Synchronous Motor Torque Ripple Compensation via Sine-Wave Correction
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Solution Overview
Problem
Existing synchronous motor control devices for electric vehicles face challenges in reducing torque ripple, which causes vehicle vibrations and deteriorates ride comfort, due to complex calculations and low practicability, especially at intermediate or high speeds.
Innovation Solution
A synchronous motor control device that incorporates a torque ripple compensation unit adding a sine-wave correction current opposite in phase and frequency to the motor drive current, effectively canceling out torque ripple with simple calculations, using formulas such as iq_c = Kcos(6θ + α, where K is a constant, θ is the motor rotation angle, and α is a phase compensation value, and optionally incorporating predictive control and a correction limiter to manage high speeds and calculation delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a vector control theoretical model formula is used to compensate torque ripple, then torque ripple reduction is achieved, but calculation complexity increases and calculation speed decreases
Solution Approach 1:
The patent changes the compensation approach from using complex theoretical model formulas to using a simplified sine wave correction current with specific parameters (frequency six times motor speed, opposite phase). This parameter-based simplification maintains torque ripple reduction effectiveness while dramatically reducing calculation complexity and improving calculation speed.
Solution Approach 2:
The patent replaces the complex, computationally expensive theoretical model with a simple, lightweight sine wave correction method that can be quickly calculated and applied. This 'simpler substitute' approach achieves the same functional goal with minimal computational resources.
2Measurement precision
If complex arithmetic formulas are used for torque ripple compensation at high speeds, then theoretical accuracy is maintained, but calculation cannot follow the running speed and noise is introduced
Solution Approach 1:
The patent transforms the compensation method into a parameter-driven sine wave approach where the frequency is set to six times the motor speed and the phase is set to opposite. This parameterization enables real-time calculation at high speeds while maintaining compensation accuracy, avoiding the noise introduction problem of complex formulas.
3Object-affected harmful factors
If torque ripple compensation is applied, then ride comfort is improved, but calculation time increases
Solution Approach 1:
The patent replaces time-consuming complex calculations with a simple sine wave correction method that requires minimal computation time. This allows torque ripple compensation to be applied in real-time without significant increase in calculation time, thereby improving ride comfort without sacrificing responsiveness.
Data Source
Figure 1A~1B
Figure 2
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AI summary
A synchronous motor control device for an electric vehicle is provided which is able to reduce torque ripple through simple calculation and is excellent in practicability. In a synchronous motor control device (1) which controls a traction synchronous motor (2), torque ripple compensation unit (3) is provided which adds, to a motor drive current, a sine-wave correction current whose phase is opposite to that of torque ripple which is generated in the motor (2) and has a frequency which is six times that of a rotation speed of the motor (2). Specifically, in the case of a configuration including a vector control type basic controller (9), the torque ripple compensation unit (3) outputs a correction current command iq_c, and a value iq_ref obtained by adding the correction current command iq_c to a q-axis current command is used for control.