CN209739155U - electronic round of system of electronic round of line control four-wheel initiative steering - Google Patents

Abstract

The utility model discloses a wire-controlled four-wheel active steering electric wheel system, which comprises a steering wheel, a steering wheel angle sensor, two steering motors, two motor control units, a motor failure detection device, and two rack and pinion steering gears , two steering tie rods, four wheels and hub motors, yaw rate sensor, vehicle speed sensor, laser radar, vehicle camera and vehicle control unit. During driving, the vehicle electronic control unit collects the steering wheel angle and yaw in real time. Angular velocity, vehicle speed, laser radar signal and on-board camera signal, through the designed controller, calculate the front and rear wheel rotation angle and the output torque of the four hub motors and transmit these signals to each motor controller, and the motor controller sends a current signal to the motor to complete Steering operation; the utility model can effectively solve the problem of fault tolerance of the wire-controlled four-wheel steering system and improve the safety of the vehicle.

Description

A wire-controlled four-wheel active steering electric wheel system

technical field

The utility model relates to the field of vehicle active control, in particular to a wire-controlled four-wheel active steering electric wheel system.

Background technique

Steering system, as one of the four major systems of the automobile chassis, greatly affects the driving safety and handling stability of the automobile. The development history of the steering system is the earliest mechanical steering system, but this kind of steering system has a complicated structure and a fixed transmission ratio, which is not conducive to the realization of the lightweight design of the car and the safe and stable driving of the driver. The steering-by-wire system cancels the mechanical connection between the steering wheel and the steering wheel, and uses sensors to collect the driver's steering intention and then send it to the steering actuator to complete the steering. Compared with the traditional mechanical steering system, the steering-by-wire system has the advantages of fast response, flexible steering, reduced vehicle weight, and space saving.

At the same time, with the development of automobile technology, the active safety of automobiles has been paid more and more attention. Automobile four-wheel steering is one of the important methods to improve automobile active safety. The wire-controlled four-wheel steering system uses the wire-controlled steering motor to drive the front and rear wheels to rotate. Compared with the front-wheel steering system, the advantage of the four-wheel steering system is that the front and rear wheels can rotate independently, which reduces the steering stress. The side slip angle of the center of mass improves the flexibility of the car at low-speed steering and the stability of high-speed steering, and improves the handling stability and driving safety of the car.

However, compared with the traditional mechanical steering system, the biggest disadvantage of the steer-by-wire system is its poor reliability, and the steering system may lose control of the steering, which is extremely dangerous for cars driving on the road.

Most of the existing fault-tolerant controls on steer-by-wire focus on the fault-tolerance of the steer-by-wire system. For example, the dual-motor redundant steering-by-wire system solves the problem of fault tolerance of the steering-by-wire system through motor backup. After one motor fails, the other motor can be used to steer, but this will increase manufacturing costs and take up more space. The system is more complex. And the fault-tolerant control does not consider the driver's emergency response and path tracking after the fault occurs, which may cause the driver to overreact and the vehicle to deviate from the target path.

Utility model content

In view of the above problems, the utility model provides a four-wheel-by-wire active steering electric wheel system and a steering fault-tolerant control method thereof. It aims to make full use of the advantages of the steering actuator redundancy of the four-wheel steer-by-wire electric wheel system and combine the path tracking control technology to achieve the goal that the steer-by-wire system can still track the path normally according to the driver's intention after the fault occurs, and reduce the driving force after the fault occurs. The psychological burden and operational burden of the driver can be reduced, and the safety and stability of the vehicle can be improved. In addition, compared with the traditional dual-motor redundant steering-by-wire system, it reduces vehicle weight and production cost, and provides a basis for the application of intelligent driving assistance systems.

In order to achieve the above object, the utility model proposes the following technical solutions to achieve:

A control-by-wire four-wheel active steering electric wheel system includes: a vehicle body and a steering wheel 9 placed inside the vehicle body, a steering wheel angle sensor 10, a rear wheel steering motor 4, a front wheel steering motor 14, a rear wheel steering motor controller 5, Front wheel steering motor controller 13, rear wheel motor fault detection device 2, front wheel motor fault detection device 16, rear rack and pinion steering gear 3, front rack and pinion steering gear 15, rear wheel steering tie rod 6, front Wheel steering tie rod 12, first hub motor 1, second hub motor 7, third hub motor 11, fourth hub motor 17, yaw rate sensor 19, center of mass sideslip angle sensor 20, vehicle speed sensor 21, laser radar 22 , vehicle camera 23, vehicle electronic control unit 8 (ECU) and CAN bus 18;

Wherein, the rear wheel steering motor 4 is located at the rear axle of the vehicle, which is respectively connected with the rear rack and pinion steering gear 3, the rear wheel steering motor controller 5, and the rear wheel motor failure detection device 2, and the rear rack and pinion steering gear 3 is located at On the rear wheel steering tie rod 6, the two ends of the rear wheel steering tie rod 6 are respectively provided with a first hub motor 1 and a second hub motor 7, and both the first hub motor 1 and the second hub motor 7 are connected to the corresponding wheels; The steering motor 4 drives the rear rack-and-pinion steering gear 3 to move, and then drives the rear steering tie rod 6 to drive the first hub motor 1 and the second hub motor 7, thereby driving the corresponding wheels to rotate and realizing the steering of the wheels;

The front wheel steering motor 14 is located at the front axle of the vehicle, and it is respectively connected with the front wheel steering gear 15, the front wheel steering motor controller 13, and the front wheel motor failure detection device 16, and the front wheel steering gear 15 is located at the front wheel. On the steering tie rod 12, a third wheel hub motor 11 and a fourth wheel hub motor 17 are respectively provided at both ends of the front wheel steering tie rod 12, and both the third wheel hub motor 11 and the fourth wheel hub motor 17 are connected to the corresponding wheels; the front wheel steering motor 14 drives the front rack and pinion steering gear 15 to move, and then drives the front steering tie rod 12 to drive the third hub motor 11 and the fourth hub motor 17 and drive the corresponding wheels to realize the steering of the vehicle;

The steering wheel 9 is located in the vehicle body, and the steering wheel angle sensor 10 is connected to the steering wheel 9 through the steering wheel steering column to obtain the steering wheel angle signal;

The front wheel motor fault detection device 16 is connected with the CAN bus 18, and is used to detect the fault of the front wheel steering motor 14 and sends the fault signal to the CAN bus 18 through the CAN transceiver; the rear wheel motor fault detection device 2 is connected with the CAN bus 18 , for detecting the fault of the rear wheel steering motor 4 and sending the fault signal to the CAN bus 18 through the CAN transceiver;

The yaw rate sensor 19, the center of mass side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the on-board camera 23 are all arranged on the vehicle body, and are respectively used to obtain the vehicle yaw rate signal, the center of mass side slip angle signal, the vehicle speed signal, The road obstacle status signal and the lane status signal; the yaw rate sensor 19, the center of mass side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the vehicle camera 23 are connected to the CAN bus 18 respectively, and the received signals are transmitted through the CAN transceiver. The received signal is sent to the CAN bus 18;

Rear-wheel steering motor controller 5 and front-wheel steering motor controller 13 are connected with CAN bus 18 respectively, receive the signal that CAN bus 18 transmits;

The vehicle electronic control unit 8 is connected to the CAN bus 18 through the CAN transceiver, and receives signals obtained by the CAN bus 18 through the yaw rate sensor 19, the side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the vehicle camera 23; The vehicle electronic control unit 8 is also connected with the steering wheel angle sensor 10, and obtains the steering wheel angle signal; the vehicle electronic control unit 8 calculates the front and rear wheel angles and the four wheel angles through the built-in controller according to the steering wheel angle signal transmitted by the steering wheel angle sensor 10. The drive torque is sent to the CAN bus 18;

The rear wheel steering motor controller 5, the front wheel steering motor controller 13, the first hub motor 1, the second hub motor 7, the third hub motor 11, and the fourth hub motor 17 are respectively provided with CAN transceivers, and the rear wheel steering The motor controller 5, the front wheel steering motor controller 13, the first hub motor 1, the second hub motor 7, the third hub motor 11, and the fourth hub motor 17 are respectively connected to the CAN bus 18 through their respective CAN transceivers, Receive the target rotation angle and target torque of the steering motor sent by the vehicle electronic control unit 8 through the CAN bus 18 .

The rear wheel steering motor controller 5 generates a corresponding current according to the angle signal obtained from the CAN bus 18 to control the operation of the rear wheel steering motor 4, and the first hub motor 1 and the second hub motor 7 are based on the torque signal obtained from the CAN bus 18 Generate corresponding current to control hub motor and corresponding wheel work.

The front wheel steering motor controller 13 generates corresponding currents to control the front wheel steering motor 14 according to the rotation angle signals obtained from the CAN bus 18, and the third hub motor 11 and the fourth hub motor 17. The torque signal obtained by the bus 18 generates a corresponding current to control the in-wheel motor and the corresponding wheel to work.

The vehicle electronic control unit 8 is an ECU module, which includes a path planning module, a driver module, a stability control module and a fault-tolerant control module connected in sequence.

In the present invention, the term "front wheel" refers to the wheel corresponding to the third hub motor and the fourth hub motor; the term "rear wheel" refers to the wheel corresponding to the first hub motor and the second hub motor.

Furthermore, in the control-by-wire four-wheel active steering electric wheel system provided by the utility model, the rear wheel steering motor 4 and the front wheel steering motor 14 are both permanent magnet brushless DC motors.

The utility model also provides a steering fault-tolerant control method for the above-mentioned wire-controlled four-wheel active steering electric wheel system: in the vehicle electronic control unit 18, the stability control module and the fault-tolerant control module are based on the motor failure detection device 16 to the vehicle electronic control unit. The signal sent by the control unit 18 switches the controller; when the front wheel steering motor 14 does not fail, the motor failure detection device 16 sends a low level to the vehicle electronic control unit 18, and the control unit operates a stability control module to implement a stability control module. Control strategy: when the front wheel steering motor 14 fails, the motor failure detection device 16 sends a high level to the vehicle electronic control unit 18, and the control unit runs the fault-tolerant control module to implement the fault-tolerant control strategy.

The above stability control strategy includes the following steps:

Step 1), the driver turns the steering wheel, the vehicle electronic control unit 18 obtains the steering wheel angle δ _sw through the steering wheel angle sensor, and obtains the ideal yaw rate w ^* and the ideal center of mass sideslip angle β ^* through formula (1):

In formulas (1)-(3), G _w is the set variable transmission ratio coefficient, v _x is the vehicle speed, L is the vehicle wheelbase, K _s is the yaw rate gain coefficient (generally 15-20), K is the stability factor, m is the vehicle mass, k ₁ and k ₂ are the cornering stiffness of the front and rear wheels of the vehicle respectively;

Step 2), the stability control module calculates the yaw rate deviation w _d , the center of mass sideslip angle deviation β _d

The difference between the ideal yaw rate w ^* and the ideal center-of-mass sideslip angle β ^* and the actual yaw rate w and the side-slip angle β measured by the sensor is:

w is the actual yaw rate measured by the sensor, β is the side slip angle of the center of mass actually measured by the sensor, w _d is the deviation of the yaw rate, and β _d is the deviation of the side slip angle of the center of mass;

Substituting formula (4) into formula (5) of the structural singular value μ control algorithm and into the stability control module to calculate the front wheel rotation angle _δf and the rear wheel rotation angle _δr ;

Described fault-tolerant control strategy comprises the following steps:

step 1:

1.1 If the front wheel steering motor fails

The fault-tolerant control module calculates the rear wheel rotation angle δ _r according to the set transmission ratio i _r between the rear wheels and the steering wheel;

Among them, δ _sw represents the steering wheel angle; δ _r represents the rear wheel angle; the value range of if _is between -15 and -20;

1.2 If the rear wheel steering motor fails

The fault-tolerant control module calculates the rear wheel rotation angle δ _f according to the set transmission ratio i _f between the front wheels and the steering wheel:

Among them, δ _sw represents the steering wheel angle; δ _f represents the rear wheel angle. The value range of if is between _15-20 ;

Step 2:

The path planning module in the vehicle electronic control unit 18 receives the laser radar signal and the on-board camera signal to generate the expected path Y ^* according to the built-in path planning algorithm and sends the expected path signal to the fault-tolerant control module;

The above path planning algorithm is a conventional algorithm in this field, as disclosed in the document "An Linfang, Chen Tao, Cheng Aiguo, et al. Intelligent Vehicle Path Planning Simulation Based on Artificial Potential Field Algorithm [J]. Automotive Engineering, 2017." path planning algorithm;

Step 3:

The driver module in the vehicle electronic control unit 18 is based on the difference between the expected path Y ^* and the actual path Y signal:

ΔY=Y ^* -Y (8)

According to the built-in single-point preview driver model algorithm (9), the expected driver's angle δ _fd of the steering wheel is obtained and sent to the fault-tolerant control module;

Among them, δ _fd is the expected steering wheel angle of the driver, G _h is the steering proportional coefficient, τ _L is the differential time; τ _d1 is the operation delay time; τ _d2 is the driver's reaction delay time;

Step 4:

The vehicle electronic control unit 18 transmits the vehicle yaw rate w and vehicle speed v signals measured by the yaw rate sensor and the vehicle speed sensor to the fault-tolerant control module;

Step 5:

The fault-tolerant control module obtains the target drive torques T ₁ , T ₂ , T ₃ of the vehicle's four in-wheel motors according to the driver's steering wheel angle δ _sw , the expected path Y ^* , the expected driver's steering wheel angle δ _fd and the actual state of the vehicle. T4 _;

Step 6:

The vehicle electronic control unit 18 sends the front and rear wheel rotation angle signals _δf or _δr and T ₁ , T ₂ , T ₃ , T ₄ calculated according to the above steps 1-6 to the front wheel respectively from the vehicle electronic control unit 18 In the steering motor controller or the rear wheel steering motor controller and the four in-wheel motor controllers, the motor controller generates corresponding current to drive the corresponding motor to rotate to realize the driving of the vehicle.

Compared with the prior art, the utility model has the following beneficial effects:

1. This utility model designs a four-wheel-by-wire active steering electric wheel system, which can realize active steering of the front and rear wheels and independent drive of the four wheels. Equipped with a steering system fault detection device, it can detect steering system faults in real time. Equipped with laser radar and on-board camera, it can realize path recognition and planning. The system has simple structure, easy operation, low cost and easy realization.

2. The utility model is equipped with two steering controllers: a stability control module and a fault-tolerant control module. Stability control under normal working conditions and fault-tolerant control under fault working conditions can be realized. At the same time, this system can realize path identification and planning. After a fault occurs, the system can still track the target of the path normally according to the driver's intention, which reduces the driver's psychological burden and operational burden after the fault occurs, and improves the safety and stability of the vehicle. .

Description of drawings

Fig. 1 is a structural diagram of the wire-controlled four-wheel steering electric wheel system provided by the utility model;

Fig. 2 is a schematic diagram of a fault-tolerant control strategy;

Figure 3 is a schematic diagram of a fault-tolerant control strategy.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in detail:

In the following embodiments, the vehicle electronic control unit 18 (that is, the ECU) selects the EDC17CP14/5/P680 vehicle ECU produced by BOSCH Company.

Example 1

As shown in Figure 1, the utility model designs a four-wheel active steering electric wheel system on the basis of the existing steering-by-wire system. There are two types of steering controllers built into the central controller: a stability control module and a fault-tolerant control module. Under normal working conditions, the stability control module works, and the front and rear wheel angles are calculated by the central controller based on the steering wheel angle, yaw rate sensor, center of mass side slip angle sensor, and vehicle speed sensor signals and sent to the front and rear wheel angles. In the steering motor controller, the front and rear wheel steering motor controllers generate corresponding currents to control the corresponding motors to rotate. The fault-tolerant control module works under fault conditions. According to the fault information obtained from the steering motor fault detection device, the central controller selects the corresponding fault-tolerant control module and combines the steering wheel angle, yaw rate, side slip angle, vehicle speed, laser radar and vehicle The camera signal calculates the front and rear wheel rotation angles and the driving torque of the four hub motors and sends them to the front and rear wheel steering motor controllers and the hub motor controllers, and then the front and rear wheel steering motor controllers and the hub motor controllers correspond The corresponding current is generated to control the rotation of the motor.

Specifically, the steer-by-wire electric wheel system provided in this embodiment includes: steering wheel 9, steering wheel angle sensor 10, rear wheel steering motor 4, front wheel steering motor 14, rear wheel steering motor controller 5, front wheel steering Motor controller 13, rear wheel motor fault detection device 2, front wheel motor fault detection device 16, rear rack and pinion steering gear 3, front rack and pinion steering gear 15, rear wheel steering tie rod 6, front wheel steering Tie rod 12, first hub motor 1, second hub motor 7, third hub motor 11, fourth hub motor 17, yaw rate sensor 19, center of mass side slip angle sensor 20, vehicle speed sensor 21, laser radar 22, vehicle camera 23. Vehicle electronic control unit 8 (ECU) and CAN bus 18;

Wherein, the rear wheel steering motor 4 is located at the rear axle of the vehicle, which is respectively connected with the rear rack and pinion steering gear 3, the rear wheel steering motor controller 5, and the rear wheel motor failure detection device 2, and the rear rack and pinion steering gear 3 is located at On the rear wheel steering tie rod 6, the two ends of the rear wheel steering tie rod 6 are respectively provided with a first hub motor 1 and a second hub motor 7, and both the first hub motor 1 and the second hub motor 7 are connected to the corresponding wheels; The steering motor 4 drives the rear rack-and-pinion steering gear 3 to move, and then drives the rear steering tie rod 6 to drive the first hub motor 1 and the second hub motor 7, thereby driving the corresponding wheels to rotate and realizing the steering of the wheels;

The front wheel steering motor 14 is located at the front axle of the vehicle, and it is respectively connected with the front wheel steering gear 15, the front wheel steering motor controller 13, and the front wheel motor failure detection device 16, and the front wheel steering gear 15 is located at the front wheel. On the steering tie rod 12, a third wheel hub motor 11 and a fourth wheel hub motor 17 are respectively provided at both ends of the front wheel steering tie rod 12, and both the third wheel hub motor 11 and the fourth wheel hub motor 17 are connected to the corresponding wheels; the front wheel steering motor 14 drives the front rack and pinion steering gear 15 to move, and then drives the front steering tie rod 12 to drive the third hub motor 11 and the fourth hub motor 17 and drive the corresponding wheels to realize the steering of the vehicle;

The steering wheel 9 is located in the vehicle body, and the steering wheel angle sensor 10 is connected to the steering wheel 9 through the steering wheel steering column to obtain the steering wheel angle signal;

The front wheel motor fault detection device 16 is connected with the CAN bus 18, and is used to detect the fault of the front wheel steering motor 14 and sends the fault signal to the CAN bus 18 through the CAN transceiver; the rear wheel motor fault detection device 2 is connected with the CAN bus 18 , for detecting the fault of the rear wheel steering motor 4 and sending the fault signal to the CAN bus 18 through the CAN transceiver;

The yaw rate sensor 19, the center of mass side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the on-board camera 23 are all arranged on the vehicle body, and are respectively used to obtain the vehicle yaw rate signal, the center of mass side slip angle signal, the vehicle speed signal, The road obstacle status signal and the lane status signal; the yaw rate sensor 19, the center of mass side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the vehicle camera 23 are connected to the CAN bus 18 respectively, and the received signals are transmitted through the CAN transceiver. The received signal is sent to the CAN bus 18;

Rear-wheel steering motor controller 5 and front-wheel steering motor controller 13 are connected with CAN bus 18 respectively, receive the signal that CAN bus 18 transmits;

The vehicle electronic control unit 8 is connected to the CAN bus 18 through the CAN transceiver, and receives signals obtained by the CAN bus 18 through the yaw rate sensor 19, the side slip angle sensor 20, the vehicle speed sensor 21, the laser radar 22, and the vehicle camera 23; The vehicle electronic control unit 8 is also connected with the steering wheel angle sensor 10, and obtains the steering wheel angle signal; the vehicle electronic control unit 8 calculates the front and rear wheel angles and the four wheel angles through the built-in controller according to the steering wheel angle signal transmitted by the steering wheel angle sensor 10. The drive torque is sent to the CAN bus 18;

The rear wheel steering motor controller 5, the front wheel steering motor controller 13, the first hub motor 1, the second hub motor 7, the third hub motor 11, and the fourth hub motor 17 are respectively provided with CAN transceivers, and the rear wheel steering The motor controller 5, the front wheel steering motor controller 13, the first hub motor 1, the second hub motor 7, the third hub motor 11, and the fourth hub motor 17 are respectively connected to the CAN bus 18 through their respective CAN transceivers, Receive the target rotation angle and target torque of the steering motor sent by the vehicle electronic control unit 8 through the CAN bus 18 .

The rear wheel steering motor controller 5 generates a corresponding current according to the angle signal obtained from the CAN bus 18 to control the operation of the rear wheel steering motor 4, and the first hub motor 1 and the second hub motor 7 are based on the torque signal obtained from the CAN bus 18 Generate corresponding current to control hub motor and corresponding wheel work.

The front wheel steering motor controller 13 generates corresponding currents to control the front wheel steering motor 14 according to the rotation angle signals obtained from the CAN bus 18, and the third hub motor 11 and the fourth hub motor 17. The torque signal obtained by the bus 18 generates a corresponding current to control the in-wheel motor and the corresponding wheel to work.

The vehicle electronic control unit 8 is an ECU module, which includes a path planning module, a driver module, a stability control module and a fault-tolerant control module connected in sequence.

In this embodiment, both the rear wheel steering motor 4 and the front wheel steering motor 14 are permanent magnet brushless DC motors.

This embodiment also provides a steering fault-tolerant control method for the above-mentioned four-wheel active steering electric wheel system by wire:

The above-mentioned vehicle electronic control unit 18 has two built-in controllers, a stability control module and a fault-tolerant control module, both of which switch the controllers according to the signal sent by the motor fault detection device 16 to the vehicle electronic control unit 18; the front wheel steering motor 14 When no failure occurs, the motor failure detection device 16 sends a low level to the vehicle electronic control unit 18, and the control unit operates a stability control module to implement a stability control strategy; when the front wheel steering motor 14 fails, the motor failure detection device 16 sends a high level to the vehicle electronic control unit 18, and the control unit runs the fault-tolerant control module to implement a fault-tolerant control strategy.

As shown in accompanying drawing 2, described stability control strategy comprises the following steps:

Step 1), the driver turns the steering wheel, the electronic control unit 18 of the vehicle obtains the steering wheel angle δ _sw through the steering wheel angle sensor, and obtains the ideal yaw rate w ^* and the ideal center-of-mass sideslip angle β ^* through formula (1):

In formulas (1)-(3), G _w is the set variable transmission ratio coefficient, v _x is the vehicle speed, L is the vehicle wheelbase, K _s is the yaw rate gain coefficient (generally 15-20), K is the stability factor, m is the vehicle mass, k ₁ and k ₂ are the cornering stiffness of the front and rear wheels of the vehicle respectively;

Step 2), the stability control module calculates the yaw rate deviation w _d and the center of mass sideslip angle deviation β _d :

The difference between the ideal yaw rate w ^* and the ideal center-of-mass sideslip angle β ^* and the actual yaw rate w and the side-slip angle β measured by the sensor is:

w is the actual yaw rate measured by the sensor, β is the side slip angle of the center of mass actually measured by the sensor, w _d is the deviation of the yaw rate, and β _d is the deviation of the side slip angle of the center of mass.

Substituting formula (4) into the stability control module obtained by the structural singular value μ control algorithm (5), calculate the front wheel rotation angle δ _f and the rear wheel rotation angle δ _r ;

As shown in accompanying drawing 3, described fault-tolerant control strategy comprises the following steps:

step 1:

1.1 If the front wheel steering motor fails

The fault-tolerant control module calculates the rear wheel rotation angle δ _r according to the set transmission ratio i _r between the rear wheels and the steering wheel;

Among them, δ _sw represents the steering wheel angle; δ _r represents the rear wheel angle; the value range of if _is between -15 and -20;

1.2 If the rear wheel steering motor fails

The fault-tolerant control module calculates the rear wheel rotation angle δ _f according to the set transmission ratio i _f between the front wheels and the steering wheel:

Among them, δ _sw represents the steering wheel angle; δ _f represents the rear wheel angle. The value range of if is between _15-20 ;

Step 2:

The path planning module in the vehicle electronic control unit 18 receives the laser radar signal and the on-board camera signal to generate the expected path Y* according to the built-in path planning algorithm and sends the expected path signal to the fault-tolerant control module;

For the path planning algorithm used in this embodiment, please refer to the document "An Linfang, Chen Tao, Cheng Aiguo, et al. Intelligent Vehicle Path Planning Simulation Based on Artificial Potential Field Algorithm [J]. Automotive Engineering, 2017." algorithm;

Step 3:

The driver module in the vehicle electronic control unit 18 is based on the difference between the expected path Y* and the actual path Y signal:

ΔY=Y*-Y(8)

According to the built-in single-point preview driver model algorithm (9), the desired driver's angle δ _fd of the steering wheel is obtained and sent to the fault-tolerant control module K;

In formula (9), δ _fd is the expected steering wheel angle of the driver, G _h is the steering proportional coefficient, τ _L is the differential time; τ _d1 is the operation delay time; τ _d2 is the driver’s reaction delay time;

Step 4:

The vehicle yaw rate w and vehicle speed v signals measured by the yaw rate sensor and the vehicle speed sensor are transmitted to the fault-tolerant control module;

Step 5:

The fault-tolerant control module obtains the target drive torques T ₁ , T ₂ , T ₃ of the vehicle's four in-wheel motors according to the driver's steering wheel angle δ _sw , the expected path Y*, the expected driver's steering wheel angle δ _fd and the actual state of the vehicle. T4 _;

Step 6:

The vehicle electronic control unit 18 sends the front and rear wheel rotation angle signals _δf or _δr and T ₁ , T ₂ , T ₃ , T ₄ calculated according to the above steps 1-6 to the front wheel respectively from the vehicle electronic control unit 18 In the steering motor controller or the rear wheel steering motor controller and the four in-wheel motor controllers, the motor controller generates corresponding current to drive the corresponding motor to rotate to realize the driving of the vehicle.

Claims (2)

1. A four-wheel-by-wire active steering electric wheel system, comprising a car body, characterized in that the four-wheel-by-wire active steering electric wheel system comprises: a steering wheel arranged inside the car body, a rear wheel steering motor, a front wheel Rear wheel steering motor, vehicle electronic control unit, CAN bus; The steering wheel is connected with a steering wheel angle sensor; The rear wheel steering motor is respectively connected to the rear wheel steering gear, the rear wheel steering motor controller, and the rear wheel motor fault detection device; the rear wheel rack steering gear is located on the rear wheel steering tie rod , the two ends of the rear wheel steering tie rod are respectively provided with a first hub motor and a second hub motor; the first hub motor and the second hub motor are respectively connected to the corresponding wheels; The front wheel steering motor is respectively connected with the front rack and pinion steering gear, the front wheel steering motor controller, and the front wheel motor fault detection device; the front rack and pinion steering gear is located on the front wheel steering tie rod, and the front wheel A third wheel hub motor and a fourth wheel hub motor are installed at both ends of the tie rod respectively, and the third wheel hub motor and the fourth wheel hub motor are respectively connected to the corresponding wheels; The vehicle electronic control unit includes a path planning module, a driver module, a stability control module and a fault-tolerant control module; The fault detection device for the front wheel motor, the fault detection device for the rear wheel motor, and the vehicle electronic control unit are all connected to the CAN bus respectively; The car body is also respectively provided with a yaw rate sensor, a side slip angle sensor, a vehicle speed sensor, a laser radar, and an on-board camera, and they are respectively connected to the CAN bus; The rear wheel steering motor controller, the front wheel steering motor controller, the first hub motor, the second hub motor, the third hub motor, and the fourth hub motor are all equipped with CAN transceivers, and the rear wheel steering motor controller, front wheel The steering motor controller, the first hub motor, the second hub motor, the third hub motor, and the fourth hub motor are respectively connected to the CAN bus through their respective CAN transceivers. 2. The control-by-wire four-wheel active steering electric wheel system according to claim 1, wherein the rear wheel steering motor and the front wheel steering motor are both permanent magnet brushless DC motors.