Motor Phase Disconnection Detection in Power Steering
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Solution Overview
Problem
Conventional methods for detecting disconnection of motor phases in motor-driven power steering (MDPS) are limited, particularly at high speeds and low steering wheel operations, as they rely on current variations and steering wheel speed, making it difficult to distinguish normal conditions from disconnection, and are ineffective during high-speed travel or when the vehicle is stationary.
Innovation Solution
A method and apparatus that calculate Q-axis command currents and compare them with measured currents using error counting, where an increase in error count indicates disconnection, allowing for quick detection of phase disconnection without relying on vehicle speed or steering wheel rotation speed, utilizing a control unit, current sensors, and output units to determine phase disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods use Q-axis command current and current variation ratio to detect disconnection, then detection is possible under normal conditions, but detection becomes impossible during high-speed traveling or when steering wheel is slowly operated
Solution Approach 1:
The patent changes the detection parameter from Q-axis command current (which varies with driving conditions) to phase current (which directly reflects connection status). By monitoring the actual current flowing through each phase and comparing it with expected values, the system can detect disconnection reliably across all driving conditions including high-speed travel and low-speed operations.
2Measurement precision
If current of each phase is sensed and checked, then disconnection can be detected, but it is difficult to distinguish normal situation from disconnection when current has 0 A value at specific motor position
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors phase current and compares it with command current or expected current values. When a discrepancy exceeds a threshold, the system generates an error signal that triggers further detection routines, allowing reliable distinction between normal zero-current positions and actual disconnection events.
Solution Approach 2:
The system performs preliminary current sensing and comparison operations before disconnection occurs or immediately upon detection of abnormal conditions. By continuously monitoring phase currents and maintaining error counts, the system is prepared to detect disconnection at any moment, including when current naturally passes through zero during normal operation.
Data Source
AI summary
A method for detecting a motor error of a motor driven power steering (MDPS) may include: calculating, by a control unit, a Q-axis command current of a motor through a Q-axis command current calculation unit, according to requested torque; calculating a command current of each phase of the motor from the calculated Q-axis command current of the motor; controlling the motor according to the Q-axis command current of the motor, and sensing a measured current of each phase of the motor through each current sensor; determining whether each phase of the motor is disconnected, through the command current and the measured current of each phase of the motor; and outputting the determination result to an output unit.