CN109733464B - Active fault tolerance and fault relief system based on steer-by-wire double motors and control method thereof - Google Patents
Active fault tolerance and fault relief system based on steer-by-wire double motors and control method thereof Download PDFInfo
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Abstract
The application discloses an active fault tolerance and fault relief system based on a steer-by-wire double motor and a mode switching control method thereof, wherein the system comprises an acquisition unit, a steering wheel assembly, an ECU (electronic control unit) control module and a front wheel steering assembly which are sequentially connected, and a fault tolerance controller; the control method comprises the steps that an acquisition unit transmits acquired automobile signals to an ECU control module, and then a fault-tolerant control strategy unit, a yaw rate calculation unit, a stability control unit and a double-machine compensation unit are used for selecting corresponding compensation strategies and acting on a rack mechanism; the system and the method provided by the application can switch between the active fault tolerance mode and the fault relief mode according to different fault conditions of the fault motor, so that the optimal control of the real-time performance of the automobile is realized, and the running performance and higher performance of the automobile under the field fault condition of the automobile are ensured.
Description
Technical Field
The invention relates to the technical field of a steer-by-wire system and a fault-tolerant control system, in particular to a steer-by-wire dual-motor fault-tolerant system and a mode switching control method thereof, which can switch working mode functions under different fault conditions according to the steer-by-wire dual-motor and ensure good running performance and cruising ability of an automobile.
Background
Currently, two types of hardware redundancy and software redundancy are commonly adopted for fault tolerance of automobiles. The hardware redundancy can be replaced by new hardware when the automobile breaks down, so that the normal running of the automobile is ensured; however, the hardware redundancy mode increases the economic cost of the automobile, does not consider the real-time fault condition of the automobile, cannot realize the real-time optimal allocation of the automobile, and is a relatively conservative fault-tolerant mode. The software redundancy is a mode of reducing the development cost of hardware redundancy by using the software redundancy, and the core mode of the software redundancy is an active fault tolerance mode, and the mode replaces error data measured by failure of a sensor and the like by using the deduced approximate correct data through identification and deduction of other groups of correct data, so that the chain error caused by failure of certain sensors can be solved, and the development cost of fault tolerance can be greatly reduced. However, some actuators are not suitable to be completely replaced by an active fault tolerance mode, because the fault of some actuators not only can cause data errors, but also can directly influence the execution effect of the automobile. For example, an execution motor for steering by wire of an automobile, a single steering execution motor fails, the steering influence caused by failure of the steering motor cannot be replaced only by adopting an active fault-tolerant mode, and the failure of the steering execution motor of a unique actuator under a field working condition cannot be guaranteed, so that the normal running and the optimal control of the automobile can be realized.
The problem of the failure of the actuator cannot be solved by a single active fault-tolerant mode, and the problem of real-time optimization of the running of the automobile cannot be solved by a single hardware redundancy mode or by combining the hardware redundancy mode with the active fault-tolerant mode, so that the resource waste of the failed actuator can be caused.
Disclosure of Invention
Aiming at the defects of the existing fault-tolerant concept and the prior art, the invention provides a novel fault-tolerant concept-fault relief, provides an active fault-tolerant and fault link system based on a steer-by-wire double-execution motor and a mode switching method thereof, greatly improves the safety, reliability and real-time superiority of performance of the system by combining hardware redundancy with active fault tolerance and fault relief on the basis of ensuring the safety, realizes perfect fusion of automobile safety and reliability, solves the problem that the automobile cannot operate or performance is suddenly reduced under the condition of single motor fault, solves the problem that the performance of the fault motor is wasted due to direct isolation of the hardware redundancy and the active fault-tolerant technology, and solves the problem that the real-time optimal performance of the automobile cannot be realized according to the type of the automobile fault in the running process of the automobile.
The invention is realized by the following technical scheme:
first, the present invention provides an active fault tolerance and fault mitigation system based on steer-by-wire dual motors, the system comprising: the system comprises an acquisition unit, a steering wheel assembly, an ECU control module and a dual-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 rotation 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 sensor for acquiring the state of the automobile by a yaw rate sensor; and the collected signals or instructions are respectively transferred to an ECU control module, a steering wheel assembly and a double-machine execution unit, specifically: the acquisition unit transmits a vehicle speed signal, a steering wheel rotation angle signal, a rotation angle signal of a steering motor obtained by a rotation 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, a rotation angle signal of a steering front wheel and the like 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 signals of the ideal yaw rate and the actual yaw rate obtained by the yaw rate calculation unit, the road surface interference side wind interference and other signals are sent to a dual-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, and mainly comprises an operation controller 7 and a fault-tolerant controller 18, wherein the operation controller 7 comprises a motor fault diagnosis unit and an electronic control unit; the fault-tolerant controller 18, namely a fault-tolerant controller, comprises 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 signals from the acquisition unit, and transmits corresponding instructions to the dual-computer execution unit for action after calculation; specifically, the motor fault diagnosis unit is a self-adaptive Kalman filter so as to realize the on-line identification of the resistance, current and voltage of the corner motor and the torque motor, and the motor fault diagnosis unit judges the state of the motor according to the real-time resistance, current and voltage signals of the corner motor and the torque motor transmitted by the acquisition unit and transmits the actual voltage and current signals of the motor to the fault-tolerant controller.
The fault-tolerant controller 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 comprehensively considers the influence of road surface interference, crosswind, system friction and the like on the stability of the automobile according to the yaw rate difference value transmitted by the yaw rate calculation unit, and obtains compensation torque and transmits the compensation torque to the double-machine fault-tolerant compensation unit on the premise of ensuring the stability of the automobile from the aspect of system robustness; the dual fault tolerance compensation unit receives the compensation torque signal transmitted by the stability control unit, and controls the torque motor 13 to act through the torque motor controller 16 according to the fault tolerance strategy of the fault tolerance control strategy unit so as to compensate the system, thereby realizing the active fault tolerance or fault relief of faults.
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, wherein the steering wheel 1 is connected with the road sensing motor 3 and a steering wheel angle sensor 4 thereof through a steering column 2, and a steering wheel moment sensor 5 is arranged on the steering column 2; the road-sensing motor controller 6 is connected with the road-sensing motor 3 and the steering wheel torque sensor 5 and controls 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 which are connected in sequence; the corner motor 10, the torque motor 13, the bipolar speed reducer 11 and the speed reducer 14 are connected with the gear rack steering device 15, the front wheels 17 are arranged on two sides of the gear rack steering device 15, the front wheel steering angle sensor 9 is arranged on the front wheels 17, the corner sensor 9 is connected with the front wheel torque sensor 12 through an F1 external bus, signals of the corner motor controller 8 and the torque motor controller 16 are input into the bus, and then transmitted to the fault-tolerant controller 18 through the bus; the corner motor 10 and the speed reducing mechanism 11 thereof are connected with the corner control unit 8, the corner motor control unit 8 controls the operation of the corner motor 10 and the bipolar speed reducer 11, the torque motor 13 and the speed reducer 14 are connected with the 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 Flexray bus; the fault-tolerant controller 18 receives signals from the front wheel torque motor sensor 12, the front wheel steering angle motor sensor 9, the steering wheel torque sensor 5 and signals from the arithmetic controller 7, performs control of a robust control and compensation strategy, inputs instructions into the Flexery bus, and transmits the instructions to the angle motor controller 8 and the torque motor controller 16 to operate the corresponding motors.
The invention further provides a mode switching control method of the active fault tolerance and fault relief system based on the drive-by-wire steering double motor, which comprises the following steps:
step 1: the acquisition unit drives the corner motor R 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 3: the yaw rate calculation unit calculates the direction according to the real-time acquisition of the acquisition unitDisc rotation angle signal delta 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 mu comprehensive robust controller control to improve the capability of the system for resisting external interference, 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 and the steering wheel assembly by receiving the fault-tolerant strategy transmitted by the fault-tolerant controller, so that the automobile can have a good yaw rate control effect and good stability.
Further, in the mode switching control method of the active fault tolerance and fault relief system based on the steering-by-wire dual-motor, the method further includes that a motor fault diagnosis unit is constructed in the step 1, and the on-line identification of the resistance, the current and the voltage of the corner motor and the torque motor can be realized by designing an adaptive 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), the system state at the time k at the time x (k), the system state at the time k-1 at the time x (k-1), A and 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) Is the output signal corrected by the Kalman filter, P (k) is the covariance of the system k time, P (k-1) is the covariance of the system k-1 time,en is a unit vector, 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 steering motor; r is R 2 The resistance of the steering motor; 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.
The self-adaptive Kalman filter transmits the voltage, current and resistance signals of the corner motor and the torque motor to the fault-tolerant control strategy unit.
Further, the four real-time fault-tolerant control policies formed in the step 2, the active fault-tolerant policy 1, the active fault-tolerant policy 2, the fault-relief policy 1, or the fault-relief policy 2 include:
step 2.1: the Kalman filter can determine the failure of the corner motor or the torque motor by monitoring the resistance fluctuation beyond the normal range. When the maximum output voltage of the motor is greater than the safety margin voltage, i.e., U > =0.5u, from the viewpoint of motor performance optimization max ，U 0 ＝0.5U max When the motor can be considered to exert part of the motor function and output certain torque, the torque T=f (I), which is the premise of a fault relief strategy, and the higher output voltage capability is the guarantee that the motor can perform compensation work;
in order to prevent the corner motor or the torque motor from being unable to timely output enough torque from the safety aspect, 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 can be considered to be incapable of functioning, the fault motor can not 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 The method comprises the steps of carrying out a first treatment on the surface of the Forming a fault vector table according to the fault conditions of the corner motor and the torque motor, wherein the fault vector table comprises the running states of the corner motor and the torque motor and the corresponding fault conditions; the fault vector table is as follows:
fault vector meter
| Fault vector | Failure condition |
| 03 | Two motors are normal |
| 25 | Full failure of two motors |
| 04 | The corner motor is normal and the torque motor is semi-normal |
| 13 | The rotation angle motor is half normal and the torque motor is normal |
| 05 | The corner motor is normal and the torque motor is totally failed |
| 23 | Full fault of corner motor and |
| 15 | Half normal rotation angle motor and full fault of torque motor |
| 24 | Full fault of corner motor and half |
| 14 | Half-normal rotation angle motor and half-normal torque |
The fault-tolerant strategy adopted in the step 2 specifically comprises the following steps:
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 steering motor 2; t (T) g3 Is the output torque of the steering motor 3;
for rack acceleration +.>
Is the movement speed of the rack;
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 T 11 Make the compensation torque, T, needed to compensate the yaw rate difference 21 Compensation torque formed by road surface interference T 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 steering motor 2; t (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, 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 T 12 Make the compensation torque, T, needed to compensate the yaw rate difference 22 Compensation torque formed by road surface interference T 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 which ΔT is integrated 3 ＝ΔT 13 +ΔT 23 +ΔT 33 (20)
Wherein DeltaT 3 To make the total compensation torque T 13 Make the compensation torque, T, needed to compensate the yaw rate difference 23 Compensation torque formed by road surface interference T 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; t (T) g2 Is the output torque of the steering motor 2; t (T) a3 Is the output torque of the steering motor 3;
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 T 14 Make the compensation torque, T, needed to compensate the yaw rate difference 24 Compensation torque formed by road surface interference T 34 Compensating torque formed by system friction;
6) When two motors are normal, a fault tolerance strategy does not need to be applied, and when both motors have faults (semi-normal or full faults), the probability is small and is not in the scope of the application.
Further, in the mode switching control method of the active fault tolerance and fault mitigation system based on steer-by-wire dual motors, in the step 4, the control framework of the μ integrated robust controller includes:
a) Yaw rate tracking, ||Z 1 || 2 ＝||W 1 (ωr * -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)
(24) ((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 can quickly track the difference value between the ideal yaw rate and the actual yaw rate under different fault tolerance strategies, has better interference suppression on external interference such as ground interference and crosswind interference, or outputs corresponding compensation torque and transmits the compensation torque delta T to the double-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.
In the invention, the fault tolerance concept of fault relief is proposed relative to the traditional fault tolerance concept. The traditional research thinking is to adopt a hardware redundancy or software redundancy mode, wherein the hardware redundancy is considered to replace the failed hardware by new hardware, separate the failed hardware from the system, or adopt a software redundancy mode to replace the hardware redundancy by software redundancy, and replace the data of the failed component by deduction through calculation data of other sensors or actuators. In practice, this is a relatively conservative fault-tolerant manner, essentially replacing the faulty component with a new component, replacing the erroneous data with other data, and the vehicle at this time may be referred to as "no-disease operation". However, the residual functions of the fault components are not fully developed and wasted, for example, the motor is not completely paralyzed after the fault occurs, a part of functions can be used for outputting certain torque, the fault motor and the normal motor can be adopted to work simultaneously aiming at different fault working conditions of the motor, and the automobile at the moment can be called as 'work with disease'. According to the method and the device, real-time optimal control of the automobile is achieved through matching and comparison of the fault motor and the normal motor. Meanwhile, the better working capacity and performance of the automobile in an extreme field environment can be ensured, and the guarantee is provided for repairing the automobile to the most advanced maintenance point.
Compared with the prior art, the steering-by-wire double-motor system and the fault-tolerant mode switching control method thereof realize multiple steering mode functions in the automobile steering-by-wire system, switch the steering modes according to different faults of the double motors of the automobile steering, realize real-time optimal control of the automobile, unify the economical efficiency and the flexibility of the steering-by-wire automobile, fully utilize the residual functions of fault components, save resources and have wide market application prospect.
Drawings
Fig. 1 is a schematic diagram of the structural arrangement of the steer-by-wire dual motor system of the present invention.
Fig. 2 is a schematic diagram of a control device of the drive-by-wire steering double-motor active fault tolerance and fault relief fault tolerance system of the invention.
FIG. 3 is a general diagram of the control strategy of the drive-by-wire dual motor active fault tolerance and fault mitigation fault tolerance system of the present invention.
FIG. 4 is a block diagram of a steer-by-wire dual motor vehicle stability control system with fault tolerance based on yaw rate feedback.
In the figure, 1, a steering wheel; 2. a steering column; 3. a road-sensing motor; 4. steering wheel angle sensor; 5. a steering wheel torque sensor; 6. a road-sensing motor controller; 7. an arithmetic controller; 8. a corner motor controller; 9. a front wheel steering angle sensor; 10. a corner motor; 11. a bipolar decelerator; 12. front wheel torque sensor; 13. a torque motor; 14. a speed reducer; 15. a rack and pinion mechanism; 16. a torque motor controller; 17. a front wheel; 18. a fault tolerant controller; 19. a vehicle speed sensor.
Detailed Description
The invention will be further described with reference to examples and drawings, to which reference is made by way of illustration, but not limitation, for the understanding of those skilled in the art.
Referring to fig. 1, a layout of an active fault tolerance and fault mitigation system based on steer-by-wire dual motors of the present invention on a vehicle body includes: the system comprises an acquisition unit, a steering wheel assembly, an ECU control module (model MT20U2, in specific implementation, M7 or MT20U can also be used), and a dual-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 rotation 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, a yaw rate sensor and other sensors for acquiring the state of the automobile; the acquisition unit transmits a vehicle speed signal, a steering wheel rotation angle signal, a rotation angle signal of a steering motor obtained by a rotation 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, a rotation angle signal of a steering front wheel and the like 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 signals of the ideal yaw rate and the actual yaw rate obtained by the yaw rate calculation unit, the road surface interference side wind interference and other signals are sent to a dual-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 and mainly comprises an operation controller 7 and a fault-tolerant controller 18, wherein the operation controller 7 comprises a motor fault diagnosis unit and an electronic control unit; the fault-tolerant controller 18, namely a fault-tolerant controller, comprises 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 signals from the acquisition unit, and transmits corresponding instructions to the dual-computer execution unit for action after calculation; specifically, the motor fault diagnosis unit is a self-adaptive Kalman filter so as to realize the on-line identification of the resistance, current and voltage of the corner motor and the torque motor, and the motor fault diagnosis unit judges the state of the motor according to the real-time resistance, current and voltage signals of the corner motor and the torque motor transmitted by the acquisition unit and transmits the actual voltage and current signals of the motor to the fault-tolerant controller.
The fault-tolerant controller 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 comprehensively considers the influence of road surface interference, crosswind, system friction and the like on the stability of the automobile according to the yaw rate difference value transmitted by the yaw rate calculation unit, and obtains compensation torque and transmits the compensation torque to the double-machine fault-tolerant compensation unit on the premise of ensuring the stability of the automobile from the aspect of system robustness; the dual fault tolerance compensation unit receives the compensation torque signal transmitted by the stability control unit, and controls the torque motor 13 to act through the torque motor controller 16 according to the fault tolerance strategy of the fault tolerance control strategy unit so as to compensate the system, thereby realizing the active fault tolerance or fault relief of faults.
The steering wheel assembly is respectively connected with the acquisition unit and the ECU control module, 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 corner sensor 4 thereof through the steering column 2, and a steering wheel moment sensor 5 is arranged on the steering column 2; the road-sensing motor controller 6 is connected with the road-sensing motor 3 and the steering wheel torque sensor 5 and controls the running of the road-sensing motor 3.
The double-machine executing unit is respectively connected with the acquisition unit and the ECU control module and 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 which are sequentially connected; the corner motor 10, the torque motor 13, the bipolar speed reducer 11 and the speed reducer 14 are connected with the gear rack steering device 15, the front wheels 17 are arranged on two sides of the gear rack steering device 15, the front wheel steering angle sensor 9 is arranged on the front wheels 17, the corner sensor 9 is connected with the front wheel torque sensor 12 through a Flexray bus, signals of the corner motor controller 8 and the torque motor controller 16 are input into the bus, and then transmitted to the fault-tolerant controller 18 through the bus; the corner motor 10 and the speed reducing mechanism 11 thereof are connected with the corner control unit 8, the corner motor control unit 8 controls the operation of the corner motor 10 and the bipolar speed reducer 11, the torque motor 13 and the speed reducer 14 are connected with the 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 Flexray bus; the fault-tolerant controller 18 receives signals from the front wheel torque motor sensor 12, the front wheel steering angle motor sensor 9, the steering wheel torque sensor 5 and signals from the arithmetic controller 7, performs control of a robust control and compensation strategy, inputs instructions into the Flexery bus, and transmits the instructions to the angle motor controller 8 and the torque motor controller 16 to operate the corresponding motors.
Fig. 2 and 3 are schematic diagrams of a control device of a drive-by-wire steering double-motor active fault tolerance and fault relief fault tolerance system and a general diagram of a control strategy of the drive-by-wire steering double-motor active fault tolerance and fault relief fault tolerance system, and the control flow of the invention is as follows:
step 1: the acquisition unit drives the corner motor R 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 instructions (voltage, current and resistance signals of the torque motor) to the fault-tolerant control strategy unit;
the motor fault diagnosis unit comprises an adaptive Kalman filter for realizing on-line identification of resistance, current and voltage of the corner motor and the torque motor:
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), the system state at the time k at the time x (k), the system state at the time k-1 at the time x (k-1), A and 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) Is the output signal corrected by the Kalman filter, P (k) is the covariance of the system k time, and P (k-1) is the system kCovariance at time-1, en is unit vector, mn (k) is 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 steering motor; r is R 2 The resistance of the steering motor; 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;
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;
the process of the active fault tolerance strategy 1, the active fault tolerance strategy 2, the fault relief strategy 1 or the fault relief strategy 2 comprises the following steps:
step 2.1: the Kalman filter can determine the failure of the corner motor or the torque motor by monitoring the resistance fluctuation beyond the normal range. When the maximum output voltage of the motor is greater than the safety margin voltage, i.e., U > =0.5u, from the viewpoint of motor performance optimization max ，U0＝0.5U max When the motor can be considered to exert part of the motor function and output certain torque, the torque T=f (I), which is the premise of a fault relief strategy, and the higher output voltage capability is the guarantee that the motor can perform compensation work;
in order to prevent the corner motor or the torque motor from being unable to timely output enough torque from the safety aspect, 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 can be considered to be incapable of functioning, the fault motor can not 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 The method comprises the steps of carrying out a first treatment on the surface of the Forming a fault vector table according to the fault conditions of the corner motor and the torque motor, wherein the fault vector table comprises the running states of the corner motor and the torque motor and the corresponding fault conditions; the fault vector table is as follows:
fault vector meter
The fault-tolerant strategy adopted in the step 2 specifically comprises the following steps:
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 steering motor 2; t (T) g3 Is the output torque of the steering motor 3;
for rack acceleration +.>
Is the movement speed of the rack;
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 T 11 So that the compensation torque required to compensate for the yaw-rate difference, T2 1, compensating torque formed by road surface interference and compensating torque formed by T31 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) a2 Is the output torque of the steering motor 2; t (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, 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 T 12 Make the compensation torque, T, needed to compensate the yaw rate difference 22 Compensation torque formed by road surface interference T 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 which ΔT is integrated 3 ＝ΔT 13 +ΔT 23 +ΔT 33 (20)
Wherein DeltaT 3 is the total compensation torque, T13 is the compensation torque required for compensating the yaw rate difference, T23 is the compensation torque formed by road interference, and T33 is the compensation 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; t (T) a2 Is the output torque of the steering motor 2; t (T) a3 Is the output torque of the steering motor 3;
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 T 14 Make the compensation torque, T, needed to compensate the yaw rate difference 24 Compensation torque formed by road surface interference T 34 Compensating torque formed by system friction;
6) When two motors are normal, a fault tolerance strategy does not need to be applied, and when both motors have faults (semi-normal or full faults), the probability is small and is not in the scope of the application.
Further, in the above-mentioned mode switching control method of the active fault tolerance and fault mitigation system based on steer-by-wire dual motor, in the step 4, a control frame diagram of the μ -integrated robust controller is shown in fig. 4, K is the controller, and disturbance input ω of the system is shown in fig. 4 r For ideal yaw rate, the disturbance input is ideal front wheel rotation angle delta f * Cross wind interference Fv and road surface interference moment T r ，W 1 ，W 2 As a weighting function, a high-pass filter is usually provided. W (W) d For the interference weight matrix, ΔG is the perturbation of the unknown parameter, ΔI is the compensation current, z 1 ，z 2 To evaluate the output.
Specifically, the control framework of the μ -integrated robust controller includes:
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)
(24) ((24)) 25) Z Z || 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 Is a weighting function, a, s, b, a, d are parameters of the low-pass filterA number.
The mu comprehensive robust controller can quickly track the difference value between the ideal yaw rate and the actual yaw rate under different fault tolerance strategies, has better interference suppression on external interference such as ground interference and crosswind interference, or outputs corresponding compensation torque and transmits the compensation torque delta T to the double-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;
step 3: the yaw rate calculation unit calculates steering wheel angle signals delta s according to the steering wheel angle signals delta s acquired by the acquisition unit in real time w 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 mu comprehensive robust controller control to improve the capability of the system for resisting external interference, 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 rack mechanism by receiving the fault-tolerant strategy transmitted by the fault-tolerant controller, so that the automobile is ensured to have good yaw angular speed control effect and good stability.
The present invention has been described in terms of the preferred embodiments thereof, and it should be understood by those skilled in the art that various modifications can be made without departing from the principles of the invention, and such modifications should also be considered as being within the scope of the 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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| PCT/CN2019/116041 WO2020125249A1 (en) | 2018-12-18 | 2019-11-06 | Active fault tolerance and fault mitigation system based on steer-by-wire dual motors and control method therefor |
| US17/258,378 US20210269087A1 (en) | 2018-12-18 | 2019-11-06 | Active Fault Tolerance and Fault Mitigation System Based on Steer-by-wire with Dual Motors and Control Method Therefor |
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| CN110329248B (en) * | 2019-06-18 | 2021-02-19 | 南京航空航天大学 | Intelligent steer-by-wire system with brain-computer interaction and emergency obstacle avoidance method thereof |
| CN110758550B (en) * | 2019-10-11 | 2021-08-06 | 南京航空航天大学 | Energy optimization method of wire-controlled double-motor coupling steering system |
| CN111017010B (en) * | 2020-01-03 | 2023-11-07 | 南京航空航天大学 | Dual-motor intelligent steer-by-wire system and synchronous control method |
| CN111422249B (en) * | 2020-04-16 | 2023-01-03 | 芜湖汽车前瞻技术研究院有限公司 | Rear wheel steering control method, rear wheel steering control device and computer storage medium |
| CN112977602B (en) * | 2021-02-04 | 2022-04-08 | 南京航空航天大学 | Dual-motor steer-by-wire system and hybrid robust stability control method thereof |
| CN113086000B (en) * | 2021-04-30 | 2022-04-08 | 哈尔滨工业大学 | Fault-tolerant estimation method for rack force of steering-by-wire system |
| CN114454950B (en) * | 2021-12-30 | 2022-12-23 | 南京航空航天大学 | Dual-motor steer-by-wire system and fault-tolerant control method thereof |
| CN114454951B (en) * | 2021-12-30 | 2022-12-06 | 南京航空航天大学 | Dual-motor steer-by-wire system and convolutional neural network fault-tolerant control method thereof |
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