Steering control method and steering control system for vehicle
By using TD filtering and PID cascade control, combined with outer and inner loop feedforward compensation, the overshoot and oscillation problems in traditional PID control are solved, achieving fast response and safety in vehicle steering control, and improving the robustness and applicability of the system.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2025-11-03
- Publication Date
- 2026-07-30
AI Technical Summary
Traditional PID control suffers from overshoot and oscillation in vehicle steering control, making it difficult to balance accuracy and speed. Furthermore, existing optimization schemes have poor applicability when the dynamic characteristics of the system change, are computationally complex, or may saturate the control signal.
The system employs TD filtering combined with PID cascade control, outer loop and inner loop feedforward compensation control. The requested angle is smoothed by the TD filter, and the inner and outer loop feedforward control improves responsiveness and anti-interference. An angle response safety module is also introduced to ensure vehicle safety.
It improves the responsiveness and anti-interference capability of the steering control system, ensuring the safety and robustness of the vehicle under different operating conditions, and reducing overshoot and response time.
Smart Images
Figure CN2025131998_30072026_PF_FP_ABST
Abstract
Description
Steering control methods and steering control systems for vehicles Technical Field
[0001] This invention relates to the field of steering control technology, and more particularly to a steering control method and steering control system for vehicles. Background Technology
[0002] With the advancement of advanced autonomous driving, the accuracy and speed of the angle control strategy of the steering control system, as the main control device for the lateral movement of the vehicle, have become particularly important.
[0003] Current technical solutions primarily utilize Proportional-Integral-Derivative (PID) control strategies to control the steering wheel angle. However, under the demand for rapid response, traditional PID control can lead to overshoot and oscillations, affecting system stability and response quality, making it difficult to balance accuracy and speed. Current optimization schemes mainly improve system response performance by tuning PID parameters, but this requires retuning when system dynamic characteristics change, reducing applicability. Other solutions address nonlinearity and uncertainty by introducing fuzzy control or adaptive control, automatically adjusting control parameters based on system dynamic characteristics; however, these are complex to implement and computationally intensive. Still other solutions use anti-saturation techniques to limit the control signal range to maintain system stability, but in some cases, control signal saturation may still occur. Summary of the Invention
[0004] To overcome the problems existing in related technologies, the present invention provides a steering control method and a steering control system for vehicles.
[0005] According to a first aspect of the present invention, the present invention provides a steering control method for a vehicle, comprising:
[0006] The target angle is obtained by performing TD filtering on the given requested angle.
[0007] Angle PID control processing is performed between the target angle and the current actual angle;
[0008] Perform angular velocity PID control processing between the target angular velocity output by the angle PID control processing and the current actual angular velocity; and
[0009] The output torque of the steering actuator is controlled based on the angular velocity PID control processing, so that the execution result of the steering actuator approaches the target angle.
[0010] In some optional embodiments, the TD filtering process employs the fastest nonlinear filtering process.
[0011] In some optional embodiments, the current actual angular velocity is calculated based on the current actual angle.
[0012] According to some optional embodiments, before performing the TD filtering process, an angle response safety process is performed on the given requested angle to obtain a safe processing angle; the angle response safety process includes:
[0013] Obtain the safe range of angles and the corresponding safe range of angular velocities;
[0014] When the requested angle is within the safe range of the angle, and the angular velocity corresponding to the requested angle is within the safe range of the angular velocity, the safe processing angle is the requested angle;
[0015] When the requested angle exceeds the safe angle range, and / or the angular velocity corresponding to the requested angle exceeds the safe angular velocity range, the safe processing angle is the maximum value of the safe angle range, and the angular velocity corresponding to the safe processing angle is the maximum value of the safe angular velocity range.
[0016] According to some optional embodiments, the step of obtaining the angle safety range and the corresponding angular velocity safety range includes:
[0017] The safe angle range is obtained based on the set range of lateral acceleration of the vehicle.
[0018] The safe range of angular velocity is obtained based on the optimal relative damping coefficient for the angle.
[0019] In some optional embodiments, the target angular velocity is compensated by outer loop feedforward compensation control.
[0020] In some alternative embodiments, the output torque of the angular velocity PID control is compensated by inner loop feedforward compensation control.
[0021] According to a second aspect of the present invention, the present invention also provides a steering control system, comprising: a TD filter, an angle PID controller, an angular velocity PID controller, and a steering actuator. The TD filter is configured to perform TD filtering on a given requested angle to obtain a target angle; the angle PID controller is configured to perform angle PID control processing between the target angle and the current actual angle; the angular velocity PID controller is connected in series with the angle PID controller and is configured to perform angular velocity PID control processing between the target angular velocity output by the angle PID controller and the current actual angular velocity; and the steering actuator is configured to be controlled by the output torque of the angular velocity PID controller so that the execution result of the steering actuator approaches the target angle.
[0022] In some optional embodiments, the TD filter is a fastest nonlinear TD filter, which employs fastest nonlinear filtering processing.
[0023] According to some optional embodiments, the steering control system further includes an angle response safety module configured to perform angle response safety processing on a given requested angle prior to the TD filtering step.
[0024] According to some optional embodiments, the steering control system further includes an outer loop feedforward module configured to perform outer loop feedforward compensation control on the target angular velocity obtained by the angle PID controller.
[0025] According to some optional embodiments, the steering control system further includes an inner loop feedforward module 7, which is configured to perform inner loop feedforward compensation control on the output torque obtained by the angular velocity PID controller.
[0026] According to the technical solution in the above embodiments of the present invention, a PID cascade control method is adopted. The outer loop takes the requested angle as a given and uses closed-loop control to obtain the target angular velocity. The inner loop takes the target angular velocity and the current actual angular velocity as the control objects to obtain the output torque of the steering actuator. This enables the current actual angle to follow and approach the target angle, while improving the system's response speed and anti-interference.
[0027] Specifically, firstly, by performing TD filtering on a given request angle, the control and signal processing of the dynamic system can be focused on. By extracting the differential signal and arranging the transition process, its smoothing function is achieved, which solves the problems of overshoot control in traditional PID control and long transition time of low-pass filter in step response residual.
[0028] In addition, this invention adds an angle response safety module. While responding to the angle, the system is optimized based on lateral acceleration, the optimal relative damping coefficient of the angle, and vehicle safety parameters, which can ensure the safe operation of the vehicle, adapt to different working conditions, and improve the safety and robustness of the system.
[0029] In addition, by introducing feedforward control in the inner and outer loops, the impact of TD filtering on response time is reduced, enabling the system to have better responsiveness and fast tracking performance. Attached Figure Description
[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 shows a flowchart of a steering control method according to some embodiments;
[0032] Figure 2 shows the time-domain waveform of the signal processed by TD filtering according to some embodiments;
[0033] Figure 3 shows the time-domain waveform of the outer loop feedforward compensation signal according to some embodiments; and
[0034] Figure 4 shows a structural block diagram of a steering control system according to some embodiments. Detailed Implementation
[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.
[0036] This invention relates to the field of steering control technology for vehicle chassis. With the advancement of advanced autonomous driving, the accuracy and speed of steering control strategies, as the primary controller for lateral vehicle movement, are particularly important. Steering control systems can be, but are not limited to, electro-hydraulic power steering (EHPS) and electric power steering (EPS). The accuracy of the system lies in minimizing overshoot and steady-state error during the response to the upper-level angle signal, and ensuring a smooth response without abrupt changes. The speed of the system lies in controlling the response, following, and adjustment time of the upper-level angle signal within a minimal range. This invention effectively ensures angle control accuracy by introducing a tracking differential (TD) filter. Furthermore, it incorporates inner and outer loop feedforward control to effectively improve response speed. In addition, functional safety design is added to enhance the system's safety and robustness.
[0037] This invention provides a steering control method. Figure 1 shows a flowchart of a steering control method according to some embodiments. Referring to Figure 1, in some embodiments, the steering control method includes:
[0038] The target angle is obtained by performing TD filtering on the given requested angle.
[0039] Angle PID control processing is performed between the target angle and the current actual angle;
[0040] Perform angular velocity PID control processing between the target angular velocity output by the angle PID control processing and the current actual angular velocity; and
[0041] The output torque of the steering actuator 4 is controlled based on the angular velocity PID control processing so that the execution result of the steering actuator 4 approaches the target angle.
[0042] According to the technical solution in the above embodiments of the present invention, the requested angle can be given by the Advanced Driver Assistance System (ADAS), and after TD filtering, angle PID control processing, and angular velocity PID control processing, the output torque of the actuator motor is controlled, thereby controlling the steering actuator to perform steering. The current actual angle refers to the angle at which the steering actuator performs steering, and the current actual angular velocity refers to the angular velocity at which the steering actuator performs steering.
[0043] Specifically, in some embodiments, the steering actuator 4 may include an actuator motor and a transmission mechanism, such as a reducer, disposed at the output end of the actuator motor; thus, there is a certain transmission ratio between the output end of the transmission mechanism and the output end of the actuator motor. The current actual angle refers to the current actual steering angle output by the output end of the transmission mechanism, and the current actual angular velocity refers to the current actual steering angular velocity output by the output end of the transmission mechanism.
[0044] In some other embodiments, the steering actuator 4 may further include a steering wheel, and a transmission mechanism, such as a reducer, may be provided between the steering wheel and the actuator motor to create a certain transmission ratio between the steering wheel and the output of the actuator motor. The current actual angle refers to the current actual angle of the steering wheel; the current actual angular velocity refers to the current actual angular velocity of the steering wheel.
[0045] The current actual angle and current actual angular velocity can be obtained directly by the sensor or through calculation after measurement. For example, the current actual angle can be measured by a torque angle sensor (TAS sensor), and the current actual angular velocity can be calculated based on the current actual angle, for example, by differentiating the current actual angle.
[0046] According to the technical solution in the above embodiments of the present invention, and in conjunction with Figure 1, the steering control method adopts PID cascade control. The outer loop takes the requested angle as a given and uses closed-loop control to obtain the target angular velocity. The inner loop takes the target angular velocity and the current actual angular velocity as the control objects to obtain the output torque of the actuator motor, so that the current actual angle can follow and approach the target angle, while improving the system's response speed and anti-interference ability.
[0047] Specifically, Figure 2 shows the time-domain waveform of the signal processed by TD filtering according to some embodiments. Referring to Figure 2, the solid lines represent the original signal at a given requested angle, and the figure shows the waveform of the step signal; the dashed lines represent the waveform of the signal output after TD filtering. It can be seen that the waveform of the TD-filtered signal has undergone a smoothing process.
[0048] Because traditional PID control suffers from a contradiction between overshoot and speed, in order to improve the speed of the system while reducing overshoot, embodiments of the present invention perform TD filtering on a given request angle, which can focus on the control and signal processing of the dynamic system. By extracting the differential signal and arranging the transition process, its smoothing function is achieved, which solves the problems of overshoot control in traditional PID control and the long transition time of low-pass filters in step response residuals.
[0049] The TD filtering process achieves control and signal processing of dynamic systems by extracting the differential signal and arranging the transient response. Furthermore, to track the requested angle signal for a given input more quickly, and considering the discretization of the steering control system, in some embodiments, the TD filtering process employs the fastest nonlinear filtering.
[0050] The fastest discrete control function is introduced below.
[0051] Where fsg(x,d)=(sign(x+d)-sign(xd)) / 2
[0052] The implementation steps of the fastest nonlinear filtering process are as follows:
[0053] Where r is the speed factor and h is the step size.
[0054] Figure 2 shows the effect of the fastest nonlinear filtering process. Using the fastest nonlinear filtering process, the signal can be tracked more quickly for a given input angle.
[0055] The introduction of TD filtering can effectively suppress the overshoot of PID control, but it also leads to a lag in the response time of the step response. In order to achieve a fast response, for example, to achieve a response time of less than 20ms, in some embodiments, as shown in Figure 1, an outer loop feedforward compensation control is introduced before the angle PID control process to compensate for the target angle and improve the responsiveness of steering control.
[0056] Specifically, Figure 3 shows the time-domain waveform of the outer loop feedforward compensation signal according to some embodiments. As shown in Figure 3, the solid lines represent the target angle signal waveform; the dashed lines represent the waveform of the difference between the target angle and the current actual angle; and the dotted solid lines represent the outer loop feedforward compensation waveform. Combining Figures 1 and 3, it can be seen that by introducing outer loop feedforward compensation control, i.e., feedforward compensation for the angle PID, the angular velocity of the steering control system can be advanced, making the current actual angle approach the target angle more quickly, thereby improving the system's responsiveness.
[0057] Furthermore, as shown in Figure 1, by introducing inner loop feedforward compensation control, that is, feedforward compensation for the angular velocity PID, the output torque of the angular velocity PID control is compensated to obtain fast tracking of the sweep frequency response, such as fast tracking of the sweep frequency response within 3Hz, and then the actuator motor in the steering actuator 4 can be controlled so that the current actual angle approaches the target angle more quickly.
[0058] The compensation amounts for the outer and inner loop feedforwards can be obtained through simulation or calibration, and are not limited here. By introducing compensation control for the inner and outer loop feedforwards, the impact of TD filtering on the response time can be reduced, giving the system better responsiveness and faster tracking performance.
[0059] Furthermore, in some embodiments, as shown in FIG1, before performing the TD filtering process, an angle response safety process can be performed on the given request angle to obtain a safety processing angle.
[0060] Specifically, the steps of the angle response safety processing include:
[0061] Obtain the safe range of angles and the corresponding safe range of angular velocities;
[0062] When the requested angle is within the safe range of the angle, and the angular velocity corresponding to the requested angle is within the safe range of the angular velocity, the safe processing angle is the requested angle.
[0063] When the requested angle exceeds the safe angle range, and / or the angular velocity corresponding to the requested angle exceeds the safe angular velocity range, the safe processing angle is the maximum value of the safe angle range, and the angular velocity corresponding to the safe processing angle is the maximum value of the safe angular velocity range.
[0064] In other words, a safe processing angle is a request angle whose angle and corresponding angular velocity are limited to a safe range.
[0065] Furthermore, the step of obtaining the angular safety range and the corresponding angular velocity safety range includes:
[0066] Based on the set range of lateral acceleration of the vehicle, the safe angle range is obtained; and
[0067] Based on the optimal relative damping coefficient for the angle, the safe range of angular velocity is obtained.
[0068] To ensure the safety of the actual vehicle under angle control, angle response safety processing is implemented for the requested angle to prevent vehicle instability. When designing the various parameters for angle response safety processing, this invention primarily considers vehicle roll parameters. This is achieved by inputting lateral acceleration, yaw rate, longitudinal acceleration, and various parameters of the four tires. For example, lateral acceleration α can be used as the input parameter. y Within the range of <0.3g, a vehicle model is established for simulation to obtain the safe range of angles; and based on the set optimal relative damping coefficient of the angle, for example, the optimal relative damping coefficient of the angle can be set to 0.707, the safe range of angular velocity is obtained.
[0069] In this way, by handling the angle response safety, it can be ensured that the requested angle and the corresponding angular velocity are limited to a safe range, so as to ensure the safety of the actual vehicle under angle and angular velocity control and avoid rollover.
[0070] The above embodiments perform angle response safety processing on a given requested angle. While responding to the angle, the system optimizes the design based on lateral acceleration, the optimal relative damping coefficient of the angle, and vehicle safety parameters. This can prevent vehicle instability, ensure safe vehicle operation, adapt to different working conditions, and improve the system's safety and robustness.
[0071] On the other hand, the present invention also provides a steering control system. Figure 4 shows a structural block diagram of a steering control system according to some embodiments. As shown in Figure 4, the steering control system includes: a TD filter 1, an angle PID controller 2, an angular velocity PID controller 3, and a steering actuator 4.
[0072] Specifically, TD filter 1 is configured to perform TD filtering on a given requested angle to obtain the target angle. Angle PID controller 2 is configured to perform angle PID control processing between the target angle and the current actual angle. Angular velocity PID controller 3 is connected in series with angle PID controller 2 and is configured to perform angular velocity PID control processing between the target angular velocity output by angle PID controller 2 and the current actual angular velocity. Steering actuator 4 is configured to be controlled by the output torque of angular velocity PID controller 3 so that the execution result of steering actuator 4 approaches the target angle.
[0073] The steering actuator 4 includes an actuator motor and a transmission mechanism located at the output end of the actuator motor; the output torque of the angular velocity PID controller 3 directly controls the actuator motor.
[0074] In some embodiments, TD filter 1 is a fastest nonlinear TD filter, which employs fastest nonlinear filtering processing.
[0075] In some embodiments, as shown in FIG4, the steering control system further includes an angle response safety module 5, which is configured to perform angle response safety processing on a given requested angle before performing the TD filtering process.
[0076] In some embodiments, as shown in FIG4, the steering control system further includes an outer loop feedforward module 6, which is configured to perform outer loop feedforward compensation control on the target angular velocity obtained by the angle PID controller 2. By compensating the target angular velocity output by the angle PID controller 2 through the outer loop feedforward module 6, the angular velocity of the steering control system can be responded to earlier, so that the current actual angle approaches the target angle more quickly, thereby improving the responsiveness of the system.
[0077] In some embodiments, as shown in FIG4, the steering control system further includes an inner loop feedforward module 7, which is configured to perform inner loop feedforward compensation control on the output torque obtained by the angular velocity PID controller 3. By compensating the output torque of the angular velocity PID controller 3 through the inner loop feedforward module 7, a fast tracking of the sweep frequency response can be obtained, thereby controlling the actuator motor in the steering actuator 4 so that the current actual angle approaches the target angle more quickly.
[0078] The steering control system is capable of executing the steering control method as described in the above embodiments. For the specific steps executed by the steering control system, please refer to the detailed description of the steering control method above; they will not be repeated here.
[0079] Through the steering control method and steering control system using the method described in the above embodiments of the present invention, by performing TD filtering on a given requested angle, the control and signal processing of the dynamic system can be focused on. Smoothing is achieved by extracting the differential signal and arranging the transition process, solving the problems of overshoot control in traditional PID control and the long residual transition time of low-pass filters in step response. Furthermore, the present invention adds an angle response safety module. While responding to the angle, the system limits the safe range of the requested angle based on lateral acceleration and the optimal relative damping coefficient of the angle, ensuring safe vehicle operation, preventing vehicle roll, and improving the system's safety and robustness. In addition, by introducing inner and outer loop feedforward control, the impact of TD filtering on the response time is reduced, giving the system better responsiveness and faster tracking performance.
[0080] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.
[0081] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.
[0082] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.
Claims
1. A steering control method for a vehicle, characterized in that, include: The target angle is obtained by performing TD filtering on the given requested angle. Angle PID control processing is performed between the target angle and the current actual angle; The target angular velocity output by the angle PID control processing is compared with the current actual angular velocity using angular velocity PID control processing. as well as The output torque of the steering actuator (4) is controlled based on the angular velocity PID control processing so that the execution result of the steering actuator (4) approaches the target angle.
2. The steering control method according to claim 1, wherein, The TD filtering process employs the fastest nonlinear filtering process.
3. The steering control method according to claim 1, wherein, The current actual angular velocity is calculated based on the current actual angle.
4. The steering control method according to claim 1, wherein, Before performing the TD filtering process, the given requested angle is subjected to angle response safety processing to obtain a safe processing angle; The steps of the angle response safety processing include: Obtain the safe range of angles and the corresponding safe range of angular velocities; When the requested angle is within the safe range of the angle, and the angular velocity corresponding to the requested angle is within the safe range of the angular velocity, the safe processing angle is the requested angle; When the requested angle exceeds the safe angle range, and / or the angular velocity corresponding to the requested angle exceeds the safe angular velocity range, the safe processing angle is the maximum value of the safe angle range, and the angular velocity corresponding to the safe processing angle is the maximum value of the safe angular velocity range.
5. The steering control method according to claim 4, wherein, The steps of obtaining the angle safety range and the corresponding angular velocity safety range include: The safe angle range is obtained based on the set range of lateral acceleration of the vehicle. The safe range of angular velocity is obtained based on the optimal relative damping coefficient for the angle.
6. The steering control method according to claim 1, wherein, The target angular velocity is compensated by the outer loop feedforward compensation control.
7. The steering control method according to claim 6, wherein, The output torque of the angular velocity PID control is compensated by the inner loop feedforward compensation control.
8. A steering control system, characterized in that, include: The system includes a TD filter (1), an angle PID controller (2), an angular velocity PID controller (3), and a steering actuator (4); among which, The TD filter (1) is configured to perform TD filtering on a given requested angle to obtain the target angle; The angle PID controller (2) is configured to perform angle PID control processing between the target angle and the current actual angle; The angular velocity PID controller (3) is connected in series with the angle PID controller (2) and is configured to perform angular velocity PID control processing between the target angular velocity output by the angle PID controller (2) and the current actual angular velocity; as well as The steering actuator (4) is configured to be controlled by the output torque of the angular velocity PID controller (3) so that the execution result of the steering actuator (4) approaches the target angle.
9. The steering control system according to claim 8, wherein, The TD filter (1) is a fastest nonlinear TD filter, and the fastest nonlinear TD filter adopts the fastest nonlinear filtering process.
10. The steering control system according to claim 8 further includes an angle response safety module (5) configured to perform angle response safety processing on the given requested angle before performing the TD filtering process.
11. The steering control system according to claim 8 further includes an outer loop feedforward module (6), which is configured to perform outer loop feedforward compensation control on the target angular velocity obtained by the angle PID controller (2).
12. The steering control system according to claim 11 further includes an inner loop feedforward module (7) configured to perform inner loop feedforward compensation control on the output torque obtained by the angular velocity PID controller (3).