Motor Voltage Feedforward Control for Torque Ripple Suppression
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Solution Overview
Problem
Existing motor control systems for electric compressors in vehicles face challenges in suppressing torque ripples due to spatial harmonics, particularly at high revolution speeds, leading to instability and delayed responsiveness in current control systems.
Innovation Solution
A motor control device that calculates d-axis and q-axis voltage command values and includes a feed forward command value calculation unit to generate q-axis and d-axis voltage feed forward command values based on spatial harmonic parameters and motor impedance, allowing direct voltage control to compensate for torque ripples caused by spatial harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is performed to reduce torque ripple, then torque ripple suppression is improved, but the control band must be lowered to maintain stability, reducing responsiveness
Solution Approach 1:
The invention calculates and applies voltage feedforward command values based on spatial harmonic parameters before the torque ripple occurs. By preemptively compensating for the torque ripple through feedforward control, the system avoids the need for high-band feedback control, thus maintaining both torque ripple suppression and high control band responsiveness
Solution Approach 2:
The invention changes the control parameter from current-based feedback control to voltage-based feedforward control. By calculating voltage command values that directly compensate for spatial harmonic effects, the system achieves torque ripple suppression without being constrained by the stability limitations of high-band current control
2Productivity
If current control band is raised to improve responsiveness, then followability is improved, but the control becomes unstable due to phase difference between current and voltage
Solution Approach 1:
The invention introduces voltage feedforward command values as an intermediary control mechanism. Instead of directly controlling current with high-band feedback, the system uses calculated voltage commands that account for phase differences and spatial harmonics, mediating the control process to achieve both stability and responsiveness
Solution Approach 2:
The invention replaces the mechanical current control system with a voltage-based control approach. By substituting current feedback control with voltage feedforward control, the system eliminates the phase difference instability issue while maintaining high responsiveness
3Measurement precision
If voltage control is performed in consideration of phase difference, then control accuracy is improved, but the control band must be lowered to prevent instability
Solution Approach 1:
The invention preemptively calculates voltage feedforward command values that incorporate phase difference compensation. By performing the phase compensation in advance through feedforward control, the system achieves accurate voltage control without needing to lower the control band for stability
Data Source
AI summary
There is provided a motor control device which enables torque ripple suppressing control high in followability by executing direct voltage control. A motor control device includes a voltage command calculation unit 15 which calculates a d-axis voltage command value Vdref and a q-axis voltage command value Vqref from a d-axis current command value id* and a q-axis current command value iq* of a motor 6, a feed forward command value calculation unit 23 which calculates a qi-axis voltage feed forward command value Vqff* for generating a q-axis current ripple on the basis of spatial harmonic parameters and the frequency characteristics of a motor winding, and a subtraction unit 10 which subtracts the q-axis voltage feed forward command value Vqff* calculated by the feed forward command value calculation unit 23 from the q-axis voltage command value Vqref calculated by the voltage command calculation unit 15.