Friction compensation control method and device for electric power steering system

Abstract

The present invention relates to the field of vehicle control, and to a friction compensation control method and device for an electric power steering system. The method provided in the embodiment of the present application comprehensively considers the steering dynamic data of the vehicle during the steering process, the hand torque input by the driver's operation, and the steering torque of the motor on the steering column, and can comprehensively and accurately calculate the friction torque. The entire calculation process fully considers the influence of various factors on the friction torque, thereby providing an accurate basis for subsequent compensation, effectively reducing or eliminating the interference with the return and damping functions caused by the friction of the EPS motor, reducer and mechanical system, improving the poor feel caused by the friction hysteresis effect, and enhancing the overall performance and driving experience of the EPS. In addition, it can also adapt to various driving conditions and road conditions, and can provide optimal steering assistance and friction compensation whether it is high-speed driving or low-speed turning.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control, and in particular to a friction compensation control method and device for an electric power steering system. Background Art

[0002] The Electric Power Steering (EPS) system is a mechatronic device that uses a servo motor as an actuator and works in conjunction with the vehicle's mechanical steering system to assist the driver in steering. As vehicles continue to become more intelligent, EPS systems are a crucial foundation. Research into improving EPS driving feel and optimizing its performance is gaining increasing attention in the industry.

[0003] Friction in the EPS motor, reducer, and mechanical system can cause a range of issues. For example, it can affect the vehicle's self-centering and damping functions, preventing it from returning to center promptly and smoothly after a turn, or causing unsatisfactory damping. Furthermore, the hysteresis effect of friction can degrade driving feel, causing the driver to experience awkward steering movements. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a friction compensation control method and device for an electric power steering system to solve the problem of how to reduce or eliminate the adverse effects caused by friction of the EPS motor, reducer and mechanical system, and to improve the problem of poor operating feel caused by the friction hysteresis effect.

[0005] In a first aspect, an embodiment of the present invention provides a friction compensation control method for an electric power steering system, the method comprising:

[0006] detecting a hand torque generated by a driver turning a steering wheel during a steering process of the vehicle, and obtaining a steering torque applied by a motor in the vehicle to a steering column during the steering process;

[0007] Acquiring steering dynamic data of the vehicle during a steering process, and calculating a friction torque based on the steering dynamic data, the hand torque, and the steering torque;

[0008] Obtaining a friction compensation coefficient, and calculating a friction compensation torque using the friction compensation coefficient and the friction torque;

[0009] The motor in the vehicle is controlled to perform torque compensation according to the friction compensation torque.

[0010] Furthermore, obtaining the steering torque of the motor in the vehicle on the steering column during the steering process includes:

[0011] Obtaining a basic power-assisting torque provided by the motor for the electric power steering system, and obtaining a rotation angle of the steering wheel during the steering process;

[0012] The steering torque of the motor on the steering column during the steering process is calculated using the rotation angle of the steering wheel and the basic power-assisting torque.

[0013] Furthermore, the calculating of the steering torque of the motor on the steering column during the steering process by using the rotation angle of the steering wheel and the basic power-assist torque includes:

[0014] Obtaining a gear rack modification coefficient corresponding to the rotation angle;

[0015] Obtaining a first transmission ratio of the belt drive and a second transmission ratio of the ball screw during a steering process of the vehicle;

[0016] A first product of the basic assist torque, the first transmission ratio, and the rack and pinion modification coefficient is calculated, and a ratio of the first product to the second transmission ratio is used as the steering torque.

[0017] Furthermore, the calculating of the friction torque based on the steering dynamic data, the hand torque and the steering torque includes:

[0018] comparing the hand torque with a hand torque limit, and comparing the steering torque with a steering torque limit;

[0019] If the hand torque is higher than the hand torque limit, and the steering torque is higher than the steering torque limit, limiting the hand torque to obtain a limited hand torque, and limiting the steering torque to obtain a limited steering torque;

[0020] Calculating a system torque using the limited hand torque and the limited steering torque;

[0021] acquiring a driving speed of the vehicle during the steering process and a rotation parameter of the steering wheel based on the steering dynamics data;

[0022] The friction torque is calculated using the driving speed, the rotational parameter, and the system torque.

[0023] Furthermore, the calculating the friction torque using the driving speed, the rotation parameter and the system torque includes:

[0024] Obtaining an initial friction torque obtained during the calibration process, and superimposing the initial friction torque with the friction torque loss caused by the hand torque effect to obtain a compensation friction torque, and using the compensation friction torque as the second torque;

[0025] Obtaining a conversion coefficient and a first torque corresponding to the driving speed, wherein the first torque is generated by a phase lag of the motor and mechanical friction of the reducer;

[0026] Calculating a difference between the system torque and the first torque, and calculating a second product between the difference and the conversion coefficient;

[0027] A sum of the second product and the second torque is calculated, and the sum is used as the friction torque.

[0028] Furthermore, obtaining the friction compensation coefficient includes:

[0029] Obtaining a steering wheel speed during the steering process;

[0030] querying a dynamic friction coefficient corresponding to the steering wheel speed and a static friction coefficient corresponding to the steering wheel speed;

[0031] The friction compensation coefficient is obtained based on the sum of the dynamic friction coefficient and the static friction coefficient.

[0032] Furthermore, obtaining the friction compensation coefficient includes:

[0033] Obtaining a rate of change of the hand torque during the steering process of the vehicle, and using the rate of change to query a corresponding rate of change of the friction compensation coefficient;

[0034] Comparing a current rotation angle of the steering wheel with a target rotation angle to obtain a positional relationship between the current rotation angle and the target rotation angle;

[0035] A calculation strategy corresponding to the positional relationship and a previous historical friction compensation coefficient are obtained, and the historical friction compensation coefficient and the friction compensation coefficient change rate are calculated according to the calculation strategy to obtain the friction compensation coefficient.

[0036] In a second aspect, an embodiment of the present invention provides a friction compensation control device for an electric power steering system, the device comprising:

[0037] a detection module, configured to detect a hand torque generated by a driver turning a steering wheel during a steering process of the vehicle, and obtain a steering torque applied by a motor in the vehicle to a steering column during the steering process;

[0038] an acquisition module, configured to acquire steering dynamic data of the vehicle during a steering process, and calculate a friction torque based on the steering dynamic data, the hand torque, and the steering torque;

[0039] a calculation module, configured to obtain a friction compensation coefficient and calculate a friction compensation torque using the friction compensation coefficient and the friction torque;

[0040] A control module is used to control the motor in the vehicle to perform torque compensation according to the friction compensation torque.

[0041] In a third aspect, an embodiment of the present invention provides an electronic device comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, computer instructions being stored in the memory, and the processor executing the method of the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0042] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method of the first aspect or any corresponding embodiment thereof.

[0043] The method provided in the embodiment of the present application comprehensively considers the steering dynamics data of the vehicle during the steering process, the hand torque input by the driver, and the steering torque of the motor on the steering column, and can comprehensively and accurately calculate the friction torque. The entire calculation process fully considers the impact of various factors on the friction torque, thereby providing an accurate basis for subsequent compensation, effectively reducing or eliminating the interference with the return and damping functions caused by the friction of the EPS motor, reducer and mechanical system, improving the poor feel caused by the friction hysteresis effect, and enhancing the overall performance and driving experience of the EPS. In addition, it can adapt to various driving conditions and road conditions, and can provide optimal steering assistance and friction compensation whether it is high-speed driving or low-speed cornering.

[0044] The method provided in the embodiments of this application obtains the dynamic and static friction coefficients corresponding to the steering wheel speed and, by summing them, derives the friction compensation coefficient. This method can more accurately compensate for friction in the steering system, taking into account the friction characteristics at different speeds, making steering operations more precise and responsive, consistent with the driver's steering intent. It can also effectively reduce inconsistent or uncomfortable steering feel caused by changes in friction. The driver will experience a smoother and more natural steering experience, enhancing the driving experience.

[0045] The method provided in the embodiments of the present application calculates the friction compensation coefficient based on the relationship between the rate of change of hand torque and the position of the steering wheel. This method can provide personalized steering assistance compensation for drivers with different driving styles and operating habits, making the steering experience more tailored to the needs of each driver. At the same time, real-time acquisition of the rate of change of hand torque and steering wheel rotation angle information can more accurately determine the current steering state, thereby calculating a more precise friction compensation coefficient and achieving more refined steering control. In addition, by comparing the current rotation angle with the target rotation angle and using a corresponding calculation strategy, the steering process can be made smoother, avoiding sudden changes in steering assistance and improving driving comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 is a flow chart of a friction compensation control method for an electric power steering system according to some embodiments of the present invention;

[0048] Figure 2 is a schematic diagram of torque limitation according to some embodiments of the present invention;

[0049] Figure 3 is a schematic diagram of a torque compensation process according to some embodiments of the present invention;

[0050] Figure 4 is a flow chart of a friction compensation control method for an electric power steering system according to some embodiments of the present invention;

[0051] Figure 5 is a structural block diagram of a friction compensation control device for an electric power steering system according to an embodiment of the present invention;

[0052] Figure 6 FIG. 4 is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0054] According to an embodiment of the present invention, a friction compensation control method and device for an electric power steering system are provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0055] In this embodiment, a friction compensation control method for an electric power steering system is provided. Figure 1FIG. 1 is a flow chart of a friction compensation control method for an electric power steering system according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0056] Step S101 , detecting the hand torque generated by the driver turning the steering wheel during the steering process of the vehicle, and obtaining the steering torque applied by the motor in the vehicle to the steering column during the steering process.

[0057] In an embodiment of the present application, a torque sensor is mounted on a connection component of the steering wheel, such as the steering column, in the vehicle's steering system. When the driver turns the steering wheel, a torque is applied to the steering wheel. This torque is transmitted to the torque sensor through components such as the steering column. The torque sensor senses the magnitude and direction of this torque and converts it into electrical signals. These electrical signals are then transmitted to the vehicle's electronic control unit (ECU) or related control system.

[0058] For example, when the vehicle is traveling at low speeds, the driver may need to apply a large amount of hand torque to turn the steering wheel, resulting in a correspondingly large value detected by the torque sensor. At higher speeds, however, due to the power steering system, the driver's hand torque is relatively small, resulting in a smaller value detected by the torque sensor. Another example is when the driver performs an emergency steering maneuver, where the applied hand torque increases dramatically. The torque sensor can quickly and accurately detect this change.

[0059] In an embodiment of the present application, obtaining the steering torque of a motor in a vehicle on a steering column during steering includes the following steps A1-A2:

[0060] Step A1: obtaining a basic power-assisting torque provided by the motor for the electric power steering system, and obtaining a rotation angle of the steering wheel during the steering process.

[0061] Specifically, during the operation of the electric power steering system (EPS), the basic assist torque is obtained as follows: First, the hand torque input by the driver to the steering wheel is obtained. For example, the driver applies a hand torque of 20N·m when turning the steering wheel. Then, this detected hand torque is amplified by a specific gain factor. Assuming the gain factor is 2, the basic assist torque obtained after amplification is 40N·m. This basic assist torque is generated by the motor and provides the main assist function for the EPS, helping the driver to control the steering wheel more easily.

[0062] During steering, the steering wheel's rotation angle also needs to be detected. This is achieved using a high-precision angle detection device installed in the steering system. When the driver begins to turn the steering wheel, the angle detection device activates in real time. Whether the turn is small, such as 15 degrees, or large, such as 120 degrees, the device accurately measures the steering wheel's rotation angle relative to its initial position and rapidly transmits this data to the EPS control system.

[0063] Step A2: Calculate the steering torque of the motor on the steering column during the steering process using the steering wheel rotation angle and the basic power-assist torque.

[0064] Specifically, the steering torque of the motor on the steering column during the steering process is calculated using the steering wheel rotation angle and the basic power torque, including: first, obtaining the gear rack displacement coefficient C corresponding to the rotation angle factor Then, obtain the first transmission ratio P of the vehicle with the drive during the steering process r And the second transmission ratio of the ball screw Lead BNA ; Finally, calculate the basic assist torque T in , first gear ratio P r And the gear rack modification coefficient C factor The first product between the first product and the second gear ratio Lead BNA The ratio between them is taken as the steering torque T out The specific calculation formula is as follows:

[0065]

[0066] The precise steering torque calculated thus provides an accurate benchmark for friction compensation. Only by clearly understanding the expected steering torque under normal operating conditions can we accurately determine torque loss due to friction and implement targeted compensation. For example, if the calculated steering torque should be 100 N·m, but the actual perceived torque is only 80 N·m, then it can be determined that the 20 N·m loss is due to friction, allowing for compensation.

[0067] Furthermore, the present embodiment integrates multiple factors, including the rack and pinion displacement coefficient corresponding to the rotation angle, the first transmission ratio of the belt drive, and the second transmission ratio of the ball screw. This comprehensive consideration makes the calculated steering torque closer to the actual situation, thereby more accurately covering all influencing factors when performing friction compensation.

[0068] Step S102 , obtaining steering dynamic data of the vehicle during the steering process, and calculating the friction torque based on the steering dynamic data, the hand torque and the steering torque.

[0069] In an embodiment of the present application, during the vehicle's steering process, the steering dynamics data covers the vehicle's speed during the steering process and the steering wheel's rotation parameters. The vehicle's speed during the steering process refers to the vehicle's instantaneous speed when performing the steering operation. This speed data can be obtained through a speed sensor on the vehicle. For example, the speed sensor is installed in the wheel, transmission, or vehicle's electronic control unit (ECU). When the vehicle turns, the speed sensor detects the vehicle's speed in real time and transmits this data to the vehicle's control system.

[0070] Steering wheel rotation parameters include several aspects. The first is the steering wheel angle, which represents the rotation angle of the steering wheel relative to its initial position. This is typically measured by an angle sensor mounted on the steering column. For example, if the steering wheel is rotated 45 degrees clockwise from its initial position, this 45 degrees represents the current rotation angle. The second aspect is the steering wheel rotation speed, which is the rate of change of the steering wheel rotation angle. This can also be detected by relevant sensors. For example, if the steering wheel rotates 15 degrees in one second, the steering wheel rotation speed is 15 degrees / second.

[0071] In the embodiment of the present application, the friction torque is calculated based on the steering dynamic data, the hand torque and the steering torque, including the following steps B1-B5:

[0072] Step B1: comparing the hand torque with the hand torque limit, and comparing the steering torque with the steering torque limit.

[0073] Specifically, in mechanical systems, the magnitude of friction can be expressed using the formula F = μN. μ represents the coefficient of friction, reflecting characteristics such as the roughness of the contact surface; N is the normal pressure. For a steering system, the friction torque of the system does not continue to increase as the steering torque continues to increase. This is because when the steering torque increases to a certain amplitude, factors affecting the friction force, such as the friction coefficient and normal pressure, reach their limit state. For example, the roughness of the contact surface is fixed, and the normal pressure will not increase indefinitely, so the friction torque will no longer continue to increase with the increase in steering torque, but will remain unchanged.

[0074] Therefore, the hand torque and steering column assist torque are first low-pass filtered. Low-pass filtering removes high-frequency noise and interference from these two torque signals, retaining useful low-frequency information and making the signals smoother and more stable. The limiting module then limits the low-pass filtered hand torque and steering column assist torque. This involves comparing the hand torque with the hand torque limit, and the steering torque with the steering torque limit.

[0075] Step B2: If the hand torque is higher than the hand torque limit and the steering torque is higher than the steering torque limit, the hand torque is limited to obtain a limited hand torque, and the steering torque is limited to obtain a limited steering torque.

[0076] Specifically, when the hand torque detected is higher than the preset hand torque limit, the hand torque needs to be limited. For example, the set hand torque limit is 50N·m, and the actual hand torque detected is 60N·m. Figure 2 As shown in the figure, the hand torque is limited to the upper limit of 50 N·m through the limiting operation, resulting in the limited hand torque. Similarly, if the steering torque exceeds the preset steering torque limit, it is also limited. For example, if the steering torque limit is set to 80 N·m and the actual steering torque is 90 N·m, the steering torque is limited to 80 N·m after the limiting process, thus obtaining the limited steering torque.

[0077] Limiting torque values ​​within a specific range ensures safe and stable system operation, prevents excessive torque from damaging system components, or prevents exceeding the system's design tolerance, thereby safeguarding vehicle steering reliability and safety. For example, the limiting module limits hand torque to a range of -50N·m to 50N·m and steering column assist torque to a range of -30N·m to 30N·m. The hand torque and steering column assist torque obtained after limiting can be used to accurately calculate friction torque, providing accurate data support for system control and optimization.

[0078] Step B3: Calculate the system torque using the limited hand torque and the limited steering torque.

[0079] Specifically, the calculation formula of the system torque is as follows: T sum =T hw +T a , where T hw is the hand torque after limiting, T a is the steering torque after limiting. sum is the system torque.

[0080] Step B4: Acquire the vehicle's driving speed and steering wheel rotation parameters during the steering process based on the steering dynamics data.

[0081] Specifically, the vehicle's speed during the steering process and the steering wheel's rotation parameters are obtained from the steering dynamics data. The rotation parameters include the steering wheel's rotation angle, rotation speed, and the like.

[0082] Step B5: Calculate the friction torque using the driving speed, rotation parameters, and system torque.

[0083] Specifically, the friction torque is calculated using the driving speed, rotation parameters and system torque, including: obtaining the initial friction torque obtained during the calibration process, and superimposing the initial friction torque with the friction torque loss generated by the hand torque effect to obtain the compensation friction torque, and using the compensation friction torque as the second torque; obtaining the conversion coefficient corresponding to the driving speed and the first torque, wherein the first torque is generated by the phase lag of the motor and the mechanical friction of the reducer; calculating the difference between the system torque and the first torque, and calculating the second product between the difference and the conversion coefficient; calculating the sum of the second product and the second torque, and using the sum as the friction torque.

[0084] First, the friction torque is divided into two components: the learned friction torque value and the friction torque loss due to the hand torque effect. These components are then summed to obtain the compensation friction torque value. This is done because during calibration, when the steering wheel is lifted and the developer turns the steering wheel, the sum of the torque sensor and steering column assist torque recorded is used as the friction torque. However, this includes the hand torque, and the hand torque and friction torque are in the same direction. This makes the recorded value smaller than the actual friction torque, resulting in a certain torque loss. To improve driving feel and prevent the friction torque from being transmitted to the steering wheel, a friction compensation torque is required. This torque is applied by the motor to the steering column to offset the internal friction of the system. Therefore, the value recorded during calibration is used as the learned friction torque value, while the friction torque loss due to the hand torque effect must also be calculated.

[0085] At the beginning of a steering motion, the system's steering torque is relatively small and equal to the normal friction pressure. According to the Coulomb friction model, the friction torque increases linearly with increasing normal pressure. Furthermore, the hysteresis torque caused by hysteresis effects in sensors, ECUs, and motors must be taken into account to ultimately determine a relatively accurate friction torque.

[0086] The calculation formula of friction torque is as follows:

[0087] T f =k(T sum -T0)+T f0 , where T sum is the system torque, k is the conversion coefficient, T0 is the first torque, T f0 is the second moment.

[0088] It's important to note that the conversion coefficient k is speed-dependent, meaning its value varies at different speeds. This is because speed affects the various friction and resistance conditions in the steering system. For example, at low speeds, the friction between the tires and the road is greater, causing the steering system components to move relatively slowly, resulting in a higher friction coefficient and a larger k value. Conversely, at higher speeds, the friction between the tires and the road is reduced, allowing components to move more smoothly, reducing the friction coefficient and, consequently, the k value.

[0089] The first torque (also known as hysteresis torque) is also a calibration parameter that is closely related to vehicle speed. This first torque is typically caused by factors such as motor response delay, clearance between transmission components, and energy loss. The impact of these factors varies at different vehicle speeds. Generally speaking, at lower vehicle speeds, the motor and transmission system operate less efficiently, hysteresis is more pronounced, and the torque generated by hysteresis is greater. As vehicle speed increases, the system operates more smoothly, and the torque generated by hysteresis decreases.

[0090] As an example, when the driving speed is 50 km / h, the corresponding conversion coefficient is 0.8. By analyzing the characteristics of the motor and reducer, the first torque is determined to be 10 N·m. At the same time, the initial friction torque obtained during the calibration process is obtained and used as the second torque. Next, the specific calculation is performed. First, the difference between the system torque and the first torque is calculated. The system torque is the total torque generated by the entire steering system. For example, if the system torque is 50 N·m and the first torque is 10 N·m, the difference is 40 N·m. Then, the second product between this difference and the conversion coefficient is calculated. For example, if the difference is 40 N·m and the conversion coefficient is 0.8, the second product is 32 N·m. Finally, the sum of the second product and the second torque is calculated. For example, if the second product is 32 N·m and the second torque is 5 N·m, the sum is 37 N·m, which is used as the final friction torque.

[0091] Step S103: Obtain the friction compensation coefficient, and calculate the friction compensation torque using the friction compensation coefficient and the friction torque.

[0092] In this embodiment of the present application, the friction compensation coefficient is determined based on two factors: the rate of change of hand torque and the speed of the steering wheel. Furthermore, this embodiment provides two different methods for calculating this friction compensation coefficient. In specific application scenarios, you can use the calibration switch to select one of the calculation methods to calculate the friction compensation coefficient as needed.

[0093] In an embodiment of the present application, obtaining the friction compensation coefficient includes: obtaining the steering wheel speed during the steering process; querying the dynamic friction coefficient corresponding to the steering wheel speed and the static friction coefficient corresponding to the steering wheel speed; and obtaining the friction compensation coefficient based on the sum of the dynamic friction coefficient and the static friction coefficient.

[0094] Specifically, based on the Coulomb friction model, the steering wheel speed parameter is used to distinguish between static and kinetic friction. Therefore, a pre-established table can be used to find the normalized kinetic and static friction coefficients corresponding to the current steering wheel speed. For example, when the steering wheel speed is at a specific value, the corresponding kinetic friction coefficient is 0.2 and the static friction coefficient is 0.3. The kinetic and static friction coefficients are then added together to form the friction compensation coefficient.

[0095] As an example, if the current steering wheel speed is 10 degrees / second, the normalized dynamic friction coefficient is 0.15 and the static friction coefficient is 0.25, then the sum of the two is 0.15+0.25=0.4, and the friction compensation coefficient is 0.4.

[0096] The method provided in the embodiments of this application obtains the dynamic and static friction coefficients corresponding to the steering wheel speed and, by summing them, derives the friction compensation coefficient. This method can more accurately compensate for friction in the steering system, taking into account the friction characteristics at different speeds, making steering operations more precise and responsive, consistent with the driver's steering intent. It can also effectively reduce inconsistent or uncomfortable steering feel caused by changes in friction. The driver will experience a smoother and more natural steering experience, enhancing the driving experience.

[0097] In another embodiment of the present application, obtaining the friction compensation coefficient also includes: obtaining the rate of change of the hand torque of the vehicle during the steering process, and using the rate of change to query the corresponding rate of change of the friction compensation coefficient; comparing the current rotation angle of the steering wheel with the target rotation angle to obtain the positional relationship between the current rotation angle and the target rotation angle; obtaining the calculation strategy corresponding to the positional relationship and the last historical friction compensation coefficient, and calculating the historical friction compensation coefficient and the rate of change of the friction compensation coefficient according to the calculation strategy to obtain the friction compensation coefficient.

[0098] Specifically, during the vehicle's steering process, the driver's hand torque on the steering wheel will be continuously monitored. Through sensors and related technologies, the change in hand torque per unit time can be calculated, thereby obtaining the rate of change of hand torque. For example, if the hand torque increases from 20N·m to 30N·m within one second, the rate of change of hand torque is 10N·m / second. This rate of change is used to query a pre-set correspondence table or database to obtain the corresponding rate of change of the friction compensation coefficient. For example, when the rate of change is 10N·m / second, the rate of change of the friction compensation coefficient found is 0.5 / second.

[0099] At the same time, the current steering wheel angle is continuously acquired. For example, the current steering wheel angle is 45 degrees. The target angle is set based on specific driving requirements and vehicle conditions. For example, the target angle is 90 degrees. The current angle is then compared with the target angle to determine their positional relationship.

[0100] The calculation strategy for obtaining the corresponding position relationship includes the following: ① When the angular difference between the current steering wheel rotation angle and the target angle is greater than or equal to the first preset angle, the position relationship is that the steering wheel is far from the target angle. At this time, the hand torque needs to be increased to turn the steering wheel. To avoid a heavy feel, the friction compensation torque should be increased. ② When the angular difference between the current steering wheel rotation angle and the target angle is less than the first preset angle and greater than the second preset angle, the position relationship is that the steering wheel is close to the target angle. At this time, the hand torque needs to be reduced to reduce the steering wheel speed. At this time, the friction compensation torque should be reduced so that the hand torque does not decrease too much and cause an uneven feeling. ③ When the angular difference between the current steering wheel rotation angle and the target angle is less than or equal to the second preset angle, the hand torque remains unchanged to maintain the target angle. At this time, the friction compensation torque should also remain unchanged.

[0101] The historical friction compensation coefficient and the rate of change of the friction compensation coefficient are calculated according to the calculation strategy to obtain the friction compensation coefficient, including: ① When the position relationship is that the steering wheel is far away from the target angle, the friction compensation coefficient is: the sum of the historical friction compensation coefficient and the rate of change of the friction compensation coefficient. At this time, the product of the rate of change of the friction compensation coefficient and the rate of change of the hand torque is greater than 0. ② When the position relationship is that the steering wheel is close to the target angle, the friction compensation coefficient is: the difference between the historical friction compensation coefficient and the rate of change of the friction compensation coefficient. At this time, the product of the rate of change of the friction compensation coefficient and the rate of change of the hand torque is less than 0. ③ When the position relationship is that the steering wheel is close to the target angle, the friction compensation coefficient is equal to the historical friction compensation coefficient. At this time, the rate of change of the hand torque is 0.

[0102] The method provided in the embodiments of the present application calculates the friction compensation coefficient based on the relationship between the rate of change of hand torque and the position of the steering wheel. This method can provide personalized steering assistance compensation for drivers with different driving styles and operating habits, making the steering experience more tailored to the needs of each driver. At the same time, real-time acquisition of the rate of change of hand torque and steering wheel rotation angle information can more accurately determine the current steering state, thereby calculating a more precise friction compensation coefficient and achieving more refined steering control. In addition, by comparing the current rotation angle with the target rotation angle and using a corresponding calculation strategy, the steering process can be made smoother, avoiding sudden changes in steering assistance and improving driving comfort.

[0103] Step S104 , controlling the motor in the vehicle to perform torque compensation according to the friction compensation torque.

[0104] In the embodiments of this application, Figure 3 As shown in the figure, the friction compensation module outputs friction compensation torque, the basic power-assistance module outputs basic power-assistance torque, and the high-frequency power-assistance module outputs high-frequency power-assistance torque. Secondly, the friction compensation torque is superimposed with the basic power-assistance torque and high-frequency power-assistance torque to obtain a superimposed torque, and stability compensation is performed on the superimposed torque to improve its stability. The superimposed torque is then further superimposed with the torque obtained from other modules to ultimately generate a reference motor torque for the motor controller. The motor controller module receives the reference motor torque and controls the motor to output a steering torque according to the reference torque. The final output steering torque acts on the EPS physical system to realize the vehicle's steering operation.

[0105] In this way, by combining multiple modules to generate different types of torque, steering assistance can be more precisely adjusted and controlled. Friction compensation torque addresses the effects of friction, basic assist torque provides basic assistance, and high-frequency assist torque responds to rapidly changing conditions. This combined effect ensures more precise steering, meeting the driver's expectations. Furthermore, different driving conditions and road conditions require different steering assistance. This multi-module stacking approach allows for flexible adjustment of torque output based on various real-time changing factors, enhancing the system's adaptability and stability under varying operating conditions.

[0106] The method provided in the embodiment of the present application comprehensively considers the steering dynamics data of the vehicle during the steering process, the hand torque input by the driver, and the steering torque of the motor on the steering column, and can comprehensively and accurately calculate the friction torque. The entire calculation process fully considers the impact of various factors on the friction torque, thereby providing an accurate basis for subsequent compensation, effectively reducing or eliminating the interference with the return and damping functions caused by the friction of the EPS motor, reducer and mechanical system, improving the poor feel caused by the friction hysteresis effect, and enhancing the overall performance and driving experience of the EPS. In addition, it can adapt to various driving conditions and road conditions, and can provide optimal steering assistance and friction compensation whether it is high-speed driving or low-speed cornering.

[0107] Figure 4 FIG. 1 is a flow chart of a friction compensation control method for an electric power steering system according to an embodiment of the present invention. Figure 4 As shown, the process includes the following steps:

[0108] Step 1: Calculate the steering torque of the motor on the steering column based on the basic power assist and the steering wheel angle.

[0109] In this step, the basic power assist is a pre-calculated power assist value based on various vehicle operating parameters (such as vehicle speed, steering speed, etc.). The steering wheel angle is measured in real time by sensors installed in the steering system. The two parameters, basic power assist and steering wheel angle, are combined to calculate the steering torque applied by the motor to the steering column using a specific algorithm and calculation formula. For example, assuming the basic power assist is 50 N·m and the steering wheel angle is 45 degrees, the steering torque calculated through a certain functional relationship is 70 N·m.

[0110] Step 2: Limit the steering column power assist and hand torque, and calculate the hand torque change rate.

[0111] Limit the steering column power assist and hand torque. Limiting limits the values ​​of these two torques to a certain range to ensure they do not exceed the system's tolerance or reasonable range. For example, limit the steering column power assist to between 0 and 100 N·m, and the hand torque to between -50 and 50 N·m. Simultaneously, calculate the rate of change of the hand torque—the amount of change in hand torque per unit time. For example, if the hand torque changes from 20 N·m to 30 N·m in 1 second, the rate of change is 10 N·m / second.

[0112] Step 3: Considering the hysteresis effect, calculate the friction torque based on the hand torque, steering column assist torque, vehicle speed and steering wheel speed.

[0113] Hysteresis refers to a delay in the system's response relative to the input. When calculating friction torque, multiple factors, including hand torque, steering column torque, vehicle speed, and steering wheel speed, must be considered. Different vehicle speeds and steering wheel speeds result in different friction torques. For example, a slower vehicle speed and a faster steering wheel speed may result in a higher friction torque; whereas a faster vehicle speed and a slower steering wheel speed may result in a lower friction torque. Complex mathematical models and formulas are used to calculate the friction torque based on these parameters.

[0114] Step 4: Calculate the friction compensation coefficient based on the hand torque change rate or the steering wheel speed.

[0115] The friction compensation coefficient is calculated based on the rate of change of hand torque or steering wheel speed. This can be achieved using a pre-established mapping relationship or calculation formula. For example, when the rate of change of hand torque is large or the steering wheel speed is fast, the friction compensation coefficient may be set to 0.8; when the rate of change of hand torque is small or the steering wheel speed is slow, the friction compensation coefficient may be set to 0.2.

[0116] Step 5: Calculate the friction compensation torque based on the friction compensation coefficient and the friction compensation torque.

[0117] Finally, the final friction compensation torque is calculated based on the previously calculated friction compensation coefficient and the predetermined friction compensation torque calculation method. For example, if the friction compensation coefficient is 0.5, the predetermined friction compensation torque calculation method is to multiply the hand torque by 2, and the current hand torque is 30 N·m, then the friction compensation torque is 0.5×(2×30)=30 N·m.

[0118] This embodiment also provides a friction compensation control device for an electric power steering system, which is used to implement the above-mentioned embodiments and preferred embodiments. Details already described will not be repeated here. As used below, the term "module" may refer to a combination of software and / or hardware that implements a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation using hardware, or a combination of software and hardware, is also possible and contemplated.

[0119] This embodiment provides a friction compensation control device for an electric power steering system, such as Figure 5 Shown, including:

[0120] A detection module 601 is used to detect the hand torque generated by the driver turning the steering wheel during the steering process of the vehicle, and obtain the steering torque applied by the motor in the vehicle to the steering column during the steering process;

[0121] An acquisition module 602 is configured to acquire steering dynamic data of the vehicle during steering, and calculate friction torque based on the steering dynamic data, hand torque, and steering torque;

[0122] A calculation module 603 is used to obtain a friction compensation coefficient and calculate a friction compensation torque using the friction compensation coefficient and the friction torque;

[0123] The control module 604 is used to control the motor in the vehicle to perform torque compensation according to the friction compensation torque.

[0124] In an embodiment of the present application, the detection module 601 is used to obtain the basic power torque provided by the motor for the electric power steering system, and to obtain the rotation angle of the steering wheel during the steering process; and to calculate the steering torque of the motor on the steering column during the steering process using the rotation angle of the steering wheel and the basic power torque.

[0125] In an embodiment of the present application, the detection module 601 is specifically used to obtain the gear rack displacement coefficient corresponding to the rotation angle; obtain the first transmission ratio of the belt drive and the second transmission ratio of the ball screw during the steering process of the vehicle; calculate the first product between the basic assist torque, the first transmission ratio and the gear rack displacement coefficient, and use the ratio between the first product and the second transmission ratio as the steering torque.

[0126] In an embodiment of the present application, an acquisition module 602 is used to obtain and compare the hand torque with the hand torque limit, and to compare the steering torque with the steering torque limit; if the hand torque is higher than the hand torque limit, and the steering torque is higher than the steering torque limit, the hand torque is limited to obtain the limited hand torque, and the steering torque is limited to obtain the limited steering torque; the system torque is calculated using the limited hand torque and the limited steering torque; the vehicle's driving speed and the steering wheel rotation parameters during the steering process are obtained based on the steering dynamic data; and the friction torque is calculated using the driving speed, rotation parameters and system torque.

[0127] In an embodiment of the present application, the acquisition module 602 is used to obtain the initial friction torque obtained during the calibration process, and use the initial friction torque and the friction torque loss generated by the hand torque effect to superimpose to obtain the compensation friction torque, and use the compensation friction torque as the second torque; obtain the conversion coefficient corresponding to the driving speed and the first torque, wherein the first torque is generated by the phase lag of the motor and the mechanical friction of the reducer; calculate the difference between the system torque and the first torque, and calculate the second product between the difference and the conversion coefficient; calculate the sum of the second product and the second torque, and use the sum as the friction torque.

[0128] In an embodiment of the present application, the calculation module 603 is used to obtain the steering wheel speed during the steering process; query the dynamic friction coefficient corresponding to the steering wheel speed and the static friction coefficient corresponding to the steering wheel speed; and obtain the friction compensation coefficient based on the sum of the dynamic friction coefficient and the static friction coefficient.

[0129] In an embodiment of the present application, the calculation module 603 is used to obtain the rate of change of the hand torque of the vehicle during the steering process, and use the rate of change to query the corresponding rate of change of the friction compensation coefficient; compare the current rotation angle of the steering wheel with the target rotation angle to obtain the positional relationship between the current rotation angle and the target rotation angle; obtain the calculation strategy corresponding to the positional relationship and the last historical friction compensation coefficient, and calculate the historical friction compensation coefficient and the rate of change of the friction compensation coefficient according to the calculation strategy to obtain the friction compensation coefficient.

[0130] See also Figure 6 , Figure 6 is a structural diagram of an electronic device provided by an optional embodiment of the present invention, such as Figure 6As shown, the electronic device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. The various components utilize different buses to communicate with each other and can be installed on a common mainboard or installed in other ways as needed. The processor can process instructions executed in the electronic device, including instructions stored in or on the memory to display graphical information of a GUI on an external input / output device (such as a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple electronic devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system).

[0131] The processor 10 may be a central processing unit, a network processor, or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit, a programmable logic device, or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic, or any combination thereof.

[0132] The memory 20 stores instructions that can be executed by at least one processor 10, so that the at least one processor 10 executes the method shown in the above embodiment.

[0133] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created based on the use of an electronic device presented by a small program landing page, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely located relative to the processor 10, and these remote memories may be connected to the electronic device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0134] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0135] The electronic device further includes a communication interface 30 for the electronic device to communicate with other devices or a communication network.

[0136] The embodiment of the present invention also provides a computer-readable storage medium. The above-mentioned method according to the embodiment of the present invention can be implemented in hardware, firmware, or implemented as a computer code that can be recorded in a storage medium, or implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and downloaded through a network and will be stored in a local storage medium, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state drive, etc.; further, the storage medium can also include a combination of the above-mentioned types of memory. It can be understood that a computer, a processor, a microprocessor controller or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor or hardware, the method shown in the above embodiment is implemented.

[0137] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A friction compensation control method for an electric power steering system, characterized in that: The method comprises: detecting a hand torque generated by a driver turning a steering wheel during a steering process of the vehicle, and obtaining a steering torque applied by a motor in the vehicle to a steering column during the steering process; Acquiring steering dynamic data of the vehicle during a steering process, and calculating a friction torque based on the steering dynamic data, the hand torque, and the steering torque; Obtaining a friction compensation coefficient, and calculating a friction compensation torque using the friction compensation coefficient and the friction torque; controlling a motor in the vehicle to perform torque compensation according to the friction compensation torque; Obtaining the steering torque of the motor in the vehicle on the steering column during the steering process includes: obtaining a basic power-assisting torque provided by the motor for the electric power steering system and obtaining a rotation angle of the steering wheel during the steering process; and calculating the steering torque of the motor on the steering column during the steering process using the rotation angle of the steering wheel and the basic power-assisting torque; The method of calculating the steering torque of the motor on the steering column during the steering process by using the rotation angle of the steering wheel and the basic power-assisting torque includes: obtaining the gear rack displacement coefficient corresponding to the rotation angle; obtaining the first transmission ratio of the belt drive and the second transmission ratio of the ball screw during the steering process of the vehicle; calculating a first product among the basic power-assisting torque, the first transmission ratio and the gear rack displacement coefficient, and using the ratio between the first product and the second transmission ratio as the steering torque.

2. The method according to claim 1, characterized in that The calculating of the friction torque based on the steering dynamics data, the hand torque and the steering torque includes: comparing the hand torque with a hand torque limit, and comparing the steering torque with a steering torque limit; If the hand torque is higher than the hand torque limit, and the steering torque is higher than the steering torque limit, limiting the hand torque to obtain a limited hand torque, and limiting the steering torque to obtain a limited steering torque; Calculating a system torque using the limited hand torque and the limited steering torque; acquiring a driving speed of the vehicle during the steering process and a rotation parameter of the steering wheel based on the steering dynamics data; The friction torque is calculated using the driving speed, the rotational parameter, and the system torque.

3. The method according to claim 2, characterized in that The calculating the friction torque by using the driving speed, the rotation parameter, and the system torque includes: Obtaining an initial friction torque obtained during the calibration process, and superimposing the initial friction torque with the friction torque loss caused by the hand torque effect to obtain a compensation friction torque, and using the compensation friction torque as the second torque; Obtaining a conversion coefficient and a first torque corresponding to the driving speed, wherein the first torque is generated by a phase lag of the motor and mechanical friction of the reducer; Calculating a difference between the system torque and the first torque, and calculating a second product between the difference and the conversion coefficient; A sum of the second product and the second torque is calculated, and the sum is used as the friction torque.

4. The method according to claim 1, wherein The obtaining of the friction compensation coefficient includes: Obtaining a steering wheel speed during the steering process; querying a dynamic friction coefficient corresponding to the steering wheel speed and a static friction coefficient corresponding to the steering wheel speed; The friction compensation coefficient is obtained based on the sum of the dynamic friction coefficient and the static friction coefficient.

5. The method according to claim 1, wherein The obtaining of the friction compensation coefficient includes: Obtaining a rate of change of the hand torque during the steering process of the vehicle, and using the rate of change to query a corresponding rate of change of the friction compensation coefficient; Comparing a current rotation angle of the steering wheel with a target rotation angle to obtain a positional relationship between the current rotation angle and the target rotation angle; A calculation strategy corresponding to the positional relationship and a previous historical friction compensation coefficient are obtained, and the historical friction compensation coefficient and the friction compensation coefficient change rate are calculated according to the calculation strategy to obtain the friction compensation coefficient.

6. A friction compensation control device for an electric power steering system, characterized in that: The device comprises: a detection module, configured to detect a hand torque generated by a driver turning a steering wheel during a steering process of the vehicle, and obtain a steering torque applied by a motor in the vehicle to a steering column during the steering process; an acquisition module, configured to acquire steering dynamic data of the vehicle during a steering process, and calculate a friction torque based on the steering dynamic data, the hand torque, and the steering torque; a calculation module, configured to obtain a friction compensation coefficient and calculate a friction compensation torque using the friction compensation coefficient and the friction torque; a control module, configured to control a motor in the vehicle to perform torque compensation according to the friction compensation torque; The detection module is configured to obtain a basic power-assisting torque provided by the motor for the electric power steering system and a rotation angle of the steering wheel during the steering process; and calculate a steering torque applied by the motor to the steering column during the steering process using the rotation angle of the steering wheel and the basic power-assisting torque; The detection module is used to obtain the gear rack modification coefficient corresponding to the rotation angle; obtain the first transmission ratio of the belt drive and the second transmission ratio of the ball screw during the steering process of the vehicle; calculate the first product between the basic assist torque, the first transmission ratio and the gear rack modification coefficient, and use the ratio between the first product and the second transmission ratio as the steering torque.

7. An electronic device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method according to any one of claims 1 to 5 by executing the computer instructions.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method according to any one of claims 1 to 5.

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