A method for suppressing road force feedback in power steering system

Abstract

The invention relates to the technical field of automobile steering devices, and specifically discloses a method for suppressing road force feedback of a power steering system, comprising obtaining a torque signal of the power steering system and a rotation speed signal of a steering motor; determining whether the change directions of the torque signal and the rotation speed signal are consistent; in response to the inconsistency of the change directions of the torque signal and the rotation speed signal, converting the torque signal and the rotation speed signal into a frequency domain through Fourier transform; comparing the converted frequency domain signal with a frequency threshold, and dividing the frequency domain signal into a high-frequency part and a low-frequency part; determining a high-frequency weight and a low-frequency weight for the high-frequency part and the low-frequency part respectively; comprehensively determining a frequency weight according to the high-frequency weight and the low-frequency weight; determining a suppression coefficient for an output current of a steering motor according to the rotation speed and the frequency weight of the steering motor to suppress feedback of road force; and being able to adjust the suppression coefficient according to the complexity of the current road condition, reduce the influence of the road impact on the steering wheel, and improve the stability of control.

Description

Technical Field

[0001] The invention relates to the technical field of automobile steering gears, and in particular to a method for suppressing road force feedback of a power steering system. Background Art

[0002] All-terrain vehicles are often used in complex and diverse terrains. Compared with ordinary passenger cars and commercial vehicles, they usually travel on unpaved roads, such as potholes, bumps or low-adhesion roads. This places higher demands on the vehicle's handling, especially the steering wheel's power feel. This is different from the situation where most passenger cars and commercial vehicles travel on flat asphalt roads. The existing electric power steering system EPS is mainly designed for vehicles on flat road conditions, requiring the output power to be smooth and linear. However, when an all-terrain vehicle is driving on a rugged road, the driver may face the phenomenon of being "hit" by the steering wheel, that is, the road feedback force is directly transmitted to the steering wheel, causing the vehicle to be unstable or out of control, seriously affecting driving safety.

[0003] The existing electric power steering (EPS) system mainly relies on the torque sensor and motor controller to work together to adjust the power. The system will provide a certain amount of steering damping according to the driver's operation signal, but the feedback control effect on the reverse force caused by uneven road surface is poor. In this case, when the driver passes through bumpy sections, it is easy to encounter the reaction force of the steering wheel, resulting in difficulty in operation or even loss of control. Summary of the invention

[0004] The purpose of the present invention is to provide a method for suppressing road force feedback of a power steering system, so as to solve the problem of difficulty in operating the steering wheel or even loss of control on bumpy roads in the prior art.

[0005] To this end, the present invention provides a method for suppressing road force feedback of a power steering system, the method comprising:

[0006] Obtain the torque signal of the power steering system and the speed signal of the steering motor;

[0007] Determining whether the torque signal and the speed signal change in the same direction;

[0008] In response to the torque signal and the speed signal having different change directions, converting the torque signal and the speed signal into a frequency domain by Fourier transform;

[0009] The converted frequency domain signal is compared with the frequency threshold, and the frequency domain signal is divided into a high frequency part and a low frequency part;

[0010] Determine a high frequency weight and a low frequency weight for the high frequency part and the low frequency part respectively;

[0011] Determining a frequency weight comprehensively according to the high frequency weight and the low frequency weight;

[0012] The suppression coefficient for the output current of the steering motor is determined according to the rotation speed of the steering motor and the frequency weight, and the feedback suppression of the road force is performed using the product of the suppression coefficient and the current control current as the target current.

[0013] As a preferred technical solution of the method for suppressing road force feedback of a power steering system, determining whether the changing directions of the torque signal and the speed signal are consistent includes:

[0014] Get the torque signal T(t) and the speed signal W(t) of the steering motor,

[0015] like , determining that the torque signal and the speed signal change in the same direction;

[0016] like , determining that the changing directions of the torque signal and the speed signal are inconsistent.

[0017] As a preferred technical solution of the method for suppressing road force feedback of a power steering system, the high frequency part satisfies that the frequency f is greater than the frequency threshold f th , the high-frequency weight of the high-frequency part is determined by the following formula:

[0018] ,

[0019] Where |T(f)| represents the amplitude of the torque signal at different frequencies f, |W(f)| represents the amplitude of the speed signal at different frequencies f, and N 高频 is the number of frequencies in the high frequency part.

[0020] As a preferred technical solution of the method for suppressing road force feedback of a power steering system, the low-frequency part satisfies that the frequency f is less than or equal to the frequency threshold f th , the low-frequency weight of the low-frequency part is determined by the following formula:

[0021] ,

[0022] Among them, N 低频 is the number of frequencies in the low frequency part.

[0023] As a preferred technical solution of the method for suppressing road force feedback of a power steering system, the frequency weight is determined by the following formula:

[0024] ,

[0025] Wherein, α and β are preset coefficients for adjusting the weights of high frequency and low frequency, respectively, and α>β.

[0026] As a preferred technical solution of the method for suppressing road force feedback of a power steering system, the method of determining the suppression coefficient for the output current of the steering motor according to the rotation speed of the steering motor and the frequency weight includes:

[0027] Comparing the rotation speed n of the steering motor with preset rotation speed thresholds n1, n2 and n3;

[0028] For the states where the speed n of the steering motor is n3≤n, n2≤n<n3, n1≤n<n2, and n<n1, different suppression formulas are set to determine the suppression coefficient for the output current of the steering motor, and the suppression coefficient is positively correlated with the speed of the steering motor;

[0029] Among them, n1<n2<n3.

[0030] As a preferred technical solution of the road force feedback suppression method of the power steering system, if the speed n of the steering motor is in the state of n3≤n, the suppression coefficient is determined by the following formula:

[0031] .

[0032] As a preferred technical solution of the road force feedback suppression method of the power steering system, if the speed n of the steering motor is in the state of n2≤n<n3, the suppression coefficient is determined by the following formula:

[0033] ,

[0034] Wherein, |ncurrent| represents the absolute value of the current rotation speed of the steering motor, K1 and K2 are respectively preset suppression coefficients and 1<K1<K2.

[0035] As a preferred technical solution of the road force feedback suppression method of the power steering system, if the speed n of the steering motor is in the state of n1≤n<n2, the suppression coefficient is determined by the following formula:

[0036] .

[0037] As a preferred technical solution of the road force feedback suppression method of the power steering system, if the rotation speed n of the steering motor is in the state of n<n1, the suppression coefficient is 1.

[0038] The beneficial effects of the present invention are:

[0039] The present invention provides a method for suppressing road force feedback of a power steering system, which is applicable to an electric power steering system of an all-terrain vehicle. Through real-time monitoring and analysis of torque signals and motor speed signals, the working conditions of the road surface on which the vehicle is traveling are identified, the direction of force transmission is determined, and the feedback force from the road surface is effectively suppressed. By identifying the direction of the road surface feedback force in real time and dynamically adjusting the current suppression coefficient according to different road conditions, the "hand-beating" phenomenon of the steering wheel is effectively reduced, and driving safety is improved. Under all-terrain complex roads, the system can intelligently adjust the power steering feel to prevent the vehicle from losing control due to road impact, so that the driver can still maintain stable control on bumpy or low-adhesion roads. The dynamic adjustment mechanism of the motor speed and the suppression coefficient ensures that the system can flexibly adapt to different road conditions and realize intelligent driving experience. The suppression coefficient can be adjusted according to the complexity of the current road conditions to reduce the impact of the road surface on the steering wheel and improve the stability of control. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of a method for suppressing road force feedback of a power steering system in an embodiment of the present invention;

[0041] Figure 2 is a working flow chart of road force feedback suppression in an embodiment of the present invention;

[0042] Figure 3 It is a flow chart for determining whether the changing directions of the torque signal and the speed signal are consistent in an embodiment of the present invention;

[0043] Figure 4 The flowchart of determining the suppression coefficient for the output current of the steering motor in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0048] See also Figure 1 and Figure 2 As shown, this embodiment provides a method for suppressing road force feedback of a power steering system, comprising:

[0049] Step S1, obtaining a torque signal of a power steering system and a speed signal of a steering motor;

[0050] Step S2, determining whether the changing directions of the torque signal and the speed signal are consistent;

[0051] Step S3, in response to the torque signal and the speed signal having different change directions, converting the torque signal and the speed signal into the frequency domain by Fourier transform;

[0052] Step S4, comparing the converted frequency domain signal with the frequency threshold, and dividing the frequency domain signal into a high frequency part and a low frequency part;

[0053] Step S5, determining a high frequency weight and a low frequency weight for the high frequency part and the low frequency part respectively;

[0054] Step S6, comprehensively determining the frequency weight according to the high frequency weight and the low frequency weight;

[0055] Step S7, determining the suppression coefficient for the output current of the steering motor according to the rotation speed and frequency weight of the steering motor, and using the product of the suppression coefficient and the current control current as the target current to perform feedback suppression of the road force.

[0056] In the above embodiment, the working conditions of the road surface on which the vehicle is driving are identified, the direction of force transmission is determined, and the feedback force from the road surface is effectively suppressed by real-time monitoring and analysis of the torque signal and the speed signal of the steering motor. By real-time identification of the direction of the feedback force from the road surface and dynamically adjusting the suppression coefficient of the current according to different road conditions, the "hand-hitting" phenomenon of the steering wheel is effectively reduced, and driving safety is improved. Under all-terrain and complex road conditions, the system can intelligently adjust the power-assisting feel to prevent the vehicle from losing control due to road impact, so that the driver can still maintain stable control on bumpy or low-adhesion roads. The dynamic adjustment mechanism of the speed and suppression coefficient of the steering motor ensures that the system can flexibly adapt to different road conditions and realize intelligent driving experience. The suppression coefficient can be adjusted according to the complexity of the current road conditions, reducing the impact of the steering wheel on the road surface and improving the stability of control.

[0057] Specifically, the EPS system collects real-time input torque signals (T(t)) through the torque sensor, and calculates the steering motor speed signal (W(t)) in real time through the rotor angle sensor. The linkage analysis of the two signals is the basis for judging the road conditions of the vehicle, and determining whether the change directions of the torque signal and the speed signal are consistent, including:

[0058] Step S21, obtaining the torque signal T(t) and the speed signal W(t) of the steering motor,

[0059] Step S22, determining whether the torque signal T(t) and the speed signal W(t) of the steering motor are both increasing or decreasing:

[0060] When the vehicle is driving on a smooth road, the torque signal generated by the driver operating the steering wheel and the speed signal of the steering motor change synchronously, and the two have the same direction, that is, both increase or decrease. Therefore: , determine that the changing directions of the torque signal and the speed signal are consistent;

[0061] When the vehicle is driving on a bumpy road, the uneven road feedback force is transmitted back to the input shaft through the output shaft, causing the torque signal and the steering motor speed signal to change in opposite directions. , it is determined that the changing directions of the torque signal and the speed signal are inconsistent.

[0062] In detail, the torque sensor can accurately identify the torque signal through Hall effect sampling. Its working principle is to detect the changes in the N-pole and S-pole magnetic field areas: when the input shaft rotates clockwise, the N-pole magnetic field area increases, and the torque signal value increases. When the input shaft rotates counterclockwise or the force is transmitted clockwise from the output shaft to the input shaft, the S-pole magnetic field area increases and the torque signal decreases. The speed signal of the steering motor is calculated through the rotor angle. Regardless of whether the force is transmitted clockwise from the input shaft to the output shaft or counterclockwise from the output shaft to the input shaft, the direction of rotation is consistent for the steering motor. Through this feature, the present invention can more accurately judge and control the direction of the feedback force of uneven road surface.

[0063] Since the torque signal (T(t)) and the speed signal (W(t)) of the steering motor collected by EPS in real time are expressed in the time domain, in order to analyze the frequency characteristics, the fast Fourier transform (FFT) is used to convert these time domain signals into the frequency domain.

[0064] The frequency domain representation of the torque signal is: T(f) = FFT(T(t));

[0065] The frequency domain representation of the steering motor speed signal is: W(f) = FFT(W(t)); and then define the frequency threshold f th , the frequency is divided into low frequency and high frequency. The low frequency signal indicates a relatively stable road condition, the vehicle runs smoothly, and the road feedback force is small. The high frequency signal corresponds to the bumpy road or sudden impact force feedback, and there will be significant fluctuations. By taking a weighted average of the feedback signal amplitudes in different frequency bands, the frequency weight is obtained:

[0066] First, the amplitude of each frequency component is calculated. |T(f)| represents the amplitude of the torque signal at different frequencies f, and |W(f)| represents the amplitude of the speed signal of the steering motor at different frequencies f.

[0067] The high frequency part satisfies that the frequency f is greater than the frequency threshold f th , the high-frequency feedback force is more intense, so it is given a higher weight. The high-frequency weight of the high-frequency part is determined by the following formula:

[0068] ,

[0069] Wherein, |T(f)| represents the amplitude of the torque signal at different frequencies f, |W(f)| represents the amplitude of the speed signal at different frequencies f, and Nhighfrequency is the number of frequencies of the high-frequency part.

[0070] The low-frequency part satisfies that the frequency f is less than or equal to the frequency threshold f th , the low-frequency feedback force is relatively stable, so a relatively low weight is set. The low-frequency weight of the low-frequency part is determined by the following formula:

[0071] ,

[0072] Wherein, N low frequency is the number of frequencies in the low frequency part. Exemplarily, the frequency threshold f th is 10Hz.

[0073] As a preferred technical solution of the road force feedback suppression method of the power steering system, the frequency weight is determined by the following formula:

[0074] ,

[0075] Among them, α and β are preset coefficients for adjusting the respective weights of high frequency and low frequency. Because the high-frequency feedback force has a greater impact on the steering wheel, α>β is limited. For example, α is 1.5 and β is 1.2. Of course, it can also be set to other values ​​through actual vehicle calibration.

[0076] The suppression coefficient for the steering motor output current is determined according to the speed and frequency weight of the steering motor, including:

[0077] Step S71, comparing the speed n of the steering motor with preset speed thresholds n1, n2 and n3;

[0078] Step S72, when the speed n of the steering motor is in the state of n3≤n, n2≤n<n3, n1≤n<n2, and n<n1, different suppression formulas are set to determine the suppression coefficient for the output current of the steering motor, and the suppression coefficient is positively correlated with the speed of the steering motor;

[0079] Among them, n1<n2<n3.

[0080] It is understandable that once the system detects that the vehicle has entered a complex road section, it will dynamically adjust the suppression coefficient to reduce the steering wheel's feedback force due to uneven road conditions. The suppression formula is as follows:

[0081] When the absolute value of the steering motor speed is greater than or equal to n3, the suppression current coefficient is set to the maximum value K2. When the road surface is bumpier (i.e., the high-frequency component is higher), the suppression coefficient will increase accordingly with the frequency weight. If the steering motor speed n is in the state of n3≤n, the suppression coefficient is determined by the following formula:

[0082] .

[0083] If the speed n of the steering motor is in the state of n2≤n<n3, the suppression coefficient is calculated according to the linear interpolation method, and the formula is as follows:

[0084] ,

[0085] Wherein, |ncurrent| represents the absolute value of the current rotation speed of the steering motor, K1 and K2 are respectively preset suppression coefficients and 1<K1<K2.

[0086] If the speed n of the steering motor is in the state of n1≤n<n2, the suppression coefficient is calculated according to the linear interpolation method, and the formula is as follows:

[0087] .

[0088] As a preferred technical solution for the road force feedback suppression method of the power steering system, if the speed n of the steering motor is in the state of n<n1, the suppression coefficient is 1. The speed threshold and the preset suppression coefficient are obtained through actual vehicle calibration. In this embodiment, n1 = 600, n2 = 800, n3 = 1000, K1 = 1.15, K2 = 1.30. In the implementation, adaptive adjustments can also be made in combination with the actual scene and calibration requirements. It can be understood that the higher the speed of the steering motor, the higher the output current is required to ensure the stability of the road force suppression. Different adaptive suppression formulas are set for different speed intervals of the steering motor, which can ensure the road force suppression effect while saving energy. The frequency weight of this embodiment represents the stability of the current road surface. The higher the frequency weight, the more unstable the road surface. The corresponding increase in output current can effectively improve the stability of the steering wheel.

[0089] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the device, method and computer program product according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based device that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for suppressing road force feedback of a power steering system, characterized in that: include: Obtain the torque signal of the power steering system and the speed signal of the steering motor; Determining whether the torque signal and the speed signal change in the same direction; In response to the torque signal and the speed signal having different change directions, converting the torque signal and the speed signal into a frequency domain by Fourier transform; The converted frequency domain signal is compared with the frequency threshold, and the frequency domain signal is divided into a high frequency part and a low frequency part; Determine a high frequency weight and a low frequency weight for the high frequency part and the low frequency part respectively; Determining a frequency weight comprehensively according to the high frequency weight and the low frequency weight; The suppression coefficient for the output current of the steering motor is determined according to the rotation speed of the steering motor and the frequency weight, and the feedback suppression of the road force is performed using the product of the suppression coefficient and the current control current as the target current.

2. The method for suppressing road force feedback of a power steering system according to claim 1, characterized in that: Determining whether the torque signal and the speed signal change in the same direction comprises: Get the torque signal T(t) and the motor speed signal W(t), like , determining that the torque signal and the speed signal change in the same direction; like , determining that the changing directions of the torque signal and the speed signal are inconsistent.

3. The method for suppressing road force feedback of a power steering system according to claim 1, characterized in that: The high frequency part satisfies that the frequency f is greater than the frequency threshold f th , the high-frequency weight of the high-frequency part is determined by the following formula: ， Where |T(f)| represents the amplitude of the torque signal at different frequencies f, |W(f)| represents the amplitude of the speed signal at different frequencies f, and N 高频 is the number of frequencies in the high frequency part.

4. The method for suppressing road force feedback of a power steering system according to claim 3, characterized in that: The low-frequency part satisfies that the frequency f is less than or equal to the frequency threshold f th , the low-frequency weight of the low-frequency part is determined by the following formula: ， Among them, N 低频 is the number of frequencies in the low frequency part.

5. The method for suppressing road force feedback of a power steering system according to claim 4, characterized in that: The frequency weight is determined by the following formula: ， Wherein, α and β are preset coefficients for adjusting the weights of high frequency and low frequency, respectively, and α>β.

6. The method for suppressing road force feedback of a power steering system according to claim 1, characterized in that: The step of determining the suppression coefficient for the output current of the steering motor according to the rotation speed of the steering motor and the frequency weight comprises: Comparing the rotation speed n of the steering motor with preset rotation speed thresholds n1, n2 and n3; For the states where the speed n of the steering motor is n3≤n, n2≤n<n3, n1≤n<n2, and n<n1, different suppression formulas are set to determine the suppression coefficient for the output current of the steering motor, and the suppression coefficient is positively correlated with the speed of the steering motor; Among them, n1<n2<n3.

7. The method for suppressing road force feedback of a power steering system according to claim 6, characterized in that: If the speed n of the steering motor is in the state of n3≤n, the suppression coefficient is determined by the following formula: 。 8. The method for suppressing road force feedback of a power steering system according to claim 6, characterized in that: If the speed n of the steering motor is in the state of n2≤n<n3, the suppression coefficient is determined by the following formula: ， Wherein, |ncurrent| represents the absolute value of the current rotation speed of the steering motor, K1 and K2 are respectively preset suppression coefficients and 1<K1<K2.

9. The method for suppressing road force feedback of a power steering system according to claim 6, characterized in that: If the speed n of the steering motor is in the state of n1≤n<n2, the suppression coefficient is determined by the following formula: 。 10. The method for suppressing road force feedback of a power steering system according to claim 6, characterized in that: If the speed n of the steering motor is in the state of n<n1, the suppression coefficient is 1.

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