Multi-axle driving and steering control method and control system of intelligent transport vehicle

Abstract

The application provides a multi-axle driving steering control method and control system of an intelligent transport vehicle, which comprises the following steps: S1, calculating steering characteristics of a second axle and a third axle according to a two-degree-of-freedom kinematic model, so as to adjust target steering angles of each wheel on the second axle and the third axle; S2, taking a vehicle heading angle and the wheel target steering angle as input, taking motor operating parameters on the corresponding axle as disturbance, and taking actual wheel steering angles as feedback, so as to control the actual wheel steering angles on the second axle and the third axle; and S3, obtaining steering relationships of the first axle and the second axle and steering relationships of the third axle and the fourth axle based on the Ackerman steering angle theorem, and controlling the wheel steering of the first axle and the fourth axle according to the steering relationships. The application calculates the steering relationships of the second axle and the third axle with driving capability and the actual wheel steering angles through a kinematic model, and then controls the wheel steering angles of the first axle and the fourth axle according to the Ackerman steering angle relationship, so that the wheel steering control precision is high and the wheel trajectory optimization is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle engineering, and more particularly to a multi-axle driving steering control method and system for an intelligent transport vehicle. BACKGROUND

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

[0003] In most transportation scenarios, the activity field of the transport vehicle is relatively narrow, so the double-head driving mode can avoid the problem of turning around in a narrow field, allowing the transport vehicle to adapt to situations where the space size is insufficient for turning around. In a double-head driving vehicle, two driving mechanisms are provided to achieve switching of the transport vehicle in two opposite driving directions. For example, a plurality of shafts are sequentially provided on a multi-axle intelligent transport vehicle, and wheels are provided at both ends of each shaft. Among them, two shafts are configured as driving steering shafts, and the remaining shafts are configured as steering shafts without driving capability. The driving steering shafts are configured with a vehicle driving mechanism to drive the vehicle to move forward or backward. During vehicle driving, the driving direction of the two driving steering bridges can be changed to control the switching of the driving direction of the transport vehicle. A steering execution mechanism, such as a proportional valve, is provided on each shaft to control the steering of the wheels at both ends. By controlling the steering execution mechanism on each shaft, the deflection angle of the wheels on each shaft can be controlled to achieve individual control of the steering of the wheels on each shaft.

[0004] However, in transportation scenarios that often require steering, ordinary multi-axle mechanical transport vehicles have difficulty in reasonably distributing the steering driving force of each shaft, and the steering control effect of intelligent transport vehicles needs to be improved. Therefore, it is worth studying the optimization of the steering driving force distribution of each steering bridge of a multi-axle vehicle. SUMMARY

[0005] The present application provides a multi-axle driving steering control method and system for an intelligent transport vehicle, which more accurately achieves individual control of the steering of the wheels on each shaft and improves the trajectory control effect of the intelligent transport vehicle.

[0006] According to a first aspect of the present application, a multi-axle driving steering control method for an intelligent transport vehicle is provided, wherein the intelligent transport vehicle includes a first shaft, a second shaft, a third shaft, and a fourth shaft sequentially arranged, wherein the first shaft and the fourth shaft are configured as steering shafts, and the second shaft and the third shaft are configured as driving steering shafts, each shaft is configured with a steering execution mechanism for controlling steering, and the second shaft and the third shaft are respectively configured with a driving mechanism; the control method comprises:

[0007] S1, constructing a kinematic model about the second axis and the third axis based on a two-degree-of-freedom model, calculating steering characteristics of the second axis and the third axis according to the kinematic model, and adjusting initial target steering angles of each wheel on the second axis and the third axis to wheel target steering angles according to the steering characteristics;

[0008] S2, for any wheel on the second axis and the third axis, taking a target heading angle of the vehicle and the wheel target steering angle as input quantities, taking a running parameter of a driving mechanism on the corresponding axis as a disturbance quantity, and taking an actual wheel steering angle as a feedback quantity, controlling wheel steering on the corresponding axis; and traversing all wheels on the second axis and the third axis to obtain actual wheel steering angles of each wheel on the second axis and the third axis.

[0009] S3, obtaining a steering relationship between the first axis and the second axis and a steering relationship between the third axis and the fourth axis based on the Ackerman steering theorem, and servo-controlling wheel steering on the first axis and wheel steering on the fourth axis according to the steering relationships.

[0010] On the basis of the above technical solution, the application can also be improved as follows.

[0011] Optionally, step S2 further comprises:

[0012] acquiring a planned trajectory of vehicle driving based on a steering instruction, taking a tangent of the planned trajectory as a target heading of the vehicle, and calculating a target heading angle of the vehicle according to the target heading of the vehicle.

[0013] Optionally, step S1 comprises:

[0014] S101, constructing a kinematic model about the second axis and the third axis based on a two-degree-of-freedom model, and the kinematic model can be expressed as a state space equation as follows:

[0015]

[0016]

[0017]

[0018] wherein, is a wheelbase between the second axis and the third axis, is a perpendicular distance of a turning center relative to the second axis, is a perpendicular distance of a turning center relative to the second axis, is a deflection stiffness of a wheel on the second axis, is a deflection stiffness of a wheel on the third axis, is a vehicle yaw rate, is a vehicle side slip angle, is a front wheel steering angle, is a vehicle mass, is the moment of inertia of the vehicle about the Z axis, is the velocity of the vehicle in the X direction;

[0019] According to the state space equation, the following relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristic is obtained:

[0020]

[0021] wherein, is the difference of the vehicle yaw rate at adjacent sampling time points;

[0022] S102, continuously judging the current steering characteristic according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristic;

[0023] If it is determined that the current steering characteristic is neutral steering, the current wheel steering angle is taken as the wheel target steering angle;

[0024] If it is determined that the current steering characteristic is under-steering, the steering angle of the wheel is increased until it is determined to be neutral steering;

[0025] If it is determined that the current steering characteristic is over-steering, the steering angle of the wheel is reduced until it is determined to be neutral steering.

[0026] Optionally, step S2 comprises:

[0027] A rotational speed / angle adjustment control system is constructed for each wheel of the second and third axles respectively;

[0028] The input quantity of each rotational speed / angle adjustment control system comprises the target heading angle of the vehicle, the wheel target steering angle and the actual wheel steering angle collected, the disturbance quantity of the rotational speed / angle adjustment control system comprises the operating parameter of the driving mechanism on the corresponding axle of the current wheel, the operating parameter of the driving mechanism comprises the torque of the driving motor and the rotational speed of the driving motor, and the output quantity of the rotational speed / angle adjustment control system is the control parameter of the steering execution mechanism on the corresponding axle of the current wheel;

[0029] The actual wheel steering angle of each wheel of the second and third axles is obtained.

[0030] Optionally, in step S3, the steering relationship between the first and second axles obtained based on the Ackermann steering theorem is as follows:

[0031] ,

[0032] wherein, is the target steering angle of the inner wheel of the first axle, is the actual turning angle of the inner wheel of the second axle, L1 is the wheelbase from the first axle to the second axle, L2 is the vertical distance from the rotation center to the second axle, and L1+L2 is equal to the vertical distance from the rotation center to the first axle.

[0033] Optionally, in step S3, the steering relationship between the third axle and the fourth axle obtained based on the Ackerman turning angle theorem is as follows:

[0034] ,

[0035] wherein, is the target turning angle of the inner wheel of the fourth axle, is the actual turning angle of the inner wheel of the third axle, L4 is the wheelbase from the third axle to the fourth axle, and L3 is the vertical distance from the rotation center to the third axle, and L3+L4 is equal to the vertical distance from the rotation center to the fourth axle.

[0036] Optionally, in step S3, the servo control of the wheels on the first axle and the wheels on the fourth axle according to the steering relationship comprises:

[0037] the calculated target turning angle of the inner wheel of the first axle is taken as an input quantity, the actual turning angle of the inner wheel of the first axle is taken as a feedback quantity, the control parameters of the steering actuator on the first axle are adjusted through a PID algorithm, and the adjusted actual turning angle of the inner wheel of the first axle is obtained.

[0038] the calculated target turning angle of the inner wheel of the fourth axle is taken as an input quantity, the actual turning angle of the inner wheel of the fourth axle is taken as a feedback quantity, the control parameters of the steering actuator on the fourth axle are adjusted through a PID algorithm, and the adjusted actual turning angle of the inner wheel of the fourth axle is obtained.

[0039] According to the second aspect of the present application, a multi-axle driving and steering control system of an intelligent transport vehicle is provided, comprising:

[0040] a model construction module, configured to construct a kinematic model about the second axle and the third axle based on a two-degree-of-freedom model, calculate steering characteristics of the second axle and the third axle according to the kinematic model, and adjust initial target turning angles of each wheel on the second axle and the third axle to wheel target turning angles according to the steering characteristics;

[0041] a first control module, configured to, for any wheel on the second axle and the third axle, take a target heading angle of the vehicle and the wheel target turning angle as input quantities, take a running parameter of a driving mechanism on a corresponding axle as a disturbance quantity, and take an actual turning angle of the wheel as a feedback quantity, to control the wheel steering on the corresponding axle, and further configured to traverse all the wheels on the second axle and the third axle to obtain actual turning angles of the wheels on the second axle and the third axle;

[0042] A second control module is configured to obtain steering relationships of the first and second shafts and steering relationships of the third and fourth shafts based on Ackerman steering theorem, and to servo-control steering of the wheels on the first shaft and steering of the wheels on the fourth shaft according to the steering relationships.

[0043] According to a third aspect of the present application, an electronic device is provided, comprising a memory and a processor configured to implement the steps of the multi-axle drive steering control method of the intelligent transport vehicle when executing a computer management program stored in the memory.

[0044] According to a fourth aspect of the present application, a computer readable storage medium is provided, having a computer management program stored thereon, the computer management program being configured to implement the steps of the multi-axle drive steering control method of the intelligent transport vehicle when executed by a processor.

[0045] The multi-axle drive steering control method, system, electronic device and storage medium of the intelligent transport vehicle provided by the present application are based on the ideas of individual control of each axle wheel and cooperative control of multiple axle wheels. Since the second and third shafts have driving capability, they provide driving power for vehicle travel. Therefore, a kinematic model of the second and third shafts is first constructed based on a two-degree-of-freedom model, the steering relationships of the second and third shafts with driving capability are calculated through the kinematic model of the second and third shafts, the initial target steering angle of the wheels obtained according to the vehicle steering instruction is corrected based on the steering relationships to obtain more accurate target steering angles of the wheels, then the target steering angles of the wheels and the target heading angle of the vehicle are used as input quantities to respectively close-loop control the steering angles of each wheel of the second and third shafts, and the operating parameters (such as torque and speed) of the motor corresponding to the second or third shaft are used as the disturbance quantity (feedforward quantity) of the closed-loop control process, and the real-time actual steering angles of each wheel are detected by a sensor as feedback quantities, so that more accurate actual steering angles of each wheel after closed-loop control are obtained. After obtaining the control quantity of the wheel corresponding to the second or third shaft, the wheels of the first and fourth shafts are controlled in a servo-control manner through the steering relationships of the first and second shafts and the steering relationships of the third and fourth shafts. The control method of the present application realizes accurate output of tire steering under different driving force distribution, improves the multi-axle drive steering control accuracy of the intelligent transport vehicle, and provides a more flexible and efficient implementation scheme for route planning optimization of the intelligent transport vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 A multi-axle arrangement of an intelligent transport vehicle suitable for the method of the present application;

[0047] Figure 2 A steering linkage structure of the wheels on both sides of a single axle in an embodiment;

[0048] Figure 3A multi-axle driving steering control method flow chart of an intelligent transport vehicle provided by the present application;

[0049] Figure 4 A kinematic model schematic diagram about the second axis and the third axis in an embodiment;

[0050] Figure 5 A relationship schematic diagram of the planned trajectory, the actual heading and the target heading in the insufficient steering condition in an embodiment;

[0051] Figure 6 A steering control principle diagram about the second axis and the third axis in an embodiment;

[0052] Figure 7 A kinematic model schematic diagram about the first axis and the second axis in an embodiment;

[0053] Figure 8 A steering control principle diagram about the first axis and the fourth axis in an embodiment;

[0054] Figure 9 A multi-axle driving steering control system composition block diagram of an intelligent transport vehicle provided by the present application;

[0055] Figure 10 A possible electronic device hardware structure schematic diagram provided by the present application;

[0056] Figure 11 A possible computer readable storage medium hardware structure schematic diagram provided by the present application. DETAILED DESCRIPTION

[0057] The specific embodiments of the present application are described in further detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0058] As Figure 1 A multi-axle distribution schematic diagram of an intelligent transport vehicle involved in a multi-axle driving steering control method provided by the present application.

[0059] As Figure 1As shown, the intelligent transport vehicle includes four shafts (first shaft-fourth shaft) arranged in sequence on the vehicle frame, wherein the first shaft and the fourth shaft are configured as steering shafts, and the second shaft and the third shaft are configured as drive steering shafts. The motor is connected to drive the steering axle (drive steering shaft) through a transmission shaft, and drives the wheels at both ends of the axle to rotate circumferentially, thereby controlling the wheel travel. For example, the motor motor1 is connected to the second shaft through a certain transmission shaft, and the second shaft can drive the vehicle to move 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 to move forward or backward under the driving action of the motor motor2. The running direction of the motor motor1 and the motor motor2 is switched, the running direction of the vehicle is switched, and bidirectional running of the vehicle is realized.

[0060] Each of the first shaft-fourth shaft is configured with a steering execution mechanism for controlling steering, and the steering control principle of the steering execution mechanism is a prior art. Figure 2 As shown, the steering control principle diagram of the wheels at both ends of a single shaft is shown, and the hydraulic station provides hydraulic power to drive the extension and retraction of the steering cylinder, which drives the steering knuckle of each shaft to rotate to realize steering. In the embodiment of the present application, the hydraulic pressure is controlled by an electromagnetic proportional valve, the opening size of the multi-way valve is controlled to control the flow of the steering loop hydraulic oil, thereby realizing the size of the steering angle, and a separate oil circuit is arranged on each shaft for separate steering control, and the four shafts are cooperatively steered. Figure 2 As shown, the steering control principle diagram of the wheels at both ends of a single shaft is shown, and the hydraulic station provides hydraulic power to drive the extension and retraction of the steering cylinder, which drives the steering knuckle of each shaft to rotate to realize steering. In the embodiment of the present application, the hydraulic pressure is controlled by an electromagnetic proportional valve, the opening size of the multi-way valve is controlled to control the flow of the steering loop hydraulic oil, thereby realizing the size of the steering angle, and a separate oil circuit is arranged on each shaft for separate steering control, and the four shafts are cooperatively steered.

[0061] Based on the foregoing steering principle, as shown in the flowchart of Figure 3 The embodiment provides a multi-shaft drive steering control method of an intelligent transport vehicle, which comprises steps S1-S3.

[0062] S1, a kinematic model about the second shaft and the third shaft is constructed based on a two-degree-of-freedom model, the steering characteristics of the second shaft and the third shaft are calculated according to the kinematic model, and the initial target steering angle of each wheel on the second shaft and the third shaft is adjusted to be a wheel target steering angle according to the steering characteristics.

[0063] S2, for any wheel on the second axis and the third axis, taking the target heading angle of the vehicle and the wheel target angle as input, the running parameter of the corresponding driving mechanism as disturbance, and the actual wheel angle as feedback, controlling the wheel steering on the corresponding axis; traversing all the wheels on the second axis and the third axis to obtain the actual wheel angles of the wheels on the second axis and the third axis;

[0064] S3, obtaining the steering relationship of the first axis and the second axis and the steering relationship of the third axis and the fourth axis based on the Ackerman angle theorem, and servo-controlling the wheel steering on the first axis and the fourth axis according to the steering relationship.

[0065] It can be understood that the embodiment provides a multi-axis driving steering control method of an intelligent transport vehicle based on the defects pointed out by the background technology and based on the ideas of single-axis wheel control and multi-axis wheel cooperative control. Since the second axis and the third axis have driving capability, they provide driving power for vehicle driving, so firstly, a kinematic model of the second axis and the third axis is constructed based on a two-degree-of-freedom model, the steering relationship of the second axis and the third axis with driving capability is calculated through the kinematic model of the second axis and the third axis, the initial target wheel angle obtained according to the vehicle steering instruction is corrected based on the steering relationship to obtain a more accurate target wheel angle; then the target wheel angle and the target heading angle of the vehicle are taken as input to control the steering angle of each wheel of the second axis and the third axis respectively in a closed loop, and the running parameter (such as torque and speed) of the motor corresponding to the second axis or the third axis is taken as the disturbance (feedforward) of the closed loop control process, and the real-time actual wheel angle is detected by a sensor as feedback, so as to obtain a more accurate actual wheel angle after closed loop control. After obtaining the control quantity of the corresponding wheel of the second axis or the third axis, the wheels of the first axis and the fourth axis are controlled in a servo control mode through the steering relationship of the first axis and the second axis and the steering relationship of the third axis and the fourth axis. The control mode of the embodiment 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 scheme for route planning optimization of the intelligent transport vehicle.

[0066] In a possible embodiment, step S1 includes steps S101-S102:

[0067] S101, constructing a kinematic model about the second axis and the third axis based on a two-degree-of-freedom model, as shown in Figure 4 The kinematic model about the second axis and the third axis in the embodiment is shown in the following figure, Figure 4 The midpoint O is the center of rotation in the vehicle steering process, and the kinematic model can be represented by the following state space equation:

[0068]

[0069]

[0070]

[0071] wherein, is the wheelbase between the second and third axles, is the vertical distance of the center of rotation O relative to the second axle, is the vertical distance of the center of rotation O relative to the second axle, is the deflection stiffness of the second axle wheels, is the deflection stiffness of the third axle wheels, is the vehicle yaw rate, is the vehicle mass center side slip angle, is the front wheel steering angle, is the vehicle mass, is the vehicle moment of inertia about the Z axis, is the vehicle velocity in the X direction;

[0072] According to the state space equation, the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristics is obtained as shown in the following table:

[0073]

[0074] wherein, is the difference of the vehicle yaw rate at adjacent sampling time instants;

[0075] It can be understood that in the study of the kinematic model, the general research idea is to ignore the tire side slip angle or to regard it as a disturbance constraint within a small controllable range. For the intelligent transport vehicle described in the embodiment, the second axle and the third axle kinematic model is approximated using a two-degree-of-freedom model as shown in Figure 4 In the speed / angle adjustment control system of the second axle and the third axle, the steering characteristic relationship of the second axle and the third axle with driving capability is first calculated through the kinematic model as shown in Figure 4

[0076] S102, continuously judging the current steering characteristics according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristics;

[0077] If it is determined that the current steering characteristics are neutral steering, in this case, it is considered that the steering radius of the vehicle is almost equal to the ideal steering radius, and the current wheel steering angle is taken as the wheel target steering angle;

[0078] As shown in Figure 5 ​The insufficient turning condition is shown. If the current turning characteristic is determined to be insufficient turning, it is considered that the actual turning radius of the vehicle is greater than the ideal (planned trajectory) turning radius, and the turning angle of the wheels is increased until the neutral turning is determined;

[0079] If the current turning characteristic is determined to be excessive turning, the condition is opposite to the insufficient turning condition. Figure 5 The opposite condition is shown. It is considered that the actual turning radius of the vehicle is less than the ideal (planned trajectory) turning radius, and the turning angle of the wheels is reduced until the neutral turning is determined.

[0080] It can be understood that after obtaining the relationship between the front wheel turning angle, the vehicle yaw angular velocity and the turning characteristic, the corresponding angular velocity and angle of the second axis and the third axis can be calculated according to the driving force distribution, and corresponding adjustment can be performed.

[0081] In a possible embodiment mode, the step S2 further includes:

[0082] The planned trajectory of the vehicle is obtained based on the turning instruction, the tangent of the planned trajectory is taken as the target heading of the vehicle, and the target heading angle of the vehicle is calculated according to the target heading of the vehicle.

[0083] It can be understood that the heading angle is the included angle between the heading and the north direction. As shown in Figure 5 The target heading of the wheels changes with the planned trajectory of the vehicle, and therefore the target heading angle of the vehicle is a changing value. By continuously adjusting the wheel turning, the real-time heading of the vehicle tends to the target heading of the vehicle, so that the running trajectory of the vehicle tends to the planned trajectory.

[0084] In a possible embodiment mode, as shown in Figure 6 The single wheel turning control system schematic diagram of the second axis and the third axis is shown, which adopts a sliding mode control algorithm to design a target yaw moment control system, and is combined with Figure 6 As shown in the step S2, it includes:

[0085] The speed / turning angle adjustment control system shown in Figure 6 is constructed for each wheel of the second axis and the third axis, that is, at least four speed / turning angle adjustment control systems shown in Figure 6 are provided for the two wheels at the ends of the second axis and the two wheels at the ends of the third axis;

[0086] The input of each of the rotation angle / rotation speed adjustment control systems includes a target heading angle of the vehicle, the wheel target rotation angle, and the actual rotation angle of the wheel acquired by the rotation angle encoder on each wheel, the disturbance of the rotation angle / rotation speed adjustment control system includes the operation parameters of the driving mechanism on the corresponding axis of the current wheel, the operation parameters of the driving mechanism include the torque of the driving motor and the rotation speed of the driving motor, and the output of the rotation angle / rotation speed adjustment control system is the control parameter of the steering execution mechanism on the corresponding axis of the current wheel, for example Figure 2 the electric control signal of the electromagnetic proportional valve shown in the figure;

[0087] The actual rotation angle of each wheel of the second axis and the third axis is acquired by the rotation angle encoder arranged on each wheel.

[0088] It can be understood that each wheel of the second axis and the third axis is controlled individually, and the steering of the wheels on the same axis is controlled individually, so that the steering control of the wheels on the same axis is checked, and the steering control precision of the wheels on the second axis and the third axis is improved.

[0089] In a possible implementation mode, Figure 7 The kinematic model of the first axis and the second axis in the embodiment is shown, based on Figure 7 According to the model shown, the rotation angles of the inner and outer wheels of the first axis and the rotation angles of the inner and outer wheels of the second axis conform to the Ackerman rotation angle relationship, and are expressed as follows:

[0090] ,

[0091] wherein, is the target rotation angle of the inner wheel of the first axis, is the actual rotation 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.

[0092] Since the control mode of the first axis is follow-up control, the rotation angle control of the first axis depends on the rotation angle control of the second axis, therefore, in the embodiment, only the control of the inner wheel rotation angle of the first axis is considered, the target rotation angle of the inner wheel of the first axis is acquired according to the target rotation angle of the inner wheel of the second axis, and the following relationship is obtained:

[0093] .

[0094] In a possible implementation mode, the rotation angle control principle of the fourth axis is similar to the rotation angle control principle of the first axis in the previous embodiment, and in step S3, the steering relationship between the third axis and the fourth axis obtained based on the Ackerman rotation angle theorem is shown as follows:

[0095] ,

[0096] wherein, is the inner wheel target steering angle of the fourth axle, is the inner wheel actual steering angle of the third axle, L4 is the wheelbase of the third axle to the fourth axle, L3 is the vertical distance from the rotation center to the third axle, and L3+L4 is equal to the vertical distance from the rotation center to the fourth axle.

[0097] The inner wheel target steering angle of the first axle is obtained through the above embodiment and the inner wheel target steering angle of the fourth axle is obtained, and then the steering of the wheels on the first axle and the steering of the wheels on the fourth axle can be controlled, including:

[0098] PID control systems as shown in Figure 8 are respectively constructed for the first axle and the fourth axle;

[0099] The calculated inner wheel target steering angle of the first axle is taken as the input quantity of the PID control system, the actual inner wheel steering angle of the first axle is collected as the feedback quantity, the control parameters of the steering actuator on the first axle are adjusted through the PID algorithm, and the adjusted actual inner wheel steering angle of the first axle is obtained;

[0100] The calculated inner wheel target steering angle of the fourth axle is taken as the input quantity of the PID control system, the actual inner wheel steering angle of the fourth axle is collected as the feedback quantity, the control parameters of the steering actuator on the fourth axle are adjusted through the PID algorithm, and the adjusted actual inner wheel steering angle of the fourth axle is obtained.

[0101] It can be understood that for the steering angle control of the first axle and the fourth axle, a classic PID control algorithm is adopted, the values collected by the first axle and the fourth axle steering angle encoders are taken as the feedback quantities, the steering control servo proportional valve is regulated and controlled, and high-precision closed-loop control of the steering angle is realized.

[0102] Figure 9 A multi-axle driving steering control system structure diagram of an intelligent transport vehicle provided by the embodiment of the present application is shown in Figure 9 A multi-axle driving steering control system of an intelligent transport vehicle, including a model construction module, a first control module and a second control module, wherein:

[0103] The model construction module is used to construct a kinematic model about the second axle and the third axle based on a two-degree-of-freedom model, calculate the steering characteristics of the second axle and the third axle according to the kinematic model, and adjust the initial target steering angle of each wheel on the second axle and the third axle to the wheel target steering angle according to the steering characteristics;

[0104] The first control module is configured to, for any wheel on the second axis and the third axis, take the target heading angle of the vehicle and the wheel target angle as input, take the operation parameter of the driving mechanism on the corresponding axis as disturbance, and take the actual wheel angle as feedback to control the wheel steering on the corresponding axis; and the first control module is further configured to traverse all the wheels on the second axis and the third axis to obtain the actual wheel angles of the wheels on the second axis and the third axis.

[0105] The second control module is configured 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 wheel steering on the first axis and the wheel steering on the fourth axis according to the steering relationship.

[0106] It can be understood that the multi-axis driving steering control system of the intelligent transport vehicle provided by the present application corresponds to the multi-axis driving steering control method of the intelligent transport vehicle provided by the above-mentioned embodiments, and the related technical features of the multi-axis driving steering control system of the intelligent transport vehicle can refer to the related technical features of the multi-axis driving steering control method of the intelligent transport vehicle, which will not be repeated here.

[0107] Please refer to Figure 10 , Figure 10 The embodiment of the electronic device provided by the present application is shown in the embodiment of the electronic device provided by the present application. As shown in Figure 10 The embodiment of the electronic device provided by the present application is shown in the embodiment of the electronic device provided by the present application. As shown in

[0108] S1, a kinematic model about the second axis and the third axis is constructed based on a two-degree-of-freedom model, the steering characteristics of the second axis and the third axis are calculated according to the kinematic model, and the initial target angles of the wheels on the second axis and the third axis are adjusted to the wheel target angles according to the steering characteristics;

[0109] S2, for any wheel on the second axis and the third axis, the target heading angle of the vehicle and the wheel target angle are taken as input, the operation parameter of the driving mechanism on the corresponding axis is taken as disturbance, and the actual wheel angle is taken as feedback to control the wheel steering on the corresponding axis; and the first control module is further configured to traverse all the wheels on the second axis and the third axis to obtain the actual wheel angles of the wheels on the second axis and the third axis.

[0110] S3, the steering relationship between the first axis and the second axis and the steering relationship between the third axis and the fourth axis are obtained based on the Ackerman angle theorem, and the wheel steering on the first axis and the wheel steering on the fourth axis are controlled according to the steering relationship.

[0111] Please refer to Figure 11 , Figure 11An embodiment of a computer readable storage medium provided by the present application is shown in the figure. As shown in the figure Figure 11 The embodiment provides a computer readable storage medium 1100, and a computer program 1111 is stored in the computer readable storage medium 1100, and the computer program 1111 is executed by a processor to implement the following steps:

[0112] S1, a kinematic model about the second axis and the third axis is constructed based on a two-degree-of-freedom model, steering characteristics of the second axis and the third axis are calculated according to the kinematic model, and initial target steering angles of each wheel on the second axis and the third axis are adjusted to wheel target steering angles according to the steering characteristics;

[0113] S2, for any wheel on the second axis and the third axis, a target heading angle of the vehicle and the wheel target steering angle are taken as input quantities, an operation parameter of a driving mechanism on the corresponding axis is taken as a disturbance quantity, and an actual steering angle of the wheel is taken as a feedback quantity, and steering of the wheel on the corresponding axis is controlled; all wheels on the second axis and the third axis are traversed to obtain actual steering angles of the wheels on the second axis and the third axis;

[0114] S3, a steering relationship between the first axis and the second axis and a steering relationship between the third axis and the fourth axis are obtained based on the Ackermann steering theorem, and steering of the wheels on the first axis and the fourth axis is controlled according to the steering relationship.

[0115] The multi-axis drive steering control method, system and storage medium of the intelligent transport vehicle provided by the embodiment of the present application are improved on the basis of the existing chassis technology and suspension technology. The opening size of the multi-way servo proportional valve is controlled to control the flow of the hydraulic oil of each axis steering loop, so that the size adjustment of the steering angle of each axis is realized. A separate oil way is arranged on each axis to control the steering independently. The four steering axes are cooperatively steered. The steering relationship of the second axis and the third axis with driving capability is given priority, and the steering angles of the first axis and the fourth axis are controlled according to the multi-axis cooperative steering relationship. Specifically, the intelligent transport vehicle uses the drive-by-wire technology, takes the vehicle heading angle and the wheel steering angle as the target control quantity, controls the steering angle and speed of each tire on the second axis and the third axis, uses the independent steering control unit composed of the steering servo proportional valve and the linkage mechanism to realize the independent control of the steering angle of each wheel on each axis, simultaneously takes the driving torque signals of the two independent driving direct current motors as the feedforward quantity, and a high-precision steering angle sensor is arranged on each tire on the second axis and the third axis to collect the actual steering angle of the wheel in real time. The control system can control the steering servo proportional valve according to the actual steering angle feedback signal of the sensor, so as to realize the accurate output of the tire steering under different driving force distribution.

[0116] The application realizes accurate output of tire steering under different driving force distribution, improves the multi-axle driving steering control accuracy of the intelligent transport vehicle, and provides a more flexible and efficient implementation scheme for route planning optimization of the intelligent transport vehicle.

[0117] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0118] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can 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.

[0119] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as combinations of flows and / or blocks in the flowcharts and / or block diagrams, 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 devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that performs the functions specified in one or more blocks.

[0120] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory produce a product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that performs the functions specified in one or more blocks.

[0121] These computer program instructions can also be loaded into a computer or other programmable data processing device, so that a series of operation steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that performs the functions specified in one or more blocks.

[0122] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims include all such modifications and variations as fall within the scope of the present application.

[0123] It is apparent that those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. Thus, it is intended that the application include all such modifications and alterations insofar as they come within the scope of the claims or the equivalents thereof.

Claims

1. A multi-axle drive steering control method of an intelligent transport vehicle, characterized by, The intelligent transport vehicle comprises a first shaft, a second shaft, a third shaft and a fourth shaft 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 execution mechanism for controlling steering, and the second shaft and the third shaft are respectively configured with a driving mechanism; the control method comprises: S1, a kinematic model about the second shaft and the third shaft is constructed based on a two-degree-of-freedom model, steering characteristics of the second shaft and the third shaft are calculated according to the kinematic model, and initial target steering angles of each wheel on the second shaft and the third shaft are adjusted to wheel target steering angles according to the steering characteristics; comprising: S101, a kinematic model about the second shaft and the third shaft is constructed based on a two-degree-of-freedom model, and the kinematic model can be expressed as a state space equation as follows: wherein, is the wheelbase between the second and third axles, is the vertical distance of the center of rotation from the second axle, is the vertical distance of the center of rotation from the second axle, is the deflection stiffness of the second axle wheel, is the deflection stiffness of the third axle wheel, is the vehicle yaw rate, is the vehicle mass center side slip angle, is the front wheel steering angle, is the vehicle mass, is the vehicle moment of inertia about the Z axis, is the vehicle velocity in the X direction; According to the state space equation, the following relationship between the front wheel steering angle, the vehicle yaw angular velocity and the steering characteristics is obtained: wherein, is the difference of the vehicle yaw rate at adjacent sampling instants. S102, the current steering characteristics are continuously judged according to the relationship between the front wheel steering angle, the vehicle yaw angular velocity and the steering characteristics; If the current steering characteristics are determined to be neutral steering, the current wheel steering angle is taken as the wheel target steering angle; If the current steering characteristics are determined to be insufficient steering, the steering angle of the wheel is increased until the neutral steering is determined; If the current steering characteristics are determined to be excessive steering, the steering angle of the wheel is reduced until the neutral steering is determined; S2, for any wheel on the second shaft and the third shaft, the target heading angle of the vehicle and the wheel target steering angle are taken as input quantities, the operating parameters of the driving mechanism on the corresponding shaft are taken as disturbance quantities, and the actual steering angle of the wheel is taken as a feedback quantity, so as to control the steering of the wheel on the corresponding shaft; all wheels on the second shaft and the third shaft are traversed to obtain the actual steering angle of each wheel on the second shaft and the third shaft. S3, the steering relationship between the first shaft and the second shaft and the steering relationship between the third shaft and the fourth shaft are obtained based on the Ackermann steering theorem, and the steering of the wheels on the first shaft and the fourth shaft is follow-up controlled according to the steering relationship.

2. The multi-axle drive steering control method of an intelligent transport vehicle according to claim 1, wherein, Step S2 further comprises: A planned trajectory of vehicle driving is obtained based on a steering instruction, a tangent line of the planned trajectory is taken as a vehicle target heading, and a target heading angle of the vehicle is calculated according to the vehicle target heading.

3. The multi-axle drive steering control method of an intelligent transport vehicle according to claim 1, wherein, Step S2 comprises: A speed / angle adjustment control system is constructed for each wheel on the second shaft and the third shaft respectively; The input quantities of each speed / angle adjustment control system include the target heading angle of the vehicle, the wheel target steering angle and the actual wheel steering angle collected, the disturbance quantities of the speed / angle adjustment control system include the operating parameters of the driving mechanism on the corresponding shaft of the current wheel, the operating parameters of the driving mechanism include the torque of the driving motor and the speed of the driving motor, and the output quantities of the speed / angle adjustment control system are the control parameters of the steering execution mechanism on the corresponding shaft of the current wheel. The actual steering angle of each wheel on the second shaft and the third shaft is obtained.

4. The multi-axle drive steering control method of an intelligent transport vehicle according to claim 1, wherein, In step S3, the steering relationship between the first shaft and the second shaft obtained based on the Ackermann steering theorem is as follows: ， wherein, is an inner wheel target rotation angle of the first axis, is an inner wheel actual rotation angle of the second axis, L1 is an axle distance from the first axis to the second axis, L2 is a perpendicular distance from the rotation center to the second axis, and L1+L2 is equal to a perpendicular distance from the rotation center to the first axis.

5. The multi-axle drive steering control method of an intelligent transport vehicle according to claim 4, wherein, In step S3, the steering relationship between the third shaft and the fourth shaft obtained based on the Ackermann steering theorem is as follows: ， wherein, is the inner wheel target rotation angle of the fourth axis, is the inner wheel actual rotation angle of the third axis, L4 is the wheelbase from the third axis to the fourth axis, L3 is the perpendicular distance from the rotation center to the third axis, and L3+L4 is equal to the perpendicular distance from the rotation center to the fourth axis.

6. The multi-axle drive steering control method of an intelligent transport vehicle according to claim 5, wherein, In step S3, the following is included: controlling the steering of the wheels on the first axle and the steering of the wheels on the fourth axle according to the steering relationship. The calculated first-axle inner wheel target rotation angle As an input quantity, the first-axle inner wheel actual rotation angle is collected as a feedback quantity, and the control parameters of the first-axle steering actuator are adjusted through a PID algorithm to obtain an adjusted first-axle inner wheel actual rotation angle. The calculated fourth axle inner wheel target rotation angle As an input quantity, the fourth axle inner wheel actual rotation angle is collected as a feedback quantity, and the control parameters of the steering actuator on the fourth axle are adjusted through a PID algorithm to obtain the adjusted fourth axle inner wheel actual rotation angle.

7. A multi-axle drive steering control system for an intelligent transport vehicle, characterized by, The system comprises the method according to any one of claims 1-6. The model construction module is configured to construct a kinematic model about the second axle and the third axle based on a two-degree-of-freedom model, calculate steering characteristics of the second axle and the third axle according to the kinematic model, and adjust initial target steering angles of the wheels on the second axle and the third axle to wheel target steering angles according to the steering characteristics. S101, constructing a kinematic model about the second axle and the third axle based on a two-degree-of-freedom model, the kinematic model can be expressed as a state space equation as follows: wherein, is the wheelbase between the second and third axles, is the vertical distance of the center of rotation from the second axle, is the vertical distance of the center of rotation from the second axle, is the deflection stiffness of the second axle wheels, is the deflection stiffness of the third axle wheels, is the vehicle yaw rate, is the vehicle mass center side slip angle, is the front wheel steering angle, is the vehicle mass, is the vehicle moment of inertia about the Z axis, is the vehicle velocity in the X direction; According to the state space equation, the following relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristics is obtained: wherein, is the difference of the vehicle yaw rate at adjacent sampling instants. S102, continuously judging the current steering characteristics according to the relationship between the front wheel steering angle, the vehicle yaw rate and the steering characteristics; If the current steering characteristics are determined to be neutral steering, the current wheel steering angle is taken as the wheel target steering angle; If the current steering characteristics are determined to be understeering, the steering angle of the wheel is increased until the neutral steering is determined; If the current steering characteristics are determined to be oversteering, the steering angle of the wheel is decreased until the neutral steering is determined; The first control module is configured to, for any wheel on the second axle and the third axle, take the target heading angle of the vehicle and the wheel target steering angle as input quantities, take the operating parameter of the driving mechanism on the corresponding axle as a disturbance quantity, and take the actual steering angle of the wheel as a feedback quantity, to control the steering of the wheel on the corresponding axle, and to traverse all the wheels on the second axle and the third axle to obtain the actual steering angles of the wheels on the second axle and the third axle. The second control module is configured to obtain the steering relationship between the first axle and the second axle and the steering relationship between the third axle and the fourth axle based on the Ackermann steering theorem, and to control the steering of the wheels on the first axle and the steering of the wheels on the fourth axle according to the steering relationship.

8. An electronic device, comprising: The system comprises a memory and a processor, and the processor is configured to execute a computer management program stored in the memory to implement the steps of the multi-axle drive steering control method of the intelligent transport vehicle according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The system comprises a memory and a processor, and the processor is configured to execute a computer management program stored in the memory to implement the steps of the multi-axle drive steering control method of the intelligent transport vehicle according to any one of claims 1-6.

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