, the forklift 10 rotates in place by the amount of the deviation θ2 of the entry angle detected in step S15.

[0074] Next, in step S19, the control device 71 performs a cargo handling operation. Step S19 is the same process as in step S9. If the displacement angle θ1 detected in step S15 is greater than the displacement angle θ1 detected in step S5, the control device 71 may cancel the correction of path R due to the displacement angle θ1 when generating path R in subsequent cycles. If the displacement angle θ1 detected in step S15 is greater than the displacement angle θ1 detected in step S5 multiple times in a row, the control device 71 may cancel the correction of path R due to the displacement angle θ1 when generating path R in subsequent cycles. If the correction of path R due to the displacement angle θ1 is canceled, the correction of path R does not need to be performed in the cycle in which the cancellation occurred. If the correction of path R is canceled, the control device may treat the pallet P to be placed next as the pallet P to be placed first.

[0075] [Operation of the First Embodiment] As shown in Figure 5, when the forklift 10 places multiple pallets P from the same direction, the displacement angle θ1 between the loading section 103 and each pallet P tends to be similar. For example, the displacement angle θ1 of each pallet P1 tends to be similar. The displacement angle θ1 of each pallet P2 tends to be similar.

[0076] The cause of the deviation angle θ1 could be, for example, individual differences in the forklift 10, the accuracy of sensors such as the external sensor 61 and camera 65, or a decrease in the accuracy of self-position estimation due to the surrounding environment of the truck 100. Furthermore, even if the path R itself is accurate, the deviation angle θ1 will increase if the forklift 10 cannot accurately follow the path R, or if the path R itself is not accurately generated.

[0077] The above-mentioned causes are not accidental but always present; therefore, when the forklift 10 places multiple pallets P from the same direction, the displacement angle θ1 between the loading section 103 and each pallet P tends to be similar. In other words, multiple pallets P tend to tilt in the same way. To put it another way, within the same cycle, the displacement angle θ1 can be considered identical.

[0078] [Effects of the First Embodiment] (1-1) The control device 71 corrects the path R based on the displacement angle θ1 calculated in the past within the same cycle. When the forklift 10 places multiple pallets P from the same direction, the displacement angle θ1 between the placement section 103 and each pallet P tends to be a similar angle. Therefore, by correcting the path R based on the displacement angle θ1 calculated in the past, the displacement angle θ1 can be reduced when placing pallets P from the second time onward.

[0079] (1-2) The control device 71 rotates the forklift 10 in place by the amount of the displacement angle θ1, and then places the pallet P. When placing the pallet P for the first time, the path R cannot be corrected, so rotating in place makes the displacement angle θ1 smaller.

[0080] When placing pallet P for the second time or later, although the path R is corrected, the deviation angle θ1 may exceed the acceptable range. Therefore, even for the second time and beyond, the deviation angle θ1 can be reduced by performing a rotation in place.

[0081] (1-3) When the control device 71 places a pallet P on the loading section 103 for the second time or later, it corrects the path R based on the displacement angle θ1 calculated when the pallet P was placed on the loading section 103 for the first time. When placing a pallet P for the second time or later, the forklift 10 travels along the corrected path R, so it is not possible to detect the displacement angle θ1 when the path R is not corrected. That is, the displacement angle θ1 may be smaller than when the path R is not corrected. By correcting the path R based on the displacement angle θ1 calculated when the pallet P was placed on the loading section 103 for the first time, the displacement angle θ1 when it is not corrected can be used. Therefore, the displacement angle θ1 can be appropriately reduced.

[0082] (1-4) The displacement angle θ1 can be calculated using distance meters 62 and 63 for detecting the edge of the loading platform. Since it is not necessary to use a dedicated sensor to calculate the displacement angle θ1, the increase in the number of parts can be suppressed.

[0083] (Second Embodiment) A second embodiment of the forklift will be described. The differences from the first embodiment will be explained.

[0084] As shown in Figure 11, the forklift 10 is equipped with a first hole detection sensor 81 and a second hole detection sensor 82. The hole detection sensors 81 and 82 are laser distance meters. The hole detection sensors 81 and 82 in this embodiment are one-dimensional distance meters capable of measuring distance in only one direction.

[0085] The hole detection sensors 81 and 82 are attached to the tip of the support portion 27. The hole detection sensors 81 and 82 may also be built into the support portion 27. The first hole detection sensor 81 and the second hole detection sensor 82 are spaced apart from each other in the left-right direction. The first hole detection sensor 81 is provided on the support portion 27 of the first fork 26L. The second hole detection sensor 82 is provided on the support portion 27 of the second fork 26R. The distance from the tip of the support portion 27 of the first fork 26L to the first hole detection sensor 81 is the same as the distance from the tip of the support portion 27 of the second fork 26R to the second hole detection sensor 82. That is, the first hole detection sensor 81 and the second hole detection sensor 82 are provided at the same position in the front-rear direction.

[0086] The two hole detection sensors 81 and 82 are arranged such that the laser emitted from the first hole detection sensor 81 and the laser emitted from the second hole detection sensor 82 are directed forward. The laser emitted from the first hole detection sensor 81 and the laser emitted from the second hole detection sensor 82 are parallel to each other.

[0087] The hole detection sensors 81 and 82 are used to detect holes H in the pallet P. When the lasers emitted from the hole detection sensors 81 and 82 are directed towards the holes H, the detected value is larger than when the lasers are hitting the front surface of the pallet P. When the support portion 27 is facing the hole H, the laser passes through the hole H. Therefore, the control device 71 can determine from the detected values ​​of the hole detection sensors 81 and 82 whether or not the support portion 27 is facing the hole H.

[0088] The forklift 10 includes a first load-gathering sensor 83 and a second load-gathering sensor 84. The load-gathering sensors 83 and 84 are laser distance meters. The hole detection sensors 81 and 82 in this embodiment are one-dimensional distance meters capable of measuring distance in only one direction. The first load-gathering sensor 83 and the second load-gathering sensor 84 are spaced apart from each other in the left-right direction. The first load-gathering sensor 83 is provided on the support portion 27 of the first fork 26L. The first load-gathering sensor 83 is provided such that the laser strikes the front of the pallet P when the left side surface of the first fork 26L is in contact with the inner surface of the hole H, and the laser passes through the hole H when the left side surface of the first fork 26L is not in contact with the inner surface of the hole H. The second load-gathering sensor 84 is provided on the support portion 27 of the second fork 26R. The second load-shifting sensor 84 is positioned such that the laser strikes the front of the pallet P when the right side of the second fork 26R is in contact with the inner surface of the hole H, and the laser passes through the hole H when the right side of the second fork 26R is not in contact with the inner surface of the hole H. The distance from the tip of the support portion 27 of the first fork 26L to the first load-shifting sensor 83 is the same as the distance from the tip of the support portion 27 of the second fork 26R to the second load-shifting sensor 84. In other words, the first load-shifting sensor 83 and the second load-shifting sensor 84 are located at the same position in the front-rear direction.

[0089] The two load-gathering sensors 83 and 84 are arranged such that the laser emitted from the first load-gathering sensor 83 and the laser emitted from the second load-gathering sensor 84 are directed forward. The laser emitted from the first load-gathering sensor 83 and the laser emitted from the second load-gathering sensor 84 are parallel to each other.

[0090] The load shifting sensors 83 and 84 are used to determine whether load shifting has been performed. Load shifting means bringing the pallets P into contact with each other. If there is a gap between the pallets P placed on the loading section 103, there is a risk of the load colliding with each other while the truck 100 is in motion, causing the load to collapse. Therefore, the control device 71 performs load shifting to bring the pallets P into contact with each other and fill the gap between them. Load shifting is performed by moving the forks 26 left and right using the side shift device 41.

[0091] When placing a pallet P on the loading section 103, the control device 71 moves the forks 26 left or right using the side shift device 41. The control device 71 moves the forks 26 in the direction that the pallet P loaded on the forks 26 is moving toward the pallet P placed on the loading section 103. When placing pallets P from the front to the back of the truck 100, when placing a pallet P from the right side of the truck 100, the forks 26 should be moved to the right using the side shift device 41. When placing a pallet P from the left side of the truck 100, the forks 26 should be moved to the left using the side shift device 41.

[0092] The control device 71 may determine that loading is complete when the detection value of the first loading sensor 83 decreases when the fork 26 is moved to the left. When the fork 26 is moved to the left and the pallets P come into contact with each other, the movement of the pallets P loaded on the fork 26 is restricted, causing the left side of the first fork 26L to come into contact with the inner surface of the hole H. As a result, the laser of the first loading sensor 83 hits the front of the pallets P, causing the detection value to decrease.

[0093] The control device 71 may determine that loading is complete when the detection value of the second loading sensor 84 decreases when the fork 26 is moved to the right. When the fork 26 is moved to the right and the pallets P come into contact with each other, the movement of the pallets P loaded on the fork 26 is restricted, causing the right side of the second fork 26R to come into contact with the inner surface of the hole H. As a result, the laser of the second loading sensor 84 hits the front of the pallet P, causing the detection value to decrease. In this way, the loading sensors 83 and 84 are used to determine whether loading has been performed or not.

[0094] The cargo handling control performed by the control device 71 when the forklift 10 is loading cargo will be described. In the cargo handling control of the second embodiment, the method for detecting angular deviation differs from that of the first embodiment. The control other than angular deviation detection is the same as in the first embodiment.

[0095] As shown in Figure 11, when the forklift 10 is facing the side panels 105 and 106, the distance to the side panels 105 and 106 is detected by the first load-shifting sensor 83 and the second load-shifting sensor 84. The deviation θ3 of the entry angle of the forks 26 relative to the mounting section 103 is expressed by the following equation (2).

[0096] The deviation in the entry angle θ3 = tan -1 (distance difference X2 / separation distance Z)…(2) The distance difference X2 is the difference between the value detected by the first load-gathering sensor 83 and the value detected by the second load-gathering sensor 84. For example, the distance difference X2 is the value obtained by subtracting the value detected by the second load-gathering sensor 84 from the value detected by the first load-gathering sensor 83. The deviation θ3 of the entry angle can be considered as the deviation angle θ1.

[0097] The deviation θ3 of the entry angle can also be calculated by using the detected values ​​of the first hole detection sensor 81 and the second hole detection sensor 82 instead of the detected values ​​of the first load-gathering sensor 83 and the second load-gathering sensor 84. When calculating the deviation θ3 of the entry angle from the detected values ​​of the first hole detection sensor 81 and the second hole detection sensor 82, the first hole detection sensor 81 is the first distance meter and the second hole detection sensor 82 is the second distance meter. When calculating the deviation θ3 of the entry angle from the detected values ​​of the first load-gathering sensor 83 and the second load-gathering sensor 84, the first load-gathering sensor 83 is the first distance meter and the second load-gathering sensor 84 is the second distance meter.

[0098] [Effects of the second embodiment] According to the second embodiment, in addition to the effects of the first embodiment, the following effects can be obtained. (2-1) The deviation θ3 of the entry angle can be calculated using the hole detection sensors 81, 82 or the load adjustment sensors 83, 84. Since it is not necessary to use a dedicated sensor to calculate the deviation θ3 of the entry angle, the increase in the number of parts can be suppressed.

[0099] [Example of changes] Each embodiment can be implemented with the following modifications. Each embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0100] ○In each embodiment, when the control device 71 places the pallet P for the third time or later, it may correct the path R based on the displacement angle θ1 calculated when the pallet P is placed on the mounting section 103 for the second time or later within the same cycle.

[0101] ○In each embodiment, feature point detection may be performed using the difference in the moving average of the detected values ​​of the distance meters 62 and 63. The control device 71 may perform feature point detection using the detected value of the first distance meter 62, or it may perform feature point detection using the detected value of the second distance meter 63.

[0102] As shown in Figure 12, when calculating the difference in the moving average of the detected values ​​from distance meters 62 and 63, the difference in the moving average is 0 up to the first time step t1. The number of detected points used when calculating the moving average is arbitrary. The difference value is the difference between the previous value of the moving average and the current value of the moving average. For example, the difference value is the current value of the moving average minus the previous value of the moving average. When distance meters 62 and 63 are detecting the distance to the ground, the change in distance is small, so the difference in the moving average will be 0 or close to 0.

[0103] At the first time point t1, when distance meters 62 and 63 begin to detect the distance to tilt points 105 and 106, the distance detected by distance meters 62 and 63 changes, causing the difference in the moving average to become less than 0. As long as the moving average includes the distance to the ground, the difference in the moving average fluctuates significantly due to the difference between the distance to the ground and the distance to tilt points 105 and 106. Once the moving average no longer includes the distance to the ground, the change in the difference in the moving average becomes more gradual.

[0104] At the second time point t2, when the distance to the ground is detected, the distance detected by distance meters 62 and 63 increases. As a result, the distance to the ground is included in the moving average, and the difference value of the moving average becomes greater than 0.

[0105] When the third time point t3 arrives and the distance to the stepped section 104 is detected, the distance detected by distance meters 62 and 63 becomes shorter. As a result, the distance to the stepped section 104 is included in the moving average, and the difference value of the moving average becomes less than 0.

[0106] Thus, even when using the difference value of the moving average, the difference value fluctuates significantly at the feature points. For this reason, it may be possible to set a threshold for the difference value or otherwise enable the detection of feature points from changes in the difference value. The control device 71 may then use the difference value of the moving average to detect feature points and use these feature points to perform angular displacement detection or detection of the edge of the loading platform.

[0107] ○In each embodiment, the external sensor 61 may also be used as the pallet detection sensor 66. ○In each embodiment, detection of the edge of the loading platform may be performed using point cloud data acquired from the external sensor 61 or the pallet detection sensor 66. In this case, the forklift 10 of the second embodiment does not need to be equipped with distance meters 62 and 63.

[0108] ○In each embodiment, the detection of the pallet P may be performed using the external sensor 61. For example, the control device 71 extracts point cloud data corresponding to the pallet P from the point cloud data acquired from the external sensor 61. The point cloud data corresponding to the pallet P is obtained, for example, by matching the shape of the pallet P with the point cloud data acquired from the external sensor 61.

[0109] ○In each embodiment, the control device 71 may perform a turn while driving to cancel out the displacement angle θ1, instead of turning in place. In this case, if the distance between the forklift 10 and the truck 100 is short and the necessary amount of travel distance for turning cannot be secured, the control device 71 may secure the necessary travel distance by having the forklift 10 move in reverse.

[0110] ○In the first embodiment, the distance meters 62 and 63 may be two-dimensional distance meters 62 and 63 that detect distances in two directions. For example, the distance meters 62 and 63 may detect distances in two directions by irradiating a laser in a fan shape. In the second embodiment, at least one of the hole detection sensors 81 and 82 and the load-gathering sensors 83 and 84 may be a two-dimensional distance meter.

[0111] ○In each embodiment, the forklift 10 may be a counterbalanced forklift. ○In each embodiment, the control of self-position estimation, driving motion, and cargo handling motion may be performed by different control devices, respectively.

[0112] ○In each embodiment, the object to be loaded may be different from the truck 100. For example, the object to be loaded may be a pallet conveyor. The pallet conveyor includes a loading section. The loading section includes, for example, rollers that transport pallets P by rotating. The loading section is located above the road surface on which the forklift 10 travels. When the loading section is located above the road surface, a difference in height between the loading section and the road surface will cause a difference in the detected values ​​of the distance meters 62 and 63 when the distance meters 62 and 63 reach above the edge of the loading section. As in the first embodiment, when the distance meters 62 and 63 are arranged to measure the distance to an object below, the edge of the loading section can be detected as a feature point. The control device 71 can calculate the deviation θ2 of the entry angle using the feature point. In the case where the distance meter is positioned to measure the distance to the object in front, as in the hole detection sensors 81, 82 and load-gathering sensors 83, 84 of the second embodiment, the control device 71 can calculate the deviation θ3 of the entry angle from the distance to the side of the mounting section.

[0113] The object to be placed on is a shelf. In this case, the top surface of the shelf is the placement surface. Even when the top surface of the shelf is the placement surface, the displacement angle θ1 can be calculated using the same method. ○In the first embodiment, the forklift 10 does not need to be equipped with a side shift device 41. In the second embodiment, when the displacement angle θ3 is calculated using hole detection sensors 81 and 82, the forklift 10 does not need to be equipped with a side shift device 41. [Explanation of Symbols]

[0114] P...pallet, R...route, 10...forklift, 26...fork, 62...first distance meter, 63...second distance meter, 71...control device, 103...mounting unit.

Claims

1. Two forks on which pallets are loaded, First rangefinder and, The first rangefinder and the second rangefinder, which are positioned separately in the left-right direction, A forklift equipped with a control device, The control device is A path is generated to the loading position set on the loading section located above the road surface on which the forklift travels. Move the forklift along the aforementioned route and place the pallet in the aforementioned location. If we consider the process of placing multiple pallets on the aforementioned placement area from the same direction as one cycle, The control device is When placing the pallet on the aforementioned placement unit for the first time in the aforementioned cycle, the displacement angle between the aforementioned placement unit and the pallet is calculated based on the detected values ​​of the first distance meter and the second distance meter. A forklift that, when placing the pallet in the aforementioned storage area for the second time or later in the aforementioned cycle, corrects the path based on the displacement angle previously calculated within the same cycle.

2. The control device is When placing the pallet on the mounting section, the offset angle between the mounting section and the pallet is calculated based on the detected values ​​of the first distance meter and the second distance meter. The forklift according to claim 1, wherein the forklift is rotated in place by the amount of the aforementioned displacement angle, and then the pallet is placed on it.

3. The forklift according to claim 1, wherein the control device corrects the path when placing the pallet in the aforementioned placement area for the second time or later in the cycle, based on the displacement angle calculated when placing the pallet in the aforementioned placement area for the first time within the same cycle.

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