Torque ripple compensation method based on current harmonic analysis and open-loop torque control

Abstract

The present invention relates to the technical field of permanent magnet synchronous motors, and more specifically to a torque pulsation compensation method based on current harmonic analysis and open-loop torque control. The method comprises the following steps: calculating the a-phase current #imgabs0#, the b-phase current #imgabs1#, and the c-phase current #imgabs2#, calculating the phase current #imgabs3#, substituting the phase current #imgabs4# into a current fundamental wave and torque formula to obtain torque, converting a three-phase stationary coordinate system into a rotating coordinate system to obtain 24th-order torque pulsation, and taking the value of the 24th-order torque pulsation #imgabs5# as #imgabs6#; substituting the 24th-order torque pulsation #imgabs7# into an open-loop torque control compensation formula to obtain a torque harmonic #imgabs8#, obtaining a torque harmonic formula, and using the torque harmonic formula to replace the torque harmonics of the open-loop torque control in an original model, thereby establishing a 24th-order noise compensation model. Compared with the existing technology, the present invention designs a torque pulsation compensation method based on current harmonic analysis and open-loop torque control. By establishing a relationship formula between current harmonics and torque harmonics and building a model, torque pulsation compensation is achieved, thereby reducing the torque pulsation and noise of the electric power steering system.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motors, and in particular to a torque ripple compensation method based on current harmonic analysis and open-loop torque control. Background Art

[0002] The electric power steering system is mainly composed of torque sensors, motors, ECUs, columns, gears and other units. Due to the special structural design of the unit composed of the motor and ECU, torque pulsation will occur, which will cause the end user to experience steering wheel vibration or strong noise when turning the steering wheel.

[0003] Among torque ripples, 24th-order interference is the primary disturbance in electric power steering systems. Currently, the causes of 24th-order noise in electric power steering systems include motor parameters, such as permanent magnet flux harmonics and inductance harmonics, MOSFET parameters in the ECU drive circuit, and EMI interference from the ECU circuit.

[0004] Therefore, it is necessary to design a torque ripple compensation method based on current harmonic analysis and open-loop torque control to reduce the torque ripple and noise of the electric power steering system. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a torque ripple compensation method based on current harmonic analysis and open-loop torque control to reduce torque ripple and noise of an electric power steering system.

[0006] In order to achieve the above object, the present invention is a torque ripple compensation method based on current harmonic analysis and open-loop torque control, comprising the following steps: Step 1, calculate the a-phase current according to the formula , b-phase current , c-phase current , , , ,in, is the rotor position angle, For the rotating coordinate system and Phase angle, a1 is the current fundamental coefficient, a5 is the 5th order harmonic coefficient, a7 is the 7th order harmonic coefficient; Step 2, calculate the phase current according to the formula , ; Step 3, the phase current Substitute into the current fundamental wave and torque formula , and the torque is ,in, is the time derivative of the inductance, is the mechanical angle, is the number of motor pole pairs; Step 4, Convert the three-phase stationary coordinate system into a rotating coordinate system to obtain the 24th order torque pulsation ,in, is the mutual inductance parameter, is the self-inductance parameter, is the main magnetic flux; Step 5, due to Much smaller than , 24th order torque ripple The value is ; Step 6, the 24th order torque pulsation Substituted into the open-loop torque control compensation formula, the torque harmonic is obtained , ,in, is the DC bus voltage, , phase5 is the phase of the 5th order phase current harmonic, phase7 is the phase of the 7th order phase current harmonic, because Much smaller than , ; Step 7, obtain the torque harmonic formula: ; Step 8, use the torque harmonic formula to replace the torque harmonics of the open-loop torque control in the original model and establish a 24th-order noise compensation model.

[0007] The 24th-order noise compensation model is iterated three times.

[0008] Compared with the existing technology, the present invention designs a torque pulsation compensation method based on current harmonic analysis and open-loop torque control. By establishing a relationship formula between current harmonics and torque harmonics and building a model, torque pulsation compensation is achieved, thereby reducing the torque pulsation and noise of the electric power steering system. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 1 is a waveform diagram of phase current with harmonics obtained by simulation in the embodiment.

[0010] Figure 2 FIG. 4 is a diagram showing the results of FFT analysis of phase current with harmonics in an embodiment.

[0011] Figure 3 FIG. 4 is a time domain waveform diagram of the torque before compensation in the embodiment.

[0012] Figure 4 FIG. 4 is a frequency domain waveform diagram of the torque before compensation in the embodiment.

[0013] Figure 5 : is a time domain waveform diagram of the torque after compensation in the embodiment.

[0014] Figure 6 : is a torque frequency domain waveform diagram after compensation in the embodiment. DETAILED DESCRIPTION

[0015] The present invention will now be further described with reference to the accompanying drawings.

[0016] The present invention is a torque ripple compensation method based on current harmonic analysis and open-loop torque control, comprising the following steps:

[0017] Step 1: Calculate the phase a current according to the formula , b-phase current , c-phase current , , , ,in, is the rotor position angle, For the rotating coordinate system and The phase angle of the current is shown in Figure 2, a1 is the current fundamental coefficient, a5 is the 5th order harmonic coefficient, and a7 is the 7th order harmonic coefficient.

[0018] Step 2: The 5th and 7th order interferences in the phase current harmonics are the main sources of the 24th order interferences. Therefore, the phase current is calculated according to the formula , .

[0019] Step 3: Phase current Substitute into the current fundamental wave and torque formula , and the torque is ,in, is the time derivative of the inductance, is the mechanical angle, is the number of motor pole pairs.

[0020] Step 4, Convert the three-phase stationary coordinate system into a rotating coordinate system to obtain the 24th order torque pulsation ,in, is the mutual inductance parameter, is the self-inductance parameter, The main magnetic flux.

[0021] Step 5, due to Much smaller than , 24th order torque ripple The value is .

[0022] Step 6: Set the 24th order torque pulsation Substituted into the open-loop torque control compensation formula, the torque harmonic is obtained , ,in, is the DC bus voltage, , phase5 is the phase of the 5th order phase current harmonic, phase7 is the phase of the 7th order phase current harmonic, because Much smaller than , .

[0023] Step 7, obtain the torque harmonic formula: .

[0024] Step 8: Use the torque harmonic formula to replace the torque harmonics of the open-loop torque control in the original model and establish a 24th-order noise compensation model.

[0025] Generally, the simulink visual simulation tool is used to establish the model. Due to the influence of the closed-loop current controller, if the model is directly built using the formula, the compensation efficiency will be low. Therefore, it is preferred to iterate three times based on the 24th-order noise compensation model to significantly improve the compensation effect.

[0026] Example: In this example, a1=95.24, a5=1.432, a7=1.027, =0.007, =4.

[0027] See also Figure 1 In the simulink visual simulation tool, the simulated phase current with harmonics and the results of FFT analysis of the phase current with harmonics are as follows: Figure 2 See Figure 3 In the simulink visual simulation tool, the time domain waveform of the output torque with harmonics is simulated. Figure 4 , the torque 24th order interference amplitude calculated by FFT, .

[0028] The 5th and 7th order harmonic amplitudes of the phase current obtained from the above analysis are Bring in , so that the formula can be verified, and we can get .and The results are similar, and the formula is verified.

[0029] The time domain and frequency domain waveforms of the torque ripple before 24-order compensation are as follows: Figure 3 and Figure 4 As shown, the present invention is used to build a 24-order noise compensation model, and the compensation results are as follows Figure 5 and Figure 6As shown in the figure, the 24th-order interference amplitude drops to 0.0026 after compensation, which is 85% less than the interference amplitude before compensation: 0.017097.

[0030] The present invention designs a torque ripple compensation method based on current harmonic analysis and open-loop torque control. By establishing a relationship formula between current harmonics and torque harmonics and building a model, torque ripple compensation is achieved, thereby reducing torque ripple and noise in the electric power steering system.

Claims

1. A torque ripple compensation method based on current harmonic analysis and open-loop torque control, characterized by: The following steps are included: Step 1: Calculate the phase a current according to the formula , b-phase current , c-phase current , ， ， ,in, is the rotor position angle, For the rotating coordinate system and Phase angle, a1 is the current fundamental coefficient, a5 is the 5th order harmonic coefficient, a7 is the 7th order harmonic coefficient; Step 2, calculate the phase current according to the formula , ; Step 3, the phase current Substitute into the current fundamental wave and torque formula , and the torque is ,in, is the time derivative of the inductance, is the mechanical angle, is the number of motor pole pairs; Step 4, Convert the three-phase stationary coordinate system into a rotating coordinate system to obtain the 24th order torque pulsation ,in, Mutual inductance parameters, Self-inductance parameters, is the main magnetic flux; Step 5, due to Much smaller than , 24th order torque ripple The value is ; Step 6, the 24th order torque pulsation Substituted into the open-loop torque control compensation formula, the torque harmonic is obtained , ,in, is the DC bus voltage, , phase5 is the phase of the 5th order phase current harmonic, phase7 is the phase of the 7th order phase current harmonic, because Much smaller than , ; Step 7, obtain the torque harmonic formula: ; Step 8, use the torque harmonic formula to replace the torque harmonics of the open-loop torque control in the original model and establish a 24th-order noise compensation model.

2. The torque ripple compensation method based on current harmonic analysis and open-loop torque control according to claim 1, characterized in that: The 24th-order noise compensation model is iterated three times.

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