Steering wheel angle closed-loop control performance optimization method and device, equipment and medium
By optimizing the closed-loop control of steering wheel angle and using a PID controller and feedforward gain to optimize the steering wheel angle response, the problem of slow response and large error in small-angle control of L4 autonomous vehicles is solved, and fast and stable steering angle control is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING JINGWEI HIRAIN TECH CO INC
- Filing Date
- 2025-06-10
- Publication Date
- 2026-06-23
AI Technical Summary
Level 4 autonomous vehicles exhibit insufficient steering wheel angle response speed during small-angle control, excessive execution time under ramp input, and significant phase delay and amplitude error under sinusoidal input.
By acquiring the difference between the target steering angle and the actual steering angle in real time, the target steering angle velocity is calculated using a PID controller. Combined with the rotation angle of the motor rotor and the vehicle speed, the feedforward gain and damping control torque are determined to optimize the closed-loop control of the steering wheel angle.
It improves the steering wheel angle response speed, reduces phase delay and amplitude error under sinusoidal input, and ensures the speed and stability of steering wheel angle control.
Smart Images
Figure CN120482143B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of autonomous driving technology, and in particular to a method, apparatus, device and medium for optimizing the performance of closed-loop control of steering wheel angle. Background Technology
[0002] Currently, Level 4 autonomous driving technology is still under development, and its maturity has not yet reached the point where driver intervention is unnecessary. Therefore, Level 4 autonomous vehicles still need to retain a traditional steering wheel for driver control. Level 4 autonomous driving involves many situations where the steering wheel angle is controlled at small angles. When the Level 4 autonomous driving function is activated, and the ADU (Autonomous Driving Unit) sends a small-angle steering command requiring a rapid response from the fully redundant R-EPS (Rack-Electronic Power Steering), if a large-slope ramp signal or a high-frequency sine wave signal is input, conventional closed-loop steering control algorithms suffer from insufficient dynamic response speed, excessively long execution time under ramp inputs, and large phase delays and amplitude errors under sine wave inputs. Summary of the Invention
[0003] To address the aforementioned technical problems, this application provides a method, apparatus, electronic device, and storage medium for optimizing the closed-loop control performance of steering wheel angle.
[0004] According to a first aspect of this application, a method for optimizing the closed-loop control performance of steering wheel angle is provided, comprising:
[0005] After the autonomous vehicle enters the autonomous driving mode, the target steering angle and the actual steering angle of the steering wheel are acquired in real time. The difference between the target steering angle and the actual steering angle is input into the first PID controller to obtain the target steering angle speed.
[0006] The rotation angle and direction of the motor rotor are acquired in real time. Based on the rotation angle and direction of the motor rotor and the transmission ratio between the steering wheel and the motor, the actual angular velocity of the steering wheel is determined.
[0007] The rate of change of the target steering wheel angle is determined by differentiating the target steering wheel angle with respect to the signal period, and the rate of change of the target steering wheel angle is limited by the speed of the autonomous vehicle to obtain the limited rate of change of the target steering wheel angle.
[0008] The feedforward gain is determined based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein the feedforward gain is inversely correlated with the absolute value.
[0009] The feedforward compensation angular velocity is determined based on the restricted target steering wheel angle change rate and the feedforward gain.
[0010] The difference between the sum of the target steering wheel angular velocity and the feedforward compensated steering angular velocity and the actual steering wheel angular velocity is input into the second PID controller to obtain the target output torque.
[0011] Optionally, the method for optimizing the closed-loop control performance of the steering wheel angle further includes:
[0012] When the rate of change of the target steering wheel angle meets the preset condition, the nonlinear damping control coefficient K1 is set to 1; when the rate of change of the target steering wheel angle does not meet the preset condition, the nonlinear damping control coefficient K1 is set to 0.
[0013] When the rotational speed of the motor rotor is less than or equal to the preset speed threshold, the motor rotor rotation coefficient Ms is set to 0; when the rotational speed of the motor rotor is greater than the preset speed threshold, the motor rotor rotation coefficient Ms is set according to the rotational speed of the motor rotor; wherein, the motor rotor rotation coefficient Ms is positively correlated with the rotational speed of the rotor.
[0014] The vehicle speed coefficient Vs is set according to the vehicle speed of the autonomous vehicle, where the vehicle speed coefficient Vs is proportional to the vehicle speed;
[0015] The deformation angle of the torque angle sensor is obtained, and the deformation angle is analyzed into the steering torque of the steering wheel. The steering torque coefficient Tp is set according to the steering torque of the steering wheel, wherein the steering torque coefficient Tp is proportional to the steering torque of the steering wheel.
[0016] Multiply the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, and the steering wheel hand torque coefficient Tp, and process the product using the nonlinear damping gain Kg to obtain the nonlinear damping control torque, so that the nonlinear damping control torque is within the preset compensation torque range.
[0017] The target output torque is superimposed with the nonlinear damping control torque to obtain the final output torque.
[0018] Optionally, the process of limiting the rate of change of the target steering wheel angle using the speed of the autonomous vehicle includes:
[0019] Based on the speed of the autonomous vehicle, a target turning angle change rate limit is determined, wherein the target turning angle change rate limit is inversely proportional to the vehicle speed;
[0020] When the target steering angle change rate is greater than the target steering angle change rate limit, the target steering angle change rate is set to the target steering angle change rate limit.
[0021] No action is taken when the target steering angle change rate is less than or equal to the target steering angle change rate limit.
[0022] Optionally, determining the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain includes:
[0023] The restricted target steering angle change rate is multiplied by the feedforward gain, and the resulting product is filtered to obtain the feedforward compensated steering angle velocity.
[0024] Optionally, determining the rate of change of the target steering wheel angle by differentiating it with respect to the signal period includes:
[0025] If the absolute value of the target steering angle is less than or equal to a preset steering angle threshold, and the slope of the ramp input is greater than a preset slope threshold or the frequency of the sine input is greater than a preset frequency, the target steering angle is differentiated with respect to the signal period to determine the rate of change of the target steering angle.
[0026] Optionally, determining the actual angular velocity of the steering wheel based on the rotation angle and direction of the motor rotor and the transmission ratio between the steering wheel and the motor includes:
[0027] Determine the rotational speed of the motor rotor based on its rotational angle and direction.
[0028] Based on the transmission ratio between the steering wheel and the motor, the rotational angular velocity of the motor rotor is converted into the actual angular velocity of the steering wheel.
[0029] Optionally, the method for determining whether the target steering angle change rate of the steering wheel meets the preset condition is as follows:
[0030] When the rate of change of the target steering wheel angle is 0 and the duration is greater than or equal to a preset time threshold, it is determined that the rate of change of the target steering wheel angle meets the preset condition.
[0031] If the target steering angle change rate is not 0, or if the target steering angle change rate is 0 but the duration is less than a preset time threshold, then it is determined that the target steering angle change rate does not meet the preset condition.
[0032] According to a second aspect of this application, a steering wheel angle closed-loop control performance optimization device is provided, comprising:
[0033] The target steering angle velocity determination module is used to acquire the target steering angle and the actual steering angle of the steering wheel in real time after the autonomous vehicle enters the autonomous driving mode, and input the difference between the target steering angle and the actual steering angle into the first PID controller to obtain the target steering angle velocity.
[0034] The actual angular velocity determination module is used to acquire the rotation angle and rotation direction of the motor rotor in real time, and determine the actual angular velocity of the steering wheel based on the rotation angle and rotation direction of the motor rotor and the transmission ratio between the steering wheel and the motor.
[0035] The module for determining the rate of change of the target steering angle after limitation is used to differentiate the target steering angle of the steering wheel with respect to the signal period, determine the rate of change of the target steering angle of the steering wheel, and use the speed of the autonomous vehicle to limit the rate of change of the target steering angle of the steering wheel to obtain the rate of change of the target steering angle of the steering wheel after limitation.
[0036] The feedforward gain determination module is used to determine the feedforward gain based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein the feedforward gain is inversely correlated with the absolute value.
[0037] The feedforward compensation angular velocity determination module is used to determine the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain.
[0038] The target output torque determination module is used to input the difference between the sum of the target steering wheel angular velocity and the feedforward compensation angular velocity and the actual steering wheel angular velocity into the second PID controller to obtain the target output torque.
[0039] Optionally, the steering wheel angle closed-loop control performance optimization device further includes:
[0040] The nonlinear damping control coefficient setting module is used to set the nonlinear damping control coefficient K1 to 1 when the target steering angle change rate of the steering wheel meets the preset conditions, and to set the nonlinear damping control coefficient K1 to 0 when the target steering angle change rate of the steering wheel does not meet the preset conditions.
[0041] The motor rotor rotation coefficient setting module is used to set the motor rotor rotation coefficient Ms to 0 when the rotation speed of the motor rotor is less than or equal to a preset speed threshold; and to set the motor rotor rotation coefficient Ms according to the rotation speed of the motor rotor when the rotation speed of the motor rotor is greater than the preset speed threshold; wherein, the motor rotor rotation coefficient Ms is positively correlated with the rotation speed of the rotor.
[0042] The vehicle speed coefficient setting module is used to set the vehicle speed coefficient Vs according to the vehicle speed of the autonomous vehicle, wherein the vehicle speed coefficient Vs is proportional to the vehicle speed.
[0043] The steering wheel hand torque coefficient setting module is used to obtain the deformation angle of the torque angle sensor, resolve the deformation angle into the steering torque of the steering wheel, and set the steering wheel hand torque coefficient Tp according to the steering torque of the steering wheel, wherein the steering wheel hand torque coefficient Tp is proportional to the steering torque of the steering wheel;
[0044] The nonlinear damping control torque determination module is used to multiply the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, and the steering wheel hand torque coefficient Tp, and process the obtained product using the nonlinear damping gain Kg to obtain the nonlinear damping control torque, so that the nonlinear damping control torque is within the preset compensation torque range.
[0045] The final output torque determination module is used to superimpose the target output torque with the nonlinear damping control torque to obtain the final output torque.
[0046] Optionally, the module for determining the limited target steering angle change rate is specifically used to differentiate the target steering angle with respect to the signal period to determine the target steering angle change rate, and to determine a limit value for the target steering angle change rate based on the vehicle speed of the autonomous vehicle, wherein the limit value for the target steering angle change rate is inversely proportional to the vehicle speed; when the target steering angle change rate is greater than the limit value for the target steering angle change rate, the target steering angle change rate is set to the limit value for the target steering angle change rate to obtain the limited target steering angle change rate; when the target steering angle change rate is less than or equal to the limit value for the target steering angle change rate, no processing is performed.
[0047] Optionally, the feedforward compensation angular velocity determination module is specifically used to multiply the limited target steering wheel angle change rate with the feedforward gain, and filter the resulting product to obtain the feedforward compensation angular velocity.
[0048] Optionally, the restricted target angle change rate determination module is specifically used to determine the steering wheel target angle change rate by differentiating the steering wheel target angle with respect to the signal period if the absolute value of the steering wheel target angle is less than or equal to a preset angle threshold, and the slope of the ramp input is greater than a preset slope threshold or the frequency of the sine input is greater than a preset frequency, and then using the speed of the autonomous vehicle to restrict the steering wheel target angle change rate to obtain the restricted steering wheel target angle change rate.
[0049] Optionally, the actual angular velocity determination module is specifically used to acquire the rotation angle and rotation direction of the motor rotor in real time, determine the rotation speed of the motor rotor based on the rotation angle and rotation direction of the motor rotor, and convert the rotation angular velocity of the motor rotor into the actual angular velocity of the steering wheel based on the transmission ratio between the steering wheel and the motor.
[0050] Optionally, the steering wheel angle closed-loop control performance optimization device further includes:
[0051] The judgment module is used to determine that the target steering angle change rate meets the preset condition when the target steering angle change rate is 0 and the duration is greater than or equal to a preset time threshold; and to determine that the target steering angle change rate does not meet the preset condition when the target steering angle change rate is not 0, or the target steering angle change rate is 0 but the duration is less than the preset time threshold.
[0052] According to a third aspect of this application, an electronic device is provided, comprising: a processor configured to execute a computer program stored in a memory, wherein the computer program, when executed by the processor, implements the method described in the first aspect.
[0053] According to a fourth aspect of this application, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the method described in the first aspect.
[0054] According to a fifth aspect of this application, a computer program product is provided that, when the computer program product is run on a computer, causes the computer to perform the method described in the first aspect.
[0055] The technical solution provided in this application has the following advantages compared with the prior art:
[0056] When the autonomous driving control unit sends a steering wheel angle request to the fully redundant R-EPS via the steering angle interface, it calculates the rate of change of the target steering wheel angle and limits it using the vehicle speed, obtaining the limited rate of change. The feedforward gain is determined based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle. Typically, the steering wheel angle response is not fast enough when the angle difference is small. Therefore, a larger feedforward gain is set where the angle difference is small, and a smaller feedforward gain is set where the angle difference is large. When the angle difference is small, increasing the feedforward gain enhances the feedforward compensation effect, accelerating the steering wheel response speed; when the angle difference is large, the feedforward compensation gain is small, and the feedforward compensation effect is weak, avoiding response overshoot. Simultaneously, ramp or sinusoidal inputs can improve the response speed of the fully redundant R-EPS, especially addressing the issue of large phase delay under sinusoidal input. When the sinusoidal input frequency is high, the R-EPS response phase delay is significant, thus mitigating this problem. Attached Figure Description
[0057] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0058] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0059] Figure 1 This is a schematic diagram showing the connection relationship between the fully redundant R-EPS and ADU on the CAN bus in the embodiments of this application;
[0060] Figure 2 This is a flowchart of a method for optimizing the closed-loop control performance of the steering wheel angle of an autonomous vehicle in an embodiment of this application;
[0061] Figure 3 This is a schematic diagram illustrating the determination of feedforward compensation angular velocity in an embodiment of this application;
[0062] Figure 4 The slope input response curve is shown when the target angular velocity feedforward compensation algorithm is not enabled.
[0063] Figure 5 This is the ramp input response curve when the target angular velocity feedforward compensation algorithm is enabled in the embodiments of this application;
[0064] Figure 6 The sinusoidal input response curve when the target angular velocity feedforward compensation algorithm is not enabled;
[0065] Figure 7 This is the sinusoidal input response curve when the target angular velocity feedforward compensation algorithm is enabled in the embodiments of this application;
[0066] Figure 8 The response curve of the ADU controlling the steering wheel rotation;
[0067] Figure 9 This is another flowchart of the steering wheel angle closed-loop control performance optimization method in the embodiments of this application;
[0068] Figure 10 This is a schematic diagram of a nonlinear damping algorithm in an embodiment of this application;
[0069] Figure 11 This is a schematic diagram of a steering wheel angle closed-loop control performance optimization method in an embodiment of this application;
[0070] Figure 12 This is a schematic diagram of a structure of an autonomous vehicle steering wheel angle closed-loop control performance optimization device in an embodiment of this application.
[0071] Figure 13 This is a schematic diagram of the structure of an electronic device in an embodiment of this application. Detailed Implementation
[0072] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0073] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.
[0074] Figure 1 This diagram illustrates the connection between the fully redundant R-EPS and ADU on the CAN bus in this embodiment. Both controllers in the fully redundant R-EPS product possess independent steering angle control capabilities. If either controller fails, the other, fault-free controller can continue operating as the master controller. The fully redundant R-EPS product's ECU (Electronic Control Unit) provides interfaces for steering wheel angle requests, control requests, and speed limits to the ADU, and sends its own response status to the ADU via CAN communication messages.
[0075] See Figure 2 , Figure 2This is a flowchart of a method for optimizing the closed-loop control performance of steering wheel angle in an embodiment of this application, which may include the following steps:
[0076] Step S202: After the autonomous vehicle enters the autonomous driving mode, the target steering angle and the actual steering angle of the steering wheel are acquired in real time. The difference between the target steering angle and the actual steering angle is input into the first PID controller to obtain the target steering angle speed.
[0077] The fully redundant R-EPS receives control requests from the ADU. When the fully redundant R-EPS's own state meets the requirements for entering autonomous driving mode, the front wheel steering control function of the autonomous vehicle is activated. The ADU sends a steering wheel angle request to the fully redundant R-EPS, which includes the target steering wheel angle. The input modes for the steering wheel angle request include ramp input or sine input. The TAS (Torque Angle Sensor) can detect the angle turned by the steering wheel and send the detected signal to the R-EPS ECU via the SENT signal transmission protocol. The R-EPS ECU interprets this signal as the actual angle turned by the steering wheel, i.e., the actual steering wheel angle.
[0078] There is usually a certain error between the target steering wheel angle and the actual steering wheel angle. By calculating the difference between the target steering wheel angle and the actual steering wheel angle, and inputting this difference into the first PID controller, the target steering wheel angle velocity can be obtained. This control loop is an angle closed loop, and the actual steering wheel angle is the feedback angle of the angle closed loop.
[0079] Step S204: Obtain the rotation angle and rotation direction of the motor rotor in real time, and determine the actual angular velocity of the steering wheel based on the rotation angle and rotation direction of the motor rotor and the transmission ratio between the steering wheel and the motor.
[0080] The fully redundant R-EPS motor is a permanent magnet synchronous motor. The rotation angle and direction of the motor rotor are obtained through an RPS (Rotation Position Sensor). Based on the rotation angle and direction, the rotational speed of the motor rotor is determined. For example, the rotational speed of the motor rotor can be estimated using a Kalman filter algorithm. Based on the transmission ratio between the steering wheel and the motor, the rotational angular velocity of the motor rotor is converted into the actual angular velocity of the steering wheel. The actual angular velocity of the steering wheel is used as the feedback angular velocity for the speed closed loop. In related technologies, the difference between the target steering wheel angular velocity and the actual steering wheel angular velocity is processed by a second PID controller to obtain the target output torque; this control loop is the speed closed loop. It can be seen that existing steering wheel angle closed-loop control includes both angle and speed closed loops.
[0081] Step S206: Differentiate the target steering angle with respect to the signal period to determine the rate of change of the target steering angle, and use the speed of the autonomous vehicle to limit the rate of change of the target steering angle to obtain the limited rate of change of the target steering angle.
[0082] The target steering angle rate feedforward compensation algorithm can refer to the vehicle speed of the autonomous vehicle for feedforward compensation. Optionally, a target steering angle change rate limit value can be determined based on the vehicle speed. This limit value is inversely proportional to the vehicle speed. The higher the vehicle speed, the lower the corresponding target steering angle change rate limit value, thus improving driving safety. For example, different target steering angle change rate limit values can be set based on different vehicle speed gradients. If the autonomous vehicle speed is within a certain speed gradient, the target steering angle change rate limit value corresponding to that speed gradient is determined as the target steering angle change rate limit value corresponding to the autonomous vehicle speed. When the target steering angle change rate is greater than the target steering angle change rate limit value, the target steering angle change rate is set to the limit value to avoid excessively large changes. When the target steering angle change rate is less than or equal to the limit value, no action is taken.
[0083] In some embodiments, if the absolute value of the target steering angle is less than or equal to a preset steering angle threshold, such as 20°, it is considered that the requested steering angle is small. Furthermore, if the slope of the ramp input is greater than a preset slope threshold or the frequency of the sine input is greater than a preset frequency, the R-EPS response is not fast enough, and the response delay and amplitude error are large during sine input. This means that adjusting the parameters of the steering angle closed loop and the speed closed loop cannot achieve both fast and stable dynamic performance. Therefore, step S206 is executed, which involves controlling the steering wheel according to the target steering angle velocity feedforward compensation algorithm.
[0084] If the absolute value of the target steering angle is greater than the preset steering angle threshold, or if the absolute value of the target steering angle is less than or equal to the preset steering angle threshold and the slope of the ramp input is less than or equal to the preset slope threshold or the frequency of the sine input is less than or equal to the preset frequency, the steering wheel can be controlled according to the existing steering wheel angle closed-loop control method because R-EPS has a relatively fast response.
[0085] Step S208: Determine the feedforward gain based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein the feedforward gain is inversely correlated with the absolute value.
[0086] Typically, the steering wheel response is not fast enough when the angle difference is small. Therefore, a larger feedforward gain is set where the angle difference is small, and a smaller feedforward gain is set where the angle difference is large. When the angle difference is small, the feedforward compensation effect is enhanced by increasing the feedforward gain, thus speeding up the steering wheel response. When the angle difference is large, the feedforward compensation gain is smaller, and the feedforward compensation effect is weaker, which can avoid response overshoot.
[0087] Step S210: Determine the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain.
[0088] In this embodiment, the limited target steering angle change rate can be multiplied by the feedforward gain to obtain the feedforward compensated steering angle velocity. Since obtaining the target steering angle change rate by differentiation introduces high-frequency noise, the limited target steering angle change rate can also be multiplied by the feedforward gain, and the resulting product can be filtered to obtain a smoother feedforward compensated steering angle velocity.
[0089] like Figure 3 As shown, the target steering wheel angle in the steering wheel angle request sent by the ADU For CAN signal message period T S The derivative is obtained to determine the rate of change of the target steering wheel angle. This rate of change is then constrained using vehicle speed to obtain the constrained rate of change. The TAS sensor can acquire the actual steering wheel angle θ and, based on the target steering wheel angle... The absolute value of the difference between the target steering angle and the actual steering wheel angle θ determines the feedforward gain. Multiplying the limited target steering wheel angle change rate by the feedforward gain and then performing a low-pass filter yields the feedforward compensated steering angular velocity.
[0090] In step S212, the difference between the sum of the target steering wheel angular velocity and the feedforward compensation angular velocity and the actual steering wheel angular velocity is input into the second PID controller to obtain the target output torque.
[0091] Adding the feedforward compensated steering angular velocity to the target steering wheel angular velocity, and then calculating the difference between this and the actual steering wheel angular velocity, increases the magnitude of this difference. This increases the input to the second PID controller, thus increasing its output and consequently the target output torque. Therefore, controlling the steering wheel rotation using the target output torque improves the response speed.
[0092] See Figure 4 and Figure 5The figures show the ramp input response curves with and without the target angular velocity feedforward compensation algorithm enabled, respectively. It can be seen that with the target angular velocity feedforward compensation algorithm enabled, the fully redundant R-EPS can respond quickly to the target steering wheel angle. See also... Figure 6 and Figure 7 The figures show the sinusoidal input response curves with and without the target angular velocity feedforward compensation algorithm enabled. It can be seen that with the target angular velocity feedforward compensation algorithm enabled, the fully redundant R-EPS can also respond quickly to the target steering wheel angle. Furthermore, the R-EPS response phase delay is reduced, and the following amplitude error is decreased.
[0093] In this embodiment, when the ADU sends the target steering wheel angle to the fully redundant R-EPS and requests a rapid response, a target steering angle velocity feedforward compensation algorithm can be used to calculate the feedforward compensation steering angle velocity based on the vehicle speed, the target steering wheel angle, and the actual steering wheel angle. Compensating the target steering wheel angle velocity with the feedforward compensation steering angle velocity solves the problem of insufficient response speed in the fully redundant R-EPS, and also addresses the issues of large response phase delay and significant amplitude error when using sinusoidal input.
[0094] In autonomous driving mode, due to the inertia of the steering wheel and column, and the connection between the pinion and column via a torsion bar, a certain degree of resistance and external interference is introduced into the steering wheel angle closed-loop control system. Specifically, the inertia of the steering wheel and column causes deformation of the TAS sensor torsion bar, introducing oscillation interference and deteriorating the dynamic stability of the response process. When the steering wheel responds quickly to the steering wheel angle request sent by the ADU, excessive overshoot and callback can occur, resulting in a prolonged time to reach steady state. Specifically, when the ADU controls the steering wheel to accelerate or decelerate as it approaches the target steering angle, a large steering wheel torque is generated. This torque leads to a longer response delay and introduces overshoot and angle fluctuations, weakening dynamic response performance. Figure 8 As shown, the inertial torque of the steering wheel when it is rotated when the target steering angle is 40° causes fluctuations in the actual steering angle. Based on this, embodiments of this application also introduce a nonlinear damping control algorithm to optimize the closed-loop control performance of the steering wheel angle.
[0095] See Figure 9 , Figure 9 This is another flowchart illustrating the steering wheel angle closed-loop control performance optimization method in this application. Figure 2 In addition to the above embodiments, the following steps are also included:
[0096] Step S902: When the rate of change of the target steering wheel angle meets the preset conditions, the nonlinear damping control coefficient K1 is set to 1; when the rate of change of the target steering wheel angle does not meet the preset conditions, the nonlinear damping control coefficient K1 is set to 0.
[0097] The nonlinear damping control coefficient K1 is used to control whether the nonlinear damping control algorithm is activated. When the rate of change of the target steering angle meets the preset conditions, the nonlinear damping control coefficient K1 is set to 1, indicating that the nonlinear damping control algorithm is activated; otherwise, the nonlinear damping control coefficient K1 is set to 0, indicating that the nonlinear damping control algorithm is not activated.
[0098] Optionally, the method for determining whether the rate of change of the target steering wheel angle meets the preset conditions is as follows:
[0099] If the target steering angle changes at a rate of 0 for a duration greater than or equal to a preset time threshold, then the target steering angle change rate is determined to meet the preset condition. If the target steering angle change rate is not 0, or if the target steering angle change rate is 0 but the duration is less than the preset time threshold, then the target steering angle change rate is determined not to meet the preset condition. In other words, when the target steering angle remains unchanged for a relatively long period (e.g., around 100ms), the nonlinear damping control algorithm is activated; otherwise, the nonlinear damping control algorithm is not activated.
[0100] Step S904: When the rotational speed of the motor rotor is less than or equal to the preset speed threshold, the rotational coefficient Ms of the motor rotor is set to 0; when the rotational speed of the motor rotor is greater than the preset speed threshold, the rotational coefficient Ms of the motor rotor is set according to the rotational speed of the motor rotor.
[0101] A nonlinear dead-zone module can be set for the motor rotor rotation coefficient Ms. When the motor rotor speed is low, the rotation coefficient Ms can be set to 0. When the motor rotor speed is high, the rotation coefficient Ms is set according to the motor rotor speed, meaning the rotation coefficient Ms is not 0. The higher the motor rotor speed, the more nonlinear damping torque is needed; therefore, the motor rotor rotation coefficient Ms is positively correlated with the rotor speed.
[0102] Step S906: Set the vehicle speed coefficient Vs according to the vehicle speed of the autonomous vehicle, wherein the vehicle speed coefficient Vs is proportional to the vehicle speed.
[0103] The nonlinear damping torque can also be adjusted according to different vehicle speeds. The higher the vehicle speed, the greater the nonlinear damping torque.
[0104] Step S908: Obtain the deformation angle of the torque angle sensor, resolve the deformation angle into the steering torque of the steering wheel, and set the steering wheel hand torque coefficient Tp according to the steering torque of the steering wheel.
[0105] In autonomous driving mode, as the ADU controls the steering wheel angle to follow the target steering wheel angle, the inertia of the steering column and steering wheel causes deformation of the torsion bar in the TAS sensor. Therefore, the torsion bar deformation angle signal can be detected and sent to the R-EPS ECU via the SENT signal transmission protocol. The R-EPS ECU interprets this signal as steering torque. The direction of the steering torque is opposite to the direction of the target output torque. The steering wheel hand torque coefficient Tp can be set based on the steering torque, and Tp is directly proportional to the steering torque.
[0106] Step S910: Multiply the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, and the steering wheel hand torque coefficient Tp, and process the product using the nonlinear damping gain Kg to obtain the nonlinear damping control torque, so that the nonlinear damping control torque is within the preset compensation torque range.
[0107] See Figure 10 , Figure 10 This is a schematic diagram of a nonlinear damping algorithm in an embodiment of this application. The nonlinear damping control torque is obtained by multiplying the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, the steering wheel torque coefficient Tp, and the nonlinear damping gain Kg. The direction of the nonlinear damping control torque is opposite to the direction of the target output torque.
[0108] The nonlinear damping gain Kg is a preset fixed value used to adjust the final nonlinear damping control torque. For example, if the nonlinear damping control coefficient K1 is 1, the motor rotor rotation coefficient Ms is 4000, the vehicle speed coefficient Vs is 100, the steering wheel hand torque coefficient Tp is 200, the nonlinear damping gain Kg is 0.00000002, and the nonlinear damping control torque = 1 × 4000 × 100 × 200 × 0.00000002 = 1.6 Nm.
[0109] Step S912: The target output torque is superimposed with the nonlinear damping control torque to obtain the final output torque.
[0110] Figure 11 This is a schematic diagram of a steering wheel angle closed-loop control performance optimization method in an embodiment of this application. The target steering wheel angular velocity is obtained through angle closed-loop calculation. The feedforward compensation angular velocity is obtained through the target angular velocity feedforward compensation algorithm. Target angular velocity of the steering wheel With feedforward compensation angular velocity Add them together, and then add them to the actual angular velocity of the steering wheel. Subtract the absolute values of the two values, and input the difference into the PID controller to obtain the target output torque T. b The nonlinear damping control torque T is obtained using a nonlinear damping control algorithm. d Due to the damping control torque T d Direction and target output torque T b In the opposite direction, the target output torque T b With nonlinear damping control torque T d By superimposing these values, the final output torque T is obtained. aim .
[0111] The steering wheel angle closed-loop control performance optimization method of this application embodiment activates a nonlinear damping control algorithm when the target steering angle change rate meets a preset condition. When the rotational speed of the motor rotor is greater than a preset speed threshold, a nonlinear damping torque is superimposed to reduce response overshoot and response angle fluctuation, enabling the steering wheel angle following control to quickly and smoothly track the target steering wheel angle command sent by the ADU. When the rotational speed of the motor rotor is less than or equal to the preset speed threshold, the nonlinear damping control torque is 0, the system damping is weak, and it can still respond to the target steering wheel angle at a relatively fast speed. After superimposing the nonlinear damping control algorithm, the steering wheel angle following process is both fast and stable, and the system has good dynamic performance.
[0112] It should be noted that although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.
[0113] Corresponding to the above method embodiments, this application also provides a steering wheel angle closed-loop control performance optimization device, see [link to relevant documentation]. Figure 12 The steering wheel angle closed-loop control performance optimization device 1200 includes:
[0114] The target steering angle velocity determination module 1202 is used to acquire the target steering angle and the actual steering angle of the steering wheel in real time after the autonomous vehicle enters the autonomous driving mode, and input the difference between the target steering angle and the actual steering angle into the first PID controller to obtain the target steering angle velocity of the steering wheel.
[0115] The actual angular velocity determination module 1204 is used to acquire the rotation angle and rotation direction of the motor rotor in real time, and determine the actual angular velocity of the steering wheel based on the rotation angle and rotation direction of the motor rotor and the transmission ratio between the steering wheel and the motor.
[0116] The target steering angle change rate determination module 1206 is used to differentiate the target steering angle with respect to the signal period, determine the target steering angle change rate, and use the vehicle speed of the autonomous vehicle to limit the target steering angle change rate to obtain the limited target steering angle change rate.
[0117] The feedforward gain determination module 1208 is used to determine the feedforward gain based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein, the feedforward gain is inversely correlated with the absolute value.
[0118] The feedforward compensation angular velocity determination module 1210 is used to determine the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain.
[0119] The target output torque determination module 1212 is used to input the difference between the sum of the target steering wheel angular velocity and the feedforward compensation angular velocity and the actual steering wheel angular velocity into the second PID controller to obtain the target output torque.
[0120] Optionally, the steering wheel angle closed-loop control performance optimization device 1200 also includes:
[0121] The nonlinear damping control coefficient setting module is used to set the nonlinear damping control coefficient K1 to 1 when the rate of change of the target steering angle meets the preset conditions, and to set the nonlinear damping control coefficient K1 to 0 when the rate of change of the target steering angle does not meet the preset conditions.
[0122] The motor rotor rotation coefficient setting module is used to set the motor rotor rotation coefficient Ms to 0 when the rotation speed of the motor rotor is less than or equal to a preset speed threshold; and to set the motor rotor rotation coefficient Ms according to the rotation speed of the motor rotor when the rotation speed of the motor rotor is greater than the preset speed threshold; wherein, the motor rotor rotation coefficient Ms is positively correlated with the rotation speed of the rotor.
[0123] The vehicle speed coefficient setting module is used to set the vehicle speed coefficient Vs according to the vehicle speed of the autonomous vehicle, wherein the vehicle speed coefficient Vs is proportional to the vehicle speed.
[0124] The steering wheel hand torque coefficient setting module is used to obtain the deformation angle of the torque angle sensor, resolve the deformation angle into the steering torque of the steering wheel, and set the steering wheel hand torque coefficient Tp according to the steering torque of the steering wheel. The steering wheel hand torque coefficient Tp is proportional to the steering torque of the steering wheel.
[0125] The nonlinear damping control torque determination module is used to multiply the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, and the steering wheel hand torque coefficient Tp, and process the obtained product using the nonlinear damping gain Kg to obtain the nonlinear damping control torque, so that the nonlinear damping control torque is within the preset compensation torque range.
[0126] The final output torque determination module is used to superimpose the target output torque with the nonlinear damping control torque to obtain the final output torque.
[0127] Optionally, the target steering angle change rate determination module 1206 is used to differentiate the target steering angle with respect to the signal period to determine the target steering angle change rate, and to determine a target steering angle change rate limit value based on the vehicle speed of the autonomous vehicle, wherein the target steering angle change rate limit value is inversely proportional to the vehicle speed; when the target steering angle change rate is greater than the target steering angle change rate limit value, the target steering angle change rate is set to the target steering angle change rate limit value to obtain the limited target steering angle change rate; when the target steering angle change rate is less than or equal to the target steering angle change rate limit value, no processing is performed.
[0128] Optionally, the feedforward compensation angular velocity determination module 1208 is specifically used to multiply the limited target steering wheel angle change rate with the feedforward gain, and filter the resulting product to obtain the feedforward compensation angular velocity.
[0129] Optionally, the target steering angle change rate determination module 1206 is specifically used to determine the target steering angle change rate by differentiating the target steering angle with respect to the signal period if the absolute value of the target steering angle is less than or equal to a preset steering angle threshold, and the slope of the ramp input is greater than a preset slope threshold or the frequency of the sine input is greater than a preset frequency. Then, the target steering angle change rate is limited by the speed of the autonomous vehicle to obtain the limited target steering angle change rate.
[0130] Optionally, the actual angular velocity determination module 1204 is specifically used to acquire the rotation angle and rotation direction of the motor rotor in real time, determine the rotation speed of the motor rotor based on the rotation angle and rotation direction of the motor rotor, and convert the rotation angular velocity of the motor rotor into the actual angular velocity of the steering wheel based on the transmission ratio between the steering wheel and the motor.
[0131] Optionally, the steering wheel angle closed-loop control performance optimization device 1200 also includes:
[0132] The judgment module is used to determine that the steering wheel target angle change rate meets the preset condition when the steering wheel target angle change rate is 0 and the duration is greater than or equal to the preset time threshold; and to determine that the steering wheel target angle change rate does not meet the preset condition when the steering wheel target angle change rate is not 0, or the steering wheel target angle change rate is 0 but the duration is less than the preset time threshold.
[0133] The specific details of each module or unit in the above-mentioned device have been described in detail in the corresponding methods, so they will not be repeated here.
[0134] It should be noted that although several modules or units for the device used to perform actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to the embodiments of this application, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.
[0135] This application also provides an electronic device, including: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to execute the steering wheel angle closed-loop control performance optimization method described in this example embodiment.
[0136] Reference Figure 13 , Figure 13 This is a schematic diagram of the structure of an electronic device in an embodiment of this application. The specific embodiments of this application do not limit the specific implementation of the electronic device.
[0137] like Figure 13 As shown, the electronic device may include: a processor 1302, a communication interface 1304, a memory 1306, and a communication bus 1308.
[0138] The processor 1302, communication interface 1304, and memory 1306 communicate with each other via communication bus 1308.
[0139] Communication interface 1304 is used to communicate with other electronic devices or servers.
[0140] The processor 1302 is used to execute program 1310, specifically the relevant steps in the above method embodiments.
[0141] Specifically, program 1310 may include program code that includes computer operation instructions.
[0142] The processor 1302 may be a central processing unit, a specific integrated circuit, or one or more integrated circuits configured to implement the embodiments of this application. The smart device includes one or more processors, which may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.
[0143] Memory 1306 is used to store program 1310. Memory 1306 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.
[0144] Specifically, program 1310 can be used to cause processor 1302 to execute the steps in the above-described embodiment of the steering wheel angle closed-loop control performance optimization method.
[0145] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the devices and modules described above can be referred to the corresponding process descriptions in the foregoing method embodiments, and will not be repeated here.
[0146] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the above-described steering wheel angle closed-loop control performance optimization method.
[0147] It should be noted that the computer-readable storage medium shown in this application can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory, read-only memory, erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this application, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer-readable storage medium can be transmitted using any suitable medium, including but not limited to: wireless, wire, optical fiber, radio frequency, etc., or any suitable combination thereof.
[0148] In this embodiment of the application, a computer program product is also provided, which, when run on a computer, causes the computer to execute the above-described steering wheel angle closed-loop control performance optimization method.
[0149] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0150] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for optimizing the closed-loop control performance of steering wheel angle in an autonomous vehicle, characterized in that, include: After the autonomous vehicle enters the autonomous driving mode, the target steering angle and the actual steering angle of the steering wheel are acquired in real time. The difference between the target steering angle and the actual steering angle is input into the first PID controller to obtain the target steering angle speed. The rotation angle and direction of the motor rotor are acquired in real time. Based on the rotation angle and direction of the motor rotor and the transmission ratio between the steering wheel and the motor, the actual angular velocity of the steering wheel is determined. The rate of change of the target steering wheel angle is determined by differentiating the target steering wheel angle with respect to the signal period, and the rate of change of the target steering wheel angle is limited by the speed of the autonomous vehicle to obtain the limited rate of change of the target steering wheel angle. The feedforward gain is determined based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein the feedforward gain is inversely correlated with the absolute value. The feedforward compensation angular velocity is determined based on the restricted target steering wheel angle change rate and the feedforward gain. The difference between the sum of the target steering wheel angular velocity and the feedforward compensated steering angular velocity and the actual steering wheel angular velocity is input into the second PID controller to obtain the target output torque.
2. The method according to claim 1, characterized in that, The method further includes: When the rate of change of the target steering wheel angle meets the preset condition, the nonlinear damping control coefficient K1 is set to 1; when the rate of change of the target steering wheel angle does not meet the preset condition, the nonlinear damping control coefficient K1 is set to 0. When the rotational speed of the motor rotor is less than or equal to the preset speed threshold, the motor rotor rotation coefficient Ms is set to 0; when the rotational speed of the motor rotor is greater than the preset speed threshold, the motor rotor rotation coefficient Ms is set according to the rotational speed of the motor rotor; wherein, the motor rotor rotation coefficient Ms is positively correlated with the rotational speed of the rotor. The vehicle speed coefficient Vs is set according to the vehicle speed of the autonomous vehicle, where the vehicle speed coefficient Vs is proportional to the vehicle speed; The deformation angle of the torque angle sensor is obtained, and the deformation angle is analyzed into the steering torque of the steering wheel. The steering torque coefficient Tp is set according to the steering torque of the steering wheel, wherein the steering torque coefficient Tp is proportional to the steering torque of the steering wheel. Multiply the nonlinear damping control coefficient K1, the motor rotor rotation coefficient Ms, the vehicle speed coefficient Vs, and the steering wheel hand torque coefficient Tp, and process the product using the nonlinear damping gain Kg to obtain the nonlinear damping control torque, so that the nonlinear damping control torque is within the preset compensation torque range. The target output torque is superimposed with the nonlinear damping control torque to obtain the final output torque.
3. The method according to claim 1, characterized in that, The process of limiting the rate of change of the steering wheel target angle using the speed of the autonomous vehicle includes: Based on the speed of the autonomous vehicle, a target turning angle change rate limit is determined, wherein the target turning angle change rate limit is inversely proportional to the vehicle speed; When the target steering angle change rate is greater than the target steering angle change rate limit, the target steering angle change rate is set to the target steering angle change rate limit. No action is taken when the target steering angle change rate is less than or equal to the target steering angle change rate limit.
4. The method according to claim 1, characterized in that, The step of determining the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain includes: The restricted target steering angle change rate is multiplied by the feedforward gain, and the resulting product is filtered to obtain the feedforward compensated steering angle velocity.
5. The method according to claim 1, characterized in that, The step of differentiating the target steering angle of the steering wheel with respect to the signal period to determine the rate of change of the target steering angle includes: If the absolute value of the target steering angle is less than or equal to a preset steering angle threshold, and the slope of the ramp input is greater than a preset slope threshold or the frequency of the sine input is greater than a preset frequency, the target steering angle is differentiated with respect to the signal period to determine the rate of change of the target steering angle.
6. The method according to claim 1, characterized in that, The determination of the actual angular velocity of the steering wheel based on the rotation angle and direction of the motor rotor, as well as the transmission ratio between the steering wheel and the motor, includes: Determine the rotational speed of the motor rotor based on its rotational angle and direction. Based on the transmission ratio between the steering wheel and the motor, the rotational angular velocity of the motor rotor is converted into the actual angular velocity of the steering wheel.
7. The method according to claim 2, characterized in that, The method for determining whether the rate of change of the target steering wheel angle meets the preset condition is as follows: When the rate of change of the target steering wheel angle is 0 and the duration is greater than or equal to a preset time threshold, it is determined that the rate of change of the target steering wheel angle meets the preset condition. If the target steering angle change rate is not 0, or if the target steering angle change rate is 0 but the duration is less than a preset time threshold, then it is determined that the target steering angle change rate does not meet the preset condition.
8. A device for optimizing the closed-loop control performance of steering wheel angle in an autonomous vehicle, characterized in that, include: The target steering angle velocity determination module is used to acquire the target steering angle and the actual steering angle of the steering wheel in real time after the autonomous vehicle enters the autonomous driving mode, and input the difference between the target steering angle and the actual steering angle into the first PID controller to obtain the target steering angle velocity. The actual angular velocity determination module is used to acquire the rotation angle and rotation direction of the motor rotor in real time, and determine the actual angular velocity of the steering wheel based on the rotation angle and rotation direction of the motor rotor and the transmission ratio between the steering wheel and the motor. The module for determining the rate of change of the target steering angle after limitation is used to differentiate the target steering angle of the steering wheel with respect to the signal period, determine the rate of change of the target steering angle of the steering wheel, and use the speed of the autonomous vehicle to limit the rate of change of the target steering angle of the steering wheel to obtain the rate of change of the target steering angle of the steering wheel after limitation. The feedforward gain determination module is used to determine the feedforward gain based on the absolute value of the difference between the target steering wheel angle and the actual steering wheel angle; wherein the feedforward gain is inversely correlated with the absolute value. The feedforward compensation angular velocity determination module is used to determine the feedforward compensation angular velocity based on the limited target steering wheel angle change rate and the feedforward gain. The target output torque determination module is used to input the difference between the sum of the target steering wheel angular velocity and the feedforward compensation angular velocity and the actual steering wheel angular velocity into the second PID controller to obtain the target output torque.
9. An electronic device, characterized in that, include: A processor for executing a computer program stored in a memory, wherein the computer program, when executed by the processor, implements the method of any one of claims 1-7.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-7.