Vehicle active return-to-center control method for EPS speed closed-loop control
By combining EPS speed closed-loop control and state machine judgment with PI control and field-oriented control, a smooth adaptive return-to-center process for the vehicle is achieved, overcoming the shortcomings of traditional EPS return-to-center control and improving driving comfort and safety.
Patent Information
- Application Number
- CN202511954041.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-02-24
AI Technical Summary
Traditional EPS return control methods have shortcomings in terms of vehicle speed adaptability, control precision, and smoothness of the return process, resulting in unstable return performance and affecting driving comfort and safety.
The EPS speed closed-loop control method is adopted, which combines the signal processing of steering wheel torque, angle and angular velocity. The state machine determines the return-to-center state, and the PI controller and adaptive attenuation factor are used to generate a smooth return-to-center torque command. Combined with field-oriented control and zero-sequence component injection space vector pulse width modulation technology, real-time closed-loop control of the return-to-center process is realized.
It improves the reliability and smoothness of the return-to-center control, ensuring fast and powerful return-to-center at low speeds and smooth return-to-center at high speeds, reducing vehicle yaw and steering wheel oscillation, enhancing driving comfort and safety, expanding the motor speed range, and reducing the computational burden on the microcontroller.
Smart Images
Figure CN121553244A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of automotive electric power steering technology, specifically relating to a vehicle active return-to-center control method with EPS speed closed-loop control. Background Technology
[0002] The self-centering performance of a vehicle's steering system is one of the key indicators for measuring a car's handling stability and driving experience. Good self-centering performance allows the steering wheel to automatically, smoothly, and accurately return to the center position for straight-line driving after a turn, reducing the driver's handling burden and enhancing the vehicle's straight-line stability.
[0003] In traditional mechanical steering systems, the automatic return of the steering wheel to center primarily relies on the return torque generated by front wheel alignment parameters (such as caster angle and kingpin inclination angle). However, this purely mechanical return-to-center method has inherent limitations: the return torque varies significantly with vehicle speed, steering angle, and road conditions, leading to unstable return-to-center performance. Especially at low speeds, the return torque is small, easily resulting in slow or incomplete steering wheel return; while at high speeds, although the return torque is large, excessive oscillation may occur due to the rapid return speed, affecting driving smoothness and safety.
[0004] With the widespread application of EPS (Electric Power Steering), a hardware foundation has been provided for optimizing EPS return-to-center performance. Current mainstream return-to-center control employs an open-loop control method, where a fixed return-to-center torque is applied at different angles. When the driver intervenes, the return-to-center torque is attenuated according to a torque reduction coefficient. This method significantly improves the vehicle's return-to-center performance, but it also presents several key challenges:
[0005] I. Limitations of Hand Torque Threshold Setting: The hand torque threshold is usually set as a fixed value or a simple mapping relationship. Under complex operating conditions, such as on bumpy roads, the steering wheel will be subjected to continuous impacts from the road surface, causing the hand torque sensor signal to fluctuate violently. At this time, the system may be unable to accurately determine whether the driver has "let go" and thus falsely trigger or fail to trigger the return-to-center function, affecting the accuracy and reliability of control.
[0006] Second, insufficient adaptability to vehicle speed: Vehicles have different requirements for the self-centering process at different speeds. At low speeds, drivers expect a quick and powerful self-centering; at high speeds, a smooth and gentle self-centering is needed to avoid vehicle yaw and steering wheel vibration. Although traditional self-centering control strategies incorporate vehicle speed as a reference, they are mostly open-loop lookup table methods, failing to make real-time closed-loop adjustments based on the actual dynamic performance during the self-centering process, making it difficult to achieve optimal self-centering quality across the entire speed range.
[0007] 3. Poor smoothness of the return-to-center process: Due to the lack of direct closed-loop control over the return-to-center speed, traditional return-to-center torque control may result in a non-linear return-to-center process. Initially, the force may be insufficient, then suddenly accelerate in the middle stage, and finally oscillate back and forth around the center position. This "stuck" or "overshoot" phenomenon severely reduces driving comfort.
[0008] Therefore, a vehicle active return-to-center control method is needed that can accurately determine the return-to-center state and adaptively and smoothly adjust the return-to-center process according to the vehicle speed to solve the above-mentioned technical problems. Summary of the Invention
[0009] This invention aims to combine the advantages of strong anti-load disturbance capability of speed closed-loop control with accurate judgment of the homing state, and overcome the defects of traditional open-loop homing control methods, such as large residual angle, unstable homing process, and inaccurate identification of homing state.
[0010] This invention provides the following technical solution: a vehicle active return-to-center control method for EPS speed closed-loop control, comprising the following steps: Step 1, Signal Acquisition and Processing: Acquire the torque and angle signals of the steering wheel, filter them, and then calculate the actual angle, actual torque, and actual angular velocity of the steering wheel.
[0011] Step 2, Target Generation: Based on the current vehicle speed, query the pre-calibrated S-curve-shaped return target curve and generate a target return angular velocity that changes continuously and smoothly over time.
[0012] Step 3, State Judgment: Based on the actual angle, actual angular velocity and actual torque values and their changing trends obtained in Step 1, the current return-to-center state of the vehicle is determined by the state machine logic.
[0013] Step 4, Torque Calculation: The target angular velocity obtained in Step 2 is compared with the actual angular velocity obtained in Step 1 to obtain the angular velocity error. The PI controller is used to calculate the angular velocity error to generate the basic angular velocity torque. The output of the PI controller includes proportional control output and integral control output.
[0014] Step 5, Adaptive Attenuation: Based on the current vehicle return-to-center status determined in Step 3, dynamically select and output the corresponding proportional attenuation factor and integral attenuation factor; selectively attenuate the proportional control output and / or integral control output, and perform amplitude limiting processing on the attenuated result to obtain the final safe return-to-center torque command.
[0015] Step 6, Torque Execution: The final safe return torque command obtained in Step 5 is used as the torque setpoint and input to the motor drive system based on field-oriented control to drive the assist motor to generate the corresponding return torque.
[0016] Preferably, in step 3, the vehicle's current return-to-center state includes: Steering wheel free return to center: The system takes the lead in the return-to-center process without driver intervention.
[0017] Reverse steering state during the return-to-center process: The driver applies torque in the opposite direction to the return-to-center direction.
[0018] During the return-to-center process, when the steering wheel is turned in the same direction: the driver applies torque in the same direction as the return-to-center process to accelerate the return to center.
[0019] Steering wheel hold mode: The driver applies torque to keep the steering wheel in a non-neutral position.
[0020] Steering wheel stationary state: The steering wheel is in the near-neutral position and the driver does not intervene.
[0021] Preferably, in step 5, the judgment rules for dynamically selecting and outputting the corresponding proportional attenuation factor and integral attenuation factor include: When the steering wheel is determined to be in a free return-to-center state, both the proportional attenuation factor and the integral attenuation factor are set to 1 to maintain the full output of the basic return-to-center torque.
[0022] When the steering wheel is determined to be in a steering hold state, the proportional attenuation factor is set to a fixed value or a dynamically calculated value less than 1, while the integral attenuation factor is kept at 1, so that the final safe return torque command mainly comes from the integral control output, in order to provide a continuous and gentle return force.
[0023] When the system is determined to be in a state of turning the steering wheel in the opposite direction during the return-to-center process, in a state of turning the steering wheel in the same direction during the return-to-center process, or in a state where the steering wheel is stationary, both the proportional attenuation factor and the integral attenuation factor are set to values less than 1. At the same time, the proportional and integral control outputs are attenuated to ensure that the driver's steering operation is easy.
[0024] More preferably, in step 5, the method for attenuating the integral control output includes: feeding forward the product of the integral attenuation factor and the integral control output to the speed error input of the PI controller, so as to achieve a slow and smooth attenuation of the integral quantity and avoid sudden torque changes.
[0025] Preferably, in step 2, the mathematical expression of the S-curve-shaped return target curve includes a piecewise continuous function or a smooth approximation function of a piecewise continuous function. The curve shape parameters include at least: the maximum return angular velocity, the total time of the return process, and the curve smoothing coefficient. The curve shape parameters are independently calibrated according to the vehicle speed to achieve rapid and powerful return at low speeds and smooth and stable return at high speeds.
[0026] Preferably, in step 1, a first-order inertial low-pass filter algorithm is used to filter the angle and torque signals, and the discretization formula is: Where x(n) is the current sampled value, y(n) and y(n-1) are the current and previous filtered output values, and λ is the filter coefficient.
[0027] The actual angular velocity is obtained by calculating the difference in steering wheel angle between adjacent cycles: Where Ts is the sampling period, , The steering wheel angles at time n and time n-1 are respectively.
[0028] Preferably, in step 6, the magnetic field orientation control system employs a space vector pulse width modulation method based on zero-sequence component injection, specifically including: The basic values of the three-phase voltages are calculated from the d-axis voltage Ud and the q-axis voltage Uq using the inverse Park transform and inverse Clark transform; the zero-sequence component is: Where Ia, Ib, and Ic are the three-phase currents of the motor collected by the MCU.
[0029] The zero-sequence component is added to the three-phase voltage base value to obtain the modulation wave signal; the modulation wave signal is compared with the triangular carrier wave to generate the PWM switching signal to drive the three-phase inverter.
[0030] Even better, in the space vector pulse width modulation method based on zero-sequence component injection, the injected zero-sequence component is equivalent to the modulation effect of traditional seven-segment SVPWM, but avoids complex sector judgment, thereby reducing the occupation of microcontroller computing resources.
[0031] Preferably, in step 6, the field-oriented control system includes a field-weakening control unit. The field-weakening control unit dynamically adjusts the d-axis current setpoint and q-axis current setpoint based on the motor speed and DC bus voltage. The control strategy of the field-weakening control unit is as follows: In the constant torque region below the base speed, a control strategy with Id=0 is adopted; in the constant power region above the base speed, a field weakening control strategy that gradually increases negative Id is adopted to expand the speed range; in the deep field weakening region, a maximum torque-voltage ratio control strategy is adopted, and the d-axis current is distributed at the intersection of the voltage limit circle and the current limit circle.
[0032] Preferably, the control method controls a vehicle electric power steering system, the vehicle electric power steering system comprising: A torque angle sensor is used to detect the torque and angle of the steering wheel in real time; a vehicle speed sensor is used to provide the current vehicle speed signal; an electronic control unit is used to implement the control method; the electronic control unit includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the control method is implemented; a power steering motor is used to provide steering assistance and return torque according to instructions.
[0033] The beneficial effects of this invention are: 1. This invention significantly improves the performance and reliability of vehicle active self-centering control by introducing a speed closed-loop control mechanism combined with precise judgment of the self-centering state. Specifically, this invention can adaptively adjust the self-centering process according to vehicle speed, ensuring rapid and powerful self-centering at low speeds, while maintaining smooth and gentle self-centering at high speeds, effectively avoiding vehicle yaw and steering wheel oscillation, thereby improving driving comfort and safety.
[0034] 2. By meticulously classifying and accurately judging the alignment state, the system can dynamically select and output the corresponding proportional attenuation factor and integral attenuation factor to selectively attenuate the basic alignment torque, ensuring the smoothness and linearity of the alignment process and avoiding the "stuck" or "overshoot" phenomena that may occur in traditional control methods.
[0035] 3. The field-oriented control system of this invention employs a space vector pulse width modulation method based on zero-sequence component injection, which not only reduces the computational resource requirements of the microcontroller but also improves the system's response speed and stability. The introduction of the field weakening control unit further expands the motor's speed range, enabling the system to achieve optimal homing quality across the entire speed domain. Attached Figure Description
[0036] Figure 1 This is a classification analysis diagram of the vehicle active return-to-center control method for EPS speed closed-loop control according to the present invention, regarding the return-to-center state; Figure 2 This is an overall block diagram of the present invention; Figure 3 This is a schematic diagram of the curved return curve of the present invention; Figure 4 This is a block diagram illustrating an embodiment of the present invention regarding speed closed-loop homing; Figure 5 This is the FOC control block diagram of the present invention regarding zero-sequence component injection SVPWM; Figure 6 This is a measured diagram of the alignment process in an embodiment of the present invention. Detailed Implementation
[0037] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0038] like Figures 1-6 As shown, the active self-centering control method in this embodiment uses an S-curve-shaped self-centering curve to ensure smooth changes in self-centering speed. Instead of solely using steering wheel torque to determine the self-centering state, it combines steering wheel angle, steering wheel speed, and steering wheel torque to jointly determine whether to attenuate the self-centering portion and the amount of attenuation. The self-centering process attenuation uses an integral output feedback-based attenuation method to ensure that the driver's self-centering needs are met under different self-centering states. The main loop control method uses a speed closed-loop approach instead of the traditional open-loop control method to improve the loop's anti-disturbance capability. In the FOC control loop, the SVPWM modulation method uses a zero-sequence component injection method instead of the traditional sector method, reducing the MCU's computational burden and improving the algorithm's execution efficiency.
[0039] In this embodiment, the return-to-center conditions are systematically classified as follows: including steering wheel free return to center, steering wheel turning in the opposite direction during return to center, steering wheel turning in the same direction during return to center, steering wheel holding the rudder, and steering wheel remaining stationary (driver does not move).
[0040] In this embodiment, if it is determined that the current state is in a steering hold state, only the integral control unit is attenuated to ensure that there is still a return force when steering hold is in effect; if it is determined that the current state is in a free return state, no attenuation is performed and the steering wheel returns to center at a predetermined speed. In other states, both the proportional control unit and the integral control unit are attenuated simultaneously to ensure the ease of steering for the driver.
[0041] In this embodiment, the main circuit adopts a speed closed-loop control method, which can achieve controllable and stable rotation speed throughout the entire return process while ensuring controllable speed.
[0042] In this embodiment, the use of SVPWM with zero-sequence component injection in FOC control instead of SVPWM with sector method reduces the overall computational load of FOC control.
[0043] This embodiment of the vehicle active return-to-center control method for EPS speed closed-loop control includes: The EPS controller should acquire the PWM signal from the TAS (steering wheel torque angle sensor) and calculate the actual angle and torque using an algorithm.
[0044] The collected steering wheel angle and torque are filtered, and the angular velocity of the steering wheel is calculated. A low-pass filter can be used for this filtering. The steering wheel rotation speed can be calculated as follows: This allows for the acquisition of relatively smooth angle, torque, and angular velocity signals.
[0045] The given curve for normalization is as follows: Figure 3 As shown, the required speed for centering varies at different vehicle speeds. This invention employs a curved centering curve based on vehicle speed variations. This curve ensures continuous and stable speed changes during centering, and the centering curves at different vehicle speeds can be calibrated. The algorithm is as follows: like Figure 1 As shown, this embodiment classifies the return-to-center state in detail. From the driver's intention, the return-to-center state can be divided into five states: steering wheel freely returning to center, steering wheel turning in the opposite direction during the return-to-center process, steering wheel turning in the same direction during the return-to-center process, steering wheel holding the rudder, and steering wheel stationary (driver does not move). These five return-to-center states determine the attenuation of the return-to-center torque to adapt to all the driver's intentions for steering return-to-center. like Figure 4 As shown, in this embodiment, the speed loop main body homing adopts a speed loop closed-loop control based on PI control, and its basic algorithm is as follows: That is, the current speed error is obtained by subtracting the target speed output by the return curve unit from the current actual steering wheel speed. This error is divided into two paths: one path is multiplied by the proportional unit Kp to obtain the proportional output part, and the other path accumulates the current error and multiplies it by the integral coefficient Ki to obtain the integral output part, and the integral output is limited. The two are added together to obtain the final output torque.
[0046] Regarding the attenuation processing of the PI controller: The current return-to-center state is determined based on the filtered steering wheel speed, steering wheel angle, and steering wheel torque. If the state is determined to be a steering hold state, only the proportional control portion is attenuated. Specifically, the proportional attenuation decision unit outputs a proportional attenuation factor, which is multiplied by the proportional unit's output to obtain the final proportional control torque. The integral attenuation factor remains constant at 1, maintaining the integral output torque. This approach provides a smaller return-to-center force to the steering wheel during steering hold, allowing for a quick response to the driver's intention to return to center when the steering wheel is slowly released. When the state is determined to be a free return-to-center state, both the proportional and integral attenuation factors are 1, maintaining the proportional and integral outputs to ensure a smooth and normal return of the steering wheel to center. When any other return-to-center state is detected, both the proportional and integral attenuation decision units output attenuation factors simultaneously for attenuation.
[0047] Furthermore, the method for integral attenuation is to multiply the integral attenuation factor output by the integral attenuation decision unit by the integral output, feed forward and add the result to the error input to achieve attenuation of the integral module. The advantage of this attenuation is that the integral attenuation is slow and gradual, so as not to give the driver a sudden feeling.
[0048] Furthermore, the final output torque needs to be limited before being output to the FOC to ensure that the return torque is not too large.
[0049] like Figure 5 As shown: After the homing torque is given to the FOC control, the actual Id and Iq are obtained by first passing through the field weakening control unit. The field weakening control unit is described as using MTPA control with id=0 in the constant torque region, increasing the field weakening angle according to the constant power field weakening algorithm in the constant power region, and distributing the dq axis current according to MTPV in the deep field weakening region. The MCU collects the three-phase currents Ia, Ib, and Ic of the motor, and uses Clark and Park transformations to obtain the feedback values of id and iq. The algorithm is as follows: The current error is obtained by subtracting the collected id and iq from the given id and iq. This error is then used to obtain ud and uq via a PI controller. ud and uq are then used to obtain UA, UB, and UC through inverse Park and inverse Clark transformations, as shown in the following algorithm: After obtaining the three-phase voltages, the SVPWM modulation method with zero-sequence component injection is used to obtain the PWM switching signal. The specific expression of the injected signal is as follows: It can replace the more complex sector-based SVPWM method and achieve the same effect, while reducing the overall code size of FOC.
[0050] like Figure 6 As shown, the curve represents the change of the alignment angle over time. The curve shows that the alignment process is smooth and the residual angle is small.
[0051] Based on actual vehicle testing, this method features a small residual angle, strong resistance to load disturbances, and smooth switching between power assist and return-to-center states, thus solving existing technical problems.
[0052] In summary, this invention significantly improves the vehicle's active self-centering performance by introducing a speed closed-loop control mechanism and precise self-centering state judgment. Specifically, this method not only ensures rapid and powerful self-centering at low speeds and smooth and gentle self-centering at high speeds, effectively avoiding vehicle yaw and steering wheel oscillation, but also ensures the smoothness and linearity of the self-centering process by meticulously dividing the self-centering state and dynamically selecting the attenuation factor, avoiding the "stuttering" or "overshooting" phenomena in traditional methods. Furthermore, the space vector pulse width modulation method based on zero-sequence component injection used in the field-oriented control system further reduces the computational burden on the microcontroller and improves the system's response speed and stability. The introduction of the field weakening control unit further expands the motor speed range, enabling the system to achieve optimal self-centering quality across the entire speed domain. Real-world vehicle testing results show that this method has a small residual angle, strong resistance to load disturbances, and smooth switching between assist and self-centering states, effectively solving problems in existing technologies and possessing significant practical application value.
[0053] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A vehicle active return-to-center control method for EPS speed closed-loop control, characterized in that, Includes the following steps: Step 1, Signal Acquisition and Processing: Acquire the torque and angle signals of the steering wheel, filter them, and then calculate the actual angle, actual torque, and actual angular velocity of the steering wheel. Step 2, Target Generation: Based on the current vehicle speed, query the pre-calibrated S-curve-shaped return-to-center target curve and generate a target return-to-center angular velocity that changes continuously and smoothly over time. Step 3, State Judgment: Based on the actual angle, actual angular velocity, and actual torque values and their changing trends obtained in Step 1, the current homing state of the vehicle is jointly determined through state machine logic; Step 4, Torque Calculation: The target angular velocity obtained in Step 2 is compared with the actual angular velocity obtained in Step 1 to obtain the angular velocity error. A PI controller is then used to calculate the angular velocity error to generate the basic angular velocity torque. The output of the PI controller includes proportional control output and integral control output. Step 5, Adaptive Attenuation: Based on the vehicle's current alignment status determined in Step 3, dynamically select and output the corresponding proportional attenuation factor and integral attenuation factor; The proportional control output and / or integral control output are selectively attenuated, and the attenuated result is limited to obtain the final safe return torque command. Step 6, Torque Execution: The final safe return torque command obtained in Step 5 is used as the torque setpoint and input to the motor drive system based on field-oriented control to drive the assist motor to generate the corresponding return torque.
2. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 3, the vehicle's current straightening state includes: Steering wheel free return to center: The system takes the lead in the return-to-center process without driver intervention; Reverse steering wheel position during the return-to-center process: The driver applies torque in the opposite direction to the return-to-center direction; During the return-to-center process, when the steering wheel is turned in the same direction: the driver applies torque in the same direction as the return-to-center direction to accelerate the return to center. Steering wheel hold-up mode: The driver applies torque to keep the steering wheel in a non-neutral position; Steering wheel stationary state: The steering wheel is in the near-neutral position and the driver does not intervene.
3. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 5, the judgment rules for dynamically selecting and outputting the corresponding proportional attenuation factor and integral attenuation factor include: When the steering wheel is judged to be in a free return-to-center state, both the proportional attenuation factor and the integral attenuation factor are set to 1 to maintain the full output of the basic return-to-center torque. When the steering wheel is determined to be in a hold state, the proportional attenuation factor is set to a fixed value or a dynamically calculated value less than 1, while the integral attenuation factor is kept at 1, so that the final safe return torque command mainly comes from the integral control output. When the system is determined to be in a state of turning the steering wheel in the opposite direction during the return-to-center process, in a state of turning the steering wheel in the same direction during the return-to-center process, or in a state where the steering wheel is stationary, both the proportional attenuation factor and the integral attenuation factor are set to values less than 1, and the proportional and integral control outputs are attenuated.
4. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 3, characterized in that, In step 5, the method for attenuating the integral control output includes: feeding forward the product of the integral attenuation factor and the integral control output to the speed error input terminal of the PI controller.
5. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 2, the mathematical expression of the S-curve-shaped return target curve includes a piecewise continuous function or a smoothed approximation function of a piecewise continuous function. The curve shape parameters include at least: the maximum return angular velocity, the total time of the return process, and the curve smoothing coefficient. The curve shape parameters are independently calibrated according to the vehicle speed.
6. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 1, a first-order inertial low-pass filter algorithm is used to filter the angle and torque signals. The discretization formula is as follows: ； Where x(n) is the current sampled value, y(n) and y(n-1) are the current and previous filtered output values, and λ is the filter coefficient; The actual angular velocity is obtained by calculating the difference in steering wheel angle between adjacent cycles: ； Where Ts is the sampling period, The steering wheel angles at time n and time n-1 are respectively.
7. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 6, the magnetic field orientation control system employs a space vector pulse width modulation method based on zero-sequence component injection, specifically including: The basic values of the three-phase voltages are calculated from the d-axis voltage Ud and the q-axis voltage Uq using the inverse Park transform and inverse Clark transform; the zero-sequence component is: ； Where Ia, Ib, and Ic are the three-phase currents of the motor collected by the MCU; The zero-sequence component is added to the three-phase voltage base value to obtain the modulation wave signal; the modulation wave signal is compared with the triangular carrier wave to generate the PWM switching signal to drive the three-phase inverter.
8. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 7, characterized in that, In the space vector pulse width modulation method based on zero-sequence component injection, the injected zero-sequence component is equivalent to the modulation effect of traditional seven-segment SVPWM.
9. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, In step 6, the field orientation control system includes a field weakening control unit. The field weakening control unit dynamically adjusts the d-axis current setpoint and q-axis current setpoint based on the motor speed and DC bus voltage. The control strategy of the field weakening control unit is as follows: In the constant torque region below the base speed, a control strategy of Id=0 is adopted; In the constant power region above the base speed, a field weakening control strategy that gradually increases negative Id is adopted; In the deep magnetic weakening region, a maximum torque-voltage ratio control strategy is adopted, and the d-axis current is distributed at the intersection of the voltage limit circle and the current limit circle.
10. The vehicle active return-to-center control method for EPS speed closed-loop control according to claim 1, characterized in that, The control method controls a vehicle electric power steering system, the vehicle electric power steering system comprising: Torque angle sensor, used to detect the torque and angle of the steering wheel in real time; Vehicle speed sensor, used to provide the current vehicle speed signal; An electronic control unit is used to implement a control method; the electronic control unit includes a memory and a processor, the memory storing a computer program. The power steering motor is used to provide steering assistance and return torque according to instructions.