Angle harmonic suppression method for tunnel magnetoresistive effect sensor

Abstract

The invention relates to the technical field of steering systems, in particular to an angle harmonic suppression method for a tunnel reluctance effect sensor. The invention relates to an angle harmonic suppression method for a tunnel magnetoresistive effect sensor. The method comprises angle first-order, third-order and fifth-order harmonic waves. Compared with the prior art, the angle harmonic suppression method for the tunnel reluctance effect sensor realizes suppression of first-order, third-order and fifth-order harmonic waves of motor torque, and reduces angle harmonic signals input into the motor and current harmonic waves, torque harmonic waves, rotating speed harmonic waves and the like caused by the angle harmonic signals to a great extent; and finally, the torque pulsation is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of steering systems, and more specifically, to an angle harmonic suppression method for a tunnel magnetoresistive effect sensor. Background Art

[0002] With the popularization of electric power energy, motors have become indispensable core components in various industries. Motor control technology has also been continuously developed and improved, and people's requirements for motor control performance have been increasing. In many industries, especially in the automotive electric power steering system (EPS), there are high requirements for the accuracy of motor torque output and the suppression of torque ripple.

[0003] In the field of electric power steering, the output torque of the motor is interfered by the input signal to generate harmonic torque. Excessive harmonic torque will affect the comfort of the driver's steering wheel feel and may also introduce noise that can be recognized by the human ear. Therefore, a torque ripple suppression strategy is needed to ensure the smoothness and stability of the motor output torque. Research has found that the low-order torque ripple of the motor is mainly caused by the motor control system. Among them, the tunnel magnetoresistive sensor (TMR) will introduce large first, third, and fifth-order harmonics into the collected rotor position angle under the influence of current. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides an angle harmonic suppression method for a tunnel magnetoresistive effect sensor, which effectively suppresses the harmonics of the rotor position angle collected based on the tunnel magnetoresistive sensor, thereby reducing the motor torque ripple.

[0005] To achieve the above object, an angle harmonic suppression method for a tunnel magnetoresistive effect sensor is designed, including the first, third, and fifth-order harmonics of the angle. The specific method flow is as follows:

[0006] S1. Give a stable speed to the motor under test, and let the motor under test drive the measured motor to make the measured motor reach a stable speed state;

[0007] S2. Give a current command of i d i q to the measured motor through the host computer;

[0008] S3. Record the rotor position angle signal collected by the measured motor for a complete period, and intercept the rotor position angle signal θ n under one mechanical rotation period;

[0009] S4. Calculate a series of corresponding instantaneous speed sets Spd n under this period through the angle signal in one rotation period, where the speed calculation method is the current angle minus the angle at the previous sampling moment and then divided by the sampling period;

[0010] S5. Obtain the average rotational speed Spd in a rotation period through a series of instantaneous rotational speeds in the period. avg , and obtain the average incremental angle Δθ by multiplying the average rotational speed by the sampling period;

[0011] S6. Obtain the ideal angle at each sampling moment in a rotation period through the average incremental angle Δθ.

[0012] S7. Subtract the ideal angle in the period from the actually collected angle to obtain the angle deviation value;

[0013] S8. Conduct Fourier analysis on the angle deviation value to obtain the harmonic phases and harmonic amplitudes of the first, third, and fifth orders; S9. Substitute the obtained harmonic phase and amplitude information into the first-order linear equations between the harmonic amplitude and current, and the harmonic phase and angle to calculate the corresponding slopes ka 1 , ka 3 , ka 5 , kp 3 , kp 5 and intercept ba 1 , ba 3 , ba 5 , bp 1 , bp 3 , bp 5 , and superimpose them on the originally actually collected angle to conduct harmonic suppression of the first, third, and fifth orders.

[0014] In the described step S1, a rotational speed sensor is provided on the motor under test, and the motor under test is provided with a rotational speed loop control. The rotational speed sensor is used to obtain the current rotational speed signal, and the motor to be measured is the motor for angle suppression.

[0015] In the described step S2, a given d i q current command. The selection of the command size refers to the common operating conditions of the steering motor. After compensating the i d i q current domain, relatively comprehensive suppression of the first, third, and fifth order harmonics of the torque can be finally achieved.

[0016] In the described step S4, Spd n is the instantaneous rotational speed at the nth position.

[0017] In the described step S6, is the ideal angle at the nth sampling point in a rotation period.

[0018] In step S6 described above, the ideal angle is obtained by integrating the average rotational speed, or the ideal angle is measured by an angle sensor. The difference between the measured ideal angle and the angle collected by the tunneling magnetoresistive angle sensor is calculated, and Fourier analysis is performed for order suppression.

[0019] Compared with the prior art, the present invention provides an angle harmonic suppression method for a tunneling magnetoresistive effect sensor, which realizes the suppression of the first, third, and fifth order harmonics of the motor torque. This suppression method greatly reduces the angle harmonic signal input into the motor and the current harmonics, torque harmonics, speed harmonics, etc. caused by it, and finally realizes the reduction of torque ripple. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the interference of low-order angle harmonics on the control system.

[0021] Figure 2 It is a time-domain diagram of the rotational speed calculated based on the angle.

[0022] Figure 3 It is a frequency-domain diagram of the rotational speed calculated based on the angle.

[0023] Figure 4 It is an angle error diagram obtained by calculating the difference between the collected angle signal and the ideal signal.

[0024] Figure 5 It is a flowchart of the angle suppression method of the present invention.

[0025] Figure 6 It is a torque comparison diagram before angle suppression.

[0026] Figure 7 It is a torque comparison diagram after angle suppression. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] To achieve the above object, the present invention has proved the influencing factors of the first, third, and fifth order harmonics based on theoretical derivation and a large amount of experimental data:

[0029] 1. The amplitude of the first-order harmonic of the motor is linearly correlated with the amplitude of the bus current in the first order, specifically: Amp_1th = k a1* Ibatt + b a1 ; where Amp_1th is the amplitude of the first-order harmonic; Ibatt is the bus current; k a1 is the slope of the first-order harmonic amplitude with respect to the bus current; b a1 is the intercept of the first-order harmonic amplitude with respect to the bus current.

[0030] 2. There are differences in the phase of the first-order harmonic of the motor among samples, that is, the values are different for different samples. Specifically: Phase_1th = b p1 ; where Phase_1th is the first-order harmonic phase; b p1 is the calibration value of the first-order harmonic phase.

[0031] 3. The amplitudes of the third- and fifth-order harmonics of the motor are linearly correlated with the amplitude of the stator current vector of the motor: Amp_3th = k a3* I s + b a3 ; Amp_5th = k a5* I s + b a5 ; where I s is the amplitude of the stator current vector; Amp_3th is the third-order harmonic amplitude; k a3 is the slope of the third-order harmonic amplitude with respect to the bus current; b a3 is the intercept of the third-order harmonic amplitude with respect to the bus current; Amp_5th is the fifth-order harmonic amplitude; k a5 is the slope of the fifth-order harmonic amplitude with respect to the bus current; b a5 is the intercept of the fifth-order harmonic amplitude with respect to the bus current.

[0032] 4. The phases of the third- and fifth-order harmonics of the motor are linearly correlated with the angle of the stator current vector of the motor: Phase_3th = k p3* θ is + b p3 ; Phase_5th = k p5* θ is + b p5 ; where θ is is the angle of the stator current vector of the motor; Phase_3th is the third-order harmonic phase; k p3 is the slope of the third-order harmonic phase with respect to the angle of the stator current vector of the motor; b p3 is the intercept of the third-order harmonic phase with respect to the angle of the stator current vector of the motor; Phase_5th is the fifth-order harmonic phase; k p5 is the slope of the fifth-order harmonic phase with respect to the angle of the stator current vector of the motor; b p5 is the intercept of the fifth-order harmonic phase with respect to the angle of the stator current vector of the motor.

[0033] The calculation methods for the above motor vector amplitude and current vector angle are as follows: θ is = arctan(i q / i d ); where i d , i q are the d-axis and q-axis currents in the motor rotating coordinate system respectively; I sis the amplitude of the stator current vector; θ is is the angle of the stator current vector.

[0034] It can be known through Figure 1 that since the motor control system is a closed-loop system, when the feedback current requires Park transformation, a rotor angle position signal needs to be input, such as Figure 2 , Figure 3 As shown, if there are harmonics in this angle signal, it will directly affect the harmonic content of the current and the harmonic content of the rotational speed, thereby introducing harmonic torque in the output torque of the motor.

[0035] Therefore, in order to avoid the above problems, it is necessary to process the angle signal in the motor control system. By means of offline harmonic injection, angle harmonics with the same magnitude and opposite direction are injected into the angle for harmonic suppression.

[0036] In order to accurately suppress the first, third, and fifth-order harmonics of the motor, it is necessary to online identify the parameters of the above first, third, and fifth-order harmonics, including the slopes k a1 , k a3 , k a5 , k p3 , k p5 and the intercepts b a1 , b a3 , b a5 , b p1 , b p3 , b p5 for precise compensation. As Figure 4 shown, the angle error is obtained by subtracting the collected angle signal from the ideal signal, and the Fourier analysis is performed on the angle error to extract the first, third, and fifth-order harmonic information contained, and finally the target data is obtained.

[0037] In order to implement the above scheme for suppressing the first, third, and fifth-order harmonics of the angle, as Figure 5 shown, the method steps are as follows: This implementation method is completed based on the motor back-to-back test bench;

[0038] (1) Give the motor under test a stable rotational speed, let the accompanying motor drive the motor under test to rotate, and make the motor under test reach a stable rotational speed state; there is a rotational speed sensor on the accompanying motor, the accompanying motor is equipped with a rotational speed loop control, and the rotational speed sensor is used to obtain the current rotational speed signal, and the motor under test is the motor for angle suppression;

[0039] (2) Give the motor under test an i d i q current command through the upper computer; give an i d i q current command, and the selection of its command size refers to the common working conditions of the steering motor. For the i of the common working conditionsd i q After compensating in the current domain, it can ultimately comprehensively suppress the first, third, and fifth-order harmonics of torque;

[0040] (3) Record the rotor position angle signal collected by the motor under test for a complete segment, and intercept the rotor position angle signal θ under one mechanical rotation period; n ;

[0041] (4) Calculate a series of instantaneous speed sets Spd corresponding to this period through the angle signal under one rotation period, where the speed calculation method is (the current angle minus the angle at the previous sampling moment) divided by the sampling period; Spd n is the instantaneous speed at the nth position; T n is the sampling interval between two sampling angles; samp ;

[0042] (5) Obtain the average speed Spd of this period through a series of instantaneous speeds under one rotation period, and obtain the average incremental angle Δθ by multiplying the average speed by the sampling period; avg ;

[0043] (6) Obtain the ideal angle at each sampling moment under one rotation period through the average incremental angle Δθ. is the ideal angle at the nth sampling point under one rotation period; the ideal angle is obtained by integrating the average speed, or the ideal angle is measured by an angle sensor, and the difference between the measured ideal angle and the angle collected by the tunneling magnetoresistive angle sensor and Fourier analysis are used for order suppression;

[0044] (7) Subtract the ideal angle of this period from the actually collected angle to obtain the angle deviation value;

[0045] (8) Perform Fourier analysis on the angle deviation value to obtain the harmonic phases and harmonic amplitudes of the first, third, and fifth orders; (9) Substitute the obtained harmonic phase and amplitude information into the first-order linear equations between the harmonic amplitude and current, and harmonic phase and angle above to find the corresponding slopes ka 1 、ka 3 、ka 5 、kp 3 、kp 5 and intercepts ba 1 、ba 3 、ba 5 、bp 1 、bp 3 、bp 5 , and superimpose them on the original actually collected angle to perform harmonic suppression of the first, third, and fifth orders.

[0046] Embodiment: As Figure 6 , Figure 7 shown, through the angle harmonic suppression method for the tunnel magnetoresistive effect sensor of the present invention for harmonic compensation, the fluctuation amplitude of the torque after compensation ( Figure 7 ) is significantly reduced compared to the original output torque of the motor ( Figure 6 ), which proves that the method of the present invention has a very obvious effect on angle harmonic suppression.

[0047] Through the angle harmonic suppression method for the tunnel magnetoresistive effect sensor of the present invention, the suppression of the first, third, and fifth order harmonics of the motor torque is realized. This optimization method greatly reduces the angle harmonic signals input into the motor and the current harmonics, torque harmonics, speed harmonics, etc. caused by them, and finally realizes the reduction of torque ripple.

Claims

1. A method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor, including angular first, third, and fifth order harmonics, characterized in that: The specific method flow is as follows: S1, giving the companion motor a stable speed, so that the companion motor drags the motor under test, and the motor under test reaches a stable speed state; S2, the host computer gives the motor under test an i d i q Current instruction; S3, record the rotor position angle signal collected from the motor under test for a complete period, and intercept the rotor position angle signal θ in one of the mechanical rotation cycles n ; S4, calculate a series of instantaneous speed sets Spd corresponding to a rotation cycle through the angle signal of the rotation cycle n , where the speed is calculated by subtracting the angle at the last sampling moment from the current angle and then dividing it by the sampling period; S5, through a series of instantaneous speeds in a rotation cycle, the average speed Spd in the cycle is obtained avg , the average incremental angle Δθ is obtained by multiplying the average speed by the sampling period; S6, by calculating the average incremental angle Δθ, the ideal angle at each sampling moment in a rotation cycle is obtained S7, subtracting the ideal angle under the cycle from the actually collected angle to obtain an angle deviation value; S8, performing Fourier analysis on the angle deviation value to obtain the first-order, third-order, and fifth-order harmonic phases and harmonic amplitudes; S9, substitute the obtained harmonic phase and amplitude information into the first-order linear equations between the above-mentioned harmonic amplitude and current, and harmonic phase and angle, and calculate the corresponding slopes ka1, ka3, ka5, kp3, kp5 and intercepts ba1, ba3, ba5, bp1, bp3, bp5, and superimpose them on the original actually collected angle to perform first, third, and fifth-order harmonic suppression.

2. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In the step S1, a speed sensor is provided on the accompanying motor, and a speed loop control is provided on the accompanying motor. The speed sensor is used to obtain a current speed signal, and the motor to be measured is a motor for angle suppression.

3. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In the step S2, given i d i q The current command, the command size is selected based on the common working conditions of the steering motor. d i q After compensation in the current domain, the first, third and fifth order harmonics of the torque can be more comprehensively suppressed.

4. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In the step S4, Spd n is the instantaneous speed at the nth position.

5. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In the step S6, is the ideal angle of the nth sampling point in one rotation cycle.

6. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In step S6, the ideal angle is obtained by integrating the average rotational speed, or the ideal angle is measured by an angle sensor, and the measured ideal angle is subtracted from the angle collected by the tunnel magnetoresistive angle sensor and the order suppression is performed by Fourier analysis.

7. The method for suppressing angular harmonics for a tunnel magnetoresistive effect sensor according to claim 1, characterized in that: In the step S9, ka1 is the slope of the first-order harmonic amplitude with the bus current, ka3 is the slope of the third-order harmonic amplitude with the bus current, and ka5 is the slope of the fifth-order harmonic amplitude with the bus current; kp3 is the slope of the third-order harmonic phase with the motor stator current vector angle, and kp5 is the slope of the fifth-order harmonic phase with the motor stator current vector angle; and the intercept ba1 is the intercept of the first-order harmonic amplitude with the bus current, ba3 is the intercept of the third-order harmonic amplitude with the bus current, and ba5 is the intercept of the fifth-order harmonic amplitude with the bus current; bp1 is the first-order harmonic phase calibration value, bp3 is the intercept of the third-order harmonic phase with the motor stator current vector angle, and bp5 is the intercept of the fifth-order harmonic phase with the motor stator current vector angle.

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