Motor stalling noise reduction method of vehicle-mounted electronic power steering system

Abstract

The invention discloses a motor stalling noise reduction method for a vehicle-mounted electronic power steering (EPS) system. The motor stalling noise reduction method comprises the following steps: step 1, constructing a vehicle-mounted EPS motor stalling noise optimization system; 2, a signal acquisition module acquires a steering wheel torque signal, a steering wheel rotating speed signal and a vehicle speed signal of the vehicle in real time; 3, a steering protection mode judgment module conducts mode judgment according to the steering wheel torque signal, the steering wheel rotating speed signal and the vehicle speed signal, and when the steering wheel torque signal, the steering wheel rotating speed signal and the vehicle speed signal are all smaller than the corresponding judgment threshold values, and the steering wheel torque signal, the steering wheel rotating speed signal and the vehicle speed signal meet the conditions at the same time and reach the set time T, a steering protection mode is started; otherwise, entering a common mode; 4a, in the rudder protection mode, the filtering module carries out deep filtering processing on the signals through a stability control filtering unit, a torque sensor filtering unit and a motor bandwidth filtering unit; and 4b, in the common mode, the filtering module carries out common filtering processing on the signal. The method has the effect that the motor stalling noise of the vehicle-mounted electronic power-assisted steering system can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power steering systems, and particularly to a method for reducing the motor stall noise of an in-vehicle electric power steering system. Background Art

[0002] In the current in-vehicle electric power steering system EPS solution, an analog torque sensor is adopted. There is a fluctuation of about 30 mNm in the torque sensor. When passing through the power amplification module, the fluctuation at the driving motor end is 0.6 amperes, resulting in obvious fluctuations in the motor rotor, and thus there are jitters and noises similar to "boiling water" in the motor under the stall condition.

[0003] Currently, the method for optimizing the motor stall noise is filtering without distinguishing the working scenarios: using a torque sensor, a stability control module, and a motor belt block control module for segmented filtering. However, since the high-frequency part of the torque sensor in the in-vehicle EPS system also represents the driver's demand, too much filtering is likely to cause distortion of the driver's intention and there are stability problems in the system. Therefore, engineers can observe that the motor stall noise is significantly improved under the condition of extreme filtering, but due to the stability problems, it cannot be implemented in engineering applications, resulting in the inability to further optimize the motor stall noise, and thus it is difficult to meet the requirements of end customers for low noise in in-vehicle devices. Summary of the Invention

[0004] A method for reducing the motor stall noise of an in-vehicle electric power steering system provided by the present invention can effectively reduce the motor stall noise of the in-vehicle electric power steering system.

[0005] To achieve the above object, a key point of a method for reducing the motor stall noise of an in-vehicle electric power steering system provided by the present invention includes the following steps:

[0006] Step 1: Construct an in-vehicle EPS motor stall noise optimization system. The in-vehicle EPS motor stall noise optimization system is provided with a signal acquisition module, the signal acquisition module is connected to a steering assist mode judgment module, and the steering assist mode judgment module is connected to a filtering module;

[0007] Step 2: The signal acquisition module real-time acquires the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal of the vehicle, and transmits them to the steering assist mode judgment module;

[0008] Step 3: The steering assist mode judgment module makes a mode judgment according to the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal. When the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal are all less than the corresponding judgment thresholds, and the three conditions are simultaneously satisfied for a set time T, it enters the steering assist mode; otherwise, it enters the normal mode;

[0009] Step 4a: In the steering assist mode, the filtering module deeply filters the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal through the stability control filtering unit, the torque sensor filtering unit, and the motor bandwidth filtering unit;

[0010] Step 4b: In the normal mode, the torque sensor filtering unit, the stability control filtering unit, and the motor bandwidth filtering unit in the filtering module perform normal filtering on the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal.

[0011] Through the above design, by designing the steering assist mode determination module, when the steering assist mode determination condition is met, it enters the steering assist mode. In the steering assist mode, the torque sensor signal is smoothed, and then the processed torque signal is given to the subsequent filtering module, and the optimized boiling water noise is achieved through deep filtering. If the steering assist mode determination condition is not met, it switches to the normal mode to ensure that the normal performance and stability are not affected in the normal mode.

[0012] In the normal mode, due to the need to consider stability issues, it is impossible to use the filtering module for deep filtering, so the boiling water noise cannot be optimized to the customer satisfaction level. In the accurately identified steering assist mode working condition, since the steering wheel basically does not rotate, there is no need to consider the issues of precise feel and stability, so the filtering module can be used for deep filtering.

[0013] Preferably: In the step 2, the signal acquisition module receives the steering wheel torque signal and the steering wheel rotation speed signal from the torque angle sensor TAS; the signal acquisition module also receives the vehicle speed signal from the vehicle speed sensor via the CAN bus.

[0014] The torque angle sensor TAS is provided with a torque sensor and an angle sensor. The torque sensor is used to collect the steering wheel torque signal, and the angle sensor is used to collect the steering wheel rotation speed signal.

[0015] The steering wheel torque signal represents the hand torque of the driver turning the steering wheel, the steering wheel rotation speed signal represents the rotation speed of the driver turning the steering wheel, and the vehicle speed signal represents the vehicle speed of the whole vehicle.

[0016] Preferably: In the step 3, the determination conditions for entering the steering assist mode are as follows:

[0017] ① The absolute value of the steering wheel rotation speed signal < the steering wheel rotation speed threshold;

[0018] ② The absolute value of the vehicle speed signal < the vehicle speed threshold;

[0019] ③ The absolute value of the steering wheel torque signal < the steering wheel torque threshold;

[0020] ④All of the above three conditions are satisfied for the set time T;

[0021] If the above four conditions are met, the steering holding mode is entered;

[0022] The condition for exiting the steering holding mode is that if any of the above four conditions is not satisfied, it will return to the normal mode.

[0023] Since the working condition described in the steering holding mode is to keep the hand torque constant for a period of time at any position of the steering wheel, the driver can hear the boiling water noise being excited. Therefore, according to the described working condition, simultaneously satisfying the above four conditions is defined as the working condition of the steering holding mode.

[0024] Preferably, a signal data processing module is further provided between the steering holding mode judgment module and the filtering module.

[0025] Preferably, in the steering holding mode, the signal data processing module calculates the average value of the N steering wheel torque signals collected within the time period T to reduce the torque fluctuation of the motor.

[0026] Since the essence of the boiling water noise is the torque fluctuation of the torque sensor causing the torque fluctuation of the motor shaft after passing through the power amplification module, and there is originally a torque fluctuation of 30 mNm in the signal itself. The algorithm of the present invention for calculating the average value of 50 torque signal data collected within the time T under the working condition of the steering holding mode reduces the torque fluctuation of 30 mNm to 20 mNm, thereby reducing the torque fluctuation of the motor to achieve the purpose of optimizing the boiling water sound.

[0027] Preferably, the filtering module is provided with a stability control filtering unit, a torque sensor filtering unit, a basic assistance unit, an assistance limit unit, a drive chip control unit, and a motor bandwidth filtering unit connected in sequence.

[0028] The basic assistance unit is used to proportionally map the steering wheel torque signal to the motor torque output; the assistance limit unit is used to limit the amplified assistance for some safety situations; the drive chip control unit is used to convert the torque of the motor into a motor PWM wave, and then control the output of the motor.

[0029] The beneficial effects of the present invention: The present invention adds a condition judgment to identify the working condition of motor blockage (EPS steering holding) and enter the steering holding mode. After identifying and entering the steering holding mode, the boiling water noise is controlled to a lower level by means of torque sensor filtering, stability control filtering, and motor bandwidth filtering, so as to achieve the purpose of further optimizing the motor stall noise only in the steering holding mode. And the steering holding mode is exited by judging the condition, and after exiting the steering holding mode, the vehicle-mounted EPS system can work in the original system, so as to ensure that the EPS system can smoothly switch back to normal operation after exiting the steering holding mode.

[0030] The invention has the advantages of low execution cost and short application cycle, and can be applied to various EPS projects in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process logic block diagram of the present invention;

[0032] Figure 2 This is a block diagram of the judgment condition of the steering mode in the embodiment;

[0033] Figure 3 This is the structural block diagram of the filtering module;

[0034] Figure 4 This is a comparison diagram of torque signal fluctuations in the normal mode and the rudder-keeping mode in the embodiment;

[0035] Figure 5 This is a comparison diagram of torque sensor filtering in the normal mode and the rudder-keeping mode in the embodiment;

[0036] Figure 6 This is a comparison diagram of motor bandwidth control filtering in the normal mode and the rudder-keeping mode in the embodiment;

[0037] Figure 7 This is a diagram showing the effect of noise optimization in the embodiment. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific examples. The following examples or drawings are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0039] like Figure 1 As shown: A method for reducing the motor stall noise of a vehicle-mounted electronic power steering system, comprising the following steps:

[0040] Step 1: constructing a vehicle-mounted EPS motor stall noise optimization system, wherein the vehicle-mounted EPS motor stall noise optimization system is provided with a signal acquisition module, the signal acquisition module is connected to a steering mode judgment module, and the steering mode judgment module is connected to a filtering module;

[0041] Step 2: The signal acquisition module acquires the steering wheel torque signal, steering wheel speed signal and vehicle speed signal of the vehicle in real time, and transmits them to the steering mode determination module;

[0042] Step 3: The steering holding mode judgment module performs mode judgment according to the steering wheel torque signal, the steering wheel speed signal and the vehicle speed signal. When the steering wheel torque signal, the steering wheel speed signal and the vehicle speed signal are all less than the corresponding judgment thresholds, and the three conditions are met at the same time for a set time T, the steering holding mode is entered; otherwise, the normal mode is entered;

[0043] Step 4a: In the steering assist mode, the filtering module deeply filters the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal through the stability control filtering unit, the torque sensor filtering unit, and the motor bandwidth filtering unit;

[0044] Step 4b: In the normal mode, the torque sensor filtering unit, the stability control filtering unit, and the motor bandwidth filtering unit in the filtering module perform normal filtering on the steering wheel torque signal, the steering wheel rotation speed signal, and the vehicle speed signal.

[0045] More filtering is performed in the steering assist mode to optimize the noise. Because in the normal mode, the EPS system needs to balance system stability, which limits the degree of filtering in the normal mode.

[0046] In the step 2, the signal acquisition module receives the steering wheel torque signal and the steering wheel rotation speed signal from the torque angle sensor TAS; the signal acquisition module also receives the vehicle speed signal from the vehicle speed sensor via the CAN bus.

[0047] In the step 3, as Figure 2 shown, the determination conditions for entering the steering assist mode are as follows:

[0048] ① The absolute value of the steering wheel rotation speed signal < the steering wheel rotation speed threshold (recommended 10 deg / s);

[0049] ② The absolute value of the vehicle speed signal < the vehicle speed threshold (recommended 3 pkh);

[0050] ③ The absolute value of the steering wheel torque signal < the steering wheel torque threshold (recommended 0.2 Nm);

[0051] ④ The above three conditions are simultaneously satisfied for the set time T;

[0052] If the above four conditions are satisfied, the steering assist mode is entered;

[0053] The condition for exiting the steering assist mode is that if any of the above four conditions is not satisfied, it will return to the normal mode.

[0054] A signal data processing module is also arranged between the steering assist mode judgment module and the filtering module.

[0055] In the steering assist mode, the signal data processing module calculates the average value of all the steering wheel torque signals collected within the time T, that is, performs smoothing processing on the steering wheel torque signal to reduce the torque fluctuation of the motor.

[0056] The value range of the time T is [20, 120] ms; the reduction range of the torque fluctuation of the motor is [2 / 3] of the original.

[0057] For example, the average value of 50 steering wheel torque signals collected within 100 ms is calculated, and the torque fluctuation originally at 30 mNm is reduced to 20 mNm.

[0058] As Figure 4 shown, since the essence of the boiling water noise is the torque fluctuation of the motor shaft caused by the fluctuation of the torque sensor after passing through the power amplification module, there is originally a torque fluctuation of 30 mNm in the signal itself as in the existing state. The algorithm of the present invention for calculating the average value of 50 torque signal data collected within 100 ms under the condition of the rudder-holding mode reduces the torque fluctuation of 30 mNm to 20 mNm, thereby reducing the torque fluctuation of the motor to achieve the purpose of optimizing the boiling water sound.

[0059] As Figure 3 shown, the filtering module is provided with a stability control filtering unit, a torque sensor filtering unit, a basic boost unit, a boost limit unit, a drive chip control unit, and a motor bandwidth filtering unit connected in sequence.

[0060] In the normal mode, due to the need to consider stability issues, it is impossible to use the torque sensor filtering unit, the stability control filtering unit, and the motor bandwidth control filtering unit for deep filtering, so the boiling water noise cannot be optimized to the customer's satisfactory level. In the accurately identified rudder-holding mode of the present invention, since the steering wheel basically does not rotate, there is no need to consider the issues of feel accuracy and stability, so the torque sensor filtering unit, the stability control filtering unit, and the motor bandwidth control filtering unit can be used for deep filtering.

[0061] The comparison of torque sensor filtering is as Figure 5 shown, and the comparison of motor bandwidth control filtering is as Figure 6 shown.

[0062] As Figure 7 shown, from the optimization results of the rudder-holding mode, objectively, the rudder-holding mode can average optimize 2 dB(A). Subjectively, the effect of the noise optimization is that the boiling water noise in the rudder-holding mode is optimized from 6.75 points to 7.25 points, reaching the best in the same level of low-cost analog signal sensors.

[0063] The present invention makes full use of the filtering module for deep filtering in the accurately identified rudder-holding mode, effectively reducing the current fluctuation at the motor end and the torque fluctuation of the motor, thereby realizing the optimization of the boiling water noise.

[0064] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing the motor stall noise of a vehicle-mounted electric power steering system, characterized in that It includes the following steps: Step 1: Construct an in-vehicle EPS motor stall noise optimization system. The in-vehicle EPS motor stall noise optimization system is provided with a signal acquisition module, the signal acquisition module is connected to a steering assist mode judgment module, and the steering assist mode judgment module is connected to a filtering module; Step 2: The signal acquisition module real-time acquires the steering wheel torque signal, steering wheel speed signal and vehicle speed signal of the vehicle, and transmits them to the steering assist mode judgment module; Step 3: The steering assist mode judgment module makes a mode judgment according to the steering wheel torque signal, steering wheel speed signal and vehicle speed signal. When the steering wheel torque signal, steering wheel speed signal and vehicle speed signal are all less than the corresponding determination thresholds, and the three conditions are simultaneously satisfied for a set time T, it enters the steering assist mode; otherwise, it enters the normal mode; Step 4a: In the steering assist mode, the filtering module deeply filters the steering wheel torque signal, steering wheel speed signal and vehicle speed signal through a stability control filtering unit, a torque sensor filtering unit and a motor bandwidth filtering unit; Step 4b: In the normal mode, the torque sensor filtering unit, stability control filtering unit and motor bandwidth filtering unit in the filtering module perform normal filtering on the steering wheel torque signal, steering wheel speed signal and vehicle speed signal.

2. The method for reducing the motor stall noise of the in-vehicle electric power steering system according to claim 1, wherein: In Step 2, the signal acquisition module receives the steering wheel torque signal and steering wheel speed signal from the torque angle sensor TAS; the signal acquisition module also receives the vehicle speed signal from the vehicle speed sensor via the CAN bus.

3. The method for reducing the motor stall noise of the in-vehicle electric power steering system according to claim 1, wherein: In Step 3, the determination conditions for entering the steering assist mode are as follows: ① The absolute value of the steering wheel speed signal < the steering wheel speed threshold; ② The absolute value of the vehicle speed signal < the vehicle speed threshold; ③ The absolute value of the steering wheel torque signal < the steering wheel torque threshold; ④ The above three conditions are simultaneously satisfied for a set time T; If the above four conditions are satisfied, it enters the steering assist mode; The condition for exiting the steering assist mode is that any one of the above four conditions is not satisfied, and it returns to the normal mode.

4. The method for reducing the motor stall noise of the in-vehicle electric power steering system according to claim 1, wherein: A signal data processing module is also provided between the steering assist mode judgment module and the filtering module.

5. The method for reducing the motor stall noise of the in-vehicle electric power steering system according to claim 4, characterized in that: In the steering assist mode, the signal data processing module calculates the average value of the N steering wheel torque signals collected within the time period T to reduce the torque fluctuation of the motor.

6. The method for reducing the motor stall noise of the in-vehicle electric power steering system according to claim 1, characterized in that: The filtering module is provided with a stability control filtering unit, a torque sensor filtering unit, a basic assist unit, an assist limit unit, a drive chip control unit and a motor bandwidth filtering unit connected in sequence.

Images