Rotation Angle Detection Using Asymmetric Driven Gears
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Solution Overview
Problem
Existing rotation angle detection systems in electric power steering (EPS) apparatuses rely on multiple sensors of the same type, which may not effectively detect abnormalities in steering angle sensors due to product specifications or other factors, leading to potential inaccuracies in detecting abnormal rotation angles.
Innovation Solution
A rotation angle detection apparatus comprising a driving gear, two driven gears with different numbers of teeth, and two sensors, along with an arithmetic circuit that computes the rotation angle of the driving gear based on the detected rotation angles of the driven gears, allowing for abnormality detection by comparing the relationship between the driven gears' angles to the computed driving gear angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sensors of the same type are used to detect rotation angle, then the reliability of sensor operation is improved, but the ability to effectively detect abnormalities in steering angle sensors deteriorates due to product specifications and other factors
Solution Approach 1:
The patent applies asymmetry by using two driven gears with different numbers of teeth (first driven gear with teeth number z1, second driven gear with teeth number z2 where z1≠z2). This asymmetric configuration creates different rotational relationships between the driven gears and the driving gear, enabling the system to detect abnormalities that would be indistinguishable when using identical sensors. The different tooth counts generate distinct rotational angle patterns that can be compared to identify sensor failures.
2Measurement precision
If the relationship between driven gears' angles is compared to computed driving gear angle for abnormality detection, then abnormality detection accuracy is improved, but false detection is reduced by establishing allowable ranges
Solution Approach 1:
The patent implements beforehand cushioning by pre-establishing allowable ranges for the rotational angle relationships between the driven gears and the driving gear. These ranges account for normal variations and tolerances in the system. By comparing actual measurements against these pre-defined ranges, the system can distinguish between normal operational variations and actual abnormalities, preventing false detections while maintaining high detection accuracy.
Data Source
AI summary
A rotation angle detection apparatus includes a driving gear, two driven gears, two sensors, and an arithmetic circuit. The two driven gears have different numbers of teeth and each are in mesh with the driving gear. The arithmetic circuit is configured to compute a rotation angle of the driving gear based on the rotation angles of the two driven gears, detected through the two sensors. The arithmetic circuit is configured to, when a relationship between the rotation angles of the two driven gears, detected through the two sensors, is different from the relationship when the rotation angle of the driving gear, computed by the arithmetic circuit, is normal, detect an abnormality in the rotation angle of the driving gear, computed by the arithmetic circuit.