Electric Power Steering Torque Sensor Verification
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Solution Overview
Problem
The existing electric power steering systems lack reliability in calculating the final absolute steering angle due to the lack of verification of relative steering angles received from angle elements, which is a concern especially with the introduction of the ISO 26263 Standard requiring high reliability.
Innovation Solution
An electric power steering system that includes a torque sensor with first and second rotors, first and second angle elements for measuring absolute and relative steering angles, and an electronic control unit that determines a reference steering angle, traces and accumulates absolute steering angles based on relative angles, averages them when within a reference difference, and outputs an alarm upon excessive discrepancies, ensuring a reliable final absolute steering angle calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electronic control unit calculates the final absolute steering angle without verifying relative steering angles from multiple angle elements, then the calculation process is simple and fast, but the reliability of the calculated final absolute steering angle is low
Solution Approach 1:
The system performs preliminary verification of relative steering angles before final calculation by tracing absolute steering angles from multiple angle elements and checking for consistency. This preliminary check ensures data reliability before the final averaging step, preventing erroneous calculations from compromising system reliability.
Solution Approach 2:
The electronic control unit implements a feedback mechanism where it continuously monitors the difference between traced absolute steering angles from different angle elements. When the difference exceeds a reference threshold, the system detects potential malfunctions and can trigger alarm information, creating a closed-loop verification system that enhances reliability.
2Reliability
If the system traces and compares absolute steering angles from multiple angle elements with verification, then the reliability of the final absolute steering angle is improved, but the calculation time and processing complexity increase
Solution Approach 1:
The system performs verification only to the extent necessary for safety - checking whether the difference between traced angles exceeds a reference difference. This partial verification approach (checking only for excessive deviations rather than exhaustive analysis) maintains reliability while minimizing unnecessary processing time for normal operating conditions.
3Stability of the object's composition
If the system maintains accumulated steering angles when difference exceeds reference difference, then the system stability is improved, but the responsiveness to actual steering changes may be reduced
Solution Approach 1:
The system applies preliminary anti-action by maintaining previously accumulated steering angle data when new measurements show excessive deviation. This prevents erroneous data from destabilizing the system while the alarm mechanism alerts operators to the underlying issue, balancing stability with eventual responsiveness when the condition is resolved.
Data Source
AI summary
An electric power steering system includes: a torque sensor including a first rotor connected to an input shaft, a second rotor connected to an output shaft, a first angle element for measuring an absolute steering angle of the first rotor, and second and third angle elements for measuring relative steering angles of the first rotor; and an electronic control unit for determining a reference steering angle based on the absolute steering angle and the relative steering angles received from the torque sensor, tracing and accumulating first and second absolute steering angles rotated from the reference steering angle based on the relative steering angles received from the second and third angle elements, and averaging the first and second absolute steering angles to provide the calculated final absolute steering angle when the difference between the accumulated first and second steering angles is within the preset reference difference.