Phase Current Offset Error Detection in Motor Control
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Solution Overview
Problem
Conventional motor control systems face challenges in accurately measuring phase currents, leading to large torque ripples and opposing motor torque due to offset errors, which can cause system instability and false trips, especially during hard maneuvers or rough road conditions.
Innovation Solution
A method and system that transform motor voltage commands into the stator reference frame to detect offset errors in phase current measurements, allowing differentiation from other system behaviors and enabling accurate detection of faulty current sensors without the need for redundant hardware, thereby improving diagnostic robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current measurement systems are used in torque control mode, then the control system can operate with standard hardware, but offset errors in phase current measurement cause large torque ripple and opposing motor torque
Solution Approach 1:
The patent implements a feedback mechanism where the measured phase currents are transformed to the rotor reference frame and compared with expected values. The system continuously monitors the transformed current signals and uses this feedback to detect offset errors, enabling real-time correction or fault detection to prevent torque ripple and opposing torque conditions
2Reliability
If redundant hardware is added to detect sensor failures, then diagnostic robustness improves, but device complexity and cost increase
Solution Approach 1:
The system performs self-diagnosis by transforming the measured phase currents to the rotor reference frame and analyzing the transformed signals for offset errors. The control system uses its existing computational resources and current measurement signals to detect sensor failures without requiring redundant hardware, enabling the system to serve its own diagnostic needs
Solution Approach 2:
The patent replaces physical redundant sensor hardware with a mathematical transformation approach. By transforming phase currents to the rotor reference frame using coordinate transformation equations, the system substitutes mechanical/hardware redundancy with computational analysis to achieve the same diagnostic functionality
3Productivity
If phase current measurements contain offset errors, then the control system continues to operate, but the actual motor current becomes incorrect resulting in large torque ripple
Solution Approach 1:
The system transforms measured phase currents to the rotor reference frame and continuously compares the transformed signals with expected values. This feedback mechanism enables real-time detection of offset errors in current measurements, allowing the system to identify measurement inaccuracies while maintaining continuous operation and prevent problematic torque conditions
Data Source
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AI summary
A method of controlling a motor of a power steering system is provided. The method generates a direct-axis voltage command and a quadrature-axis voltage command based on a current measurement signal received from the motor. The method transforms the direct-axis voltage command and the quadrature-axis voltage command into an alpha voltage command and a beta voltage command. The method determines an offset error in the phase current measurement based on the alpha and beta voltage commands.