Controller, control system, control method, and program

Abstract

To provide a controller, control system, control method, and program capable of inhibiting a yaw angle deviation from occurring at a time of changing maneuvering modes.SOLUTION: A controller is incorporated in a vehicle including a vehicle body, and three wheels that are mounted on the vehicle body, can rotate about a drive axis line extending in a horizontal direction, and can be steered about a steering axis line extending in a vertical direction. The controller includes a first steering unit that steers two first wheels out of the three wheels from a first change initiation direction to a first intermediate direction, and thus causes drive axis lines of the two first wheels to intersect at one intersection, which is located outside the vehicle body, when seen in the vertical direction, and a second steering unit that steers the remaining one second wheel out of the three wheels from a second change initiation direction to a second change termination direction after an intersection is formed. After the second wheel is steered to the second change termination direction, the first steering unit steers the two first wheels from the first intermediate direction to a first change termination direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a control system, a control method, and a program. [Background technology]

[0002] Patent Document 1 discloses a reach forklift truck. This forklift truck includes a vehicle body, a pair of front wheels (left and right), and rear wheels driven by a travel motor.

[0003] Furthermore, Patent Document 2 discloses a steering method for an automated guided vehicle. In this steering method, the front and rear wheels are steered in opposite phases to turn the vehicle at a predetermined radius. At the start and end of the turn, the rear wheels are steered so as to face the traveling direction of the front wheels. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-43357 [Patent Document 2] Patent No. 3329963 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a forklift truck as disclosed in Patent Document 1 that is remotely and automatically controlled, or in the case of an autonomous forklift truck, if stationary steering is performed when switching from a straight-line mode to a lateral movement mode or from a straight-line mode to a turning mode, a deviation in the yaw angle of the vehicle body occurs. In addition, because the three wheels are steered simultaneously, there is a time before the mode change is completed when, viewed from above, the drive axes of the three wheels intersect and the tires are positioned in a way that makes it easier for the vehicle to rotate at a yaw angle.

[0006] Furthermore, in the steering method disclosed in Patent Document 2, the axles are steered to converge at one point when turning, which makes it more likely that yaw angle deviation will occur when switching driving modes by stationary steering. In particular, when the vehicle is automatically controlled, the driver is not on board the vehicle, and therefore the yaw angle deviation cannot be finely adjusted by the driver's operation.

[0007] The present disclosure has been made to solve the above-mentioned problem, and aims to provide a control device, a control system, a control method, and a program that can suppress yaw angle deviation when switching steering modes. [Means for solving the problem]

[0008] In order to solve the above problem, the control device of the present disclosure is a control device for a vehicle having a vehicle body and three wheels mounted on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and is equipped with a first steering unit that steers two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection located outside the vehicle body when viewed in the vertical direction, and a second steering unit that steers the remaining one second wheel of the three wheels from a second switching start orientation to a second switching end orientation after the intersection is formed, and after the second wheel is steered to the second switching end orientation, the first steering unit steers the two first wheels from the first intermediate orientation to the first switching end orientation.

[0009] The control device according to the present disclosure is a control device for a vehicle having a vehicle body and three wheels mounted on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and includes a first steering unit that steers two of the three wheels (first wheels) from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection when viewed in the vertical direction, and a second steering unit that, after the intersection is formed, steers the remaining one of the three wheels (second wheel) from a second switching start orientation to a second switching end orientation so that the drive axis of the second wheel does not pass through the intersection when viewed in the vertical direction, and after steering of the second wheel begins, the first steering unit steers the two first wheels from the first intermediate orientation to the first switching end orientation.

[0010] A control system according to the present disclosure includes the above-described control device and the vehicle.

[0011] The control method of the present disclosure is a control method for a vehicle having a vehicle body and three wheels provided on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and includes a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection located outside the vehicle body when viewed in the vertical direction, a second steering step of steering the remaining one second wheel of the three wheels from a second switching start orientation to a second switching end orientation after the intersection is formed, and a third steering step of steering the two first wheels from the first intermediate orientation to the first switching end orientation after the second wheel has been steered to the second switching end orientation.

[0012] The control method of the present disclosure is a control method for a vehicle having a vehicle body and three wheels provided on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and includes: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection when viewed in the vertical direction; a second steering step of steering the remaining one second wheel of the three wheels from a second switching start orientation to a second switching end orientation after the intersection is formed, so that the drive axis of the second wheel does not pass through the intersection when viewed in the vertical direction; and a step of steering the two first wheels from the first intermediate orientation to the first switching end orientation after steering of the second wheel begins.

[0013] The program of the present disclosure is a program for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and causes a computer to execute the following steps: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection located outside the vehicle body when viewed in the vertical direction; a second steering step of steering the remaining one second wheel of the three wheels from a second switching start orientation to a second switching end orientation after the intersection is formed; and a third steering step of steering the two first wheels from the first intermediate orientation to the first switching end orientation after the second wheel has been steered to the second switching end orientation.

[0014] The program according to the present disclosure is a program for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, rotatable around a drive axis extending horizontally and steerable around a steering axis extending vertically, and causes a computer to execute the following steps: a first steering step of steering two of the three wheels (first wheels) from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection when viewed in a vertical direction; a second steering step of steering the remaining one of the three wheels (second wheel) from a second switching start orientation to a second switching end orientation after the intersection is formed, so that the drive axis of the second wheel does not pass through the intersection when viewed in a vertical direction; and a step of steering the two first wheels from the first intermediate orientation to the first switching end orientation after steering of the second wheel begins. [Effects of the Invention]

[0015] According to the control device, control system, control method, and program of the present disclosure, it is possible to suppress yaw angle deviation when switching the steering mode. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram of a control system according to a first embodiment of the present disclosure, viewed from above. [Figure 2] FIG. 2 is a functional block diagram of a control device according to the first embodiment of the present disclosure. [Figure 3] 5 is a flowchart showing a procedure for switching between operation modes according to the first embodiment of the present disclosure. [Figure 4] FIG. 3 is a diagram showing an example of a first steering step according to the first embodiment of the present disclosure. [Figure 5] FIG. 4 is a diagram showing an example of a second steering step according to the first embodiment of the present disclosure. [Figure 6] FIG. 2 is a diagram illustrating a lateral movement mode according to the first embodiment of the present disclosure. [Figure 7] FIG. 10 is a diagram showing another example of the second steering step according to the first embodiment of the present disclosure. [Figure 8]FIG. 2 is a diagram illustrating an in-place rotation mode according to the first embodiment of the present disclosure. [Figure 9] 4 is a diagram illustrating an example of a point of action of a drive wheel when a rotation suppression mechanism according to the first embodiment of the present disclosure is in operation. FIG. [Figure 10] 5A to 5C are diagrams illustrating an effect of releasing the rotation suppression mechanism according to the first embodiment of the present disclosure. [Figure 11] 5A to 5C are diagrams illustrating an effect of releasing the rotation suppression mechanism according to the first embodiment of the present disclosure. [Figure 12] FIG. 10 is a schematic configuration diagram of a control system according to a second embodiment of the present disclosure, viewed from above. [Figure 13] FIG. 10 is a functional block diagram of a control device according to a second embodiment of the present disclosure. [Figure 14] 10 is a flowchart showing a procedure for switching between operation modes according to a second embodiment of the present disclosure. [Figure 15] FIG. 10 is a diagram showing an example of a first steering step according to a second embodiment of the present disclosure. [Figure 16] FIG. 10 is a diagram showing an example of a second steering step according to a second embodiment of the present disclosure. [Figure 17] FIG. 10 is a diagram illustrating a lateral movement mode according to a second embodiment of the present disclosure. [Figure 18] FIG. 10 is a diagram showing another example of the second steering step according to the second embodiment of the present disclosure. [Figure 19] FIG. 10 is a diagram illustrating an in-place rotation mode according to a second embodiment of the present disclosure. [Figure 20] 10 is a flowchart showing a procedure for switching between operation modes according to a modified example of the second embodiment of the present disclosure. [Figure 21] FIG. 10 is a diagram showing changes in the steering angle of each wheel over time in response to switching of the steering mode according to a modified example of the second embodiment of the present disclosure. [Figure 22] FIG. 22 is a diagram showing the orientation of each wheel at point A in FIG. 21 according to a modified example of the second embodiment of the present disclosure. [Figure 23] FIG. 22 is a diagram showing the orientation of each wheel at point B in FIG. 21 according to a modified example of the second embodiment of the present disclosure. [Figure 24] FIG. 22 is a diagram showing the orientation of each wheel at point C in FIG. 21 according to a modified example of the second embodiment of the present disclosure. [Figure 25] FIG. 1 is a hardware configuration diagram according to each embodiment and modified example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] First Embodiment (Control system configuration) Hereinafter, a control device 40, a control system 1, a control method, and a program according to a first embodiment of the present disclosure will be described with reference to FIGS. As shown in FIG. 1, the control system 1 includes a vehicle 2 and a control device 40.

[0018] (vehicle) The vehicle 2 of this embodiment is an autonomous forklift. The vehicle 2 is automatically controlled by a control device 40, which will be described later. Hereinafter, the longitudinal direction Ds of the vehicle 2 within the horizontal direction Dh will be simply referred to as the longitudinal direction Ds, and the vehicle width direction Dw of the vehicle 2 within the horizontal direction Dh will be simply referred to as the vehicle width direction Dw. Furthermore, the right side in the vehicle width direction Dw will be simply referred to as the "right side," and the left side in the vehicle width direction Dw will be simply referred to as the "left side." The vehicle 2 includes a vehicle body 10, a loading mechanism 20, a traveling motor 3, wheels 30, a rotation suppression mechanism 4, a steering device 5, and a vehicle-side control device 6.

[0019] (Body) The vehicle body 10 has a vehicle body main body 11 and straddle legs 12. Two straddle legs 12 are provided facing each other in the vehicle width direction Dw. The straddle legs 12 extend forward from the vehicle body main body 11.

[0020] (Loading mechanism) The loading mechanism 20 has a mast 21, a lift bracket 22, and a fork 23.

[0021] (mast) The masts 21 are attached to the front of the vehicle body 11. They extend in the vertical direction Dv. Two masts 21 are provided between the two straddle legs 12. The two masts 21 face each other in the vehicle width direction Dw. The two masts 21 are movable forward and backward in the fore-and-aft direction Ds along the straddle legs 12. The masts 21 can also be tilted by a tilt mechanism (not shown). This allows the masts 21 to take a position extending perpendicular to a horizontal plane along a vertical line, or a position tilted relative to the vertical line.

[0022] (Lift bracket) The lift bracket 22 is attached so as to span the two masts 21 in the vehicle width direction Dw. The lift bracket 22 can move along the masts 21 in the up-down direction Dv.

[0023] (fork) The fork 23 is attached to the lift bracket 22. The fork 23 is formed in an L shape when viewed in the vehicle width direction Dw. The fork 23 is fixed to the lift bracket 22. The fork 23 extends forward.

[0024] (Traction motor) The traveling motor 3 is provided on the vehicle body 10. The traveling motor 3 drives the driving wheels 30a, which will be described later.

[0025] (wheel) Three wheels 30 are provided on the vehicle body 10. Each wheel 30 is provided on the lower part of the vehicle body 10 and supports the vehicle body 10 from below. These three wheels 30 are provided so as to be rotatable independently about a driving axis O1. The driving axis O1 passes through the center of the wheel 30 and extends in the horizontal direction Dh. The rotation of the wheels 30 about the driving axis O1 enables the vehicle 2 to move straight or turn. These three wheels 30 are also provided so as to be steerable independently about a steering axis O2. The steering axis O2 passes through the center of the wheel 30 and extends in the vertical direction Dv. When the wheels 30 are steered, the driving axis O1 of the wheels 30 rotates about the steering axis O2. The three wheels 30 include one driving wheel 30a and two driven wheels 30b.

[0026] (Drive wheels) The drive wheel 30a is provided on the vehicle body 11. Here, an imaginary line passing through the center position of the vehicle body 10 in the vehicle width direction Dw and extending in the front-rear direction Ds is defined as a vehicle center line C. The drive wheel 30a is provided to the left of this vehicle center line C (upper side on the paper). The drive wheel 30a is driven by a travel motor 3.

[0027] (Driven wheel) The driven wheels 30b are provided at the front ends of the straddle legs 12. The driven wheels 30b rotate following the rotation of the drive wheels 30a. In this embodiment, two driven wheels 30b are provided. The two driven wheels 30b are provided as a pair at positions symmetrical to each other in the vehicle width direction Dw with respect to the vehicle center line C.

[0028] (Rotation suppression mechanism) The rotation suppression mechanism 4 suppresses rotation of the drive wheel 30a about the drive axis O1. The rotation suppression mechanism 4 suppresses rotation of the drive wheel 30a about the drive axis O1, for example, by applying a brake to the drive wheel 30a. Note that the rotation suppression mechanism 4 may also suppress rotation of the drive wheel 30a about the drive axis O1, for example, by applying a reverse drive force to the drive wheel 30a.

[0029] (Steering device) The steering device 5 steers the wheels 30. In the illustrated example, a mechanism for steering the drive wheels 30a is shown schematically. The steering device 5 for steering the driven wheels 30b is not shown. The steering device 5 is installed, for example, at a position horizontally offset from the drive wheels 30a, and supports the drive wheels 30a in a cantilever manner. Note that the arrangement and shape of the steering device 5 shown in the figure are merely an example and can be changed as appropriate.

[0030] (Vehicle control device) The vehicle-side control device 6 receives commands and the like from a control device 40 (described later) and operates various mechanisms that configure the vehicle 2, such as the rotation suppression mechanism 4 and the steering device 5.

[0031] (Control device) The control device 40 is provided separately from the vehicle 2. The control device 40 controls the movement of the vehicle 2 and switching of the vehicle 2's steering mode. The control device 40 steers the three wheels 30 to switch the vehicle 2's steering mode from a normal steering mode to a special steering mode. The normal steering modes include a straight-ahead mode in which the vehicle 2 moves straight in the fore-and-aft direction Ds, and a turning mode in which the vehicle 2 turns around a vertical axis on the outside of the vehicle 2. In the straight-ahead mode, the drive axes O1 of the three wheels 30 extend in the vehicle width direction Dw. In the turning mode, the inclination angle of the drive axes O1 of the two driven wheels 30b with respect to the vehicle center line C is smaller than the inclination angle of the drive axis O1 of the drive wheel 30a with respect to the vehicle center line C. The special steering modes include a lateral movement mode in which the vehicle 2 moves laterally in the vehicle width direction Dw, and an in-place rotation mode in which the vehicle 2 turns around a vertical axis passing through the vehicle 2. In the lateral movement mode, the drive axes O1 of the three wheels 30 extend in the fore-and-aft direction Ds. In the in-place turning mode, the drive axes O1 of the three wheels 30 intersect at a single point on the inside of the vehicle 2 when viewed in the up-down direction.

[0032] Here, the orientation of the first wheel 31 before the start of switching the steering mode is referred to as a first switching start orientation A1, and the orientation of the first wheel 31 after the switching of the steering mode is referred to as a first switching end orientation A3 (see FIGS. 6 and 8). The orientation of the first wheel 31 during the process of switching from the first switching start orientation A1 to the first switching end orientation A3 is referred to as a first intermediate orientation A2 (see FIG. 4). Furthermore, the orientation of the second wheel 32 before the start of switching the steering mode is referred to as a second switching start orientation B1, and the orientation of the second wheel 32 after the switching of the steering mode is referred to as a second switching end orientation B2 (see FIGS. 6 and 8).

[0033] The control device 40 has the following functional units: an acquisition unit 41, a rotation suppression operation unit 42, a first steering unit 43, a second steering unit 44, and an automatic steering unit 45.

[0034] (Acquisition Department) The acquisition unit 41 acquires information such as signals transmitted from the vehicle 2 and an external device (not shown) that transmits commands to the control device 40.

[0035] (Rotation suppression operation unit) The rotation suppression operation unit 42 sends a command to the vehicle-side control device 6 to operate the rotation suppression mechanism 4. Before the start of steering of the drive wheels 30a, the rotation suppression operation unit 42 causes the rotation suppression mechanism 4 to release the rotation suppression of the drive wheels 30a. Furthermore, until the steering of the drive wheels 30a is completed, the rotation suppression operation unit 42 maintains the state in which the rotation suppression of the drive wheels 30a by the rotation suppression mechanism 4 has been released.

[0036] (First steering section) The first steering unit 43 sends a command to the vehicle-side control device 6 to operate the steering device 5. The first steering unit 43 steers two of the three wheels 30. Hereinafter, the wheels 30 steered by the first steering unit 43 will be referred to as the first wheels 31. In this embodiment, the driven wheels 30b are the first wheels 31. Furthermore, when the driven wheels 30b are the first wheels 31 as in this embodiment, the first wheels 31 on the left side of the first wheels 31 will be referred to as the "left first wheel 31L," and the first wheels 31 on the right side of the first wheels 31 will be referred to as the "right first wheel 31R." The first steering unit 43 steers the two first wheels 31 from the first switching start orientation A1 to the first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 (see FIG. 4) located outside the vehicle body 10 when viewed in the up-down direction Dv. Furthermore, after the second wheels 32 described below are steered in the second switching end direction B2, the first steering unit 43 steers the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3.

[0037] (Second steering section) The second steering unit 44 sends a command to the vehicle-side control device 6 to operate the steering device 5. The second steering unit 44 steers the remaining one of the three wheels 30. Hereinafter, the wheel 30 steered by the second steering unit 44 will be referred to as the second wheel 32. In this embodiment, the drive wheel 30a is the second wheel 32. After the intersection P1 of the drive axes O1 of the two first wheels 31 is formed, the second steering unit 44 steers the one second wheel 32 from the second switching start orientation B1 to the second switching end orientation B2.

[0038] (Autopilot section) The autopilot unit 45 sends commands to the vehicle-side control device 6 to operate the travel motor 3, the rotation suppression mechanism 4, and the steering device 5. The autopilot unit 45 steers the vehicle 2 by rotating each wheel 30 about the drive axis O1. The autopilot unit 45 can rotate each wheel 30 about the drive axis O1 while maintaining the orientation of each wheel 30, or can rotate each wheel 30 about the drive axis O1 while steering it.

[0039] (Control method procedure) Hereinafter, the procedure of the control method for switching the operation mode of the vehicle 2 while the vehicle 2 is stopped will be described with reference to the flow shown in FIG. Before the switching of the steering mode is started, the rotation suppression mechanism 4 applies a brake or a reverse driving force to the drive wheels 30a to suppress the rotation of the drive wheels 30a.

[0040] Here, a method of controlling the vehicle 2 will be described using as an example a case where the steering mode of the vehicle 2 is switched from the straight-ahead mode (see FIG. 1) to the lateral movement mode (see FIG. 6). In the straight-ahead mode, as shown in FIG. 1, all three wheels 30 face in the longitudinal direction Ds. That is, in the straight-ahead mode, the drive axes O1 of the three wheels 30 all extend in the vehicle width direction Dw and are perpendicular to the vehicle center line C. In addition, in the lateral movement mode, as shown in FIG. 6, all three wheels 30 face in the vehicle width direction Dw. That is, in the lateral movement mode, the drive axes O1 of the three wheels 30 extend parallel to the vehicle center line C.

[0041] As shown in FIG. 3, the control method according to the embodiment of the present disclosure includes a switching start signal acquisition step S11, a rotation suppression release step S12, a first steering step S13, a second steering step S14, a third steering step S15, a switching end signal acquisition step S16, and a rotation suppression operation step S17.

[0042] (Switching start signal acquisition step) In the switching start signal acquisition step S11, the acquisition unit 41 acquires a signal to start switching of the steering mode from the vehicle 2 or an external device (not shown). After the switching start signal acquisition step S11, the rotation suppression release step S12 is performed.

[0043] (Rotation suppression release step) In the rotation suppression release step S12, the rotation suppression operation unit 42 causes the rotation suppression mechanism 4 to release the brake, reverse drive force, etc. applied to the drive wheel 30a and release the rotation suppression of the drive wheel 30a before steering of the drive wheel 30a begins (in this embodiment, before steering of any one of the three wheels 30 begins). After the rotation suppression release step S12, a first steering step S13 is performed. The rotation suppression operation unit 42 maintains the state in which the rotation suppression of the drive wheel 30a by the rotation suppression mechanism 4 has been released until steering of the drive wheel 30a is completed (in this embodiment, until steering of all three wheels 30 is completed).

[0044] (First steering step) As shown in FIG. 4, in the first steering step S13, the first steering unit 43 steers two first wheels 31 of the three wheels 30 from the first switching start orientation A1 to the first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at one intersection P1 as viewed in the up-down direction Dv. In the illustrated example, the intersection P1 is located on the vehicle center line C. Note that the intersection P1 does not have to be located on the vehicle center line C. Here, in the first switching start orientation A1, the drive axes O1 of the first wheels 31 extend in the vehicle width direction Dw. In the first steering step S13, the first steering unit 43 steers the two first wheels 31 in the first intermediate orientation A2 so that the two first wheels 31 form a V-shape that opens outward from the vehicle 2. As a result, when viewed in the up-down direction Dv, the intersection P1 of the drive axes O1 of the two first wheels 31 is formed on the outside of the vehicle body 10. The two first wheels 31 are steered in opposite directions. In this embodiment, the left-side first wheel 31L on the left side (upper side of the paper) is steered counterclockwise, and the right-side first wheel 31R on the right side (lower side of the paper) is steered clockwise. In addition, in a first steering step S13, the first steering unit 43 steers the two first wheels 31 so that the drive axes O1 of the two first wheels 31 are not aligned or parallel to each other. After the first steering step S13, a second steering step S14 is performed.

[0045] (Second steering step) As shown in FIG. 5, in the second steering step S14, after the intersection point P1 is formed in the first steering step S13, the second steering unit 44 steers the remaining one of the three wheels 30, the second wheel 32, from the second switching start orientation B1 to the second switching end orientation B2. Here, in the second switching start orientation B1, the drive axis O1 of the second wheel 32 extends in the vehicle width direction Dw, similar to the drive axis O1 of the first wheel 31. Furthermore, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 extends in the fore-and-aft direction Ds. That is, in the second steering step S14, the drive axis O1 of the second wheel 32 is rotated 90 degrees around the steering axis O2. In this embodiment, the second wheel 32 is steered counterclockwise. After the second steering step S14, a third steering step S15 is performed.

[0046] (Third steering step) As shown in Fig. 6, in the third steering step S15, after the second wheel 32 is steered to the second switching end orientation B2 in the second steering step S14, the two first wheels 31 are steered from the first intermediate orientation A2 to the first switching end orientation A3. Here, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 extends in the fore-and-aft direction Ds. That is, in the first steering step S13 and the third steering step S15, the drive axis O1 of the first wheel 31 is rotated 90 degrees around the steering axis O2. Note that in the third steering step S15, the two first wheels 31 are also steered in the same orientation as in the first steering step S13. Furthermore, in a third steering step S15, the first steering unit 43 steers the two first wheels 31 so that the drive axes O1 of the two first wheels 31 are not aligned or parallel to each other in any direction other than the first switching end orientation A3. After the third steering step S15, a switching end signal acquisition step S16 is performed.

[0047] (Switching end signal acquisition step) In the switching end signal acquisition step S16, the acquisition unit 41 acquires a signal to end the switching of the operation mode from the vehicle 2 or an external device (not shown). After the switching end signal acquisition step S16, the rotation suppression operation step S17 is performed.

[0048] (Rotation suppression operation step) In the rotation suppression operation step S17, the rotation suppression operating unit 42 causes the rotation suppression mechanism 4 to apply a brake or a reverse driving force to the drive wheel 30a, thereby suppressing the rotation of the drive wheel 30a. Through the above steps, the control mode is switched from the straight-line mode to the lateral movement mode.

[0049] Next, a case where the steering mode of the vehicle 2 is switched from the straight ahead mode (see FIG. 1) to the turn-on-the-spot mode (see FIG. 8) will be described.

[0050] 8, in the rotation-in-place mode, the drive axes O1 of the three wheels 30 intersect at a single point on the inside of the vehicle 2 when viewed in the vertical direction Dv. The vehicle 2 can rotate in place around a vertical vertical line that passes through this intersection point Pr.

[0051] When switching from the straight-ahead mode to the turn-on-the-spot mode, similar to when switching from the straight-ahead mode to the lateral movement mode, the control method includes a switching start signal acquisition step S11, a rotation suppression release step S12, a first steering step S13, a second steering step S14, a third steering step S15, a switching end signal acquisition step S16, and a rotation suppression activation step S17. However, when switching from the straight-ahead mode to the turn-on-the-spot mode, the steering direction of the wheels 30 in the second steering step S14 and the third steering step S15 differs from when switching from the straight-ahead mode to the lateral movement mode.

[0052] (Second steering step) 7, in the second steering step S14, the second steering unit 44 steers the second wheel 32 so that the second wheel 32 is inclined with respect to the fore-and-aft direction Ds and the vehicle width direction Dw. That is, in this case, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 is inclined with respect to the fore-and-aft direction Ds and the vehicle width direction Dw.

[0053] (Third steering step) 8, in the third steering step S15, the first steering unit 43 steers the two first wheels 31 in the first switching end orientation A3 so that the two first wheels 31 form a V-shape that opens toward the inside of the vehicle 2, and causes the drive axes O1 of the three wheels 30 to intersect at a single intersection point Pr located on the inside of the vehicle 2. That is, in this case, in the first switching end orientation A3, the drive axes O1 of the two first wheels 31 intersect with the drive axis O1 of the second wheel 32 at a single intersection point Pr. Through the above steps, the steering mode is switched from the straight-line mode to the rotation mode.

[0054] The vehicle 2, whose steering mode has been switched in the above-described manner, is automatically driven by the control device 40.

[0055] (Action and effect) According to this embodiment, the following effects are achieved.

[0056] In this embodiment, the control device 40 includes a first steering unit 43 and a second steering unit 44. The first steering unit 43 steers two first wheels 31 of the three wheels 30 from a first switching start orientation A1 to a first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 located outside the vehicle body 10 as viewed in the up-down direction Dv. After the intersection point P1 is formed, the second steering unit 44 steers the remaining second wheel 32 of the three wheels 30 from a second switching start orientation B1 to a second switching end orientation B2. After the second wheel 32 is steered to the second switching end orientation B2, the first steering unit 43 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3.

[0057] When switching the steering mode of the vehicle 2 (for example, from straight-ahead mode to sideways movement mode, or from straight-ahead mode to on-the-spot rotation mode), if the drive axes O1 of the three wheels 30 intersect at a single intersection when viewed in the vertical direction Dv, the vehicle 2 will be more likely to rotate around the vertical axis passing through that intersection, and even a small external force will cause a deviation in the yaw angle. In contrast, in this embodiment, the control device 40 first steers the two first wheels 31 in the first switching start orientation A1 to the first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 located outside the vehicle body 10 as viewed in the vertical direction Dv. Even if the control device 40 then steers the second wheel 32 so that the drive axis O1 of the second wheel 32 passes through the intersection point P1 and the drive axes O1 of the three wheels 30 intersect at the single intersection point P1, the distance (arm length) between the intersection point P1, which serves as the center of rotation, and the center of gravity of the vehicle 2 becomes longer, making it difficult for the vehicle 2 to rotate around the vertical axis. Therefore, the control device 40 can suppress yaw angle deviation when switching the steering mode.

[0058] In this embodiment, the vehicle 2 includes a traction motor 3 that drives the drive wheel 30a out of the three wheels 30, and a rotation suppression mechanism 4 that suppresses rotation of the drive wheel 30a. The control device 40 includes a rotation suppression operation unit 42 that causes the rotation suppression mechanism 4 to release the rotation suppression of the drive wheel 30a before steering of the first wheel 31 begins. The rotation suppression operation unit 42 maintains the state in which the rotation suppression of the drive wheel 30a by the rotation suppression mechanism 4 is released until the first wheel 31 is steered in the first switching end direction A3.

[0059] Because the tire width of the drive wheel 30a is wide, it is considered that the point of application Pa of the ground load is not on the steering axis O2 in many cases, as shown in Figure 9. In this way, if the drive wheel 30a is steered while the rotation suppression mechanism 4 suppresses the rotation of the drive wheel 30a in a state where the point of application Pa of the ground load is eccentric with respect to the steering axis O2, the point of application Pa of the ground load of the drive wheel 30a will not move, and a moment will be generated that rotates the vehicle body 10 in the yaw angle direction. This makes it easier for the yaw angle of the vehicle body 10 to shift. In contrast, in this embodiment, while the control device 40 steers the vehicle wheel 30, the rotation restriction of the drive wheel 30a is released. As a result, when the drive wheel 30a is steered, the application point Pa of the ground load of the drive wheel 30a is allowed to rotate about the steering axis O2, as shown in FIGS. 10 and 11. This suppresses the moment that rotates the vehicle body 10 in the yaw angle direction. Therefore, yaw angle deviation of the vehicle body 10 is further suppressed. Note that for simplification, FIGS. 10 and 11 only show the steering of the drive wheel 30a. In reality, during the process in which the drive wheel 30a (second wheel 32) is steered from the first switching start direction A1 to the first switching end direction A3 with the rotation restriction by the rotation suppression mechanism 4 released, the driven wheel 30b (first wheel 31) is also steered according to the procedure shown in the flow chart of FIG. 3 described above. Furthermore, in this embodiment, the two driven wheels 30b are arranged in a V-shape in the first intermediate direction A2 (see FIG. 4). Such a V-shape arrangement of the two driven wheels 30b suppresses yaw rotation of the entire vehicle 2. Therefore, even if the rotation suppression of the drive wheels 30a is released, yaw rotation of the entire vehicle 2 is suppressed. In this way, by switching the steering mode as described above while the rotation restriction on the drive wheels 30a is released, it is possible to further restrict the rotation of the yaw angle.

[0060] In this embodiment, the control device 40 includes an automatic steering unit 45 that steers the vehicle 2 by rotating the wheels 30 about the drive axis O1.

[0061] According to this embodiment, the control device 40 can automatically steer the vehicle 2 without requiring a driver to operate the vehicle 2. Incidentally, when a driver is on board the vehicle 2 and the vehicle 2 is manually operated by the driver, even if a yaw angle deviation occurs in the vehicle 2 when switching the operation mode of the vehicle 2, the driver can make fine adjustments to eliminate the yaw angle deviation. Generally, in many vehicles 2, including forklifts and automobiles, the point of application Pa of the ground load of the wheel 30 is not located on the steering axis O2 of the wheel 30. Therefore, when the vehicle 2 is steered while stopped, the vehicle body 10 inevitably deviates. Furthermore, aligning the steering axis O2 with the point of application Pa requires the steering device 5 to be located above the wheel 30, which increases the installation space and costs for the steering device 5. For these reasons, when a vehicle is manually operated by a driver, such as a manned forklift, the driver can make fine adjustments to eliminate a yaw angle deviation, and therefore, control to prevent a yaw angle deviation in the vehicle has not been a priority. On the other hand, when the vehicle 2 is automatically steered as in this embodiment, the yaw angle deviation of the vehicle 2 cannot be eliminated by fine adjustments by the driver. However, the control device 40 of this embodiment steers the three wheels 30 as described above, and therefore can suppress the occurrence of yaw angle deviation itself. Furthermore, in this embodiment, the rotation suppression operation unit 42 maintains the state in which the rotation suppression of the drive wheel 30a by the rotation suppression mechanism 4 is released until the first wheel 31 is steered in the first switching end orientation A3, and therefore yaw angle deviation hardly occurs. Therefore, the control device 40 can automatically steer the vehicle 2 without eliminating the yaw angle deviation of the vehicle 2 after switching the steering mode.

[0062] (Second embodiment) The second embodiment will be described below with reference to Figures 12 to 19. Among the configurations of the second embodiment, configurations common to the above-described embodiments will be given the same names and symbols, and descriptions thereof will be omitted as appropriate.

[0063] As shown in FIG. 12, in this embodiment, the control system 1 includes a vehicle 2 and a control device 50.

[0064] (Control device) As shown in FIG. 13, the control device 50 has the following functional units: an acquisition unit 51, a rotation suppression operation unit 52, a first steering unit 53, and a second steering unit .

[0065] (Acquisition Department) The acquisition unit 51 acquires information such as signals transmitted from the vehicle 2 or an external device (not shown).

[0066] (Rotation suppression operation unit) The rotation suppression operation unit 52 sends a command to the vehicle-side control device 6 to operate the rotation suppression mechanism 4. Before the start of steering of the drive wheels 30a, the rotation suppression operation unit 52 causes the rotation suppression mechanism 4 to release the rotation suppression of the drive wheels 30a. Furthermore, until the steering of the drive wheels 30a is completed, the rotation suppression operation unit 52 maintains the state in which the rotation suppression of the drive wheels 30a by the rotation suppression mechanism 4 has been released.

[0067] (First steering section) The first steering unit 53 sends a command to the vehicle-side control device 6 to operate the steering device 5. The first steering unit 53 steers two of the three wheels 30. Hereinafter, the wheels 30 steered by the first steering unit 53 will be referred to as the first wheels 31. In this embodiment, the driven wheels 30b are the first wheels 31. Furthermore, when the driven wheels 30b are the first wheels 31 as in this embodiment, the first wheels 31 on the left side of the first wheels 31 will be referred to as the "left first wheel 31L," and the first wheels 31 on the right side of the first wheels 31 will be referred to as the "right first wheel 31R." The first steering unit 53 steers the two first wheels 31 from the first switching start orientation A1 to the first intermediate orientation A2 (see FIG. 15), thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection P1 (see FIG. 15) as viewed in the up-down direction Dv. In this embodiment, when steering the two first wheels 31 from the first switching start orientation A1 to the first intermediate orientation A2, the first steering unit 53 forms the intersection point P1 at a position where the drive axis O1 of the second wheel 32 to be steered later does not pass through the intersection point P1. Furthermore, after starting to steer the second wheel 32, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to a first switching end orientation A3 (see FIGS. 17 and 19). In this embodiment, after the second wheel 32, which will be described later, is steered to the second switching end orientation B2 (see FIGS. 16 and 18), the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3.

[0068] (Second steering section) The second steering unit 54 sends a command to the vehicle-side control device 6 to operate the steering device 5. The second steering unit 54 steers the remaining one of the three wheels 30. Hereinafter, the wheel 30 steered by the second steering unit 54 will be referred to as the second wheel 32. In this embodiment, the drive wheel 30a is the second wheel 32. After the intersection P1 of the drive axes O1 of the two first wheels 31 is formed, the second steering unit 54 steers the one second wheel 32 from the second switching start orientation B1 to the second switching end orientation B2 so that the drive axis O1 of the second wheel 32 does not pass through the intersection P1 when viewed in the up-down direction Dv.

[0069] (Autopilot section) The autopilot unit 55 sends commands to the vehicle-side control device 6 to operate the travel motor 3, the rotation suppression mechanism 4, and the steering device 5. The autopilot unit 55 steers the vehicle 2 by rotating each wheel 30 about the drive axis O1. The autopilot unit 55 can rotate each wheel 30 about the drive axis O1 while maintaining the orientation of each wheel 30, or can rotate each wheel 30 about the drive axis O1 while steering it.

[0070] (Control method procedure) Hereinafter, the procedure of the control method for switching the steering mode of the vehicle 2 while the vehicle 2 is stopped will be described with reference to the flow shown in FIG. Before the switching of the steering mode is started, the rotation suppression mechanism 4 applies a brake or a reverse driving force to the drive wheels 30a to suppress the rotation of the drive wheels 30a.

[0071] Here, a method for controlling the vehicle 2 will be described using as an example a case where the steering mode of the vehicle 2 is switched from the straight ahead mode (see FIG. 12) to the lateral movement mode (see FIG. 17).

[0072] As shown in FIG. 14, the control method according to an embodiment of the present disclosure includes a switching start signal acquisition step S21, a rotation suppression release step S22, a first steering step S23, a second steering step S24, a third steering step S25, a switching end signal acquisition step S26, and a rotation suppression operation step S27.

[0073] (Switching start signal acquisition step) In the switching start signal acquisition step S21, the acquisition unit 51 acquires a signal to start switching of the steering mode from the vehicle 2 or an external device (not shown). After the switching start signal acquisition step S21, the rotation suppression release step S22 is performed.

[0074] (Rotation suppression release step) In the rotation suppression release step S22, the rotation suppression operation unit 42 causes the rotation suppression mechanism 4 to release the brake, reverse drive force, etc. applied to the drive wheel 30a and release the rotation suppression of the drive wheel 30a before steering of the drive wheel 30a begins (in this embodiment, before steering of any one of the three wheels 30 begins). After the rotation suppression release step S22, a first steering step S23 is performed. The rotation suppression operation unit 42 maintains the state in which the rotation suppression of the drive wheel 30a by the rotation suppression mechanism 4 has been released until steering of the drive wheel 30a is completed (in this embodiment, until steering of all three wheels 30 is completed).

[0075] (First steering step) 15, in a first steering step S23, the first steering unit 53 steers two first wheels 31 of the three wheels 30 from the first switching start orientation A1 to a first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 as viewed in the up-down direction Dv. Here, in the first switching start orientation A1, the drive axes O1 of the first wheels 31 extend in the vehicle width direction Dw. In the first steering step S23, the first steering unit 53 steers the two first wheels 31 in the first intermediate orientation A2 so that the two first wheels 31 form a V-shape that opens outward toward the outside of the vehicle 2. In this embodiment, when steering the two first wheels 31 from the first switching start orientation A1 to the first intermediate orientation A2, the first steering unit 53 forms the intersection point P1 at a position where the drive axis O1 of the second wheel 32 to be steered later does not pass through the intersection point P1. For example, the intersection point P1 of the drive axes O1 of the two first wheels 31 is formed to the left (upper side of the paper) in the vehicle width direction Dw of the steering axis O2 of the second wheel 32. The two first wheels 31 are steered in opposite directions to each other. In this embodiment, the left first wheel 31L on the left side (upper side of the paper) is steered counterclockwise, and the right first wheel 31R on the right side (lower side of the paper) is steered clockwise. In addition, in the first steering step S23, the first steering unit 53 steers the two first wheels 31 so that the drive axes O1 of the two first wheels 31 are not aligned or parallel to each other. After the first steering step S23, a second steering step S24 is performed.

[0076] (Second steering step) As shown in FIG. 16 , in the second steering step S24, after the intersection point P1 is formed in the first steering step S23, the second steering unit 54 steers the remaining one of the three wheels 30, the second wheel 32, from the second switching start orientation B1 to the second switching end orientation B2 so that the drive axis O1 of the second wheel 32 does not pass through the intersection point P1 when viewed in the up-down direction Dv. Here, in the second switching start orientation B1, the drive axis O1 of the second wheel 32 extends in the vehicle width direction Dw, similar to the drive axis O1 of the first wheel 31. Furthermore, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 extends in the fore-and-aft direction Ds. In this embodiment, in the second steering step S24, the drive axis O1 of the second wheel 32 is rotated 90 degrees around the steering axis O2. In this embodiment, the second wheel 32 is steered counterclockwise. As a result, the second wheel 32 is steered in the second switching end direction B2 without the drive axis O1 of the second wheel 32 passing through the intersection point P1.

[0077] After starting to steer the second wheels 32 as described above, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3. In this embodiment, after the second steering step S24, a third steering step S25 is performed as a step of steering the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3.

[0078] (Third steering step) As shown in FIG. 17 , in the third steering step S25, after the second wheel 32 is steered to the second switching end orientation B2 in the second steering step S24, the two first wheels 31 are steered from the first intermediate orientation A2 to the first switching end orientation A3. Here, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 extends in the fore-and-aft direction Ds. That is, in the first steering step S23 and the third steering step S25, the drive axis O1 of the first wheel 31 is rotated 90 degrees around the steering axis O2. Furthermore, in the third steering step S25, the first steering unit 53 steers the two first wheels 31 so that the drive axes O1 of the two first wheels 31 are not aligned or parallel to each other in any orientation other than the first switching end orientation A3. After the third steering step S25, a switching end signal acquisition step S26 is performed.

[0079] (Switching end signal acquisition step) In the switching end signal acquisition step S26, the acquisition unit 51 acquires a signal to end the switching of the operation mode from the vehicle 2 or an external device (not shown). After the switching end signal acquisition step S26, the rotation suppression operation step S27 is performed.

[0080] (Rotation suppression operation step) In the rotation suppression operation step S27, the rotation suppression operation unit 52 causes the rotation suppression mechanism 4 to apply a brake or a reverse driving force to the drive wheel 30a, thereby suppressing the rotation of the drive wheel 30a. Through the above steps, the control mode is switched from the straight-line mode to the lateral movement mode.

[0081] Next, a case where the steering mode of the vehicle 2 is switched from the straight ahead mode (see FIG. 12) to the turn-on-the-spot mode (see FIG. 19) will be described.

[0082] When switching from the straight-ahead mode to the turn-on-the-spot mode, the control method includes a switching start signal acquisition step S21, a rotation suppression release step S22, a first steering step S23, a second steering step S24, a third steering step S25, a switching end signal acquisition step S26, and a rotation suppression activation step S27, just like when switching from the straight-ahead mode to the lateral movement mode. However, when switching from the straight-ahead mode to the turn-on-the-spot mode, the steering direction of the wheels 30 in the second steering step S24 and the third steering step S25 differs from when switching from the straight-ahead mode to the lateral movement mode.

[0083] (Second steering step) 18, in the second steering step S24, the second steering unit 54 steers the second wheel 32 so that the second wheel 32 is inclined with respect to the fore-and-aft direction Ds and the vehicle width direction Dw. That is, in this case, in the second switching end orientation B2, the drive axis O1 of the second wheel 32 is inclined with respect to the fore-and-aft direction Ds and the vehicle width direction Dw.

[0084] (Third steering step) 19, in the third steering step S25, the first steering unit 53 steers the two first wheels 31 in the first switching end orientation A3 so that the two first wheels 31 form a V-shape that opens toward the inside of the vehicle 2, and causes the drive axes O1 of the three wheels 30 to intersect at a single intersection point Pr located on the inside of the vehicle 2. That is, in this case, in the first switching end orientation A3, the drive axes O1 of the two first wheels 31 intersect with the drive axis O1 of the second wheel 32 at a single intersection point Pr. Through the above steps, the steering mode is switched from the straight-line mode to the rotation mode.

[0085] The vehicle 2 whose steering mode has been switched in the above-described procedure is automatically driven by the control device 50.

[0086] (Action and effect) In this embodiment, the same effects as those of the above-described embodiment can be achieved with respect to the configurations common to the above-described embodiment. In addition, the following effects can be achieved according to this embodiment.

[0087] In this embodiment, the control device 50 includes a first steering unit 53 and a second steering unit 54. The first steering unit 53 steers two of the three wheels 30, namely, first wheels 31, from a first switching start orientation A1 to a first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 as viewed in the vertical direction Dv. After the intersection point P1 is formed, the second steering unit 54 steers the remaining one of the three wheels 30, namely, a second wheel 32, from a second switching start orientation B1 to a second switching end orientation B2, so that the drive axis O1 of the second wheel 32 does not pass through the intersection point P1 as viewed in the vertical direction Dv. After starting to steer the second wheel 32, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to a first switching end orientation A3.

[0088] According to this configuration, the control device 50 can switch the steering mode of the vehicle 2 without causing the drive axes O1 of the three wheels 30 to intersect at a single intersection point. Therefore, the control device 50 can suppress yaw angle deviation when switching the steering mode.

[0089] In this embodiment, when steering the two first wheels 31 from the first switching start orientation A1 to the first intermediate orientation A2, the first steering unit 53 forms the intersection point P1 at a position where the drive axis O1 of the second wheel 32 to be steered later does not pass through the intersection point P1. After the second wheel 32 is steered to the second switching end orientation B2, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3.

[0090] This allows the control device 50 to prevent the drive axes O1 of the three wheels 30 from intersecting at one intersection point without performing any complicated procedures.

[0091] (Modification of the second embodiment) A modification of the second embodiment will be described below with reference to FIGS.

[0092] (First steering section) In this modified example, when the second wheels 32 are steered from the second switching start direction B1 to the second switching end direction B2, the first steering unit 53 steers the two first wheels 31 so that the intersection point P1 moves away from the drive axis O1 of the second wheels 32.

[0093] (Control method procedure) The procedure of the control method for switching the steering mode of the vehicle 2 will be described below with reference to the flow shown in Fig. 20. Here, the control method for the vehicle 2 will be described using as an example a case where the steering mode of the vehicle 2 is switched from the straight-ahead mode to the lateral movement mode. As shown in FIG. 20, the control method according to the modified example of the present disclosure includes a switching start signal acquisition step S21A, a rotation suppression release step S22A, a first steering step S23A, a second steering step S24A, a switching end signal acquisition step S25A, and a rotation suppression operation step S26A. The steps from the switching start signal acquisition step S21A to the rotation suppression release step S22A are performed in the same procedure as in the second embodiment.

[0094] In this modification, the three wheels 30 are steered independently and simultaneously. The steering angles of these three wheels 30 are controlled as shown in the graph in FIG. 21. The steering angles are set based on the orientation of each wheel 30 when the vehicle body 10 is in the straight-ahead mode. Hereinafter, a counterclockwise steering angle is defined as positive, and a clockwise steering angle is defined as negative. The horizontal axis of FIG. 21 indicates elapsed time [s], and the vertical axis of FIG. 21 indicates the steering angle [deg] of each wheel 30. In FIG. 21, the solid line indicates the change over time in the steering angle of the second wheel 32, the dashed line indicates the change over time in the steering angle of the first left wheel 31L, and the dashed line indicates the change over time in the steering angle of the first right wheel 31R. In FIG. 22, and in FIGS. 22 to 24, the wheels 30 and the drive axis O1 are shown at each time in FIG. 21. 22 to 24, the vehicle body 10 is omitted. In Fig. 22 to 24, the vertical axis indicates the position (Y [m]) in the vehicle width direction Dw when the vehicle center line C is set to 0, and the horizontal axis indicates the position (X [m]) in the front-rear direction Ds when the steering axis O2 of the driven wheel 30b is set to 0.

[0095] (First steering step) After the rotation suppression release step S22A, a first steering step S23A is started. In the first steering step S23A, as shown in Fig. 22, the first steering unit 53 first steers two of the three wheels 30, the first wheels 31, from the first switching start orientation A1 to the first intermediate orientation A2, so that the drive axes O1 of the two first wheels 31 intersect at one intersection point P1 as viewed in the up-down direction Dv. Of the first wheels 31, the left first wheel 31L is steered counterclockwise, and the right first wheel 31R is steered clockwise.

[0096] (Second steering step) The formation of the intersection point P1 triggers the execution of a second steering step S24A, and steering of the second wheel 32 begins. While the second wheel 32 is being steered in the second step S24A, the first steering step S23A is executed. More specifically, after the intersection point P1 is formed, the second steering unit 54 steers the second wheel 32, the remaining one of the three wheels 30, from the second switching start orientation B1 to the second switching end orientation B2 so that the drive axis O1 of the second wheel 32 does not pass through the intersection point P1 when viewed in the up-down direction Dv. The second wheel 32 is steered counterclockwise.

[0097] After the steering of the second wheels 32 starts as described above, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3. In this modified example, in the second steering step S24A, not only the second wheel 32 but also the two first wheels 31 are steered. At this time, when the second wheels 32 are steered from the second switching start orientation B1 to the second switching end orientation B2, the first steering unit 53 steers the two first wheels 31 so that the intersection point P1 moves away from the drive axis O1 of the second wheels 32. As a result, as shown in FIGS. 23 and 24, the three intersection points P1, P2, and P3 of each drive axis O1 always move apart. Thereafter, the steering of the two first wheels 31 is completed first, followed by the steering of the second wheels 32. That is, the first steering step S23A is completed first, followed by the second step S24A. In this manner, the first wheel 31 is steered from the first switching start direction A1 to the first switching end direction A3, and the second wheel 32 is steered from the second switching start direction B1 to the second switching end direction B2, without the three drive axes O1 intersecting at a single intersection. In this manner, the steering mode is switched to the lateral movement mode, as shown in FIG. 17 of the second embodiment. Thereafter, the steps from the switching end signal acquisition step S25A to the rotation suppression operation step S26A are performed in the same manner as in the second embodiment. Through the above steps, the control mode is switched from the straight-line mode to the lateral movement mode. This steering mode switching control can also be applied to switching from the straight ahead mode to the turn-on-the-spot mode, as in the above-described embodiment.

[0098] (Action and effect) In this modified example, the same effects as those of the above-described embodiment can be achieved with respect to the configurations common to the above-described embodiment. In addition, the present embodiment can achieve the following effects.

[0099] In this modified example, when the second wheels 32 are steered from the second switching start direction B1 to the second switching end direction B2, the first steering unit 53 steers the two first wheels 31 so that the intersection point P1 moves away from the drive axis O1 of the second wheels 32.

[0100] This allows the three wheels 30 to be steered simultaneously while preventing the drive axes O1 of the three wheels 30 from intersecting at a single intersection point.

[0101] (Hardware configuration) The control devices 40 and 50 of the above embodiments are implemented in a computer 1100 shown in Fig. 25. Fig. 25 is a schematic block diagram showing the configuration of the computer 1100 according to each embodiment. The computer 1100 includes a processor 1110, a main memory 1120, a storage 1130, and an interface 1140.

[0102] The operations of the above-mentioned functional units of the control devices 40 and 50 are stored in the form of a program in the storage 1130. The processor 1110 reads the program from the storage 1130, loads it into the main memory 1120, and executes the above-mentioned processing in accordance with the program. The processor 1110 also allocates a storage area in the main memory 1120 in accordance with the program.

[0103] The program may be for realizing some of the functions to be performed by the computer 1100. For example, the program may be combined with other programs already stored in the storage 1130 or other programs implemented in other devices to perform the functions. Furthermore, the computer 1100 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include a PAL (Programmable Array Logic), a GAL (Generic Array Logic), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array). In this case, some or all of the functions to be performed by the processor 1110 may be realized by the integrated circuit.

[0104] Examples of storage 1130 include a magnetic disk, a magneto-optical disk, and a semiconductor memory. Storage 1130 may be an internal medium directly connected to the bus of computer 1100, or an external medium connected to computer 1100 via interface 1140 or a communication line. Furthermore, when this program is distributed to computer 1100 via a communication line, computer 1100 that receives the program may load the program into main memory 1120 and execute the above-mentioned processing. Storage 1130 may also be a non-transitory tangible storage medium.

[0105] The program may also be a program for realizing some of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with other programs already stored in storage 1130.

[0106] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0107] In the above embodiment, the case where the steering mode of the vehicle 2 is switched from the normal steering mode to the special steering mode has been described. However, the steering mode of the vehicle 2 may also be switched from the special steering mode to the normal steering mode. Furthermore, the steering mode of the vehicle 2 may also be switched from the normal steering mode to a different normal steering mode, or from the special steering mode to a different special steering mode. Furthermore, the case where the steering mode is switched from the straight-ahead mode to the lateral movement mode or the on-the-spot rotation mode has been described. However, this is not limiting. For example, the steering mode may be switched from the turning mode to the lateral movement mode or the on-the-spot rotation mode. The first switching start orientation A1, first intermediate orientation A2, and first switching end orientation A3 of the first wheel 31 can be changed as appropriate. Furthermore, the second switching start orientation B1 and second switching end orientation B2 of the second wheel 32 can be changed as appropriate. For example, the first wheel 31 steered in the first switching end orientation A3 and the second wheel 32 steered in the second switching end orientation B2 may be arranged to tilt at the same tilt angle with respect to the longitudinal direction Ds and the vehicle width direction Dw. In this case, the steering mode becomes a tilt straight-ahead mode in which the vehicle moves in a straight line in a direction tilting in one direction with respect to the longitudinal direction Ds and the vehicle width direction Dw. This tilt straight-ahead mode may be one type of normal steering mode or one type of special steering mode.

[0108] In the above embodiment, the two driven wheels 30b are the first wheels 31 and the one driving wheel 30a is the second wheel 32, but this is not limited to this. Which of the three wheels 30 is the first wheel 31 and which is the second wheel 32 can be changed as appropriate. One of the driven wheels 30b and the driving wheel 30a may be the first wheel 31, and the remaining other driven wheel 30b may be the second wheel 32.

[0109] In the above embodiment, the case where the number of wheels 30 is three has been described, but this is not limited thereto. Four or more wheels 30 may be provided. For example, one training wheel may be provided on the body 10, and the vehicle 2 may be provided with a total of four wheels 30, including a drive wheel 30a, two driven wheels 30b, and the training wheel. In the case where four or more wheels 30 are provided, the steering mode is switched for any three wheels 30 in the above-described procedure.

[0110] In the above embodiment, the control devices 40, 50 are provided separately from the vehicle 2, but this is not limiting. The control devices 40, 50 may be provided integrally with the vehicle 2.

[0111] In the above embodiment, the vehicle 2 is an autonomous forklift truck, but the present disclosure is not limited to this. The vehicle 2 may be, for example, a manned forklift truck or an electric trolley. However, when the vehicle 2 is an unmanned autonomous forklift truck that requires highly accurate operation and does not allow for fine adjustments by the operator, the control devices 40 and 50 of the present disclosure that suppress yaw angle deviation when switching operation modes while the vehicle is stopped function particularly effectively.

[0112] <Additional Notes> The control devices 40 and 50, the control system 1, the control method and the program described in each embodiment can be understood, for example, as follows.

[0113] (1) A control device 40 according to a first aspect is a control device 40 for a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, which are rotatable around a drive axis O1 extending in a horizontal direction Dh and steerable around a steering axis O2 extending in a vertical direction Dv, and by steering two first wheels 31 of the three wheels 30 from a first switching start orientation A1 to a first intermediate orientation A2, the driving directions of the two first wheels 31 are changed as viewed in the vertical direction Dv. The steering system includes a first steering unit 43 that intersects the driving axis O1 at a single intersection P1 located outside the vehicle body 10, and a second steering unit 44 that steers the remaining second wheel 32 of the three wheels 30 from a second switching start direction B1 to a second switching end direction B2 after the intersection P1 is formed, and after the second wheel 32 is steered to the second switching end direction B2, the first steering unit 43 steers the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3.

[0114] When switching the steering mode of the vehicle 2 (for example, from straight-ahead mode to sideways movement mode, or from straight-ahead mode to on-the-spot rotation mode), if the drive axes O1 of the three wheels 30 intersect at a single intersection when viewed in the vertical direction Dv, the vehicle 2 will be more likely to rotate around the vertical axis passing through that intersection, and even a small external force will cause a deviation in the yaw angle. In contrast, in this embodiment, the control device 40 first steers the two first wheels 31 in the first switching start orientation A1 to the first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection P1 located outside the vehicle body 10 as viewed in the vertical direction Dv. Even if the control device 40 then steers the second wheel 32 so that the drive axis O1 of the second wheel 32 passes through the intersection P1 and the drive axes O1 of the three wheels 30 intersect at the single intersection P1, the distance (arm length) between the intersection P1, which serves as the center of rotation, and the center of gravity of the vehicle 2 becomes longer, making it difficult for the vehicle 2 to rotate around the vertical axis. Therefore, the control device 40 can suppress yaw angle deviation when switching the steering mode.

[0115] (2) A control device 50 according to a second aspect is a control device 50 for a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, which are rotatable around a drive axis O1 extending in a horizontal direction Dh and steerable around a steering axis O2 extending in a vertical direction Dv. Two first wheels 31 of the three wheels 30 are steered from a first switching start orientation A1 to a first intermediate orientation A2, so that the drive axes O1 of the two first wheels 31 are aligned in a 1-axis direction as viewed in the vertical direction Dv. The steering system is equipped with a first steering unit 53 that causes the two first wheels 31 to intersect at an intersection P1, and a second steering unit 54 that, after the intersection P1 is formed, steers the remaining second wheel 32 of the three wheels 30 from the second switching start orientation B1 to the second switching end orientation B2 so that the drive axis O1 of the second wheel 32 does not pass through the intersection P1 when viewed in the up-down direction Dv, and after steering of the second wheel 32 begins, the first steering unit 53 steers the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3.

[0116] According to this configuration, the control device 50 can switch the steering mode of the vehicle 2 without causing the drive axes O1 of the three wheels 30 to intersect at a single intersection point P1. Therefore, the control device 50 can suppress yaw angle deviation when switching the steering mode.

[0117] (3) A control device 50 according to a third aspect is the control device 50 of (2), wherein, when steering the two first wheels 31 from the first switching start direction A1 to the first intermediate direction A2, the first steering unit 53 forms the intersection point P1 at a position where the drive axis O1 of the second wheel 32 to be steered later does not pass through the intersection point P1, and after the second wheel 32 is steered to the second switching end direction B2, the first steering unit 53 may steer the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3.

[0118] This allows the control device 50 to prevent the drive axes O1 of the three wheels 30 from intersecting at one intersection point without performing any complicated procedures.

[0119] (4) The control device 50 according to the fourth aspect is the control device 50 of (2), and when the second wheel 32 is steered from the second switching start direction B1 to the second switching end direction B2, the first steering unit 53 may steer the two first wheels 31 so that the intersection point P1 moves away from the drive axis O1 of the second wheel 32.

[0120] This allows the three wheels 30 to be steered simultaneously while preventing the drive axes O1 of the three wheels 30 from intersecting at a single intersection point.

[0121] (5) A control device 40, 50 according to a fifth aspect is a control device 40, 50 of any one of (1) to (4), wherein the vehicle 2 comprises a traction motor 3 that drives the drive wheel 30a of the three wheels 30, and a rotation suppression mechanism 4 that suppresses the rotation of the drive wheel 30a, and the rotation suppression mechanism 4 comprises a rotation suppression operating unit 42, 52 that releases the rotation suppression of the drive wheel 30a before steering of the drive wheel 30a begins, and the rotation suppression operating unit 42, 52 may maintain a state in which the rotation suppression of the drive wheel 30a by the rotation suppression mechanism 4 is released until steering of the drive wheel 30a is completed. Examples of the rotation suppression mechanism 4 include a brake mechanism that applies a brake to the drive wheels 30a, and a counter-driving force mechanism that applies a counter-driving force to the drive wheels 30a.

[0122] Because the tire width of the drive wheel 30a is wide, it is considered that the point of application Pa of the ground load is not on the steering axis O2 in many cases. In this way, if the drive wheel 30a is steered while the rotation suppression mechanism 4 suppresses the rotation of the drive wheel 30a in a state where the point of application Pa of the ground load is eccentric with respect to the steering axis O2, the point of application Pa of the ground load of the drive wheel 30a will not move, and a moment will be generated that rotates the vehicle body 10 in the yaw angle direction. This makes it easier for the yaw angle of the vehicle body 10 to shift. In contrast, in this embodiment, while the control devices 40, 50 are steering the wheels 30, the rotation restriction on the drive wheels 30a is released. As a result, when the drive wheels 30a are steered, the application point Pa of the ground load on the drive wheels 30a is allowed to rotate around the steering axis O2. This suppresses the moment that rotates the vehicle body 10 in the yaw angle direction. This further suppresses yaw angle deviation of the vehicle body 10.

[0123] (6) The control device 40, 50 according to the sixth aspect is any one of the control devices 40, 50 of (1) to (5), and is equipped with an automatic steering unit 45, 55 that steers the vehicle 2 by rotating the wheels 30 around the drive axis O1.

[0124] According to this aspect, the control devices 40 and 50 enable automatic steering of the vehicle 2 without requiring a driver to operate the vehicle 2. Incidentally, when a driver is on board the vehicle 2 and the vehicle 2 is manually driven by the driver, even if a yaw angle deviation occurs in the vehicle 2 when switching the driving mode of the vehicle 2, the driver can make fine adjustments to eliminate the yaw angle deviation. For this reason, when the vehicle 2 is manually driven by a driver, such as a manned forklift, control to prevent a yaw angle deviation in the vehicle 2 is not given priority. On the other hand, when the vehicle 2 is automatically steered as in this embodiment, the yaw angle deviation of the vehicle 2 cannot be eliminated by fine adjustments by the driver. However, the control devices 40, 50 of this embodiment have the configuration of at least the first or second embodiment, and therefore can suppress the occurrence of yaw angle deviation itself. Furthermore, when the control devices 40, 50 have the configuration of the fifth embodiment, yaw angle deviation hardly occurs. Therefore, the control devices 40, 50 can automatically steer the vehicle 2 without eliminating the yaw angle deviation of the vehicle 2 after switching the steering mode.

[0125] (7) A control system 1 according to a seventh aspect includes the control device 40, 50 according to any one of (1) to (6) and the vehicle 2.

[0126] (8) A control method according to an eighth aspect is a control method for a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, which are rotatable around a drive axis O1 extending in a horizontal direction Dh and steerable around a steering axis O2 extending in a vertical direction Dv, wherein two first wheels 31 of the three wheels 30 are steered from a first switching start orientation A1 to a first intermediate orientation A2, so that the drive axes O1 of the two first wheels 31 are aligned forward as viewed in the vertical direction Dv. The method includes a first steering step S13 of intersecting the wheels 31 at a single intersection P1 located outside the vehicle body 10, a second steering step S14 of steering the remaining second wheel 32 of the three wheels 30 from the second switching start direction B1 to the second switching end direction B2 after the intersection P1 is formed, and a third steering step S15 of steering the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3 after the second wheel 32 is steered to the second switching end direction B2.

[0127] (9) A control method according to a ninth aspect is a control method for a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, rotatable around a drive axis O1 extending in a horizontal direction Dh, and steerable around a steering axis O2 extending in a vertical direction Dv, the control method including a first steering step S in which two first wheels 31 of the three wheels 30 are steered from a first switching start orientation A1 to a first intermediate orientation A2 so that the drive axes O1 of the two first wheels 31 intersect at one intersection point P1 as viewed in the vertical direction Dv. 23, S23A, a second steering step S24, S24A of steering the remaining second wheel 32 of the three wheels 30 from the second switching start direction B1 to the second switching end direction B2 after the intersection point P1 is formed so that the drive axis O1 of the second wheel 32 does not pass through the intersection point P1 when viewed in the vertical direction Dv, and a step (third steering step S25, first steering step S23A) of steering the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3 after steering of the second wheel 32 starts.

[0128] (10) A program according to a tenth aspect is a program for controlling a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, which are rotatable around a drive axis O1 extending in a horizontal direction Dh and steerable around a steering axis O2 extending in a vertical direction Dv, wherein two first wheels 31 of the three wheels 30 are steered from a first switching start orientation A1 to a first intermediate orientation A2, so that the drive axes O1 of the two first wheels 31 are aligned in the vertical direction Dv. The computer executes a first steering step S13 of intersecting the wheels at a single intersection P1 located outside the vehicle body 10, a second steering step S14 of steering the remaining second wheel 32 of the three wheels 30 from the second switching start direction B1 to the second switching end direction B2 after the intersection P1 is formed, and a third steering step S15 of steering the two first wheels 31 from the first intermediate direction A2 to the first switching end direction A3 after the second wheel 32 is steered to the second switching end direction B2.

[0129] (11) A program according to an eleventh aspect is a program for controlling a vehicle 2 having a vehicle body 10 and three wheels 30 provided on the vehicle body 10, rotatable around a drive axis O1 extending in a horizontal direction Dh and steerable around a steering axis O2 extending in a vertical direction Dv, the program including a first steering step S2 in which two first wheels 31 of the three wheels 30 are steered from a first switching start orientation A1 to a first intermediate orientation A2, thereby causing the drive axes O1 of the two first wheels 31 to intersect at a single intersection point P1 as viewed in the vertical direction Dv. 3, S23A, and after the intersection P1 is formed, the computer executes a second steering step S24, S24A of steering the remaining second wheel 32 of the three wheels 30 from the second switching start orientation B1 to the second switching end orientation B2 so that the drive axis O1 of the second wheel 32 does not pass through the intersection P1 when viewed in the vertical direction Dv, and a step (third steering step S25, first steering step S23A) of steering the two first wheels 31 from the first intermediate orientation A2 to the first switching end orientation A3 after steering of the second wheel 32 begins. [Explanation of symbols]

[0130] 1. Control System 2 vehicles 3. Travel motor 4 Rotation suppression mechanism 5 Steering gear 6 Vehicle control device 10. Body 11 Body 12 Straddle Leg 20 Loading mechanism 21 Mast 22 Lift bracket 23 Fork 30 wheels 30a drive wheel 30b Driven wheel 31 1st wheel 31L 1st left wheel 31R Right side 1st wheel 32 2nd wheel 40 Control device 41 Acquisition Department 42 Rotation suppression operation unit 43 First Steering Section 44 Second Steering Section 45 Autopilot Unit 50 Control device 51 Acquisition Department 52 Rotation suppression operation unit 53 First Steering Section 54 Second Steering Section 55 Autopilot A1 First switching start direction A2 1st Intermediate A3 1st switch end direction B1 Second switching start direction B2 Second switching end direction C Vehicle centerline Dv vertical direction Dh horizontal direction Ds Anteroposterior direction Dw Vehicle width direction O1 drive axis O2 steering axis P1 intersection P2 intersection P3 intersection Pr intersection S11 Switching start signal acquisition step S12 Rotation suppression release step S13 First steering step S14 Second steering step S15 Third steering step S16 Switching end signal acquisition step S17 Rotation suppression operation step S21 Switching start signal acquisition step S22 Rotation suppression release step S23 First steering step S24 Second steering step S25 3rd steering step S26 Switching end signal acquisition step S27 Rotation suppression operation step S21A Switching start signal acquisition step S22A Rotation suppression release step S23A 1st steering step S24A 2nd steering step S25A Switching end signal acquisition step S26A Rotation suppression operation step

Claims

1. A control device for a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about drive axes extending in a horizontal direction and steerable about steering axes extending in a vertical direction, the control device comprising: a first steering unit that steers two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at a single intersection point located outside the vehicle body as viewed in the up-down direction; a second steering unit that steers the remaining second wheel of the three wheels from the second switching start orientation to the second switching end orientation after the intersection is formed; Equipped with After the second wheels are steered in the second switching end orientation, the first steering unit steers the two first wheels from the first intermediate orientation to the first switching end orientation. Control device.

2. A control device for a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about drive axes extending in a horizontal direction and steerable about steering axes extending in a vertical direction, the control device comprising: a first steering unit that steers two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation, thereby causing the drive axes of the two first wheels to intersect at one intersection point when viewed in the up-down direction; a second steering unit that steers the remaining second wheel of the three wheels from the second switching start orientation to the second switching end orientation after the intersection is formed so that the drive axis of the second wheel does not pass through the intersection when viewed in the up-down direction; Equipped with After the steering of the second wheels is started, the first steering unit steers the two first wheels from the first intermediate orientation to a first switching end orientation. Control device.

3. When steering the two first wheels from the first switching start orientation to the first intermediate orientation, the first steering unit forms the intersection at a position where the drive axis of the second wheel to be steered later does not pass through the intersection, After the second wheels are steered in the second switching end orientation, the first steering unit steers the two first wheels from the first intermediate orientation to the first switching end orientation. The control device according to claim 2 .

4. When the second wheels are steered from the second switching start orientation to the second switching end orientation, the first steering unit steers the two first wheels so that the intersection point is away from the drive axis of the second wheels. The control device according to claim 2 .

5. The vehicle is a traction motor that drives a drive wheel among the three wheels; a rotation suppression mechanism that suppresses rotation of the drive wheels; Equipped with a rotation suppression operation unit that releases the rotation suppression of the drive wheels before the steering of the drive wheels is started, The rotation suppression operation unit maintains a state in which the rotation suppression of the drive wheels by the rotation suppression mechanism is released until the steering of the drive wheels is completed. The control device according to any one of claims 1 to 4.

6. an automatic steering unit that steers the vehicle by rotating the wheels about the drive axis; The control device according to claim 5 .

7. The control device according to any one of claims 1 to 4; The vehicle; A control system comprising:

8. A method for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about drive axes extending in a horizontal direction and steerable about steering axes extending in a vertical direction, the method comprising: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation so that the drive axes of the two first wheels intersect at a single intersection point located outside the vehicle body as viewed in the up-down direction; a second steering step of steering the remaining second wheel of the three wheels from the second switching start direction to the second switching end direction after the intersection point is formed; a third steering step of steering the two first wheels from the first intermediate direction to the first switching end direction after the second wheels are steered in the second switching end direction; A control method comprising:

9. A method for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about drive axes extending in a horizontal direction and steerable about steering axes extending in a vertical direction, the method comprising: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation so that the drive axes of the two first wheels intersect at one intersection point when viewed in the up-down direction; a second steering step of steering the remaining second wheel of the three wheels from the second switching start orientation to the second switching end orientation after the intersection is formed so that the drive axis of the second wheel does not pass through the intersection when viewed in the up-down direction; After starting to steer the second wheels, steering the two first wheels from the first intermediate direction to a first switching end direction; A control method comprising:

10. A program for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about a drive axis extending in a horizontal direction and steerable about a steering axis extending in a vertical direction, the program comprising: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation so that the drive axes of the two first wheels intersect at a single intersection point located outside the vehicle body as viewed in the up-down direction; a second steering step of steering the remaining second wheel of the three wheels from the second switching start direction to the second switching end direction after the intersection point is formed; a third steering step of steering the two first wheels from the first intermediate direction to the first switching end direction after the second wheels are steered in the second switching end direction; A program that causes a computer to execute the following.

11. A program for controlling a vehicle having a vehicle body and three wheels provided on the vehicle body, the wheels being rotatable about a drive axis extending in a horizontal direction and steerable about a steering axis extending in a vertical direction, the program comprising: a first steering step of steering two first wheels of the three wheels from a first switching start orientation to a first intermediate orientation so that the drive axes of the two first wheels intersect at one intersection point when viewed in the up-down direction; a second steering step of steering the remaining second wheel of the three wheels from the second switching start orientation to the second switching end orientation after the intersection is formed so that the drive axis of the second wheel does not pass through the intersection when viewed in the up-down direction; After starting to steer the second wheels, steering the two first wheels from the first intermediate direction to a first switching end direction; A program that causes a computer to execute the following.

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