Method for steering wheel and front wheel corner coupling alignment of steering-by-wire system

Abstract

The invention relates to the technical field of steering systems, in particular to a steering wheel and front wheel corner coupling alignment method for a steer-by-wire system. A method for steering wheel and front wheel corner coupling alignment of a steer-by-wire system includes a steering wheel alignment state machine. Compared with the prior art, the steering wheel and front wheel steering angle coupling alignment method for the steer-by-wire system can solve the problem of how to align and couple again after up-down decoupling of steer-by-wire; according to the method, power-on automatic operation is achieved, manual key activation is not needed, and the flexibility and comfort of the alignment function are improved; after the steering wheels are aligned, abnormal sound generated by large fluctuation of downward torque can be avoided during upper and lower steering coupling.

Description

Technical Field

[0001] The invention relates to the technical field of steering systems, in particular to a method for coupling and aligning a steering wheel and a front wheel angle in a wire-controlled steering system. Background Art

[0002] With the popularization of new energy vehicles and the rapid development of intelligent driving technology, the diversification and intelligence of automobile use needs have become an inevitable trend in the future development of automobiles. As a key system for intelligent driving, the steering system will also evolve from traditional mechanical steering, hydraulic steering, and electric power steering to wire-controlled steering to adapt to higher levels of autonomous driving and future intelligent transportation scenarios.

[0003] Steering by Wire eliminates the mechanical intermediate shaft connecting the upper and lower parts of the traditional electric power steering system. Instead, it controls the steering actuator motor through electronic control signals, which drives the front wheels to complete the steering, thus achieving mechanical decoupling of the steering wheel and the steering front wheels of the car.

[0004] After the steer-by-wire system is freed from the mechanical intermediate shaft, the steering wheel mechanism and the front wheel drive mechanism will be divided into two independent control systems, each controlled by its own controller, which can achieve software decoupling and software coupling effects between the steering wheel mechanism and the front wheel angle mechanism. When the upper and lower steering systems are decoupled, steer-by-wire can achieve more functions than traditional steering, such as game mode, steering wheel silent mode, etc. When the steering wheel and front wheel angle are coupled, steer-by-wire can achieve a normal steering driving experience like traditional steering. Between the decoupling and coupling of the upper and lower steering, a steering wheel alignment method is needed to achieve coupling. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system, so that the steer-by-wire system can complete the up and down coupling action faster and more comfortably.

[0006] To achieve the above purpose, a method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system is designed, including a steering wheel alignment state machine, characterized in that the method flow is as follows: S1, the steering wheel alignment state machine determines whether the vehicle has been unlocked. If yes, it enters the steering wheel alignment angle closing control mode, and the central control screen prompts the steering wheel to enter the alignment mode; otherwise, it waits for the opening conditions to be met; S2, the steering wheel alignment initialization state determines whether to enter the steering wheel alignment execution state according to the conditions; when the conditions are met, the steering wheel alignment mode is executed; S3, if the current angle difference between the steering wheel and the front wheel steering angle is less than or equal to 1°, skip step S2, the steering wheel alignment execution state, and directly enter the steering wheel alignment completion state; S4: If the steering wheel torque is greater than 3Nm during the steering wheel alignment, the steering wheel alignment is interrupted and the system enters the steering wheel alignment interruption state. The central control screen prompts that the steering wheel alignment is interrupted and enters the steering wheel vibration output control mode. The steering wheel vibrates to remind the driver to release the steering wheel. When the steering wheel torque is below 3Nm, the steering wheel alignment mode is re-executed. S5: If the steering wheel alignment process is interrupted more than 3 times, the system will exit the steering wheel alignment mode and prompt the central control screen to exit the steering wheel alignment mode; S6, after the steering wheel alignment fails, the vehicle needs to be powered on and off again, and step S1 steering wheel alignment mode is executed again; S7: After the steering wheel alignment is completed, if it is detected that the vehicle mode is in game mode or the steering wheel silent mode is turned on, it jumps to the steering wheel alignment start state.

[0007] The wire-controlled steering system includes a steering wheel, a TAS sensor, a steering column, a feel simulation motor, a SAS, a steering execution motor, an upper steering controller, a lower steering controller, a central control screen and vehicle communication. The SAS is a steering angle sensor, and the TAS sensor is an angle torque sensor; the upper and lower steering controllers communicate with the vehicle through a public CAN bus, and the driver controls the switches of several modes through the central control screen; the upper and lower steering controllers transmit their respective angle signals and mode signals through a private CAN, and independently control the torque output of the feel simulation motor and the steering execution motor to realize several wire-controlled driving modes.

[0008] In the step S1, it is determined whether the vehicle has been unlocked and is powered on for the first time in this power-on cycle, or whether the decoupling mode has been exited.

[0009] In step S1, the process of steering wheel alignment angle closing control is as follows: S11, subtract the current steering wheel angle from the lower steering angle, and use the angle difference curve to obtain the target angular velocity; S12, performing PID control on the target angular velocity and the current angular velocity difference to obtain the target steering wheel alignment motor request torque.

[0010] The steering wheel alignment angle closure control module has two sets of configuration parameters corresponding to two alignment scenarios: (1) Quick alignment: When the vehicle is unlocked using the Bluetooth key, the vehicle detects that the driver is not sitting in the seat and selects the quick alignment parameters to ensure that the steering wheel is aligned before the driver enters the vehicle. (2) Slow alignment: When the game mode or steering wheel silent mode is exited, the vehicle detects that the driver is in the seat and selects the slow alignment parameters. The purpose is to align the steering wheel smoothly without scaring the driver, thereby enhancing the sense of luxury of the vehicle.

[0011] In step S2, the judgment conditions for the alignment initialization state are: (1) the difference between the steering wheel angle and the front wheel angle is greater than 1°; (2) whether the current steering wheel torque is less than 2Nm; (3) whether the current steering wheel speed is less than 50° / s; if all three conditions are met, the steering wheel alignment is performed.

[0012] In step S4, the steering wheel vibration output control is to use the cosine function to calculate the motor torque M=Acos(ωt+φ)=Acos(2πft+φ)=Acos(360ft+φ), where A is the amplitude of the motor output torque, f is the vibration frequency, t is the running time, and φ is the initial phase angle.

[0013] Compared with the prior art, the present invention provides a method for coupling and aligning the steering wheel and front wheel angle of a wire-controlled steering system, which can solve the problem of how to realign the coupling after the wire-controlled steering is decoupled up and down; the method runs automatically when powered on and does not require manual button activation, thereby improving the flexibility and comfort of the alignment function; and after the steering wheel is aligned, the abnormal noise caused by large fluctuations in the downward turning torque can be avoided when the upward and downward steering are coupled. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a connection diagram for the wire control system.

[0015] Figure 2 Schematic diagram of the flow chart of the steering wheel up and down coupling alignment control strategy.

[0016] Figure 3 This is a flow chart of the steering wheel alignment state machine.

[0017] Figure 4 Flowchart of the steering wheel alignment control strategy.

[0018] Figure 5 This is the angle difference single-loop PID control flow chart.

[0019] Figure 6 This is the flow chart of vibration output control.

[0020] Figure 7 It is a curve diagram of the relationship between the angle difference and the target angular velocity. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] After the steering wheel mechanism and the front wheel drive mechanism of the steer-by-wire system are decoupled, the steering wheel mechanism and the front wheel drive mechanism are controlled by their respective controllers. When the driver enters the driving mode, the up and down steering angles need to be aligned so that the angles of the up and down steering angle sensors are consistent in order to complete the system coupling. There are two typical application scenarios: 1. Unlock and start the vehicle: When the vehicle is unlocked via the Bluetooth key, the steering wheel will be aligned up and down to ensure that the steering wheel angle and the front wheel angle are consistent when the driver gets on the vehicle. This is because the steering wheel may be tilted when the driver gets off the vehicle after parking.

[0023] 2. Exit decoupling mode: When the game mode or steering wheel silent mode is exited, the steering wheel angle and the front wheel angle are likely to be misaligned. You need to run the steering wheel up and down coupling alignment again.

[0024] The hardware of the wire-controlled steering system mainly includes: steering wheel, TAS sensor (angle torque sensor), steering column, feel simulation motor, SAS (angle sensor), steering execution motor, upper steering controller, lower steering controller, central control screen and vehicle communication. The upper and lower steering controllers communicate with the vehicle through the public CAN bus, and the driver controls each mode switch through the central control screen. The upper and lower steering controllers transmit their respective angle signals and mode signals through the private CAN, and independently control the torque output of the feel simulation motor and the steering execution motor to achieve different wire-controlled driving modes.

[0025] Therefore, the present invention provides a method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system, such as Figure 1 , Figure 2 As shown, the process of this method is as follows: 1. The steering wheel alignment state machine first determines whether the vehicle has been unlocked, that is, whether it is powered on for the first time in this power-on cycle, or whether the decoupling mode (game mode, steering wheel silent, etc.) has been exited. This signal is sent by the driver through the central control screen or voice control system, and is sent to the steering system through vehicle communication. The steering system determines whether to enter the steering wheel alignment initialization state based on the current conditions (such as whether the vehicle speed signal meets the switching conditions). At the same time, the central control screen will prompt the steering wheel to enter the steering wheel alignment mode. Do not hold the steering wheel with your hands.

[0026] 2. Steering wheel alignment initialization state determines whether to enter the steering wheel alignment execution state based on the conditions, mainly: (1) the difference between the steering wheel angle and the front wheel angle is greater than 1° (the limit can be changed according to needs); (2) whether the current steering wheel torque is less than 2Nm (the limit can be changed according to needs); (3) whether the current steering wheel speed is less than 50° / s (the limit can be changed according to needs). If the above three conditions are met, the steering wheel alignment mode is executed. If the angle difference between the current steering wheel and the front wheel angle is less than or equal to 1°, the steering wheel alignment execution state is skipped and the steering wheel alignment completion state is directly entered.

[0027] 3. If the steering wheel torque is greater than 3Nm during the steering wheel alignment, the steering wheel alignment will be interrupted and the system will enter the steering wheel alignment interruption state. The central control screen will prompt that the steering wheel alignment is interrupted and the steering wheel will vibrate to remind the driver to release the steering wheel. When the steering wheel torque is below 3Nm, the steering wheel alignment mode will be re-executed.

[0028] 4. If the steering wheel alignment process is interrupted more than 3 times, the system will exit the steering wheel alignment mode and prompt the central control screen to exit the steering wheel alignment mode. If the steering wheel alignment fails, the vehicle needs to be powered on and off again and the steering wheel alignment mode needs to be executed again.

[0029] 5. In the steering wheel alignment completion state, if it is detected that the vehicle mode is turned on the game mode or the steering wheel silent mode, the state will jump to the steering wheel alignment start state.

[0030] The status signal of the steering wheel alignment state machine will be sent to the central control panel through the vehicle communication, and the current status will be displayed synchronously. It will also be used as one of the conditions for the vehicle mode switching. Only when the alignment is completed, the vehicle can enter the driving mode, and the steering execution motor can perform steering according to the current angle of the steering wheel.

[0031] Actual case: (1) When the steering wheel is aligned, the driver can feel that the direction of the vehicle's movement is consistent with the steering direction of the steering wheel, which is in line with normal driving habits.

[0032] (2) When the steering wheel fails to align, for example, there is a 100° angle difference between the steering wheel and the front wheel. At this time, if the driver still keeps the steering wheel in the middle position according to driving habits, hoping to drive in a straight line, the vehicle will deviate to one side due to the angle difference between the steering wheel and the front wheel. The vehicle's running direction is inconsistent with the driver's subjective intention, which will cause the driver to panic and greatly increase the probability of traffic accidents.

[0033] When the state machine is in the alignment execution state, the angle difference single-loop PID is used for control. When the state machine is in the alignment interruption state, the vibration output is used for control.

[0034] 1. The angle difference single-loop PID control process is as follows: (1) Subtract the current steering wheel angle from the lower steering angle and use the angle difference curve to obtain the target angular velocity; (2) The target angular velocity and the current angular velocity difference are subjected to PID control to obtain the target steering wheel alignment motor request torque.

[0035] There are two sets of configuration parameters under this control logic, corresponding to the alignment scenarios mentioned above: (1) Quick alignment: When the vehicle is unlocked using the Bluetooth key, the vehicle detects that the driver is not sitting in the seat and selects the quick alignment parameters to ensure that the steering wheel is aligned before the driver enters the vehicle.

[0036] (2) Slow alignment: When the game mode or the steering wheel is silently exited, the vehicle detects that the driver is in the seat and selects the slow alignment parameters. The purpose is to smoothly align the steering wheel without scaring the driver and to enhance the sense of luxury of the vehicle.

[0037] 2. Vibration output control is constructed using the cosine function: the motor torque M=Acos(ωt+φ)=Acos(2πft+φ)=Acos(360ft+φ), where A is the amplitude of the motor output torque, f is the vibration frequency, t is the operating time, and φ is the initial phase angle.

[0038] In the vibration output control algorithm, the operating logic is: after the steering wheel alignment is completed, the system can enter the driving mode, and the central control screen will prompt the driver to take over the vehicle. When entering the human driving mode, the lower steering system will judge the steering wheel alignment state machine to enter the driving mode from the alignment mode. The lower turn angle loop control will add a torque slow increase strategy, that is, the angle loop torque increase gradient limit in this state is within a certain gradient. This is to prevent the lower turn angle control from having a small angle difference when just entering the driving mode, and a large instantaneous force will appear in the control, resulting in some abnormal noises. When the lower turn angle responds to the upper turn angle, the system enters the human driving mode and the steering wheel alignment coupling is completed.

[0039] The present invention can solve the problem of how to realign the coupling after the up and down decoupling of the wire-controlled steering; the steering wheel alignment method runs automatically when powered on, and does not require manual button activation, thereby improving the flexibility and comfort of the alignment function; after the steering wheel alignment is completed, the abnormal noise caused by large fluctuations in the downward turning torque can be avoided when the up and down steering are coupled.

Claims

1. A method for coupling and aligning a steering wheel and a front wheel angle in a steer-by-wire system, comprising a steering wheel alignment state machine, characterized in that: The described method flow is as follows: S1, the steering wheel alignment state machine determines whether the vehicle has been unlocked. If yes, it enters the steering wheel alignment angle closing control mode, and the central control screen prompts the steering wheel to enter the alignment mode; otherwise, it waits for the opening conditions to be met; S2, the steering wheel alignment initialization state determines whether to enter the steering wheel alignment execution state according to the conditions; when the conditions are met, the steering wheel alignment mode is executed; S3, if the current angle difference between the steering wheel and the front wheel steering angle is less than or equal to 1°, skip step S2, the steering wheel alignment execution state, and directly enter the steering wheel alignment completion state; S4: If the steering wheel torque is greater than 3Nm during the steering wheel alignment, the steering wheel alignment is interrupted and the system enters the steering wheel alignment interruption state. The central control screen prompts that the steering wheel alignment is interrupted and enters the steering wheel vibration output control mode. The steering wheel vibrates to remind the driver to release the steering wheel. When the steering wheel torque is below 3Nm, the steering wheel alignment mode is re-executed. S5: If the steering wheel alignment process is interrupted more than 3 times, the system will exit the steering wheel alignment mode and prompt the central control screen to exit the steering wheel alignment mode; S6, after the steering wheel alignment fails, the vehicle needs to be powered on and off again, and step S1 steering wheel alignment mode is executed again; S7: After the steering wheel alignment is completed, if it is detected that the vehicle mode is in game mode or the steering wheel silent mode is turned on, it jumps to the steering wheel alignment start state.

2. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: The wire-controlled steering system includes a steering wheel, a TAS sensor, a steering column, a feel simulation motor, a SAS, a steering execution motor, an upper steering controller, a lower steering controller, a central control screen and vehicle communication. The SAS is a steering angle sensor, and the TAS sensor is an angle torque sensor; the upper and lower steering controllers communicate with the vehicle through a public CAN bus, and the driver controls the switches of several modes through the central control screen; the upper and lower steering controllers transmit their respective angle signals and mode signals through a private CAN, and independently control the torque output of the feel simulation motor and the steering execution motor to realize several wire-controlled driving modes.

3. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: In the step S1, it is determined whether the vehicle has been unlocked and is powered on for the first time in this power-on cycle, or whether the decoupling mode has been exited.

4. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: In step S1, the process of steering wheel alignment angle closing control is as follows: S11, subtract the current steering wheel angle from the lower steering angle, and use the angle difference curve to obtain the target angular velocity; S12, performing PID control on the target angular velocity and the current angular velocity difference to obtain the target steering wheel alignment motor request torque.

5. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: The steering wheel alignment angle closure control module has two sets of configuration parameters corresponding to two alignment scenarios: (1) Quick alignment: When the vehicle is unlocked using the Bluetooth key, the vehicle detects that the driver is not sitting in the seat and selects the quick alignment parameters to ensure that the steering wheel is aligned before the driver enters the vehicle. (2) Slow alignment: When the game mode or steering wheel silent mode is exited, the vehicle detects that the driver is in the seat and selects the slow alignment parameters. The purpose is to align the steering wheel smoothly without scaring the driver, thereby enhancing the sense of luxury of the vehicle.

6. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: In step S2, the conditions for determining the alignment initialization state are: (1) the difference between the steering wheel angle and the front wheel steering angle is greater than 1°; (2) whether the current steering wheel torque is less than 2 Nm; (3) whether the current steering wheel speed is less than 50° / s; All three conditions are met to perform steering wheel alignment.

7. The method for coupling and aligning the steering wheel and front wheel angles of a steer-by-wire system according to claim 1, characterized in that: In step S4, the steering wheel vibration output control is to use the cosine function to calculate the motor torque M=Acos(ωt+φ)=Acos(2πft+φ)=Acos(360ft+φ), where A is the amplitude of the motor output torque, f is the vibration frequency, t is the running time, and φ is the initial phase angle.

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