Transportation vehicle

Abstract

To provide a transportation vehicle including a plurality of travel devices, the transportation vehicle being capable of appropriately estimating a position of the traveling vehicle.SOLUTION: An autonomous travel controller 11 of a transportation vehicle 1 acquires a steering angle of a wheel 21 with respect to, as a reference, a vehicle front and rear direction D1 in a plurality of travel devices 6A to 6H, and calculates an average steering angle being an average value of the acquired steering angle. The autonomous travel controller 11 estimates a current vehicle position on the basis of the calculated average steering angle and an acquired vehicle speed, and controls driving of the travel devices 6A to 6H and steering devices 7A to 7H on the basis of the estimated current vehicle position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an autonomously driven transport vehicle. [Background technology]

[0002] Patent Document 1 describes a vehicle that can estimate the vehicle position during travel and calculate a command value for autonomous travel to a target position using the estimated vehicle position. The vehicle described in Patent Document 1 estimates the vehicle position by using the vehicle speed and the angular velocity of the vehicle about an axis parallel to the height direction. Hereinafter, the angular velocity of the vehicle about an axis parallel to the height direction will also be simply referred to as the angular velocity of the vehicle. For example, command values ​​for the vehicle speed and steering angle required for autonomous travel are calculated using the distance and direction from the estimated vehicle position to the target position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-53536 Summary of the Invention [Problem to be solved by the invention]

[0004] A transport vehicle equipped with multiple travel devices with independently steerable wheels is known. In such a transport vehicle, steering the wheels of each travel device allows the vehicle to travel in a direction parallel to the direction of travel, or to travel in a direction different from the direction of travel, i.e., so-called diagonal travel or lateral travel.

[0005] However, when a transport vehicle travels diagonally or sideways, there is little change in the direction of the vehicle, and if the vehicle position is estimated using only the angular velocity of the vehicle, a discrepancy may occur between the actual vehicle position and the estimated vehicle position.

[0006] In order to solve the above problem, an object of the present invention is to provide a transport vehicle equipped with a plurality of traveling devices that can accurately estimate the vehicle position. [Means for solving the problem]

[0007] In order to solve the above problems, the transport vehicle of the present invention is an autonomous transport vehicle that includes a vehicle body including a loading platform, a plurality of traveling devices arranged on the vehicle body and having independently steerable wheels, and a steering device that steers the wheels of each of the plurality of traveling devices. The transport vehicle includes a speed acquisition unit that acquires a vehicle speed that is the speed of the transport vehicle, an average steering angle calculation unit that acquires steering angles of the wheels of the plurality of traveling devices based on the longitudinal direction of the vehicle and calculates an average steering angle that is the average value of the acquired steering angles of the wheels, a position estimation unit that estimates a current vehicle position of the transport vehicle based on the calculated average steering angle and the acquired vehicle speed, and a travel control unit that controls the drive of the traveling devices and the steering device based on the estimated current vehicle position.

[0008] In the transport vehicle having the above configuration, even when the vehicle is traveling in a traveling mode with little change in angular velocity, the traveling direction of the vehicle can be calculated from the average value of the steering angles of the wheels of the multiple traveling devices. Furthermore, even when there is variation in the actual steering angles between the multiple traveling devices, the traveling direction can be calculated using the average steering angles, thereby suppressing a decrease in the calculation accuracy of the traveling direction caused by the variation in the actual steering angles. As a result, the vehicle position of the transport vehicle can be accurately estimated. [Effects of the Invention]

[0009] According to the present invention, in a transport vehicle equipped with a plurality of traveling devices each having independently steerable wheels, it is possible to suppress a decrease in the estimation accuracy of the vehicle position and to allow the vehicle to travel autonomously in an appropriate manner. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. [Figure 2]FIG. 2 is a diagram illustrating the arrangement of a plurality of traveling devices. [Figure 3] FIG. 2 is a diagram illustrating an electrical configuration of a transport vehicle. [Figure 4] 10 is a flowchart illustrating the processing of the autonomous driving controller in an autonomous driving mode. [Figure 5] FIG. 10 is a diagram illustrating oblique traveling. [Figure 6] FIG. 2 is a diagram illustrating estimation of a vehicle position. [Figure 7] 10 is a flowchart illustrating processing by an autonomous driving controller in an autonomous driving mode according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) An embodiment of a transport vehicle will be described with reference to the drawings. FIG. 1 is a side view of a transport vehicle 1 according to this embodiment. FIG. 2 is a view of the transport vehicle 1 as seen from the bottom side, and is a schematic diagram illustrating the arrangement of multiple traveling devices 6. FIG. 3 is a diagram mainly illustrating the electrical configuration of the transport vehicle 1. The transport vehicle 1 is a vehicle used for transporting long, heavy objects. The transport vehicle 1 is an electric vehicle that travels by operating a traveling motor 12 and a steering motor 13 (shown in FIG. 3) using electricity stored in a battery unit (not shown) as a power source. The transport vehicle 1 is also configured to be able to switch between a driving traveling mode in which the vehicle travels while being driven by a driver, and an autonomous traveling mode in which the vehicle travels autonomously.

[0012] Hereinafter, the direction extending along the front and rear of the transport vehicle 1 will be referred to as the "vehicle longitudinal direction D1." In the vehicle longitudinal direction D1, the side where the driver's cab 5 described below is located will be referred to as the "front side," and the side where the driver's cab 5 is not located will be referred to as the "rear side." In the transport vehicle 1, the direction extending along the vehicle width will be referred to as the "vehicle left-right direction D2." When facing the front side of the transport vehicle 1 (i.e., the side where the driver's cab 5 is located), the right side will be defined as the "right side," and the left side will be defined as the "left side." The vehicle left-right direction D2 is also a direction perpendicular to the vehicle longitudinal direction D1. In the transport vehicle 1, the direction extending along the vehicle height will be referred to as the "height direction D3."

[0013] The transport vehicle 1 comprises a vehicle body 2, a plurality of travelling devices 6, and a plurality of steering devices 7 (shown in FIG. 3). The vehicle body 2 comprises a vehicle body frame 3, a loading platform 4 for carrying heavy objects, and a driver's cab 5 where the driver gets in to drive. The vehicle body frame 3 is roughly rectangular in plan view and is composed of a pair of elongated side members extending in the vehicle's fore-and-aft direction D1, and four cross members extending between the pair of side members in the vehicle's left-right direction D2. The loading platform 4 is arranged on the upper surface of the vehicle body frame 3 and is configured to be able to be raised and lowered in the height direction D3 using known technology.

[0014] The plurality of traveling units 6 are attached to the bottom side of the body frame 3 of the vehicle body 2. As shown in FIG. 2, the transfer vehicle 1 is equipped with eight traveling units 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H arranged in the vehicle longitudinal direction D1 and the vehicle transverse direction D2, respectively. Specifically, one set (i.e., two traveling units) of traveling units 6 are arranged in the vehicle transverse direction D2 relative to the body frame 3, and four sets of traveling units 6 are arranged in the vehicle longitudinal direction D1. Hereinafter, when distinguishing between the plurality of traveling units 6A to 6H, the traveling units 6A to 6H will be distinguished by describing them as, from the front, the first traveling unit 6A, the second traveling unit 6B, the third traveling unit 6C, the fourth traveling unit 6D, the fifth traveling unit 6E, the sixth traveling unit 6F, the seventh traveling unit 6G, and the eighth traveling unit 6H.

[0015] Each of the traveling units 6A to 6H has a pair (two) of wheels 21 connected via an axle. The axle is rotatably held at the lower end of a swing arm that constitutes the traveling unit 6A to 6H. The upper end of the swing arm is supported by a suspension bracket so that it can swing up and down relative to the body frame 3. The upper end of the suspension bracket is attached to the body frame 3 so that it can rotate horizontally.

[0016] Each of the traveling devices 6A to 6H has a traveling motor 12 (FIG. 3) for rotating the axle together with the wheels 21 to travel the transport vehicle 1. The traveling motor 12 is connected to a traveling PLC 10 (described later) and is configured to be rotatable in response to a control signal from the traveling PLC 10.

[0017] In this embodiment, all eight traveling devices 6A to 6H are equipped with traveling motors 12, and the wheels 21 of the traveling devices 6A to 6H can be independently rotated and driven by each traveling motor 12. However, the present invention is not limited to this, and a configuration in which traveling motors 12 are equipped only to some of the traveling devices 6A to 6H may be adopted. In this case, the traveling devices 6A to 6H equipped with traveling motors 12 are devices that generate driving force for traveling, and the traveling devices 6A to 6H that do not have traveling motors 12 are devices that travel in response to traveling.

[0018] As shown in FIG. 2, on the body frame 3, the midpoint in the vehicle longitudinal direction D1 between the first and second traveling units 6A and 6B, which are arranged at the forefront, and the seventh and eighth traveling units 6G and 6H, which are arranged at the rearmost, is defined as a virtual midpoint M. The first to fourth traveling units 6A to 6D are arranged on the body frame 3 forward of the midpoint M in the vehicle longitudinal direction D1, and the fifth to eighth traveling units 6E to 6H are arranged on the body frame 3 rearward of the midpoint M. Furthermore, the traveling units 6A to 6D arranged on the body frame 3 forward of the midpoint M in the vehicle longitudinal direction D1 are arranged on the body frame 3 so as to be point-symmetrical with respect to the midpoint M with respect to the traveling units 6E to 6H arranged on the body frame 3 rearward of the midpoint M. Specifically, the first traveling unit 6A and the eighth traveling unit 6H are arranged on the body frame 3 so as to be point-symmetrical with respect to the midpoint M. Similarly, the second running device 6B and the seventh running device 6G, the third running device 6C and the sixth running device 6F, and the fourth running device 6D and the fifth running device 6E are each arranged on the body frame 3 so as to be point symmetrical with respect to the midpoint M.

[0019] As shown in FIG. 3, steering devices 7A to 7H for independently steering the wheels 21 of each traveling device 6A to 6H are disposed on the body frame 3 of this embodiment. Each steering device 7A to 7H includes a steering motor 13 and a reducer 22 and is fixed to the body frame 3. For convenience, FIG. 3 illustrates the steering motor 13 and reducer 22 only for the steering device 7A, and does not illustrate those for the other steering devices 7B to 7H. The steering motor 13 is connected to a traveling PLC 10 (described later) and can rotate an output shaft in response to a command from the traveling PLC 10. The rotation of the output shaft of the steering motor 13 is transmitted to the traveling devices 6A to 6H via the reducer 22, and the traveling devices 6A to 6H are rotated horizontally relative to the body frame 3, thereby independently steering the direction of each wheel 21. Note that the transport vehicle 1 may be configured such that a single steering device steers multiple traveling devices.

[0020] In this embodiment, the turning angle of the wheels 21 of the traveling devices 6A to 6H is indicated by an angle based on the vehicle longitudinal direction D1, i.e., a "steering angle." The steering angle is an angle determined within a range of 0 to 180 degrees to the right and 0 to 180 degrees to the left based on the vehicle longitudinal direction D1.

[0021] As shown in FIG. 3, the transfer vehicle 1 further includes a travel PLC 10, an autonomous travel controller 11, multiple sensors 14, 15, and 16 that detect physical quantities generated during travel, and a communication IF 17. PLC is an abbreviation for "Programmable Logic Controller." "IF" is an abbreviation for "Interface." In this embodiment, the various sensors 14, 15, and 16 are described as devices separate from the travel devices 6A-6H and the steering devices 7A-7H, but the sensors 14, 15, and 16 may be provided as part of the travel devices 6A-6H and the steering devices 7A-7H. Alternatively, the transfer vehicle 1 may not include these sensors 14, 15, and 16, and may acquire data on speed and steering angle by means other than sensors.

[0022] The vehicle speed sensor 14 is a sensor that detects the vehicle speed, which is the speed of the transfer vehicle 1 in the traveling direction, and is, for example, a wheel speed sensor. The gyro sensor 15 is a sensor that detects the angular velocity ω of the transfer vehicle 1 based on an axis parallel to the height direction D3, and is, for example, an IMU (Inertial Measurement Unit) sensor. Here, the "vehicle orientation" is a value that uses the direction in which the front side of the cab 5 of the transfer vehicle 1 faces as a reference (0 degrees), and as will be described later, may differ from the traveling direction, which is the direction in which the transfer vehicle 1 advances, when the transfer vehicle 1 travels obliquely or laterally.

[0023] The steering angle sensor 16 is a sensor for detecting the steering angle δ of the wheels 21 of the traveling devices 6A to 6H. In this embodiment, the steering angle sensor 16 is a sensor, such as a potentiometer, that detects the actual steering angle of the wheels 21 of the traveling devices 6A to 6H relative to the vehicle longitudinal direction D1. The steering angle sensor 16 detects the actual steering angle δ of one of the pair of wheels 21 provided on each traveling device 6A to 6H. Alternatively, the steering angle sensor 16 may detect the rotation angle of the steering motor 13 in the steering devices 7A to 7H and estimate and calculate the steering angle δ of the traveling device 6 from the detected rotation angle of the steering motor 13.

[0024] In this embodiment, four steering angle sensors 16 detect the steering angle δ of each of the first traveling device 6A, the second traveling device 6B, the seventh traveling device 6G, and the eighth traveling device 6H among the traveling devices 6A to 6H. Therefore, as will be described later, the steering angles δ of the four traveling devices 6A, 6B, 6G, and 6H are input to the autonomous traveling controller 11 from the steering angle sensors 16. However, the present invention is not limited to this, and a configuration may be adopted in which steering angle sensors 16 are attached to all eight traveling devices 6A to 6H, so that the steering angles δ of the eight traveling devices 6A to 6H are input to the autonomous traveling controller 11.

[0025] The communication IF 17 is an interface for communicating with an external device (not shown), and is a wireless communication IF capable of wireless communication such as the Wi-Fi (registered trademark) standard. The transport vehicle 1 can communicate with an external device for managing the operation of the transport vehicle 1, such as a management server, via the communication IF 17.

[0026] The traveling PLC 10 includes a CPU, ROM, RAM, and a motor driver, and is connected to traveling motors 12 provided in the traveling devices 6A to 6H and steering motors 13 provided in the steering devices 7A to 7H. Although not shown, the traveling PLC 10 is also connected to a steering wheel and various operating levers that accept operations by the driver to drive the transfer vehicle 1. In the driving and traveling mode, the traveling PLC 10 controls the driving of the traveling devices 6A to 6H and the steering devices 7A to 7H in accordance with the amount of operation of the steering wheel and operating levers by the driver, thereby causing the transfer vehicle 1 to travel.

[0027] The autonomous driving controller 11 is a device that outputs a control signal to the driving PLC 10 in the autonomous driving mode to cause the transport vehicle 1 to drive autonomously. The autonomous driving controller 11 has, for example, a CPU, a ROM, and a RAM, similar to the driving PLC. The autonomous driving controller 11 is also connected to the driving PLC 10, the various sensors 14 to 16 already described, and the communication IF 17.

[0028] In the autonomous driving mode, the autonomous driving controller 11 estimates the current vehicle position (Pi(x, y), Qi(u, v) described later) of the transport vehicle 1. "i" is an identifier indicating the coordinates at a certain time i. The autonomous driving controller 11 uses the estimated current vehicle position to calculate command values ​​required for autonomous driving and transmits them to the driving PLC 10. Details of the specific control by the autonomous driving controller 11 will be described later.

[0029] When the transport vehicle 1 travels in the autonomous travel mode, the autonomous travel controller 11 receives command information from an external device via the communication IF 17. The command information includes information indicating the route along which the transport vehicle 1 should travel, such as coordinates of nodes that the transport vehicle 1 should pass on this route, route parameters, and travel parameters. Here, the "route parameters" include information indicating the curvature of a route formed by connecting multiple nodes. The "travel parameters" include information indicating the vehicle speed, vehicle direction, and travel mode (diagonal travel, sideways travel, V-shaped travel, etc.) specified for each route. The information included in the command information described above is an example. Note that the autonomous travel controller 11 may store the command information in memory in advance, rather than receiving it from an external device, and then expand and read it into RAM or the like during autonomous travel.

[0030] Among the traveling modes specified by the command information, the diagonal traveling and the lateral traveling are traveling modes in which the transportation vehicle 1 travels with all the wheels 21 of the traveling devices 6A to 6H steered at the same steering angle, so that the vehicle faces in a direction different from the traveling direction. Specifically, when the traveling mode "diagonal traveling" is specified by the command information, the transportation vehicle 1 travels with all the wheels 21 of the traveling devices 6A to 6H tilted at the specified steering angle δ. Also, when the traveling mode "lateral traveling" is specified by the command information, the transportation vehicle 1 travels with all the wheels 21 of the traveling devices 6A to 6H steered at the steering angle δ of approximately 90 degrees relative to the vehicle's direction. In addition, V-shaped running is a running mode in which the transport vehicle 1 is run with the wheels 21 of the first to fourth running devices 6A to 6D, which are arranged forward of the midpoint M on the vehicle body 2, being steered at an angle δ toward the vehicle's turning direction, and the wheels 21 of the fifth to eighth running devices 6E to 6H, which are arranged rearward of the midpoint M, being steered at an angle δ toward the opposite side to the vehicle's turning direction.

[0031] Next, a specific processing procedure executed by the autonomous driving controller 11 when the transport vehicle 1 is driven in the autonomous driving mode will be described with reference to Fig. 4. For example, in the autonomous driving mode, the autonomous driving controller 11 starts the processing shown in Fig. 4 when command information is received from an external device. Alternatively, the autonomous driving controller 11 may start the processing shown in Fig. 4 when it determines that the transport vehicle 1 has reached a predetermined destination.

[0032] In step 10, the autonomous driving controller 11 acquires the current vehicle speed V detected by the vehicle speed sensor 14 and the current angular speed ω detected by the gyro sensor 15. Hereinafter, each step will be abbreviated as "S." Note that, hereinafter, "acquire" means that the autonomous driving controller 11 expands the detected values ​​from the various sensors 14 to 16 on RAM and makes them available for use in each process. In this embodiment, the speed acquisition unit is realized by the process executed by the autonomous driving controller 11 in S10.

[0033] Next, the autonomous driving controller 11 estimates the current vehicle position by processing steps S11 to S14, which will be described later. Here, when the transportation vehicle 1 travels in the "diagonal traveling" or "lateral traveling" traveling mode, the vehicle orientation changes little and the vehicle travels with its orientation different from the traveling direction, making it difficult to estimate the vehicle position using only the angular velocity ω of the vehicle. In FIG. 5, during diagonal traveling, the vehicle position estimated using only the vehicle orientation is shown by a dashed-dotted line relative to the actual vehicle position shown by a solid line in the figure. In this example, the transportation vehicle 1 travels with its traveling direction tilted by a predetermined angle α with respect to the vehicle orientation θ, but the change in the vehicle orientation θ is approximately constant. Therefore, if the vehicle orientation θ is calculated using only the angular velocity ω and the vehicle positions Pi(x, y) and Qi(u, v) are estimated, the estimated vehicle position will be a position that is offset from the actual vehicle position. Therefore, in this embodiment, the autonomous driving controller 11 estimates the current vehicle position using the average value of the steering angle δ.

[0034] First, in S11, the autonomous traveling controller 11 acquires the steering angles δA, δB, δG, and δH of each traveling device 6A, 6B, 6G, and 6H detected by the steering angle sensor 16. As shown in Fig. 6, "steering angle δA" indicates the steering angle of the wheel 21 of the first traveling device 6A, and "steering angle δB" indicates the steering angle of the wheel 21 of the second traveling device 6B. "steering angle δG" indicates the steering angle of the wheel 21 of the seventh traveling device 6G, and "steering angle δH" indicates the steering angle of the wheel 21 of the eighth traveling device 6H.

[0035] In S12, the autonomous driving controller 11 calculates an average steering angle δavg from the acquired steering angles δ. Even if the steering angle command values ​​for the steering devices 7A-7H specify the same angle, variations may occur in the actual steering angles δ of the wheels 21 of the traveling devices 6A, 6B, 6G, and 6H depending on the traveling devices 6A-6H, the mechanical characteristics of the traveling devices 6A-6H, and the road surface conditions. Therefore, in this embodiment, the autonomous driving controller 11 calculates the average value of the four actual steering angles δA, δB, δG, and δH detected by the steering angle sensor 16, thereby suppressing the impact of variations in the steering angles δ on the estimation accuracy of the vehicle position Pi(x, y). In other words, the autonomous driving controller 11 calculates the average steering angle using the steering angles of the four driving devices 6A, 6B, 6G, and 6H that are arranged symmetrically from the midpoint M on the body frame 3, thereby calculating the diagonal component when the transport vehicle 1 is traveling, and calculating the direction of travel of the transport vehicle 1 regardless of the driving mode, such as V-shaped driving, diagonal driving, or lateral driving.

[0036] Specifically, the autonomous driving controller 11 calculates the average steering angle δavg from the four acquired steering angles δ using the following (Equation 1). δavg = (δA+δB+δG+δH) / 4 … (Formula 1) In this embodiment, the autonomous driving controller 11 implements an average steering angle calculation unit by executing the processes in S11 and S12.

[0037] In S13, the autonomous driving controller 11 estimates the current (i.e., i=m) vehicle position Pm(x, y) on the vehicle coordinate system using the current vehicle speed Vm and the calculated average steering angle δavg. The vehicle coordinate system is a relative coordinate system in which a reference position P0 of the transfer vehicle 1 is set as the origin and coordinate axes (x-axis, y-axis) are provided in the vehicle longitudinal direction D1 and the vehicle lateral direction D2 of the transfer vehicle 1. In this embodiment, the reference position P0 is set to a position on the front side of the vehicle, more specifically, a position forward of the first and second traveling units 6A, 6B on the body frame 3 and intermediate between the first and second traveling units 6A, 6B in the vehicle lateral direction D2. In estimating the vehicle position Pm(x, y), the autonomous driving controller 11 sets the reference position P0 of the transfer vehicle 1 at the previous time, i.e., the time Δt ago, as the origin, and calculates the amount of movement from this reference position P0 as the current vehicle position Pm(x, y).

[0038] In this embodiment, the autonomous driving controller 11 calculates the coordinates xm and ym, which are components of the vehicle position Pm(x, y), using the following (Equation 2) and (Equation 3). xm=Vm×Δt×cos(δavg) … (Formula 2) ym=Vm×Δt×sin(δavg) … (Formula 3)

[0039] In the above (Equation 2) and (Equation 3), as shown in FIG. 6, the calculated average steering angle δavg is used as the traveling direction from the reference position P0 of the vehicle coordinates (i.e., vehicle position Pm-1(x, y)). Then, by using the above (Equation 2), the estimated traveling distance "Vm × Δt" corresponding to the vehicle speed Vm is resolved into the x-axis component, which is the vertical component of this estimated traveling distance, according to the traveling direction "δavg," to calculate the travel amount (i.e., coordinate x) to the vehicle position Pm(x, y). Furthermore, by using the above (Equation 3), the estimated traveling distance "Vm × Δt" is resolved into the y-axis component, which is the horizontal component of this estimated traveling distance, according to the traveling direction "δavg," to calculate the travel amount (i.e., coordinate y) to the vehicle position Pm(x, y).

[0040] In this embodiment, the steering angle δ of the wheels 21 of the traveling units 6A, 6B, 6G, and 6H that are arranged spaced apart in the vehicle longitudinal direction D1 across a virtual midpoint M of the vehicle body 2 is used to calculate the average steering angle δavg. Therefore, by using the steering angles δ of not only the traveling units 6A and 6B located at the front of the vehicle but also the traveling units 6G and 6H located at the rear of the vehicle to calculate the average steering angle δavg, the calculation accuracy in the traveling direction of the transfer vehicle 1 can be improved.

[0041] In S14, the autonomous driving controller 11 converts the estimated vehicle position Pi(x, y) on the vehicle coordinate system into the vehicle position Qi(u, v) on the absolute coordinate system (where i=m). The absolute coordinate system has an origin at a position different from the reference position P0 of the transport vehicle 1, and has coordinate axes (u-axis, v-axis) in the directions of latitude and longitude, for example. The absolute coordinate system is, for example, a geographic coordinate system or a projected coordinate system.

[0042] Here, the vehicle position Qm(u, v) on the absolute coordinate system can be calculated using the following (Equation 4): In the following (Equation 4), the coordinates "um-1, vm-1" are the values ​​of the vehicle position Qm-1(u, v) on the absolute coordinate system at a time Δt in the past.

number

[0043] By substituting the above (Equation 2) and (Equation 3) into the above (Equation 4), the following (Equation 5) can be calculated, which converts the vehicle position Pm(x, y) into the vehicle position Qm(u, v) on the absolute coordinate system.

[0044]

number

[0045] In S15, the autonomous driving controller 11 calculates a command value for autonomous driving using the estimated vehicle position Qm(u,v) on the absolute coordinate system. In this embodiment, the command value for autonomous driving is calculated using the estimated vehicle position Qm(u,v), the coordinates of the node to be passed next indicated by the command information, and various parameters. For example, the autonomous driving controller 11 calculates a speed command value and a steering command value from the converted vehicle position Qm(u,v) taking into consideration the distance and direction to the node to be passed next, the vehicle speed specified by the route to be traveled, the specified vehicle direction, and the curvature of the route. Note that the method for calculating the command values ​​calculated in S15 is well known, so a description thereof will be omitted.

[0046] In S16, the autonomous driving controller 11 transmits the calculated command values ​​to the traveling PLC 10. As a result, the traveling PLC 10 controls the driving of the traveling motor 12 and the steering motor 13 in accordance with the command values, and causes the transport vehicle 1 to autonomously travel toward the next node to be passed. In this embodiment, the autonomous driving controller 11 realizes a traveling control unit by the processes executed in S15 and S16. Note that the steering device 7 is not limited to a combination of a steering motor and a reducer, and may be one that uses a hydraulic cylinder, for example. In this case, the traveling PLC 10 may be configured to control the hydraulic cylinder in accordance with the command values.

[0047] Although not shown in Fig. 4, when the autonomous driving controller 11 determines that it has arrived at the node specified in the command information, it transmits a completion signal indicating that it has arrived at the node to the external device via the communication IF 17. When the external device receives the completion signal, it generates command information including information specifying a new node and transmits it to the transport vehicle 1. Note that instead of determining that the external device has arrived at the node specified in the command information, the autonomous driving controller 11 may determine that it has arrived at the node specified in the command information.

[0048] In S17, the autonomous driving controller 11 determines whether or not the termination condition for the autonomous driving mode is met. The termination condition for the autonomous driving mode is, for example, when the autonomous driving controller 11 determines that the transport vehicle 1 has reached the final destination among the nodes specified in the command information transmitted from an external device, or when the autonomous driving controller 11 receives an instruction to switch the travel mode from the autonomous driving mode to the driving travel mode. If the autonomous driving controller 11 determines that the termination condition for the autonomous driving mode is not met (S17: NO), the process returns to S10, and the series of processes from S10 to S16 described above are executed to cause the transport vehicle 1 to travel autonomously. Thereafter, if the autonomous driving controller 11 determines that the termination condition for the autonomous driving mode is met (S17: YES), the process shown in FIG. 4 is terminated.

[0049] The present embodiment described above can achieve the following effects. The autonomous driving controller 11 calculates the average steering angle δavg of the wheels 21 of the multiple traveling devices 6A, 6B, 6G, and 6H, and estimates the current vehicle position Qm(u, v) based on the calculated average steering angle δavg and the vehicle speed V. The autonomous driving controller 11 calculates command values ​​for controlling the drive of each traveling device 6A-6H and each steering device 7A-7H based on the estimated vehicle position Qm(u, v), and outputs them to the traveling PLC 10. This makes it possible to accurately estimate the current vehicle position even when there is little change in the direction of the vehicle and the transport vehicle 1 is traveling with its traveling direction facing in a direction different from the vehicle's actual direction. Furthermore, by using the average value of the steering angle δ of the wheels 21, even if there is variation in the actual steering angle δ of the wheels 21 of the traveling devices 6A-6H, it is possible to suppress the influence of a decrease in the calculation accuracy of the traveling direction due to variation.

[0050] The autonomous driving controller 11 (average steering angle calculation unit) calculates the average steering angle δavg from the steering angle δ of the wheels 21 of the pair of traveling devices 6A, 6B arranged side by side in the vehicle left-right direction D2. Because the traveling direction of the vehicle is a direction according to the average steering angle δavg of the wheels 21 of the pair of traveling devices 6 arranged side by side in the vehicle left-right direction D2, the steering angle δ of the wheels 21 of the pair of traveling devices 6A, 6B arranged side by side in the vehicle left-right direction D2 is used to calculate the average steering angle δavg.

[0051] The autonomous traveling controller 11 (average steering angle calculation unit) calculates the average steering angle δavg from the steering angles δ of the wheels 21 of the first and second traveling units 6A, 6B located in front of the midpoint M and the seventh and eighth traveling units 6G, 6H located behind the midpoint M on the vehicle body 2. As a result, by using the steering angles δ of the traveling units 6A, 6B, 6G, 6H located at a distance in the front and rear of the vehicle to calculate the average steering angle δavg, the calculation accuracy of the traveling direction of the transfer vehicle 1 can be improved.

[0052] (Second embodiment) In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated. Fig. 7 is a flowchart illustrating the specific processing procedure executed by the autonomous driving controller 11 when the transport vehicle 1 is driven in the autonomous driving mode in this embodiment. In this embodiment, the autonomous driving controller 11 has a different configuration from the first embodiment in that it switches the vehicle position calculation method depending on the driving mode in the autonomous driving mode.

[0053] In S10, the autonomous driving controller 11 acquires the current vehicle speed V detected by the vehicle speed sensor 14, as already described. In S20, the autonomous driving controller 11 refers to the driving parameters in the command information received from the external device, and determines whether or not either "diagonal driving" or "lateral driving" is specified as the driving mode of the transfer vehicle 1. Here, if the command information does not specify either the driving mode "diagonal driving" or "lateral driving" (S20: NO), the process proceeds to S21.

[0054] In S21, the autonomous driving controller 11 estimates the current (i.e., i=k) vehicle position Pk(x, y) on the vehicle coordinate system. In estimating the vehicle position in S21, first, coordinates x, y on the vehicle coordinate system are calculated by a well-known vehicle position estimation calculation using the vehicle speed V and vehicle orientation θ at time "k". For example, the current vehicle position Pk(x, y) can be estimated using a well-known Kalman filter. Furthermore, the vehicle orientation θ can be calculated using the following (Equation 6) using the angular velocity ω detected by the gyro sensor 15. Here, "θk" is the vehicle orientation at time "k", and "ωk" is the previous angular velocity at time "k-1", i.e., Δt before time "k". "θk-1" is the vehicle orientation at time "k-1". θk = ωk×Δt+θk-1 … (Formula 6)

[0055] In S22, the autonomous driving controller 11 converts the calculated vehicle position Pk(x, y) into a vehicle position Qk(u, v) on the absolute coordinate system. In this embodiment, the vehicle position Pk(x, y) on the vehicle coordinate system is converted into a vehicle position Qk(u, v) on the absolute coordinate system using a rotation vector according to the vehicle orientation θk shown in the following (Equation 7). The coordinates "uk-1, vk-1" are the values ​​of the vehicle position Qk-1(u, v) on the absolute coordinate system at a time Δt in the past before time k.

number

[0056] In addition, when the transport vehicle 1 is equipped with external sensors such as a camera or radar sensor, the autonomous driving controller 11 may detect the distance and direction to surrounding landmarks using the external sensors in addition to the vehicle speed V and vehicle direction θ described above, and estimate the vehicle position Pk(x, y) and Qk(u, v) using the detected distance to the landmark. The autonomous driving controller 11 may detect Pk-n(x, y) and Qk-n(u, v) using a well-known GNSS (an abbreviation for Global Navigation Satellite System) and calculate Pk(x, y) and Qk(u, v) using the detected values ​​and the estimation method of this embodiment. Note that "n" is any natural number.

[0057] On the other hand, if the driving mode "diagonal driving" or "lateral driving" is specified by the driving parameters included in the command information received from the external device (S20: YES), the autonomous driving controller 11 proceeds to S11. As already explained, in S11, the autonomous driving controller 11 acquires the steering angles δA, δB, δG, and δH of each of the driving devices 6A, 6B, 6G, and 6H detected by the steering angle sensor 16. As already explained, in S12, the autonomous driving controller 11 calculates the average steering angle δavg from each of the acquired steering angles δ. Note that a specific method for calculating the average steering angle δavg has already been explained above using (Equation 1).

[0058] In S13, the autonomous driving controller 11 estimates the vehicle position Pm(x, y) on the vehicle coordinate system using the current vehicle speed Vm and the calculated average steering angle δavg, as already explained. Note that a specific method for calculating the vehicle position Pm(x, y) has already been explained using the above (Equation 2) and (Equation 3).

[0059] As already explained, in S14, the autonomous driving controller 11 converts the estimated vehicle position Pm(x, y) on the vehicle coordinate system into the vehicle position Qm(u, v) on the absolute coordinate system. Note that a specific method for calculating the vehicle position Qm(u, v) has already been explained using the above (Equation 5).

[0060] Regardless of the driving mode, after calculating the vehicle position Qm(u, v) (after completing the processing in S22 or S14), the autonomous driving controller 11 calculates command values ​​for autonomous driving using the vehicle position Qm(u, v) on the absolute coordinate system in S15, and transmits the calculated command values ​​to the driving PLC 10 in S16, thereby causing the transport vehicle 1 to drive autonomously. After that, when the autonomous driving controller 11 determines that the condition for terminating the autonomous driving mode has been met (S17: YES), it terminates the processing shown in FIG.

[0061] (Other embodiments) The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit thereof, for example, the following modifications are also possible. In S11 of Figure 4, the autonomous driving controller 11 may acquire only the steering angle δ of each of the first traveling device 6A and the second traveling device 6B arranged in the left-right direction D2 of the vehicle, and calculate the average steering angle δavg using only the two steering angles acquired in S12.

[0062] The number of traveling devices 6 provided in the transfer vehicle 1 is not limited to eight, and may be, for example, four or more and less than eight, or more than eight traveling devices 6.

[0063] In the above-described embodiment, the traveling drive source is an electric motor, that is, the traveling motor 12. However, instead of this, a hydraulic motor that uses hydraulic pressure circulated by driving the engine may be used as the traveling drive source. [Explanation of symbols]

[0064] 1...Transport vehicle, 2...Vehicle body, 6...Traveling device, 7...Steering device, 10...Travel PLC, 11...Autonomous travel controller, 12...Travel motor, 13...Steering motor, 14...Vehicle speed sensor, 15...Gyro sensor, 16...Steering angle sensor, 17...Communication IF

Claims

1. a vehicle body having a loading platform; a plurality of running devices disposed on the vehicle body and having independently steerable wheels; a steering device that steers the wheels of each of the plurality of traveling devices, and a speed acquisition unit that acquires a vehicle speed, which is the speed of the transport vehicle; an average steering angle calculation unit that acquires steering angles of the wheels of the plurality of traveling devices based on the vehicle longitudinal direction and calculates an average steering angle that is an average value of the acquired steering angles of the wheels; a position estimation unit that estimates a current vehicle position of the transportation vehicle based on the calculated average steering angle and the acquired vehicle speed; a travel control unit that controls driving of the traveling device and the steering device based on the estimated current vehicle position.

2. A pair of the traveling devices are arranged side by side in the left-right direction of the vehicle on the vehicle body, The average steering angle calculation unit The transport vehicle according to claim 1 , further comprising: acquiring a steering angle of the wheels of at least each of the pair of traveling devices; and calculating an average steering angle that is an average value of the acquired steering angles of the wheels.

3. The traveling devices are arranged side by side in the vehicle front-rear direction on the vehicle body, In the vehicle body, if the midpoint is the midpoint between the traveling device arranged most forward in the vehicle longitudinal direction and the traveling device arranged most rearward, The average steering angle calculation unit 2. The transport vehicle according to claim 1, wherein the steering angles of the wheels of at least the traveling device located forward of the midpoint in the fore-and-aft direction of the vehicle and the traveling device located rearward are acquired, and an average steering angle is calculated, which is the average value of the acquired steering angles of the wheels.

4. The average steering angle calculation unit 4. The transport vehicle according to claim 3, wherein at least the steering angles of the wheels of a pair of the traveling devices that are point-symmetrical with respect to the midpoint are acquired, and an average steering angle that is an average value of the acquired steering angles of the wheels is calculated.

5. A communication interface is provided for communication with an external device. the external device transmits to the transport vehicle command information, which is information for causing the transport vehicle to autonomously travel, and includes an instruction on a travel mode of the transport vehicle; The position estimation unit The transport vehicle according to any one of claims 1 to 4, wherein when the command information includes an instruction for a driving mode in which the transport vehicle is driven with the vehicle facing in a direction different from the direction of travel, a current vehicle position of the transport vehicle is estimated based on the calculated average steering angle and the acquired vehicle speed.

6. The position estimation unit calculating a traveling direction of the transport vehicle based on the calculated average steering angle; decomposing an estimated travel distance of the transport vehicle based on the vehicle speed into a horizontal component and a vertical component according to the calculated traveling direction; 5. The transport vehicle according to claim 1, wherein a current vehicle position is estimated based on the resolved horizontal direction component and the resolved vertical direction component.

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