Electric power steering torque calculation method, system, steering control method, system

Abstract

This invention discloses an electric power steering torque calculation method, system, and steering control method / system, relating to the field of automotive technology. The electric power steering torque calculation method includes: calculating the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque; determining the target torque based on the rack force, vehicle speed, steering wheel angle, and the measured lateral acceleration of the vehicle; calculating the closed-loop target power steering torque based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque, and current steering wheel torque; calculating the open-loop target power steering torque based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque; and calculating the weighted sum of the open-loop and closed-loop target power steering torques to obtain the motor power steering torque. By decoupling the open-loop and closed-loop power steering torques, and calculating the motor power steering torque based on both, closed-loop control of the hand torque based on motor feedback is achieved, which can optimize the user's hand feel.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, specifically to an electric power steering system, and more specifically to an electric power steering torque calculation method, an electric power steering torque calculation system, an electric power steering control method, an electric power steering control system, a vehicle, and a computer-readable storage medium. Background Technology

[0002] Currently, the basic power steering unit in electric power steering systems obtains speed-sensitive power assistance by linearly interpolating the driver's steering torque and current vehicle speed using a lookup table, and then calculates the power steering motor's torque or control current. This basic power steering characteristic is usually iteratively corrected in the later stages of development, before acceptance, through real-vehicle testing based on the subjective feel of calibration evaluators. It has no significant relation to the vehicle's current driving posture and body condition, typically resulting in a unique power steering characteristic curve for each vehicle. Furthermore, the calibration parameters used by different calibration personnel vary, failing to adequately meet customers' requirements for consistent feel and leading to a poor driving experience.

[0003] Patent CN101722980B describes an electric power steering system with independently adjustable, curve-type assist characteristics. This system consists of a traditional mechanical steering system with an added torque sensor, electronic control unit, power steering motor, and reduction gear. The torque sensor is mounted on the steering shaft to detect the driver's steering torque T. d The power steering motor is mounted on the steering shaft or steering gear, and provides power assist torque T to the driver through a reduction gear. a The electronic control unit calculates the required drive current to the power assist motor based on the current vehicle driving conditions and the magnitude of the steering torque, in order to generate the corresponding assist torque; characterized in that, at a certain vehicle speed, the steering torque T d With assist torque T a The corresponding relationship is defined by a parameter-independent adjustable curve-type assist characteristic curve, where the horizontal axis of the assist characteristic curve is the operating torque and the vertical axis is the corresponding assist torque.

[0004] Patent CN106882260B discloses a method for dynamically calibrating the characteristics of brushed electric power steering (EPS) current in automobiles. This method can be matched and adapted to relevant physical parameters of the vehicle to adjust the parameter settings of the electronic control unit (ECU) in the EPS, enabling the EPS to output optimal power steering characteristics to meet the vehicle's steering performance requirements. Simultaneously, this method is also applicable to ECU parameter calibration in laboratory conditions, allowing for EPS power steering characteristics closer to those used in real-world applications, reducing the workload of real-world calibration. The calibration method of this invention equates the EPS power steering characteristics with the power steering current (I) characteristics output by the ECU. The characteristic curve of the power steering current (I) is calibrated, and the vehicle's speed (V) and steering force (T) are correlated with various parameters of the power steering current (I) characteristic curve. A small number of key feature points are set to dynamically adjust the full-process calibration of other feature parameters, achieving visualization and precision, simple operation, and a short cycle time.

[0005] Based on the aforementioned existing technologies, it can be seen that the mainstream solutions currently rely on the driver's steering torque and vehicle speed collected by torque sensors as the main input signals. These signals are used to design a two-dimensional basic assist characteristic curve of the motor's assist torque or assist current versus steering torque and vehicle speed, and then the assist torque of the motor is calculated. This method does not consider the vehicle's driving posture or the chassis dynamics model of the current vehicle motion. It lacks closed-loop control of the vehicle's behavior after assist is applied and does not consider the overall vehicle motion posture. The assist characteristic curve is designed and calibrated primarily based on human subjective feeling. This design, which does not consider the vehicle's motion characteristics, often leads to distorted feel. This results in abnormal feel under specific operating conditions due to the vehicle's chassis motion characteristics, causing frustration for customers. Furthermore, the subjective design of the assist characteristic curve wastes significant manpower and effort in calibration and acceptance. Summary of the Invention

[0006] One objective of this invention is to provide a method for calculating electric power steering torque. This method estimates rack force, determines a target torque based on rack force, vehicle speed, steering wheel angle, and the vehicle's measured lateral acceleration, and uses the target torque as feedback assist torque in closed-loop control with steering wheel torque to calculate the closed-loop target assist torque. The open-loop target assist torque is then calculated based on the rack force and target torque. The motor assist torque is a weighted sum of the closed-loop and open-loop target assist torques. During steering control, this method combines the driver's intention with vehicle attitude control, resulting in a better driving experience. A second objective is to provide an electric power steering control method. This method can better calculate the motor assist torque and control the vehicle based on the calculated motor assist torque. It avoids unexpected feel effects caused by sudden changes in steering feel, better ensuring consistency in steering feel and improving the driver's experience in vehicle handling.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for calculating electric assist torque, the method comprising:

[0009] Calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque;

[0010] The target torque is determined based on the rack force, vehicle speed, steering wheel angle, and the vehicle's measured lateral acceleration.

[0011] The closed-loop target assist torque is calculated based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque, and current steering wheel torque.

[0012] The open-loop target assist torque is calculated based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque.

[0013] The motor assist torque is obtained by calculating the weighted sum of the open-loop target assist torque and the closed-loop target assist torque.

[0014] Based on the above technical means, the steering wheel angle reflects the driver's intention, while the vehicle speed, the measured lateral acceleration of the vehicle, and the forward return value of the motor torque reflect the vehicle's motion posture. By decoupling, the open-loop assist torque and the closed-loop assist torque are obtained. Based on these two, the motor assist torque is calculated, realizing closed-loop control of the hand torque based on motor feedback. This can optimize the user's hand feel and decouple it from the subjective hand feel calibration of the calibration personnel. By utilizing the vehicle posture, i.e., the vehicle's lateral acceleration information and the vehicle's current rack force, vehicle steering control is achieved.

[0015] In this embodiment of the application, determining the target torque based on the rack force, vehicle speed, steering wheel angle, and the measured lateral acceleration of the vehicle includes:

[0016] Calculate the first lateral acceleration based on the rack force and vehicle speed;

[0017] Calculate the second lateral acceleration based on the steering wheel angle and vehicle speed;

[0018] The third lateral acceleration is calculated based on the vehicle's measured lateral acceleration.

[0019] The target torque is determined based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration.

[0020] Based on the above technical means, the current motion posture of the vehicle can be calculated from three different directions. The target torque is determined by three sets of completely decoupled lateral accelerations. The determined target torque has a high correlation with the vehicle posture, which reduces the influence of subjective calibration personnel on the calibration of the vehicle's feel. At the same time, there is no need to repeat the calibration for different vehicle models. The vehicle's feel is only related to the vehicle's posture.

[0021] In this embodiment of the application, calculating the first lateral acceleration based on the rack force and vehicle speed includes:

[0022] Determine the gain value corresponding to the current vehicle speed from the gain-vehicle speed equivalent identification map;

[0023] The first lateral acceleration is obtained by calculating the product of the rack force and the determined gain value. The gain-vehicle speed equivalent identification map is obtained through experimental calibration.

[0024] Based on the above technical means, the corresponding gain value is determined from the calibrated gain-vehicle speed equivalent identification map according to the current vehicle speed. This value is then used to calculate the first lateral acceleration with the rack force calculated based on the vehicle's own data. The calculation process uses vehicle-based data, which can decouple the calculation process from the subjective design curve of the personnel.

[0025] In this embodiment of the application, calculating the second lateral acceleration based on the steering wheel angle and vehicle speed includes:

[0026] Based on the steering wheel angle and vehicle speed, the vehicle's angle-based lateral acceleration is calculated using vehicle dynamics equations.

[0027] The first weight is determined from the angle-based lateral acceleration weight map based on the angle-based lateral acceleration and vehicle speed.

[0028] The second lateral acceleration is obtained by calculating the product of the angle-based lateral acceleration and the determined first weight. The angle-based lateral acceleration weight map is obtained through experimental calibration.

[0029] Based on the above technical means, the corresponding first weight is determined from the angle-based lateral acceleration weight map based on the angle-based lateral acceleration and velocity. The angle-based lateral acceleration is calculated according to the vehicle dynamics equation, and it is not necessary to consider the influence of the calibration personnel's subjective design on the calculation of the second lateral acceleration.

[0030] In this embodiment of the application, the calculation of the third lateral acceleration based on the measured lateral acceleration of the vehicle includes:

[0031] The second weight is determined from the measured lateral acceleration weight map based on the measured lateral acceleration and vehicle speed.

[0032] The product of the measured lateral acceleration and the determined second weight is calculated to obtain the third lateral acceleration value. The measured lateral acceleration weight map is obtained through experimental calibration.

[0033] Based on the above technical means, the second weight is determined according to the measured lateral acceleration and vehicle speed of the vehicle, and then the weight is calculated with the measured lateral acceleration to obtain the third lateral acceleration, which reduces the influence of the subjective design of the calibration personnel on the third lateral acceleration.

[0034] In this embodiment of the application, determining the target torque based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration includes:

[0035] The first lateral acceleration, the second lateral acceleration, and the third lateral acceleration are weighted and summed to obtain the equivalent lateral acceleration, wherein the weight of the first lateral acceleration is 1, the weight of the second lateral acceleration is the first weight, and the weight of the third lateral acceleration is the second weight.

[0036] The target torque is determined from the steering wheel angle weighting diagram based on the equivalent lateral acceleration, which is determined by experimental calibration.

[0037] Based on the above technical means, by using the current vehicle posture calculated from three different dimensions and performing a weighted summation, the resulting vehicle motion posture can more realistically reflect the actual posture of the current vehicle, and thus the determined target torque can more realistically reflect the torque of the current vehicle.

[0038] In this embodiment of the application, the closed-loop target assist torque is calculated based on the target torque, the vehicle's hysteresis compensation torque, and the current steering wheel torque, including:

[0039] Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque;

[0040] Calculate the first difference between the first sum and the current steering wheel torque;

[0041] The proportional coefficient of the closed-loop control is determined based on the vehicle speed and rack force.

[0042] The closed-loop target assist torque is obtained by calculating the product of the first difference and the proportional coefficient.

[0043] Based on the above technical means, the target torque and the hysteresis compensation torque are in the same direction. Therefore, the sum of the two is used as the feedback torque in the closed-loop control. Together with the current steering wheel torque, the closed-loop target assist torque is obtained.

[0044] In this embodiment of the application, the open-loop target assist torque is calculated based on the rack force, the vehicle's hysteresis compensation torque, and the target torque, including:

[0045] Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque;

[0046] Calculate the second difference between the rack force and the first sum;

[0047] The first coefficient related to vehicle speed is determined based on vehicle speed and current steering wheel torque;

[0048] The product of the second difference and the first coefficient is calculated to obtain the open-loop target assist torque.

[0049] Based on the above technical means, similarly, the target torque and the hysteresis compensation torque are in the same direction, so the two are summed to obtain the first sum value. The rack force estimates the total force on the rack of the current vehicle. The first sum value is the force that the steering wheel can provide. The difference between the two corresponds to the torque that the motor needs to provide. The torque that the motor needs to provide in the absence of feedback can be calculated by the above method.

[0050] In this embodiment of the application, the rack force of the current steering system is calculated based on the current steering wheel torque and the forward return value of the motor torque, including:

[0051] Add the current steering wheel torque to the previous value of the motor torque to obtain the rack force of the current steering system.

[0052] Using the aforementioned technical methods, the total force currently borne by the vehicle's rack was estimated.

[0053] A second aspect of the present invention provides an electric assist torque calculation system, comprising:

[0054] The rack force calculation module is used to calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque.

[0055] The target torque generation module is used to determine the target torque based on the rack force, vehicle speed, steering wheel angle, and the measured lateral acceleration of the vehicle.

[0056] The closed-loop target assist torque generation module is used to calculate the closed-loop target assist torque based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque and current steering wheel torque.

[0057] The open-loop target assist torque generation module is used to calculate the open-loop target assist torque based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque.

[0058] The motor assist torque generation module is used to calculate the weighted sum of the open-loop target assist torque and the closed-loop target assist torque to obtain the motor assist torque.

[0059] Through the above technical means, the motor assist torque can be calculated based on the vehicle's motion posture, realizing closed-loop control of the hand torque based on motor feedback. This can optimize the user's hand feel and decouple it from the subjective hand feel calibration of the calibration personnel. By utilizing the vehicle's posture, i.e., the vehicle's lateral acceleration information and the vehicle's current rack force, vehicle steering control is achieved.

[0060] A third aspect of the present invention provides an electric power steering control method, the method comprising:

[0061] The electric assist torque is calculated using the electric assist torque calculation method described above;

[0062] Control the operation of the power steering motor to provide steering assistance according to the motor's assist torque.

[0063] By employing the aforementioned technical means, the motor assist torque can be calculated more effectively, and control can be implemented based on the calculated motor assist torque. This prevents unexpected changes in steering feel caused by a single sudden change in feel, thus better ensuring the consistency of steering feel and improving the driver's driving experience.

[0064] A fourth aspect of the present invention provides an electric power steering control system, the system comprising:

[0065] The control unit is used to calculate the motor assist torque according to the electric assist torque calculation method, and send an action command to the assist motor according to the calculated motor assist torque.

[0066] A power steering motor is used to execute the action commands to provide steering assistance.

[0067] The aforementioned technical means can improve the driver's driving experience in controlling the vehicle.

[0068] The fifth aspect of the present invention provides a vehicle in which electric power steering is achieved by applying the electric power steering control method described above.

[0069] A sixth aspect of the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the electric power assist torque calculation method or the electric power assist steering control method.

[0070] The beneficial effects of this invention are:

[0071] (1) This invention provides a method for calculating electric power assist torque. This method estimates the rack force, determines the target torque based on the rack force, vehicle speed, steering wheel angle and the measured lateral acceleration of the vehicle, uses the target torque as feedback assist torque and performs closed-loop control with the steering wheel torque, calculates the closed-loop target assist torque, and calculates the open-loop target assist torque based on the rack force and the target torque. The electric motor assist torque is the weighted sum of the closed-loop target assist torque and the open-loop target assist torque. During steering control, the driver's driving intention is combined with the vehicle's attitude control, resulting in a better driving experience.

[0072] In this method, the target torque, as a feedback torque, forms a closed-loop control with the steering wheel force rectangle. The intermediate logic is based on vehicle dynamics formulas, incorporating the lateral motion posture of the entire vehicle chassis into the system for calculation. The calculated target torque carries the dynamic characteristics of the vehicle's current motion, providing the driver with a better driving feel. Furthermore, when changing vehicle platforms, no additional calibration of feel information is required; a single set of parameters can be used across multiple vehicle models to achieve the customer's required feel, significantly shortening calibration and development work, saving manpower and resources, and improving product reliability.

[0073] (2) The present invention provides an electric power steering control method, which can better calculate the motor assist torque and control the vehicle based on the calculated motor assist torque. It will not cause unexpected hand feel effects due to a single sudden change in hand feel, thus better ensuring the consistency of steering hand feel and improving the driver's driving experience of vehicle operation. Attached Figure Description

[0074] Figure 1 A flowchart of an electric assist torque calculation method provided in one embodiment of the present invention;

[0075] Figure 2 A schematic diagram illustrating the calculation principle of rack force in an electric power assist torque calculation method provided by one embodiment of the present invention;

[0076] Figure 3 This is a schematic diagram illustrating the calculation principle of the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration in an electric power assist torque calculation method provided by an embodiment of the present invention.

[0077] Figure 4 This is a schematic diagram illustrating the target torque calculation principle in an electric power assist torque calculation method provided by one embodiment of the present invention.

[0078] Figure 5 This is a schematic diagram illustrating the closed-loop target assist torque calculation principle in an electric assist torque calculation method provided by an embodiment of the present invention.

[0079] Figure 6This is a schematic diagram illustrating the open-loop target assist torque calculation principle in an electric assist torque calculation method provided by an embodiment of the present invention.

[0080] Figure 7 A block diagram of an electric assist torque calculation system provided in one embodiment of the present invention;

[0081] Figure 8 A flowchart of an electric power steering control method according to one embodiment of the present invention;

[0082] Figure 9 This is a block diagram of an electric power steering control system provided in one embodiment of the present invention. Detailed Implementation

[0083] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0084] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0085] One embodiment of this application provides a method for calculating electric assist torque, such as... Figure 1 As shown, the method includes:

[0086] S1: Calculate the rack force STE_RF of the current steering system based on the current steering wheel torque and the forward return value of the motor torque.

[0087] In the embodiments of this application, such as Figure 2As shown, the rack force of the current steering system is obtained by adding the current steering wheel torque to the previous value of the motor torque. The rack force calculated at this point is the unprocessed rack force torque. It can be limited in amplitude using a limiter, followed by LPF low-pass filtering. LPF low-pass filtering can suppress the gain of high-frequency signals, reducing the feel fluctuations caused by high-frequency components in the system. After the above processing, an accurate estimated rack force is obtained. In this embodiment, the previous value of the motor torque is the assist torque of the motor during the previous control cycle. In this embodiment, the amplitude of the limiter is designed differently based on parameters such as vehicle model and load. Through the above technical means, the total force borne by the rack of the current vehicle is estimated.

[0088] S2: Determine the target torque based on the rack force, vehicle speed, steering wheel angle, and the vehicle's measured lateral acceleration, such as... Figure 3 As shown, it specifically includes:

[0089] S201: Calculate the first lateral acceleration based on the rack force and vehicle speed. In this embodiment, this specifically includes:

[0090] Determine the gain value corresponding to the current vehicle speed from the gain-vehicle speed equivalent identification map;

[0091] The first lateral acceleration is obtained by calculating the product of the rack force and the determined gain value. The gain-vehicle speed equivalent identification map is obtained through experimental calibration. In this embodiment, the first lateral acceleration is also called the reference acceleration Lat_RF. In the gain-vehicle speed equivalent identification map, the horizontal axis represents the vehicle speed, and the vertical axis represents the gain value. A gain value can be determined based on the current vehicle speed. The first lateral acceleration is obtained by multiplying the rack force by this gain value.

[0092] In other embodiments, after calculating the first lateral acceleration, a limiter is used to limit the amplitude of the first lateral acceleration, which can improve the accuracy of the first lateral acceleration. The amplitude of the limiter is designed differently according to parameters such as vehicle type and load. The above calculation process uses vehicle-based data, which can decouple the calculation process from the subjective design curve by the operator.

[0093] S201: Calculate the second lateral acceleration based on the steering wheel angle and vehicle speed, specifically including:

[0094] Based on the steering wheel angle and vehicle speed, the vehicle's angle-based lateral acceleration is calculated using vehicle dynamics equations. In this embodiment, the calculation formula for the vehicle dynamics equations is as follows:

[0095] γ = k*θ*v², where k is the dynamic constant, θ is the steering wheel angle, v is the vehicle speed, and γ is the lateral acceleration based on the angle.

[0096] The first weight is determined from the angle-based lateral acceleration weight map based on the angle-based lateral acceleration and vehicle speed.

[0097] The second lateral acceleration, Lat_SA, is obtained by multiplying the angle-based lateral acceleration by the determined first weight. The angle-based lateral acceleration weight map is obtained through experimental calibration. In this embodiment, the steering wheel angle weight map is a three-dimensional graph, where the X-axis represents the angle-based lateral acceleration, the Y-axis represents the vehicle speed, and the Z-axis represents the weight. The corresponding weights can be obtained based on the calculated angle-based lateral acceleration and vehicle speed. Multiplying the corresponding weights by the angle-based lateral acceleration yields the second lateral acceleration. To improve the accuracy of the second lateral acceleration, a limiter can be used to limit its amplitude. The amplitude of the limiter is designed differently based on parameters such as vehicle type and load.

[0098] Based on the above technical means, the corresponding first weight is determined from the angle-based lateral acceleration weight map based on the angle-based lateral acceleration and vehicle speed. The angle-based lateral acceleration is calculated according to the vehicle dynamics equation, and the influence of the calibration personnel's subjective design on the calculation of the second lateral acceleration does not need to be considered.

[0099] S203: Calculate the third lateral acceleration based on the vehicle's measured lateral acceleration, specifically including:

[0100] The second weight is determined from the measured lateral acceleration weight map based on the measured lateral acceleration and vehicle speed.

[0101] The product of the measured lateral acceleration and the determined second weight is calculated to obtain the third lateral acceleration value Lat_LA. The measured lateral acceleration weight map is obtained through experimental calibration. In this embodiment, the measured lateral acceleration is the lateral acceleration parsed on the vehicle bus. This lateral acceleration is based on the value collected by the vehicle's own lateral acceleration sensor or the lateral acceleration value calculated by other controllers and sent to the bus. The measured lateral acceleration weight map is a three-dimensional graph. In the graph, the X-axis coordinate is the measured lateral acceleration of the vehicle, the Y-axis coordinate is the vehicle speed, and the Z-axis coordinate is the weight. In this embodiment, in order to improve the accuracy of the third lateral acceleration, a limiter can be used to limit the amplitude of the third lateral acceleration. The amplitude of the limiter is designed differently according to the vehicle model, load, and other parameters. According to the above technical means, the second weight is determined based on the measured lateral acceleration and vehicle speed, and then the weight is calculated with the measured lateral acceleration to obtain the third lateral acceleration, reducing the influence of the subjective design of the calibration personnel on the third lateral acceleration.

[0102] S204: Determine the target torque based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration, such as... Figure 4 As shown, it specifically includes:

[0103] The first lateral acceleration, the second lateral acceleration, and the third lateral acceleration are weighted and summed to obtain the equivalent lateral acceleration, wherein the weight of the first lateral acceleration is 1, the weight of the second lateral acceleration is the first weight, and the weight of the third lateral acceleration is the second weight.

[0104] The target torque is determined from the steering wheel angle weighting diagram based on the equivalent lateral acceleration, which is determined through experimental calibration. In this embodiment, the horizontal axis of the steering wheel angle weighting diagram represents the equivalent lateral acceleration, and the vertical axis represents the weight.

[0105] Based on the above technical means, by using the current vehicle posture calculated from three different dimensions and performing a weighted summation, the resulting vehicle motion posture can more realistically reflect the actual posture of the current vehicle, and thus the determined target torque can more realistically reflect the torque of the current vehicle.

[0106] Based on the above technical means, the current vehicle's motion posture can be calculated from three different dimensions. The target torque is determined by three sets of completely decoupled lateral accelerations. The determined target torque has a high correlation with the vehicle posture, reducing the influence of subjective calibration personnel on the calibration of the vehicle's feel. At the same time, there is no need to repeat calibration for different vehicle models. The vehicle's feel is only related to the vehicle's posture.

[0107] In the above embodiments, the angle-based lateral acceleration weight map, the measured lateral acceleration weight map, and the steering wheel angle weight map can be designed according to different operation and control requirements.

[0108] S3: Calculate the closed-loop target assist torque based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque, and current steering wheel torque, such as... Figure 5 As shown, it specifically includes:

[0109] S301: Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque. In this embodiment, the hysteresis compensation torque is the compensation torque for the vehicle to overcome friction, which is ideally zero. This hysteresis compensation torque is calculated based on the vehicle's configuration and parameters. The target torque and the hysteresis compensation torque are in the same direction, and they will superimpose when they act; therefore, they are added together to calculate the first sum.

[0110] S302: Calculate the first difference between the first sum and the current steering wheel torque.

[0111] S303: Determine the proportional coefficient of the closed-loop control based on the vehicle speed and rack force. In this embodiment, the proportional coefficient refers to the proportional coefficient Kp of the closed-loop control. Different proportional coefficients can achieve different control effects for the same action. The proportional coefficient is obtained from the closed-loop proportional coefficient diagram, where the X-axis coordinate is the rack force, the Y-axis coordinate is the vehicle speed, and the Z-axis coordinate is the proportional coefficient.

[0112] S304: Calculate the product of the first difference and the proportional coefficient to obtain the closed-loop target assist torque. In some embodiments, to improve the accuracy of the closed-loop target assist torque, a limiter can be used to limit the amplitude of the closed-loop target assist torque. The amplitude of the limiter is designed differently according to parameters such as vehicle model and load. Steering wheel torque is the same as hand torque. This method provides closed-loop control of hand torque, which is stable and continuous, and provides a stable feel, thus providing the driver with a consistent feel and reducing the influence of subjective human calibration on steering feel.

[0113] The calculation of the closed-loop target assist torque utilizes the principle of closed-loop control. In actual driving, the driver expects the torque provided by the motor after completing its response to be consistent with the current steering wheel torque. The current steering wheel torque is the effect the driver inputs to achieve, while the target torque is based on the feedback effect. Therefore, the calculated target torque is used as the feedback signal in the closed-loop control, and the current steering wheel torque is used as the target signal. The proportional coefficient is determined based on the vehicle speed and rack force to perform closed-loop control.

[0114] S4: Calculate the open-loop target assist torque based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and the target torque. Figure 6 As shown, it specifically includes:

[0115] S401: Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque. The target torque and the hysteresis compensation torque are in the same direction and will be superimposed when they act. Therefore, the two are added together to calculate the first sum.

[0116] S402: Calculate the second difference between the rack force and the first sum. In this application, the rack force is the total force applied to the rack. The rack force is equal to the sum of the steering wheel torque and the motor torque. The first sum belongs to the torque already provided by the current system. The difference needs to be compensated by the power assist motor.

[0117] S403: A first coefficient related to vehicle speed is determined based on the vehicle speed and the current steering wheel torque. In this embodiment, the first coefficient is obtained from the steering wheel torque gain curve. The X-axis coordinate of the steering wheel torque gain curve is the steering wheel torque, the Y-axis coordinate is the vehicle speed, and the Z-axis coordinate is the gain value. In this embodiment, the first coefficient needs to be calibrated based on a real vehicle. In one embodiment of this application, the gain value is 1 when the steering wheel torque is any value.

[0118] S404: Calculate the product of the second difference and the first coefficient to obtain the open-loop target assist torque.

[0119] In some embodiments, in order to improve the accuracy of the open-loop target assist torque, a limiter can be used to limit the amplitude of the open-loop target assist torque. The amplitude of the limiter is designed differently according to parameters such as vehicle type and load.

[0120] Based on the above technical means, similarly, the target torque and the hysteresis compensation torque are in the same direction, so the two are summed to obtain the first sum value. The rack force estimates the total force on the rack of the current vehicle. The first sum value is the force that the steering wheel can provide. The difference between the two corresponds to the torque that the motor needs to provide. The torque that the motor needs to provide in the absence of feedback can be calculated by the above method.

[0121] S5: Calculate the weighted sum of the open-loop target assist torque and the closed-loop target assist torque to obtain the motor assist torque. In this embodiment, the sum of the weights of the open-loop target assist torque and the closed-loop target assist torque is 1, and the specific value is set according to the driver's or OEM's own style.

[0122] In this embodiment, if the steering system has other compensation torques and advanced function torques superimposed, they will also be superimposed on the motor assist torque for unified output.

[0123] Based on the aforementioned technical methods, the steering wheel angle reflects the driver's intention, while vehicle speed, measured lateral acceleration, and forward torque of the motor reflect the vehicle's motion posture. By decoupling, open-loop and closed-loop assist torques are obtained, and the motor assist torque is calculated based on these two parameters. This achieves closed-loop control of the hand torque based on motor feedback, optimizing the user's feel while decoupling from the subjective feel calibration by calibration personnel. Vehicle steering control is achieved using vehicle posture information, i.e., lateral acceleration, and the current rack force. The vehicle steering torque is calculated by weighting the closed-loop and open-loop control torques, preventing unexpected feel effects from a single abrupt change in feel, thus better ensuring the consistency of steering feel and improving the driver's driving experience.

[0124] The method described in this application requires obtaining different calibration curves based on vehicle attitude during the design phase, eliminating the need for calibration based on different handling feel requirements. The established calibration work caters to the needs of different drivers. The calibrated curves can be applied to different vehicle models and platforms, reducing the complexity of vehicle handling feel calibration. Furthermore, when changing vehicle platforms, no additional handling feel information calibration is required; a single set of parameters can be used across multiple vehicle types to achieve the customer's required handling feel. This significantly reduces calibration development work, saves manpower and resources, shortens product development and calibration cycles, and increases product reliability.

[0125] The electric torque assist method described in this application only needs to consider the vehicle's lateral acceleration, which is related to the vehicle's motion posture. Parameters in the calibration curve can be adjusted according to different driving habits and handling styles, thereby improving the user experience. It also accommodates different driving modes for different customers, better conforms to the kinematic characteristics of the chassis control system, and solves the problem of inconsistent feel caused by subjectively designed assist curves. This method better integrates vehicle motion posture and steering system control, resulting in more precise steering control. It also provides good theoretical support and an interface for later chassis domain control integration for overall vehicle posture control, leading to more refined steering system control.

[0126] This invention also provides an electric power assist torque calculation system, such as... Figure 7 As shown, it includes:

[0127] The rack force calculation module is used to calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque.

[0128] The target torque generation module is used to determine the target torque based on the rack force, vehicle speed, steering wheel angle, and the measured lateral acceleration of the vehicle.

[0129] The closed-loop target assist torque generation module is used to calculate the closed-loop target assist torque based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque and current steering wheel torque.

[0130] The open-loop target assist torque generation module is used to calculate the open-loop target assist torque based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque.

[0131] The motor assist torque generation module is used to calculate the weighted sum of the open-loop target assist torque and the closed-loop target assist torque to obtain the motor assist torque.

[0132] Through the above technical means, the motor assist torque can be calculated based on the vehicle's motion posture, realizing closed-loop control of the hand torque based on motor feedback. This can optimize the user's hand feel and decouple it from the subjective hand feel calibration of the calibration personnel. By utilizing the vehicle's posture, i.e., the vehicle's lateral acceleration information and the vehicle's current rack force, vehicle steering control is achieved.

[0133] Another embodiment of the present invention provides an electric power steering control method, such as... Figure 8 As shown, the method includes:

[0134] The electric assist torque is calculated using the electric assist torque calculation method described above;

[0135] Control the operation of the power steering motor to provide steering assistance according to the motor's assist torque.

[0136] Steering control simulation was performed based on the electric power steering control method of this application. In the response curves of steering wheel torque and motor assist torque, the current assist torque of the motor has a small phase delay with the steering wheel torque, and there is no obvious torque fluctuation or insufficient response.

[0137] By employing the aforementioned technical means, the motor assist torque can be calculated more effectively, and control can be implemented based on the calculated motor assist torque. This prevents unexpected changes in steering feel caused by a single sudden change in feel, thus better ensuring the consistency of steering feel and improving the driver's driving experience.

[0138] This invention also provides an electric power steering control system, such as... Figure 9 As shown, the system includes:

[0139] The control unit is used to calculate the motor assist torque according to the electric assist torque calculation method, and send an action command to the assist motor according to the calculated motor assist torque.

[0140] A power steering motor is used to execute the action commands to provide steering assistance.

[0141] The aforementioned technical means can improve the driver's driving experience in controlling the vehicle.

[0142] The present invention also provides a vehicle that uses the electric power steering control method described above to achieve electric power steering.

[0143] On the other hand, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the electric power assist torque calculation method or the electric power assist steering control method.

[0144] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for calculating electric assist torque, characterized in that, The method includes: Calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque; The target torque is determined based on the rack force, vehicle speed, steering wheel angle, and the vehicle's measured lateral acceleration. The closed-loop target assist torque is calculated based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque, and current steering wheel torque. The open-loop target assist torque is calculated based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque. Calculate the weighted sum of the open-loop target assist torque and the closed-loop target assist torque to obtain the motor assist torque; the determination of the target torque based on the rack force, vehicle speed, steering wheel angle, and the vehicle's measured lateral acceleration includes: Calculate the first lateral acceleration based on the rack force and vehicle speed; Calculate the second lateral acceleration based on the steering wheel angle and vehicle speed; The third lateral acceleration is calculated based on the vehicle's measured lateral acceleration. The target torque is determined based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration.

2. The electric assist torque calculation method according to claim 1, characterized in that, The first lateral acceleration is calculated based on the rack force and vehicle speed, including: Determine the gain value corresponding to the current vehicle speed from the gain-vehicle speed equivalent identification map; The first lateral acceleration is obtained by calculating the product of the rack force and the determined gain value. The gain-vehicle speed equivalent identification map is obtained through experimental calibration.

3. The electric assist torque calculation method according to claim 2, characterized in that, The second lateral acceleration is calculated based on the steering wheel angle and vehicle speed, including: Based on the steering wheel angle and vehicle speed, the vehicle's angle-based lateral acceleration is calculated using vehicle dynamics equations. The first weight is determined from the angle-based lateral acceleration weight map based on the angle-based lateral acceleration and vehicle speed. The second lateral acceleration is obtained by calculating the product of the angle-based lateral acceleration and the determined first weight. The angle-based lateral acceleration weight map is obtained through experimental calibration.

4. The electric assist torque calculation method according to claim 3, characterized in that, The calculation of the third lateral acceleration based on the vehicle's measured lateral acceleration includes: The second weight is determined from the measured lateral acceleration weight map based on the measured lateral acceleration and vehicle speed. The product of the measured lateral acceleration and the determined second weight is calculated to obtain the third lateral acceleration value. The measured lateral acceleration weight map is obtained through experimental calibration.

5. The electric assist torque calculation method according to claim 4, characterized in that, Determining the target torque based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration includes: The first lateral acceleration, the second lateral acceleration, and the third lateral acceleration are weighted and summed to obtain the equivalent lateral acceleration, wherein the weight of the first lateral acceleration is 1, the weight of the second lateral acceleration is the first weight, and the weight of the third lateral acceleration is the second weight. The target torque is determined from the steering wheel angle weighting diagram based on the equivalent lateral acceleration, which is determined by experimental calibration.

6. The method for calculating electric assist torque according to claim 1, characterized in that, The closed-loop target assist torque is calculated based on the target torque, the vehicle's hysteresis compensation torque, and the current steering wheel torque, including: Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque; Calculate the first difference between the first sum and the current steering wheel torque; The proportional coefficient of the closed-loop control is determined based on the vehicle speed and rack force. The closed-loop target assist torque is obtained by calculating the product of the first difference and the proportional coefficient.

7. The method for calculating electric assist torque according to claim 1, characterized in that, The open-loop target assist torque is calculated based on the rack force, the vehicle's hysteresis compensation torque, and the target torque, including: Calculate the first sum of the target torque and the vehicle's hysteresis compensation torque; Calculate the second difference between the rack force and the first sum; The first coefficient related to vehicle speed is determined based on vehicle speed and current steering wheel torque; The product of the second difference and the first coefficient is calculated to obtain the open-loop target assist torque.

8. The method for calculating electric assist torque according to claim 1, characterized in that, Calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque, including: Add the current steering wheel torque to the previous value of the motor torque to obtain the rack force of the current steering system.

9. An electric assist torque calculation system, characterized in that, include: The rack force calculation module is used to calculate the rack force of the current steering system based on the current steering wheel torque and the forward return value of the motor torque. The target torque generation module is used to determine the target torque based on the rack force, vehicle speed, steering wheel angle, and the measured lateral acceleration of the vehicle. The closed-loop target assist torque generation module is used to calculate the closed-loop target assist torque based on the rack force, vehicle speed, target torque, vehicle hysteresis compensation torque and current steering wheel torque. The open-loop target assist torque generation module is used to calculate the open-loop target assist torque based on the rack force, vehicle speed, current steering wheel torque, vehicle hysteresis compensation torque, and target torque. The motor assist torque generation module is used to calculate the weighted sum of the open-loop target assist torque and the closed-loop target assist torque to obtain the motor assist torque; The determination of the target torque based on the rack force, vehicle speed, steering wheel angle, and measured lateral acceleration of the vehicle includes: Calculate the first lateral acceleration based on the rack force and vehicle speed; Calculate the second lateral acceleration based on the steering wheel angle and vehicle speed; The third lateral acceleration is calculated based on the vehicle's measured lateral acceleration. The target torque is determined based on the first lateral acceleration, the second lateral acceleration, and the third lateral acceleration.

10. An electric power steering control method, characterized in that, The method includes: The electric assist torque is calculated using the electric assist torque calculation method described in any one of claims 1-8; Control the operation of the power steering motor to provide steering assistance according to the motor's assist torque.

11. An electric power steering control system, characterized in that, The system includes: The control unit is used to calculate the motor assist torque according to the electric assist torque calculation method according to any one of claims 1-8, and send an action command to the assist motor according to the calculated motor assist torque; A power steering motor is used to execute the action commands to provide steering assistance.

12. A vehicle, characterized in that, The vehicle uses the electric power steering control method of claim 10 to achieve electric power steering.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the electric power steering torque calculation method as described in any one of claims 1-8 or the electric power steering control method as described in claim 10.

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