Control method and controller for vehicle steering system

Abstract

A control method and controller for a vehicle steering system are disclosed. The method includes: obtaining a first steering wheel angle and a first yaw rate of a target vehicle during operation; determining a theoretical system response value based on the target vehicle's system transfer function and the first steering wheel angle, and fusing the first yaw rate and the theoretical system response value into a second yaw rate; determining an error value based on the target yaw rate and the second yaw rate, and inputting the error value into a position closed-loop PID controller to obtain an angle increment; and determining whether the target vehicle's steering wheel motor supports a speed closed-loop PID controller. If not, the angle increment is output to the steering wheel motor; if so, the angle increment is output to the speed closed-loop PID controller to obtain a speed command, which is then output to the steering wheel motor. Furthermore, the parameters in the closed-loop PID controller can be automatically calibrated. This method can improve debugging efficiency and vehicle steering system performance.

Description

Technical Field

[0001] The present application relates to the technical field of vehicle steering control, and in particular to a control method and controller for a vehicle steering system. Background Art

[0002] The vehicle's large mass and resulting moment of inertia make precise control and positioning difficult during steering and centering maneuvers. Furthermore, because different vehicle steering systems control vastly different physical quantities, it's difficult to directly transfer control methods from one steering system to another.

[0003] Therefore, there is an urgent need for an efficient control method for a vehicle steering system to improve the control capability of the vehicle steering system. Summary of the Invention

[0004] In view of this, the present application discloses a control method and a controller for a vehicle steering system to improve the control capability of the vehicle steering system.

[0005] In one aspect, the present application discloses a control method for a vehicle steering system, comprising: obtaining a first steering wheel angle of a target vehicle during operation and a first yaw angular velocity matching the first steering wheel angle; determining a theoretical system response value based on a system transfer function of the target vehicle and the first steering wheel angle, inputting the first yaw angular velocity and the theoretical system response value into a fusion device to obtain a second yaw angular velocity; determining an error value based on the target yaw angular velocity and the second yaw angular velocity, and inputting the error value into a position closed-loop PID controller to obtain an angle increment; judging whether the steering wheel motor of the target vehicle supports a speed closed-loop PID controller, and if not, outputting the angle increment to the steering wheel motor; and if so, outputting the angle increment to the speed closed-loop PID controller to obtain a speed command, and outputting the speed command to the steering wheel motor.

[0006] Optionally, the steering wheel motor receives an angle increment or a speed command and generates a compensation response value based on a system transfer function; the method also includes: inputting the compensation response value, the first yaw angular velocity and the theoretical system response value into a fusion device to obtain a second yaw angular velocity.

[0007] Optionally, the fuser is a Kalman filter, an extended Kalman filter or an unscented Kalman filter.

[0008] Optionally, obtaining a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle when the target vehicle is running includes: installing an encoder on a steering wheel motor; and recording encoder data when the target vehicle is running to obtain the first steering wheel angle.

[0009] Optionally, obtaining a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle when the target vehicle is running includes: installing an inertial sensor on the target vehicle; recording data from the inertial sensor when the target vehicle is running to obtain the first yaw angular velocity; or installing an antenna for a global navigation satellite system on the target vehicle; receiving satellite signals through the antenna when the target vehicle is running, and processing the satellite signals into the first yaw angular velocity.

[0010] Optionally, the control method for a vehicle steering system further includes: constructing a system transfer function of a target vehicle; the system transfer function includes a proportional link and a time-delay link, and the proportional coefficient of the proportional link is determined by a first proportional constant and a second proportional constant; wherein the first proportional constant is the quotient of the front wheel angle of the target vehicle and the first steering wheel angle, and the second proportional constant is the quotient of the vehicle speed of the target vehicle and the wheelbase of the front and rear axles of the target vehicle.

[0011] Optionally, the control method for a vehicle steering system further includes: calibrating parameters in a position closed-loop PID controller and a speed closed-loop PID controller, the parameters including a proportional gain parameter and a differential gain parameter.

[0012] Optionally, calibrating the parameters in the position closed-loop PID controller and the speed closed-loop PID controller includes: initializing a second steering wheel angle, the second steering wheel angle being the maximum angle of the initial steering wheel of the target vehicle; based on the second steering wheel angle, controlling the target vehicle to rotate during operation, and recording a third yaw angular velocity that matches the second steering wheel angle; judging whether the third yaw angular velocity is within a preset range; if not, correcting the second steering wheel angle using the target yaw angular velocity and the maximum value in the preset range until the third yaw angular velocity is within the preset range; if so, obtaining the corresponding maximum angle, minimum angle, maximum yaw angular velocity and minimum yaw angular velocity using the second steering wheel angle, and determining the parameters in the position closed-loop PID controller and the speed closed-loop PID controller.

[0013] Optionally, the differential gain parameter and the proportional gain parameter are in a multiple relationship.

[0014] In a second aspect, the present application further discloses a controller for a target vehicle, which executes the control method for a vehicle steering system disclosed in the first aspect above.

[0015] In summary, the control method and controller for a vehicle steering system disclosed in this application have at least the following beneficial effects:

[0016] 1. This solution uses the yaw rate as the target value, making it widely adaptable to different steering modes;

[0017] 2. The variable gain + cascade PID control method improves the control effect of the nonlinear steering system and realizes the conversion control from steering wheel angle to motor speed;

[0018] 3. This invention uses the values ​​of inertial sensors and encoders, taking advantage of the characteristics of the inertial sensor's precise instantaneous absolute value and the encoder's precise, stable relative value without response delay, and using the fused value as feedback to improve control accuracy and stability.

[0019] 4. For the parameters required in the control system, this solution has designed a set of automatic calibration acquisition methods to enable it to adapt to a wide range of vehicle models more quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following is a brief introduction to the drawings used in describing the embodiments of this application.

[0021] Figure 1 An example diagram of a control method for a vehicle steering system provided by an embodiment of the present application is shown.

[0022] Figure 2 An example diagram of another control method for a vehicle steering system provided by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the specific implementation methods of the present application will be described below with reference to the accompanying drawings. The drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative work. Adjustments and improvements made without departing from the concept of the present application are all within the scope of protection of the present application.

[0024] To simplify the drawings, only the parts related to the corresponding embodiments are schematically shown in each figure. They do not represent the actual structure of the product. In addition, to simplify the drawings and facilitate understanding, in some figures, only a portion of the components with the same structure or function are schematically depicted. In reality, more or fewer components with the same structure or function may exist.

[0025] In this application, unless otherwise expressly specified and limited, ordinal numbers such as "first", "second", etc. are only used to distinguish and describe associated objects, and cannot be understood as indicating or implying the relative importance or order between associated objects; in addition, they do not represent the number of associated objects. "Multiple" includes two or more, and other quantifiers are similar. " / " is used to describe the relationship between associated objects, which indicates the "or" relationship between associated objects. "And / or" is used to describe the relationship between associated objects, which includes any combination relationship between associated objects, for example, "a and / or b" includes: "alone a", "alone b", or "a and b". "One or more" or "at least one" in multiple objects refers to any object or any combination of multiple objects, for example, "one or more of a1, a2, a3" or "at least one of a1, a2, a3" includes: "alone a1", "alone a2", "alone a3", "a1 and a2", "a1 and a3", "a2 and a3", or "a1, a2 and a3".

[0026] Heavy or heavily loaded mobile machinery (such as large vehicles) has a large moment of inertia, making it difficult to effectively improve the response speed of steering and self-centering processes. Furthermore, the numerous nonlinearities in the mechanical transmission process lead to significant system response lag. These factors, combined, make precise steering control challenging.

[0027] The physical quantities controlled by different vehicle steering systems vary significantly. For example, in an Ackerman-steering vehicle, steering wheel movement drives the front wheels, while in a four-wheel-steering vehicle, both front and rear wheels rotate simultaneously. Articulated vehicles achieve directional changes by rotating the hinge point, while differential vehicles steer by varying the differential speed of the left and right wheels. These different vehicle types have significantly different motion models.

[0028] Current common solutions achieve steering control by controlling the movement of actuators, such as the vehicle's front wheel angle. This approach makes the algorithm incompatible with vehicle configurations. Even with the same steering configuration, control parameters may not be universal when applied to different vehicles. This requires re-tuning the control algorithm each time, making it difficult to quickly reuse.

[0029] Therefore, one of the concepts of this application is to control the yaw rate so that it can be widely applied to different steering forms. Commonly used sensors in existing steering control systems include encoders and inertial sensors (IMUs). The encoder can obtain the steering wheel angle, while the IMU can obtain the motion state of the vehicle body. However, the encoder readings may offset (error accumulation) over time, and the IMU may introduce large noise due to vehicle vibration. By fusing feedback data from multiple sensors, the robustness of the system is improved.

[0030] In addition, the debugging of existing control parameters usually relies on manual experience, and the manual debugging process is complicated and time-consuming. To this end, this application designs a set of explainable automatic calibration processes that can automatically debug and calibrate the required parameters, achieving faster and more convenient promotion and application.

[0031] The following description is given with reference to the accompanying drawings.

[0032] Figure 1 An example diagram of a control method for a vehicle steering system provided by an embodiment of the present application is shown. Figure 1 , a control method for a vehicle steering system includes:

[0033] S100, obtaining a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle of the target vehicle during operation;

[0034] S200, determining a theoretical system response value based on a system transfer function of the target vehicle and a first steering wheel angle, inputting the first yaw rate and the theoretical system response value into a fuser to obtain a second yaw rate;

[0035] S300, determining an error value based on the target yaw rate and the second yaw rate, and inputting the error value into a position closed-loop PID controller to obtain a rotation angle increment;

[0036] S400, determining whether the steering wheel motor of the target vehicle supports a speed closed-loop PID controller. If not, outputting the angle increment to the steering wheel motor. If supported, outputting the angle increment to the speed closed-loop PID controller to obtain a speed command, and outputting the speed command to the steering wheel motor.

[0037] The above method can be applied to autonomous driving scenarios, such as autonomous driving of mobile machinery, to achieve walking control of the mobile machinery.

[0038] Yaw rate describes the speed at which a vehicle rotates about its vertical axis and reflects its overall steering dynamics when turning or changing lanes. This quantity is closely related to the vehicle's motion state and is independent of the specific steering mechanism (such as the front wheels, rear wheels, differential, or hinge point). Whether the vehicle achieves directional changes through front wheel rotation, four-wheel steering, differential control, or articulated steering, the ultimate manifestation is a change in yaw rate. By controlling yaw rate, the vehicle's steering behavior can be uniformly controlled without relying on the specific physical structure of the actuators. When controlling the entire vehicle, the vehicle body can be considered a rigid body. Since the vehicle does not have independent lateral motion, the vehicle motion can be decomposed into longitudinal and lateral motion. Current common control algorithms achieve yaw motion control by controlling indirect quantities such as the vehicle's front wheel angle. This method, however, directly controls the yaw quantity, that is, the vehicle's yaw rate. Regardless of whether the vehicle employs Ackerman steering, rear-wheel steering, differential steering, or multi-axle steering, its body motion can be abstracted into longitudinal and lateral motion. In this way, the control method of the present application can adapt to different steering forms.

[0039] In vehicles, some motors do not support position loop (i.e., position closed-loop PID controller) control, and only support speed loop (i.e., speed closed-loop PID controller). The control method of this application can enable the motor to support both speed loop and position loop control. Position loop control and speed loop control are essentially two nested control loops: the goal of the position loop is to control the position of the motor (such as the angle of the steering wheel), that is, the motor rotates to a certain target angle; and the goal of the speed loop is to control the speed of the motor so that the motor rotates at a specified speed. The output of the position loop can be a target speed, that is, telling the motor at what speed to rotate in order to reach a predetermined angle. Therefore, the speed loop can actually be used to assist the position loop to control how the motor reaches the target position at an appropriate speed.

[0040] For motors that don't support a position loop (only support speed control), position control can be achieved indirectly by adjusting the speed loop. Although the motor cannot be directly controlled to a specific position, the motor's rotation amplitude can be controlled by continuously adjusting the motor speed. For example, the system can use the speed loop to control the motor speed based on the difference between the current and target positions, gradually approaching the target position. As the motor approaches the target position, the speed is gradually reduced so that the motor can smoothly stop at the target position. The core control objective of this solution is yaw rate, which can be achieved by adjusting the motor speed. Therefore, whether the motor supports a position loop or only a speed loop, as long as the motor speed can be controlled, the vehicle's yaw rate can be controlled by adjusting the speed. For motors that don't support a position loop, the solution calculates the difference between the target and current positions, converts this difference into a target speed, and inputs it into the speed loop. The motor then adjusts the steering wheel according to the target speed to achieve the target position.

[0041] In the above method, a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle are first obtained while the target vehicle is in motion. In some embodiments of the present application, an encoder can be installed on the steering wheel motor, and encoder data can be recorded while the target vehicle is in motion to obtain the first steering wheel angle. For example, the encoder can be subjected to median compensation. Over time, the encoder reading may experience zero-point drift (i.e., drift of the initial zero point) or accumulated error, causing it to fail to accurately reflect the actual steering wheel angle. This error may be caused by temperature changes, mechanical wear, installation errors, or external interference. Median compensation is a correction technique used to eliminate the effects of encoder zero-point drift or accumulated error. Its basic principle is to record and analyze the encoder's behavior over a certain period of time to determine the extent to which its actual "median" (i.e., theoretical zero point) has shifted. Compensation is then applied to the measured value to restore the true steering wheel angle. In terms of its implementation process, the system first records the steering wheel motion data over a certain period of time and uses mathematical methods (such as filtering or averaging) to determine the offset of the encoder reading. This offset is called the center offset, and it represents the deviation of the encoder's measured zero point from the true zero point. The system then corrects each encoder reading to compensate for this center offset, making each measured angle closer to the true steering wheel angle.

[0042] In some embodiments of the present application, an inertial sensor can be installed on the target vehicle, and the data of the inertial sensor can be recorded while the target vehicle is running to obtain the first yaw rate; or, an antenna for a global navigation satellite system can be installed on the target vehicle, and satellite signals can be received through the antenna while the target vehicle is running, and the satellite signals can be processed into the first yaw rate. In other words, the first yaw rate of the target vehicle while running can be obtained by an inertial sensor or an antenna for a global navigation satellite system (GNSS). In addition, there is a corresponding relationship between the first yaw rate and the first steering wheel angle, that is, when the steering wheel angle of the target vehicle is the above first steering wheel angle, the yaw rate that can be obtained by the IMU or the antenna for GNSS is the above first yaw rate. If the first yaw rate is obtained by using an antenna for GNSS, the first yaw rate can be obtained by calculation based on the heading data obtained by the antenna.

[0043] In some embodiments of the present application, the control method for a vehicle steering system further includes: constructing a system transfer function of a target vehicle; the system transfer function includes a proportional link and a time-delay link, and the proportional coefficient of the proportional link is determined by a first proportional constant and a second proportional constant; wherein the first proportional constant is the quotient of the front wheel angle of the target vehicle and the first steering wheel angle, and the second proportional constant is the quotient of the vehicle speed of the target vehicle and the wheelbase of the front and rear axles of the target vehicle.

[0044] When the target vehicle maintains forward motion (that is, the target vehicle is running), the steering wheel movement will cause the vehicle to yaw. There is a mapping relationship between the steering wheel angle θ and the yaw rate ω: ω = f(θ); where θ is the steering wheel angle and ω is the yaw rate. Taking the Ackerman model as an example, the steering wheel angle θ and the front wheel angle δ are proportional links: δ = k1θ, k1 is the first proportional constant, that is, the first proportional constant is the quotient of the front wheel angle of the target vehicle and the first steering wheel angle. The relationship between the front wheel angle δ and the yaw rate ω based on the kinematic model is as follows: Where V is the vehicle speed and L is the target vehicle's front and rear axle distance. These two terms can be considered constants when in constant motion. When the target vehicle's front wheel angle is small, tanδ is approximately equal to δ, so it can be considered a proportional function. The second proportional constant, k2, equals V / L, meaning it is the quotient of the target vehicle's speed and its front and rear axle distance. From this, we can obtain ω = k2δ and ω = k3θ, where k3 is the proportionality factor of the proportional link, and k3 = k1 * k2. This proves that the yaw rate ω and the steering wheel angle θ are proportional under limited conditions.

[0045] Due to the delay of the steering transmission system and the delay of the rotational inertia response, the steering system can be regarded as a combination of a proportional link and a time-delay link. The system transfer function can be written as: Where τ is the time constant of the link. In some embodiments of the present application, if the steering system is not linear, it can be linearized in stages using a piecewise function, and the calculation formula is as follows: That is to say, the nonlinear system is adjusted to a linear state in each segment through a segmented approach.

[0046] For the target vehicle, the yaw rate is controlled, and the feedback is naturally also yaw rate. The inertial sensor can obtain the current yaw rate of the vehicle body (the GNSS antenna can calculate the target vehicle's yaw rate based on the acquired heading). The value obtained by the inertial sensor is considered the system response plus sensor observation noise, while the steering wheel motor encoder reading is the system input plus the encoder reading zero bias. For example, the actual steering wheel angle can be read using encoder mid-position compensation. Based on this angle value, the system response can be calculated using the aforementioned transfer function. Because this response is obtained through theoretical calculation using the steering wheel angle, it avoids the sensor observation noise and system response delay associated with directly observing the system output. By calculating the steering wheel encoder movement over the previous τ time period, the value obtained through the transfer function calculation can be used to compensate for the delay in directly observing the vehicle body yaw response. This value, combined with the vehicle body yaw rate directly measured by the inertial sensor, serves as the system response measurement. These values ​​are combined in a Kalman filter for observation, resulting in a relatively accurate feedback value for the vehicle body. This value is named the second yaw rate ω. N .

[0047] The above embodiment combines the values ​​of the inertial sensor and the motor encoder, leveraging the advantages of the inertial sensor's precise instantaneous absolute value (but with high noise and vehicle response delay) and the encoder's precise and stable relative value without response delay (but with zero offset). This approach leverages their strengths and compensates for their weaknesses, using the fused value as feedback to improve control accuracy and stability.

[0048] In this application, an error value is determined based on the target yaw rate and the second yaw rate, and the error value is input into a position closed-loop PID controller to obtain a steering angle increment. Subsequently, a determination is made as to whether the target vehicle's steering wheel motor supports a speed closed-loop PID controller. If not, the steering angle increment is output to the steering wheel motor. If so, the steering angle increment is output to the speed closed-loop PID controller to obtain a speed command, which is then output to the steering wheel motor. In some embodiments of this application, the steering wheel motor receives the steering angle increment or speed command and generates a compensation response value based on a system transfer function. The control method further includes inputting the compensation response value, the first yaw rate, and the theoretical system response value into a fusion unit to obtain a second yaw rate. In some embodiments of this application, the fusion unit is a Kalman filter, an extended Kalman filter, or an unscented Kalman filter.

[0049] The target yaw rate issued by the upper control can be called ω T At this time, the error between the target yaw rate and the second yaw rate is: e ω =ω T -ω N , the target action increment (position loop increment pid) at this time is: Among them, k p 、k i and k d For the position closed loop PID controller's proportional, integral, and differential coefficients. For the speed loop control, the speed loop is controlled by connecting one level of PID in series: Among them, k ′ p 、k i ′ and k ′ d are the proportional, integral and differential coefficients of the speed closed-loop PID controller.

[0050] In some embodiments of the present application, for the nonlinear problem of the steering system (mainly the steering wheel virtual position caused by the steering clearance, which is called dead zone in control). ′ ,θ ′ ], the dead zone can be overcome by changing the position loop gain. The calculation formula is as follows: in, is the gain set for the dead zone, and k p dz >k p Similarly, the nonlinearity in the non-dead zone can be applied to the idea of ​​the above piecewise function (refer to the above embodiment), and a piecewise variable gain PID control is set.

[0051] In the above embodiment, the control effect of the nonlinear steering system is improved by the variable gain + cascade PID control method, and the conversion control from the steering wheel angle to the motor speed is realized at the same time.

[0052] Figure 2 An example diagram of another control method for a vehicle steering system provided by an embodiment of the present application is shown. Figure 2 In some embodiments of the present application, the control method for a vehicle steering system further includes:

[0053] S500, calibrating parameters in the position closed-loop PID controller and the speed closed-loop PID controller, the parameters including proportional gain parameters and differential gain parameters.

[0054] For example, please refer to Figure 2 , the calibration methods include:

[0055] S510, initializing a second steering wheel angle, where the second steering wheel angle is the maximum angle of the initial steering wheel of the target vehicle;

[0056] S520, based on the second steering wheel angle, controlling the target vehicle to rotate during operation, and recording a third yaw angular velocity that matches the second steering wheel angle;

[0057] S530 determines whether the third yaw rate is within a preset range. If not, the second steering wheel angle is corrected using the target yaw rate and the maximum value in the preset range until the third yaw rate is within the preset range. If so, the corresponding maximum angle, minimum angle, maximum yaw rate, and minimum yaw rate are obtained using the second steering wheel angle, and parameters for the position closed-loop PID controller and the velocity closed-loop PID controller are determined. In some embodiments of the present application, the differential gain parameter and the proportional gain parameter are in a multiple relationship.

[0058] Automatic parameter calibration includes calibration of position loop control parameters and calibration of speed loop control parameters. First, the calibration program flow can be used to obtain the motor position loop control parameters. The calibration process can be referred to as follows. In the initial state, the target vehicle starts at a stable constant speed. The yaw angular velocity of the target vehicle is directly or indirectly obtained through inertial sensors or antennas for GNSS. By adjusting the steering wheel position, the yaw angular velocity slowly converges to zero, so that the steering wheel returns to the center and the target vehicle is traveling in a straight line. Then set the steering wheel to swing in the form of a periodic function, such as a sine function: Among them, A0 is a constant, that is, the second steering wheel angle, which is the maximum angle of the initial steering wheel of the target vehicle, t is the time to start the movement, l is an arbitrary positive number, and f is the control frequency; thus, the initialization of the second steering wheel angle is completed. In this process, the action of the steering wheel causes the vehicle to swing left and right. At this time, the vehicle yaw rate under the timing is recorded synchronously, that is, based on the second steering wheel angle, the target vehicle is controlled to rotate during operation, and the third yaw rate that matches the second steering wheel angle is recorded. Then, it is determined whether the maximum value of the vehicle yaw rate (that is, the third yaw rate above) in the previous stage is within the preset range. The preset range can be, for example, [1,3]° / s. If not, the target yaw rate and the maximum value in the preset range are used to correct the second steering wheel angle. The calculation formula is as follows: Among them, A ′ 0 is the corrected second steering wheel angle. The above recording and judgment operations are then repeated until the third yaw rate is within the preset range. If the third yaw rate is within the preset range, the target vehicle can be stopped and the next calculation can be performed. This is to use the second steering wheel angle to obtain the corresponding maximum angle, minimum angle, maximum yaw rate, and minimum yaw rate, and determine the parameters of the position closed-loop PID controller and the speed closed-loop PID controller. The calculation formula is as follows. If the vehicle steering system has no backlash, the transmission coefficient can be considered a constant: Otherwise, k should be calculated piecewise: Then, based on the k calculated in the above formula, the control parameters can be calculated through the time series data: Where q represents the number of cycles required to converge to the current error. d With k p The differential gain parameter and the proportional gain parameter are related in multiples: k d =w·k p For example, w is set to 0.2, and k d =0.2k p At this time, k j Get the yaw offset during the full calibration cycle: At this point, the position loop control parameter calibration function is completed.

[0059] After the position loop is calibrated, the speed loop control parameters can be calibrated. This means converting the motor input dimensions to obtain the speed control parameters. The position loop commands are in degrees per second (° / s). For example, if the motor receives a speed command in rpm (rotations per minute), and the motor control frequency is T and the desired period is n, the following formula can be derived: In some embodiments, assuming that the motor control frequency is 20 Hz and the motor is expected to complete the target motion within 2 cycles, the following calculation formula is used: Thus, the automatic calibration of the speed loop parameters is completed.

[0060] Because the control parameters of existing technologies may not be universal for different types of vehicles, or even for vehicles of the same type with different specifications, and the difficulty of using experience-based tuning methods is not conducive to method promotion, in the above embodiment, the automatic calibration method of design parameters can effectively improve the debugging efficiency.

[0061] Based on similar technical concepts, the present application also discloses a controller for a target vehicle, and executes the control method for a vehicle steering system disclosed in the first aspect above. Exemplarily, the controller can be, for example, an electronic control unit (ECU). The ECU is the core of the entire control system, which is responsible for executing the PID control algorithm (position loop and speed loop) and calculating the required motor control parameters, such as kp and kd, based on the feedback signals provided by sensors (such as IMU, GNSS). In addition, the ECU receives sensor data such as vehicle speed, yaw angular velocity, steering wheel angle, etc., and performs real-time calculations and adjustments to ensure that the vehicle can steer according to the set path or target under different steering conditions.

[0062] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments. In addition, the above embodiments can be freely combined as needed.

Claims

1. A control method for a vehicle steering system, characterized in that: include: Acquire a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle when the target vehicle is running; determining a theoretical system response value based on a system transfer function of the target vehicle and the first steering wheel angle, and inputting the first yaw rate and the theoretical system response value into a fuser to obtain a second yaw rate; determining an error value based on the target yaw rate and the second yaw rate, and inputting the error value into a position closed-loop PID controller to obtain a rotation angle increment; determining whether the steering wheel motor of the target vehicle supports a speed closed-loop PID controller; if not, outputting the rotation angle increment to the steering wheel motor; if supported, outputting the rotation angle increment to the speed closed-loop PID controller to obtain a speed command, and outputting the speed command to the steering wheel motor; Calibrate parameters in the position closed-loop PID controller and the speed closed-loop PID controller, wherein the parameters include proportional gain parameters and differential gain parameters; Wherein, the calibration of the parameters in the position closed-loop PID controller and the speed closed-loop PID controller includes: Initializing a second steering wheel angle, where the second steering wheel angle is a maximum angle of an initial steering wheel of the target vehicle; controlling the target vehicle to rotate during operation based on the second steering wheel angle, and recording a third yaw angular velocity that matches the second steering wheel angle; Determining whether the third yaw rate is within a preset interval; if not, correcting the second steering wheel angle using the target yaw rate and a maximum value in the preset interval until the third yaw rate is within the preset interval; and if so, obtaining corresponding maximum angle, minimum angle, maximum yaw rate, and minimum yaw rate using the second steering wheel angle, and determining parameters in the position closed-loop PID controller and the speed closed-loop PID controller.

2. The control method for a vehicle steering system according to claim 1, characterized in that: The steering wheel motor receives the rotation angle increment or the speed command and generates a compensation response value based on the system transfer function; the method further includes: The compensation response value, the first yaw angular velocity, and the theoretical system response value are input into the fuser to obtain the second yaw angular velocity.

3. The control method for a vehicle steering system according to claim 1 or 2, characterized in that: The fuser is a Kalman filter, an extended Kalman filter or an unscented Kalman filter.

4. The control method for a vehicle steering system according to claim 1, characterized in that: The step of obtaining a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle of the target vehicle during operation includes: Installing an encoder on the steering wheel motor; The data of the encoder is recorded while the target vehicle is running to obtain the first steering wheel angle.

5. The control method for a vehicle steering system according to claim 1 or 4, characterized in that: The step of obtaining a first steering wheel angle and a first yaw angular velocity matching the first steering wheel angle of the target vehicle during operation includes: installing an inertial sensor on the target vehicle; Recording data from the inertial sensor while the target vehicle is running to obtain the first yaw angular velocity; or, installing an antenna for a global navigation satellite system on the target vehicle; When the target vehicle is running, a satellite signal is received through the antenna, and the satellite signal is processed into the first yaw angular velocity.

6. The control method for a vehicle steering system according to claim 1, characterized in that: Also includes: Constructing a system transfer function of the target vehicle; The system transfer function includes a proportional link and a time-lag link, and the proportional coefficient of the proportional link is determined by a first proportional constant and a second proportional constant; The first proportional constant is the quotient of the front wheel angle of the target vehicle and the first steering wheel angle, and the second proportional constant is the quotient of the speed of the target vehicle and the wheelbase of the front and rear axles of the target vehicle.

7. The control method for a vehicle steering system according to claim 1, characterized in that: The differential gain parameter is in a multiple relationship with the proportional gain parameter.

8. A controller, characterized in that: The invention is used for a target vehicle and executes the control method for a vehicle steering system according to any one of claims 1 to 7.

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