Current Sensor Failure Detection in Electric Power Steering
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Solution Overview
Problem
Existing current sensor failure detection methods for electric power steering systems are limited in coverage and accuracy, particularly when the d-axis current of the motor rotor is zero, and involve complex error calculation processes, which can lead to inaccurate detection of phase current errors across different motor positions.
Innovation Solution
A method and apparatus that calculate the phase and magnitude of the current required for the motor based on torque requirements, using a required current calculator and estimated current calculator, and compare this with measured current values to detect sensor failures without additional hardware, employing a failure detector to identify discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing current sensor failure detection methods are used, then detection can be performed in some operating conditions, but detection accuracy deteriorates when d-axis current is zero and coverage is limited
Solution Approach 1:
The patent changes the detection parameter from direct phase current measurement to estimated current based on torque and position. By calculating required current from torque requirements and estimating actual current from motor position, the system achieves accurate failure detection across all operating conditions including when d-axis current is zero, thereby improving both reliability and measurement precision
Solution Approach 2:
The patent introduces torque and position information as intermediary parameters to detect current sensor failures. Instead of directly measuring phase currents, the system uses torque requirements and motor position to calculate estimated current, which serves as an intermediary indicator to detect sensor failures without being affected by the limitations of direct current measurement methods
2Reliability
If complex error calculation processes are used, then detection coverage can be expanded, but calculation complexity increases and accuracy deteriorates
Solution Approach 1:
The patent extracts the essential detection function by taking out only the necessary parameters (torque and position) needed for current estimation. This eliminates the need for complex error calculation processes while maintaining full detection coverage, as the system only requires calculating required current from torque and estimating actual current from position information
Solution Approach 2:
The patent segments the detection process into two independent calculation steps: calculating required current from torque requirements, and estimating actual current from motor position. This segmentation simplifies the overall calculation process by breaking down the complex error calculation into manageable, independent components that can be easily implemented and verified
Data Source
AI summary
A method and apparatus for detecting a failure of a current sensor measuring the magnitude of a current, by which a motor is driven. A required current calculator calculates a phase and a magnitude of a current required for a motor, in accordance with a torque required for the motor. An estimated current calculator calculates an estimated current, in accordance with the phase and the magnitude of the required current. A failure detector detects a failure of a current sensor by comparing the estimated current with a current measured by the current sensor.