Precise docking control method and vehicle system

Abstract

To provide a precise docking control method and a vehicle system for drawing a 4-wheel steering vehicle sideways to stop.SOLUTION: A precise docking control method for drawing a vehicle (2) including at least a 4-wheel steering vehicle whose rear wheels are steered in an opposite phase to a platform (15) sideways to stop, executes preliminary control for setting a virtual platform (159) virtually extending along a stopping direction being a direction of the vehicle (2) when the vehicle (2) is drawn to the platform (15) sideways to stop to a position that is the front side of the platform (15), and drawing the vehicle (2) to the virtual platform (159) sideways before control for drawing the vehicle (2) to the platform (15) sideways to stop.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a straightening control method and a vehicle system for laterally stopping a vehicle including a four-wheel steering vehicle in which the rear wheels are steered in the reverse phase.

Background Art

[0002] Conventionally, for example, for the purpose of transporting parts, products, etc. within a facility such as a factory, a four-wheel steering vehicle in which the rear wheels are steered in the reverse phase with respect to the front wheels, which are the steering wheels, may be used. Four-wheel steering vehicles are suitable for use within facilities such as factories because they are effective in making tight turns (see Patent Document 1 below). Four-wheel steering vehicles include, in addition to vehicles having drive wheels and capable of self-propulsion, carts towed by towing vehicles, etc.

[0003] However, a four-wheel steering vehicle in which the rear wheels are controlled in the reverse phase has a tendency for the rear wheels to swing outwards during cornering. For example, during so-called straightening control in which the vehicle is laterally stopped at a predetermined stop position, the swing-out of the rear wheels may become a problem.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0007] One aspect of the present invention is a vehicle system for bringing a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, alongside a platform and stopping it, A first circuit sets a virtual platform that virtually extends along the stopping direction, which is the direction in which the vehicle is facing when the vehicle is parked alongside the platform, at a position that is on the front side of the platform in both the stopping direction and the lateral direction perpendicular to the stopping direction. A second circuit that performs preliminary control to move the vehicle closer to the virtual platform, Includes a third circuit that performs control for bringing the vehicle alongside the platform and stopping it, The third circuit is located in a vehicle system that, after the preliminary control performed by the second circuit, executes control to bring the vehicle alongside the platform and stop it.

[0008] The present invention relates to a precise docking control method and vehicle system for stopping a vehicle, including at least a four-wheel steering vehicle, alongside a platform. In this precise docking control method and vehicle system, a virtual platform is virtually set up in front of the platform on which the vehicle is to be stopped. In this precise docking control method, the vehicle is brought closer to this virtual platform before it is to be stopped alongside the platform.

[0009] According to the present invention, by moving a vehicle, including at least a four-wheel steering vehicle, closer to a virtual platform before stopping it alongside the platform, the vehicle's entry angle when stopping alongside the platform can be reduced. Reducing the vehicle's entry angle reduces the amount of steering, thereby reducing the amount of outward swing of the rear wheels, which are steered in the opposite phase.

[0010] Thus, the pre-parking control method and vehicle system of the present invention are excellent control methods or systems that can suppress the amount of outward swing of the rear wheels when a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, is parked alongside a platform and stopped. [Brief explanation of the drawing]

[0011] [Figure 1] A diagram illustrating the vehicle system. [Figure 2] Vehicle diagram. [Figure 3] Diagram illustrating the four-wheel steering mechanism of a trolley. [Figure 4] A system diagram showing the system configuration of the towing vehicle. [Figure 5] Diagram illustrating a magnetic sensor array. [Figure 6] A flowchart illustrating the flow of vehicle control. [Figure 7] Diagram illustrating the pre-control system. [Figure 8] A diagram illustrating the control system for precisely positioning the platform. [Figure 9] An explanatory diagram of other installation methods for magnetic markers. [Modes for carrying out the invention]

[0012] The four-wheel steering vehicle in the present invention may be a vehicle having drive wheels and capable of self-running, or may be a dolly that does not have drive wheels and is towed by another vehicle. The vehicle may be a vehicle combining a towing vehicle having drive wheels and a dolly. In the case of the combination of the towing vehicle and the dolly, either the towing vehicle or the dolly may be a four-wheel steering vehicle. The towing vehicle may be a four-wheel steering vehicle or a vehicle in which only the front wheels or the rear wheels are steered. The number of dollies towed by the towing vehicle may be only one or two or more. When the number of dollies is two or more, any one of the dollies may be a four-wheel steering vehicle.

[0013] The correct parking control method of the present invention may be premised on, for example, the travel control of a vehicle by autonomous navigation, or may be premised on the travel control of a vehicle using, for example, a magnetic marker or a guide tape, or may be premised on the control of running a vehicle using the absolute position measured by GNSS (Global Navigation Satellite System) using satellite radio waves, or may be premised on the control of running a vehicle using the position measured by an indoor positioning system using a radio beacon or a wireless tag.

[0014] Embodiments of the present invention will be specifically described using the following examples. (Example 1) This example relates to a vehicle system 1 that executes correct parking control for horizontally parking and stopping vehicle 2 at a predetermined stop position. This content will be described with reference to FIGS. 1 to 9.

[0015] The vehicle system 1 in this example is a system in which the vehicle 2 moves along the paths 11 and 13 provided within a facility such as a factory, as shown in FIG. 1. For example, in a facility such as a factory, there are platforms 15 for vehicles carrying parts to be supplied to equipment to park horizontally and stop, platforms 15 for vehicles carrying processed parts to park horizontally and stop, and so on. For example, in facilities such as hospitals and nursing homes, there are platforms for loading cooked meals onto vehicles, and so on.

[0016] As illustrated in FIG. 1 for example, in the vehicle system 1, in addition to the main path 11 for moving within the facility, a branch path 13 branching from the main path is provided. As one of the branch paths 13, a parking path 130 for parking the vehicle 2 horizontally on the above-mentioned platform 15 is provided. In the vehicle system 1, map data in which the absolute positions and the like of each point on the paths 11 and 13 are specified is used.

[0017] Magnetic markers 10 are arranged at intervals on the main path 11 and the branch path 13. For example, on the main path 11, magnetic markers 10 are arranged at intervals of 2 m along the traveling path of the vehicle 2. Also, for example, on the parking path 130 which is one of the branch paths 13, magnetic markers 10 are arranged at intervals of 0.5 m, which is narrower than the main path 11, so as to ensure the positional accuracy of the vehicle 2 in the traveling direction.

[0018] The parking path 130 is provided individually for the platform 15 on which the vehicle 2 is parked horizontally and stopped. The parking path 130 includes a straight section 131 including a stop position (an example of a predetermined stop position) 135 for parking the vehicle 2 horizontally on the platform 15, a diversion section 133 branching from the main path 11 and connecting to the straight section, and a merging section (not shown) for merging into the main path 11 after passing through the straight section 131.

[0019] The side access routes 130 for each platform 15 have the same specifications. The distance of the diversion section 133, the distance of the straight section 131, the distance of the merging section (not shown), and the distance from the starting point of the straight section 131 to the stopping position 135 are all common to each platform 15. Since the distances of each section are common, the number of magnetic markers 10 installed in the diversion section 133 and the number of magnetic markers 10 installed from the starting point of the straight section 131 to the stopping position 135 are also common to each platform 15. On the vehicle 2 side, for example, by counting the number of magnetic markers 10 placed every 0.5m, it is possible to determine the distance from entering the side access route 130 to entering the straight section 131, and the remaining distance from entering the straight section 131 to the stopping position 135.

[0020] In this example, the straight section 131 has a length of 9m, and the distance from the starting point of the straight section 131 to the stopping position 135 is 7m. The lateral distance between the main path 11 and the straight section 131, which are parallel to each other, is set to 1m. In the straight section 131, the magnetic markers 10 are positioned so that when the amount of lateral displacement (lateral deviation) of the vehicle 2 relative to the magnetic markers 10 is controlled to zero, the vehicle 2 can be positioned alongside the platform 15 with a gap of 10cm. The side-to-side path 130 is a path for positioning the vehicle 2 moving along the main path 11 90cm to the platform 15.

[0021] Vehicle 2 (Figure 2) consists of an autonomously driven towing vehicle 21 and a four-wheeled bogie 23 towed by the towing vehicle 21. The towing vehicle 21 is 2m long and 1m wide. The bogie 23 is 2m long and 1m wide. In this example, vehicle 2 has only one bogie 23 connected, but it may also be a vehicle with multiple bogies 23 connected.

[0022] The towing vehicle 21 is a three-wheeled vehicle equipped with a single front wheel 211 that serves as a steering wheel and two rear wheels 212 that serve as drive wheels. The rear wheels 212 are fixed wheels with a fixed direction of rotation. A rod-shaped magnetic sensor array 3 is mounted on the front of the towing vehicle 21 so as to follow the vehicle width direction (lateral direction). A towing hook 219 for towing the bogie 23 is provided at the rear end of the towing vehicle 21.

[0023] The bogie 23 is a four-wheeled vehicle with two front wheels 231 and two rear wheels 232. All the wheels on the bogie 23 are driven wheels that do not generate any driving force. The front wheels 231 are rotatably supported by front wheel holders 231H (Figure 3). The rear wheels 232 are rotatably supported by rear wheel holders 232H (Figure 3). The front wheel holders 231H and rear wheel holders 232H are suspended from the vehicle body in a rotatable state. The front wheels 231 or the rear wheels 232 are steered in accordance with the rotation of the front wheel holders 231H and rear wheel holders 232H. The bogie 23 is a 4WS bogie in which the rear wheels 232 are steered in opposite phase to the front wheels 231, and is an example of a four-wheel steering vehicle.

[0024] As shown in Figures 2 and 3, the bogie 23 is equipped with a connecting bar 230 for connecting to the towing vehicle 21, as well as a link mechanism 24 for steering the front wheels 231 and a link mechanism 25 for steering the rear wheels 232. The bogie 23 is configured so that the front wheels 231 and rear wheels 232 are steered according to the direction in which it is towed by the towing vehicle 21. The link mechanisms 24 and 25 are arranged at different heights to avoid interference with each other and with the front wheel holders 231H and rear wheel holders 232H, etc.

[0025] The connecting bar 230 is provided so as to protrude forward from the bogie 23. The tip of the connecting bar 230 is configured to be able to be locked onto the towing hook 219 of the towing vehicle 21. The connecting bar 230 is pivotally supported by a vertical axis 230P so as to be able to rotate in a horizontal plane parallel to the road surface. While being towed by the towing vehicle 21, the connecting bar 230 rotates toward the towing vehicle 21. The rear end of the connecting bar 230 is provided with a locking portion 230A for connecting the ends of two push rods 241 that form a link mechanism 24.

[0026] The linkage mechanism 24 for steering the front wheel 231 includes a push rod 241 connected to the rear end of the connecting bar 230, and a first lever 243 provided integrally with the front wheel holder 231H that rotatably supports the front wheel 231. The first lever 243 extends so as to protrude rearward from the rotation center of the rotatable front wheel holder 231H. The tip of the first lever 243 is configured to connect to the push rod 241. The linkage mechanism 24 is configured such that, in response to the rotational displacement of the connecting bar 230, the push rod 241 pushes or pulls the first lever 243, causing the front wheel holder 231H to rotate and the front wheel 231 to be steered.

[0027] The linkage mechanism 25 for steering the rear wheel 232 includes a second lever 253 integrated with the front wheel holder 231H, a third lever 255 integrated with the rear wheel holder 232H that rotatably supports the rear wheel 232, and a linkage rod 251 connecting the second lever 253 and the third lever 255. The second lever 253 extends outward from the center of rotation of the front wheel holder 231H. The third lever 255 extends inward from the center of rotation of the rotatable rear wheel holder 232H. The tips of the second lever 253 and the third lever 255 are configured to be connectable to the linkage rod 251.

[0028] For example, when the front wheel holder 231H rotates to the right in response to the rightward steering of the front wheel 231, the second lever 253 rotates clockwise. This pushes the link rod 251 backward. The link rod 251 pushed backward causes the third lever 255 of the rear wheel holder 232H to rotate counterclockwise. This causes the rear wheel holder 232H to rotate left, thereby steering the rear wheel 232 to the left. Thus, the link mechanism 25 is configured so that the rear wheel 232 is steered in opposite phase to the steering of the front wheel 231.

[0029] Next, the system configuration of the towing vehicle 21 will be explained with reference to Figure 4. The system of the towing vehicle 21 is centered around the control unit 40. The control unit 40 is connected to a magnetic sensor array 3 for magnetic detection, an IMU (Inertial Measurement Unit) 42 that enables inertial navigation, a motor unit 44 that rotates the rear wheels 212, a wheel speed unit 442 that outputs pulses according to the rotation of the rear wheels 212, a steering unit 46 that steers the front wheels 211 which are the steering wheels, a map database 48, and the like.

[0030] The magnetic sensor array 3 (Figure 5) is a rod-shaped unit in which multiple magnetic sensors Cn are arranged in a straight line, and is mounted along the width direction of the towing vehicle 21 (see Figure 2). In this example, the magnetic sensor array 3 is mounted in front of the front wheels 211. The mounting height of the magnetic sensor array 3 relative to the floor surface on which the vehicle 2 moves is 100 mm.

[0031] The magnetic sensor array 3 (Figure 5) comprises 15 magnetic sensors Cn (where n is an integer from 1 to 15) arranged in a straight line, and a detection processing circuit 32 incorporating a CPU and the like (not shown). In the rod-shaped magnetic sensor array 3, 15 magnetic sensors Cn are arranged at 5 cm intervals along its longitudinal direction. When the magnetic sensor array 3 is attached to the towing vehicle 21 so as to be aligned with the vehicle width direction, the 15 magnetic sensors Cn will be arranged in a straight line along the vehicle width direction (lateral direction). Based on the 15 magnetic sensors Cn arranged in the vehicle width direction, when a magnetic marker 10 is detected, the position of the magnetic marker 10 in the vehicle width direction can be detected. Based on the position of the magnetic marker 10 relative to the 15 magnetic sensors Cn, the amount of lateral displacement (lateral deviation) of the towing vehicle 21 relative to the magnetic marker 10 can be determined.

[0032] For the magnetic sensor Cn, for example, a highly accurate MI (Magnet Impedance) sensor is recommended. An MI sensor is a magnetic sensor that utilizes the known MI effect (Magnet Impedance Effect), in which the impedance of a magnetosensitive material such as an amorphous wire changes sensitively in response to an external magnetic field. Each magnetic sensor Cn constituting the magnetic sensor array 3 has the same magnetic detection direction. The magnetic detection direction by each magnetic sensor Cn may be one of the vertical, lateral (vehicle width direction), or direction of travel, or two of them, or all of them.

[0033] The detection processing circuit 32 (Figure 5) of the magnetic sensor array 3 is an arithmetic circuit that performs marker detection processing to detect the magnetic marker 10. The detection processing circuit 32, although not shown in the figure, is composed of a CPU (central processing unit) that performs various calculations, memory elements such as ROM (read-only memory) and RAM (random access memory), etc. The detection processing circuit 32 outputs the detection signal of the magnetic marker 10 and the amount of lateral displacement of the towing vehicle 21 relative to the magnetic marker 10.

[0034] The IMU42 (Figure 4) is a unit that estimates the relative position and vehicle heading of the towed vehicle 21 using inertial navigation. Although not shown in the figure, the IMU42 is equipped with a two-axis magnetic sensor which is an electronic compass for measuring heading, a two-axis accelerometer for measuring acceleration, a two-axis gyro sensor for measuring angular velocity around the yaw axis, etc. Here, the yaw axis is the vertical axis.

[0035] The IMU42 calculates the displacement by double integration of the measured acceleration and the relative orientation of the towing vehicle 21 by integration of the measured angular velocity. The IMU42 estimates the vehicle orientation at any given moment by adding this relative orientation to the reference orientation (absolute orientation). For example, the absolute orientation when vehicle 2 is parked in a predetermined parking position can be used as the reference orientation. The IMU42 estimates the relative position (displaced position) by accumulating the displacement along the vehicle orientation at any given moment. Each time a new magnetic marker 10 is detected and the vehicle position (absolute position) is determined, the reference position is updated according to that vehicle position and the relative position is reset to zero.

[0036] The map database 48 is a database that stores map data representing the shapes of routes 11 and 13, the location of platform 15, waiting positions, stopping positions, etc. Magnetic markers 10 (see Figure 1) placed along the routes are linked to the map data. For example, by referring to the map data using the number of magnetic markers 10 detected after departing a waiting position whose absolute position on the map data is known, the location of the most recently detected magnetic marker 10 can be identified.

[0037] The control unit 40 is a unit that controls the movement of the towing vehicle 21. The control unit 40 controls the steering angle of the front wheels 211 via the steering unit 46 and controls the rotational angular velocity of the rear wheels 212 via the motor unit 44. The control unit 40 is equipped with an electronic circuit (not shown) that includes a CPU for performing various calculations, memory elements such as ROM and RAM. The control unit 40 stores the contents of work tasks acquired from an external source in the RAM storage area. In the work tasks, the locations on the map data are specified, such as waypoints that the vehicle 2 should pass through, the platform 15 to which it should arrive, and the final destination.

[0038] The control unit 40 has the following circuit functions: (1) Circuit for determining the travel path: Based on the set work task, this circuit determines the path that vehicle 2 should take. (2) Circuit for determining vehicle position: The vehicle position is determined using the marker detection result or the relative position estimated by IMU42. (3) Circuit for setting the target lateral displacement: This circuit sets the target lateral displacement, which is the control target value for the amount of lateral displacement (lateral deviation) of the vehicle 2 relative to the magnetic marker 10. (4) Circuit for calculating control values: This circuit calculates control values ​​such as the target steering angle for the steering angle of the front wheels 211 and the target rotational angular velocity for the rotational angular velocity of the rear wheels 212. (5) Circuit for controlling vehicle 2: The control value of the indicated steering angle is input to the steering unit 46, and the control value of the indicated rotational angular velocity is input to the motor unit 44, thereby controlling the movement of vehicle 2.

[0039] The circuit for setting the target lateral displacement described above functions as a first circuit that sets a virtual platform, which virtually extends along the stopping direction (the orientation of the vehicle 2 when it is parked alongside the platform 15), at a position on the front side of the platform 15 in both the stopping direction and the lateral direction perpendicular to the stopping direction. As will be described in more detail later, an example of the first circuit, the circuit for setting the target lateral displacement, sets the virtual platform by making the target lateral displacement relative to the magnetic marker 10 during vehicle 2 travel control variable.

[0040] The circuit that controls the vehicle 2 has the function of a second circuit that performs preliminary control to move the vehicle 2 closer to the virtual platform, and the function of a third circuit that performs control to move the vehicle 2 alongside the platform 15 and stop it.

[0041] In the vehicle system 1 of this example, configured as described above, the control unit 40 determines the route for moving to waypoints and goal points related to work tasks. The control unit 40 determines the movement route from the current location, such as a waiting position, by mapping the waypoints and goal points onto map data.

[0042] The details of the vehicle 2 driving control performed by the control unit 40 will be explained below with reference to the flowchart in Figure 6, Figures 7 and 8. The flowchart in Figure 6 shows the control flow until the vehicle 2 is properly docked at the platform 15 via the main route 11. When driving control is performed, the control unit 40 uses the vehicle 2's starting point, such as a waiting position, as a reference position to determine the vehicle 2's current location at any given moment.

[0043] As the vehicle 2 moves along the main path 11 (see Figure 7), the control unit 40 sets the target lateral displacement amount relative to the magnetic marker 10 to zero (S101). The control unit 40 identifies the deviation between the measured lateral displacement amount relative to the detected magnetic marker 10 and the target lateral displacement amount (S102), and executes driving control, including steering angle control, to bring this deviation closer to zero (S103). With such driving control, the vehicle 2 can be moved along the arrangement line of the magnetic marker 10 on the main path 11. The control unit 40 repeats the above process until it reaches the branching point to the side path 130 (S104:NO).

[0044] While moving along the main route 11, the control unit 40 determines the vehicle's current location on the map data by counting the number of magnetic markers 10 detected after starting movement from a reference position, such as a waiting position. Furthermore, after detecting any magnetic marker 10 and before detecting a new magnetic marker 10, the control unit 40 estimates the vehicle's current location using inertial navigation with the IMU 42. By determining or estimating the vehicle's current location in this way, the control unit 40 understands its approach to the branching point to the side route 130.

[0045] When the control unit 40 reaches the branching point to the side-to-side path 130 (S104: YES), it sets the target lateral displacement to +10 cm (S105). Here, the positive or negative value of the target lateral displacement is related to whether the vehicle 2 is offset to the left or right with respect to the direction of travel. For example, if the target lateral displacement is set to the positive side, the vehicle 2 will be offset to the right with respect to the direction of travel. For example, in the case of precise docking control to park alongside the platform 15 on the left side with respect to the direction of travel, it is good to set a positive target lateral displacement in step S105. For example, in the case of precise docking control to park alongside the platform 15 on the right side with respect to the direction of travel, it is good to set a negative target lateral displacement in step S105.

[0046] After entering the side-to-side path 130, the control unit 40 determines the distance traveled after entering the side-to-side path 130 by counting the number of detected magnetic markers 10. The control unit 40 then detects that the vehicle has passed through the diversion section 133 and reached the starting point 131S of the straight section 131 (see Figure 7). The control unit 40 continuously sets a target lateral displacement of +10cm from the starting point 131S of the straight section 131 to a point 3m away (S104:YES → S106:NO) (S105). The control unit 40 identifies the deviation between the target lateral displacement of +10cm and the measured lateral displacement relative to the detected magnetic markers 10 (S110), and executes driving control, including steering angle control, to bring this deviation closer to zero (S111).

[0047] Here, the period from the starting point 131S of the straight section 131 to the point 3m away is the period during which the control unit 40 performs preliminary control. After passing the starting point 131S of the straight section 131, the control unit 40 determines the distance traveled after passing the starting point 131S of the straight section 131 by counting the number of detected magnetic markers 10.

[0048] In the preliminary control, the vehicle 2 is moved to a virtual platform 159 located in front of the actual platform 15 in both the forward and lateral directions (see Figure 7). The trajectory of the vehicle 2 when it approaches the virtual platform 159 is as shown by the hatching line HL in Figure 7. This hatching line HL is positioned offset from the arrangement line of the magnetic markers 10. The offset between the hatching line HL and the arrangement line of the magnetic markers 10 is caused by the target lateral displacement of +10 cm set in step S105 above.

[0049] The virtual platform 159 (Figure 7) is located in front of the actual platform 15 in the direction of travel, and is offset 10 cm to the right in the lateral direction. The virtual platform 159 virtually extends along the stopping direction, which is the orientation of the vehicle 2 when it is parked alongside platform 15.

[0050] The control unit 40 sets the target lateral displacement to +5 cm (S107) for the section from 3 m past the starting point 131S of the straight section 131 to 3.5 m (S106: YES → S108: NO). The control unit 40 identifies the deviation between the target lateral displacement of 5 cm and the measured lateral displacement relative to the detected magnetic marker 10 (S110), and performs driving control, including steering angle control, to bring this deviation closer to zero (S111).

[0051] Subsequently, when the control unit 40 has passed a point 3.5m from the starting point 131S of the straight section (S108:YES), it sets the target lateral displacement to zero (S109). The control unit 40 then identifies the deviation between the target lateral displacement of zero and the measured lateral displacement relative to the detected magnetic marker 10 (S110), and executes driving control, including steering angle control, to bring this deviation closer to zero (S111). The control unit 40 executes driving control, including steering angle control, to bring this deviation closer to zero until the vehicle 2 reaches the stopping position 135 (S112:NO). When the vehicle 2 reaches the stopping position 135 (S112:YES), the control unit 40 terminates the precise stopping control.

[0052] In the precise docking control shown in the flow of Figure 6, the control performed after passing the point 3.5m from the starting point 131S of the straight section 131 is the final control to bring the vehicle 2 alongside the platform 15 and stop. In the precise docking control of this example, preliminary control is performed to move the vehicle 2 closer to a virtual platform 159 that extends 10cm laterally from the platform 15, and then the final control is performed to bring the vehicle alongside the actual platform 15.

[0053] In this example of precise docking control, the control unit 40 sets a target lateral displacement amount, thereby shifting the control target line relative to the arrangement line of magnetic markers 10 in the docking path 130. As a result, the vehicle 2 docks alongside the platform 15 following the trajectory of the hatching line HL in Figures 7 and 8. Figure 8 is an enlarged view of the area around the platform 15.

[0054] The hatching line HL in Figures 7 and 8 represents the trajectory of the leading towing vehicle 21. When the towing vehicle 21 moves along this hatching line HL and reaches the stopping position 135, as shown in the figures, the orientation of the four-wheel steering vehicle, the bogie 23, coincides with the orientation of the towing vehicle 21 (the stopping direction), and the bogie 23 is positioned alongside the platform 15.

[0055] In this example of precise docking control, after passing the starting point of the straight section 131, during the pre-control period up to a point 3m from this starting point, the vehicle 2 is moved to the virtual platform 159 located in front of platform 15 in both the direction of travel and the lateral direction (see Figure 7). The lateral offset between platform 15 and virtual platform 159 is 10cm.

[0056] Therefore, after performing preliminary control, the final control for positioning the vehicle 2 alongside the platform 15 only requires moving it forward by a mere 10 cm. Thus, in this example of precise positioning control, the approach angle of the vehicle 2 when positioning alongside the platform 15 can be suppressed. By suppressing the approach angle of the vehicle 2, the vehicle 2 can be precisely positioned on the platform 15 while suppressing the amount of swing-out of the rear wheels 232 of the bogie 23, which is a four-wheel steering vehicle. In this case, it is possible to efficiently precisely position the vehicle 2 on the platform 15 by utilizing the advantages of a four-wheel steering vehicle while mitigating the disadvantage of a four-wheel steering vehicle, where some swing-out of the rear wheels 232 is unavoidable.

[0057] The virtual platform 159 is positioned laterally in front of the actual platform 15, providing lateral clearance for equipment and other facilities. Therefore, even if the rear wheels 232 of the bogie 23, which is a four-wheel steering vehicle, swing outward, there is less risk of interference with the equipment.

[0058] Furthermore, when moving vehicle 2 towards platform 15, controlling the trajectory of the front wheels 211 of the front-wheel steering towing vehicle 21 to make a wide turn outward can shorten the time required for precise docking control. In the demonstration experiment, in the case of vehicle 2 in this example, for example, when allowing a wide turn of 10 mm or less for the towing vehicle 21, the swing amount of the rear wheels 232 of the four-wheel steering bogie 23 was found to be about 30 mm.

[0059] In this example configuration, the lateral offset amount of the virtual platform 159 relative to the platform 15 is set based on this swing amount of 30 mm. The lateral offset amount of the virtual platform 159 is preferably between 1 and 5 times the swing amount of the rear wheels 232 of the bogie 23. In this example, the lateral offset amount of the virtual platform 159 relative to the platform 15 is set to 10 cm (100 mm), which is approximately 3.3 times the swing amount of the rear wheels of the bogie 23, which is 30 mm.

[0060] If the offset amount of the virtual platform 159 is less than one times the swing amount of the rear wheels 232, there is a risk that the rear wheels 232, which are swung outward during pre-control, may come too close to equipment or devices, and the effect of setting pre-control may not be fully realized. On the other hand, if the offset amount of the virtual platform 159 exceeds five times the swing amount of the rear wheels 232, the approach angle when the vehicle 2 arrives at platform 15 from the virtual platform 159 may not be sufficiently suppressed, and the effect of executing pre-control may not be fully realized.

[0061] In this example, as described above, at least two magnetic markers 10 are arranged along the platform 15, and these at least two magnetic markers 10 are arranged in a straight line up to the set range of the virtual platform 159 in the stopping direction (the direction of travel of the vehicle 2). In this example, preliminary control is achieved by adjusting the vehicle's width towards the virtual platform by setting a variable target lateral displacement amount.

[0062] Alternatively, as illustrated in Figure 9, at least two magnetic markers 10 may be arranged along the platform 15, and at least two magnetic markers 10 may also be arranged along the virtual platform 159. Here, "along the virtual platform 159" means along the trajectory of the vehicle 2 used to move towards the virtual platform 159. The arrangement line of magnetic markers 10 along the platform 15 and the arrangement line of magnetic markers 10 along the virtual platform 159 are parallel but at different levels. When the magnetic markers 10 are laid as shown in Figure 9, the control for both the platform 15 and the virtual platform 159 remains set to a common predetermined value (e.g., zero).

[0063] In this example, a docking control method is demonstrated using a single virtual platform 159. Alternatively, multiple virtual platforms can be used to gradually move the vehicle 2 towards platform 15 by performing preliminary control in stages. By using multiple virtual platforms, the unique behavior of the rear wheels 232 of the four-wheel-steering bogie 23 due to reverse-phase steering can be further suppressed during docking control. When using multiple virtual platforms, it is advisable to set the lateral offset between adjacent virtual platforms to between 1 and 5 times the swing-out amount of the rear wheels 232 of the bogie 23. In this case, the effect of placing another virtual platform in front of a virtual platform can be enhanced.

[0064] In this example, the towing vehicle 21 is shown as a vehicle 2 that tows one bogie (4WS bogie) 23. However, the vehicle may also have two, three, or more 4WS bogies connected to it. The docking control method in this example may also be applied to a four-wheel steering vehicle with drive wheels. Furthermore, the four-wheel steering vehicle with drive wheels may also tow one or more 4WS bogies.

[0065] In this example, a magnetic sensor array 3 is installed at the front of the towing vehicle 21, and the towing vehicle 21 is controlled so that the amount of lateral displacement relative to the magnetic marker 10 measured by the magnetic sensor array 3 approaches a predetermined value. Alternatively, the magnetic sensor array may be installed at the rear of the towing vehicle 21. In this case, a control point should be set in front of the towing vehicle 21 in the longitudinal direction, and the amount of lateral displacement measured by the magnetic sensor array should be converted into the amount of lateral displacement at the control point. By using the amount of lateral displacement at the control point located in front as the control target, the control delay problem caused by placing the magnetic sensor array at the rear of the vehicle can be avoided.

[0066] In this example, a precise docking control method for vehicle driving control using magnetic markers 10 is illustrated. Vehicle driving control may be controlled using guidance such as magnetic markers 10, autonomous navigation, or a GNSS system or indoor positioning system. The precise docking control method in this example is widely applicable regardless of the specifications of the vehicle driving control.

[0067] Although specific examples of the present invention have been described in detail as shown in the examples above, these examples only disclose an example of the technology covered by the claims. Needless to say, the claims should not be interpreted restrictively based on the configuration or numerical values ​​of the specific examples. The claims encompass technologies obtained by various modifications or changes to the above examples using prior art or the knowledge of those skilled in the art. [Explanation of Symbols]

[0068] 1. Vehicle System 10 Magnetic Markers 11 Main Route 13 Branching Routes 130 Side access route 131 Straight section 133 Diversion Section 135 Stop position 15 Platforms 159 Virtual Platforms 2 vehicles 21 Towing vehicles 211 Front Wheel 212 Rear wheel 23. Bogies (4-wheel steering vehicles, 4WS bogies) 231 Front Wheel 232 Rear wheel 24, 25 Link mechanism 3. Magnetic sensor array 40 Control Units

Claims

1. A method for precisely controlling a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, to come alongside a platform and stop, The unit that controls the movement of the vehicle is: A virtual platform is set at a position that is on the front side of the platform in both the direction of stopping and the direction perpendicular to the stopping direction, where the vehicle is facing when it is parked alongside the platform and stopped. A precise docking control method for stopping a vehicle alongside the platform is characterized by performing preliminary control to bring the vehicle closer to the virtual platform.

2. A method for precisely controlling a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, to come alongside a platform and stop, The unit that controls the movement of the vehicle is: A virtual platform is set at a position that is on the front side of the platform in both the direction of stopping and the direction perpendicular to the stopping direction, where the vehicle is facing when it is parked alongside the platform and stopped. In the precise docking control for bringing the vehicle alongside the platform and stopping it, preliminary control is performed to bring the vehicle closer to the virtual platform. A docking control method characterized in that the unit that controls the movement of the vehicle sets the virtual platform such that the lateral offset amount with respect to the platform is between 1 and 5 times the amount of outward swing of the rear wheels when the rear wheels of the four-wheel steering vehicle are steered in opposite phases while driving.

3. A method for precisely controlling a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, to come alongside a platform and stop, The unit that controls the movement of the vehicle is: A virtual platform is set at a position that is on the front side of the platform in both the direction of stopping and the direction perpendicular to the stopping direction, where the vehicle is facing when it is parked alongside the platform and stopped. In the precise docking control for bringing the vehicle alongside the platform and stopping it, preliminary control is performed to bring the vehicle closer to the virtual platform. On the road surface on which the vehicle travels, at least two or more magnetic markers are arranged along the platform, and at least two or more magnetic markers are arranged along the virtual platform. A unit that controls the movement of the vehicle controls the lateral deviation relative to the magnetic marker, and controls the movement of the vehicle to bring the lateral deviation closer to a predetermined value, in a method for precise docking control.

4. A method for precisely controlling a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, to come alongside a platform and stop, The unit that controls the movement of the vehicle is: A virtual platform is set at a position that is on the front side of the platform in both the direction of stopping and the direction perpendicular to the stopping direction, where the vehicle is facing when it is parked alongside the platform and stopped. In the precise docking control for bringing the vehicle alongside the platform and stopping it, preliminary control is performed to bring the vehicle closer to the virtual platform. On the road surface on which the vehicle travels, at least two or more magnetic markers are arranged along the platform, and these at least two or more magnetic markers extend to the set range of the virtual platform in the stopping direction. The vehicle is steered with the lateral deviation relative to the magnetic marker as the control target. A precise docking control method characterized in that the unit that controls the movement of the vehicle sets different values ​​as the control target value for the lateral deviation when executing control to bring the vehicle alongside the platform and when executing the preliminary control to move the vehicle closer to the virtual platform.

5. A method for precisely controlling a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite phases, to come alongside a platform and stop, The unit that controls the movement of the vehicle is: A virtual platform is set at a position that is on the front side of the platform in both the direction of stopping and the direction perpendicular to the stopping direction, where the vehicle is facing when it is parked alongside the platform and stopped. In the precise docking control for bringing the vehicle alongside the platform and stopping it, preliminary control is performed to bring the vehicle closer to the virtual platform. The unit that controls the movement of the vehicle sets up a plurality of virtual platforms such that the amount of lateral offset relative to the platform increases in stages as the vehicle moves away from the platform in the stopping direction. A precise docking control method characterized by performing multiple pre-controls to move the vehicle closer to multiple virtual platforms.

6. The docking control method according to claim 5, wherein the lateral offset amount of adjacent virtual platforms is 1 to 5 times the amount of outward swing of the rear wheels when the rear wheels of the four-wheel steering vehicle are steered in opposite phases while driving.

7. A vehicle system for bringing a vehicle, which includes at least a four-wheel steering vehicle in which the rear wheels are steered in opposite directions, alongside a platform and stopping it, A circuit sets a virtual platform that virtually extends along the stopping direction, which is the direction in which the vehicle is facing when the vehicle is parked alongside the platform, at a position that is on the front side of the platform in both the stopping direction and the lateral direction perpendicular to the stopping direction, Includes a circuit for controlling the vehicle, The vehicle system is configured such that, in a precise docking control for bringing the vehicle alongside the platform and stopping it, it performs preliminary control to move the vehicle closer to the virtual platform, and after the execution of the preliminary control, it performs control to bring the vehicle alongside the platform and stop it.

8. In claim 7, on the road surface on which the vehicle travels, at least two or more magnetic markers are arranged along the platform, and at least two or more magnetic markers are arranged along the virtual platform, A vehicle system in which a circuit for controlling the vehicle controls the vehicle with respect to the lateral deviation relative to the magnetic marker as the control target, and sets a common value as the control target value for the lateral deviation for control of moving the vehicle closer to the virtual platform and control of moving the vehicle alongside the platform.

9. In claim 7, on the road surface on which the vehicle travels, at least two or more magnetic markers are arranged along the platform, and the at least two or more magnetic markers are arranged in a straight line to the set range of the virtual platform in the stopping direction. A vehicle system in which a circuit for controlling the vehicle controls the vehicle with respect to the lateral deviation relative to the magnetic marker as the control target, and sets different values ​​as the control target value for the lateral deviation for control of moving the vehicle closer to the virtual platform and control of moving the vehicle alongside the platform.

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