Multi-shaft drive steering control method and control system of intelligent transport vehicle

Abstract

The invention provides a multi-shaft driving steering control method and system for an intelligent transport vehicle, and the method comprises the steps: S1, calculating the steering characteristics of a second shaft and a third shaft according to a two-degree-of-freedom kinematics model, so as to adjust the target rotation angles of all wheels on the second shaft and the third shaft; s2, the vehicle course angle and the target wheel rotation angle serve as input quantities, the motor operation parameters on the corresponding shafts serve as disturbance quantities, the actual wheel rotation angles serve as feedback quantities, and the actual wheel rotation angles on the second shaft and the third shaft are obtained through control; and S3, the steering relation between the first shaft and the second shaft and the steering relation between the third shaft and the fourth shaft are obtained based on the Ackerman angle theorem, and steering of wheels on the first shaft and the fourth shaft is controlled according to the steering relation. According to the method, the steering relation between the second shaft and the third shaft with the driving capacity and the actual wheel rotation angle are calculated through the kinematic model, then the wheel rotation angles of the first shaft and the fourth shaft are controlled in a follow-up mode according to the Ackerman rotation angle relation, the wheel steering control precision is high, and wheel track optimization is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of vehicle engineering technology, and more specifically, to a multi-axis driving steering control method and control system for an intelligent transport vehicle. Background Art

[0002] Multi-axle intelligent transport vehicles can achieve fixed-point transportation through preset routes and are not easily disturbed by the environment. Due to their advantages such as high transportation efficiency, flexibility, management convenience and low cost, their popularization in automated production lines has gradually become a trend.

[0003] In most transportation scenarios, the activity area of ​​the transport vehicle is relatively narrow, so the dual-head driving method can avoid the problem of the transport vehicle turning around in a narrow area, so that the transport vehicle can adapt to the situation where the space size is not enough to turn around. In a dual-head driving vehicle, two drive mechanisms are set to realize the switching of the transport vehicle in two opposite driving directions. For example, multiple axles are arranged in sequence on a multi-axle intelligent transport vehicle, and wheels are provided at both ends of each axle. Among them, two axles are configured as driving steering axles, and the remaining axles are configured as steering axles without driving capability. The driving steering axle is configured with a vehicle driving mechanism to drive the vehicle forward or backward. During the driving process of the vehicle, the dual-head driving direction switching of the transport vehicle can be controlled by changing the running direction of the two driving steering axles. Each axle is configured with a steering actuator for controlling the steering of the wheels at both ends, such as a proportional valve. By controlling the steering actuator on each axle to control the deflection angle of the wheels on each axle, the steering of each axle can be controlled separately.

[0004] However, in transportation scenarios where steering is often required, it is difficult for ordinary multi-axle mechanical transport vehicles to reasonably distribute the steering driving force of each axle, and the steering control effect of intelligent transport vehicles needs to be improved. Therefore, it is worth studying to optimize the distribution of steering driving force of each steering axle of multi-axle vehicles. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a multi-axis drive steering control method and control system for an intelligent transport vehicle, which can more accurately realize the individual control of the steering of the wheels on each axle, thereby improving the trajectory control effect of the intelligent transport vehicle.

[0006] According to a first aspect of the present invention, a multi-axis driving steering control method of an intelligent transport vehicle is provided, wherein the intelligent transport vehicle comprises a first axis, a second axis, a third axis and a fourth axis arranged in sequence, wherein the first axis and the fourth axis are configured as steering axes, the second axis and the third axis are configured as driving steering axes, each axis is configured with a steering actuator for controlling steering, and the second axis and the third axis are respectively configured with a driving mechanism; the control method comprises: S1, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculating the steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting the initial target turning angle of each wheel on the second axis and the third axis as the wheel target turning angle according to the steering characteristics; S2, for any wheel on the second and third axes, the target heading angle of the vehicle and the target turning angle of the wheel are used as input quantities, the operating parameters of the driving mechanism on the corresponding axis are used as disturbance quantities, and the actual turning angle of the wheel is used as feedback quantity to control the steering of the wheel on the corresponding axis; all wheels on the second and third axes are traversed to obtain the actual turning angle of each wheel on the second and third axes; S3, based on the Ackermann angle theorem, obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis, and control the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship.

[0007] Based on the above technical solution, the present invention can also make the following improvements.

[0008] Optionally, step S2 further includes: A planned trajectory of the vehicle is obtained based on the steering instruction, a tangent of the planned trajectory is used as a target heading of the vehicle, and a target heading angle of the vehicle is calculated according to the target heading of the vehicle.

[0009] Optionally, step S1 includes: S101, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, wherein the kinematic model can be expressed as the following state space equation:

[0010]

[0011]

[0012] in, is the wheelbase between the second and third axles, is the vertical distance of the center of rotation relative to the second axis, is the vertical distance of the center of rotation relative to the second axis, is the deflection stiffness of the wheels on the second axle, is the deflection stiffness of the third axle wheel, is the vehicle yaw rate, is the vehicle's sideslip angle, is the front wheel turning angle, is the vehicle mass, is the moment of inertia of the vehicle about the Z axis, is the vehicle's speed in the X direction; According to the state space equation, the following relationship between the front wheel angle, the vehicle yaw rate and the steering characteristics is obtained:

[0013] in, is the vehicle yaw rate at adjacent sampling moments The difference between S102, continuously determining the current steering characteristic according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristic; If the current steering characteristic is determined to be neutral steering, the current wheel angle is used as the wheel target angle; If the current steering characteristic is determined to be understeering, the steering angle of the wheel is increased until it is determined to be neutral steering; If the current steering characteristic is determined to be oversteering, the steering angle of the wheel is reduced until it is determined to be neutral steering.

[0014] Optionally, step S2 includes: A speed / angle adjustment control system is constructed for each wheel of the second axle and the third axle respectively; The input quantity of each speed / angle regulating control system includes the target heading angle of the vehicle, the target wheel angle and the collected actual wheel angle; the disturbance quantity of the speed / angle regulating control system includes the operating parameters of the drive mechanism on the shaft corresponding to the current wheel; the operating parameters of the drive mechanism include the torque of the drive motor and the speed of the drive motor; the output quantity of the speed / angle regulating control system is the control parameter of the steering actuator on the shaft corresponding to the current wheel; Get the actual wheel steering angle of each wheel of the second axle and the third axle.

[0015] Optionally, in step S3, the steering relationship between the first axis and the second axis obtained based on the Ackerman angle theorem is as shown in the following formula: , in, is the target turning angle of the inner wheel of the first axis, is the actual turning angle of the inner wheel of the second axis, L1 is the wheelbase from the first axis to the second axis, L2 is the vertical distance from the center of rotation to the second axis, and L1+L2 is equal to the vertical distance from the center of rotation to the first axis.

[0016] Optionally, in step S3, the steering relationship between the third axis and the fourth axis obtained based on the Ackerman angle theorem is as shown in the following formula: , in, is the target turning angle of the inner wheel of the fourth axis, is the actual turning angle of the inner wheel of the third axis, L4 is the wheelbase from the third axis to the fourth axis, L3 is the vertical distance from the center of rotation to the third axis, and L3+L4 is equal to the vertical distance from the center of rotation to the fourth axis.

[0017] Optionally, in step S3, the following control of the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship includes: The calculated inner wheel target angle of the first axis As input, the actual turning angle of the inner wheel of the first axis is collected as feedback, and the control parameters of the steering actuator on the first axis are adjusted through the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the first axis; The calculated inner wheel target angle of the fourth axis As the input quantity, the actual turning angle of the inner wheel of the fourth axis is collected as the feedback quantity, and the control parameters of the steering actuator on the fourth axis are adjusted by the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the fourth axis.

[0018] According to a second aspect of the present invention, a multi-axis driving steering control system for an intelligent transport vehicle is provided, comprising: a model building module, configured to build a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculate the steering characteristics of the second axis and the third axis according to the kinematic model, and adjust the initial target turning angle of each wheel on the second axis and the third axis to the target turning angle of the wheel according to the steering characteristics; The first control module is used for controlling the steering of the wheel on the corresponding axis by taking the target heading angle of the vehicle and the target turning angle of the wheel as input quantities, the operating parameters of the driving mechanism on the corresponding axis as the disturbance quantity, and the actual turning angle of the wheel as the feedback quantity for any wheel on the second axis and the third axis; and is also used for traversing all the wheels on the second axis and the third axis to obtain the actual turning angle of each wheel on the second axis and the third axis; The second control module is used to obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis based on the Ackerman angle theorem, and to control the steering of the wheels on the first axis and the fourth axis according to the steering relationship.

[0019] According to a third aspect of the present invention, there is provided an electronic device comprising a memory and a processor, wherein the processor is used to implement the steps of the multi-axis drive steering control method of the above-mentioned intelligent transport vehicle when executing a computer management program stored in the memory.

[0020] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium on which a computer management program is stored, and when the computer management program is executed by a processor, the steps of the multi-axis drive steering control method of the above-mentioned intelligent transport vehicle are implemented.

[0021] The present invention provides a multi-axis driving steering control method, system, electronic device and storage medium for an intelligent transport vehicle, which is based on the idea of ​​individual control of each axle wheel and coordinated control of multiple axle wheels. Since the second axle and the third axle have driving capabilities and provide driving power for vehicle travel, the operation model of the second axle and the third axle is first constructed based on a two-degree-of-freedom model, and the steering relationship between the second axle and the third axle with driving capabilities is calculated through the kinematic model of the second axle and the third axle, and the initial target turning angle of the wheel obtained according to the vehicle steering instruction is corrected based on the steering relationship to obtain a more accurate target turning angle of the wheel; then the target turning angle of the wheel and the target heading angle of the vehicle are used as input quantities to perform closed-loop control on the steering angle of each wheel of the second axle and the third axle, and the operating parameters (such as torque and speed) of the motor corresponding to the second axle or the third axle are used as the disturbance quantity (feedforward quantity) of the closed-loop control process, and the actual turning angle of each wheel is detected by the sensor in real time as the feedback quantity, so as to obtain a more accurate actual turning angle of each wheel after closed-loop control. After obtaining the control amount of the wheel corresponding to the second axis or the third axis, the wheels of the first axis and the fourth axis are controlled by follow-up control through the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis. The control method of the present invention realizes accurate output of tire steering under different driving force distribution, improves the multi-axis driving steering control accuracy of the intelligent transport vehicle, and provides a more flexible and efficient implementation plan for route planning optimization of the intelligent transport vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a multi-axle arrangement of an intelligent transport vehicle applicable to the method of the present invention; Figure 2 A schematic diagram of the steering linkage structure of wheels on both sides of a single axle in a certain embodiment; Figure 3 A flow chart of a multi-axis driving steering control method for an intelligent transport vehicle provided by the present invention; Figure 4 is a schematic diagram of a kinematic model about the second axis and the third axis in a certain embodiment; Figure 5 A schematic diagram of the relationship between the planned trajectory, the actual heading and the target heading in an understeering condition in a certain embodiment; Figure 6 is a schematic diagram of steering control for the second axis and the third axis in a certain embodiment; Figure 7 A schematic diagram of a kinematic model of a first axis and a second axis in a certain embodiment; Figure 8 is a schematic diagram of steering control for a first axis and a fourth axis in a certain embodiment; Fig. 9A block diagram of a multi-axis driving and steering control system for an intelligent transport vehicle provided by the present invention; Fig.10 A schematic diagram of the hardware structure of a possible electronic device provided by the present invention; Fig.11 A schematic diagram of the hardware structure of a possible computer-readable storage medium provided by the present invention. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0024] like Figure 1 Shown is a schematic diagram of multi-axis distribution of an intelligent transport vehicle involved in a multi-axis drive steering control method of an intelligent transport vehicle provided by the present invention.

[0025] like Figure 1 As shown, the intelligent transport vehicle includes four shafts (first to fourth shafts) arranged on the frame in sequence, wherein the first and fourth shafts are configured as steering shafts, and the second and third shafts are configured as driving steering shafts. The motor is connected to the driving steering axle (driving steering shaft) through a transmission shaft, driving the wheels at both ends of the axle to rotate circumferentially, thereby controlling the driving of the wheels. For example, the motor motor1 is connected to the second shaft through a transmission shaft, and the second shaft can drive the vehicle forward or backward under the driving action of the motor motor1; the motor motor2 is connected to the third shaft through another transmission shaft, and the third shaft can drive the vehicle forward or backward under the driving action of the motor motor2. The running direction of the motor motor1 and the motor motor2 is switched, and the driving direction of the vehicle can be switched to realize two-way driving of the vehicle.

[0026] Each of the first to fourth axes is provided with a steering actuator for controlling the steering, and the steering control principle of the steering actuator is the prior art. Figure 2 The figure shows the steering control principle of the wheels at both ends of a single axle. The hydraulic station provides hydraulic power to drive the steering cylinder to extend and retract, driving the steering knuckles of each axle to rotate to achieve steering. In the embodiment of the present invention, the hydraulic pressure is controlled by the electromagnetic proportional valve, and the opening size of the multi-way valve is controlled to control the flow of the hydraulic oil in the steering circuit, thereby achieving the size of the steering angle. A separate oil circuit is set on each axle for separate steering control, and the four axles steer in coordination. Figure 2The directions are shown for example. When the servo proportional valve is controlled, the servo proportional valve receives the electric control signal and changes the hydraulic oil flow ratio of its A port and B port. The flow ratio of the A port and the B port of the servo proportional valve changes, driving the linkage mechanism to drive the steering knuckle to turn, thereby adjusting the steering angle of the wheel. Since both wheel A and wheel B are controlled by the same servo proportional valve and linkage mechanism on the same axle, the steering angles of wheel A and wheel B are adjusted synchronously. The real-time steering state of the wheel can be reflected by installing an angle encoder on the steering knuckles on both sides of the axle and collecting the angle of rotation of the steering knuckle. In some cases, the steering condition of the wheel on the same axle can be reflected by detecting the steering condition of any wheel on the same axle. Angle encoders can also be installed on the steering knuckles at both ends of the axle, and the steering condition of the vehicle can be verified by collecting the steering conditions of the wheels at both ends of the axle.

[0027] Based on the above steering principle, Figure 3 As shown in the flowchart, this embodiment provides a multi-axis driving steering control method for an intelligent transport vehicle, the method comprising steps S1 to S3: S1, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculating the steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting the initial target turning angle of each wheel on the second axis and the third axis as the wheel target turning angle according to the steering characteristics; S2, for any wheel on the second and third axes, the target heading angle of the vehicle and the target turning angle of the wheel are used as input quantities, the operating parameters of the driving mechanism on the corresponding axis are used as disturbance quantities, and the actual turning angle of the wheel is used as feedback quantity to control the steering of the wheel on the corresponding axis; all wheels on the second and third axes are traversed to obtain the actual turning angle of each wheel on the second and third axes; S3, based on the Ackermann angle theorem, obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis, and control the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship.

[0028] It can be understood that, based on the defects pointed out in the background technology, this embodiment provides a multi-axis driving steering control method for an intelligent transport vehicle based on the idea of ​​controlling the wheels of each axis individually and controlling the wheels of multiple axes in coordination. Since the second axis and the third axis have driving capabilities and provide driving power for the vehicle, the kinematic model of the second axis and the third axis is first constructed based on the two-degree-of-freedom model, and the steering relationship of the second axis and the third axis with driving capabilities is calculated through the kinematic model of the second axis and the third axis. Based on the steering relationship, the initial target turning angle of the wheel obtained according to the vehicle steering instruction is corrected to obtain a more accurate target turning angle of the wheel; then, the target turning angle of the wheel and the target heading angle of the vehicle are used as input quantities to perform closed-loop control on the steering angle of each wheel of the second axis and the third axis, and the operating parameters (such as torque and speed) of the motor corresponding to the second axis or the third axis are used as the disturbance quantity (feedforward quantity) of the closed-loop control process, and the actual turning angle of each wheel is detected by the sensor in real time as the feedback quantity, so as to obtain a more accurate actual turning angle of each wheel after closed-loop control. After obtaining the control amount of the wheel corresponding to the second axis or the third axis, the wheels of the first axis and the fourth axis are controlled by follow-up control through the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis. The control method of this embodiment realizes accurate output of tire steering under different driving force distribution, improves the accuracy of multi-axis driving steering control of the intelligent transport vehicle, and provides a more flexible and efficient implementation plan for route planning optimization of the intelligent transport vehicle.

[0029] In a possible implementation manner, step S1 includes steps S101-S102: S101, construct a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, such as Figure 4 FIG. 1 is a schematic diagram of the kinematic model of the second axis and the third axis in this embodiment. Figure 4 The midpoint O is the center of rotation during the vehicle steering process. The kinematic model can be expressed as the following state space equation:

[0030]

[0031]

[0032] in, is the wheelbase between the second and third axles, is the perpendicular distance of the center of rotation O relative to the second axis, is the perpendicular distance of the center of rotation O relative to the second axis, is the deflection stiffness of the wheels on the second axle, is the deflection stiffness of the third axle wheel, is the vehicle yaw rate, is the vehicle's sideslip angle, is the front wheel turning angle, is the vehicle mass, is the moment of inertia of the vehicle about the Z axis, is the vehicle's speed in the X direction; According to the state space equation, the relationship between the front wheel angle, the vehicle yaw rate and the steering characteristics is obtained as shown in the following table:

[0033] in, is the vehicle yaw rate at adjacent sampling moments The difference between It is understandable that when studying the kinematic model, the general research idea is to ignore the tire side slip angle or regard it as a disturbance constraint within a small controllable range. For the intelligent transport vehicle described in this embodiment, the kinematic model of the second and third axes is as follows: Figure 4 In the speed / angle control system about the second and third axes, the first Figure 4 The kinematic model shown calculates the steering characteristics relationship of the second and third axes with drive capabilities.

[0034] S102, continuously determining the current steering characteristic according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristic; If the current steering characteristic is determined to be neutral steering, in this case, the vehicle's steering radius is considered to be almost equal to the ideal steering radius, and the current wheel turning angle is used as the wheel target turning angle; like Figure 5 The situation under understeering is shown. If the current steering characteristic is judged to be understeering, it is considered that the actual turning radius of the vehicle is greater than the ideal turning radius (planned trajectory). At this time, the steering angle of the wheel is increased until it is judged to be neutral steering. If the current steering characteristic is judged to be oversteering, this situation is similar to Figure 5 The opposite is true, where the actual turning radius of the vehicle is considered to be smaller than the ideal turning radius (planned trajectory). In this case, the steering angle of the wheel is reduced until it is determined to be a neutral turn.

[0035] It can be understood that after obtaining the relationship between the front wheel angle, the vehicle yaw rate and the steering characteristics, the angular velocity and angle corresponding to the second and third axes can be calculated based on the relationship according to the driving force distribution, and corresponding adjustments can be made.

[0036] In a possible implementation manner, step S2 further includes: A planned trajectory of the vehicle is obtained based on the steering instruction, a tangent of the planned trajectory is used as a target heading of the vehicle, and a target heading angle of the vehicle is calculated according to the target heading of the vehicle.

[0037] It can be understood that the heading angle is the angle between the heading and the true north direction. Figure 5 As shown in FIG. 1 , the target heading of the wheel changes with the planned trajectory of the vehicle, so the target heading angle of the vehicle is a variable value. By continuously adjusting the wheel steering, the real-time heading of the vehicle approaches the target heading of the vehicle, and the driving trajectory of the vehicle approaches the planned trajectory.

[0038] In a possible embodiment, Figure 6 The figure shows the schematic diagram of the single wheel steering control system in the second and third axes. The sliding mode control algorithm is used to design the target yaw moment control system. Figure 6 As shown, step S2 includes: For each wheel of the second and third axles, construct Figure 6 The speed / angle adjustment control system shown in the figure, that is, for the wheels at both ends of the second shaft and the wheels at both ends of the third shaft, at least four such as Figure 6 The speed / angle regulation control system shown; The input of each speed / angle control system includes the target heading angle of the vehicle, the target wheel angle, and the actual wheel angle collected by the angle encoder on each wheel. The disturbance of the speed / angle control system includes the operating parameters of the drive mechanism on the shaft corresponding to the current wheel. The operating parameters of the drive mechanism include the torque of the drive motor and the speed of the drive motor. The output of the speed / angle control system is the control parameter of the steering actuator on the shaft corresponding to the current wheel, for example Figure 2 The electric control signal of the solenoid proportional valve shown; The actual wheel rotation angle of each wheel of the second axle and the third axle is acquired respectively through the rotation angle encoders arranged on each wheel.

[0039] It can be understood that each wheel of the second axle and the third axle is controlled individually. By individually controlling the steering of the wheels at both ends of the same axle, the steering control of the wheels on the same axle can be verified, thereby improving the steering control accuracy of the wheels on the second axle and the third axle.

[0040] In one possible embodiment, Figure 7 The schematic diagram of the kinematic model of the first axis and the second axis in this embodiment is shown. Figure 7 In the model shown, the inner and outer wheel turning angles of the first axis and the inner and outer wheel turning angles of the second axis conform to the Ackerman turning angle relationship, which is expressed as follows: , in, is the target turning angle of the inner wheel of the first axis, is the actual turning angle of the inner wheel of the second axis, L1 is the wheelbase from the first axis to the second axis, L2 is the vertical distance from the rotation center O to the second axis, and L1+L2 is equal to the vertical distance from the rotation center O to the first axis.

[0041] Since the control mode of the first shaft is follow-up control, its angle control depends on the angle control of the second shaft. Therefore, in this embodiment, only the inner wheel angle of the first shaft is controlled. The inner wheel target angle of the first shaft is obtained according to the inner wheel target angle of the second shaft, and the following relationship is obtained: .

[0042] In a possible implementation manner, the steering angle control principle of the fourth axis is similar to the steering angle control principle of the first axis in the previous embodiment. In step S3, the steering relationship between the third axis and the fourth axis is obtained based on the Ackerman angle theorem, as shown in the following formula: , in, is the target turning angle of the inner wheel of the fourth axis, is the actual turning angle of the inner wheel of the third axis, L4 is the wheelbase from the third axis to the fourth axis, L3 is the vertical distance from the center of rotation to the third axis, and L3+L4 is equal to the vertical distance from the center of rotation to the fourth axis.

[0043] The target rotation angle of the inner wheel of the first axis is obtained by the above embodiment: And the inner wheel target angle of the fourth axis After that, the wheel steering on the first axle and the wheel steering on the fourth axle can be controlled, including: Construct the first axis and the fourth axis as follows Figure 8 The PID control system shown; The calculated inner wheel target angle of the first axis As the input of the PID control system, the actual turning angle of the inner wheel of the first shaft is collected as the feedback quantity, and the control parameters of the steering actuator on the first shaft are adjusted by the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the first shaft; The calculated inner wheel target angle of the fourth axis As the input of the PID control system, the actual turning angle of the inner wheel of the fourth axis is collected as the feedback quantity, and the control parameters of the steering actuator on the fourth axis are adjusted by the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the fourth axis.

[0044] It can be understood that for the angle control of the first axis and the fourth axis, the classic PID control algorithm is adopted, and the values ​​collected by the angle encoders of the first axis and the fourth axis are used as feedback to regulate the steering control servo proportional valve to achieve high-precision closed-loop control of the wheel angle.

[0045] Fig. 9 A structural diagram of a multi-axis driving steering control system for an intelligent transport vehicle provided by an embodiment of the present invention, such as Fig. 9 As shown, a multi-axis driving steering control system for an intelligent transport vehicle includes a model building module, a first control module and a second control module, wherein: a model building module, configured to build a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculate the steering characteristics of the second axis and the third axis according to the kinematic model, and adjust the initial target turning angle of each wheel on the second axis and the third axis to the target turning angle of the wheel according to the steering characteristics; The first control module is used for controlling the steering of the wheel on the corresponding axis by taking the target heading angle of the vehicle and the target turning angle of the wheel as input quantities, the operating parameters of the driving mechanism on the corresponding axis as the disturbance quantity, and the actual turning angle of the wheel as the feedback quantity for any wheel on the second axis and the third axis; and is also used for traversing all the wheels on the second axis and the third axis to obtain the actual turning angle of each wheel on the second axis and the third axis; The second control module is used to obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis based on the Ackerman angle theorem, and to control the steering of the wheels on the first axis and the fourth axis according to the steering relationship.

[0046] It can be understood that the multi-axis drive steering control system of an intelligent transport vehicle provided by the present invention corresponds to the multi-axis drive steering control method of the intelligent transport vehicle provided by the aforementioned embodiments. The relevant technical features of the multi-axis drive steering control system of the intelligent transport vehicle can refer to the relevant technical features of the multi-axis drive steering control method of the intelligent transport vehicle, which will not be repeated here.

[0047] See also Fig.10 , Fig.10 Schematic diagram of an electronic device provided by an embodiment of the present invention. Fig.10 As shown, an embodiment of the present invention provides an electronic device 1000, including a memory 1010, a processor 1020, and a computer program 1011 stored in the memory 1010 and executable on the processor 1020. When the processor 1020 executes the computer program 1011, the following steps are implemented: S1, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculating the steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting the initial target turning angle of each wheel on the second axis and the third axis as the wheel target turning angle according to the steering characteristics; S2, for any wheel on the second and third axes, the target heading angle of the vehicle and the target turning angle of the wheel are used as input quantities, the operating parameters of the driving mechanism on the corresponding axis are used as disturbance quantities, and the actual turning angle of the wheel is used as feedback quantity to control the steering of the wheel on the corresponding axis; all wheels on the second and third axes are traversed to obtain the actual turning angle of each wheel on the second and third axes; S3, based on the Ackermann angle theorem, obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis, and control the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship.

[0048] See also Fig.11 , Fig.11 Schematic diagram of an embodiment of a computer-readable storage medium provided by the present invention. Fig.11 As shown, this embodiment provides a computer-readable storage medium 1100, on which a computer program 1111 is stored. When the computer program 1111 is executed by a processor, the following steps are implemented: S1, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculating the steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting the initial target turning angle of each wheel on the second axis and the third axis as the wheel target turning angle according to the steering characteristics; S2, for any wheel on the second and third axes, the target heading angle of the vehicle and the target turning angle of the wheel are used as input quantities, the operating parameters of the driving mechanism on the corresponding axis are used as disturbance quantities, and the actual turning angle of the wheel is used as feedback quantity to control the steering of the wheel on the corresponding axis; all wheels on the second and third axes are traversed to obtain the actual turning angle of each wheel on the second and third axes; S3, based on the Ackermann angle theorem, obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis, and control the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship.

[0049] The embodiment of the present invention provides a multi-axis driving steering control method, system and storage medium for an intelligent transport vehicle. Based on the existing chassis technology and suspension technology, the steering unit and the driving unit are improved. The flow of hydraulic oil in the steering circuit of each axis is controlled by controlling the opening size of the multi-way servo proportional valve, so as to achieve the adjustment of the size of the steering angle of each axis. A separate oil circuit is set on each axis for separate steering control. The four steering axes steer in coordination, giving priority to the steering relationship between the second and third axes with driving capacity, and then regulating the steering angle of the first and fourth axes with the coordinated steering relationship of multiple axes. Specifically, the intelligent transport vehicle uses wire control technology, takes the vehicle heading angle and wheel angle as the target control quantity, controls the angle and speed of each tire of the second and third axes, and uses an independent steering control unit composed of a steering servo proportional valve and a linkage mechanism to achieve independent control of the wheel angle of each axis. At the same time, the driving torque signal of two independently driven DC motors is combined as a feedforward quantity, and high-precision angle sensors are installed on each tire of the second and third axes to collect the actual wheel angle in real time. The control system can control the steering servo proportional valve according to the actual wheel angle feedback signal of the sensor, thereby achieving accurate output of tire steering under different driving force distribution.

[0050] The present invention realizes accurate output of tire steering under different driving force distributions, improves the multi-axis drive steering control accuracy of the intelligent transport vehicle, and provides a more flexible and efficient implementation plan for route planning optimization of the intelligent transport vehicle.

[0051] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0052] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0053] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0054] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0055] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0056] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0057] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-axis driving steering control method for an intelligent transport vehicle, characterized in that: The intelligent transport vehicle comprises a first shaft, a second shaft, a third shaft and a fourth shaft which are arranged in sequence, wherein the first shaft and the fourth shaft are configured as steering shafts, the second shaft and the third shaft are configured as driving steering shafts, each shaft is configured with a steering actuator for controlling steering, and the second shaft and the third shaft are respectively configured with a driving mechanism; the control method comprises: S1, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculating the steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting the initial target turning angle of each wheel on the second axis and the third axis as the wheel target turning angle according to the steering characteristics; S2, for any wheel on the second and third axes, the target heading angle of the vehicle and the target turning angle of the wheel are used as input quantities, the operating parameters of the driving mechanism on the corresponding axis are used as disturbance quantities, and the actual turning angle of the wheel is used as feedback quantity to control the steering of the wheel on the corresponding axis; all wheels on the second and third axes are traversed to obtain the actual turning angle of each wheel on the second and third axes; S3, based on the Ackermann angle theorem, obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis, and control the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship.

2. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 1, characterized in that: Step S2 also includes: A planned trajectory of the vehicle is obtained based on the steering instruction, a tangent of the planned trajectory is used as a target heading of the vehicle, and a target heading angle of the vehicle is calculated according to the target heading of the vehicle.

3. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 1, characterized in that: Step S1 includes: S101, constructing a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, wherein the kinematic model can be expressed as the following state space equation: in, is the wheelbase between the second and third axles, is the vertical distance of the center of rotation relative to the second axis, is the vertical distance of the center of rotation relative to the second axis, is the deflection stiffness of the wheels on the second axle, is the deflection stiffness of the third axle wheel, is the vehicle yaw rate, is the vehicle's sideslip angle, is the front wheel turning angle, is the vehicle mass, is the moment of inertia of the vehicle about the Z axis, is the vehicle's speed in the X direction; According to the state space equation, the following relationship between the front wheel angle, the vehicle yaw rate and the steering characteristics is obtained: in, is the vehicle yaw rate at adjacent sampling moments The difference between S102, continuously determining the current steering characteristic according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristic; If the current steering characteristic is determined to be neutral steering, the current wheel angle is used as the wheel target angle; If the current steering characteristic is determined to be understeering, the steering angle of the wheel is increased until it is determined to be neutral steering; If the current steering characteristic is determined to be oversteering, the steering angle of the wheel is reduced until it is determined to be neutral steering.

4. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 1, characterized in that: Step S2 comprises: A speed / angle adjustment control system is constructed for each wheel of the second axle and the third axle respectively; The input quantity of each speed / angle regulating control system includes the target heading angle of the vehicle, the target wheel angle and the collected actual wheel angle; the disturbance quantity of the speed / angle regulating control system includes the operating parameters of the drive mechanism on the shaft corresponding to the current wheel; the operating parameters of the drive mechanism include the torque of the drive motor and the speed of the drive motor; the output quantity of the speed / angle regulating control system is the control parameter of the steering actuator on the shaft corresponding to the current wheel; Get the actual wheel angle of each wheel of the second axis and the third axis.

5. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 1, characterized in that: In step S3, the steering relationship between the first axis and the second axis is obtained based on the Ackerman angle theorem, as shown in the following formula: ， in, is the target turning angle of the inner wheel of the first axis, is the actual turning angle of the inner wheel of the second axis, L1 is the wheelbase from the first axis to the second axis, L2 is the vertical distance from the center of rotation to the second axis, and L1+L2 is equal to the vertical distance from the center of rotation to the first axis.

6. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 5, characterized in that: In step S3, the steering relationship between the third axis and the fourth axis is obtained based on the Ackerman angle theorem, as shown in the following formula: ， in, is the target turning angle of the inner wheel of the fourth axis, is the actual turning angle of the inner wheel of the third axis, L4 is the wheelbase from the third axis to the fourth axis, L3 is the vertical distance from the center of rotation to the third axis, and L3+L4 is equal to the vertical distance from the center of rotation to the fourth axis.

7. The multi-axis driving steering control method of an intelligent transport vehicle according to claim 6, characterized in that: In step S3, the following control of the steering of the wheels on the first axis and the steering of the wheels on the fourth axis according to the steering relationship includes: The calculated inner wheel target angle of the first axis As input, the actual turning angle of the inner wheel of the first axis is collected as feedback, and the control parameters of the steering actuator on the first axis are adjusted through the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the first axis; The calculated inner wheel target angle of the fourth axis As the input quantity, the actual turning angle of the inner wheel of the fourth axis is collected as the feedback quantity, and the control parameters of the steering actuator on the fourth axis are adjusted by the PID algorithm to obtain the adjusted actual turning angle of the inner wheel of the fourth axis.

8. A multi-axis driving steering control system for an intelligent transport vehicle, characterized in that: Based on the method described in any one of claims 1 to 7, the system comprises: a model building module, configured to build a kinematic model about the second axis and the third axis based on the two-degree-of-freedom model, calculate the steering characteristics of the second axis and the third axis according to the kinematic model, and adjust the initial target turning angle of each wheel on the second axis and the third axis to the target turning angle of the wheel according to the steering characteristics; The first control module is used for controlling the steering of the wheel on the corresponding axis by taking the target heading angle of the vehicle and the target turning angle of the wheel as input quantities, the operating parameters of the driving mechanism on the corresponding axis as the disturbance quantity, and the actual turning angle of the wheel as the feedback quantity for any wheel on the second axis and the third axis; and is also used for traversing all the wheels on the second axis and the third axis to obtain the actual turning angle of each wheel on the second axis and the third axis; The second control module is used to obtain the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis based on the Ackerman angle theorem, and to control the steering of the wheels on the first axis and the fourth axis according to the steering relationship.

9. An electronic device, characterized in that: It includes a memory and a processor, and the processor is used to implement the steps of the multi-axis drive steering control method of the intelligent transport vehicle as described in any one of claims 1 to 7 when executing the computer management program stored in the memory.

10. A computer-readable storage medium, characterized in that: A computer management program is stored thereon, and when the computer management program is executed by the processor, the steps of the multi-axis drive steering control method of the intelligent transport vehicle as described in any one of claims 1-7 are implemented.

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