CN109808764B - Wire control steering device with redundancy function and control method - Google Patents

Abstract

The invention discloses a wire control steering device with a redundancy function and a control method, wherein the wire control steering device with the redundancy function comprises a road feel simulation actuator, a steering actuator and a wire control steering control module; the steering actuator comprises a first gear-rack mechanism, a first rack travel sensor, a first steering motor controller, a first steering motor rotor position sensor, a second gear-rack mechanism, a second rack travel sensor, a second steering motor controller, a second steering motor rotor position sensor and a steering machine. According to the invention, through the redundant first steering motor and the first steering motor controller and the second steering motor controller, the steering-by-wire system can still normally steer when a fault occurs, and the safety of passengers in the vehicle is ensured.

Description

A wire-controlled steering device with redundant function and control method

Technical Field

The present invention relates to the field of advanced vehicle steering systems and control technologies thereof, and in particular to a wire-controlled steering device with redundant functions and a control method thereof.

Background technique

With the continuous development of automobile technology, automobile steering systems have gone through four stages: mechanical steering, hydraulic power steering, electro-hydraulic steering and electric power steering. With the in-depth development of automotive electronic technology, a new type of steering system demand has received widespread attention, namely wire-controlled steering.

The steer-by-wire system eliminates the mechanical connection between the steering wheel and the steering wheel, and achieves steering entirely by electric energy, thus getting rid of the various limitations of traditional steering systems. Not only can the force transmission characteristics of vehicle steering be freely designed, but also the angle transmission characteristics of vehicle steering can be designed, thus bringing unlimited space for the design of vehicle steering characteristics, and is a major innovation in vehicle steering systems.

In recent years, the intelligentization of automobiles has been continuously promoted, and the wire-controlled steering system is an essential device for intelligent driving cars. It can not only respond to steering commands from the bus, but also hide the steering wheel, thereby providing sufficient cabin space for autonomous driving vehicles and improving the comfort of passengers in the car. Therefore, wire-controlled steering will inevitably become the fifth stage in the development history of steering systems.

At present, among the known technologies, the steer-by-wire system disclosed in the patent "A steer-by-wire system and control method for electric vehicles" (CN103587576A) includes three parts: a steer-by-wire system controller, a steering wheel force feedback module and a front wheel steering module. The control method mainly includes initialization, signal acquisition, steering wheel force feedback control and front wheel steering control. The steer-by-wire system disclosed in the patent "Steering-by-wire system and control method for steering-by-wire system" (CN107848569A) is mainly disclosed to enable the steer-by-wire system to work stably when the ignition switch is turned on. The steer-by-wire system disclosed in the patent "A redundant and fault-tolerant system and control method for automobile steer-by-wire" (CN101549707A) mainly introduces the redundant measures and redundant control methods of the system software and hardware. The steer-by-wire system disclosed in the patent "A fully decoupled steer-by-wire system" (CN107672669A) mainly introduces the mechanical structure of the steer-by-wire system. None of the published patents introduce redundant safety measures in the structure and control of the wire-controlled steering system. In particular, when the system is used for intelligent driving technology, it cannot guarantee that the vehicle can still steer normally when key components fail, thereby ensuring the safety of the passengers in the vehicle.

Summary of the invention

The object of the present invention is to provide a wire-controlled steering device and a control method with redundant functions, which can enable the vehicle to still perform normal steering when key components fail, thereby effectively ensuring the safety of passengers in the vehicle.

The present invention solves the technical problem by adopting the following technical solution: a wire-controlled steering device with redundant function, which includes a road sense simulation actuator, a steering actuator and a wire-controlled steering control module;

The road sense simulation actuator includes a steering wheel, a steering input shaft, a torque sensor, a first rotation angle sensor, a worm gear mechanism, a second rotation angle sensor, a road sense motor, a road sense motor rotor position sensor and a road sense motor controller;

The steering wheel is connected to the steering input shaft, and a torque sensor and a first rotation angle sensor are installed between the steering input shaft and the worm gear;

The road sense motor is connected to the steering input shaft through a worm gear mechanism;

A rotation angle sensor is also installed at the end of the worm gear mechanism;

The road sense motor controller is connected to the road sense motor; a road sense motor rotor position sensor is installed at the end of the road sense motor rotor;

The steering actuator includes a first rack-and-pinion mechanism, a first rack travel sensor, a first steering motor controller, a first steering motor, a first steering motor rotor position sensor, a second rack-and-pinion mechanism, a second rack travel sensor, a second steering motor controller, a second steering motor, a second steering motor rotor position sensor and a steering gear;

The first steering motor is connected to the steering gear via a first rack-and-pinion mechanism, and the second steering motor is connected to the steering gear via a second rack-and-pinion mechanism, and the first rack-and-pinion mechanism and the second rack-and-pinion mechanism are coaxially arranged;

A first rack travel sensor is integrated inside the first rack and pinion mechanism, and a second rack travel sensor is integrated inside the second rack and pinion mechanism;

The first steering motor controller is connected to the first steering motor, and the second steering motor controller is connected to the second steering motor;

The road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected to the wire steering control module.

Optionally, the steer-by-wire control module includes a steer-by-wire controller, an acceleration sensor, a yaw rate sensor and a vehicle speed sensor;

The acceleration sensor, the yaw rate sensor and the vehicle speed sensor are all connected to the steer-by-wire controller; and the road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected to the steer-by-wire controller.

Optionally, the wire-controlled steering controller is connected to a first CAN bus and a second CAN bus; and the road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected to the first CAN bus and the second CAN bus.

The present invention has the following beneficial effects: the present invention ensures that the wire-controlled steering system can still steer normally when a fault occurs, thereby ensuring the safety of the passengers in the vehicle, by means of a redundant first steering motor and a first steering motor controller and a second steering motor and a second steering motor controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a steer-by-wire device with redundant functions according to the present invention;

Fig. 2 is a CAN network topology diagram of the present invention;

FIG3 is a flow chart of a control method of a steer-by-wire device with a redundant function;

FIG4 is a flow chart of road sense simulation control;

FIG5 is a flow chart of the front wheel steering angle control.

Detailed ways

The technical solution of the present invention is further described below in conjunction with the embodiments and drawings.

Example 1

This embodiment provides a steer-by-wire device with a redundant function, the structure of which is shown in FIG1 , and includes a road-feel simulation actuator, a steering actuator, and a steer-by-wire control module.

Among them, the road feel simulation actuator 25 includes a steering wheel 1, a steering input shaft 2, a torque sensor 3, a first angle sensor 4, a worm gear mechanism 5, a second angle sensor 6, a road feel motor 7, a road feel motor rotor position sensor 8 and a road feel motor controller 9.

The steering wheel 1 is connected to the steering input shaft 2 to obtain the driver's driving intention. A torque sensor 3 and a first angle sensor 4 are installed between the steering input shaft 2 and the worm gear 5 to detect the driver's hand force and the steering wheel angle.

The road sense motor 7 is connected to the steering input shaft 2 through the worm gear mechanism 5 to simulate the road sense feedback torque; a rotation angle sensor 6 is also installed at the end of the worm gear mechanism 5 to serve as a redundant backup for rotation angle measurement.

The road sense motor 7 and the road sense motor controller 9 can be installed in an integrated manner or arranged in a separate manner. The road sense motor controller 9 is connected to the road sense motor 7 and the wire-controlled steering controller 10, and is used to receive the torque command of the wire-controlled steering controller 10 and control the road sense motor 7 to output the steering resistance; a road sense motor rotor position sensor 8 is installed at the end of the rotor of the road sense motor 7 to measure the road sense motor rotor position in real time.

The steering actuator 26 includes a first rack and pinion mechanism 14, a first rack travel sensor 15, a first steering motor controller 16, a first steering motor 17, a first steering motor rotor position sensor 18, a second rack and pinion mechanism 19, a second rack travel sensor 20, a second steering motor controller 21, a second steering motor 22, a second steering motor rotor position sensor 23 and a steering gear 24.

The first steering motor 17 is connected to the steering gear 24 via the first rack-and-pinion mechanism 14 , and the second steering motor 22 is also connected to the steering gear 24 via the second rack-and-pinion mechanism 19 . The first rack-and-pinion mechanism 14 and the second rack-and-pinion mechanism 19 are coaxially arranged.

The first rack and pinion mechanism 14 has a first rack travel sensor 15 integrated therein, and the second rack and pinion mechanism 19 has a second rack travel sensor 20 integrated therein;

The first steering motor 17 and the first steering motor controller 16, the second steering motor 22 and the second steering motor controller 21 can be installed in an integrated manner or arranged in a separate manner; the first steering motor controller 16 is connected to the first steering motor 17 and the wire-controlled steering controller 10, and the second steering motor controller 21 is connected to the second steering motor 22 and the wire-controlled steering controller 10, so that the first steering motor controller 16 and the second steering motor controller 21 simultaneously receive the steering command of the wire-controlled steering controller 10, and respectively control the first steering motor 17 and the second steering motor 22, so as to steer the front wheels of the vehicle.

The steer-by-wire control module 27 includes a steer-by-wire controller 10 , an acceleration sensor 11 , a yaw rate sensor 12 , and a vehicle speed sensor 13 ;

The acceleration sensor 11 is used to measure the lateral acceleration of the vehicle, the yaw angular velocity sensor 12 is used to measure the yaw angular velocity of the vehicle, and the vehicle speed sensor 13 is used to measure the vehicle speed; the wire-controlled steering controller 10 controls the rotation of the road sense motor 7 through the road sense motor controller 9 according to the lateral acceleration, yaw angular velocity and speed of the vehicle to achieve road sense simulation; and controls the first steering motor 17 and the second steering motor 21 through the first steering motor controller 16 and the second steering motor controller 21 to achieve active steering control of the front wheels.

In this embodiment, the real-time steering wheel angle value can be measured by three methods: the first angle sensor, the second angle sensor and/or the road sense motor rotor position sensor. When one of the measurement methods fails, resulting in an erroneous or invalid measurement value, a correct steering wheel angle value can be comprehensively output through a majority ruling mechanism.

The real-time steering angle value of the front wheels of the vehicle can be measured by three methods: the first rack travel sensor, the second rack travel sensor and/or the first steering motor rotor position sensor. When one of the measurement methods fails, resulting in an erroneous or invalid measurement value, a correct front wheel steering angle value can be comprehensively output through a majority ruling mechanism.

The first steering motor and the first steering motor controller, as well as the second steering motor and the second steering motor controller, work simultaneously and are redundant with each other. When one of the steering motors or its controller fails and causes the steering motor to fail to work normally, the other steering motor can still work normally, thereby ensuring that the vehicle can steer normally under the drive of the effective motor.

The torque sensor 3 adopts the CIPOS non-contact torque sensor of Hella; the first rotation angle sensor 4 and the second rotation angle sensor 6 adopt the CIPOS non-contact rotation angle sensor of Hella; the vehicle speed sensor 9 adopts the 1H0927807D wheel speed sensor of SKTOO; the motor rotor position sensor adopts the AS5147 linear Hall sensor of Austrian Microelectronics; and the acceleration sensor adopts the BOSCH digital three-axis acceleration sensor BMA250.

More preferably, the wire-controlled steering controller is connected to the first CAN bus and the second CAN bus; and the road-sensing motor controller, the first steering motor controller and the second steering motor controller are all connected to the first CAN bus and the second CAN bus to realize the CAN communication redundancy function. At this time, under normal working conditions, the wire-controlled steering controller sends a road-sensing simulation instruction to the road-sensing motor controller through the first CAN bus, and then sends a front wheel steering angle instruction to the first steering motor controller and the second steering motor controller through the second CAN bus to perform front wheel steering control; when the second CAN bus fails, the wire-controlled steering controller can send a front wheel steering instruction to the first steering motor controller through the first CAN bus to control the steering of the vehicle. The road-sensing motor controller also plays the role of redundant backup for the wire-controlled steering controller in the network. When the wire-controlled steering controller fails, the road-sensing motor controller can send a steering instruction to the first steering motor controller through the first CAN bus, and the vehicle still has a normal steering function.

Compared with the prior art, the present invention has the following advantages:

1. Save space: Since the mechanical connection between the steering wheel and the steering gear is eliminated, the steering wheel can be hidden or eliminated, thus providing sufficient cabin space and improving ride quality.

2. Energy saving: By eliminating the mechanical steering column, the vehicle can reduce weight by about 5 kg, which can improve the vehicle's fuel economy and save energy.

3. Improved comfort: The steering feel, steering sensitivity and steering lightness can be set according to different drivers to bring a comfortable driving experience to the driver.

4. Performance improvement: Factors such as variable transmission ratio and direct front wheel control have greatly improved the vehicle's handling stability and yaw response.

5. Safety: Key actuators, sensors, communication networks, etc. are equipped with redundancy measures to ensure that when a fault occurs, the wire-controlled steering system can still steer normally, thus ensuring the safety of the passengers in the vehicle.

Example 2

3 , this embodiment provides a control method for a steer-by-wire device with redundant functions, which is used to control the steer-by-wire device with redundant functions as described in Embodiment 1, and includes:

S10, identifying the driver's steering behavior by collecting information such as vehicle speed, steering wheel angle, steering wheel speed, vehicle yaw acceleration, and vehicle lateral acceleration;

S20, by identifying the driver's steering behavior, the steering resistance of the vehicle is estimated, and the road feeling information of the current driving condition is estimated. The flow chart of the road feeling simulation control (road feeling information estimation) is shown in FIG4, which includes four parts: steering load observation, virtual power control, corner limit control, and road feeling torque synthesis.

1) Steering load observation is the calculation of steering resistance, including lateral force restoring torque and gravity restoring torque.

The calculation formula of the lateral force return moment is:

Where, _{Ta_l} is the lateral force restoring torque, m is the vehicle mass, b is the distance from the center of mass to the rear axle, L is the wheelbase, _ay is the lateral acceleration, and ξ is the front wheel turning angle.

The calculation formula of gravity self-aligning torque is:

Where _{Ta_w} is the gravity self-aligning torque, _Kaw is the gravity self-aligning coefficient, _ξsw is the steering wheel angle, and i is the steering gear ratio.

2) Virtual power steering control is the force input of the electric steering system to the steering system, simulating the power assist obtained by the driver when operating the steering wheel when the traditional electric steering system is working. It mainly includes basic power assist control, active return control, friction compensation and damping compensation.

Basic power-assist control is to look up the table to obtain the steering assist T _ast provided to the driver under the current working condition according to the steering force applied by the driver to the steering wheel and the current vehicle speed;

Active return control is when the driver needs the steering wheel to return to the middle position, the wire control system performs position control to control the steering wheel to return to the center position. This patent adopts PID closed-loop control, and the control method is as follows:

Where, T _rtc is the return torque, θ _t is the return target angle, θ _s is the current actual angle, K _p , _Ki , and K _d are PID control parameters. Since the goal of the return control is to return the steering wheel to the middle position, θ _t = 0, so the above formula can be expressed as:

Friction compensation is to compensate for the mechanical friction in the steering system to increase the dynamic response of the steering system. The calculation formula is:

T _f =K _f ·sgn(ω _m )

Where _Tf is the friction compensation torque, _Kf is the friction compensation coefficient, and sgn( _ωm ) is the rotation direction of the road sensing motor.

Damping compensation is to compensate the damping of the steering system to increase the dynamic response of the system. The calculation formula is:

T _d =K _d ·sgn(T _m )abs(ω _m )

Where _Td is the damping compensation torque, sgn( _Tm ) is the steering wheel torque direction, and _ωm is the road sense motor speed.

3) Angle limit control. Since there is no mechanical connection between the steering wheel and the steering gear of the wire control system, the steering wheel can be rotated unlimitedly under the driver's operation. In order to simulate the actual vehicle operation conditions, it is necessary to prevent the steering wheel from continuing to rotate at a certain angle, which is the angle limit control. The calculation method is:

T _dp ＝K _dp θ _s

Where T _dp is the limiting torque, K _dp is the limiting coefficient, and θ _s is the steering wheel angle.

4) Road feel torque comprehensive control is to comprehensively calculate the steering resistance torque obtained by steering load observation, the power assist torque obtained by virtual power assist control and the torque obtained by angle limit control to obtain the target execution torque required by the road feel simulation motor.

S30, calculating the ideal steering transmission ratio of the current steering condition by identifying the steering behavior of the driver and the driving state of the vehicle, and calculating the angle that the front wheels of the vehicle need to turn under the current steering wheel angle input through the changed transmission ratio;

Variable transmission ratio control is based on the ideal yaw rate gain, which flexibly changes the steering system transmission ratio value, so that the car can obtain similar steering response when turning at different speeds, and improve the steering flexibility of the car at low speeds and the handling stability at high speeds. Variable transmission ratio control mainly includes basic transmission ratio calculation and transmission ratio increment calculation. The basic transmission ratio calculation is calculated based on the current steady-state lateral acceleration of the vehicle. The calculation formula for steady-state lateral acceleration is:

Where _ay is the lateral acceleration, u is the vehicle speed, L is the wheelbase, K is the understeer, _δsw is the steering wheel angle, and i is the transmission ratio.

From the above formula, the basic transmission ratio calculation formula can be deduced as:

The transmission ratio increment calculation is obtained by closed-loop following the ideal yaw rate. The calculation formula of the ideal yaw rate is:

Where Yaw is the ideal yaw rate, u is the vehicle speed, L is the wheelbase, K is the understeer degree, and δ _sw is the steering wheel angle.

The closed-loop following adopts the PID control algorithm, so the transmission ratio increment calculation formula is:

Where i _inc is the incremental transmission ratio, K _p , _Ki , and K _d are PID control parameters, Yaw is the ideal yaw angular velocity, and yaw is the actual yaw angular velocity.

The front wheel transmission ratio that is more suitable for the current driving condition can be obtained by adding the basic transmission ratio and the transmission ratio increment, and the required front wheel steering angle value can be calculated by the current steering wheel angle:

Wherein, δ _fw is the target value of the front wheel steering angle, δ _sw is the current steering wheel angle, i _bas is the basic transmission ratio, and i _inc is the incremental transmission ratio.

S40, performing position closed-loop control on the front wheel angle of the vehicle to obtain an input torque command required by the steering motor;

Front wheel steering control includes closed-loop control of the front wheel angle so that the wheel follows the steering wheel. It also involves dual motor coordinated control so that the dual motors run synchronously without interfering with each other. The front wheel steering control flow chart is shown in Figure 5. The control steps are as follows:

1) Calculate the optimal front wheel steering angle required for the current vehicle driving condition by combining the driver's steering wheel angle input and the ideal transmission ratio obtained in the variable transmission ratio control;

2) Differentiate the front wheel steering angle requirement value obtained in step 1 to obtain the speed feedforward value;

3) The front wheel angle obtained in step 1 and the actual position of the front wheel are closed-loop controlled to obtain a speed feedback value;

4) Differentiate the speed feedforward obtained in step 2 to obtain the torque feedforward;

5) The speed feedforward value obtained in step 2 and the speed feedback value obtained in step 3 are summed to obtain a speed target value, and the speed target value and the current front wheel speed are closed-loop controlled to obtain a torque feedback value;

6) Sum the torque feedforward value obtained in step 4 and the torque feedback value obtained in step 5 to obtain the steering torque target value, and distribute the torque target value to the two steering actuator motors.

S50: Use the allocated torque as the target value to drive the first steering motor and the second steering motor to output corresponding torque, so that the front wheels of the vehicle follow the target rotation angle required by step 4.

The order of the above embodiments is only for the convenience of description and does not represent the advantages or disadvantages of the embodiments.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (3)

1. The steering-by-wire device with the redundancy function is characterized by comprising a road feel simulation actuator, a steering actuator and a steering-by-wire control module;

The road sense simulation executor comprises a steering wheel, a steering input shaft, a torque sensor, a first rotation angle sensor, a worm and gear mechanism, a second rotation angle sensor, a road sense motor rotor position sensor and a road sense motor controller;

the steering wheel is connected with a steering input shaft, and a torque sensor and a first rotation angle sensor are arranged between the steering input shaft and the worm gear;

the road sensing motor is connected with the steering input shaft through a worm and gear mechanism;

the tail end of the worm and gear mechanism is also provided with a second rotation angle sensor;

The road sensing motor controller is connected with the road sensing motor; the tail end of the road sensing motor rotor is provided with a road sensing motor rotor position sensor;

The steering actuator comprises a first gear-rack mechanism, a first rack travel sensor, a first steering motor controller, a first steering motor rotor position sensor, a second gear-rack mechanism, a second rack travel sensor, a second steering motor controller, a second steering motor rotor position sensor and a steering machine;

The first steering motor is connected with the steering machine through a first gear-rack mechanism, the second steering motor is connected with the steering machine through a second gear-rack mechanism, and the first gear-rack mechanism and the second gear-rack mechanism are coaxially arranged;

A first rack travel sensor is integrated inside the first rack and pinion mechanism, and a second rack travel sensor is integrated inside the second rack and pinion mechanism;

the first steering motor controller is connected with a first steering motor, and the second steering motor controller is connected with a second steering motor;

the road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected with the steer-by-wire control module;

the steer-by-wire control module comprises a steer-by-wire controller, an acceleration sensor, a yaw rate sensor and a vehicle speed sensor;

The acceleration sensor, the yaw rate sensor and the vehicle speed sensor are all connected to the steer-by-wire controller; the road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected with the steer-by-wire controller;

the wire control steering controller is connected to the first CAN bus and the second CAN bus; and the road sensing motor controller, the first steering motor controller and the second steering motor controller are all connected to the first CAN bus and the second CAN bus.

2. A control method of a steering-by-wire apparatus having a redundancy function, characterized by controlling the steering-by-wire apparatus having a redundancy function according to claim 1,

The control method comprises the following steps:

s10, identifying the steering behavior of a driver by collecting the vehicle speed, the steering wheel angle, the steering wheel rotating speed, the vehicle yaw acceleration and the vehicle lateral acceleration;

s20, estimating steering resistance when the vehicle runs through the identification of steering behaviors of a driver, and finishing the estimation of road feel information of the current running working condition;

S30, calculating an ideal steering transmission ratio of the current steering working condition by identifying the steering behavior of a driver and the running state of the vehicle, and calculating the angle required to rotate by the front wheels of the vehicle under the current steering wheel angle input through the changed transmission ratio;

S40, performing position closed-loop control on the front wheel steering angle of the vehicle to obtain an input torque command required by a steering motor;

S50, taking the distributed moment as a target value, driving the first steering motor and the second steering motor to output corresponding moments, and enabling the front wheels of the vehicle to follow the required target rotation angle;

Wherein S40 includes:

1) The optimal front wheel steering angle demand required by the current vehicle running working condition is calculated by combining the steering angle input of the steering wheel by the driver and the ideal transmission ratio obtained in the variable transmission ratio control;

2) Differentiating the front wheel steering angle demand value obtained in the step1 to obtain a rotating speed feedforward quantity;

3) Performing closed-loop control on the front wheel corner obtained in the step 1 and the actual position of the front wheel to obtain a rotating speed feedback quantity;

4) Differentiating the rotating speed feedforward quantity obtained in the step 2 to obtain a moment feedforward quantity;

5) Summing the rotating speed feedforward quantity obtained in the step 2 and the rotating speed feedback quantity obtained in the step 3 to obtain a rotating speed target value, and performing closed-loop control on the rotating speed target value and the current front wheel rotating speed to obtain a moment feedback quantity;

6) And (3) summing the moment feedforward quantity obtained in the step (4) and the moment feedback quantity obtained in the step (5) to obtain a steering moment target value, and distributing the moment target value to two steering executing motors.

3. The control method according to claim 2, wherein the estimation of the road feel information includes steering load observation, virtual assist control, corner limit control, and road feel torque integration.