Steering Angle Sensor Fault Detection via Gear Ratio Monitoring
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Solution Overview
Problem
Existing angle sensors face challenges in reliably detecting angular jumps, especially when no historical values are available, due to non-ideal roundness of output gears causing dynamic changes in transmission ratios and aging effects, leading to measurement inaccuracies and undetectable errors upon sensor reactivation.
Innovation Solution
A method that determines a reference value and comparison value for the angular position of a shaft based on the angular positions of two output gears, monitoring the transmission ratio for long-term changes, and using a lap counter value to correct for angular jumps, with a comparison of these values to detect errors and predict wear, even in the absence of historical data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If period number correction is applied to correct angular jumps, then measurement accuracy is improved, but reliability deteriorates when no historical values are available
Solution Approach 1:
The patent applies preliminary action by determining a reference value for the angular position of the shaft based on the first driven gear before comparing it with a comparison value determined from the second driven gear. This preliminary determination of angular position using multiple gears allows the system to detect faults even when no historical values are available, as the reference and comparison values are both determined from current gear positions rather than requiring past data for validation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a reference value determined from the first driven gear as a mediator between the raw measurements and the final angular position determination. This reference value serves as an independent check against the comparison value from the second driven gear, enabling fault detection without relying on historical data while maintaining measurement accuracy through the gear ratio relationship.
2Measurement precision
If dynamic changes in gear ratio are corrected, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by using the angular position measurements from the two driven gears themselves to detect and correct for dynamic changes in the gear ratio. The system compares the reference value from the first driven gear with the comparison value from the second driven gear, and the gear ratio relationship between them provides the correction mechanism. This eliminates the need for external sensors or complex correction algorithms, as the gears' own measurements serve the correction function.
3Reliability
If redundant calculations are performed to verify measurement accuracy, then reliability is improved, but use of energy increases
Solution Approach 1:
The patent applies partial action by performing only the essential redundant calculation needed for fault detection - comparing the reference value from the first driven gear with the comparison value from the second driven gear. Rather than implementing comprehensive continuous monitoring or multiple layers of validation, the system performs this single critical comparison that provides sufficient fault detection capability while minimizing computational energy consumption. The gear ratio relationship provides the necessary validation without requiring excessive calculations.
Data Source
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AI summary
The invention relates to a method for identifying a fault (96) in an angle sensor (24) which is designed to determine the angular position (18) of a shaft (14) based on an angular position difference (56) between a first output gear (32), which is driven by the shaft (14), and a second output gear (34), which is driven by the shaft (14), the output gears differing in respect of their diameter (34, 36), said method comprising: - determining a reference value (18, 52) for the angular position (18) of the shaft (14) based on the angular position (42) of the first output gear (32), - determining a comparison value (18', 52') for the angular position (18) of the shaft (14) based on the angular position (46) of the second output gear (34) and a transmission ratio (90) between the first output gear (32) and the second output gear (34), and identifying the fault (96) when a comparison (93, 94) of the reference value (18, 52) and the comparison value (18', 52') satisfies a predetermined condition (95).