Stepless steering mode switching method for electric power steering system

Abstract

The invention relates to the technical field of steering systems, in particular to a stepless steering mode switching method for an electric power steering system. The method comprises the following steps: acquiring a driver hand torque, a steering wheel steering angle and a direction angular velocity signal through a sensor; obtaining a whole vehicle speed signal and a steering mode switching gear signal through a signal receiving device; a basic power assisting module, an active aligning module and an active damping module are adjusted through a calculation module on the basis of the current driving working condition and a steering gear signal, the request ratio of all the modules to a driving motor of the electric power steering system is changed, and the purpose of changing the steering hand feeling is achieved; a steering motor is driven to perform auxiliary steering through a motor driving module; the multi-gear stepless switching mode of the steering mode is achieved by adjusting the proportion of all the modules of the electric power steering system.

Description

Technical Field

[0001] The invention relates to the technical field of steering systems, in particular to a method for steplessly switching steering modes of an electric power steering system. Background Art

[0002] As the automobile market has increasingly higher requirements for driving comfort, electric power steering systems also need to have a variety of steering modes (such as light mode, normal mode, and sports mode, etc.) for drivers to choose from, in order to meet different drivers' steering feel requirements and improve driving comfort.

[0003] Currently, the electric power steering system has a variety of modes to choose from. For example, in the light mode, the electric power steering system will increase the electric power assistance to make the driver's steering lighter; the sports mode will appropriately reduce the electric power assistance, while enhancing functions such as active return and active damping, making the vehicle operation more sporty; and the normal mode will take into account both light comfort and driving sportiness, and select a steering style in the middle.

[0004] However, the number of steering mode options for the current electric power steering system is fixed, for example, there are three modes in total (light mode, normal mode and sports mode), and each mode contains its own unique tuning parameters, so there will be obvious sudden changes in steering feel when switching between modes (for example, when switching from light mode to sports mode, the driver will obviously feel that the steering feel becomes heavier). Although it is possible to continue to increase the number of steering modes (for example, adding light+, sports+, etc.) to cover more steering mode options, too many mode options require the system to store more steering mode tuning parameters, increasing the software and hardware costs. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for steplessly switching steering modes of an electric power steering system, and achieves stepless switching of steering modes in multiple gears by adjusting the ratio of various modules of the electric power steering system.

[0006] To achieve the above object, a method for steplessly switching steering modes of an electric power steering system is designed, the method comprising:

[0007] (1) Obtaining the driver's hand torque, steering wheel angle, and angular velocity signals through sensors;

[0008] (2) obtaining a vehicle speed signal and a steering mode switching position signal through a signal receiving device;

[0009] (3) adjusting the basic power assist module, the active return module, and the active damping module based on the current driving condition and the steering gear position signal through the calculation module, changing the request ratio of each module to the electric power steering system drive motor, thereby achieving the purpose of changing the steering feel;

[0010] (4) driving the steering motor to assist steering through the motor drive module;

[0011] The basic assist module includes a torque frequency division coefficient adjustment factor, a low-frequency assist torque adjustment factor, and a high-frequency gain torque coefficient;

[0012] The active return module includes a return torque adjustment factor and a return angular velocity adjustment factor;

[0013] The active damping module includes an active damping torque adjustment factor.

[0014] The adjustment method of the basic booster module is as follows:

[0015] (1) The driver torque divider in the electric power steering system divides the driver torque according to the torque division coefficient adjustment factor converted from the current steering mode gear signal and outputs high-frequency torque signal and low-frequency torque signal to the basic power steering module. The division calculation is:

[0016] Low-frequency torque signal = frequency division coefficient * driver torque + (1 – frequency division coefficient) * low-frequency torque signal | 上一周期计算值 High-frequency torque signal = driver torque – low-frequency torque signal;

[0017] Among them, the frequency division coefficient = a1*2πf / (a1*2πf+t), where a1 is the torque frequency division coefficient adjustment factor, f is the frequency division frequency adjusted in the default mode, and t is the frequency divider function scheduling period;

[0018] (2) The basic assist module adjusts the high-frequency gain torque according to the high-frequency gain torque adjustment factor converted from the current steering mode gear signal, the high-frequency torque signal, the low-frequency torque signal, and the vehicle speed. The adjustment method is as follows: a two-dimensional table lookup calculation of the high-frequency gain coefficient planned based on the current vehicle speed and the low-frequency torque signal is performed. The high-frequency gain coefficient can be set to increase with the increase of the vehicle speed and increase with the increase of the low-frequency torque to improve the steering flexibility. The calculated high-frequency gain is multiplied by the high-frequency torque signal to obtain the high-frequency gain torque of the default mode. The high-frequency gain torque adjustment factor set based on the current steering gear mode signal is multiplied by the high-frequency gain torque of the default mode to obtain the final high-frequency gain torque.

[0019] (3) The basic power assist module performs low-frequency power assist adjustment according to the low-frequency power assist torque adjustment factor converted from the current steering mode gear signal, the low-frequency torque signal, and the vehicle speed. The adjustment method is as follows:

[0020] The low-frequency assist two-dimensional table lookup calculation is planned based on the current vehicle speed and the low-frequency torque signal. The low-frequency assist torque can be set to increase with the increase of vehicle speed and increase with the increase of low-frequency torque to provide a suitable steering assist torque. The calculated low-frequency assist is multiplied by the low-frequency assist torque adjustment factor set based on the current steering gear mode signal to obtain the final low-frequency assist torque; the basic assist module transmits the adjusted torque to the motor drive module to drive the steering motor for assisted steering.

[0021] The adjustment method of the active return module is as follows:

[0022] (1) The active return module calculates the return angular velocity according to the return angular velocity adjustment factor converted from the current steering mode gear signal, the vehicle speed, and the steering wheel angle. The adjustment method is:

[0023] The return angular velocity is calculated by two-dimensional table lookup based on the current vehicle speed and the steering wheel angle. The return angular velocity can be set to increase with the increase of the angle and decrease appropriately with the increase of the vehicle speed to compensate for the insufficient return at low vehicle speed and suppress the return overshoot at high vehicle speed. The calculated return angular velocity is multiplied by the return angular velocity adjustment factor set based on the current steering gear mode signal to obtain the final target return angular velocity;

[0024] (2) The calculated result is combined with the driver's steering torque and the actual steering wheel angular velocity to calculate the return torque, and the adjustment method is:

[0025] The calculated target return angular velocity and the actual angular velocity are difference calculated, and the calculated difference is multiplied by the return torque conversion coefficient of the default mode to obtain the default return torque, wherein the return torque conversion coefficient can be set to decrease as the driver's steering torque increases, so as to reduce the interference of the return torque on the driver's active steering. The calculated default return torque is multiplied by the return torque adjustment factor set based on the current steering gear mode signal to obtain the final return torque; then the active return module transmits the calculated return torque to the motor drive module to drive the steering motor for auxiliary steering.

[0026] The adjustment method of the active damping module is as follows:

[0027] The active damping module calculates the damping torque according to the active damping torque adjustment factor converted from the current steering mode gear signal, vehicle speed, steering wheel angle, steering wheel angle speed, and driver's steering torque. The adjustment method is:

[0028] The default damping torque is planned based on the current vehicle speed and steering wheel angular velocity using a two-dimensional table lookup calculation. The default damping torque can be set to increase with increasing angular velocity and vehicle speed to improve system stability. It can also be set to reduce the damping torque near a small mid-angle to improve the sense of mid-position when driving. The calculated default damping torque is multiplied by the damping torque adjustment factor set based on the current steering gear mode signal to obtain the final damping control torque. The calculated result is transmitted to the motor drive module to drive the steering motor for assisted steering.

[0029] Compared with the prior art, the present invention provides a method for steplessly switching steering modes of an electric power steering system, and realizes a multi-gear stepless switching mode of the steering mode by adjusting the ratio of each module of the electric power steering system. The electric power steering system can cover more mode selections, and the driver can select the steering mode of multiple gears steplessly by means of a knob or a slider.

[0030] Since the driver selects the steering mode by means of a knob or a slider, the electric power steering system can include multiple steering modes (for example, 0 to 100 steering mode selections, where 0 represents the lightest steering mode and 100 represents the sportiest steering mode). At the same time, the steering mode switching of each gear does not need to call its own unique tuning parameters, but instead adjusts the ratio of each module of the electric power steering system. Therefore, the steering mode switching between multiple levels will become very smooth, realizing stepless switching between steering modes. At the same time, the steering mode of each gear no longer includes its own unique tuning parameters, which greatly reduces the storage space demand for the tuning parameters, thereby reducing software and hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a block diagram for calculating and implementing various adjustment factors for switching steering modes of the present invention.

[0032] Figure 2 This is a block diagram of the steering mode switching adjustment principle of the present invention.

[0033] Figure 3 This is a framework diagram of the adjustment method of the basic assist module of the present invention.

[0034] Figure 4 This is a framework diagram of the adjustment method of the active return module of the present invention.

[0035] Figure 5 This is a framework diagram of the adjustment method of the active damping module of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings.

[0037] In order to solve the problem that the total number of steering modes is limited (for example, there are only three modes) and the steering feeling suddenly changes when switching between steering modes, the present invention proposes a method for switching steering modes in multiple gears, and realizes the method of switching steering modes in multiple gears by adjusting the ratio of each module of the electric power steering system. The electric power steering system can cover more mode selections, and the driver can select the steering mode in multiple gears in a stepless manner by means of a knob or a slider.

[0038] Since the driver selects the steering mode by means of a knob or a slider, the electric power steering system can include multiple steering modes (for example, 0 to 100 steering mode selections, where 0 represents the lightest steering mode and 100 represents the sportiest steering mode). At the same time, the steering mode switching of each gear does not need to call its own unique tuning parameters, but instead adjusts the ratio of each module of the electric power steering system. Therefore, the steering mode switching between multiple levels will become very smooth, realizing stepless switching between steering modes. At the same time, the steering mode of each gear no longer includes its own unique tuning parameters, which greatly reduces the storage space demand for the tuning parameters, thereby reducing software and hardware costs.

[0039] The stepless switching steering mode of the present invention will set at least six adjustment factors, namely "torque division coefficient adjustment factor of basic power assist module", "low-frequency power assist torque adjustment factor of basic power assist module", "high-frequency gain torque adjustment factor of basic power assist module", "active return angular velocity adjustment factor of active return module", "active return torque adjustment factor of active return module" and "active damping torque adjustment factor of active damping module", as shown in Table 1.

[0040] Table 1

[0041]

[0042] All the adjustment factors will be smoothly transitioned based on the steering mode gear signal obtained by the system (for example, the gears of 0 to 100 as shown in the table above, where gear 0 represents the lightest steering mode and gear 100 represents the most sporty steering mode). When the steering mode is set to normal mode, the steering gear signal received is the normal gear 50 gear. At gear 50, all adjustment factors are 100% by default.

[0043] When the steering mode requirement is lighter, the steering mode gear signal becomes smaller, the "torque division coefficient adjustment factor of the basic power assist module", "low-frequency power assist torque adjustment factor of the basic power assist module" and "high-frequency gain torque adjustment factor of the basic power assist module" increase linearly, and the "active return angular velocity adjustment factor of the active return module", "active return torque adjustment factor of the active return module" and "active damping torque adjustment factor of the active damping module" decrease linearly to provide an easier steering feel.

[0044] When the steering mode requires a more sporty style, the steering mode gear signal becomes larger, the "torque division coefficient adjustment factor of the basic power-assisting module", "low-frequency power-assisting torque adjustment factor of the basic power-assisting module" and "high-frequency gain torque adjustment factor of the basic power-assisting module" decrease linearly, and the "active return angular velocity adjustment factor of the active return module", "active return torque adjustment factor of the active return module" and "active damping torque adjustment factor of the active damping module" increase linearly to provide a more stable and sporty steering style.

[0045] At the same time, each adjustment factor can be additionally modified based on the current vehicle speed to meet different requirements for steering modes at different vehicle speeds, such as Figure 1 shown.

[0046] Based on the current vehicle speed and steering mode gear signal, this solution will calculate at least six adjustment factors to adjust the basic power module, active return module and active damping module to achieve the purpose of infinitely switching the steering mode in multiple gears, such as Figure 2 shown.

[0047] The method includes: (1) obtaining the driver's hand torque, steering wheel steering angle and directional angular velocity signal through a sensor; (2) obtaining the vehicle speed signal and steering mode switching gear signal through a signal receiving device; (3) adjusting the basic power assist module, the active return module and the active damping module based on the current driving condition and the steering gear signal through a calculation module, changing the request ratio of each module to the electric power steering system drive motor, so as to achieve the purpose of changing the steering feel; (4) driving the steering motor through the motor drive module to assist the steering.

[0048] The adjustment factors involved in the basic assist module include "torque division coefficient adjustment factor of the basic assist module", "low-frequency assist torque adjustment factor of the basic assist module" and "high-frequency gain torque adjustment factor of the basic assist module", such as Figure 3 shown.

[0049] Adjustment method of basic power-assist module: The driver torque divider in the electric power steering system divides the driver torque according to the torque division coefficient adjustment factor converted from the current steering mode gear signal, and outputs high-frequency torque signal and low-frequency torque signal to the basic power-assist module. The basic power-assist module adjusts the high-frequency gain torque according to the high-frequency gain torque adjustment factor converted from the current steering mode gear signal, the high-frequency torque signal, the low-frequency torque signal, and the vehicle speed. The adjustment method is: a two-dimensional table lookup calculation of the high-frequency gain coefficient planned based on the current vehicle speed and the low-frequency torque signal. The high-frequency gain coefficient can be set to increase with the increase of vehicle speed and increase with the increase of low-frequency torque to improve steering flexibility. The calculated high-frequency gain is multiplied by the high-frequency torque signal to obtain the high-frequency gain torque of the default mode. The high-frequency gain torque adjustment factor set based on the current steering gear mode signal is multiplied by the high-frequency gain torque of the default mode to obtain the final high-frequency gain torque. The basic power-assist module adjusts the low-frequency power-assist according to the low-frequency power-assist torque adjustment factor converted from the current steering mode gear signal, the low-frequency torque signal and the vehicle speed. The adjustment method is as follows: a two-dimensional lookup table calculation of the low-frequency power-assist is planned based on the current vehicle speed and the low-frequency torque signal. The low-frequency power-assist torque can be set to increase with the increase of vehicle speed and increase with the increase of low-frequency torque to provide a suitable steering assist torque. The calculated low-frequency power-assist is multiplied by the low-frequency power-assist torque adjustment factor set based on the current steering gear mode signal to obtain the final low-frequency power-assist torque. The basic power-assist module transmits the adjusted torque to the motor drive module to drive the steering motor for auxiliary steering.

[0050] The adjustment factors involved in the active self-centering module include the "active self-centering module's self-centering angular velocity adjustment factor" and the "active self-centering module's active self-centering torque adjustment factor", such as Figure 4 shown.

[0051] Adjustment method of active return module: The active return module calculates the return angular velocity according to the return angular velocity adjustment factor converted from the current steering mode gear signal, the vehicle speed, and the steering wheel angle. The adjustment method is: a two-dimensional table calculation of the return angular velocity planned based on the current vehicle speed and the steering wheel angle is performed. The return angular velocity can be set to increase with the increase of the angle and decrease appropriately with the increase of the vehicle speed to compensate for the insufficient return at low speeds and suppress the overshoot at high speeds. The calculated return angular velocity is multiplied by the return angular velocity adjustment factor set based on the current steering gear mode signal to obtain the final The target return angular velocity is calculated; the calculated result is combined with the driver's steering torque and the actual steering wheel angular velocity to calculate the return torque. The adjustment method is: the calculated target return angular velocity and the actual angular velocity are calculated by difference, and the difference is multiplied by the return torque conversion coefficient of the default mode to obtain the default return torque, where the return torque conversion coefficient can be set to decrease as the driver's steering torque increases to reduce the interference of the return torque on the driver's active steering. The calculated default return torque is multiplied by the return torque adjustment factor set based on the current steering gear mode signal to obtain the final return torque. Then the active return module transmits the calculated return torque to the motor drive module to drive the steering motor for auxiliary steering.

[0052] The adjustment factors involved in the active damping module include "active damping module active damping torque adjustment factor", such as Figure 5 shown.

[0053] Adjustment method of active damping module: The active damping module calculates the damping torque according to the active damping torque adjustment factor converted from the current steering mode gear signal, vehicle speed, steering wheel angle, steering wheel angular velocity, and driver's steering torque. The adjustment method is: the default damping torque two-dimensional table calculation is planned based on the current vehicle speed and steering wheel angular velocity. The default damping torque can be set to increase with the increase of angular velocity and the increase of vehicle speed to improve system stability. At the same time, it can be set to reduce the damping torque near the small angle of the middle position to improve the driving sense of the middle position. The calculated default damping torque is multiplied by the damping torque adjustment factor set based on the current steering gear mode signal to obtain the final damping control torque. The calculated result is transmitted to the motor drive module to drive the steering motor for auxiliary steering.

[0054] By adjusting the basic power-assisting module, active return module and active damping module through at least six adjustment factors, the steering mode can be switched continuously in multiple gears.

Claims

1. A method for steplessly switching steering modes of an electric power steering system, the method comprising: (1) Obtaining the driver's hand torque, steering wheel angle, and angular velocity signals through sensors; (2) obtaining a vehicle speed signal and a steering mode switching position signal through a signal receiving device; (3) Based on the current driving conditions and steering gear position signal, the calculation module adjusts the basic power assist module, the active return module, and the active damping module, thereby changing the request ratio of each module to the electric power steering system drive motor to achieve the purpose of changing the steering feel; (4) driving the steering motor to assist steering through the motor drive module; The basic assist module includes a torque frequency division coefficient adjustment factor, a low-frequency assist torque adjustment factor, and a high-frequency gain torque coefficient; The active return module includes a return torque adjustment factor and a return angular velocity adjustment factor; The active damping module includes an active damping torque adjustment factor.

2. The method for steplessly switching steering modes of an electric power steering system according to claim 1, characterized in that: The adjustment method of the basic booster module is as follows: (1) The driver torque divider in the electric power steering system divides the driver torque according to the torque division coefficient adjustment factor converted from the current steering mode gear signal and outputs high-frequency torque signal and low-frequency torque signal to the basic power steering module. The division calculation is: Low-frequency torque signal = frequency division coefficient * driver torque + (1 – frequency division coefficient) * low-frequency torque signal | 上一周期计算值 High-frequency torque signal = driver torque – low-frequency torque signal; Among them, the frequency division coefficient = a1*2πf / (a1*2πf+t), where a1 is the torque frequency division coefficient adjustment factor, f is the frequency division frequency adjusted in the default mode, and t is the frequency divider function scheduling period; (2) The basic power assist module adjusts the high-frequency gain torque according to the high-frequency gain torque adjustment factor converted from the current steering mode gear signal, the high-frequency torque signal, the low-frequency torque signal, and the vehicle speed. The adjustment method is as follows: A two-dimensional table calculation of the high-frequency gain coefficient planned based on the current vehicle speed and the low-frequency torque signal is performed. The high-frequency gain coefficient can be set to increase with the increase of the vehicle speed and increase with the increase of the low-frequency torque to improve the steering flexibility. The high-frequency gain calculated is multiplied by the high-frequency torque signal to obtain the high-frequency gain torque of the default mode. The high-frequency gain torque adjustment factor set based on the current steering gear mode signal is multiplied by the high-frequency gain torque of the default mode to obtain the final high-frequency gain torque. (3) The basic power assist module performs low-frequency power assist adjustment according to the low-frequency power assist torque adjustment factor converted from the current steering mode gear signal, the low-frequency torque signal, and the vehicle speed. The adjustment method is as follows: The low-frequency assist two-dimensional table lookup calculation is planned based on the current vehicle speed and the low-frequency torque signal. The low-frequency assist torque can be set to increase with the increase of vehicle speed and increase with the increase of low-frequency torque to provide a suitable steering assist torque. The calculated low-frequency assist is multiplied by the low-frequency assist torque adjustment factor set based on the current steering gear mode signal to obtain the final low-frequency assist torque; the basic assist module transmits the adjusted torque to the motor drive module to drive the steering motor for assisted steering.

3. The method for steplessly switching steering modes of an electric power steering system according to claim 1, characterized in that: The adjustment method of the active return module is as follows: (1) The active return module calculates the return angular velocity according to the return angular velocity adjustment factor converted from the current steering mode gear signal, the vehicle speed, and the steering wheel angle. The adjustment method is: The return angular velocity is calculated by two-dimensional table lookup based on the current vehicle speed and the steering wheel angle. The return angular velocity can be set to increase with the increase of the angle and decrease appropriately with the increase of the vehicle speed to compensate for the insufficient return at low vehicle speed and suppress the return overshoot at high vehicle speed. The calculated return angular velocity is multiplied by the return angular velocity adjustment factor set based on the current steering gear mode signal to obtain the final target return angular velocity; (2) The calculated result is combined with the driver's steering torque and the actual steering wheel angular velocity to calculate the return torque, and the adjustment method is: The calculated target return angular velocity and the actual angular velocity are subjected to a difference calculation, and the calculated difference is multiplied by the return torque conversion coefficient of the default mode to obtain the default return torque, wherein the return torque conversion coefficient can be set to decrease as the driver's steering torque increases, so as to reduce the interference of the return torque on the driver's active steering, and the calculated default return torque is multiplied by the return torque adjustment factor set based on the current steering gear mode signal to obtain the final return torque; The active self-centering module then transmits the calculated self-centering torque to the motor drive module to drive the steering motor for auxiliary steering.

4. The method for steplessly switching steering modes of an electric power steering system according to claim 1, characterized in that: The adjustment method of the active damping module is as follows: The active damping module calculates the damping torque according to the active damping torque adjustment factor converted from the current steering mode gear signal, vehicle speed, steering wheel angle, steering wheel angle speed, and driver's steering torque. The adjustment method is: The default damping torque is calculated based on the two-dimensional table lookup of the current vehicle speed and the steering wheel angular velocity. The default damping torque can be set to increase with the increase of angular velocity and vehicle speed to improve system stability. At the same time, it can be set to reduce the damping torque near the small angle of the middle position to improve the driving sense of the middle position. The calculated default damping torque is multiplied by the damping torque adjustment factor set based on the current steering gear mode signal to obtain the final damping control torque; The calculated results are transmitted to the motor drive module to drive the steering motor for auxiliary steering.

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