Method, device, equipment, medium and program product for determining vehicle power assist curve

Abstract

The present application discloses a method, apparatus, device and storage medium for determining a vehicle power assist curve, the method comprising: obtaining the maximum input torque of a vehicle's steering wheel, the maximum power assist torque of a vehicle's motor, a vehicle speed sensing function and a power assist dead zone torque of the vehicle; determining a first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque; determining a second power assist curve of the vehicle based on the maximum input torque, the maximum power assist torque of the vehicle's motor, the vehicle speed sensing function and the power assist dead zone torque of the vehicle; and determining the first power assist curve and the second power assist curve as the vehicle power assist curve.

Description

Technical Field

[0001] The present application relates to the field of automotive electric power steering systems, and in particular to a method, device, equipment and storage medium for determining a vehicle power steering curve. Background Art

[0002] With the development of power steering systems, drivers can more easily control vehicle steering while achieving functions such as basic speed-dependent power assistance, damping compensation, and active self-centering. Basic speed-dependent power assistance is a key technology in Electric Power Steering (EPS). It relies primarily on the hand torque collected by the torque sensor and the current vehicle speed collected by the speed sensor, combined with a speed-dependent power assistance curve table to obtain the desired target current. The target voltage signal is then output to the power assist motor through a current controller and a pulse width modulation (PWM) controller. The power assist motor then generates a corresponding power assist torque to the lower end of the steering column, assisting the driver in controlling the vehicle's steering.

[0003] The vehicle's power-assistance curve determines the strategy used by the Electronic Control Unit (ECU) to output the appropriate power-assistance current to meet the required power-assistance torque at a specific vehicle speed and hand torque. Currently, common methods for determining vehicle power-assistance curves are complex, with numerous curve parameters, making parameter tuning difficult and hindering real-vehicle or test bench testing. Summary of the Invention

[0004] The embodiments of the present application provide a method, apparatus, device, and storage medium for determining a vehicle power assist curve, which can reduce the complexity of determining the vehicle power assist curve.

[0005] The technical solution of this application is achieved as follows:

[0006] An embodiment of the present application provides a method for determining a vehicle power assist curve, the method comprising:

[0007] Obtaining a maximum input torque of a vehicle's steering wheel, a maximum power-assistance torque of a motor of the vehicle, a vehicle speed sensing function of the vehicle, and a power-assistance dead-band torque of the vehicle; wherein the vehicle speed sensing function is used to characterize the relationship between the vehicle speed and the vehicle speed sensing coefficient;

[0008] determining a first power assist curve for the vehicle based on the vehicle speed sensing function and the maximum power assist torque; wherein the first power assist curve is used to represent a relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque;

[0009] determining a second power assist curve for the vehicle based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, a vehicle speed sensing function, and a power assist dead-band torque of the vehicle; wherein the second power assist curve is used to represent a relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead-band torque and less than or equal to the maximum input torque;

[0010] The first power assist curve and the second power assist curve are determined as a vehicle power assist curve.

[0011] In this way, during the process of determining the vehicle power-assistance curve, different power-assistance curves can be determined based on the different ranges of the input torque, that is, the first power-assistance curve and the second power-assistance curve are determined as the vehicle power-assistance curve, thereby improving the accuracy of determining the vehicle power-assistance curve. Furthermore, in the embodiment of the present application, the vehicle power-assistance curve of the vehicle can be accurately calibrated by using the maximum input torque of the vehicle's steering wheel, the maximum power-assistance torque of the vehicle's motor, the vehicle's speed sensing function, and the parameters with less power-assistance dead zone torque of the vehicle, thereby reducing the complexity of determining the vehicle power-assistance curve and facilitating parameter tuning and actual vehicle or test bench testing.

[0012] Further, in an embodiment of the present application, the second power assist curve of the vehicle is determined based on the maximum input torque, the maximum power assist torque of the vehicle's motor, the vehicle's speed sensing function, and the vehicle's power assist dead zone torque, including: determining a sinusoidal power assist function based on the current input torque, the power assist dead zone torque, and the maximum input torque; and determining the product of the sinusoidal power assist function, the vehicle speed sensing function, and the maximum power assist torque as the second power assist curve of the vehicle.

[0013] In this way, a sinusoidal power assist function can be determined based on the current input torque, the power assist dead zone torque, and the maximum input torque. Due to its inherent curve characteristics, the sinusoidal power assist function can meet the requirements of both concave front and convex rear. Furthermore, the sinusoidal power assist function can be calibrated using only three parameters: the current input torque, the power assist dead zone torque, and the maximum input torque. The second power assist curve for the vehicle is then determined by multiplying the sinusoidal power assist function, the vehicle speed sensing function, and the maximum power assist torque, thus reducing the complexity of determining the power assist curve.

[0014] Further, in an embodiment of the present application, determining the first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque includes: determining the product of the vehicle speed sensing function and the maximum power assist torque as the first power assist curve of the vehicle.

[0015] In this way, the product of the vehicle speed sensing function and the maximum assist torque is determined as the vehicle's first assist curve. When the current input torque of the steering wheel is large and the vehicle speed is constant, the motor can be controlled to output a fixed assist torque through the first assist curve, so that the motor will not be overloaded.

[0016] Furthermore, in an embodiment of the present application, the method also includes: determining the maximum input torque of the steering wheel of the vehicle based on the tangential force of the steering wheel of the vehicle and the radius of the steering wheel of the vehicle; determining the maximum power assist torque of the motor of the vehicle based on the maximum steering resistance torque of the vehicle and the maximum input torque; determining the speed sensing function of the vehicle based on multiple test speeds of the vehicle; and determining the power assist dead zone torque of the vehicle based on the electric power steering conditions.

[0017] In this way, the maximum steering wheel input torque is determined based on the vehicle's steering wheel tangential force and the vehicle's steering wheel radius; the maximum assist torque of the vehicle's motor is determined based on the vehicle's maximum steering resistance torque and maximum input torque; the vehicle's speed sensing function is determined based on multiple test vehicle speeds; and the vehicle's assist dead zone torque is determined based on the electric power steering conditions. In this way, the parameters used to calibrate the vehicle's assist curve can be accurately determined.

[0018] Further, in an embodiment of the present application, the speed sensing function of the vehicle is determined based on multiple test speeds of the vehicle, including: for each test speed of the vehicle, adjusting the speed sensing coefficient of the vehicle at the test speed until the input torque of the steering wheel of the vehicle is a preset expected operating torque, and determining the current speed sensing coefficient as the speed sensing coefficient corresponding to the test speed; and determining the speed sensing function of the vehicle based on the speed sensing coefficients corresponding to the multiple test speeds of the vehicle.

[0019] In this way, the speed sensitivity coefficient is adjusted for each test speed until the vehicle's steering wheel input torque reaches the preset desired steering torque. The current speed sensitivity coefficient is then determined as the speed sensitivity coefficient corresponding to the test speed. Finally, the vehicle's speed sensitivity function is determined based on the speed sensitivity coefficients corresponding to the multiple test speeds. This allows the relationship between the vehicle's real-time speed and the speed sensitivity coefficient to be accurately determined.

[0020] Further, in an embodiment of the present application, the maximum power assist torque of the vehicle's motor is determined based on the maximum steering resistance torque of the vehicle and the maximum input torque, including: determining the vehicle's in-place steering resistance torque based on the friction coefficient between the vehicle's tires and the ground, the front axle load of the vehicle's tires, and the air pressure of the vehicle's tires; determining the maximum steering resistance torque based on the in-place steering resistance torque, the steering system's rotation ratio, and the positive efficiency of the rack and pinion steering gear; and determining the difference between the maximum steering resistance torque and the maximum input torque as the maximum power assist torque of the vehicle's motor.

[0021] In this way, the vehicle's stationary steering torque is first determined based on the friction coefficient between the vehicle's tires and the ground, the front axle load of the vehicle's tires, and the tire pressure of the vehicle. The maximum steering torque is then determined based on the stationary steering torque, the steering system's turning ratio, and the positive efficiency of the rack and pinion steering gear. Finally, the difference between the maximum steering torque and the maximum input torque is determined as the maximum assist torque of the vehicle's motor. This improves the accuracy of determining the maximum assist torque of the vehicle's motor.

[0022] Furthermore, in an embodiment of the present application, the method further includes: determining the steering wheel assist torque based on the current speed of the vehicle and the current input torque of the steering wheel using the vehicle assist curve;

[0023] The product of the electromagnetic torque coefficient of the power-assisting motor and the transmission ratio of the reduction mechanism is determined as the power-assisting linear coefficient; the power-assisting torque is divided by the power-assisting linear coefficient to determine the power-assisting current; wherein, the power-assisting torque is linearly related to the power-assisting current; based on the power-assisting current, the response torque of the motor is determined.

[0024] In this way, the steering wheel assist torque is determined based on the vehicle's current speed and the steering wheel's current input torque using the vehicle assist curve. The assist linear coefficient is determined by multiplying the electromagnetic torque coefficient of the assist motor and the transmission ratio of the reduction mechanism. The assist current is then determined as the quotient of the assist torque and the assist linear coefficient. The motor's response torque is then determined based on the assist current. In this way, after determining the assist torque corresponding to the vehicle speed and current input torque using the vehicle assist, the assist current corresponding to the assist torque can be determined first, and finally, the motor response torque corresponding to the assist current can be determined. This ensures that the motor outputs a response torque that matches the vehicle speed and current input torque.

[0025] An embodiment of the present application provides a device for determining a vehicle power-assistance curve, the device comprising:

[0026] an acquisition unit, configured to acquire a maximum input torque of a steering wheel of a vehicle, a maximum power-assistance torque of a motor of the vehicle, a vehicle speed sensing function of the vehicle, and a power-assistance dead-zone torque of the vehicle; wherein the vehicle speed sensing function is used to characterize a relationship between the vehicle speed and a vehicle speed sensing coefficient;

[0027] A determination unit is used to determine a first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque; wherein the first power assist curve is used to characterize the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque; a second power assist curve of the vehicle is determined based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, the vehicle speed sensing function of the vehicle and the power assist dead zone torque of the vehicle; wherein the second power assist curve is used to characterize the relationship between the current input torque and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead zone torque and is less than or equal to the maximum input torque; the first power assist curve and the second power assist curve are determined as vehicle power assist curves.

[0028] An embodiment of the present application provides a device for determining a vehicle power assist curve, the device comprising: a processor and a storage medium storing executable instructions, the storage medium relying on the processor to perform operations via a communication bus, and when the executable instructions are executed by the processor, the method for determining the vehicle power assist curve described in one or more of the above-mentioned embodiments is executed.

[0029] An embodiment of the present application provides a computer storage medium storing executable instructions. When the executable instructions are executed by a processor, the processor executes the method for determining a vehicle power assistance curve as described in one or more embodiments.

[0030] An embodiment of the present application provides a computer program product, including a computer program or instructions. When the computer program or instructions are executed by a processor, the method for determining a vehicle power assist curve as described in one or more embodiments is performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a method for determining a vehicle power assist curve provided in an embodiment of the present application Figure 1 ;

[0032] Figure 2 A schematic diagram of a method for determining a vehicle power assist curve provided in an embodiment of the present application Figure 2 ;

[0033] Figure 3A system architecture block diagram of an electric power steering system provided in an embodiment of the present application;

[0034] Figure 4 A schematic diagram of a method for determining a vehicle power assist curve provided in an embodiment of the present application Figure 3 ;

[0035] Figure 5 A schematic diagram of a strategy for controlling a steering mechanism provided in an embodiment of the present application;

[0036] Figure 6 A vehicle power assist curve diagram provided in an embodiment of the present application;

[0037] Figure 7 A three-dimensional assist torque search diagram provided in an embodiment of the present application;

[0038] Figure 8 A linear power assist curve diagram in the related art provided in the embodiments of this application;

[0039] Figure 9 A broken line power assistance curve diagram in the related art provided in the embodiments of this application;

[0040] Figure 10 A curved power assist curve diagram in the related art provided in the embodiments of this application;

[0041] Figure 11 A schematic diagram of the vehicle speed sensing function fitting provided in an embodiment of the present application;

[0042] Figure 12 A schematic diagram of the structure of a device for determining a vehicle power assist curve provided in an embodiment of the present application;

[0043] Figure 13 A schematic diagram of the composition structure of a vehicle power assist curve determination device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions of this application are further elaborated in detail below with reference to the accompanying drawings and embodiments. The described embodiments should not be regarded as limiting this application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0046] The terms "first / second / third" involved are merely to distinguish similar vehicles and do not represent a specific order for the vehicles. It is understandable that "first / second / third" can be interchanged with the specific order or sequence where permitted so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing this application only and are not intended to limit this application.

[0048] With the development of power steering systems, EPS (Electronic Steering System) has added many auxiliary mechanisms compared to traditional mechanical steering systems, including power steering motors, worm gear reducers, ECUs, and various sensors (vehicle speed sensor, torque sensor, current sensor). With EPS, drivers can more easily control the vehicle's steering, while also realizing basic speed-dependent power assistance, damping compensation, and active self-centering functions.

[0049] The torque sensor and angle sensor in the electric power steering mechanism are mounted on the steering column. They measure the torque and deformation applied by the steering wheel to the upper end of the steering column and transmit the calculated torque and angle to the ECU. A vehicle speed sensor, also known as a wheel speed sensor, is installed at each wheel and transmits the calculated current vehicle speed to the ECU. In the commonly used column-type electric power steering (C-EPS) system, the power assist motor is mounted on the steering column and, through a worm gear reduction mechanism, outputs the reduced torque to the steering column to assist in steering the vehicle. The power assist motor also transmits the current flowing through it to the ECU. The rack-and-pinion steering gear converts the torque increased by the power assist motor into rack axial force, which is then applied to the steering wheel via a lateral tie rod, thereby determining the vehicle's power assist curve. The ECU receives the torque and angle from the steering wheel, as well as the current vehicle speed at the wheel end, to determine the current steering system state, including basic speed-dependent assist, damping control, or self-centering control. Considering the state of speed-dependent power assistance, the vehicle power assistance curve is found according to the torque and speed to obtain the corresponding power assistance current, which is converted into an electrical signal and then outputted through the PWM controller to the corresponding power assistance voltage. Then, according to the internal control strategy, the commonly used ones are Proportional-Integral-Derivative (PID) control, fuzzy PID control and extended Kalman filter algorithm, the current signal sent by the motor and the expected current signal are closed-loop controlled to ensure that the current current is equal to the expected current.

[0050] Currently, the commonly used straight-line, broken-line, and curved vehicle power-assistance curves fail to meet the requirement for a power-assistance curve that is concave at the front and convex at the rear. This requirement requires that when the steering wheel angle is small, the power-assistance torque provided by the power-assistance motor increases with the rate of change of the angle, resulting in a concave image on the power-assistance curve. At larger steering wheel angles, for safety reasons, the power-assistance torque provided by the power-assistance motor should decrease with the rate of change of the angle, resulting in a convex image. Furthermore, when the power-assistance torque reaches saturation, the rate of change is large, which affects the feel within a certain range of hand torque, thereby reducing the accuracy of the vehicle power-assistance curve.

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0052] The embodiments of the present application propose a method for determining a vehicle power assist curve. By determining the power assist curve using the method for determining a vehicle power assist curve proposed in the embodiments of the present application, the accuracy of determining the vehicle power assist curve can be improved.

[0053] Furthermore, in the embodiments of the present application, Figure 1 A schematic diagram of a method for determining a vehicle power assist curve provided in an embodiment of the present application Figure 1 ,like Figure 1 As shown, the method for determining the vehicle power assist curve may include the following steps:

[0054] S101: Obtain the maximum input torque of the vehicle's steering wheel, the maximum power-assistance torque of the vehicle's motor, the vehicle's speed sensing function, and the vehicle's power-assistance dead-zone torque; wherein the speed sensing function is used to characterize the relationship between the vehicle's speed and the vehicle's speed sensing coefficient.

[0055] Here, the maximum input torque of the vehicle's steering wheel is the input torque applied to the steering wheel by the vehicle's driver, so the maximum input torque is limited by the driver's physical strength. In an embodiment of the present application, the maximum input torque can be obtained based on the tangential force applied by the driver to the steering wheel and the radius of the steering wheel. For example, when the tangential force applied by the driver to the steering wheel is generally 15-50 N·m and the radius of the steering wheel is generally 0.2m, the maximum input torque of the steering wheel is 3-10 N·m. In some embodiments, the maximum input torque can be determined based on the driver's driving habits. For example, the maximum input torque of the steering wheel can be set to 7 N·m.

[0056] The maximum assist torque of the vehicle's motor corresponds to the maximum input torque of the vehicle's steering wheel. That is, when the steering wheel input torque is the maximum data torque, the assist torque output by the vehicle's motor is the maximum assist torque of the vehicle's motor. In some embodiments, when the drag torque is the highest during a stationary turn, the assist torque provided by the motor is the maximum assist torque.

[0057] In the embodiment of the present application, the vehicle speed sensing function can be determined based on different vehicle speeds and the corresponding vehicle speed sensing coefficients. For example, a fitting algorithm can be used to fit different vehicle speeds and the corresponding vehicle speed sensing coefficients to obtain a vehicle speed sensing function that represents the relationship between the vehicle speed and the vehicle speed sensing coefficient.

[0058] In an embodiment of the present application, the vehicle's power-assisted dead-zone torque may be a preset value, and the power-assisted dead-zone torque may determine the vehicle's driving comfort. When the power-assisted dead-zone torque is large, the driver will only output the power-assisted torque when applying a large torque, which will increase the driver's driving intensity and is not in line with the original design intention of the EPS. When the vehicle's power-assisted dead-zone torque is small, steering wheel rotations caused by slight impacts on the road surface will generate power assistance, causing the driver to lose road feel and a sense of the vehicle's center position, which is very dangerous at high speeds. At the same time, an overly sensitive control system will also increase the operating burden of the motor and shorten the motor's service life. For example, the vehicle's power-assisted dead-zone torque may be set to 1 N·m.

[0059] S102: Determine a first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque.

[0060] Here, the first assist curve is used to represent the relationship between the current input torque of the steering wheel and the current assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque.

[0061] In an embodiment of the present application, when determining the first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque, the vehicle power assist curve determination device may determine the product of the vehicle speed sensing function and the maximum power assist torque as the first power assist curve of the vehicle.

[0062] It will be appreciated that when the vehicle speed is constant, the speed sensing function is a fixed value, and the maximum assist torque is also a fixed value, so the first assist curve can be a straight line. In other words, when the vehicle speed is constant and the current steering wheel input torque is greater than the maximum input torque, the current assist torque output by the motor does not change due to changes in the current steering wheel input torque.

[0063] S103 : Determine a second power assist curve of the vehicle based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, the vehicle speed sensing function, and the power assist dead zone torque of the vehicle.

[0064] The second power assist curve is used to represent the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead zone torque and less than or equal to the maximum input torque.

[0065] Furthermore, in an embodiment of the present application, when determining the second power assist curve of the vehicle based on the maximum input torque, the maximum power assist torque of the vehicle's motor, the vehicle's speed sensing function and the vehicle's power assist dead zone torque, a sinusoidal power assist function can be determined based on the current input torque, the power assist dead zone torque and the maximum input torque; the product of the sinusoidal power assist function, the vehicle speed sensing function and the maximum power assist torque is determined as the second power assist curve of the vehicle.

[0066] In an embodiment of the present application, the sinusoidal assist function may include the current input torque, the assist dead zone torque and the maximum input torque. Therefore, the sinusoidal assist function determined by the sinusoidal function can meet the requirements of the assist curve being concave at the front and convex at the back.

[0067] It can be understood that the requirement of the power assist curve being concave at the front and convex at the back means that when the current input torque of the steering wheel is greater than the power assist dead zone torque and less than or equal to the maximum input torque, the input torque can be considered to be in the power assist section, that is, when the input torque is in a smaller range, the power assist torque should change faster with the input torque, and when the input torque is larger, the change of the power assist torque with the input torque should become slower.

[0068] S104: Determine the first power assist curve and the second power assist curve as a vehicle power assist curve.

[0069] In an embodiment of the present application, after determining the second power assist curve of the vehicle based on the maximum input torque, the maximum power assist torque of the vehicle's motor, the vehicle's speed sensing function, and the vehicle's power assist dead zone torque, the vehicle power assist curve determination device can determine the first power assist curve and the second power assist curve as the vehicle power assist curve.

[0070] In an embodiment of the present application, the vehicle power assist curve may include: a first power assist curve and a second power assist curve.

[0071] In some embodiments, the vehicle power assist curve may further include a third assistant curve, wherein the third assistant curve is used to characterize the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is less than or equal to the power assist dead zone torque.

[0072] In the embodiment of the present application, the third assistant curve is a straight line, and the third assistant curve indicates that when the current input torque of the steering wheel is less than or equal to the assist dead zone torque, the current assist torque of the motor is 0.

[0073] In an embodiment of the present application, during the determination of the vehicle power-assistance curve, different power-assistance curves can be determined based on the different ranges of the input torque, i.e., the first power-assistance curve and the second power-assistance curve are determined as the vehicle power-assistance curve, thereby improving the accuracy of the determination of the vehicle power-assistance curve. Furthermore, in an embodiment of the present application, the vehicle power-assistance curve of the vehicle can be accurately calibrated by using the maximum input torque of the vehicle's steering wheel, the maximum power-assistance torque of the vehicle's motor, the vehicle's speed sensing function, and the parameters with less power-assistance dead-zone torque of the vehicle, thereby reducing the complexity of determining the vehicle power-assistance curve and facilitating parameter setting and actual vehicle or test bench testing.

[0074] In some embodiments, the above S103 can be implemented through S201 and S202:

[0075] S201 : Determine a sinusoidal power assist function based on the current input torque, the power assist dead-band torque, and the maximum input torque.

[0076] It's understandable that when the steering wheel's current input torque is small (i.e., less than or equal to the power assist dead zone torque) or large (greater than the maximum input torque), the vehicle's motor's current power assist torque remains fixed. In other words, the front and rear curves of the second assist curve are both straight lines. Therefore, to ensure a completely smooth power assist curve and enhance driver feel, the second assist curve, which connects the front and rear curves, must be concave at the front and convex at the rear. While smooth power assist curves are possible in related technologies, the curves have numerous undetermined parameters, making their determination more complex.

[0077] In this embodiment, a sinusoidal power assist function can be determined based on the current input torque, the power assist dead zone torque, and the maximum input torque. Due to its inherent curve characteristics, the sinusoidal function can meet the requirements of concave at the front and convex at the back. Furthermore, the curve can be calibrated using only three parameters: the current input torque, the power assist dead zone torque, and the maximum input torque, thus reducing the complexity of determining the power assist curve.

[0078] In some embodiments, the above-mentioned sinusoidal boost function can be implemented by formula (1):

[0079]

[0080] Among them, T d is the current input torque, T d0 To assist dead zone torque, T dmax is the maximum input torque.

[0081] S202: Determine the product of the sinusoidal power assist function, the vehicle speed sensing function, and the maximum power assist torque as a second power assist curve for the vehicle.

[0082] The second power assist curve can be realized by formula (2):

[0083]

[0084] Among them, k(v) is the vehicle speed sensing function, T amax For maximum assist torque.

[0085] In this embodiment of the present application, a sinusoidal power assist function can be determined based on the current input torque, the power assist dead zone torque, and the maximum input torque. Due to its inherent curve characteristics, the sinusoidal power assist function can meet the requirements of concave front and convex rear. Furthermore, the sinusoidal power assist function can be calibrated using only three parameters: the current input torque, the power assist dead zone torque, and the maximum input torque. The second power assist curve for the vehicle is then determined by multiplying the sinusoidal power assist function, the vehicle speed sensing function, and the maximum power assist torque, thereby reducing the complexity of determining the power assist curve.

[0086] In some embodiments, the above S102 may be implemented by S301:

[0087] S301: Determine the product of the vehicle speed sensing function and the maximum power assist torque as a first power assist curve of the vehicle.

[0088] The first power assist curve of the vehicle can be realized by formula (3):

[0089] k(v)T amax Formula (3);

[0090] Among them, k(v) is the vehicle speed sensing function, T amax For maximum assist torque.

[0091] As can be seen from formula (3), when the current steering wheel input torque is large (i.e., greater than the maximum input torque), the current assist torque output by the motor is related to the vehicle speed, the only variable in formula (3). In some embodiments, the vehicle speed sensing function can represent an inversely proportional relationship between the vehicle speed v and the vehicle speed sensing coefficient k. Therefore, when the vehicle speed v increases, the vehicle speed sensing coefficient k decreases, and thus the current assist torque output by the motor also decreases.

[0092] It's understandable that the current assist torque output by the motor is proportional to the vehicle's drag torque. The greater the vehicle's drag torque, the greater the current assist torque output by the motor, which improves the vehicle's drivability. Therefore, when the vehicle speed v is high, the vehicle's drag torque is low, so the motor can be controlled to output a smaller assist torque.

[0093] In an embodiment of the present application, the product of the vehicle speed sensing function and the maximum assist torque is determined as the first assist curve of the vehicle. When the current input torque of the steering wheel is large and the vehicle speed is constant, the first assist curve can be used to control the motor to output a fixed assist torque, so that the motor will not be overloaded.

[0094] In some embodiments, the above method for determining the vehicle power assist curve may also be implemented by the following steps:

[0095] S401: Determine a maximum input torque of a steering wheel of the vehicle according to a tangential force of the steering wheel of the vehicle and a radius of the steering wheel of the vehicle.

[0096] Here, the maximum input torque of the vehicle's steering wheel is the input torque applied to the steering wheel by the vehicle's driver, and therefore the maximum input torque is limited by the driver's physical strength. In the embodiment of the present application, the maximum input torque can be obtained based on the tangential force applied to the steering wheel by the driver and the radius of the steering wheel.

[0097] S402: Determining a maximum assist torque of a motor of the vehicle based on a maximum steering resistance torque of the vehicle and the maximum input torque;

[0098] In the embodiment of the present application, S402 can be implemented by the following steps:

[0099] S4021: Determine the vehicle's stationary steering resistance torque based on the friction coefficient between the vehicle's tires and the ground, the front axle load of the vehicle's tires, and the tire pressure of the vehicle.

[0100] Here, the maximum steering resistance torque of the vehicle may be the resistance torque when the vehicle is turning in place.

[0101] In the embodiment of the present application, the in-situ steering resistance torque M f This can be achieved through formula (4):

[0102]

[0103] Among them, M f is the rotation resistance torque, f is the friction coefficient between the tire and the ground, F z is the front axle load of the tire, and p is the tire pressure.

[0104] For example, when f is 0.7, Fz When the load is 8800N and p is 250kPa, M f It is 373.7N·m.

[0105] S4022: Determine a maximum steering resistance torque based on the stationary steering resistance torque, the steering ratio of the steering system, and the positive efficiency of the rack and pinion steering gear.

[0106] In the embodiment of the present application, the maximum steering resistance torque of the vehicle can be achieved by formula (5):

[0107]

[0108] Among them, M T is the maximum steering resistance torque converted to the steering column; i is the transmission ratio of the steering system; ξ + is the positive efficiency of the rack and pinion steering gear, M f is the resistance torque for turning in place.

[0109] S4023: Determine the difference between the maximum steering resistance torque and the maximum input torque as the maximum assist torque of the motor of the vehicle.

[0110] In the embodiment of the present application, the maximum assist torque of the vehicle's motor can be achieved by formula (6):

[0111] T amax =M T -T dmax Formula (6);

[0112] Among them, T amax is the maximum assist torque that the motor can provide, T dmax is the maximum input torque to the vehicle's steering wheel.

[0113] Based on the above embodiment, in T dmax is 7N·m, and M T When the load is 31N·m, T amax It is 24.1N·m.

[0114] In the embodiment of the present application, the vehicle's stationary steering torque is first determined based on the friction coefficient between the vehicle's tires and the ground, the front axle load of the vehicle's tires, and the tire pressure of the vehicle. The maximum steering torque is then determined based on the stationary steering torque, the steering system's rotation ratio, and the positive efficiency of the rack-and-pinion steering gear. Finally, the difference between the maximum steering torque and the maximum input torque is determined as the maximum power-assist torque of the vehicle's motor. This improves the accuracy of determining the maximum power-assist torque of the vehicle's motor.

[0115] S403: Determine a vehicle speed sensing function of the vehicle according to a plurality of test vehicle speeds of the vehicle.

[0116] In the embodiment of the present application, the above S403 can be implemented through S4031 and S4032:

[0117] S4031: For each test speed of the vehicle, adjust the speed sensing coefficient of the vehicle at the test speed until the input torque of the steering wheel of the vehicle is a preset expected steering torque, and determine the current speed sensing coefficient as the speed sensing coefficient corresponding to the test speed.

[0118] Here, the vehicle speed sensing coefficient can be adjusted to make the input torque of the steering wheel equal to the desired control torque, and the current of the power assist motor I in the current state can be detected at the same time. a , thus obtaining the vehicle speed sensitivity coefficient at the current vehicle speed. Repeat this step at different vehicle speeds to obtain the vehicle speed sensitivity coefficient at different vehicle speeds.

[0119] S4032: Determine a vehicle speed sensing function of the vehicle based on the vehicle speed sensing coefficients corresponding to the plurality of test vehicle speeds of the vehicle.

[0120] In the embodiment of the present application, after obtaining the vehicle speed sensitivity coefficients corresponding to multiple test speeds of the vehicle, the vehicle speed sensitivity function can be obtained based on a preset fitting algorithm. For example, the fitting algorithm can be a Gauss-Newton method in Matlab.

[0121] In the embodiment of the present application, the vehicle speed sensing function can be implemented by formula (7):

[0122] k(v)=a×e bv Formula (7);

[0123] Where a and b are both constants.

[0124] In this embodiment of the present application, the vehicle speed sensitivity coefficient is adjusted for each test speed until the vehicle's steering wheel input torque reaches a preset desired steering torque, and the current vehicle speed sensitivity coefficient is determined as the speed sensitivity coefficient corresponding to the test speed. Finally, the vehicle speed sensitivity function is determined based on the speed sensitivity coefficients corresponding to the multiple test speeds. In this way, the relationship between the vehicle's real-time speed and the speed sensitivity coefficient can be accurately determined.

[0125] S404: Determine the power steering dead zone torque of the vehicle according to the electric power steering condition.

[0126] Here, the electric power steering condition represents the sensitivity of the control system of the vehicle, and the more sensitive the control system of the vehicle is, the smaller the power assist dead zone torque is.

[0127] It is understandable that the vehicle power-assistance curve includes a third power-assistance curve, which characterizes the relationship between the current input torque and the current power-assistance torque of the motor when the current input torque of the vehicle is less than or equal to the power-assistance dead zone torque. Among them, when the current input torque of the vehicle is less than or equal to the power-assistance dead zone torque, the current power-assistance torque of the motor can be 0. In other words, when the current input torque of the vehicle is less than or equal to the power-assistance dead zone torque, the motor will not output the current power-assistance torque, and will only enter the power-assistance zone (i.e., the second power-assistance curve) when it is greater than the power-assistance dead zone torque. Therefore, the power-assistance dead zone torque determines whether the vehicle enters the power-assistance zone. Therefore, the smaller the power-assistance dead zone torque, the easier it is for the vehicle to enter the power-assistance zone, and the higher the sensitivity of the vehicle's control system; the larger the power-assistance dead zone torque, the less likely the vehicle is to enter the power-assistance zone, and the lower the sensitivity of the vehicle's control system.

[0128] In this embodiment, the maximum input torque of the vehicle's steering wheel is determined based on the tangential force of the vehicle's steering wheel and the radius of the vehicle's steering wheel. The maximum assist torque of the vehicle's motor is determined based on the vehicle's maximum steering resistance torque and maximum input torque. The vehicle's speed sensing function is determined based on multiple test vehicle speeds. The vehicle's assist dead zone torque is determined based on the electric power steering conditions. In this way, the parameters used to calibrate the vehicle's assist curve can be accurately determined.

[0129] In some embodiments, the above method for determining the vehicle power assist curve may also be implemented by the following steps:

[0130] S501: Determine the steering wheel assist torque based on the vehicle assist curve, the current speed of the vehicle, and the current input torque of the steering wheel.

[0131] In the embodiment of the present application, after determining the vehicle power assist curve through the above embodiment, the current vehicle speed, as detected by the speed sensor, and the current input torque applied to the steering wheel by the driver, as detected by the torque sensor, can be obtained. The steering wheel power assist torque is then determined from the vehicle power assist curve based on the current input torque.

[0132] It is understandable that different current input torques use different power assist curves. Therefore, it is necessary to compare the current input torque with the power assist dead zone torque and the maximum input torque. If the current input torque is less than or equal to the power assist dead zone torque, the third power assist curve is used, i.e., the steering wheel power assist torque is 0. If the current input torque is greater than the power assist dead zone torque and less than or equal to the maximum input torque, the second power assist curve is used, i.e., the current input torque and the current vehicle speed are substituted into the function corresponding to the second power assist curve to obtain the steering wheel power assist torque. If the current input torque is greater than the maximum input torque, the first power assist curve is used, i.e., the current vehicle speed is substituted into the function corresponding to the first power assist curve to obtain the steering wheel power assist torque.

[0133] S502: Determine the product of the electromagnetic torque coefficient of the power assist motor and the transmission ratio of the reduction mechanism as the power assist linear coefficient.

[0134] S503: Taking the quotient of the assist torque and the assist linear coefficient, the result is determined as the assist current; wherein the assist torque and the assist current are in a linear relationship.

[0135] In the embodiment of the present application, the above-mentioned assist current can be realized by formula (8):

[0136]

[0137] Among them, I a is the assist current, T a is the steering wheel assist torque, G is the transmission ratio of the reduction mechanism, k a is the electromagnetic torque coefficient of the power assist motor.

[0138] Exemplarily, the transmission ratio of the reduction mechanism may be 21, and the electromagnetic torque coefficient of the power-assisting motor may be 0.05.

[0139] S504: Determine the response torque of the motor based on the assist current.

[0140] It is understood that the assist current is the desired output current of the motor, but the actual output current of the motor may not be equal to the assist current. Therefore, it is necessary to obtain the actual current output by the motor, then use a current controller to adjust the actual current based on the assist current. The adjusted current is input into the PWM controller. The PWM controller outputs an assist voltage to the motor based on the adjusted current, and the motor outputs the motor's response torque to the steering mechanism based on the assist voltage. Exemplarily, the current controller can adjust the actual current based on the assist current using at least one of the following adjustment methods: PID control, fuzzy PID control, and extended Kalman filter algorithm.

[0141] In the embodiment of the present application, the steering wheel assist torque is determined based on the vehicle's current speed and the current steering wheel input torque using the vehicle assist curve. The assist linear coefficient is determined by multiplying the electromagnetic torque coefficient of the assist motor and the transmission ratio of the reduction mechanism. The assist current is determined as the quotient of the assist torque and the assist linear coefficient. The motor response torque is determined based on the assist current. Thus, after the assist torque corresponding to the vehicle speed and current input torque is determined using the vehicle assist, the assist current corresponding to the assist torque can be determined first, and finally, the motor response torque corresponding to the assist current can be determined. This allows the motor to output a response torque that matches the vehicle speed and current input torque.

[0142] In the embodiments of the present application, Figure 3 This is a system architecture block diagram of an electric power steering system provided in an embodiment of the present application, such as Figure 3 As shown, the electric power steering system 30 architecture includes: a steering wheel 301, a torque sensor 302, an angle sensor 303, a vehicle speed sensor 304, a power assist motor 305, a worm gear reduction mechanism 306, an ECU 307, and a rack and pinion steering gear 308. The torque sensor and angle sensor are mounted on the steering column to measure the torque and deformation applied by the steering wheel to the upper end of the steering column and transmit the calculated torque and angle to the ECU. A vehicle speed sensor, also referred to as a wheel speed sensor, is mounted on each wheel and transmits the calculated current vehicle speed to the ECU. A vehicle speed sensor 304, also referred to as a wheel speed sensor, is mounted on each wheel and transmits the calculated current vehicle speed to the ECU 307. In the commonly used column-type electric power steering (C-EPS) system, the power assist motor 305 is mounted on the steering column and, through the worm gear reduction mechanism 306, outputs the reduced torque to the steering column to assist the driver in steering. Furthermore, the assist motor 305 transmits the current flowing through the assist motor to the ECU 307 .

[0143] The rack-and-pinion steering system converts torque from the power-assisted motor into rack axial force, which is then applied to the steering wheel via a lateral tie rod to control steering. ECU 307 receives torque and angle from steering wheel 301, as well as the current vehicle speed at the wheel, and determines the current steering state, which can be either basic speed-dependent power assist, damping control, or self-centering control.

[0144] In some embodiments, Figure 4 A flow chart of a basic speed-dependent power assist control strategy provided in an embodiment of the present application is shown as follows: Figure 4 As shown, Figure 4 As shown, the control strategy process may include the following steps:

[0145] S601: Obtain the vehicle speed and the input torque of the vehicle.

[0146] In an embodiment of the present application, when controlling vehicle steering using a basic speed-dependent power assist control strategy, the vehicle speed and input torque can be first obtained through different sensors respectively. Specifically, the speed of the vehicle equipment can be obtained through a speed sensor, and the input torque of the vehicle equipment can be obtained through a torque sensor.

[0147] S602: Determine the assist current through the ECU based on the driving data and the vehicle assist curve.

[0148] In an embodiment of the present application, after obtaining the vehicle speed of the vehicle equipment through a speed sensor and obtaining the input torque of the vehicle equipment through a torque sensor, the vehicle power assist curve determination device can determine the power assist current through the ECU based on the driving data and the vehicle power assist curve.

[0149] S603: Outputting a target voltage signal to the power-assisting motor via the current controller and the PWM controller, so that the power-assisting motor generates a corresponding power-assisting torque to control the vehicle steering.

[0150] In an embodiment of the present application, after the ECU determines the assist current based on driving data and the vehicle assist curve, the vehicle assist curve determination device can output the target voltage signal U to the assist motor through the current controller and the PWM controller, and the assist motor generates a corresponding assist torque to control the vehicle steering.

[0151] It should be noted that in the embodiment of the present application, the device for determining the vehicle power assist curve can perform closed-loop control on the power assist current returned by the power assist motor and the preset power assist current according to the control strategy, so that the current current is equal to the preset power assist current.

[0152] Specifically, in an embodiment of the present application, the ECU collects the current vehicle speed information based on the vehicle speed sensor and the input torque of the steering wheel based on the torque sensor, determines the magnitude of the assist current through the vehicle assist curve, and the ECU transmits the assist current to the assist motor through the PWM controller, and the assist motor outputs the corresponding assist torque.

[0153] like Figure 5 As shown, the sensor 501 collects the vehicle speed V and input torque T s The current controller 503 then inputs the power-assistance current to the PWM controller 504. The PWM controller 504 determines the power-assistance voltage based on the power-assistance current and applies the power-assistance voltage to the power-assistance motor, causing the power-assistance motor to output a power-assistance torque to the steering mechanism 505. At this point, the forces acting on the steering mechanism 505 include the power-assistance torque, the steering wheel torque, and the steering resistance torque.

[0154] In an embodiment of the present application, a vehicle power assist curve for use in the field of electric power steering is designed. The vehicle power assist curve is designed based on a curve type, while ensuring that the mathematical expression of the power assist curve is concise and easy to calibrate.

[0155] The expression of the vehicle power assist curve designed in this application is shown in formula (9):

[0156]

[0157] Where:

[0158] T m : The final torque output by the motor;

[0159] k(v): vehicle speed sensitivity coefficient;

[0160] T amax : Maximum assist torque of the motor;

[0161] T d0 : Assist dead zone;

[0162] T dmax : Maximum steering wheel input torque corresponding to maximum power-assist torque;

[0163] T d : Current steering wheel input torque.

[0164] Furthermore, in the embodiments of the present application, Figure 6 A vehicle power assist curve diagram provided in an embodiment of the present application is as follows: Figure 6 As shown, the horizontal axis is the steering wheel input torque (N·m) (input torque), and the vertical axis is the power assist motor output torque (N·m) (power assist torque). This is implemented at different vehicle speeds to obtain the output torque under different input torques.

[0165] This vehicle power-assistance curve is based on the existing vehicle power-assistance curve. It solves the problem that the curve has inflection points that reduce the driver's feel and the traditional curve does not present a concave front and convex rear form. It uses a relatively simple mathematical form to express it, and is independently calibrated according to the different requirements for feel in the small power-assistance area and the large power-assistance area. There is no multi-segment form, which greatly reduces the workload during parameter calibration.

[0166] The vehicle power-assistance curve draws different power-assistance curves according to different vehicle speeds. Due to the symmetry between the steering wheel input torque and the power-assistance motor output torque, the vehicle power-assistance curve is oddly symmetrical about the coordinate origin in the first and third quadrants of the plane rectangular coordinate system. Therefore, the mathematical expression of the vehicle power-assistance curve in the first quadrant is shown in formula (10):

[0167]

[0168] The first quadrant of the vehicle's power assist curve can be divided into three segments: the dead zone, the power assist curve, and the saturation zone. The power assist torque in the dead zone is zero, while the power assist torque in the power assist curve increases steadily with increasing steering wheel input torque. The power assist torque in the saturation zone is the maximum value at the current vehicle speed. To ensure that the power assist increases at a faster rate when the torque is low and decreases at a slower rate when the torque is high, the curve is concave at the front and convex at the back in the power assist curve.

[0169] In addition, when the assist torque is constant, the assist torque of the non-characteristic speed of the existing vehicle assist curve is obtained by linear interpolation of the assist torques of two adjacent characteristic speeds. Therefore, the curve is not smooth enough in the entire speed range.

[0170] Furthermore, in the embodiment of the present application, in order to maintain a smooth transition of the curve at all vehicle speeds and within the entire hand torque range, Figure 7 A three-dimensional boost torque search diagram is provided in the embodiment of the present application, such as Figure 7 As shown, both hand torque and vehicle speed are equally divided into 100 parts to ensure smooth transitions across the entire range, further improving the driver's control feel. Existing single-chip microcontrollers have sufficient memory and high computing power, eliminating the problem of requiring a large amount of calibration data.

[0171] The vehicle power assist curves of the present application are smoothly connected, have good linearity, and present a concave front and convex rear shape, which improves the steering feel while ensuring the ease of steering, and the steering feel is smooth; compared with the current vehicle power assist curves used in practice, the power assist curve of the present application has a simpler mathematical form, fewer calibration parameters and is easier to obtain, which facilitates technicians to adjust the power assist curve by modifying relevant parameters, shortens the development cycle, and reduces the workload of developers; compared with the current linear interpolation method for calculating the power assist torque based on non-characteristic vehicle speeds, the present application provides a three-dimensional lookup table with smooth transitions across all vehicle speeds and the entire hand torque range, which can theoretically improve the driver's control feel.

[0172] At present, there are three common vehicle power curves: linear ( Figure 8 Vehicle power assist curve shown), broken line type ( Figure 9 The vehicle power assist curve shown) and curve type ( Figure 10 Vehicle power assist curve shown).

[0173] like Figure 8 As shown in the figure, the linear power assist curve has a constant speed sensitivity coefficient k(v) at a certain characteristic speed. The design of this power assist curve is easy to implement and easy to adjust. When the speed is a fixed value and in a certain range, the output power assist torque T of the power assist motor is aIt increases in proportion to the driver's hand torque, but when passing over uneven roads, the impact generated by the road surface will have a greater impact on the driver, and the driver has a poor grasp of the road feel.

[0174] like Figure 9 As shown, the broken-line power-assistance curve improves upon the linear type. At a specific speed, the speed sensitivity coefficient k(v) takes on different values ​​(k1, k2, k3…), providing varying degrees of power-assistance torque under varying hand torque conditions. The power-assistance current and hand torque form a segmented linear relationship, making the power-assistance curve design relatively easy to implement and adjust parameters. However, a sudden change in slope occurs at the intersection of different speed sensitivity coefficients, causing a sense of unsmooth control for the driver.

[0175] like Figure 11 As shown in the figure, under a certain characteristic vehicle speed, the speed sensitivity coefficient k(v) of the curved power assist curve will change continuously and evenly. When the vehicle speed is a fixed value and in a certain range, the power assist gain will change evenly with the change of hand torque, taking into account both steering ease and road feel.

[0176] In an embodiment of the present application, a power-assisting motor is mounted on the steering column and, through a worm gear mechanism, outputs the reduced torque to the steering column to assist the driver in steering. Furthermore, the power-assisting motor transmits current flowing through it to the ECU. A rack-and-pinion steering gear converts the torque increased by the power-assisting motor into rack axial force, which is then applied to the steering wheel via a lateral tie rod, thereby determining the vehicle power-assistance curve. The ECU receives torque and steering angle from the steering wheel, as well as the current vehicle speed at the wheel end, and determines the current steering state, including basic speed-dependent power assistance, damping control, or self-centering control. If the system is in speed-dependent power assistance, the ECU searches the vehicle power-assistance curve based on the torque and speed to obtain the corresponding power-assistance current. This current is converted into an electrical signal, which is then passed through a PWM controller to output the corresponding power-assistance voltage. The ECU then performs closed-loop control based on the motor current signal and the desired current signal, using an internal control strategy (commonly used calculus-based PID control, fuzzy-PID control, and extended Kalman filter algorithms) to ensure that the current current is equal to the desired current.

[0177] When the steering wheel angle and angular velocity determine that the system is in speed-dependent power assist, the ECU obtains the current power assist value based on an internal two-dimensional or three-dimensional lookup table. This power assist value is closely related to the vehicle power assist curve. The vehicle power assist curve designed in this application can be calibrated according to different feel requirements. The calibration parameters are relatively simple and easy to obtain. The entire curve is relatively smooth, ensuring that the driver will not experience a sense of frustration when turning, and the power assist area meets the feel requirements of concave front and convex rear. The curve has the functions of steering smoothness and concise mathematical expression.

[0178] The curves in the first and third quadrants are oddly symmetric about the origin. When the sign of the hand torque is negative, because the entire image is oddly symmetric about the origin, the absolute value of the independent variable in the above formula needs to be taken and then inserted into the above formula, and the obtained assist torque can be taken as the negation.

[0179] The mathematical expression of the vehicle power assist curve in this application is relatively concise, and the calibration curve used is relatively easy to obtain. The calibration parameters involved are T d0 , T dmax , T amax , k(v), calibration parameters play a decisive role in the driver's feel. The following combines theoretical derivation and actual vehicle data to obtain the values ​​of the above four key calibration parameters. This process is used as a reference.

[0180] 1. Dead zone threshold T d0 (Power dead zone torque):

[0181] T d0 The setting should be moderate, T d0 If the value is too large, the driver will need to apply a larger torque before the assist torque is output, which will increase the driver's driving intensity and is not in line with the original design intention of EPS. d0 If it is too small, even the slightest impact on the road will cause the steering wheel to turn with power, which will cause the driver to lose the sense of the road and the sense of the vehicle's center position. This is very dangerous at high speeds. At the same time, an overly sensitive control system will increase the operating burden of the motor and shorten the motor's service life. Generally, T is set d0 1N·m.

[0182] 2. Maximum steering wheel input torque T corresponding to maximum power torque dmax :

[0183] At a certain vehicle speed, the output torque of the power assist motor increases with the increase of the steering wheel input torque. The steering wheel input torque is applied by the driver and is limited by the driver's physical strength. According to the national standard QC / T480-1999 for the automotive industry, the tangential force applied by the driver on the steering wheel is generally 15-50N·m, and the radius of the steering wheel is usually 0.2m. The calculated input torque of the steering wheel is 3-10N·m. Taking into account driving habits, T is set. dmax 7N·m.

[0184] 3. Maximum motor assist torque T amax :

[0185] The resistance torque is the largest when the car is turning in place, so the power torque provided by the power motor is the largest. At this time, the current vehicle speed can be considered to be zero. Generally, a semi-empirical formula is often used to calculate the resistance torque of turning in place, as shown in formula (11):

[0186]

[0187] Where:

[0188] M f : In-situ steering resistance torque (N·m);

[0189] f: friction coefficient between tire and ground, take 0.7;

[0190] F z : Front axle load of the tire (N), take 8800N;

[0191] p: tire pressure (kpa), take 250kpa.

[0192] After obtaining the in-situ resistance torque, the calculation result needs to be converted to the steering column. The calculation formula is shown in formula (12):

[0193]

[0194] Where:

[0195] M T : Maximum steering resistance torque converted to the steering column (N·m);

[0196] i: The transmission ratio of the steering system is 15;

[0197] ξ + : The positive efficiency of the rack and pinion steering gear is 80%.

[0198] Combining formula (8) and T dmax , the maximum assist torque that the motor can provide is shown in formula (13):

[0199] T amax =M T -T dmax =31.1N·m-7N·m=24.1N·m (13)

[0200] Currently, permanent magnet brushed DC motors are commonly used as power assist motors. There is a simple mathematical relationship between their electrical input parameters and mechanical output characteristics, which can simplify the motor's internal structure and perform linear processing. Therefore, it can be assumed that the motor's maximum power assist torque T amax and the maximum assist current I amax There is a linear relationship between them, as shown in formula (14):

[0201]

[0202] Where:

[0203] G: transmission ratio of reduction mechanism, take 21;

[0204] k a : The electromagnetic torque coefficient of the power assist motor is taken as 0.05.

[0205] The vehicle power-assistance curve of the embodiment of the present application calculates the motor power-assistance torque. In order to simplify the model, it is assumed that the power-assistance torque T under any conditions is a and assist current I a There is a linear relationship between them, and the transfer relationship between them is shown in formula (14).

[0206] 4. Vehicle speed sensitivity coefficient k(v):

[0207] For the calibration of vehicle speed induction coefficient k(v), actual vehicle data is usually used. At a certain vehicle speed, the value of k(v) is adjusted so that the input torque of the steering wheel is equal to the desired operating torque, and the current of the power assist motor I is detected at the same time. a , and thus get k(v) at the current speed. Repeat this step at different speeds to get k(v) at different speeds.

[0208] This application refers to actual vehicle test data and divides the 0-80 km / h range into 19 intervals. K(v) calibration tests are performed in each of these intervals, and the calculated K(v) values ​​are recorded. The average vehicle speed within each interval is also calculated and recorded. The results are shown in Tables 1 and 2.

[0209] Table 1

[0210]

[0211] Table 2

[0212]

[0213] The data in Tables 1 and 2 were fitted in Matlab using the Gauss-Newton method, with vehicle speed as the x-axis and k(v) as the y-axis. The fitted curve expression is shown in formula (15):

[0214] k(v)=a×e bv (15)

[0215] Furthermore, in the embodiments of the present application, Figure 10 A fitting result diagram provided in the embodiment of the present application is shown as follows: Figure 10 As shown in Figure 1, k(v) is different at different speeds, and as the speed increases, k(v) decreases. The fitted curve expression is shown in formula (16):

[0216] k(v)=1.0817×e -0.023808v (16)

[0217] The undetermined parameter T obtained through the above calibration process d0 、T dmax 、T amax and k(v), and bring them into equation (10) to get the image of the vehicle power assist curve in the first quadrant. Then rotate the curve 180 degrees about the coordinate origin to get the complete power assist curve.

[0218] In the embodiment of the present application, the three-dimensional boost torque lookup table (ie Figure 7 ) where the x-axis and y-axis represent the hand torque and vehicle speed, respectively, and the z-axis represents the motor assist torque. After obtaining the assist torque from the table, the assist current is calculated according to Equation (14). This current is converted into an electrical signal and then output to the assist motor via the PWM controller, which controls the motor to output the desired assist torque.

[0219] The driver expects different levels of power assistance at different vehicle speeds and different steering wheel input torques. At low vehicle speeds, the power assist motor is expected to provide a larger power assist torque to ensure the ease of steering at low speeds; and at higher vehicle speeds, the power assist motor is expected to provide a smaller power assist torque to ensure the safety of steering at high speeds. When the power assist motor provides power assistance, the driver hopes that the gradient of the power assist torque provided is continuous to maintain a better steering feel. When the steering wheel input torque is within a smaller range, the change of the motor power assist torque with the hand torque should be faster. When the steering wheel input torque is larger, the change of the motor power assist torque with the hand torque should become slower, that is, the power assist curve presents a characteristic of being concave at the front and convex at the back. In addition, the driver expects a smooth transition throughout the entire vehicle speed range to further improve the power assist feel. The present application meets the above requirements.

[0220] In summary, the present application designs a speed-dependent vehicle power assist curve for use in the field of electric power steering. The calibration parameters of the curve are relatively few and relatively easy to obtain. In addition, an example is provided to calculate the various parameters in the mathematical expression of the curve, which effectively improves the development and debugging process of the EPS system in the basic power assist stage. Compared with the traditional power assist curve, the steering assist feel is optimized because the designed curve has a smooth transition at all vehicle speeds and within the entire hand torque range. The present application is applied to the field of electric power steering, which can save manpower and financial resources and achieve high productivity.

[0221] Based on the same inventive concept as the above embodiments, the present embodiment provides a device for determining a vehicle power assist curve. Figure 12 A schematic diagram of the structure of a vehicle power assist curve determination device provided in an embodiment of the present application is shown in FIG. Figure 12 As shown, the vehicle power assist curve determination device 12 includes an acquisition unit 121 and a determination unit 122 .

[0222] An acquisition unit 121 is configured to acquire a maximum input torque of a vehicle's steering wheel, a maximum power-assistance torque of a vehicle's motor, a vehicle speed sensing function, and a power-assistance dead-zone torque of the vehicle; wherein the vehicle speed sensing function is configured to represent a relationship between the vehicle speed and the vehicle speed sensing coefficient;

[0223] The determination unit 122 is used to determine a first power-assistance curve of the vehicle based on a vehicle speed sensing function and a maximum power-assistance torque; wherein the first power-assistance curve is used to characterize the relationship between the current input torque of the steering wheel and the current power-assistance torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque; and to determine a second power-assistance curve of the vehicle based on the maximum input torque, the maximum power-assistance torque of the vehicle's motor, the vehicle speed sensing function and the power-assistance dead-zone torque of the vehicle; wherein the second power-assistance curve is used to characterize the relationship between the current input torque and the current power-assistance torque of the motor when the current input torque of the steering wheel is greater than the power-assistance dead-zone torque and is less than or equal to the maximum input torque; and the first power-assistance curve and the second power-assistance curve are determined as the vehicle power-assistance curve.

[0224] In some embodiments, the determination unit 122 is further configured to determine a sinusoidal assist function based on the current input torque, the assist dead zone torque, and the maximum input torque; and to determine the product of the sinusoidal assist function, the vehicle speed sensing function, and the maximum assist torque as the second assist curve of the vehicle.

[0225] In some implementations, the determination unit 122 is further configured to determine the product of the vehicle speed sensing function and the maximum power assist torque as the first power assist curve of the vehicle.

[0226] In some embodiments, the determination unit 122 is further used to determine the maximum input torque of the vehicle's steering wheel based on the tangential force of the vehicle's steering wheel and the radius of the vehicle's steering wheel; determine the maximum power assist torque of the vehicle's motor based on the vehicle's maximum steering resistance torque and maximum input torque; determine the vehicle's speed sensing function based on multiple test speeds of the vehicle; and determine the vehicle's power assist dead zone torque based on the electric power steering condition.

[0227] In some embodiments, the determination unit 122 is further used to adjust the speed sensing coefficient of the vehicle at each test speed of the vehicle until the input torque of the steering wheel of the vehicle is a preset expected steering torque, and determine the current speed sensing coefficient as the speed sensing coefficient corresponding to the test speed; and determine the speed sensing function of the vehicle based on the speed sensing coefficients corresponding to multiple test speeds of the vehicle.

[0228] In some embodiments, the determination unit 122 is further used to determine the vehicle's stationary steering resistance torque based on the friction coefficient between the vehicle's tires and the ground, the front axle load of the vehicle's tires, and the air pressure of the vehicle's tires; determine the maximum steering resistance torque based on the stationary steering resistance torque, the steering system's rotation ratio, and the positive efficiency of the rack and pinion steering gear; and determine the difference between the maximum steering resistance torque and the maximum input torque as the maximum assist torque of the vehicle's motor.

[0229] In some embodiments, the determination unit 122 is further used to determine the steering wheel assist torque based on the current speed of the vehicle and the current input torque of the steering wheel through the vehicle assist curve; determine the product of the electromagnetic torque coefficient of the assist motor and the transmission ratio of the reduction mechanism as the assist linear coefficient; divide the assist torque by the assist linear coefficient to determine the assist current; wherein the assist torque is linearly related to the assist current; and determine the response torque of the motor based on the assist current.

[0230] Based on the same inventive concept as the above embodiments, the present embodiment provides a device for determining a vehicle power assist curve. Figure 13 A schematic diagram of the structure of a vehicle power assist curve determination device provided in an embodiment of the present application is shown in FIG. Figure 13 As shown, the vehicle power assist curve determination device 13 may include a processor 131 , a memory 132 , a communication interface 133 , and a bus 134 for connecting the processor 131 , the memory 132 , and the communication interface 133 .

[0231] Furthermore, in an embodiment of the present application, the memory 132 is used to store a computer program that can be run on the processor;

[0232] The processor 131 is used to obtain the maximum input torque of the vehicle's steering wheel, the maximum assist torque of the vehicle's motor, the vehicle's speed sensing function and the vehicle's assist dead zone torque when running the computer program; wherein the vehicle speed sensing function is used to characterize the relationship between the vehicle's speed and the vehicle's speed sensing coefficient; based on the vehicle speed sensing function and the maximum assist torque, determine the vehicle's first assist curve; wherein the first assist curve is used to characterize the relationship between the current input torque and the current assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque; based on the maximum input torque, the maximum assist torque of the vehicle's motor, the vehicle's speed sensing function and the vehicle's assist dead zone torque, determine the vehicle's second assist curve; wherein the second assist curve is used to characterize the relationship between the current input torque and the current assist torque of the motor when the current input torque of the steering wheel is greater than the assist dead zone torque and less than or equal to the maximum input torque; the first assist curve and the second assist curve are determined as the vehicle assist curve.

[0233] The present application also provides a computer program product, including a computer program or instructions, which, when executed by a processor, implements some or all of the steps in the above method. The computer program product can be implemented specifically by hardware, software, or a combination thereof. The computer program product can be implemented specifically by hardware, software, or a combination thereof. In an optional embodiment, the computer program product is embodied as a computer storage medium. In another optional embodiment, the computer program product is embodied as a software product, such as a software development kit (SDK), etc.

[0234] In addition, the functional modules in this embodiment may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware or software functional modules.

[0235] If the integrated unit is implemented as a software functional module and not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a vehicle device or processor to execute all or part of the steps of the method of this embodiment. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0236] An embodiment of the present application provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the method for determining the vehicle power assist curve as described above.

[0237] Specifically, the program instructions corresponding to the method for determining a vehicle power assist curve in this embodiment can be stored on a storage medium such as a CD, a hard disk, or a USB flash drive. When the program instructions corresponding to the method for determining a vehicle power assist curve in the storage medium are read or executed by an electronic device, the following steps are included:

[0238] Obtaining the maximum input torque of the vehicle's steering wheel, the maximum power-assistance torque of the vehicle's motor, the vehicle's speed sensing function, and the vehicle's power-assistance dead-zone torque; wherein the speed sensing function is used to characterize the relationship between the vehicle's speed and the vehicle's speed sensing coefficient;

[0239] Determining a first power assist curve for the vehicle based on the vehicle speed sensing function and the maximum power assist torque; wherein the first power assist curve is used to represent the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque;

[0240] determining a second power assist curve for the vehicle based on the maximum input torque, the maximum power assist torque of the vehicle's motor, a vehicle speed sensing function, and the power assist dead-band torque of the vehicle; wherein the second power assist curve is used to represent the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead-band torque and less than or equal to the maximum input torque;

[0241] The first power assist curve and the second power assist curve are determined as the vehicle power assist curve.

[0242] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of hardware embodiments, software embodiments, or embodiments combining software and hardware. Furthermore, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage and optical storage, etc.) containing computer-usable program code.

[0243] The present application is described with reference to the implementation flow charts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flow charts and / or block diagrams, as well as the combination of processes and / or boxes in the flow charts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the implementation flow charts. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that performs the functions specified in one or more boxes.

[0244] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the instructions in the implementation flow diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0245] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process described in the flowchart. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0246] The above description is merely a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application.

Claims

1. A method for determining a vehicle power assist curve, characterized in that: The determination method includes: Obtaining a maximum input torque of a vehicle's steering wheel, a maximum power-assistance torque of a motor of the vehicle, a vehicle speed sensing function of the vehicle, and a power-assistance dead-band torque of the vehicle; wherein the vehicle speed sensing function is used to characterize the relationship between the vehicle speed and the vehicle speed sensing coefficient; determining a first power assist curve for the vehicle based on the vehicle speed sensing function and the maximum power assist torque; wherein the first power assist curve is used to represent a relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque; determining a second power assist curve for the vehicle based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, a vehicle speed sensing function, and a power assist dead-band torque of the vehicle; wherein the second power assist curve is used to represent a relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead-band torque and less than or equal to the maximum input torque; The first power assist curve and the second power assist curve are determined as a vehicle power assist curve.

2. The method for determining a vehicle power assist curve according to claim 1, wherein: The determining of a second power assist curve of the vehicle based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, a vehicle speed sensing function of the vehicle, and the power assist dead-band torque of the vehicle includes: determining a sinusoidal assist function based on the current input torque, the assist dead-band torque, and the maximum input torque; The product of the sinusoidal power assist function, the vehicle speed sensing function and the maximum power assist torque is determined as a second power assist curve of the vehicle.

3. The method for determining a vehicle power assist curve according to claim 1, wherein: The determining of a first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque includes: The product of the vehicle speed sensing function and the maximum power-assistance torque is determined as a first power-assistance curve of the vehicle.

4. The method for determining a vehicle power assist curve according to claim 1, wherein: The method further comprises: determining a maximum input torque of the steering wheel of the vehicle according to a tangential force of the steering wheel of the vehicle and a radius of the steering wheel of the vehicle; determining a maximum assist torque of a motor of the vehicle based on a maximum steering resistance torque of the vehicle and the maximum input torque; determining a vehicle speed sensing function of the vehicle based on a plurality of test vehicle speeds of the vehicle; The power-assist dead-band torque of the vehicle is determined according to an electric power steering condition.

5. The method for determining a vehicle power assist curve according to claim 4, wherein: The determining of the vehicle speed sensing function according to the plurality of test vehicle speeds of the vehicle includes: For each test speed of the vehicle, adjusting a vehicle speed sensitivity coefficient of the vehicle at the test speed until an input torque of a steering wheel of the vehicle reaches a preset desired steering torque, and determining the current vehicle speed sensitivity coefficient as the vehicle speed sensitivity coefficient corresponding to the test speed; A vehicle speed sensing function of the vehicle is determined based on vehicle speed sensing coefficients corresponding to the plurality of test vehicle speeds of the vehicle.

6. The method for determining a vehicle power assist curve according to claim 4, wherein: The determining, based on the maximum steering resistance torque of the vehicle and the maximum input torque, the maximum assist torque of the motor of the vehicle includes: Determining the vehicle's stationary steering resistance torque based on a friction coefficient between the vehicle's tires and the ground, a front axle load of the vehicle's tires, and an air pressure of the vehicle's tires; determining a maximum steering resistance torque according to the stationary steering resistance torque, a steering ratio of the steering system, and a positive efficiency of the rack and pinion steering gear; A difference between the maximum steering resistance torque and the maximum input torque is determined as a maximum assist torque of the motor of the vehicle.

7. The method for determining a vehicle power assist curve according to any one of claims 1 to 6, characterized in that: The method further comprises: determining the steering wheel assist torque based on the vehicle assist curve and the current speed of the vehicle and the current input torque of the steering wheel; The product of the electromagnetic torque coefficient of the power-assisting motor and the transmission ratio of the reduction mechanism is determined as the power-assisting linear coefficient; The quotient of the assist torque and the assist linear coefficient is determined as the assist current; wherein the assist torque and the assist current are in a linear relationship; Based on the assist current, the response torque of the motor is determined.

8. A device for determining a vehicle power assist curve, characterized in that: The vehicle power-assistance curve determining device includes: an acquisition unit, configured to acquire a maximum input torque of a steering wheel of a vehicle, a maximum power-assistance torque of a motor of the vehicle, a vehicle speed sensing function of the vehicle, and a power-assistance dead-zone torque of the vehicle; wherein the vehicle speed sensing function is used to characterize a relationship between the vehicle speed and a vehicle speed sensing coefficient; A determination unit is used to determine a first power assist curve of the vehicle based on the vehicle speed sensing function and the maximum power assist torque; wherein the first power assist curve is used to characterize the relationship between the current input torque of the steering wheel and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the maximum input torque; a second power assist curve of the vehicle is determined based on the maximum input torque, the maximum power assist torque of the motor of the vehicle, the vehicle speed sensing function of the vehicle and the power assist dead zone torque of the vehicle; wherein the second power assist curve is used to characterize the relationship between the current input torque and the current power assist torque of the motor when the current input torque of the steering wheel is greater than the power assist dead zone torque and is less than or equal to the maximum input torque; the first power assist curve and the second power assist curve are determined as vehicle power assist curves.

9. A device for determining a vehicle power assist curve, characterized in that: The device for determining the vehicle power assist curve includes: a processor and a storage medium storing executable instructions, wherein the storage medium relies on the processor to perform operations through a communication bus, and when the executable instructions are executed by the processor, the method for determining the vehicle power assist curve described in any one of claims 1 to 7 is executed.

10. A computer storage medium, characterized in that Executable instructions are stored, and when the executable instructions are executed by a processor, the processor executes the method for determining a vehicle power assist curve according to any one of claims 1 to 7.

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