CN109733464B - Active Fault Tolerance and Fault Mitigation System Based on Steering by Wire Dual Motors and Its Control Method - Google Patents

Abstract

This application discloses an active fault-tolerant and fault-mitigating system based on steer-by-wire dual motors and its mode switching control method. The system includes the acquisition unit, steering wheel assembly, ECU control module, and front wheel steering Assembly, fault-tolerant controller; its control method includes that the acquisition unit transmits the collected vehicle signals to the ECU control module, and then selects the corresponding The compensation strategy of this application acts on the rack mechanism; the system and method provided by this application can switch between the active fault tolerance and fault mitigation modes according to different fault conditions of the faulty motor, so as to realize the optimal control of the real-time performance of the automobile, thereby ensuring the Drivability and high performance under automotive field failure conditions.

Description

Active Fault Tolerance and Fault Mitigation System Based on Steering by Wire Dual Motors and Its Control Method

technical field

The invention relates to the technical field of steer-by-wire systems and fault-tolerant control systems, in particular to the steer-by-wire dual-motor fault-tolerant function for switching working modes under different fault conditions of the steer-by-wire dual motors and ensuring good vehicle driving performance and battery life. System and mode switching control method thereof.

Background technique

At present, hardware redundancy and software redundancy are commonly used for vehicle fault tolerance. Among them, hardware redundancy can be replaced when the car breaks down, and the faulty hardware is replaced with new hardware to ensure the normal driving of the car; but the hardware redundancy method will increase the economic cost of the car, without considering the cost of the car. Real-time fault conditions cannot achieve real-time optimal allocation of vehicles, which is a relatively conservative fault-tolerant method. Software redundancy is a way to reduce the development cost of hardware redundancy through software redundancy. The core method of software redundancy is the method of active fault tolerance. This method uses the identification and derivation of other sets of correct data, and the approximate correctness of the derivation is used. The wrong data measured due to the failure of sensors, etc. can be replaced by the data, which can solve the cascading error caused by the failure of some sensors, and can greatly reduce the development cost of fault tolerance. However, some actuators are not suitable to be completely replaced by active fault-tolerant methods, because the failure of some actuators will not only cause data errors, but also directly affect the execution effect of the car. For example, the executive motor of the steering by wire of the car, the single steering executive motor fails, and only the active fault-tolerant method cannot replace the steering effect caused by the failure of the steering motor. Normal driving and optimal control.

The active fault-tolerant method alone cannot solve the actuator failure problem, and the hardware redundancy method alone or the combination of hardware redundancy and active fault-tolerant method cannot solve the real-time optimization problem of vehicle driving, which will cause a waste of faulty actuator resources.

Contents of the invention

Aiming at the existing fault-tolerant concept and the deficiencies of the prior art, the present invention proposes a new type of fault-tolerant concept-fault mitigation, and based on this concept, provides an active fault-tolerant and fault-link system and its mode based on steering-by-wire dual-execution motors The switching method, on the basis of ensuring safety, greatly improves the safety, reliability, and real-time superiority of the system through the combination of hardware redundancy, active fault tolerance and fault mitigation, and realizes the real-time superiority of the vehicle. The perfect integration of safety and reliability solves the problem that the car cannot run or the performance drops sharply in the case of a single motor failure, and solves the problem of hardware redundancy and active fault tolerance technology directly isolating the faulty motor, which is caused by too conservative methods The problem of motor performance waste also solves the problem that the real-time optimal performance of the car cannot be realized according to the type of car failure during the driving process.

The present invention is achieved through the following technical solutions:

First, the present invention provides an active fault-tolerant and fault-mitigating system based on steer-by-wire dual motors. The system includes: an acquisition unit, a steering wheel assembly, an ECU control module, and a dual-machine execution unit;

Wherein, the acquisition unit is respectively connected with the ECU control module, the steering wheel assembly, and the dual-machine execution unit; the acquisition unit includes a steering wheel angle sensor 4, a steering wheel torque sensor 5, a front wheel angle sensor 9, a front wheel torque sensor 12, The vehicle speed sensor 19 and the yaw rate sensor collect the sensor of the vehicle state; and transmit the collected signals or instructions to the ECU control module, the steering wheel assembly, and the dual-machine execution unit, specifically: the collection unit real-time drives the vehicle In the process, the vehicle speed signal, the steering wheel angle signal, the rotation angle signal of the steering motor obtained by the speed sensor, the torque signal of the torque motor obtained by the torque sensor, the vehicle yaw rate signal obtained by the yaw rate sensor, and the rotation angle signal of the steering front wheel, etc. Pass it to the electronic control unit and the yaw angular velocity calculation unit; send the resistance, voltage and current signals of the angle motor and the torque motor to the motor fault diagnosis unit; pass the instructions sent by the fault diagnosis unit to the fault-tolerant control strategy unit; send the yaw The difference signal between the ideal yaw rate and the actual yaw rate obtained by the angular rate calculation unit, as well as signals such as road surface interference and side wind interference are sent to the dual-machine fault-tolerant compensation control unit;

The ECU control module is respectively connected with the acquisition unit, the dual-machine execution unit, and the steering wheel assembly. It mainly includes an arithmetic controller 7 and a fault-tolerant controller 18. The arithmetic controller 7 includes a motor fault diagnosis unit and an electronic control unit; a fault-tolerant controller 18 That is, a fault-tolerant controller, including a fault-tolerant control strategy unit, a yaw rate calculation unit, a stability control unit, and a dual-motor fault-tolerant compensation unit;

The ECU control module receives the signal from the acquisition unit, and after calculation, transmits the corresponding instruction to the dual-machine execution unit for action; specifically, the motor fault diagnosis unit is an adaptive Kalman filter to realize the rotation angle motor and torque motor On-line identification of resistance, current, and voltage, which determines the state of the motor based on the real-time resistance, current, and voltage signals of the angle motor and torque motor transmitted by the acquisition unit, and transmits the actual voltage and current signals of the motor to the fault-tolerant controller.

According to the signal from the motor fault diagnosis unit, the fault-tolerant controller implements corresponding fault-tolerant compensation control strategies for different motor faults through active fault tolerance and fault mitigation; the yaw rate calculation unit transmits the steering wheel angle signal and vehicle speed The signal calculates the ideal yaw rate signal, and then calculates the ideal yaw rate difference to be adjusted according to the ideal yaw rate signal and the actual yaw rate signal, and transmits the yaw rate difference to the stability control unit; the stability control unit comprehensively considers the influence of road disturbance, side wind, system friction, etc. on the stability of the car based on the yaw rate difference transmitted by the yaw rate calculation unit, and starts from the robustness of the system to ensure the stability of the car As a premise, the compensation torque is obtained and transmitted to the dual-machine fault-tolerant compensation unit; the dual-machine fault-tolerant compensation unit receives the compensation torque signal transmitted by the stability control unit, and according to the fault-tolerant strategy of the fault-tolerant control strategy unit, through the torque motor controller 16 controls the action of the torque motor 13 to compensate the system, thereby realizing active fault tolerance or fault mitigation.

The steering wheel assembly includes a steering wheel 1, a steering column 2, a road sensor motor 3, and a road sensor motor controller 6. The steering wheel 1 is connected to the road sensor motor 3 and its steering wheel angle sensor 4 through the steering column 2. The steering wheel The torque sensor 5 is installed on the steering column 2; the road sensor motor controller 6 is connected to the road sensor motor 3 and the steering wheel torque sensor 5 to control the operation of the road sensor motor 3.

The dual-machine execution unit includes a corner motor controller 8, a corner motor 10, a bipolar reducer 11, a torque motor controller 16, a torque motor 13, a reducer 14, a rack and pinion mechanism 15, and a front wheel 17 connected in sequence; Angle motor 10 and torque motor 13 and bipolar reducer 11, reducer 14 are connected with rack and pinion steering gear 15, and front wheel 17 is installed on the both sides of rack and pinion steering gear 15, and front wheel angle sensor 9 is installed with On the front wheel 17, the angle sensor 9 and the front wheel torque sensor 12 are connected to the F1exray bus, and the angle motor controller 8 and the torque motor controller 16 signals are input into the bus, and then transmitted to the fault-tolerant controller 18 through the bus; 10 and its deceleration mechanism 11 are connected to the corner control unit 8, the corner motor control unit 8 controls the operation of the corner motor 10 and the bipolar reducer 11, the torque motor 13 and the reducer 14 are connected to the torque motor controller 16, and the torque motor controls Device 16 controls the operation of torque motor 13 and speed reducer 14; the output end of fault-tolerant controller 18 is respectively connected with the input end of road sense motor controller 6 and the Flexray bus; The torque motor sensor 12, the front wheel angle motor sensor 9, the signal of the steering wheel torque sensor 5 and the signal of the operation controller 7 are used for robust control and compensation strategy control, and the command is input into the Flexery bus, and the command is sent to The angle motor controller 8 and the torque motor controller 16 make corresponding motors act.

Secondly, the present invention also provides a mode switching control method of the active fault tolerance and fault mitigation system based on the above-mentioned steer-by-wire dual-motor system, the method includes the following steps:

Step 1: When the car is running, the acquisition unit transmits the resistance R ₃ of the corner motor R ₂ and the torque motor, and the current signals I ₂ and I ₃ to the motor fault diagnosis unit, and the motor fault diagnosis unit judges according to the magnitude of the resistance and current The state of the motor, and the relationship T=f(I) of the output motor current and torque, and the instruction is passed to the fault-tolerant control strategy unit;

Step 2: The fault-tolerant control strategy unit receives the diagnosis result from the fault diagnosis unit, obtains the operating status of the angle motor or torque motor, and compares the angle motor voltage U ₂ and the torque motor voltage U ₃ with the reference threshold U ₀ , decide to adopt active fault tolerance strategy 1, or active fault tolerance strategy 2, or fault mitigation strategy 1, or fault mitigation strategy 2;

Step 3: The yaw rate calculation unit calculates the real-time ideal yaw rate signal ω r * according to the steering wheel angle signal δ _sw collected by the acquisition unit in real time, and the vehicle speed signal u according to the law of variable transmission ratio, and then calculates the ideal yaw rate signal ω _r ^* according to the ideal yaw rate signal ω _r ^* and the actual yaw rate signal ω _r calculate the ideal yaw rate difference Δω _r that needs to be adjusted, and transmit the yaw rate difference Δω _r to the stability control unit;

The yaw rate calculation unit inputs the vehicle steering two-degree-of-freedom model according to the real-time vehicle speed u and the front wheel angle to obtain the actual yaw rate ω _r .

Δω _r =ω _r -ω _r ^* (2)

In formula (1): m is the mass of the car; Iz is the moment of inertia of the car around the z-axis; k ₁ and k ₂ are the cornering stiffnesses of the front and rear wheels respectively; δ _f is the rotation angle of the front wheels; The distance from the axis to the center of mass of the vehicle; u is the forward speed of the vehicle; ω _r is the yaw rate; β is the side slip angle of the center of mass;

Step 4: The stability control unit receives the yaw rate difference Δω _r input from the yaw rate control unit, and converts it into the corresponding compensation torque T ₁ , the compensation torque T ₂ formed by comprehensive road disturbance, and the compensation torque formed by system friction Torque T ₃ , considering system stability control factors, adopts μ comprehensive robust controller control to improve the system's ability to resist external interference, and transmits the compensation torque ΔT to the dual-machine compensation unit;

ΔT＝ΔT ₁ +ΔT ₂ +ΔT ₃ (3)

ΔT is the total compensation torque, ΔT ₁ is the compensation torque required to compensate for the difference in yaw rate, ΔT ₂ is the compensation torque formed by road disturbance, and ΔT ₃ is the compensation torque formed by system friction;

Step 5: The fault-tolerant controller receives the compensation torque T from the stability control unit, selects the corresponding compensation strategy by receiving the fault-tolerant strategy from the fault-tolerant controller, and acts on the dual-machine executive unit and the steering wheel assembly to ensure The car can have a good yaw rate control effect and good stability.

Further, in the above-mentioned mode switching control method based on the above-mentioned steer-by-wire dual-motor active fault tolerance and fault mitigation system, it also includes constructing a motor fault diagnosis unit in step 1, which can be achieved by designing an adaptive Kalman filter Realize online identification of angle motor and torque motor resistance, current and voltage:

where: for a discrete linear system:

x(k)＝Ax(k-1)+B(u(k)+w(k)) (4)

_yv (k)=Cx(k)+v(k) (5)

In formulas (4) and (5), x(k) is the system state at time k, x(k-1) is the system state at time k-1, A and B are system parameters, and u(k) is the time k For the control quantity of the system, w(k) is the process noise signal, v(k) is the measurement noise signal, y _v (k) is the measured value of the system at time k, and C is the matrix;

The discrete Kalman filter recursive algorithm is:

Mn(k)=P(k)C ^T /[CP(k)C ^T +R] (6)

P(k)=AP(k-1)A ^T +BQB ^T (7)

P(k)＝(En-Mn(k)C)P(k) (8)

x(k)=Ax(k-1)+Mn(k)( _yv (k)-CAx(k-1)) (9)

y _e (k) = Cx (k) (10)

In the equations (6)-(10), the system state at time k when x(k) and the system state at time k-1 when x(k-1) are, A, B, R are system parameters, C is a matrix, A ^T is the transpose matrix of A matrix, B ^T is the transpose matrix of B matrix, C ^T is the transpose matrix of C matrix, y _e (k) is the output signal after Kalman filter correction, P(k) is The covariance of the system at time k, P(k-1) is the covariance of the system at time k-1, En is a unit vector, and Mn(k) is an intermediate variable

En is a unit vector, then the covariance errcov(k) of the system error is:

errcov(k)=CP(k)C ^T (11)

In formula (11), errcov(k) is the covariance of the system error, C is the matrix, C ^T is the transpose matrix of the C matrix, and P(k) is the covariance of the system at time k.

According to Kirchhoff's voltage law, construct the loop model of the angle motor and the torque motor:

The electrical equation of the angle motor is:

是转角电机的电流，

是转角电机转角加速度，k_b2是转角电机的刚度。In formula (12): L is the inductance of the steering motor; R ₂ is the resistance of the steering motor; k _b2 is the electromotive force constant; u ₂ is the input voltage of the corner motor,

is the current of the angle motor,

is the corner acceleration of the corner motor, and k _b2 is the stiffness of the corner motor.

The electrical equation of the torque motor is:

是转矩电机转角加速度，k_b3是转角电机的刚度。In the formula: L is the inductance of the torque motor; R ₃ is the resistance of the torque motor; k _b3 is the electromotive force constant; u ₃ is the input voltage of the torque motor, i _a3 is the current of the torque motor,

is the angular acceleration of the torque motor, and k _b3 is the stiffness of the angular motor.

The adaptive Kalman filter transmits the voltage, current and resistance signals of the angle motor and torque motor to the fault-tolerant control strategy unit.

Further, the four real-time fault-tolerant control strategies formed in step 2, active fault-tolerant strategy 1, or active fault-tolerant strategy 2, or fault mitigation strategy 1, or the process of fault mitigation strategy 2 include:

Step 2.1: The Kalman filter can determine the fault of the angle motor or torque motor by monitoring the resistance fluctuation beyond the normal range. Considering the optimization of motor performance, when the maximum output voltage of the motor is greater than the safety margin voltage, that is, U>=0.5U _max , U ₀ =0.5U _max , it can be considered that the motor can perform some functions of the motor and output a certain torque. Torque T=f(I), which is the premise of the fault mitigation strategy, and the higher output voltage capability is also the guarantee that the motor can perform compensation work;

From the perspective of safety, in order to prevent the angle motor or torque motor from being unable to output sufficient torque in time, when the maximum voltage of the motor is less than the safety margin, that is, U<=0.5U _max , U ₀ =0.5U _max , it can be considered The faulty motor cannot function, and the faulty motor cannot complete the compensation work. At this time, the system isolates the faulty motor and performs active fault-tolerant strategy control;

Step 2.2: Define 0 for normal operation of the corner motor, 1 for semi-normal operation of the corner motor, 2 for non-running of the corner motor, full failure, definition 3 for normal operation of the torque motor, 4 for semi-normal operation of the torque motor, and 5 for rotation The torque motor cannot run, full failure; semi-normal operation means U ₂ ＞=U ₀ or U ₃ ＞=U ₀ ; a fault vector table is formed according to the fault conditions of the angle motor and the torque motor, and the fault vector table includes the angle motor and the torque The operating state of the motor and the corresponding fault conditions; the fault vector table is as follows:

Fault vector table

fault vector Fault conditions 03 Both motors are fine 25 Both motors fail 04 Angle motor is normal, torque motor is half normal 13 Corner motor half normal, torque motor normal 05 The corner motor is normal, and the torque motor is all faulty twenty three The angle motor is completely faulty, and the torque motor is normal 15 The corner motor is half normal, and the torque motor is completely faulty twenty four The angle motor is completely faulty, and the torque motor is half normal 14 Corner motor half normal, torque half normal

The fault tolerance strategy adopted in step 2 specifically includes:

1) When both the angle motor and the torque motor work normally, the two motors work together to control the front wheel angle and the yaw rate of the vehicle. At this time, no fault-tolerant strategy is needed; when the two motors work normally, the rack motion analysis is as follows:

The differential equation of motion for the rack is:

为齿条加速度，

为齿条的运动速度；In the formula: m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is the inter-system Friction, G is the reduction ratio of the double reducer mechanism; T _g2 is the output torque of the steering motor 2; T _g3 is the output torque of the steering motor 3;

is the rack acceleration,

is the movement speed of the rack;

The differential equation of motion of the wheel is:

转向前轮的转角加速度，

为转向前轮角速度，M_Z为车轮的回正力矩；In formula (15): J _w is the moment of inertia of the front wheel; T _frkp is the friction moment; B _{kp is} the damping coefficient of the kingpin.

The angular acceleration of the steering front wheels,

is the angular velocity of the steering front wheel, and M _Z is the aligning moment of the wheel;

2) When the corner motor is normal and the torque motor is half normal, the system performs fault mitigation strategy 1, the corner motor mainly controls the yaw rate of the vehicle, and the torque motor compensates the compensation torque ΔT ₁ fed back by the yaw rate controller;

For the comprehensive ΔT ₁ = ΔT ₁₁ + ΔT ₂₁ + ΔT ₃₁ (16) where ΔT ₁ is the total compensation torque, T ₁₁ is the compensation torque required to compensate for the difference in yaw rate, T ₂₁ is the compensation torque caused by road disturbance Moment, the compensation torque formed by T ₃₁ system friction;

In formula (17), m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is The friction between the systems, G is the reduction ratio of the double reducer mechanism; T _g2 is the output torque of the steering motor 2; T _a3 is the output torque of the steering motor 3;

3) When the corner motor is semi-normal and the torque motor is normal, use fault mitigation strategy 2, the torque motor acts as the corner motor for main control, and the corner motor acts as the torque motor to compensate the compensation torque fed back by the yaw rate controller ΔT ₂ ;

For integrated ΔT ₂ =ΔT ₁₂ +ΔT ₂₂ +ΔT ₃₂ (18)

Among them, ΔT ₂ is the total compensation torque, T ₁₂ is the compensation torque required to compensate for the difference in yaw rate, T ₂₂ is the compensation torque formed by road disturbance, and T ₃₂ is the compensation torque formed by system friction;

4) When the corner motor is normal and the torque motor is completely faulty, adopt the active fault tolerance strategy 1, cut off the current input of the torque motor, control the corner motor separately, and compensate the compensation torque ΔT ₃ fed back by the yaw rate controller;

Its comprehensive ΔT ₃ =ΔT ₁₃ +ΔT ₂₃ +ΔT ₃₃ (20)

Among them, ΔT ₃ is the total compensation torque, T ₁₃ is the compensation torque required to compensate for the difference in yaw rate, T ₂₃ is the compensation torque formed by road disturbance, and T ₃₃ is the compensation torque formed by system friction;

In formula (21), m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is The friction between the systems, G is the reduction ratio of the double reducer mechanism; T _g2 is the output torque of the steering motor 2; T _a3 is the output torque of the steering motor 3;

5) When the corner motor fails completely and the torque motor is normal, active fault tolerance strategy 2 is adopted to cut off the current input of the corner motor, and the torque motor is controlled separately, and the torque motor acts as a corner motor to compensate for the feedback from the yaw rate controller Torque ΔT ₄ ;

Its comprehensive ΔT ₄ =ΔT ₁₄ +ΔT ₂₄ +ΔT ₃₄ (22)

Among them, ΔT ₄ is the total compensation torque, T ₁₄ is the compensation torque required to compensate for the difference in yaw rate, T ₂₄ is the compensation torque formed by road disturbance, and T ₃₄ is the compensation torque formed by system friction;

6) When the two motors are normal, there is no need to apply a fault tolerance strategy. When both motors are faulty (semi-normal or full fault), the probability is very small, which is not within the scope of this application.

Further, in the above-mentioned mode switching control method of the active fault-tolerant and fault mitigation system based on steer-by-wire dual motors, in the step 4, the control framework of the μ comprehensive robust controller includes:

a) Yaw rate tracking, ||Z ₁ || ₂ ＝||W ₁ (ωr ^* -ω _r )|| ₂ (24)

Wherein, W ₁ is a weighting function, usually set as a low-pass filter W ₁ =k ₁ (as+b)/(cs+d) (25)

In formula (24)(25), ||Z ₁ || ₂ is the 2-norm of the evaluation output of the controlled object, ω _r ^* is the ideal yaw rate value, ω _r is the actual vehicle yaw rate value, W ₁ is Weighting function, a, s, b, a, d are the parameters of the low-pass filter.

The μ-integrated robust controller must be able to quickly track the difference between the ideal yaw rate and the actual yaw rate under different fault-tolerant strategies, and it must also have a better interference suppression for external disturbances such as ground disturbances and side wind disturbances, or Output the corresponding compensation torque and transmit the compensation torque ΔT to the dual-machine compensation unit;

b) Compensation feedback, stability control: ΔT=ΔT ₁ +ΔT ₂ +ΔT ₃ (26)

Among them, ΔT is the total compensation torque, ΔT ₁ is the compensation torque required to compensate for the difference in yaw rate, ΔT ₂ is the compensation torque formed by road disturbance, and ΔT ₃ is the compensation torque formed by system friction.

In the present invention, the fault tolerance concept of fault mitigation is proposed relative to the traditional fault tolerance concept. The traditional research idea is to adopt the method of hardware redundancy or software redundancy. The consideration of hardware redundancy is to replace the failed hardware with new hardware, separate the faulty hardware from the system, or adopt the method of software redundancy. , replace hardware redundancy with software redundancy, and replace the data of failed components by deriving calculated data from other sensors or actuators. In the actual process, this is a relatively conservative fault-tolerant method, which is essentially a substitution relationship. New parts are used to replace faulty parts, and other data are used to replace wrong data. At this time, the car can be called "sickness-free work." However, the remaining functions of the faulty component have not been fully developed and are wasted. For example, after the motor fails, it is not completely paralyzed. It can use part of the function to output a certain torque. According to different fault conditions of the motor, the faulty motor and the normal motor can be used at the same time. Work, the car at this time can be called "sick work". This application realizes the real-time optimal control of the automobile through the matching and comparison of the faulty motor and the normal motor. And at the same time, it can ensure the better working ability and performance of the car in extreme wild environments, and also provides a guarantee for the car to be repaired at the most advanced maintenance point.

Compared with the existing ones, through the steer-by-wire dual-motor system and its fault-tolerant mode switching control method of the present invention, multiple steering mode functions are realized in the steer-by-wire system of automobiles, and different faults of the dual motors are implemented according to the steering of the automobile. The switch of steering mode realizes the real-time optimal control of the vehicle, which is the unification of the economy and flexibility of the steer-by-wire vehicle, and makes full use of the remaining functions of the faulty parts to save resources, and has broad market application prospects.

Description of drawings

Fig. 1 is a schematic diagram of the structural layout of the steering-by-wire dual-motor system of the present invention.

Fig. 2 is a schematic diagram of the control device of the steering-by-wire dual-motor active fault-tolerant and fault-mitigating fault-tolerant system of the present invention.

Fig. 3 is a general diagram of the control strategy of the steering-by-wire dual-motor active fault-tolerant and fault-mitigated fault-tolerant system of the present invention.

Figure 4 is a block diagram of a vehicle stability control system for a steer-by-wire dual-motor vehicle with a fault-tolerant function based on yaw rate feedback.

In the figure, 1. Steering wheel; 2. Steering column; 3. Road sense motor; 4. Steering wheel angle sensor; 5. Steering wheel torque sensor; 6. Road sense motor controller; 7. Operation controller; 8. Corner angle Motor controller; 9. Front wheel angle sensor; 10. Angle motor; 11. Bipolar reducer; 12. Front wheel torque sensor; 13. Torque motor; 14. Reducer; 15. Rack and pinion mechanism; 16. Torque motor controller; 17, front wheel; 18, fault-tolerant controller; 19, vehicle speed sensor.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below in conjunction with examples and accompanying drawings, and the contents mentioned in the implementation modes are not intended to limit the present invention.

Referring to the layout diagram of a kind of active fault-tolerant and fault-relief system based on steering-by-wire dual motors of the present invention shown in Fig. In implementation, M7 or MT20U) and dual-machine execution unit can also be used;

Among them, the acquisition unit is connected with the ECU control module, the steering wheel assembly, and the dual-machine execution unit respectively; the acquisition unit includes the steering wheel angle sensor 4, the steering wheel torque sensor 5, the front wheel angle sensor 9, the front wheel torque sensor 12, and the vehicle speed sensor 19. The yaw rate sensor and other sensors that collect the state of the car; the collection unit collects the vehicle speed signal, the steering wheel angle signal, the rotation angle signal of the steering motor obtained by the speed sensor, the torque signal of the torque motor obtained by the torque sensor, and The vehicle yaw rate signal obtained by the yaw rate sensor, the steering angle signal of the front wheel, etc. are transmitted to the electronic control unit and the yaw rate calculation unit; the resistance, voltage and current signals of the corner motor and torque motor are sent to the motor fault diagnosis Unit; transmit the instruction sent by the fault diagnosis unit to the fault-tolerant control strategy unit; send the signal of the difference between the ideal yaw rate and the actual yaw rate obtained by the yaw rate calculation unit and the signal of road interference and lateral wind interference to the two-machine Fault-tolerant compensation control unit;

The ECU control module is respectively connected with the acquisition unit, the dual-machine execution unit, and the steering wheel assembly, and mainly includes an arithmetic controller 7 and a fault-tolerant controller 18, and the arithmetic controller 7 includes a motor fault diagnosis unit and an electronic control unit; the fault-tolerant controller 18 is Fault-tolerant controller, including fault-tolerant control strategy unit, yaw rate calculation unit, stability control unit, and dual-motor fault-tolerant compensation unit;

The ECU control module receives the signal from the acquisition unit, and after calculation, transmits the corresponding instruction to the dual-machine execution unit for action; specifically, the motor fault diagnosis unit is an adaptive Kalman filter to realize the rotation angle motor and torque motor On-line identification of resistance, current, and voltage, which determines the state of the motor based on the real-time resistance, current, and voltage signals of the angle motor and torque motor transmitted by the acquisition unit, and transmits the actual voltage and current signals of the motor to the fault-tolerant controller.

According to the signal from the motor fault diagnosis unit, the fault-tolerant controller implements corresponding fault-tolerant compensation control strategies for different motor faults through active fault tolerance and fault mitigation; the yaw rate calculation unit transmits the steering wheel angle signal and vehicle speed The signal calculates the ideal yaw rate signal, and then calculates the ideal yaw rate difference to be adjusted according to the ideal yaw rate signal and the actual yaw rate signal, and transmits the yaw rate difference to the stability control unit; the stability control unit comprehensively considers the influence of road disturbance, side wind, system friction, etc. on the stability of the car based on the yaw rate difference transmitted by the yaw rate calculation unit, and starts from the robustness of the system to ensure the stability of the car As a premise, the compensation torque is obtained and transmitted to the dual-machine fault-tolerant compensation unit; the dual-machine fault-tolerant compensation unit receives the compensation torque signal transmitted by the stability control unit, and according to the fault-tolerant strategy of the fault-tolerant control strategy unit, through the torque motor controller 16 controls the action of the torque motor 13 to compensate the system, thereby realizing active fault tolerance or fault mitigation.

The steering wheel assembly is respectively connected with the acquisition unit and the ECU control module. The steering wheel assembly includes a steering wheel 1, a steering column 2, a road sensor motor 3, and a road sensor motor controller 6. The steering wheel 1 communicates with the steering column 2 and The road sensor motor 3 and its steering wheel angle sensor 4 are connected, and the steering wheel torque sensor 5 is installed on the steering column 2; the road sensor motor controller 6 is connected to the road sensor motor 3 and the steering wheel torque sensor 5 to control the road sensor motor 3 running.

The two-machine execution unit is connected to the acquisition unit and the ECU control module respectively, and the two-machine execution unit includes a corner motor controller 8 connected in sequence, a corner motor 10, a bipolar reducer 11, a torque motor controller 16, and a torque motor 13, reducer 14, rack and pinion mechanism 15, front wheel 17; Angle motor 10 and torque motor 13 and bipolar reducer 11, reducer 14 are connected with pinion and rack steering gear 15, and front wheel 17 is installed on the gear On both sides of the rack steering gear 15, the front wheel angle sensor 9 is installed on the front wheel 17, the angle sensor 9 and the front wheel torque sensor 12 are connected to the Flexray bus, and the angle motor controller 8 and the torque motor controller 16 signals are input to the In the bus, it is transmitted to the fault-tolerant controller 18 through the bus; the corner motor 10 and its speed reduction mechanism 11 are connected to the corner control unit 8, and the corner motor control unit 8 controls the operation of the corner motor 10 and the bipolar reducer 11, and the torque motor 13 And speed reducer 14 connects torque motor controller 16, and torque motor controller 16 controls the operation of torque motor 13 and speed reducer 14; The bus is connected; the fault-tolerant controller 18 receives the signals of the front wheel torque motor sensor 12, the front wheel angle motor sensor 9, the steering wheel torque sensor 5 and the signal of the arithmetic controller 7, which are transmitted to the Flexary, and performs robust control and compensation The strategy is controlled, and the command is input into the Flexery bus, and the command is sent to the angle motor controller 8 and the torque motor controller 16 to make the corresponding motor act.

Figures 2 and 3 are schematic diagrams of the steering-by-wire dual-motor active fault-tolerant and fault-mitigating fault-tolerant system control device and a general diagram of the control strategy for the steer-by-wire dual-motor active fault-tolerant and fault-relieving fault-tolerant system. The control flow of the present invention is as follows:

Step 1: When the car is running, the acquisition unit transmits the resistance R ₃ of the corner motor R ₂ and the torque motor, and the current signals I ₂ and I ₃ to the motor fault diagnosis unit, and the motor fault diagnosis unit judges according to the magnitude of the resistance and current Motor state, and the relation T=f(I) of output motor current and torque, and instruction (voltage of torque motor, electric current, resistance signal) is delivered to fault-tolerant control strategy unit;

The motor fault diagnosis unit includes an adaptive Kalman filter to realize the online identification of angle motor and torque motor resistance, current and voltage:

where: for a discrete linear system:

x(k)＝Ax(k-1)+B(u(k)+w(k)) (4)

_yv (k)=Cx(k)+v(k) (5)

In formulas (4) and (5), x(k) is the system state at time k, x(k-1) is the system state at time k-1, A and B are system parameters, and u(k) is the time k For the control quantity of the system, w(k) is the process noise signal, v(k) is the measurement noise signal, y _v (k) is the measured value of the system at time k, and C is the matrix;

The discrete Kalman filter recursive algorithm is:

Mn(k)=P(k)C ^T /[CP(k)C ^T +R] (6)

P(k)=AP(k-1)A ^T +BQB ^T (7)

P(k)＝(En-Mn(k)C)P(k) (8)

x(k)=Ax(k-1)+Mn(k)( _yv (k)-CAx(k-1)) (9)

y _e (k) = Cx (k) (10)

In the equations (6)-(10), the system state at time k when x(k) and the system state at time k-1 when x(k-1) are, A, B, R are system parameters, C is a matrix, A ^T is the transpose matrix of A matrix, B ^T is the transpose matrix of B matrix, C ^T is the transpose matrix of C matrix, y _e (k) is the output signal after Kalman filter correction, P(k) is The covariance of the system at time k, P(k-1) is the covariance of the system at time k-1, En is a unit vector, and Mn(k) is an intermediate variable

En is a unit vector, then the covariance errcov(k) of the system error is:

errcov(k)=CP(k)C ^T (11)

In formula (11), errcov(k) is the covariance of the system error, C is the matrix, C ^T is the transpose matrix of the C matrix, and P(k) is the covariance of the system at time k.

According to Kirchhoff's voltage law, construct the loop model of the angle motor and the torque motor:

The electrical equation of the angle motor is:

是转角电机的电流，

是转角电机转角加速度，k_b2是转角电机的刚度。In formula (12): L is the inductance of the steering motor; R ₂ is the resistance of the steering motor; k _b2 is the electromotive force constant; u ₂ is the input voltage of the corner motor,

is the current of the angle motor,

is the corner acceleration of the corner motor, and k _b2 is the stiffness of the corner motor.

The electrical equation of the torque motor is:

是转矩电机转角加速度，k_b3是转角电机的刚度；In the formula: L is the inductance of the torque motor; R ₃ is the resistance of the torque motor; k _b3 is the electromotive force constant; u ₃ is the input voltage of the torque motor, i _a3 is the current of the torque motor,

is the angular acceleration of the torque motor, k _b3 is the stiffness of the angular motor;

Step 2: The fault-tolerant control strategy unit receives the diagnosis result from the fault diagnosis unit, obtains the operating status of the angle motor or torque motor, and compares the angle motor voltage U ₂ and the torque motor voltage U ₃ with the reference threshold U ₀ , decide to adopt active fault tolerance strategy 1, or active fault tolerance strategy 2, or fault mitigation strategy 1, or fault mitigation strategy 2;

The process of the above active fault tolerance strategy 1, or active fault tolerance strategy 2, or fault mitigation strategy 1, or fault mitigation strategy 2 includes:

Step 2.1: The Kalman filter can determine the fault of the angle motor or torque motor by monitoring the resistance fluctuation beyond the normal range. Considering the optimization of motor performance, when the maximum output voltage of the motor is greater than the safety margin voltage, that is, U>=0.5U _max , U0=0.5U _max , it can be considered that the motor can perform some functions of the motor, output a certain torque, and rotate Torque T=f(I), which is the premise of the fault mitigation strategy, and the higher output voltage capability is also the guarantee that the motor can perform compensation work;

From the perspective of safety, in order to prevent the angle motor or torque motor from being unable to output sufficient torque in time, when the maximum voltage of the motor is less than the safety margin, that is, U<=0.5U _max , U ₀ =0.5U _max , it can be considered The faulty motor cannot function, and the faulty motor cannot complete the compensation work. At this time, the system isolates the faulty motor and performs active fault-tolerant strategy control;

Step 2.2: Define 0 for normal operation of the corner motor, 1 for semi-normal operation of the corner motor, 2 for non-running of the corner motor, full failure, definition 3 for normal operation of the torque motor, 4 for semi-normal operation of the torque motor, and 5 for rotation The torque motor cannot run, full failure; semi-normal operation means U ₂ ＞= U ₀ or U ₃ ＞= U ₀ ; a fault vector table is formed according to the fault conditions of the angle motor and the torque motor, and the fault vector table includes the angle motor and the torque The operating state of the motor and the corresponding fault conditions; the fault vector table is as follows:

Fault vector table

The fault tolerance strategy adopted in step 2 specifically includes:

1) When both the angle motor and the torque motor work normally, the two motors work together to control the front wheel angle and the yaw rate of the vehicle. At this time, no fault-tolerant strategy is needed; when the two motors work normally, the rack motion analysis is as follows:

The differential equation of motion for the rack is:

为齿条加速度，

为齿条的运动速度；In the formula: m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is the inter-system Friction, G is the reduction ratio of the double reducer mechanism; T _g2 is the output torque of the steering motor 2; T _g3 is the output torque of the steering motor 3;

is the rack acceleration,

is the movement speed of the rack;

The differential equation of motion of the wheel is:

转向前轮的转角加速度，

为转向前轮角速度，M_Z为车轮的回正力矩；In formula (15): J _w is the moment of inertia of the front wheel; T _frkp is the friction moment; B _{kp is} the damping coefficient of the kingpin.

The angular acceleration of the steering front wheels,

is the angular velocity of the steering front wheel, and M _Z is the aligning moment of the wheel;

2) When the corner motor is normal and the torque motor is half normal, the system performs fault mitigation strategy 1, the corner motor mainly controls the yaw rate of the vehicle, and the torque motor compensates the compensation torque ΔT ₁ fed back by the yaw rate controller;

For comprehensive Δ _T 1 = Δ T ₁₁ + Δ T ₂₁ + Δ T ₃₁ (16)

Among them, ΔT ₁ is the total compensation torque, T ₁₁ is the compensation torque required to compensate for the difference in yaw rate, _T2 1 is the compensation torque formed by road disturbance, and T31 is the compensation torque formed by system friction;

In formula (17), m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is The friction between the systems, G is the reduction ratio of the double reducer mechanism; T _a2 is the output torque of the steering motor 2; T _a3 is the output torque of the steering motor 3;

3) When the corner motor is semi-normal and the torque motor is normal, use fault mitigation strategy 2, the torque motor acts as the corner motor for main control, and the corner motor acts as the torque motor to compensate the compensation torque fed back by the yaw rate controller ΔT ₂

For the comprehensive ΔT ₂ = ΔT ₁₂ + ΔT ₂₂ + ΔT ₃₂ (18) where ΔT ₂ is the total compensation torque, T ₁₂ is the compensation torque required to compensate for the difference in yaw rate, and T ₂₂ is the compensation torque caused by road disturbance Moment, compensation torque formed by T ₃₂ system friction;

4) When the corner motor is normal and the torque motor is completely faulty, adopt the active fault tolerance strategy 1, cut off the current input of the torque motor, control the corner motor separately, and compensate the compensation torque ΔT ₃ fed back by the yaw rate controller;

Its comprehensive ΔT ₃ =ΔT ₁₃ +ΔT ₂₃ +ΔT ₃₃ (20)

Among them, ΔT3 is the total compensation torque, T13 is the compensation torque required to compensate for the difference in yaw rate, T23 is the compensation torque formed by road disturbance, and T33 is the compensation torque formed by system friction;

In formula (21), m _rack is the mass of the rack; y _rack is the displacement of the rack; r _L is the offset of the main pin axis; K _L is the stiffness of the steering rod; B _rack is the damping coefficient of the rack; F _frrack is The friction between the systems, G is the reduction ratio of the double reducer mechanism; T _a2 is the output torque of the steering motor 2; T _a3 is the output torque of the steering motor 3;

5) When the corner motor fails completely and the torque motor is normal, active fault tolerance strategy 2 is adopted to cut off the current input of the corner motor, and the torque motor is controlled separately, and the torque motor acts as a corner motor to compensate for the feedback from the yaw rate controller Torque ΔT ₄ :

Its comprehensive ΔT ₄ =ΔT ₁₄ +ΔT ₂₄ +ΔT ₃₄ (22)

Among them, ΔT ₄ is the total compensation torque, T ₁₄ is the compensation torque required to compensate for the difference in yaw rate, T ₂₄ is the compensation torque formed by road disturbance, and T ₃₄ is the compensation torque formed by system friction;

6) When the two motors are normal, there is no need to apply a fault tolerance strategy. When both motors are faulty (semi-normal or full fault), the probability is very small, which is not within the scope of this application.

Further, in the above-mentioned mode switching control method of the active fault-tolerant and fault-mitigating system based on steer-by-wire dual motors, in the step 4, the control frame diagram of the μ comprehensive robust controller is shown in Figure 4, and in Figure 4, K is the controller, the disturbance input of the system ω _r is the ideal yaw rate, the disturbance input is the ideal front wheel angle δ _f ^* , the side wind disturbance Fv and the disturbance torque T _r of the road surface, W ₁ and W ₂ are weighting functions , usually set as a high-pass filter. W _d is the interference weighting matrix, ΔG is the unknown parameter perturbation, ΔI is the compensation current, z ₁ and z ₂ are the evaluation outputs.

Specifically, the control framework of the μ-synthesis robust controller includes:

a) Yaw rate tracking, ||Z ₁ || ₂ ＝||W ₁ (ω _r ^* -ω _r )|| ₂ (24)

Wherein, W ₁ is a weighting function, usually set as a low-pass filter W ₁ =k ₁ (as+b)/(cs+d) (25)

In equations (24)(25), ||Z _Z || ₂ is the 2-norm of the evaluation output of the controlled object, ω _r ^* is the ideal yaw rate value, ω _r is the actual vehicle yaw rate value, W ₁ is Weighting function, a, s, b, a, d are the parameters of the low-pass filter.

The μ-integrated robust controller must be able to quickly track the difference between the ideal yaw rate and the actual yaw rate under different fault-tolerant strategies, and it must also have a better interference suppression for external disturbances such as ground disturbances and side wind disturbances, or Output the corresponding compensation torque and transmit the compensation torque ΔT to the dual-machine compensation unit;

b) Compensation feedback, stability control: ΔT=ΔT ₁ +ΔT ₂ +ΔT ₃ (26)

Among them, ΔT is the total compensation torque, ΔT ₁ is the compensation torque required to compensate for the difference in yaw rate, ΔT ₂ is the compensation torque formed by road disturbance, and ΔT ₃ is the compensation torque formed by system friction;

Step 3: The yaw rate calculation unit calculates the real-time ideal yaw rate signal ω _r ^* according to the steering wheel angle signal δs _w collected by the acquisition unit in real time, and the vehicle speed signal u according to the law of variable transmission ratio, and then according to the ideal yaw rate signal ω _r ^* and the actual yaw rate signal ω _r calculate the ideal yaw rate difference Δω _r that needs to be adjusted, and transmit the yaw rate difference Δω _r to the stability control unit;

The yaw rate calculation unit inputs the vehicle steering two-degree-of-freedom model according to the real-time vehicle speed u and the front wheel angle to obtain the actual yaw rate ω _r .

Δω _r =ω _r -ω _r ^* (2)

In formula (1): m is the mass of the car; Iz is the moment of inertia of the car around the z-axis; k ₁ and k ₂ are the cornering stiffnesses of the front and rear wheels respectively; δ _f is the rotation angle of the front wheels; The distance from the axis to the center of mass of the vehicle; u is the forward speed of the vehicle; ω _r is the yaw rate; β is the side slip angle of the center of mass;

Step 4: The stability control unit receives the yaw rate difference Δω _r input from the yaw rate control unit, and converts it into the corresponding compensation torque T ₁ , the compensation torque T ₂ formed by comprehensive road disturbance, and the compensation torque formed by system friction Torque T ₃ , considering system stability control factors, adopts μ comprehensive robust controller control to improve the system's ability to resist external interference, and transmits the compensation torque ΔT to the dual-machine compensation unit;

ΔT＝ΔT ₁ +ΔT ₂ +ΔT ₃ (3)

ΔT is the total compensation torque, ΔT ₁ is the compensation torque required to compensate for the difference in yaw rate, ΔT ₂ is the compensation torque formed by road disturbance, and ΔT ₃ is the compensation torque formed by system friction;

Step 5: The fault-tolerant controller receives the compensation torque T from the stability control unit, selects the corresponding compensation strategy by receiving the fault-tolerant strategy from the fault-tolerant controller, and acts on the rack mechanism to ensure that the car can have a good lateral Pendulum angular speed control effect, and good stability.

There are many specific application approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principle of the present invention. Improvements should also be regarded as the protection scope of the present invention.

Claims (4)

1. A mode switching control method of an active fault tolerance and fault relief system of a steer-by-wire double motor is characterized by comprising the following specific steps:

step 1: the acquisition unit acquires the resistance R of the corner motor during the running of the automobile ₂ And resistance R of torque motor ₃ Current signal I ₂ And I ₃ The motor fault diagnosis unit judges the motor state according to the resistance and the current, outputs the relation T=f (I) between the motor current and the torque, and transmits the instruction to the fault-tolerant control strategy unit;

step 2: the fault-tolerant control strategy unit receives the diagnosis result from the fault diagnosis unit, obtains the running state working condition of the corner motor or the torque motor, and compares the voltage U of the corner motor ₂ And torque motor voltage U ₃ And a reference threshold U ₀ Comparing, determining to adopt an active fault tolerance strategy 1, an active fault tolerance strategy 2, a fault relief strategy 1 or a fault relief strategy 2;

step 2.1: when the maximum voltage of the motor output is greater than the safety margin voltage, i.e. U>＝0.5U _max ,U ₀ ＝0.5U _max When the motor can be considered to play a part of the motor function, a certain torque is output, and the torque T=f (I); when the maximum voltage of the motor is less than the safety margin, i.e. U<＝0.5U _max ,U ₀ ＝0.5U _{max of max} The fault motor is considered to be incapable of functioning, the fault motor cannot complete compensation work, and at the moment, the system isolates the fault motor and performs control of an active fault-tolerant strategy;

step 2.2: definition 0 indicates normal operation of the corner motor, 1 indicates semi-normal operation of the corner motor, 2 indicates non-operation of the corner motor, and full fault, definition 3 indicates normal operation of the torque motor, 4 indicates semi-normal operation of the torque motor, 5 indicates non-operation of the torque motor, and full fault; semi-normal operation representation U ₂ >＝U ₀ Or U ₃ >＝U ₀ ；

Step 3: the yaw rate calculation unit calculates steering wheel angle signals delta according to the steering wheel angle signals delta acquired by the acquisition unit in real time _sw The vehicle speed signal u calculates real-time ideal yaw rate signal omega according to the variable transmission ratio rule _r ^* Then according to the ideal yaw rate signal omega _r ^* And the actual yaw-rate signal omega _r Calculating the ideal yaw rate difference delta omega to be adjusted _r And the yaw rate difference Deltaomega _r Transmitting to a stability control unit;

the yaw rate calculation unit inputs the real-time speed u and the front wheel steering angle of the automobile into a two-degree-of-freedom model of steering of the whole automobile to obtain the actual yaw rate omega _r ：

Δω _r ＝ω _r -ω _r ^* (2)

In the formula (1): m is the mass of the automobile; iz is the moment of inertia of the automobile around the z axis; k (k) ₁ 、k ₂ The cornering stiffness of the front and rear wheels respectively; delta _f Is the front wheel corner; a, b are the distances from the front and rear axles to the mass center of the vehicle respectively; u is the forward speed of the vehicle; omega _r Is yaw rate; beta is the centroid slip angle;

step 4: the stability control unit receives the yaw rate difference Deltaomega input from the yaw rate control unit _r Converted into corresponding compensation torque T ₁ Compensation torque T formed by comprehensive road surface interference ₂ Compensating torque T formed by friction of system ₃ Taking system stability control factors into consideration, adopting a mu comprehensive robust controller to control, and transmitting compensation torque delta T to a double-machine compensation unit;

ΔT＝ΔT ₁ +ΔT ₂ +ΔT ₃ (3)

DeltaT makes the total compensation torque DeltaT ₁ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂ Compensation torque, delta T, formed by road disturbance ₃ Compensating torque formed by system friction;

step 5: the fault-tolerant controller receives the compensation torque T from the stability control unit, and selects a corresponding compensation strategy to act on the dual-machine execution unit by receiving the fault-tolerant strategy transmitted by the fault-tolerant controller;

the drive-by-wire steering double-motor active fault tolerance and fault relief system comprises an acquisition unit, a steering wheel assembly, an ECU control module and a double-machine execution unit;

the acquisition unit is respectively connected with the ECU control module, the steering wheel assembly and the double-machine execution unit; the acquisition unit comprises a steering wheel angle sensor (4), a steering wheel moment sensor (5), a front wheel rotation angle sensor (9), a front wheel moment sensor (12), a vehicle speed sensor (19) and a yaw rate sensor;

the acquisition unit transmits a vehicle speed signal, a steering wheel corner signal, a corner signal of a corner motor obtained by a rotating speed sensor, a torque signal of a torque motor obtained by a torque sensor, a vehicle yaw rate signal obtained by a yaw rate sensor and a corner signal of a steering front wheel to the electronic control unit and the yaw rate calculation unit in real time; the resistance, voltage and current signals of the corner motor and the torque motor are sent to a motor fault diagnosis unit; transmitting the instruction sent by the fault diagnosis unit to a fault-tolerant control strategy unit; the difference signal of the ideal yaw rate and the actual yaw rate obtained by the yaw rate calculation unit and the road surface interference lateral wind interference signal are sent to a double-machine fault-tolerant compensation control unit;

The ECU control module is respectively connected with the acquisition unit, the double-machine execution unit and the steering wheel assembly, the ECU control module comprises an operation controller (7) and a fault-tolerant controller (18), and the operation controller (7) comprises a motor fault diagnosis unit and an electronic control unit; the fault-tolerant controller (18) comprises a fault-tolerant control strategy unit, a yaw rate calculation unit, a stability control unit and a double-motor fault-tolerant compensation unit; the ECU control module receives signals from the acquisition unit, and transmits corresponding instructions to the dual-computer execution unit for action after calculation;

the fault-tolerant controller (18) carries out corresponding fault-tolerant compensation control strategies on different motor faults in an active fault-tolerant and fault-relieving mode according to signals transmitted by the motor fault diagnosis unit; the yaw rate calculation unit calculates an ideal yaw rate signal according to the steering wheel angle signal and the vehicle speed signal transmitted by the acquisition unit, calculates an ideal yaw rate difference value required to be adjusted according to the ideal yaw rate signal and the actual yaw rate signal, and transmits the yaw rate difference value to the stability control unit; the stability control unit obtains a compensation torque according to the yaw rate difference value transmitted by the yaw rate calculation unit and transmits the compensation torque to the double-machine fault-tolerant compensation unit; the double-machine fault-tolerant compensation unit receives the compensation torque signal transmitted by the stability control unit and controls the action of the torque motor (13) through the torque motor controller (16) according to the fault-tolerant strategy of the fault-tolerant control strategy unit;

The steering wheel assembly comprises a steering wheel (1), a steering column (2) and a road-sensing motor (3), a road-sensing motor controller (6), the steering wheel (1) is connected with the road-sensing motor (3) and a steering wheel angle sensor (4) through the steering column (2), a steering wheel moment sensor (5) is arranged on the steering column (2), and the road-sensing motor controller (6) is connected with the road-sensing motor (3) and the steering wheel moment sensor (5) to control the running of the road-sensing motor (3);

the double-machine executing unit comprises a corner motor controller (8), a corner motor (10), a bipolar speed reducer (11), a torque motor controller (16), a torque motor (13), a speed reducer (14), a gear rack mechanism (15) and a front wheel (17);

the gear-rack mechanism (15) is respectively connected with the corner motor (10), the torque motor (13), the bipolar speed reducer (11) and the speed reducer (14), the front wheels (17) are arranged on two sides of the gear-rack mechanism (15), the front wheel steering angle sensor (9) is arranged on the front wheels (17), the front wheel steering angle sensor (9) is connected with the front wheel torque sensor (12) through a bus, signals of the corner motor controller (8) and the torque motor controller (16) are input into the bus, and then are transmitted into the fault-tolerant controller (18) through the bus; the corner motor (10) and the bipolar speed reducer (11) are respectively connected with the corner motor controller (8); the torque motor (13) and the speed reducer (14) are connected with a torque motor controller (16), and the torque motor controller (16) controls the operation of the torque motor (13) and the speed reducer (14); the output end of the fault-tolerant controller (18) is respectively connected with the input end of the road-sensing motor controller (6) and the bus; the fault-tolerant controller (18) receives signals transmitted by the front wheel torque sensor (12), the front wheel steering angle sensor (9), the steering wheel torque sensor (5) and the operation controller (7), and transmits instructions to the steering angle motor controller (8) and the torque motor controller (16).

2. The method according to claim 1, wherein in step 1, the motor fault diagnosis unit includes on-line identification of corner motor and torque motor resistance, current, voltage by a Kalman filter:

wherein: for a discrete linear system:

x(k)＝Ax(k-1)+B(u(k)+w(k)) (4)

y _v (k)＝Cx(k)+v(k) (5)

in the formulas (4) and (5), x (k) is the system state at the time k, x (k-1) is the system state at the time k-1, A, B are system parameters, u (k) is the control quantity of the system at the time k, w (k) is a process noise signal, v (k) is a measurement noise signal, and y _v (k) Is a measurement value at the time of k of the system, C is a matrix;

the discrete Kalman filter recurrence algorithm is:

Mn(k)＝P(k)C ^T /[CP(k)C ^T +R] (6)

P(k)＝AP(k-1)A ^T +BQB ^T (7)

P(k)＝(En-Mn(k)C)P(k) (8)

x(k)＝Ax(k-1)+Mn(k)(y _v (k)-CAx(k-1)) (9)

y _e (k)＝Cx(k) (10)

the system state at time k at x (k) in formulas (6) - (10), the system state at time k-1 at x (k-1), A, B, R are system parameters, C is a matrix, A ^T Is the transposed matrix of matrix A, B ^T Is the transposed matrix of matrix B, C ^T Is the transposed matrix of the C matrix, y _e (k) The output signal is corrected by a Kalman filter, P (k) is covariance of the moment of a system k, P (k-1) is covariance of the moment of the system k-1, en is a unit vector, and Mn (k) is an intermediate variable;

en is a unit vector, the covariance errcov (k) of the systematic error is:

errcov(k)＝CP(k)C ^T (11)

in the formula (11), errcov (k) is the covariance of the systematic error, C is the matrix, C ^T Is the transpose of the C matrix, and P (k) is the covariance of the system at time k;

according to kirchhoff's voltage law, constructing a loop model of a corner motor and a torque motor:

the electrical equation of the corner motor is as follows:

in the formula (12): l is the inductance of the corner motor; r is R ₂ The resistor is a corner motor resistor; k (k) _b2 Is an electromotive force constant; u (u) ₂ Is the input voltage of the corner motor,

is the current of the corner motor, ">

Is the angular acceleration, k of the angular motor _b2 Is the stiffness of the corner motor;

the torque motor electrical equation is:

wherein: l is the inductance of the torque motor; r is R ₃ The resistance of the torque motor; k (k) _b3 Is an electromotive force constant; u (u) ₃ Is the input voltage of the torque motor, i _a3 Is the current of the torque motor and,

is the angular acceleration, k of the torque motor _b3 Is the stiffness of the corner motor.

3. The method according to claim 2, wherein the step 2 of forming the active fault tolerance policy 1, or the active fault tolerance policy 2, or the fault mitigation policy 1, or the flow of the fault mitigation policy 2 comprises:

1) When the corner motor and the torque motor work normally, the two motors act together to control the front wheel steering angle and the yaw rate of the automobile, and a fault-tolerant strategy is not needed at this time; under normal operation of the two motors, the rack motion is analyzed as follows:

The differential equation of motion of the rack is:

wherein: m is m _rack The mass of the rack is that of the rack; y is _rack Is the displacement of the rack; r is (r) _L The main pin shaft is biased; k (K) _L Is the rigidity of the steering tie rod; b (B) _rack Is a rack damping coefficient; f (F) _frrack G is the reduction ratio of the double-speed reducer mechanism for the friction force between the systems; t (T) _g2 Is the output torque of the corner motor; t (T) _g3 Is the output torque of the torque motor;

for rack acceleration +.>

Is the movement speed of the rack; delta _f Is the steering angle of the steering front wheel;

the differential equation of motion of the wheel is:

in formula (15): j (J) _w Is the rotational inertia of the front wheel; t (T) _frkp Is a friction torque; b (B) _kp Damping coefficient of the kingpin;

steering wheel acceleration, +.>

For steering the angular velocity of the front wheels, M _Z The aligning moment of the wheels is;

2) When the corner motor is normal and the torque motor is semi-normal, the system carries out fault relief strategy 1, the corner motor mainly carries out automobile yaw rate control, and the torque motor compensates the compensation torque delta T fed back by the yaw rate controller ₁ ；

For the complex delta T ₁ ＝ΔT ₁₁ +ΔT ₂₁ +ΔT ₃₁ (16)

Wherein DeltaT ₁ To make the total compensation torque delta T ₁₁ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂₁ Compensation torque, delta T, formed by road disturbance ₃₁ Compensating torque formed by system friction;

in the formula (17), m _rack The mass of the rack is that of the rack; y is _rack Is the displacement of the rack; r is (r) _L The main pin shaft is biased; k (K) _L Is the rigidity of the steering tie rod; b (B) _rack Is a rack damping coefficient; f (F) _frrack G is the reduction ratio of the double-speed reducer mechanism for the friction force between the systems; t (T) _g2 Is the output torque of the corner motor; t (T) _g3 Is the output torque of the torque motor;

3) When the corner motor is semi-normal and the torque motor is normal, the fault relief strategy 2 is adopted, the torque motor is used as the function of the corner motor to perform main control, the corner motor is used as the function of the torque motor to perform compensation torque delta T fed back by the compensation yaw rate controller ₂ ；

For the complex delta T ₂ ＝ΔT ₁₂ +ΔT ₂₂ +ΔT ₃₂ (18)

Wherein DeltaT ₂ To make the total compensation torque delta T ₁₂ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂₂ Compensation torque, delta T, formed by road disturbance ₃₂ Compensating torque formed by system friction;

4) When the corner motor is normal and the torque motor is totally failed, an active fault-tolerant strategy 1 is adopted, the current input of the torque motor is cut off, the corner motor is independently controlled, and the compensation torque delta T fed back by the compensation yaw rate controller is carried out ₃ ；

To the healdTotal delta T ₃ ＝ΔT ₁₃ +ΔT ₂₃ +ΔT ₃₃ (20)

Wherein DeltaT ₃ To make the total compensation torque delta T ₁₃ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂₃ Compensation torque, delta T, formed by road disturbance ₃₃ Compensating torque formed by system friction;

In the formula (21), m _rack The mass of the rack is that of the rack; y is _rack Is the displacement of the rack; r is (r) _L The main pin shaft is biased; k (K) _L Is the rigidity of the steering tie rod; b (B) _rack Is a rack damping coefficient; f (F) _frrack G is the reduction ratio of the double-speed reducer mechanism for the friction force between the systems;

5) When the corner motor has complete faults, the torque motor is normal, the current input of the corner motor is cut off by adopting an active fault-tolerant strategy 2, the torque motor is independently controlled, the torque motor serves as the function of the corner motor, and the compensation torque delta T fed back by the compensation yaw rate controller is carried out ₄ ；

To which ΔT is integrated ₄ ＝ΔT ₁₄ +ΔT ₂₄ +ΔT ₃₄ (22)

Wherein DeltaT ₄ To make the total compensation torque delta T ₁₄ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂₄ Compensation torque, delta T, formed by road disturbance ₃₄ Compensating torque formed by system friction;

4. the method according to claim 2, wherein in step 4, the control framework of the μ -integrated robust controller comprises:

a) Yaw rate tracking, ||Z ₁ || ₂ ＝||W ₁ (ω _r ^* -ω _r )|| ₂ (24)

Wherein W is ₁ Is typically arranged as a low pass filter W as a weighting function ₁ ＝k ₁ (as+b)/(cs+d) (25)

In the formulas (24) (25), Z ₁ || ₂ 2 norms omega of evaluation output of controlled object _r ^* Is the ideal yaw rate value omega _r Is the yaw rate value of the actual automobile, W ₁ A, s, b, a, d are parameters of the low pass filter, which are weighting functions;

The mu comprehensive robust controller outputs corresponding compensation torque and transmits the compensation torque delta T to the two-machine compensation unit;

b) And (3) compensation feedback and stability control: Δt=Δt ₁ +ΔT ₂ +ΔT ₃ (26)

Wherein DeltaT is the total compensation torque DeltaT ₁ Make the compensation torque, deltaT needed to compensate the yaw rate difference ₂ Compensation torque, delta T, formed by road disturbance ₃ Compensating torque formed by system friction.

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