Electric Power Steering Sensor Comparison for Fast Fault Isolation
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Solution Overview
Problem
In electric power steering devices with a dual-system redundant configuration, identifying a failed sensor is inefficient and time-consuming due to the need for round-robin comparisons, leading to wasted processing capacity and function when only one sensor fails.
Innovation Solution
An electronic control device with a first, second, and third sensor that compares output signals with different threshold values to determine the magnitude relationship and identifies abnormal sensors, allowing for reduced arithmetic processing load and easy failure identification by using output values from normal sensors for drive control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If round-robin comparison method is used to identify failed sensors, then sensor failure identification can be performed, but arithmetic processing load increases and time consumption increases
Solution Approach 1:
The patent divides the sensor comparison process into two distinct stages: a first comparison stage during normal operation that performs lighter arithmetic processing, and a second comparison stage when failure is detected that performs more comprehensive analysis. This segmentation allows the system to maintain low processing load during normal operation while ensuring accurate failure identification when needed.
Solution Approach 2:
The system performs preliminary comparisons during normal operation to establish baseline relationships between sensors. By pre-establishing these comparison results, the system avoids performing full round-robin comparisons at the time of failure detection, thereby reducing time consumption while maintaining identification accuracy.
2Loss of information
If comprehensive sensor comparison is performed to identify failed sensors, then failure location can be identified, but arithmetic processing load increases
Solution Approach 1:
The patent implements a dynamic comparison strategy where the extent of sensor comparison adapts based on system state. During normal operation, only essential comparisons are performed. When failure is detected, the system dynamically increases comparison depth to identify the specific failed sensor, thus balancing information completeness with processing energy consumption.
3Reliability
If dual-system redundant configuration is implemented, then system reliability improves, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple sensors into a unified comparison framework. By combining the output signals of three sensors and applying a systematic comparison method, the system achieves reliable failure identification without requiring complex redundant architectures, thus reducing device complexity while maintaining high reliability.
4Productivity
If normal sensors continue operating after one sensor fails, then processing capacity is utilized, but diagnostic safety decreases
Solution Approach 1:
The system implements continuous feedback through ongoing sensor comparisons. When a failure is detected, the feedback mechanism triggers identification of the specific failed sensor, allowing the system to safely continue operation with remaining normal sensors. This feedback loop maintains diagnostic safety while preserving processing capacity utilization.
Data Source
AI summary
A control device of an electric power steering device includes an arithmetic processing device having a comparison unit, a failure diagnosis unit, and a drive control unit. The comparison unit compares a difference between a first output signal output from a first sensor and a second output signal output from a second sensor with a first threshold value to determine a magnitude relationship, and compares a difference between the first output signal and a third output signal output from a third sensor with a second threshold value to determine a magnitude relationship. Based on a result of the comparison unit, the failure diagnosis unit identifies one abnormal sensor among the first, second and third sensor. Using output values from two normal sensors that are not identified as abnormal sensors among the first, second and third sensor, the drive control unit generates a drive control signal for driving an electric motor.