Steering ECU Offset Voltage Detection Without PWM Switching Noise
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Solution Overview
Problem
Conventional electric power steering systems face challenges in accurately detecting the offset voltage of current sensors due to interference from motor driving currents and switching noise, which affects the precision of current measurement.
Innovation Solution
The electronic control device includes a control unit that connects the current sensor to either the power supply unit or ground during a detection period, turns off high-side inverter switches, and fixes PWM signals to a constant level, ensuring no motor driving current is generated, thus eliminating interference and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current sensor is connected to the motor during normal operation, then the system can drive the motor, but motor driving current and switching noise interfere with offset voltage detection
Solution Approach 1:
The patent applies preliminary action by performing offset voltage detection during a dedicated detection period before normal motor operation begins. The control unit controls the inverter to connect the current sensor to the power supply unit or ground during this period, enabling offset voltage measurement before motor driving current and switching noise can interfere with the detection.
Solution Approach 2:
The patent extracts the offset voltage detection function from the normal motor operation by creating a separate detection period. During this period, the inverter is controlled to disconnect the motor and connect the current sensor to the power supply unit or ground, isolating the detection process from harmful motor driving current and switching noise interference.
2Measurement precision
If PWM signals are switched during detection, then the inverter can operate dynamically, but switching noise interferes with offset voltage measurement
Solution Approach 1:
The patent extracts the offset voltage detection from the dynamic PWM switching operation by dedicating a specific detection period where PWM signals are fixed. During this period, the control unit fixes PWM signals to a constant level and disables dynamic switching, thereby eliminating switching noise while enabling accurate offset voltage measurement.
Solution Approach 2:
The patent changes the parameter of PWM signal level from dynamic switching to fixed constant level during the detection period. The control unit fixes PWM signals to either turn-on level VH or turn-off level VL during offset voltage detection, preventing switching noise generation while maintaining the ability to restore dynamic operation after detection.
Data Source
AI summary
A vehicle steering assistance device and a driving method thereof are capable of simplifying the configuration of a circuit, reducing manufacturing cost, and reducing the possibility of circuit failure. The vehicle steering assistance device may include: a motor; and a switch unit that connects or disconnects all phase terminals corresponding to a neutral point of the motor based on an external control signal.