Steer-by-wire system and angle control method thereof

Abstract

The invention discloses a steer-by-wire system and an angle control method thereof, the system comprises a hand feeling simulator and a steering actuator, the hand feeling simulator comprises a torque sensor, a hand feeling simulator controller, a hand feeling simulator motor, a hand feeling simulator transmission mechanism and a hand feeling simulator angle sensor; the steering actuator comprises a steering actuator controller, a steering actuator angle sensor, a steering actuator transmission mechanism and a steering actuator motor, wherein the angle of the steering actuator is dynamically consistent with the steering angle obtained by the hand feeling simulator. According to the invention, the road surface actuator in the steer-by-wire system needs to follow the hand feeling simulator, so that the response characteristic of the steering actuator in the steer-by-wire system to the input angle of a driver is improved, the response accuracy of the following performance under the dynamic input scene of the driver is improved, and the transverse control precision of the vehicle is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steer-by-wire systems for automobiles, and specifically relates to a steer-by-wire system, and also relates to an angle control method for a steer-by-wire system. Background Art

[0002] The development focus of the automotive industry has shifted from traditional internal combustion engines to new energy vehicles, which is an irresistible trend. New energy vehicles bring not only changes in the power system, but also increasing requirements for the development of steer-by-wire technology.

[0003] Currently, the steer-by-wire system is a key technology in the development of current automotive chassis, which consists of a feel simulator and a steering actuator. The feel simulator is connected to the steering wheel, outputs the driver's steering angle command to the steering actuator, and at the same time feeds back the road feel to the driver. After receiving the steering angle command from the feel simulator, the steering actuator drives the wheels to rotate to achieve steering. Information is exchanged between the feel simulator and the steering actuator through electrical signals. However, affected by the signal transmission cycle and the reaction time limit of the steering actuator to respond to the angle command, the ability of the steer-by-wire system to dynamically follow the driver's steering intention is reduced compared with that of the traditional steering system, especially under the working conditions of high-speed steering.

[0004] For example: Publication No. CN107600168B discloses a steering control device and method for a steer-by-wire system, which calculates a compensation steering angle for variably controlling the output angle of the wheels based on the feedback steering angle and vehicle speed. This method belongs to changing the target angle request, but the final accuracy will be affected. Another example: Publication No. CN114261442B discloses a composite position control method for a steer-by-wire system, which divides the position control regulator into a first position regulator and a second position regulator, changing from the traditional closed-loop feedback PI control to closed-loop feedback + open-loop feedforward control, but only using the rotational speed as the feedforward signal has limited compensation.

[0005] Therefore, the steer-by-wire system using the traditional angle tracking method has low response accuracy in following the driver's dynamic input scenario, which affects the lateral control accuracy of the vehicle. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an improved steer-by-wire system.

[0007] At the same time, it also relates to an angle control method for a steer-by-wire system.

[0008] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0009] A steer-by-wire system, which includes a haptic simulator and a steering actuator. The haptic simulator includes a torque sensor, a haptic simulator controller, a haptic simulator motor, a haptic simulator transmission mechanism, and a haptic simulator angle sensor; the steering actuator includes a steering actuator controller, a steering actuator angle sensor, a steering actuator transmission mechanism, and a steering actuator motor. The angle of the steering actuator is dynamically consistent with the steering angle obtained by the haptic simulator. Among them, the torque T sum is T LFW 、T FW 、T FB The sum of the three, T LFW is the expected linear feedforward motor torque of the steering actuator calculated according to the measured value T sensor of the torque sensor of the haptic simulator and through a linear feedforward control module; T FW is the real-time torque of the steering actuator motor and the expected feedforward motor torque of the steering actuator calculated through a dynamic feedforward control module; T FB is the expected feedback motor torque of the steering actuator calculated according to the angle deviation between the driver's steering angle θ hwa and the steering actuator angle θ rwa and through a PID feedback control module.

[0010] Preferably, the driver drives the haptic simulator transmission mechanism to rotate by applying a torque on the steering wheel, thereby generating an expected steering angle, and measuring and outputting it to the haptic simulator controller through the haptic simulator angle sensor; the driver's hand torque needs to overcome the resistance torque of the haptic simulator motor and is measured by the torque sensor, and at the same time sent to the haptic simulator controller to control the haptic simulator motor to generate torque.

[0011] In some specific embodiments, the haptic simulator controller, the haptic simulator motor, the haptic simulator transmission mechanism, and the haptic simulator angle sensor are sequentially connected and form an internal closed loop.

[0012] According to a specific implementation and preferred aspect of the present invention, the steering actuator controller receives the driver's steering angle sent by the haptic simulator controller, and after comparing it with the steering actuator angle sensor, controls the steering actuator motor to generate torque to drive the steering actuator transmission mechanism to move to a position consistent with the driver's steering angle to drive the steering wheel to rotate.

[0013] In some specific embodiments, the steering actuator controller, the steering actuator motor, the steering actuator transmission mechanism, and the steering actuator angle sensor are sequentially connected and form an internal closed loop.

[0014] According to another specific implementation and preferred aspect of the present invention, the linear feedforward control module calculates the expected linear feedforward motor torque T of the steering actuator by designing a calibratable curve coefficient KL(x) based on the torque sensor signal T that changes in real time sensor as follows: LFW as follows:

[0015] T LFW = KL(x) × T sensor .

[0016] In some specific embodiments, the expected feedforward motor torque T of the steering actuator is also based on the driver's steering angle θ measured by the feel simulator angle sensor FW , and calculates the driver's steering speed hwa and acceleration and acceleration

[0017] According to another specific implementation and preferred aspect of the present invention, the dynamic feedforward control module calculates the expected feedforward motor torque T of the steering actuator by calculating the driver's steering speed and acceleration and based on the actual output torque T of the motor act as follows: FW :

[0018]

[0019] In the above formula, M rwa is the equivalent mass of the steering actuator, B rwa is the equivalent damping of the steering actuator, η is the transmission efficiency of the steering actuator, and G is the transmission ratio of the transmission mechanism of the steering actuator.

[0020] According to another specific implementation and preferred aspect of the present invention, the PID feedback control module calculates the expected feedback motor torque T of the steering actuator by calculating the deviation (θ hwa -θ rwa ) between the driver's steering angle and the steering actuator angle, and designs appropriate k p , k i , k d parameters as follows: FB :

[0021] T FB = k p × (θ hwa -θ rwa ) + k i × (θ hwa -θ rwa ) + k d × (θ hwa -θ rwa ).

[0022] Another technical solution of the present invention: An angle control method for a steer-by-wire system, which adopts the above-mentioned steer-by-wire system, and the control process in which the angle of the steering actuator is dynamically consistent with the steering angle obtained by the feel simulator is as follows:

[0023] 1) According to the measurement value T of the torque sensor of the feel simulator sensor The expected linear feedforward motor torque of the steering actuator is calculated through the linear feedforward control module. The linear feedforward control module designs a calibratable curve coefficient KL(x), and according to the torque sensor signal T that changes in real time sensor , the expected linear feedforward motor torque T of the steering actuator is calculated LFW As follows: T LFE = KL(x) × T sensor ;

[0024] 2) According to the driver's steering angle θ measured by the angle sensor of the feel simulator hwa , and the driver's steering speed is calculated and acceleration At the same time, considering the real-time motor torque of the steering actuator, the expected feedforward motor torque T of the steering actuator is calculated through the dynamic feedforward control module FW , the dynamic feedforward control module, by calculating the driver's steering speed and acceleration According to the actual output torque T of the motor act The expected feedforward motor torque T of the steering actuator is calculated FW :

[0025] In the above formula, M rwa is the equivalent mass of the steering actuator, B rwa is the equivalent damping of the steering actuator, η is the transmission efficiency of the steering actuator, and G is the transmission ratio of the transmission mechanism of the steering actuator;

[0026] 3) According to the angle deviation between the driver's steering angle θ hwa and the angle θ of the steering actuator rwa , the expected feedback motor torque T of the steering actuator is calculated through the PID feedback control module FB , the PID feedback control module calculates the deviation between the driver's steering angle and the angle of the steering actuator (θ hwa -θ rw a), designs appropriate k p , k i , k d parameters, and calculates the expected feedback motor torque T of the steering actuator FB :

[0027] T FB = k p ×(θ hwa - θ rwa ) + k i ×(θ hwa - θ rwa ) + k d ×(θ hwa - θ rwa );

[0028] 4) The final desired steering actuator motor torque T sum is the sum of T LFW , T FW , and T FB , and is sent to the steering actuator motor for execution. Therefore, the above angle control method improves the response characteristics of the steering actuator in the steer-by-wire system to the driver's input angle.

[0029] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] For the existing steer-by-wire system, only changing the target angle request results in low steering accuracy, and only using the rotational speed as a feedforward signal has limited compensation and cannot achieve the dynamic consistency between the steering angle obtained by the feel simulator and the steering actuator angle. However, the present invention cleverly solves various deficiencies of the existing system through the overall design of the steer-by-wire system. After adopting this system, the driver drives the transmission mechanism of the feel simulator to rotate by applying a torque on the steering wheel, thereby generating a desired steering angle, which is measured and output to the feel simulator controller by the angle sensor of the feel simulator; at the same time, the hand torque of the driver needs to overcome the resistance torque of the feel simulator motor, which is measured by the torque sensor and sent to the feel simulator controller. Through internal closed-loop torque control, the feel simulator motor is controlled to generate a torque. At the same time, the steering actuator controller receives the driver's steering angle sent by the feel simulator controller, compares it with the steering actuator angle sensor, and controls the steering actuator motor to generate a torque to drive the steering actuator transmission mechanism to move to a position consistent with the driver's steering angle to drive the steering wheel to rotate. Therefore, the present invention is based on the dynamic consistency between the angle of the steering actuator and the steering angle obtained by the feel simulator, realizing that the road surface actuator in the steer-by-wire system follows the feel simulator, improving the response characteristics of the steering actuator in the steer-by-wire system to the driver's input angle, improving the response accuracy of the followability in the driver's dynamic input scenario, and improving the lateral control accuracy of the vehicle.

[0031] Specific real-time manner

[0032] Figure 1Schematic diagram of the steer-by-wire system of the present invention;

[0033] Figure 2 Working schematic diagram of the steer-by-wire system of the present invention.

[0034] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will be described in detail in combination with specific real-time manners. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific real-time examples disclosed below.

[0035] As Figure 1 shown, the steer-by-wire system involved in this embodiment includes a feel simulator and a steering actuator. The feel simulator includes a torque sensor, a feel simulator controller, a feel simulator motor, a feel simulator transmission mechanism, and a feel simulator angle sensor; the steering actuator includes a steering actuator controller, a steering actuator angle sensor, a steering actuator transmission mechanism, and a steering actuator motor.

[0036] In some specific embodiments, the feel simulator and the steering actuator exchange information through electrical signals. The feel simulator controller, the feel simulator motor, the feel simulator transmission mechanism, and the feel simulator angle sensor are connected in sequence to form an internal closed loop; the steering actuator controller, the steering actuator motor, the steering actuator transmission mechanism, and the steering actuator angle sensor are connected in sequence to form an internal closed loop.

[0037] In some specific embodiments, the driver drives the feel simulator transmission mechanism to rotate by applying a torque on the steering wheel, thereby generating a desired steering angle, which is measured and output to the feel simulator controller by the feel simulator angle sensor; the hand torque of the driver needs to overcome the resistance torque of the feel simulator motor and is measured by the torque sensor, and is sent to the feel simulator controller at the same time to control the feel simulator motor to generate a torque; after receiving the driver's steering angle sent by the feel simulator controller and comparing it with the steering actuator angle sensor, the steering actuator controller controls the steering actuator motor to generate a torque to drive the steering actuator transmission mechanism to move to a position consistent with the driver's steering angle to drive the steering wheel to rotate.

[0038] Combined with Figure 2 shown, in order to achieve the dynamic consistency of the angle of the steering actuator described above with the steering angle obtained by the feel simulator (here, there is a following relationship between the actuator and the feel simulator, or rather, the purpose of the present application is that the road actuator in steer-by-wire should follow the feel simulator), it is necessary to design a control method as shown in the schematic diagram of the invention, and the process includes:

[0039] 1) Calculate the expected linear feedforward motor torque of the steering actuator based on the measured value T of the torque sensor of the feel simulator sensor The expected linear feedforward motor torque of the steering actuator is calculated through the linear feedforward control module, where the linear feedforward control module calculates the expected linear feedforward motor torque T of the steering actuator by designing a calibratable curve coefficient KL(x) according to the torque sensor signal T that changes in real time sensor as follows: T LFW is given by the following formula: T LFW = KL(x)T sensor ;

[0040] 2) Based on the driver's steering angle θ measured by the angle sensor of the feel simulator hwa , calculate the driver's steering speed and acceleration Meanwhile, considering the real-time motor torque of the steering actuator, calculate the expected feedforward motor torque T of the steering actuator through the dynamic feedforward control module FW , the dynamic feedforward control module calculates the expected feedforward motor torque T of the steering actuator by calculating the driver's steering speed and acceleration Based on the actual output torque T of the motor act calculate the expected feedforward motor torque T of the steering actuator FW : In the above formula, M rwa is the equivalent mass of the steering actuator, B rwa is the equivalent damping of the steering actuator, η is the transmission efficiency of the steering actuator, and G is the transmission ratio of the transmission mechanism of the steering actuator;

[0041] 3) Based on the angle deviation between the driver's steering angle θ hwa and the angle of the steering actuator θ rwa , calculate the expected feedback motor torque T of the steering actuator through the PID feedback control module FB , the PID feedback control module calculates the expected feedback motor torque T of the steering actuator by calculating the deviation (θ hwa -θ rwa ) between the driver's steering angle and the angle of the steering actuator, designing appropriate k p , k i , k d parameters, and calculating the expected feedback motor torque T of the steering actuator FB :

[0042] T FB = k p ×(θ hwa -θ rwa ) + k i ×(θ hwa -θ rwa ) + hd ×(θ hwa -θ rwa ));

[0043] 4) The finally expected steering actuator motor torque T sum is the sum of T LFW , T FW , and t FB , and is sent to the steering actuator motor for execution.

[0044] In summary, after adopting this system and control method, the driver drives the transmission mechanism of the feel simulator to rotate by applying a torque to the steering wheel, thereby generating an expected steering angle, and measuring and outputting it to the feel simulator controller through the feel simulator angle sensor; at the same time, the hand torque of the driver needs to overcome the resistance torque of the feel simulator motor, and is measured by the torque sensor and sent to the feel simulator controller, and the feel simulator motor is controlled to generate a torque through internal closed-loop torque control. At the same time, the steering actuator controller receives the driver's steering angle sent by the feel simulator controller, and compares and judges it with the steering actuator angle sensor, and controls the steering actuator motor to generate a torque to drive the steering actuator transmission mechanism to move to a position consistent with the driver's steering angle to drive the steering wheel to rotate. Therefore, based on the dynamic consistency between the angle of the steering actuator and the steering angle obtained by the feel simulator, the present invention realizes that the road surface actuator in the steer-by-wire system follows the feel simulator, so as to improve the response characteristics of the steering actuator in the steer-by-wire system to the driver's input angle, improve the response accuracy of the followability in the driver's dynamic input scenario, and improve the lateral control accuracy of the vehicle.

[0045] The above has made a detailed description of the present invention, aiming to enable those skilled in this field to understand the content of the present invention and implement it in real time. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A steer-by-wire system, which includes a haptic simulator and a steering actuator. The haptic simulator includes a torque sensor, a haptic simulator controller, a haptic simulator motor, a haptic simulator transmission mechanism, and a haptic simulator angle sensor; the steering actuator includes a steering actuator controller, a steering actuator angle sensor, a steering actuator transmission mechanism, and a steering actuator motor, characterized in that: The angle of the steering actuator is dynamically consistent with the steering angle obtained by the feel simulator, where the steering actuator motor torque T sum is T LFW , T FW , T FB and the sum of the three, T LFW is the expected linear feedforward motor torque of the steering actuator calculated according to the measured value T sensor of the feel simulator torque sensor and through a linear feedforward control module; T FW is the real-time steering actuator motor torque and the expected feedforward motor torque of the steering actuator calculated through a dynamic feedforward control module; T FB is the expected feedback motor torque of the steering actuator calculated according to the angle deviation between the driver's steering angle θ hwa and the steering actuator angle θ rwa and through a PID feedback control module.

2. The steer-by-wire system according to claim 1, wherein: The driver drives the transmission mechanism of the haptic simulator to rotate by applying a torque to the steering wheel, thereby generating a desired steering angle, and measuring and outputting it to the haptic simulator controller through the haptic simulator angle sensor; the hand torque of the driver needs to overcome the resistance torque of the haptic simulator motor and is measured by the torque sensor, and is simultaneously sent to the haptic simulator controller to control the haptic simulator motor to generate torque.

3. The steer-by-wire system according to claim 2, wherein: The haptic simulator controller, the haptic simulator motor, the haptic simulator transmission mechanism, and the haptic simulator angle sensor are connected in sequence to form an internal closed loop.

4. The steer-by-wire system according to claim 1, wherein: After receiving the driver's steering angle sent by the haptic simulator controller and comparing it with the steering actuator angle sensor, the steering actuator controller controls the steering actuator motor to generate a torque to drive the steering actuator transmission mechanism to move to a position consistent with the driver's steering angle to drive the steering wheel to rotate.

5. The steer-by-wire system according to claim 4, characterized in that: The steering actuator controller, the steering actuator motor, the steering actuator transmission mechanism, and the steering actuator angle sensor are connected in sequence to form an internal closed loop.

6. The steer-by-wire system according to claim 1, wherein: The linear feedforward control module calculates the expected linear feedforward motor torque T of the steering actuator according to the torque sensor signal T that changes in real time by designing a calibratable curve coefficient KL(x). sensor , as follows: LFW The formula is as follows: T LFW = KL(x) × T sensor .

7. The steer-by-wire system according to claim 1, wherein: Steering actuator desired feedforward motor torque T FW At the same time, according to the driver's steering angle θ measured by the feel simulator angle sensor hwa , and calculate the driver's steering speed and acceleration 8. The steer-by-wire system according to claim 7, characterized in that: The dynamic feedforward control module calculates the driver's steering speed and acceleration According to the actual output torque T of the motor act Calculate the desired feedforward motor torque T of the steering actuator FW : In the above formula, M rwa is the equivalent mass of the steering actuator, B rwa is the equivalent damping of the steering actuator, η is the transmission efficiency of the steering actuator, and G is the transmission ratio of the transmission mechanism of the steering actuator.

9. The steer-by-wire system according to claim 7, characterized in that: The PID feedback control module calculates the deviation (θ hwa - θ rwa ) between the driver's steering angle and the steering actuator angle, designs appropriate k p , k i , k d parameters, and calculates the expected feedback motor torque T FB of the steering actuator as follows: T FB = k p ×(θ hwa - θ rwa ) + k i ×(θ hwa - θ rwa ) + k d ×(θ hwa - θ rwa )。 10. An angle control method for a steer-by-wire system, characterized in that: This method adopts the steer-by-wire system described in any one of claims 1 to 9, and the control process for the dynamic consistency between the haptic simulator angle and the steering actuator angle is as follows: 1) According to the measured value T of the torque sensor of the feel simulator sensor The desired linear feedforward motor torque of the steering actuator is calculated through the linear feedforward control module, where the linear feedforward control module calculates the desired linear feedforward motor torque T of the steering actuator by designing a calibratable curve coefficient KL(x) according to the torque sensor signal T that changes in real time sensor LFW As follows: T LFW = KL(x) × T sensor ;​ 2) According to the driver's steering angle θ measured by the feel simulator angle sensor hwa , and calculate the driver's steering speed and acceleration Meanwhile, considering the real-time steering actuator motor torque, the desired feedforward motor torque T of the steering actuator is calculated through the dynamic feedforward control module FW , the dynamic feedforward control module calculates the driver's steering speed and acceleration According to the actual output torque T of the motor act calculate the desired feedforward motor torque T of the steering actuator FW : In the above formula, M rwa is the equivalent mass of the steering actuator, B rwa is the equivalent damping of the steering actuator, η is the transmission efficiency of the steering actuator, and G is the transmission ratio of the steering actuator transmission mechanism; 3) According to the driver's steering angle θ hwa and the steering actuator angle θ rwa angle deviation, the desired feedback motor torque T of the steering actuator is calculated through the PID feedback control module FB , the PID feedback control module calculates the deviation between the driver's steering angle and the steering actuator angle (θ hw a - θ rwa ), designs appropriate k p , k i , k d parameters, and calculates the desired feedback motor torque T of the steering actuator FB : T FB = k p ×(θ hwa - θ rwa ) + k i ×(θ hwa - θ rwa ) + k d ×(θ hwa - θ rwa ); 4) The final desired steering actuator motor torque T sum is T LFW , T FW , T FB the sum of the three, and sent to the steering actuator motor for execution.

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