Distributed driving multi-axle vehicle steering control method and device

Abstract

The invention relates to a distributed driving multi-axle vehicle steering control method and device, and belongs to the technical field of vehicle power control. The method comprises the steps that when a steering demand of a multi-axle vehicle is received, different judgment can be made according to different vehicle speed states, and then different target steering modes are determined; when the running speed is larger than the preset speed, the stability of the multi-axle vehicle can be judged according to the current yaw velocity to obtain the running state, then the corresponding target steering mode is determined according to the running state, and when the running speed is not larger than the preset speed, the steering requirement can be judged to obtain the steering state. The corresponding target steering mode is determined according to the steering state, then steering control can be carried out on the multi-axle vehicle according to the target steering mode and distributed driving, different steering control can be carried out on the multi-axle vehicle according to different conditions, and the stability of the vehicle in the steering process is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle power control, and in particular, to a steering control method and device for a multi-axle vehicle with distributed drive. Background Art

[0002] Multi-axle heavy vehicles are mainly used for transporting special equipment and performing professional tasks under various complex traffic conditions, where high requirements are placed on passability, mobility, and stability. The multi-wheel steering system of multi-axle vehicles provides a smaller turning radius and diverse steering modes by reasonably controlling the wheel angles of each axle, which is of great significance for improving the mobility and stability of heavy vehicles and is one of the technologies that multi-axle vehicles urgently need to develop nowadays. Currently, the multi-wheel steering system mainly adopts a mechanical steering method to control the distribution of the wheel angles of each wheel. And multi-wheel steering can have different modes, which can be adjusted according to the vehicle driving state. On the basis of multi-wheel steering, a distributed drive vehicle can change the vehicle steering characteristics through differential steering and direct yaw moment control. Therefore, it is necessary to integrate the control of distributed drive and multi-wheel steering.

[0003] Currently, the integration technology of the two methods mainly starts from the perspective of vehicle stability and distributes the two control methods at high speeds. One idea is to make a decision distribution of multi-wheel steering and direct yaw moment control through the load transfer ratio, and improve vehicle stability through the integrated control of the two. Another idea is to decouple the wheel steering and differential steering of different axles, with some wheels performing angular steering and some wheels performing differential steering. However, different steering control methods such as multi-wheel steering, differential steering, and direct yaw moment control have different implementation methods, effects, and applicable ranges. At the same time, there are couplings between the various steering control methods, which affect each other under different driving conditions. Differential steering can assist the steering system to further increase the wheel angle and reduce the turning radius. But at the same time, it will also generate an additional yaw moment, which has an adverse effect on the vehicle stability, especially under high-speed conditions.

[0004] Therefore, there is an urgent need to propose a steering control method and device for a multi-axle vehicle with distributed drive to solve the technical problem in the prior art that the multi-wheel steering system uses different control methods to cooperate in controlling the vehicle, which will generate an additional yaw moment and have an adverse effect on the vehicle stability. Summary of the Invention

[0005] In view of this, it is necessary to provide a steering control method and device for a multi-axle vehicle with distributed drive to solve the technical problem in the prior art that the multi-wheel steering system uses different control methods to cooperate in controlling the vehicle, which will generate an additional yaw moment and have an adverse effect on the vehicle stability.

[0006] To solve the above problems, in a first aspect, the present invention provides a steering control method for a multi-axle vehicle with distributed drive, including: When receiving a steering demand of the multi-axle vehicle, obtain the current driving information of the multi-axle vehicle; the current driving information includes driving speed and current yaw rate; When the driving speed is greater than a preset speed, judge the stability of the multi-axle vehicle according to the current yaw rate to obtain a driving state, and determine a target steering mode according to the driving state; the target steering mode is stability steering or steering system steering; When the driving speed is not greater than the preset speed, judge the steering demand to obtain a steering state; and determine a target steering mode according to the steering state; the target steering mode is differential integrated steering or steering system steering; Steer the multi-axle vehicle according to the target steering mode and distributed drive.

[0007] In a possible implementation manner, the judging the stability of the multi-axle vehicle according to the current yaw rate to obtain a driving state includes: Obtain a yaw rate difference according to the current yaw rate and a preset linear yaw rate; Judge whether the absolute value of the yaw rate difference is greater than a preset difference; If so, determine that the driving state of the multi-axle vehicle is an unstable state; If not, determine that the driving state of the multi-axle vehicle is a stable state.

[0008] In a possible implementation manner, the determining a target steering mode according to the driving state includes: When the driving state is the unstable state, determine that the target steering mode is the stability steering; When the driving state is the stable state, determine that the target steering mode is the steering system steering.

[0009] In a possible implementation manner, the steering demand includes a steering wheel angle; the judging the steering demand to obtain a steering state includes: Judge whether the steering wheel angle is greater than or equal to a preset angle; If so, the steering state of the multi-axle vehicle is a large steering state; If so, the steering state of the multi-axle vehicle is a small steering state.

[0010] In a possible implementation manner, the determining a target steering mode according to the steering state includes: When the steering state is the large steering state, determine that the target steering mode is the differential integrated steering; When the steering state is the small steering state, determine that the target steering mode is the steering system steering.

[0011] In a possible implementation, the method further includes: When the target steering mode is the steering system steering, perform steering control on the multi-axle vehicle according to the steering system steering.

[0012] In a possible implementation, the performing steering control on the multi-axle vehicle according to the steering system steering includes: Obtain the wheelbase of each axle on the multi-axle vehicle, and determine the steering center and the wheel angle of the first axle; Determine the proportionality coefficient of each axle according to all the wheelbases; Calculate the proportionality coefficient of each axle according to the wheel angle of the first axle one by one to obtain the wheel angle of each axle; Perform steering control on the left and right wheels of the corresponding axle on the multi-axle vehicle according to the wheel angle.

[0013] In a possible implementation, the current driving information includes the tire rolling radius, the single-axle return torque, the single-axle frictional resistance torque, the moment of inertia of the left wheel of each axle about the kingpin, the transmission ratio of the electric wheel reducer, the kingpin offset at the wheel center, the kingpin inclination angle, and the kingpin caster angle; when the target steering mode is the differential integrated steering, the performing steering control on the multi-axle vehicle according to the target steering mode and distributed drive includes: Calculate the tire rolling radius, the moment of inertia, the transmission ratio of the electric wheel reducer, the kingpin offset, the kingpin inclination angle, and the kingpin caster angle of each axle to obtain a first coefficient; Calculate the tire rolling radius, the single-axle return torque, the single-axle frictional resistance torque, the transmission ratio of the electric wheel reducer, the kingpin offset, the kingpin inclination angle, and the kingpin caster angle of each axle to obtain a second coefficient; Obtain the left wheel angle of each axle according to the first coefficient and the second coefficient; Obtain the mechanical system steering angle of each axle according to the left wheel angle and a preset proportionality coefficient; Obtain the actual wheel angle of each axle according to the mechanical system steering angle and the left wheel angle, and perform steering control on the multi-axle vehicle according to the actual wheel angle of each axle.

[0014] In a possible implementation, the current driving information includes the tire rolling radius, the single-axle self-aligning torque, the single-axle frictional resistance torque, the moment of inertia of the left wheel of each axle about the kingpin, the transmission ratio of the electric-wheel reducer, the kingpin offset at the wheel center, the kingpin inclination, and the caster angle; when the target steering mode is the differential integrated steering, the steering control of the multi-axle vehicle according to the target steering mode and distributed drive includes: Calculating the tire rolling radius, the moment of inertia, the transmission ratio of the electric-wheel reducer, the kingpin offset, the kingpin inclination, and the caster angle of each axle to obtain a first coefficient; Calculating the tire rolling radius, the single-axle self-aligning torque, the single-axle frictional resistance torque, the transmission ratio of the electric-wheel reducer, the kingpin offset, the kingpin inclination, and the caster angle of each axle to obtain a second coefficient; Obtaining the left-wheel rotation angle of each axle according to the first coefficient and the second coefficient; Obtaining the mechanical system steering angle of each axle according to the left-wheel rotation angle and a preset proportional coefficient; Obtaining the actual wheel rotation angle of each axle according to the mechanical system steering angle and the left-wheel rotation angle, and performing steering control on the multi-axle vehicle according to the actual wheel rotation angle of each axle.

[0015] In a second aspect, the present invention further provides a steering control device for a multi-axle vehicle with distributed drive, including: An information acquisition module, configured to acquire the current driving information of the multi-axle vehicle when receiving a steering demand of the multi-axle vehicle; the current driving information includes the driving speed and the current yaw rate; A stability judgment module, configured to judge the stability of the multi-axle vehicle according to the current yaw rate when the driving speed is greater than a preset speed, obtain a driving state, and determine a target steering mode according to the driving state; the target steering mode is stability steering or steering system steering; A steering judgment module, configured to judge the steering demand when the driving speed is not greater than the preset speed, obtain a steering state; and determine a target steering mode according to the steering state; the target steering mode is differential integrated steering or steering system steering; A steering control module, configured to perform steering control on the multi-axle vehicle according to the target steering mode and distributed drive.

[0016] The beneficial effects of the present invention are as follows: when receiving the steering demand of a multi-axle vehicle, different judgments can be made according to different vehicle speed states, and then different target steering modes can be determined. When the driving speed is greater than the preset speed, the stability of the multi-axle vehicle can be judged according to the current yaw rate to obtain the driving state, so that the driving state of the vehicle stability can be determined through the additional yaw moment, and then the corresponding target steering mode can be determined according to the driving state. When the driving speed is not greater than the preset speed, the steering demand can be judged to obtain the steering state, and then the corresponding target steering mode can be determined according to the steering state. Then, the multi-axle vehicle can be steered according to the target steering mode and distributed drive, so that different steering controls can be performed on the multi-axle vehicle according to different situations, and the stability of the vehicle during steering is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic flowchart of an embodiment of a steering control method for a multi-axle vehicle with distributed drive provided by the present invention; Figure 2 FIG. is a schematic structural diagram of an embodiment of steering mode decision provided by the present invention; Figure 3 FIG. is a schematic flowchart of an embodiment of a steering mode of a steering system adopted by the present invention; Figure 4 FIG. is a schematic structural diagram of an embodiment of a six-axle vehicle adopted by the present invention; Figure 5 For the present invention Figure 1 FIG. is a schematic flowchart of an embodiment of step S104 in the present invention; Figure 6 FIG. is a schematic structural diagram of an embodiment of a mechanical structure principle diagram of a kingpin angle of a wheel motor provided by the present invention; Figure 7 For the present invention Figure 1 FIG. is a schematic flowchart of another embodiment of step S104 in the present invention; Figure 8 FIG. is a schematic structural diagram of an embodiment of a steering control device for a multi-axle vehicle with distributed drive provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will specifically describe the preferred embodiments of the present invention with reference to the drawings. The drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, but are not used to limit the scope of the present invention.

[0019] As Figure 1 shown, a specific embodiment of the present invention discloses a steering control method for a multi-axle vehicle with distributed drive, including: S101. When receiving the steering demand of a multi-axle vehicle, obtain the current driving information of the multi-axle vehicle; the current driving information includes the driving speed and the current yaw rate.

[0020] The multi-axle vehicle steering control method provided by the embodiments of the present application can be applied to a multi-axle vehicle steering control system. Among them, the multi-axle vehicle steering control can be based on a software system running on a terminal device. The terminal device can be a server, a tablet computer, an Augmented Reality (AR) / Virtual Reality (VR) device, a notebook computer, an Ultra-Mobile Personal Computer (UMPC), a netbook, a Personal Digital Assistant (PDA), a mobile phone, and other terminal devices. The embodiments of the present application do not impose any restrictions on the specific type of the terminal device.

[0021] Among them, the driver can input the steering demand through the steering wheel angle. When the steering wheel of the multi-axle vehicle detects the steering wheel angle, the multi-axle vehicle receives the steering demand, and then can obtain the current driving information of the multi-axle vehicle. The current driving information can include parameters such as the driving speed, the current time, the engine speed, the vehicle mass, the pedal opening, and the moment of inertia. Specifically, it can be set according to the actual situation, and the embodiments of the present invention do not limit this here.

[0022] Further, the sensor collects the steering wheel angle input by the driver and the driver pedal opening, calculates the total longitudinal demand torque according to the driver's accelerator pedal opening, obtains the wheel speed according to the wheel speed sensor, and then estimates the actual vehicle speed. The actual yaw rate of the vehicle is obtained by using the yaw rate sensor, and the actual sideslip angle of the center of mass is estimated according to the state observer. According to the stability criterion calculated by the upper controller, three steering modes are determined by the threshold method through the steering angle size, vehicle speed, and vehicle stable state: steering system steering, differential integrated steering, and stability steering.

[0023] S102. When the driving speed is greater than the preset speed, judge the stability of the multi-axle vehicle according to the current yaw rate, obtain the driving state, and determine the target steering mode according to the driving state; the target steering mode is stability steering or steering system steering.

[0024] Among them, after detecting the current driving information of the multi-axle vehicle, the driving speed can be judged, and the driving speed is judged whether it is greater than the preset speed , and the preset speed can be specified by the driver or calibrated according to the actual vehicle. If so, it means that the multi-axle vehicle is driving at a high speed, then , the stability of the multi-axle vehicle can be further judged according to the current yaw rate to obtain the driving state, and then the target steering mode can be determined according to the driving state. The target steering mode can include stability steering and steering system steering.

[0025] S103. When the driving speed is not greater than the preset speed, judge the steering demand to obtain the steering state; and determine the target steering mode according to the steering state; the target steering mode is differential integrated steering or steering system steering.

[0026] Among them, if the driving speed is not greater than the preset speed , then , it means that the multi-axle vehicle is driving at a low speed, and the steering demand can be judged to obtain the steering state; then the target steering mode can be determined according to the steering state; the target steering mode is differential integrated steering or steering system steering and steering system steering.

[0027] S104. Perform steering control on the multi-axle vehicle according to the target steering mode and distributed drive.

[0028] Among them, after determining the target steering mode, the multi-axle vehicle can be controlled to control the wheels on both sides of the multi-axle according to the target steering mode. When the target steering mode is specifically differential integrated steering or stability steering, the multi-axle vehicle can be steered according to the target steering mode and distributed drive.

[0029] Compared with the prior art, when receiving the steering demand of the multi-axle vehicle in this embodiment, different judgments can be made according to different vehicle speed states, and then different target steering modes can be determined. When the driving speed is greater than the preset speed, the stability of the multi-axle vehicle can be judged according to the current yaw rate to obtain the driving state, so that the driving state of vehicle stability can be determined by the additional yaw moment, and then the corresponding target steering mode can be determined according to the driving state. When the driving speed is not greater than the preset speed, the steering demand can be judged to obtain the steering state, and then the corresponding target steering mode can be determined according to the steering state. Then, the multi-axle vehicle can be steered according to the target steering mode and distributed drive, so that the multi-axle vehicle can be steered differently according to different situations, improving the stability of the vehicle during steering.

[0030] In some embodiments of the present invention, step S102 includes: Obtain the yaw rate difference according to the current yaw rate and the preset linear yaw rate.

[0031] Among them, the current driving information may further include the current yaw rate , the stability of a multi-axle vehicle can be judged through a vehicle reference model, and the vehicle reference model adopts n a linear two-degree-of-freedom model of distributed drive and multi-wheel steering for each axle, as shown in formula (1): (1) In the formula, is the reference yaw rate, is the reference sideslip angle of the center of mass, is the total vehicle mass, is the distance from the i -th axle to the center of mass of the vehicle, is the i -th axle sideslip stiffness, is the actual longitudinal speed, is the moment of inertia of the vehicle about the z axis, is the i -th axle wheel steering angle. n The model of the multi-axle vehicle can be configured according to the specific number of axles and the number of steering wheels of the vehicle to adapt to the specific vehicle type.

[0032] Calculate the reference yaw rate and the reference sideslip angle of the center of mass of the multi-axle vehicle, and then combine the current yaw rate and the sideslip angle of the center of mass of the multi-axle vehicle to judge the stability of the vehicle. Specifically, the yaw rate threshold method can be used to calculate the current yaw rate and the reference yaw rate to obtain the yaw rate difference , as shown in formula (2): (2) Judge whether the absolute value of the yaw rate difference is greater than the preset difference; If so, determine that the driving state of the multi-axle vehicle is an unstable state; If not, determine that the driving state of the multi-axle vehicle is a stable state.

[0033] Among them, after calculating the yaw rate difference , the yaw rate difference can be judged, and judge whether the absolute value of the yaw rate difference is greater than the preset difference ; the preset difference can be set according to the actual situation, and in the embodiments of the present invention, it is not limited here. Calibrate according to vehicle speed, driving style, etc. When , determine that the driving state of the multi-axle vehicle is an unstable state, and the stability flag , when When it is determined that the driving state of the multi-axle vehicle is a stable state, the stability flag bit .

[0034] In some embodiments of the present invention, step S102 includes: When the driving state is an unstable state, determine that the target steering mode is stability steering.

[0035] Among them, when the speed is relatively high, that is, the vehicle speed exceeds a certain preset speed , the vehicle stability flag bit , that is, the multi-axle vehicle is in an unstable state. At this time, the multi-axle vehicle has a risk of instability and requires the distributed drive system to intervene. With stability as the control target, direct yaw moment control is performed to ensure driving safety. Therefore, stability steering is used for steering, that is, the target steering mode is stability steering.

[0036] When the driving state is a stable state, determine that the target steering mode is steering system steering.

[0037] Among them, when the speed is relatively high, that is, the vehicle speed does not exceed a certain preset speed , and the vehicle stability flag bit , that is, the vehicle is in a stable state. At this time, the vehicle speed is relatively high, and the differential steering of the vehicle has a greater impact on vehicle stability. From the perspective of safety, differential steering should not be used. At the same time, the vehicle is still in a stable state and does not require stability intervention by the distributed drive system. Therefore, the distributed drive system does not intervene either, and steering system steering is used for steering, that is, the target steering mode is steering system steering.

[0038] In some embodiments of the present invention, the steering demand includes the steering wheel angle; step S103 includes: Judge whether the steering wheel angle is greater than or equal to the preset angle; If so, the steering state of the multi-axle vehicle is a large steering state; If so, the steering state of the multi-axle vehicle is a small steering state.

[0039] In a specific embodiment of the present invention, the steering demand may include the steering wheel angle. When the driving speed is not greater than the preset speed, it can be judged whether the steering wheel angle is greater than or equal to the preset angle; if so , it indicates that the steering state of the multi-axle vehicle is a large steering state; if not , it indicates that the steering state of the multi-axle vehicle is a small steering state. The large steering state represents a state with a larger angle during the steering process, and the small steering state represents a state with a smaller angle during the steering process. The preset angle can be set according to actual conditions, and the embodiments of the present invention do not limit this here.

[0040] In some embodiments of the present invention, step S103 includes: When the steering state is a large steering state, determine that the target steering mode is differential integrated steering.

[0041] Among them, when the speed is low, that is, the vehicle speed does not exceed a certain preset speed , but the driver inputs a large steering wheel angle , that is, it exceeds a certain preset angle . At this time, the required turning radius of the vehicle is small, and the impact of differential integrated steering on vehicle stability is small when the vehicle speed is low. The distributed drive control system should take mobility as the control target. That is, on the basis of the steering of the steering system, differential steering is integrated, which can further increase the wheel angle, reduce the turning radius, and improve steering mobility. Therefore, differential integrated steering is used for steering, that is, the target steering mode is differential integrated steering.

[0042] When the steering state is a small steering state, determine that the target steering mode is steering system steering.

[0043] Among them, when the speed is low, that is, the vehicle speed does not exceed a certain preset speed , and the driver inputs a small steering wheel angle , that is, it does not exceed a certain preset angle . At this time, the required turning radius of the vehicle is large, the demand for steering mobility is low, and low-speed vehicles are not likely to lose stability. Therefore, there is no need for the distributed drive system to intervene, and only the steering system can meet the steering requirements. Therefore, steering system steering is used for steering, that is, the target steering mode is steering system steering.

[0044] In some embodiments of the present invention, the method further includes: When the target steering mode is steering system steering, perform steering control on the multi-axle vehicle according to the steering of the steering system.

[0045] In specific embodiments of the present invention, differential integrated steering and stability steering require the intervention of the distributed drive system to perform steering control on the multi-axle vehicle, while steering system steering is to perform steering control on the multi-axle vehicle and does not require the intervention of the distributed drive system.

[0046] In specific embodiments of the present invention, as Figure 2 shown, the steering requirement, that is, the steering wheel angle , can be obtained through the front wheel angle sensor, and the data of the vehicle speed sensor can be obtained through the vehicle controller to obtain the current vehicle speed . Then, the steering wheel angle and the current vehicle speed can be transmitted to the active steering controller, and the active steering controller processes the current speed and the preset speed Make a judgment. When happens, the steering wheel angle can be judged against the preset angle When δ≥ happens, differential integrated steering of mode two is adopted to control the steering of a multi - axle vehicle. When δ≥ happens, the steering system of mode one is adopted to control the steering of a multi - axle vehicle; when happens, the active steering controller can judge the stability of the multi - axle vehicle. When happens, that is, when the vehicle is in a stable state, the steering system of mode one is adopted to control the steering of the multi - axle vehicle. When , that is, when the multi - axle vehicle is in an unstable state, stability steering of mode three is adopted to control the steering of the multi - axle vehicle.

[0047] In some embodiments of the present invention, the steering of the multi - axle vehicle is controlled according to the steering system. As Figure 3 shown, it includes: S301. Obtain the wheelbase of each axle on the multi - axle vehicle, and determine the steering center and the wheel angle of the first axle.

[0048] Among them, to reduce tire wear, when steering in this mode, try to ensure that the wheels of the steering axle satisfy the Ackermann steering geometry relationship. Taking a six - axle vehicle as an example, the six - axle vehicle is as Figure 4 shown. Figure 4 The six - axle vehicle in (3) In the formula, is the wheel angle of the th axle, is the proportionality coefficient, which is the ratio of the angle of the th axle to the angle of the first axle.

[0049] S302. Determine the proportionality coefficient of each axle according to all wheelbases.

[0050] Among them, the specific calculation of the proportionality coefficient is as shown in formula (4): (4) In the formula, is the wheelbase from one to six axes. It can be seen from the above formula that the multi-axis steering angle ratio is the longitudinal distance ratio from the axis to the steering center, and then the proportionality coefficient of each axis is calculated.

[0051] S303. Calculate the proportionality coefficient of each axis according to the rotation angle of the first-axis wheel in turn to obtain the wheel rotation angle of each axis.

[0052] Among them, after calculating the proportionality coefficient of each axis, it can be substituted into formula (3) for calculation one by one to obtain the wheel rotation angle of each axis.

[0053] S304. Control the left and right wheels of the corresponding axis on the multi-axis vehicle according to the wheel rotation angle.

[0054] Among them, after obtaining the wheel rotation angle of each axis, the left and right wheels on each axis of the multi-axis vehicle can be controlled to steer through the corresponding wheel rotation angle.

[0055] In some embodiments of the present invention, the current driving information includes the tire rolling radius, the single-axle return torque, the single-axle frictional torque, the moment of inertia of the left wheel of each axis around the kingpin, the transmission ratio of the electric wheel reducer, the kingpin offset at the wheel center, the kingpin inclination angle and the kingpin caster angle; as Figure 5 shown, when the target steering mode is differential integrated steering, step S104 includes: S501. Calculate the tire rolling radius, moment of inertia, electric wheel reducer transmission ratio, kingpin offset, kingpin inclination angle and kingpin caster angle of each axis to obtain the first coefficient.

[0056] Among them, when the system meets the differential integrated steering condition, it enters the differential integrated steering mode. The differential torque between the distributed drive left and right wheels is used to make the wheels generate a deflection angle around the kingpin, and its mechanical structure is as shown in the appendix Figure 6 shown, Figure 6 is the schematic diagram of the mechanical structure of the wheel-side motor kingpin deflection angle. The relationship between the torque difference of the coaxial left and right wheels and the generated rotation angle is shown in formula (5): (5) Among them, , the calculation of the first coefficient is shown in formula (6): (6) In the formula, is the longitudinal force of the left wheel, is the longitudinal force of the right wheel, is the rolling radius of the tire, is the second-order time derivative of the left wheel steering angle, is the iThe moment of inertia of the left wheel of the axle rotating about the kingpin is the i left wheel angle of the axle is the transmission ratio of the motor-wheel reducer is the kingpin offset at the wheel center is the kingpin inclination is the caster angle

[0057] S502. Calculate the tire rolling radius, single-axle self-aligning torque, single-axle frictional resistance torque, transmission ratio of the motor-wheel reducer, kingpin offset, kingpin inclination, and caster angle for each axle to obtain the second coefficient

[0058] The second coefficient is calculated as shown in formula (7): (7) In the formula is the single-axle self-aligning torque, that is, the sum of the self-aligning torques of the two wheels is the single-axle frictional resistance torque

[0059] S503. Obtain the left wheel angle of each axle according to the first coefficient and the second coefficient

[0060] Among them, the first coefficient and the second coefficient can be substituted into formula (5) for calculation, and the left wheel angle generated by the differential of the coaxial motor can be obtained .

[0061] S504. Obtain the steering angle of the mechanical system of each axle according to the left wheel angle and the preset proportional coefficient

[0062] Among them, then the steering angle of the mechanical system of each axle can be calculated according to the left wheel angle and the preset proportional coefficient as shown in formula (8): (8) In the formula is the proportional coefficient, which can be obtained through on-vehicle calibration

[0063] S505. Obtain the actual wheel angle of each axle according to the steering angle of the mechanical system and the left wheel angle, and perform steering control on the multi-axle vehicle according to the actual wheel angle of each axle

[0064] Among them, the actual wheel angle of each axle can be obtained according to the sum of the steering angle of the mechanical system and the left wheel angle as shown in formula (9): (9) In some embodiments of the present invention, the current driving information further includes the wheelbase of the differential steering axle; as Figure 7 shown, when the target steering mode is stability steering, step S104 further includes: S701. Calculate the required additional yaw moment of each axle based on the proportional-integral closed-loop control method for the current driving information.

[0065] Among them, when the target steering mode is stability steering, the direct yaw moment control method is adopted, with vehicle stability as the control target to control the wheel torque. According to the deviation of the yaw angular velocity, the required additional yaw moment of each axle is determined through the proportional-integral closed-loop control method, as shown in formula (10): (10) In the formula, is the proportional gain, which determines the response intensity to the instantaneous deviation, is the integral gain, which is used to eliminate the steady-state error, is the difference in yaw angular velocity, is the wheelbase of this differential steering axle, is the time variable.

[0066] S702. Obtain the total longitudinal required torque according to the wheelbase of the differential steering axle and the required additional yaw moment.

[0067] Among them, the relationship between the required additional yaw moment and the driving forces on both sides of the same axle is as shown in formula (11): (11) Thus, the total longitudinal required torque is calculated through formula (11) 。

[0068] S703. Perform wheel torque distribution according to the required additional yaw moment and the total longitudinal required torque to obtain the maximum output torque of each axle.

[0069] Among them, the actuator control module performs wheel torque distribution according to the required additional yaw moment and the total longitudinal required torque, and outputs the target driving torque of each wheel to the motor controller, and uses the optimization method to perform torque distribution on the whole vehicle. The specific implementation method is as follows: Step 1. Determine the objective function of the optimization problem as shown in formula (12): (12) Among them, the first objective function represents the tracking target of the total longitudinal torque and the required additional yaw moment, as shown in formula (13): (13) In the formula, , , , is the total longitudinal force required, , is the longitudinal force of the -th axis.

[0070] Among them, the second objective function is the minimum utilization adhesion coefficient function. Take the square of the two-norm of the longitudinal adhesion utilization coefficient, as shown in formula (14): (14) where , are the loads of each wheel.

[0071] Step 2: Determine the constraints of the optimization problem.

[0072] In the differential steering mode, the differential torque generated by the steering angle is used as a constraint condition. The longitudinal forces of the left and right wheels on the -th axis satisfy, as shown in formula (15): (15) In the steady steering mode, the longitudinal forces of the left and right wheels on the -th axis satisfy, as shown in formula (16): (16) At the same time, the driving force of each wheel satisfies the constraints of the maximum and minimum torques of the motor, as shown in formula (17): (17) In the formula, R is the wheel radius, T max is the maximum output torque of the motor under the current working condition.

[0073] S704. Use the quadratic programming solution algorithm to optimize the maximum output torque, obtain the optimal wheel torque, and perform steering control on the multi-axis vehicle according to the optimal wheel torque of each axis.

[0074] Among them, use the quadratic programming solution algorithm to optimize the maximum output torque, obtain the optimal wheel driving force, further obtain the optimal wheel torque, and send the above-obtained optimal wheel torque as the demand target to the drive motor controller for execution and implementation, that is, perform steering control on the multi-axis vehicle according to the optimal wheel torque of each axis.

[0075] In the embodiments of the present invention, aiming at the problems of excessive turning radius of multi-axle vehicles and unstable steering during high-speed driving, the present invention adaptively adjusts the steering mode according to the driving speed and the steering wheel angle requirement, and takes into account the requirements of maneuverability and stability under different driving conditions, effectively improving the comprehensive performance of the vehicle. The integrated steering control system for distributed drive six-axle all-wheel steering vehicles proposed in the embodiments of the present invention is also applicable to multi-axle heavy vehicles with other axle numbers. The embodiments of the present invention utilize common vehicle state information and use the threshold method to decide different steering modes, with high operation efficiency, low system cost, and strong practicability.

[0076] In order to better implement the steering control method for multi-axle vehicles with distributed drive in the embodiments of the present invention, correspondingly, based on the steering control method for multi-axle vehicles with distributed drive, the embodiments of the present invention also provide a steering control device for multi-axle vehicles with distributed drive, as Figure 8 shown. The steering control device 800 for multi-axle vehicles with distributed drive includes: An information acquisition module 801, configured to acquire the current driving information of the multi-axle vehicle when receiving the steering requirement of the multi-axle vehicle; the current driving information includes the driving speed and the current yaw angular velocity; A stability judgment module 802, configured to judge the stability of the multi-axle vehicle according to the current yaw angular velocity when the driving speed is greater than the preset speed, obtain the driving state, and determine the target steering mode according to the driving state; the target steering mode is stability steering or steering system steering; A steering judgment module 803, configured to judge the steering requirement when the driving speed is not greater than the preset speed, obtain the steering state; and determine the target steering mode according to the steering state; the target steering mode is differential integrated steering or steering system steering; A steering control module 804, configured to perform steering control on the multi-axle vehicle according to the target steering mode and the distributed drive.

[0077] The above-mentioned steering control device 800 for multi-axle vehicles with distributed drive can implement the technical solutions described in the embodiments of the above-mentioned steering control method for multi-axle vehicles with distributed drive. The specific implementation principles of the above-mentioned modules or units can be referred to the corresponding content in the embodiments of the above-mentioned steering control method for multi-axle vehicles with distributed drive, which will not be elaborated here.

[0078] The above has introduced in detail the steering control method and device for multi-axle vehicles with distributed drive provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A steering control method for a multi-axis vehicle with distributed drive, characterized in that, Including: When receiving a steering demand of a multi-axle vehicle, obtaining the current driving information of the multi-axle vehicle; The current driving information includes a driving speed and a current yaw rate; When the driving speed is greater than a preset speed, judging the stability of the multi-axle vehicle according to the current yaw rate to obtain a driving state, and determining a target steering mode according to the driving state; The target steering mode is a stability steering or a steering system steering; When the driving speed is not greater than the preset speed, judging the steering demand to obtain a steering state; And determining a target steering mode according to the steering state; The target steering mode is a differential integrated steering or a steering system steering; Steering control of the multi-axle vehicle is performed according to the target steering mode and distributed drive.

2. The steering control method for a multi-axle vehicle with distributed drive according to claim 1, characterized in that, The judging the stability of the multi-axle vehicle according to the current yaw rate to obtain a driving state includes: Obtaining a yaw rate difference according to the current yaw rate and a preset linear yaw rate; Judging whether an absolute value of the yaw rate difference is greater than a preset difference; If so, determining the driving state of the multi-axle vehicle as an unstable state; If not, determining the driving state of the multi-axle vehicle as a stable state.

3. The steering control method for a multi-axis vehicle with distributed drive according to claim 2, characterized in that, The determining a target steering mode according to the driving state includes: When the driving state is the unstable state, determining the target steering mode as the stability steering; When the driving state is the stable state, determining the target steering mode as the steering system steering.

4. The steering control method for a multi-axle vehicle with distributed drive according to claim 1, characterized in that The steering demand includes a steering wheel angle; the judging the steering demand to obtain a steering state includes: Judging whether the steering wheel angle is greater than or equal to a preset angle; If so, the steering state of the multi-axle vehicle is a large steering state; If so, the steering state of the multi-axle vehicle is a small steering state.

5. The steering control method for a multi-axle vehicle with distributed drive according to claim 4, characterized in that, The determining a target steering mode according to the steering state includes: When the steering state is the large steering state, determining the target steering mode as the differential integrated steering; When the steering state is the small steering state, determining the target steering mode as the steering system steering.

6. The steering control method for a multi-axle vehicle with distributed drive according to claim 5, characterized in that, The method further includes: When the target steering mode is the steering system steering, performing steering control on the multi-axle vehicle according to the steering system steering.

7. The steering control method for a multi-axle vehicle with distributed drive according to claim 6, characterized in that, The performing steering control on the multi-axle vehicle according to the steering system steering includes: Obtaining the wheelbase of each axle on the multi-axle vehicle, and determining a steering center and a first-axle wheel angle; Determining a proportionality coefficient of each axle according to all wheelbases; Calculating the proportionality coefficient of each axle one by one according to the first-axle wheel angle to obtain the wheel angle of each axle; Performing steering control on the left and right wheels of the corresponding axle on the multi-axle vehicle according to the wheel angle.

8. The steering control method for a multi-axle vehicle with distributed drive according to claim 1, characterized in that, The current driving information includes a tire rolling radius, a single-axle return torque, a single-axle frictional resistance torque, the moment of inertia of the left wheel of each axle about the kingpin, an electric wheel reducer transmission ratio, a kingpin offset at the wheel center, a kingpin inclination angle, and a kingpin caster angle; When the target steering mode is the differential integrated steering, the steering control of the multi-axis vehicle according to the target steering mode and distributed drive includes: Calculating the tire rolling radius, the moment of inertia, the transmission ratio of the electric wheel reducer, the kingpin offset, the kingpin inclination and the caster angle of each axis to obtain a first coefficient; Calculating the tire rolling radius, the single axle self-aligning torque, the single axle frictional torque, the transmission ratio of the electric wheel reducer, the kingpin offset, the kingpin inclination and the caster angle of each axis to obtain a second coefficient; Obtaining the left wheel angle of each axis according to the first coefficient and the second coefficient; Obtaining the mechanical system steering angle of each axis according to the left wheel angle and a preset proportional coefficient; Obtaining the actual wheel angle of each axis according to the mechanical system steering angle and the left wheel angle, and performing steering control on the multi-axis vehicle according to the actual wheel angle of each axis.

9. The steering control method for a multi-axis vehicle with distributed drive according to claim 1, characterized in that, The current driving information further includes the wheelbase of the differential steering axis; When the target steering mode is the stability steering, the steering control of the multi-axis vehicle according to the target steering mode and distributed drive includes: Calculating the required additional yaw moment of each axis based on the proportional-integral closed-loop control method for the current driving information; Obtaining the total longitudinal required torque according to the wheelbase of the differential steering axis and the required additional yaw moment; Performing wheel torque distribution according to the required additional yaw moment and the total longitudinal required torque to obtain the maximum output torque of each axis; Optimizing the maximum output torque by using a quadratic programming solution algorithm to obtain the optimal wheel torque, and performing steering control on the multi-axis vehicle according to the optimal wheel torque of each axis.

10. A steering control device for a multi-axle vehicle with distributed drive, characterized in that, Including: An information acquisition module, configured to acquire the current driving information of the multi-axis vehicle when receiving a steering demand of the multi-axis vehicle; The current driving information includes the driving speed and the current yaw angular velocity; A stability judgment module, configured to judge the stability of the multi-axis vehicle according to the current yaw angular velocity when the driving speed is greater than a preset speed, obtain a driving state, and determine a target steering mode according to the driving state; The target steering mode is the stability steering or the steering system steering; A steering judgment module, configured to judge the steering demand when the driving speed is not greater than the preset speed to obtain a steering state; And determining a target steering mode according to the steering state; The target steering mode is the differential integrated steering or the steering system steering; A steering control module, configured to perform steering control on the multi-axis vehicle according to the target steering mode and distributed drive.

Images