FORKLIFT DEVICE, FORKLIFT CONTROL METHOD AND PROGRAM

Abstract

A forklift device comprising: an error prediction unit (1003) configured to predict, after a pallet (20) is loaded, a first position error, which is a position error between a standard position of a fork (11) and a center position of the pallet (20) on the fork (11) after loading, and a first angle error, which is an angle error of the pallet (20) with respect to the fork (11) after loading; a travel path correction unit (1005) configured to correct a travel path previously set from a loading position of the pallet (20) to a stacking position of the pallet (20) to compensate for the first position error and the first angle error when the pallet (20) is stacked; and a conveying travel control unit (1006) configured to perform travel control so that the pallet (20) is conveyed along the corrected travel path.

Description

[0001] The present disclosure relates to a forklift device, a forklift control method, and a program. Priority is claimed to Japanese Patent Application No. 2018-124449, filed on June 29, 2018, the contents of which are incorporated herein by reference.

[0002] When forklift devices load pallets with loads placed on them, convey the pallets to stacking positions, and stack the pallets, errors occur in which, in some cases, the positions of the stacked pallets deviate from the intended stacking positions. Therefore, for example, when unmanned forklift devices are automatically driven, the loading and stacking of pallets is repeated, and errors are accumulated that exceed the tolerated errors. Therefore, there is a possibility that pallets cannot be loaded and cannot be finally stacked by the forklift devices, or there is a possibility that loads fall over. Patent Literature 1 discloses a technology for aligning fork center lines with pallet center lines at the time of pallet loading without accumulating errors.Patent Literature 2 discloses a technology for correcting an error by laterally shifting forks by an error when stacking pallets. [Patent Literature 1] Japanese unexamined patent application, first publication number JP H03- 211 199 A [Patent Literature 2] Japanese unexamined patent application, first publication number JP H02- 163 298 A

[0003] US 7,757,946 B2 discloses a system and method for sizing products on or in forklifts, pallets, or pallet trucks. A tunnel or other defined space allows the passage of a material handling vehicle. The tunnel is equipped with one or more dimension-sensing devices to detect the overall dimensions of the vehicle and the products on it. A computer system communicates with the tunnel to determine the dimensions of the product alone by subtracting the known dimensions of the vehicle from the overall dimensions.

[0004] DE 42 34 174 C2 relates to a method for load pickup and delivery by forklift trucks that have at least one movable fork tine that picks up a load and ultrasonic sensors. These sensors are designed for distance measurements and allow for the detection and compensation of lateral offsets or inclinations of the load to prevent misalignment during transport.

[0005] US 2018 / 0 105 406 A1 describes a forklift equipped with a two-dimensional distance sensor. This distance sensor emits a measurement signal in a downward direction to measure the distance to a measuring point on the surface of a load. The forklift can determine whether there is a height difference on the surface of the load and whether the front part is higher than the rear part, thus ensuring the stability of stacked loads.

[0006] JP H03-211 199 A concerns a load-handling control system for driverless industrial vehicles. It describes a device that automatically adjusts the position of a forklift's forks to ensure that the load is picked up correctly, even if the load is not correctly positioned on the pallet. This helps ensure stability during transport and prevents damage to the load or the surrounding area.

[0007] In recent years, with the increase in shipping volume or the acceleration of shipping, it has become necessary to shorten the cycle time of an unmanned forklift. However, in unmanned forklifts with this technology, this requires time due to operations such as operating the forks in the lateral direction (sideways shifting) before loading pallets, adjusting the fork spacing to detect pallet positions, and many other sensing operations required to convey loads.

[0008] An object of the present disclosure is to provide a forklift device, a forklift control method, and a program capable of quickly conveying a load of a forklift device to shorten a cycle time of work of an unmanned forklift device.

[0009] According to one aspect of the present disclosure, the object is achieved by a forklift device according to claim 1 or 7, or a program according to claim 8. The dependent claims relate to further advantageous embodiments of the invention.

[0010] According to at least one of the preceding aspects, it is possible to quickly transport a load of a forklift device. Fig. 1 is an explanatory diagram showing an overview of a forklift apparatus according to a first embodiment. Fig. 2 is a side view illustrating the forklift device according to the first embodiment. Fig. 3 is an explanatory diagram showing a functional structure of the forklift device according to the first embodiment. Fig. 4 is an explanatory diagram showing a post-loading position error and a post-loading angle error that occur after a pallet is loaded for unloading by the forklift device. Fig. 5 is an explanatory diagram showing a center of gravity position after the pallet is loaded for unloading by the forklift device. Fig. 6 is an explanatory diagram showing the ease of rotation of the pallet due to a deviation of the center of gravity position of the load. Fig. 7 is a first explanatory diagram showing a data structure of error information stored in a database in a storage unit according to a first embodiment. Fig. 8 is a second explanatory diagram showing a data structure of travel path information according to the first embodiment, which is stored in a database in a storage unit. Fig. 9 is an explanatory diagram showing a process flow of the forklift device according to the first embodiment. Fig. 10 is a first explanatory diagram showing a travel path correction by a travel path correction unit according to the first embodiment. Fig. 11 is a second explanatory diagram showing a travel path correction by the travel path correction unit according to the first embodiment. Fig. 12 is a third explanatory diagram showing a travel path correction by the travel path correction unit according to the first embodiment. Fig. 13 is an explanatory diagram showing a functional structure of the forklift device according to the second embodiment. Fig. 14 is an explanatory diagram showing a process flow of the forklift device according to the second embodiment. Fig. 15 is an explanatory diagram showing a process flow of the forklift device according to a third embodiment.

[0011] Hereinafter, a forklift device 10 according to a first embodiment will be described with reference to Fig. 1 to 12 are described.

[0012] Fig. 1 is an explanatory view of an overview of the forklift device 10 according to the first embodiment. Fig. 2 is a side view showing a forklift device 10 according to the first embodiment. The forklift device 10 includes a fork 11 and a camera 103. The forklift device 10 can insert the fork 11 into holes 21 of the pallet 20 and load a pallet 20 on which cargo 22 is stacked. The pallet 20 is a loading platform used for orderly shipment of a cargo 22 to be placed thereon. The pallet 20 is, for example, a wooden pallet, a plastic pallet, a metal pallet, or a paper pallet. The holes 21 are two holes formed on side surfaces of the pallet 20. Here, the number of holes 21 is not limited to two.

[0013] In the following description, an extending direction of the fork 11 provided in the forklift device 10 is assumed to be a ±Y direction (an end side of the fork 11 is assumed to be the +Y side), and a direction perpendicular to the extending direction of the forks on a loading surface of the fork 11 is assumed to be a ±X direction (the right side viewed from the base side of the fork 11 is assumed to be the +X side). A direction perpendicular to the loading surface of the fork 11 is assumed to be the ±Z direction (the upper side of the loading surface is assumed to be the +Z side). In the embodiment, a case where the loading surface of the fork 11 is parallel to the horizontal direction will be described. However, the loading surface of the fork 11 may not be parallel to the horizontal direction.

[0014] Fig. 3 is an explanatory diagram showing a functional structure of the forklift device 10 according to the first embodiment.

[0015] As it is in Fig. 3, the forklift device 10 includes a central processing unit (CPU) 100, a fork motor 101, a traction motor 102, a camera 103, and a storage unit 104.

[0016] The central processing unit (CPU) 100 is a processor that operates according to a program prepared in advance to perform a variety of functions and is responsible for an overall operation of the forklift device 10.

[0017] The central processing unit (CPU) 100 functions as a relative position angle detection unit 1001, a center of gravity position detection unit 1002, an error prediction unit 1003, a travel path setting unit 1004, a travel path correction unit 1005, and a conveyance control unit 1006.

[0018] The relative position angle detection unit 1001 detects a relative position δ p before loading and a relative angle θ before loading between a center position O of the pallet 20 and a standard position M of the fork 11 before the forklift device 10 loads the pallet 20. The relative position δ p before charging and the relative angle θ before charging will be discussed later with reference to Fig. 4(a). Specifically, the relative position angle detection unit 1001 first receives image information of the holes 21 and image information of the load 22, which are captured by the camera 103 before the pallet 20 is loaded. Then, the relative position angle detection unit 1001 detects the relative position δ pbefore loading and the relative angle θ before loading between the center position O of the pallet 20 and the standard position M of the fork 11 based on the obtained image information of the holes 21.

[0019] Here the relative position +δ p before charging and the relative angle θ before charging are detected based on the detected image information of the holes 21, but can be detected based on the image information of the pallet 20.

[0020] The center of gravity position detecting unit 1002 detects a center of gravity position (a position of a center of gravity) δ before charging. g in the load 22 on the pallet 20 based on the image information of the load 22, which is imaged by the camera 103. The center of gravity position δ gbefore charging may be a center of gravity position of the load 22 calculated from a width, a depth, and a height of the load 22 obtained from the image information of the load 22 imaged by the camera 103.

[0021] When predicting a first position error δ p ', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 is loaded, and a first angle error θ', which is an angle error after loading with respect to the fork 11 of the pallet 20, the central processing unit (CPU) 100 may not have the center of gravity position detection unit 1002, if the center of gravity position δ g before loading the load 22 before the pallet 20 is loaded is not necessary.

[0022] The error prediction unit 1003 predicts the first position error δ p ' after loading, which is a position error between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 is loaded, predicts the first angular error θ', which is an angular error after loading with respect to the fork 11 of the pallet 20, and predicts the center of gravity position δ g ' after charging. The first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after charging will be discussed later with reference to Fig. 4(b).

[0023] In particular, based on the detected relative position δ p before charging, the recorded relative angle θ before charging, the recorded center of gravity position δ gbefore charging and preset error information 1041, the error prediction unit 1003 predicts the first position error δ p ', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 is loaded, for unloading, predicts the first angular error θ', which is an angular error after loading with respect to the fork 11 of the pallet 20, and predicts the center of gravity position δ g ' after charging. Here, the error information is 1041 information, in which the relative position δ p before charging, the relative angle θ before charging and the center of gravity position δ g before loading for unloading are related to the first position error δ p ', the first angular error θ' and the center of gravity position δ g' after loading, after the pallet 20 is loaded. Accordingly, based on the detected relative position δ p before charging, the recorded relative angle θ before charging and the recorded center of gravity position δ g before charging, the error prediction unit 1003 calculates the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after charging without physical analysis in real time.

[0024] Therefore, it is possible to reduce the time required for real-time physical analysis of the first position error, the first angle error, and the center of gravity position after charging.

[0025] The first position error δ p ', the first angular error θ' and the center of gravity position δ g' after loading may be acquired with image information imaged by the camera 103 or the like after the forklift device 10 has loaded the pallet 20, instead of predicting it before the pallet 20 has been loaded.

[0026] The travel path setting unit 1004 sets a travel path R from the loading position of the pallet 20 to the stacking position of the pallet 20. Specifically, the travel path setting unit 1004 sets the travel path R based on the loading position of the pallet 20 and the stacking position of the pallet 20, taking into account travel path information 1042 of the storage unit 104.

[0027] The travel path correction unit 1005 pre-corrects the travel path R from the loading position of the pallet 20 to the stacking position of the pallet 20 in order to compensate for a stacking error caused by the first position error δ p' and the first angular error θ' that occurs when the pallet 20 is stacked. Compensation of the stacking error will be described later.

[0028] The conveyance travel control unit 1006 performs travel control such that the pallet 20 is conveyed along the corrected travel path R'. Specifically, the conveyance travel control unit 1006 performs travel control such that the pallet 20 is conveyed such that the forklift device 10 that loads the pallet 20 is caused to travel from the loading position of the pallet 20 to the stacking position along the corrected travel path R'.

[0029] The fork motor 101 operates to drive the fork 11 upward or downward to load or stack the pallet 20. In the embodiment, the case where the conveyance control unit 1006 controls the operation of the fork motor 101 will be described. However, in other embodiments, the operation of the fork motor 101 may be controlled by another control unit.

[0030] The drive motor 102 operates in such a way that the forklift 10 is caused to travel along the corrected travel path R'.

[0031] The camera 103 images the holes 21 of the pallet 20 and the load 22 on the pallet 20 to obtain image information of the holes 21 of the pallet 20 and image information of the load 22 on the pallet 20 before the pallet 20 is loaded. As shown in Fig. 2, the camera 103 is mounted on the front surface of the forklift device 10 and obtains image information of an image area / field of view S. However, a position at which the camera 103 is mounted on the forklift device 10 may be a position at which images of the holes 21 and the load 22 can be obtained and is not limited to the position shown in Fig. 2 limited.

[0032] The camera 103 may be a device capable of imaging the pallet 20 and the load 22 to obtain image information thereof, or may be a LiDAR camera, a laser radar, or the like.

[0033] The storage unit 104 stores the error information 1041 and the travel path information 1042. The error information 1041 of the storage unit 104 is referred to by the error prediction unit 1003 when the error prediction unit 1003 detects the first position error δ p' for unloading, which is a position error after the pallet 20 is loaded, the first angular error θ', which is an angular error after loading, and the center of gravity position δ g ' after loading. The travel path information 1042 of the storage unit 104 is information in which the loading position (starting location) of the pallet 20, the stacking position (a destination) of the pallet 20, and the travel path R are related to each other. The travel path setting unit 1004 refers to the travel path information 1042 when the travel path setting unit 1004 sets the travel path R.

[0034] The storage unit 104 is a large-capacity storage device (a non-volatile memory) included in the forklift device 10 and is, for example, a hard disk drive (HDD), a solid-state drive (SSD), or the like. The storage unit 104 is referred to as an auxiliary storage device and records acquired information. In the first embodiment, the first position error, which is a position error after loading the pallet 20, and the first angle error, which is an angle error after loading, which occur after the forklift device 10 loads the pallet 20 to receive a load, are corrected. Next, a first position error, which is a position error after loading, and a first angle error, which is an angle error after loading the pallet 20, which are correction targets, will be described with reference to Fig. 4 and Fig. 5 are described.

[0035] Fig. 4 is an explanatory diagram showing a post-loading position error and a post-loading angle error that occur after a pallet 20 is loaded for unloading by the forklift device 10.

[0036] Fig. 4(a) shows a situation before the forklift device 10 loads the pallet 20. As shown in Fig. 4(a), a deviation occurs (the relative position δ pbefore loading and the relative angle θ before loading) between the center position O of the pallet 20 and the standard position M of the fork 11. The center position O is a center position of the pallet 20 and, in particular, is a position indicating an intersection point between the center lines P1 and P2 of the pallet 20. The standard position M is a position regulated as a standard with respect to the fork 11 and, in particular, is a position indicating an intersection point between the center lines F1 and F2 of the fork 11.

[0037] The relative position δ p before charging includes both an error δ x in the ± X direction and an error δ y in the ± Y direction between the standard position M and the center position O. Here the relative position δ p before charging by (δ x , δ y). The relative angle θ before loading is an angular deviation of the center line P1 of the pallet 20 with respect to the center line F1 of the fork 11.

[0038] In the situation presented in Fig. 4(a), the forklift device 10 detects a position of the pallet 20 before loading the pallet 20, and the forklift device 10 moves directly to the pallet to pick up the pallet 20 to receive a load. At this time, as shown in Fig. 4(b), a deviation occurs (the first position error δ p ', which is a position error after loading and the first angular error θ', which is an angular error after loading) between the center position O of the pallet 20 and the standard position M of the fork 11.

[0039] Here, for the standard position M, it is assumed that the center position O is aligned with the standard position M when the pallet 20 is stacked, so that the pallet 20 is aligned with a center line F1 of the fork 11 and a side surface P3 of the holes 21 of the pallet 20 is aligned with a base surface F3 of the fork 11. The first position error, which is a position error after loading, has both an error δ x ' in the ± X direction and an error δ y ' in the ± Y direction between the standard position M and the center position O when the pallet 20 is loaded by the fork 11. Here, the first position error δ p ' by (δ x ', δ y '). The first angular error θ' is an angular deviation of the center line F1 of the fork 11 with respect to the center line P1 of the pallet 20.

[0040] When the pallets are loaded and stacked a multitude of times without the first position error δ p ' and the first angular error θ', the first position error δ accumulates p ' and the first angular error θ' and therefore there is a possibility that the accumulated error exceeds a tolerated error within which the pallets can be stacked at the pallet stacking position.

[0041] The first position error δ p ', which is a position error after loading, and the first angular error θ', which is an angular error after loading in the pallet 20, depend on a center of gravity position of the load 22 on the pallet 20. The following is a relationship between the center of gravity position of the load 22 and the first position error δ p ' and the first angular error θ'. Fig. 5 is an explanatory diagram showing a center of gravity position after the pallet 20 is loaded for unloading by the forklift device 10.

[0042] In Fig. 5, the load 22 on the pallet 20 is not placed at the center position O of the pallet 20, but is offset in the + X direction. At this time, the center of gravity position δ g ' of charge 22 by +δ gx ' from the center position O of the pallet 20 in the X direction. Therefore, when the forklift device 10 moves the pallet 20 without correction, the pallet 20 deviates or rotates with respect to the fork 11, and therefore there is a possibility of further position error and angle error occurring.

[0043] That is, if the pallets are loaded and stacked a plurality of times without considering the center of gravity positions after the pallets 20 are loaded for unloading, the position errors and the angle errors accumulate, and therefore, there is a possibility that the accumulated error exceeds a tolerated error at which the pallets can be stacked at the stacking position of the pallets.

[0044] Fig. Fig. 6 is an explanatory diagram showing the ease of rotation of the pallet 20 due to a deviation of the center of gravity position δ g the charge 22 shows.

[0045] In Fig. 6, the load 22 on the pallet 20 is not placed in the center position O of the pallet 20 and is offset by +δ gx ' in the + X direction and by -δ gy' in the Y direction. At this time, it is easy for the pallet 20 on the fork 11 to rotate clockwise (W1) relative to the fork 11, and it is difficult for the pallet 20 to rotate counterclockwise (W2).

[0046] Next, the error information 1041 stored in the storage unit 104 will be described.

[0047] Fig. 7 is a first explanatory diagram showing a data structure of the error information 1041 according to the first embodiment, which is stored as a database in the storage unit 104.

[0048] As shown in Fig. 7, a first column shows the relative position δ p before charging, the relative position θ before charging and the center of gravity position δ g before loading into the pallet 20 with respect to the fork 11 before the pallet 20 is loaded for unloading. A second column shows the first position error δ p', which is a position error after loading, after the pallet 20 is loaded for unloading, the first angular error θ', which is an angular error after loading and the center of gravity position δ g ' after loading. When a relative position before loading, a relative angle before loading and a center of gravity position before loading, which are detected by the relative position angle detection unit 1001 before loading the pallet 20, δ 1p , θ1, δ 1g correspond, a first position error, which is a position error after loading the pallet 20, a first angle error, which is an angle error after loading, and the center of gravity position after loading are predicted as δ 1p ', θ1', δ 1g'. When a relative position before loading, a relative angle before loading and a center of gravity position before loading, which are detected by the relative position angle detection unit 1001 before loading the pallet 20, δ 2p θ 2, δ 2g correspond, a first position error, which is a position error after loading the pallet 20, a first angle error, which is an angle error after loading, and a center of gravity position after loading are predicted as δ 2p ', θ2', δ 2g '. When a relative position before loading, a relative angle before loading and a center of gravity position before loading, which are detected by the relative position angle detection unit 1001 before loading the pallet 20, δ 3p , θ 3, δ 3gare, a first position error, which is a position error after loading the pallet 20, a first angle error, which is an angle error after loading, and a center of gravity position after loading are predicted as δ 3p ', θ3', δ 3g '.

[0049] A correlation of the relative position before loading of the pallet 20, the relative angle before loading and the center of gravity position before loading with the first position error, which is a position error after loading of the pallet 20, the first angle error, which is an angle error after loading and the center of gravity position after loading can be carried out in advance using a coarse-scale analysis taking into account friction between at least two of the fork 11, the pallet 20 and the load 22 and an influence of the center of gravity position of the load 22 shown in Fig. 6, and the associated information can be stored in the error information 1041. Therefore, even if there is a variation in the state of the load 22, countermeasures can be taken. A value of friction between at least two of the fork 11, the pallet 20, and the load 22 can be known.

[0050] Instead of the embodiment in which the error information 1041 is used, a relative position of the pallet 20 with respect to the fork 11 before loading the pallet 20, a relative angle before loading, and a center of gravity position before loading may be physically analyzed in real time, and the first position error, which is a position error after loading the pallet 20, a first angle error, which is an angle error after loading, and the center of gravity position after loading may be calculated. Next, the travel path information 1042 stored in the storage unit 104 will be described.

[0051] Fig. 8 is a second explanatory diagram illustrating a data structure of the travel path information 1042 according to the first embodiment, which is stored as a database in the storage unit 104.

[0052] As shown in Fig. 8, a first column shows positions of loading positions (starting locations). A second column shows the positions of stacking positions (destinations). A third column shows paths from the loading positions to the stacking positions. If the loading position is A and the stacking position is B, the path is set to a first route in the first row. If the loading position is A and the stacking position is C, the path is set to a second path in the second row. If the loading position is D and the stacking position is E, the path is set to a third path in the third row. If the loading position is D and the stacking position is F, the path is set to a fourth path in the fourth row. In this way, the path is set with the loading position and the stacking position. In the following description, a loading position is assumed as A, a stacking position is assumed as B, and the travel path is assumed as R1.

[0053] A method for setting a path is not limited to the method described above as long as the path from the loading position to the stacking position is uniquely set.

[0054] Fig. 9 is an explanatory diagram showing a process flow of the forklift device 10 according to the first embodiment.

[0055] The process flow shown in Fig. 9 is performed repeatedly during operation of the forklift device 10.

[0056] First, the camera 103 receives image information of the holes 21 of the pallet 20 and image information of the load 22. The relative position angle detection unit 1001 detects the pallet 20 based on image information of the holes 21 of the pallet 20 (step S101). The relative position angle detection unit 1001 then detects the relative position δ pbefore loading and the relative angle θ before loading between the center position O of the pallet 20 and the standard position M of the fork 11 based on the image information of the detected holes 21 (step S102).

[0057] The center of gravity position detection unit 1002 then detects the center of gravity position δ g before loading the load 22 onto the pallet 20 based on the image information of the load 22 captured by the camera 103 (step S103).

[0058] The error prediction unit 1003 predicts a first position error δ p ', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after loading the pallet 20, predicts the first angular error θ', which is an angular error after loading the pallet 20 with respect to the fork 11, and predicts the center of gravity position δ g' after charging (step S104). In particular, based on the detected relative position δ p before charging, the recorded relative angle θ before charging, the recorded center of gravity position δ g before charging and the error information 1041 defined in advance, the error prediction unit 1003 predicts the first position error δ p ', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 is loaded, for unloading ahead, the first angular error θ', which is an angular error after loading the pallet 20 with respect to the fork 11 and the center of gravity position δ g ' after loading the pallet 20 with respect to the fork 11. Here is the error information 1041 information in which the relative position δ p before charging, the relative angle θ before charging and the center of gravity position δg before charging in relation to the first position error δ p ' are set, the first angular error θ' and the center of gravity position δ g ' after loading, after the pallet 20 is loaded for unloading. Accordingly, based on the detected relative position δ p before charging, the recorded relative angle θ before charging and the recorded center of gravity position δ g before charging, the error prediction unit 1003 calculates the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after charging in real time without physical analysis.

[0059] Therefore, it is possible to reduce the time required to perform physical analysis of the first position error, the first angle error and the center of gravity position after charging in real time.

[0060] The forklift device 10 then loads the pallet 20 for unloading (step S105).

[0061] The travel path setting unit 1004 sets the travel path R1 from the loading position A of the pallet 20 to the stacking position B of the pallet 20 (step S106). For example, in the case of the loading position A and the stacking position B, the travel path setting unit 1004 sets the travel path R1 with reference to the travel path information 1042 of the storage unit 104, as shown in Fig. 8, the route R1.

[0062] The travel path correction unit 1005 corrects the travel path R1, which has been set in advance from the loading position A of the pallet 20 to the stacking position B of the pallet 20, by a stacking error caused by the first position error δ p' and the first angular error θ' that occurs when the pallet 20 is stacked (step S107). A process in which the travel path correction unit 1005 corrects the travel path R1 to the travel path R1' will be described below.

[0063] A procedure in which the error occurring when loading the pallet 20 at the stacking position B is compensated by correcting the travel path R1 will be described with reference to the Fig. 10 to 12.

[0064] Fig. 10 to 12 are first to third explanatory diagrams illustrating travel path correction by the travel path correction unit 1005 according to the first embodiment.

[0065] Fig. 10 illustrates a positional relationship between the standard position M of the fork 11 and the current center position O of the pallet 20 when the forklift device 10 travels along the predetermined travel path R1 and stacks the pallet 20 by aligning the standard position M of the fork 11 to the stacking position B.

[0066] As shown in Fig. 10, when the forklift device 10 travels along the specified travel path R1 and stacks the pallet 20 at the stacking position B, the first position error δ p ' (δ x ', δ y ') and the first angular error θ'. Accordingly, the stacking position can be adjusted to the stacking position B, for which the center position O of the pallet 20 is a target, by shifting the standard position M of the fork 11 from the stacking position B to the stacking position B', as shown in Fig. 11, so that the first position error δ p ' (δ x ', δ y') and the first angular error θ' are compensated when the pallet 20 is stacked. In particular, the travel path R1 for stacking is corrected so that the standard position M of the fork 11 is shifted by -δ p ' (-a, -b) on the XY plane and the pallet 20 is rotated by -θ' on the XY plane with respect to the fork 11 at the stacking position B'. Here -a = -δ x 'cosθ-δ y 'sinθ and -b = δ x 'sinθ-δ y 'cosθ is fulfilled.

[0067] For example, the travel path correction unit 1005 can change the travel path R1 to the travel path R1' shown in Fig. 12 correct.

[0068] As described above, the first position error is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after loading the pallet 20, δ p ' (δ x ', δ y'). The first angular error, which is an angular error after loading in the pallet 20 with respect to the fork 11, is θ'. The corrected travel path R1' is a travel path in which the forklift device 10 turns at a turn start location F' located before a turn start location F of the intended travel path R1 by a distance L4, turns by an angle (90-θ') with a turning radius r, travels along a distance L5 after turning, and stops, as shown in Fig. 12. The turning radius r does not change before and after the correction of the travel path R1.

[0069] As described with reference to Fig. 11, it is assumed that -a = -δ x 'cosθ-δ y 'sinθ and -b = δ x 'sinθ-δ y 'cosθ must be fulfilled. At this time, as shown in Fig. 12, L3 = L1+rsinθ-b, L2 = (L1+rsinθ-b)tanθ, L4 = rcosθ+L2+ar and L5=(L1-b)÷cosθ+rtanθ are satisfied.

[0070] Accordingly, the travel path R1' is a travel path in which the forklift device 10 starts before the turning start location F of the preset travel path R1 by L4 = rcosθ+(L1+rsinθ-b)tanθ+ar, turns by an angle (90-θ') to a turning radius r, travels by L5=(L1-b)÷cosθ+rtanθ after turning, and stops.

[0071] The forklift device 10 then conveys the pallet 20 along the corrected travel path R1' (step S108). Specifically, the conveyance travel control unit 1006 controls operation of the travel motor 102 such that the forklift device 10 travels along the corrected travel path R1.

[0072] Subsequently, the fork motor 101 performs stacking at the stacking position B' (step S109). Specifically, the conveyance control unit 1006 controls operation of the fork motor 101 such that the forklift device 10 stacks the pallet 20 at the stacking position B'.

[0073] As described above, the process content in which the forklift device 10 faces the pallet 20 before loading the pallet 20 for unloading, and then loads the pallet 20, travels, and performs stacking has been described. A time point at which the pallet 20 is loaded within the process flow may be the time points of the various detections and the time points of the predictions in parallel, before, or after each other. Specifically, the time point at which the travel path R1 is set (step S106) and the time point at which the travel path R1 is corrected (step S107) may be any time point after the prediction of the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after loading and can therefore be before step S105 in which the pallet 20 is loaded.

[0074] The forklift device 10 according to the first embodiment comprises; the error prediction unit 1003 configured to calculate the first position error δ p ', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 is loaded, to predict the first angular error θ', which is an angular error after loading with respect to the fork 11 in the pallet 20, and to predict the center of gravity position δ g ' after loading; the travel path correction unit 1005 is configured to correct the travel path R1 from the loading position A of the pallet 20 to the stacking position B of the pallet 20 to compensate for the first position error δ p' and compensate for the first angular error θ' when the pallet 20 is stacked; and the conveying travel control unit 1006 configured to perform travel control such that the pallet 20 is conveyed along the corrected travel path R1'.

[0075] Therefore, in the first embodiment, since separate operations such as side shifting of the fork and intermittent adjustment of the fork are not necessary in the process of correcting the error (the stacking error) that occurs when the forklift device 10 is loading and then starting the cargo 22, a cycle time of the work of the forklift device can be shortened and therefore the conveyance of the cargo by the forklift device can be performed quickly.

[0076] Furthermore, in the process of correcting the stacking error only by correcting the travel path without providing, for example, separate devices such as a fork side shifting mechanism and a fork pitch adjusting mechanism, the process of correcting the error can be easily performed at a low cost.

[0077] The forklift device 10 according to the first embodiment has been described in detail above. However, a specific aspect of the forklift device 10 is not limited to the above description, and various design modifications can be made within the scope of the present disclosure without departing from the gist of the present disclosure.

[0078] For example, in the forklift device 10 according to the first embodiment, in step S104, the Fig. 9 the error prediction unit 1003 the first position error δ p', the first angular error θ' and the center of gravity position δ g ' after charging based on the detected relative position δ p before charging, the recorded relative angle θ before charging and the recorded center of gravity position δ g before charging, as described above.

[0079] Here, as a first modification example of the first embodiment, the error prediction unit 1003 may calculate the first position error δ p ' and the first angular error θ' without using the center of gravity position δ g predict before charging.

[0080] In particular, based on the detected relative position δ p before charging, the detected relative angle θ before charging and the predefined error information 1041, the error prediction unit 1003 predicts the first position error δ p', which is a position error after loading between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the pallet 20 has been loaded, for unloading and the first angular error θ', which is an angular error after loading the pallet 20 with respect to the fork 11. Here, the error information is 1041 information, where the relative position δ p before charging and the relative angle θ before charging are related to the first position error δ p ' and the first angular error θ'. Accordingly, based on the detected relative position δ p before charging and the detected relative angle θ before charging, the error prediction unit 1003 calculates the first position error δ p ' and predict the first angular error θ' in real time without physical analysis.

[0081] Therefore, it is possible to calculate a time necessary to perform the physical analysis of the first position error δ p ' and the first angular error θ' in real time.

[0082] This allows even if the center of gravity position δ g the load 22 is not detected, the error prediction unit 1003 calculates the first position error δ p ' and predict the first angular error θ'. The first modification example of the first embodiment is effective in a case where there is no variation / variation in the center of gravity position of the load 22 on the pallet 20 or the like.

[0083] Hereinafter, the forklift device 10 according to a second embodiment will be described with reference to Fig. 13 and Fig. 14 are described.

[0084] Fig. 13 is an explanatory diagram showing a functional structure of the forklift device 10 according to the second embodiment.

[0085] As shown in Fig. 13, the central processing unit (CPU) 100 of the forklift device 10 according to the second embodiment further performs a function of a follow-up error prediction unit 1007 in addition to the first embodiment. Accordingly, each constituent element other than the follow-up error prediction unit 1007 in the forklift device 10 according to the second embodiment is configured to function similarly to each constituent element of the forklift device 10 according to the first embodiment, unless otherwise specified.

[0086] Based on the first position error δ p ' and the first angular error θ', the tracking error prediction unit 1007 predicts a second position error δ p'', which is a position error after the travel, and a second angular error θ'', which is an angular error after the travel, occurring from the charging position A to the stacking position B. For example, the post-travel error prediction unit 1007 can predict the second position error δ p '' and the second angular error θ'' based on the first position error δ p ', the first angular error θ', the center of gravity position δ g ' after loading, the travel distance R1, a travel speed, an amount of inclination, the weight of the load 22, a friction coefficient between the fork 11 and the pallet 20 and the like.

[0087] The travel path correction unit 1005 corrects the travel path R1, which is set in advance from the loading position A of the pallet 20 to the stacking position B of the pallet 20, by a stacking error caused by the second position error δ p'' and the second angular error θ'' when the pallet 20 is stacked. (Process flow of the forklift device 10)

[0088] Fig. 14 is an explanatory diagram showing a process flow of the forklift device 10 according to the second embodiment.

[0089] The process flow of the forklift device 10 according to the second embodiment shown in Fig. 14 is different from the process flow of the forklift device 10 according to the first embodiment shown in Fig. 9, in that steps S201 and S202 are added. In the forklift device 10 according to the second embodiment, the operations except for steps S201 and S202 are similar to the operations of the forklift device 10 according to the first embodiment. Therefore, the different operations will be described below.

[0090] As shown in Fig. 14, first, the operations of steps S101 to S105 are performed similarly to the first embodiment.

[0091] Then, after the process of step S105, the process of step S201 is performed. This means that the tracking error prediction unit 1007 of the forklift device 10 calculates the second position error δ p '', which is a position error after traveling from the loading position A to the stacking position B, and the second angular error θ'', which is an angular error after traveling, by applying the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after loading to a deviation amount prediction model (step S201). Here, the deviation amount prediction model is a model, e.g., a calculation expression for predicting the second position error δ p'' and the second angular error θ'' from predicted values ​​before loading the pallet 20 (the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after loading), the information obtained by the travel program (the travel path R1, the travel speed and the amount of inclination) and the known information (the weight of the load 22 and the coefficient of friction between the fork 11 and the pallet 20).

[0092] After step S201, the process of step S106 is performed similarly to the first embodiment.

[0093] Then, after the process of step S106, the process of step S202 is performed. That is, the travel path correction unit 1005 of the forklift device 10 corrects the travel path R1, which is set in advance, from the loading position A of the pallet 20 to the stacking position B of the pallet 20 in order to correct the stacking error caused by the second position error δ p '' and the second angle error θ'' when the pallet 20 is stacked (step S202).

[0094] The operations of steps S108 and S109 are then performed as in the first embodiment to complete the process of the flow shown in Fig. 14 to complete.

[0095] As described above, the process flow in which the forklift device 10 faces the pallet 20 before loading the pallet 20 for unloading, then loads the pallet 20, moves it, and performs stacking has been described. A time point at which the pallet 20 is loaded in the process flow and the times of the various detections and predictions can be performed in parallel, before each other, or sequentially. In particular, the times of steps S201, S106, and S202 can be set at any time of the prediction of the first position error δ. p ', the first angular error θ' and the center of gravity position δ g ' after loading and can therefore be before step S105 in which the pallet 20 is loaded.

[0096] The forklift device 10 according to the second embodiment comprises: the tracking error prediction unit 1007 configured to calculate the second position error δp '', which is a position error after traveling between the standard position M of the fork 11 and the center position O of the pallet 20 on the fork 11 after the forklift device 10 has traveled, and to predict the second angular error θ'', which is an angular error after traveling with respect to the fork 11 in the pallet 20; the travel path correction unit 1005, which is configured to correct the travel path R1 from the loading position A of the pallet 20 to the stacking position B of the pallet 20 to calculate the second position error δ p '' and compensate / reset the second angular error θ'' when the pallet 20 is stacked; and the conveying travel control unit 1006, which is configured to perform travel control such that the pallet 20 is conveyed along the corrected travel path R1'.

[0097] Therefore, because separate operations such as fork side shifting and fork pitch adjustment are not necessary in the process of correcting the error (stacking error) that occurs when the forklift device 10 loads and then stacks the load 22, a cycle time of the work of the forklift device can be shortened, and therefore, conveyance of the load by the forklift device can be carried out quickly.

[0098] In addition, because the operation of correcting the stacking error can be performed only by correcting the travel path without, for example, providing separate devices such as a side switching mechanism / side switching mechanism of the fork and a fork pitch adjusting mechanism of the fork, the operation of correcting the error can be performed easily and at a low cost.

[0099] With respect to the position of the pallet 20 on the fork 11, an error occurs not only during the operation of loading the pallet 20, but also during traveling. According to the second embodiment, since the error from loading the pallet 20 to stacking the pallet 20 can be compensated, the error at the stacking position B can be more compensated / better compensated than in the first embodiment in which only the error during loading the pallet 20 is compensated. As completely unmanned distribution operations in a warehouse become widespread, high-speed travel and high-speed unloading operations of an unmanned forklift will be required in the future. Therefore, the dynamic action of the pallet on the fork becomes large, and the error during traveling increases.Even in this case, in the forklift device 10 according to the second embodiment, it is possible to effectively reset / compensate the stacking error.

[0100] The forklift device 10 according to the second embodiment has been described in detail above. However, a specific aspect of the forklift device 10 is not limited to the above description, and various design variations may be made within the scope of the present disclosure without departing from the gist of the present disclosure.

[0101] For example, in the forklift device 10 according to the second embodiment, in step S201, the Fig. 14, the tracking error prediction unit 1007 calculates the second position error δ p '' and the second angular error θ'', which is calculated from the loading position A to the stacking position B based on the first position error δ p', the first angular error θ', the center of gravity position δ g ' after charging as described above.

[0102] Here, as a first modification example of the second embodiment, the tracking error prediction unit 1007 may calculate the second position error δ p '' and the second angular error θ'' without using the center of gravity position δ g ' after charging.

[0103] In particular, the tracking error prediction unit 1007 may calculate the second position error δ p '' and the second angular error θ'' by applying the first position error δ p ', the first angular error θ', the travel distance R1, the travel speed, the amount of inclination, the weight of the load 22 and the friction coefficient between the fork 11 and the pallet 20 to a deviation amount prediction model.

[0104] In addition, the tracking error prediction unit 1007 may calculate the second position error δ p '' and predict the second angular error θ'' using a deviation amount prediction model without using at least one of the traveling distance R1, the traveling speed, the inclination amount, the weight of the load 22, and the friction coefficient between the fork 11 and the pallet 20.

[0105] By doing this, even if the center of gravity position δ g the load 22 is not detected and the center of gravity position δ g ' after charging is not predicted, the tracking error prediction unit 1007 calculates the second position error δ p '' and the second angular error θ''. In addition, it is possible to reduce the time required to predict the second position error δ p '' and the second angular error θ'' by not using the center of gravity position δ g' after loading for prediction. The first modification example of the second embodiment is effective in a case where there is no fluctuation in the center of gravity position of the load 22 on the pallet 20 or the like.

[0106] Hereinafter, the forklift device 10 according to a third embodiment will be described with reference to Fig. 15 are described.

[0107] A functional structure of the forklift device 10 according to the third embodiment is arranged to function similarly to each constituent element of the forklift device 10 according to the first or second embodiment unless otherwise stated.

[0108] The travel path setting unit 1004 also sets a travel path from a current position of the forklift device 10 to the loading position A of the pallet 20 before the forklift device 10 loads the pallet 20.

[0109] The travel path correction unit 1005 also corrects the travel path until the pallet is loaded such that the first position error δ p ' and the first angular error θ' are further reduced when the pallet 20 is loaded. The error prediction unit 1003 also continues to predict the first position error δ p ' and the first angular error θ' occurring at the time of loading the pallet 20 along the corrected travel path.

[0110] The conveyor travel control unit 1006 also loads the pallet 20 along the corrected travel path until the pallet 20 is loaded.

[0111] Fig. 15 is an explanatory diagram showing a process flow of the forklift device 10 according to a third embodiment.

[0112] The process flow of the forklift device 10 according to the third embodiment shown in Fig. 15 is different from the process flow of the forklift device 10 according to the first embodiment shown in Fig. 9 or to the process flow of the forklift device 10 according to the second embodiment shown in Fig. 14 in that steps S301 to S304 are further added. In the forklift device 10 according to the third embodiment, operations other than steps S301 to S304 are similar to the operations of the forklift device 10 according to the first or second embodiment. Therefore, the different operations will be described below.

[0113] As shown in Fig. 15, first, the operations of steps S101 to S104 are performed similarly to the first embodiment.

[0114] Then, after the process of step S104, the process of step S301 is performed. That is, the travel path setting unit 1004 sets the travel path from the current position of the forklift device 10 to the loading position A of the pallet 20 before the forklift device 10 loads the pallet 20 (step S301).

[0115] The travel path correction unit 1005 then corrects the travel path until the pallet is loaded in such a way that the first position error δ p ' and the first angular error θ' predicted at the time of loading the pallet 20 in step S104 (step S302) are further reduced. The error prediction unit 1003 again predicts the first position error δ p ', which is a position error, the first angular error θ', which is an angular error after charging, and the center of gravity position δ g' after loading, which occur when the pallet 20 is loaded along the corrected travel path (step S303).

[0116] The conveyor travel control unit 1006 then loads the pallet 20 along the corrected travel path until the pallet 20 is loaded (step S304).

[0117] The operations of steps S201, S106, S202, S108 and S109 are sequentially performed as in the first or second embodiment to complete the process of the flow shown in Fig. 15, to be completed.

[0118] As described above, the process flow in which the forklift device 10 faces the pallet 20 before loading the pallet 20 for unloading, then picks up the pallet 20, moves it, and performs the stacking has been described. A time point at which the pallet 20 is loaded in the process flow, times of the various detections, and times of the predictions can be performed in parallel, before each other, or sequentially. In particular, the times of steps S201, S106, and S202 can occur at any time after step S303 in which the first position error δ p ', the first angular error θ' and the center of gravity position δ g ' after loading, and therefore they may be before step S304 in which the pallet 20 is loaded.

[0119] In the forklift device 10 according to the third embodiment, the travel path correction unit 1005 corrects the travel path until the pallet is loaded such that the first position error δ p ' and the first angular error θ' are further reduced when the pallet 20 is loaded. The error prediction unit 1003 further predicts the first position error δ p ', which is a position error, and the first angular error θ', which is an angular error after loading, which occur at the time of loading the pallet 20 along the corrected travel path. The conveyor travel control unit 1006 also loads the pallet 20 along the corrected travel path until the pallet 20 is loaded.

[0120] Because the travel path is corrected before the forklift device 10 loads the pallet 20, the first position error δ p' and the first angular error θ' can be further reduced. As a result, the forklift device 10 can load the pallet 20 at a safer position on the fork 11 and safely convey the pallet 20.

[0121] The forklift device 10 according to the third embodiment has been described in detail above. However, a specific aspect of the forklift device 10 is not limited to the above description, and various design variations may be made within the scope of the present disclosure without departing from the gist of the present disclosure.

[0122] For example, in the forklift device 10 according to the third embodiment, in step S303, the Fig. 15 the error prediction unit 1003 again calculates the first position error δ p ', the first angular error θ' and the center of gravity position δ g' after loading, which occur at the time of loading the pallet 20 along the corrected travel path as described above.

[0123] Here, as a first modification example of the third embodiment, the error prediction unit 1003 may again only calculate the first position error δ p ' and the first angular error θ', which occur at the time of loading the pallet 20 along the corrected travel path, without re-predicting the center of gravity position δ g ' after charging. In particular, as described in the first modification example of the first embodiment, based on the detected relative position δ p before charging, the detected relative angle θ before charging and the predefined error information 1041, the error prediction unit 1003 after charging the first position error δ p' before, which is a position error between the standard position M of the fork 11 and the center position O of the pallet 20 of the fork 11 after the pallet 20 is loaded for unloading and the first angle error θ', which is an angle error after loading the pallet 20 with respect to the fork 11. Here, the error information is 1041 information in which the relative position δ p before charging and the relative angle θ before charging with the first position error δ p ' and the first angular error θ'. Accordingly, based on the detected relative position δ p before charging and the detected relative angle θ before charging, the error prediction unit 1003 calculates the first position error δ p' and the first angular error θ' in real time without physical analysis. Then, before the forklift device 10 loads the pallet 20, the travel path setting unit 1004 sets the travel path from the current position of the forklift device 10 to the loading position A of the pallet 20. Then, the travel path correction unit 1005 corrects the travel path until the pallet is loaded such that the first position error δ p ' and the first angular error θ' at the time of loading the pallet 20, which were predicted in step S104, are further reduced. The error prediction unit 1003 again predicts the first position error δ p ' and the first angular error θ', which occur when the pallet 20 is loaded along the corrected travel path, without re-predicting the center of gravity position δ g ' after charging.

[0124] This allows even if the center of gravity position δ gthe load 22 is not detected, the error prediction unit 1003 calculates the first position error δ p ' and predict the first angular error θ'. The first modification example of the third embodiment is effective in a case where there is no change in the center of gravity position of the load 22 on the pallet 20 or the like.

[0125] As described above, several embodiments of the present disclosure have been described, but all embodiments are proposed as examples and are not intended to limit the scope of the present disclosure. The embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the present disclosure. The embodiments and variations are included in the present disclosure, described in the claims, and within the range of equivalents, as long as the embodiments of the variations are included within the scope or spirit of the present disclosure.

[0126] The sequence of each operation in the central processing unit (CPU) 100 described above is stored on a computer-readable storage medium in the format of a program, and the preceding operations are performed when the central processing unit (CPU) 100 reads and executes the program. Here, the computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. The computer program can be delivered to a computer via a communication line, and the computer (the central processing unit (CPU) 100) to which the computer program is delivered can execute the program.

[0127] The program can be configured to implement some of the functions described above. Furthermore, the program can also be a program in which the functions described above can be implemented in combination with a program already stored on a computer system, a so-called differential file (differential program). The computer (the central processing unit (CPU) 100) can be equipped with one computer or with a plurality of computers connected in a communicable manner.

[0128] According to a second aspect of the present invention, the forklift device may further include a relative position angle detection unit configured to detect a pre-loading relative position between the standard position of the fork and a center position of the pallet before the pallet is loaded, and a pre-loading relative angle with respect to the fork of the pallet. The error prediction unit may calculate the first position error and the first angle error based on the pre-loading relative position and the pre-loading relative angle.

[0129] According to a third aspect of the present invention, the forklift device may further comprise a storage unit configured to store error information in which the relative position before loading and the relative angle before loading are correlated with the first position error and the first angle error. The error prediction unit may predict the first position error and the first angle error based on the error information.

[0130] According to a fourth aspect of the present invention, the forklift device may further include a center of gravity position detection unit configured to detect a pre-loading center of gravity position in a load on the pallet before the pallet is loaded. Based on the pre-loading center of gravity position and the error information, the error prediction unit may predict the first position error, the first angle error, and a post-loading center of gravity position in the load on the pallet after the pallet is loaded.The error information may further include: the center of gravity position before charging and the center of gravity position after charging and the relative position before charging, the relative angle before charging and the center of gravity position before charging, which are stored in accordance with the first position error, the first angle error and the center of gravity position after charging for storage.

[0131] According to a fifth aspect of the present invention, based on the relative position before loading and the relative angle before loading, the travel path correction unit can further correct a travel path until the pallet is loaded such that the first position error and the first angle error are further reduced. Furthermore, the conveying travel control unit can cause the pallet to be loaded along the corrected travel path until the pallet is loaded.

[0132] According to a sixth aspect of the present invention, the error prediction unit may further include a post-travel error prediction unit that predicts a second position error, which is a position error after travel, and a second angle error, which is an angle error after travel, that occur from the loading position to the stacking position based on the first position error and the first angle error. The travel path correction unit may further correct the travel path from the loading position to the stacking position to compensate for / reset the second position error and the second angle error when the pallet is stacked.

[0133] According to a seventh aspect of the present invention, there is provided a forklift control method comprising: predicting a first position error, which is a post-loading position error between a standard position of a fork and a center position of a pallet on the fork after the pallet is loaded, and a first angle error, which is a post-loading angle error with respect to the fork in the pallet; correcting a travel path from a pallet loading position to a pallet stacking position to compensate for / reset the first position error and the first angle error when the pallet is stacked; and performing travel control such that the pallet is conveyed along the corrected travel path.

[0134] According to an eighth aspect of the present invention, there is provided a program that causes a computer of a forklift device traveling along a travel path to perform: predicting a first positional error, which is a post-loading positional error, between a standard position of a fork and a center position of a pallet on the fork after the pallet is loaded, and a first angular error, which is a post-loading angular error with respect to the fork in the pallet; correcting the travel path from a pallet loading position to a pallet stacking position to compensate for / reset the first positional error and the first angular error when the pallet is stacked; and executing travel control such that the pallet is conveyed along the corrected travel path.

[0135] Furthermore, the constituent elements in the foregoing embodiments can be appropriately replaced with known constituent elements within the scope of the present disclosure without departing from the gist of the present disclosure. Furthermore, the technical scope of the present disclosure is not limited to the foregoing embodiments, and many modifications can be made within the scope of the present disclosure without departing from the gist of the present disclosure. 10 Forklift device 11 Fork 20 pallets 21 holes 22 cargo 100 central processing unit (CPU) 1001 Relative position angle detection unit 1002 Center of gravity position detection unit 1003 Error prediction unit 1004 route setting unit 1005 Travel path correction unit 1006 Conveyor control unit 1007 Follow-up error prediction unit 101 Fork motor 102 Traction motor 103 Camera 104 storage unit 1041 Error information 1042 route information

Claims

[1] A forklift device comprising: an error prediction unit (1003) configured to predict, after a pallet (20) is loaded, a first position error, which is a position error between a standard position of a fork (11) and a center position of the pallet (20) on the fork (11) after loading, and a first angle error, which is an angle error of the pallet (20) with respect to the fork (11) after loading; a travel path correction unit (1005) configured to correct a travel path previously set from a loading position of the pallet (20) to a stacking position of the pallet (20) to compensate for the first position error and the first angle error when the pallet (20) is stacked; and a conveying travel control unit (1006) configured to perform travel control so that the pallet (20) is conveyed along the corrected travel path. [2] The forklift device according to claim 1, further comprising: a relative position angle detection unit (1001) configured to detect a relative position between the standard position of the fork (11) and the center position of the pallet (20) before loading, and a relative angle of the pallet (20) before loading with respect to the fork (11), wherein the error prediction unit (1003) is configured to predict the first position error and the first angle error based on the relative position before charging and the relative angle before charging. [3] The forklift device according to claim 2, further comprising: a storage unit (104) configured to store error information by relating the relative position before charging and the relative angle before charging to the first position error and the first angle error; wherein the error prediction unit (1003) is configured to predict the first position error and the first angle error based on the error information. [4] The forklift device according to claim 3, further comprising: a center of gravity position detection unit (1002) configured to detect a center of gravity position in a load on the pallet (20) before the pallet (20) is loaded, wherein the error prediction unit (1003) is configured to predict, based on the center of gravity position before loading and the error information, the first position error, the first angle error and a center of gravity position of the load after loading on the pallet (20) after the pallet (20) is loaded, and wherein the error information further includes the center of gravity position before charging and the center of gravity position after charging, and wherein the relative position before charging, the relative angle before charging, and the center of gravity position before charging are stored in accordance with the first position error, the first angle error, and the center of gravity position after charging. [5] The forklift device according to any one of claims 2 to 4, wherein, furthermore, based on the relative position before loading and the relative angle before loading, the travel path correction unit (1005) is configured to correct a travel path until the pallet (20) is loaded, so that the first position error and the first angle error are further reduced, and wherein the conveyor travel control unit (1006) is further configured to cause the pallet (20) to be loaded to be loaded along the corrected travel path until the pallet (20) is loaded. [6] The forklift device according to any one of claims 1 to 5, wherein the error prediction unit (1003) further comprises a post-travel error prediction unit (1007) configured to predict a second position error, which is a position error after the travel, and a second angle error, which is an angle error after the travel, occurring from the loading position to the stacking position based on the first position error and the first angle error, and wherein the travel path correction unit (1005) is further configured to correct the travel path from the loading position to the stacking position to compensate for the second position error and the second angle error when the pallet (20) is stacked. [7] A forklift control method comprising: Predicting a first position error, which is a position error after loading, between a standard position of a fork (11) and a center position of a pallet (20) on the fork (11) after the pallet (20) is loaded, and a first angular error, which is an angular error after loading the pallet (20) with respect to the fork (11); Correcting a travel path previously determined from a loading position of the pallet (20) to a stacking position of the pallet (20) to compensate for the first position error and the first angle error when the pallet (20) is stacked; and Carrying out a travel control such that the pallet (20) is conveyed along the corrected travel path. [8] A program which causes a computer of a forklift device travelling along a travel path to execute: predicting a first position error, which is a position error between a standard position of a fork (11) and a center position of a pallet (20) on the fork (11) after loading, after the pallet (20) is loaded, and a first angle error, which is an angle error of the pallet (20) with respect to the fork (11) after loading; Correcting the travel path, which was previously determined from a loading position of the pallet (20) to a stacking position of the pallet (20), to compensate for the first position error and the first angle error when the pallet (20) is stacked; and Carrying out a travel control such that the pallet (20) is conveyed along the corrected travel path.

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