Intermittent Failure Diagnostic System for Electric Power Steering
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Solution Overview
Problem
Conventional electric power steering apparatuses struggle to detect intermittent failures, which do not exceed the failure threshold, leading to false detection and inability to diagnose neighboring failures, thus failing to meet the requirement of recent vehicle electronic control systems.
Innovation Solution
An intermittent failure diagnostic system is developed, which sets an intermittent failure diagnostic threshold within or between the conventional failure thresholds, using statistical methods to securely detect intermittent failures by measuring the number or time of measured values exceeding this threshold, and adjusts the counting value or time to match the false-failure probability of both ordinary and intermittent diagnoses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional failure threshold diagnosis is used, then false detection is reduced, but intermittent failures below the threshold cannot be detected
Solution Approach 1:
The failure threshold is segmented into multiple levels: a conventional failure threshold for definite failure detection and an intermittent failure diagnostic threshold for detecting subtle abnormalities. This segmentation allows the system to detect both obvious failures and intermittent issues without increasing false detection rates.
Solution Approach 2:
The system performs partial diagnosis by focusing specifically on detecting intermittent failures through statistical analysis of measured values against the intermittent threshold, rather than requiring complete failure symptoms to trigger detection. This partial action enables early detection of developing problems.
2Reliability
If the failure threshold is lowered to detect intermittent failures, then detection range is improved, but false detection rate increases
Solution Approach 1:
The system uses feedback mechanisms where measured values are continuously compared against both the intermittent failure diagnostic threshold and the conventional failure threshold. Statistical analysis of the frequency and duration of threshold exceedances provides feedback that distinguishes true intermittent failures from normal variations, maintaining low false detection rates.
Solution Approach 2:
The system changes the parameter of threshold sensitivity by implementing two distinct thresholds: a higher conventional failure threshold for definitive failure detection and a lower intermittent failure diagnostic threshold for early anomaly detection. This parameter differentiation allows detection of subtle changes without triggering false alarms.
3Measurement precision
If statistical methods are applied to detect intermittent failures, then detection accuracy is improved, but system complexity increases
Solution Approach 1:
The system replaces complex mechanical or hardware-based diagnostic mechanisms with statistical analysis methods. By using software-based statistical comparison of measured values against thresholds, the system achieves high detection accuracy without adding physical complexity to the diagnostic apparatus.
Data Source
AI summary
An intermittent failure diagnostic system that, in addition to a failure detection of a conventional failure threshold, appropriately sets an intermittent diagnostic threshold at which a probability of false-positive detection of the intermittent failure is equal to a probability of false-positive detection of the conventional failure, more accurately detects the intermittent failure, suppresses an unprepared system down and improves the reliability, may be used with an electric power steering apparatus.