Resolver Malfunction Detection Using Segmented Fault Regions
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Solution Overview
Problem
Existing malfunction detection devices for resolvers struggle to accurately detect malfunctions as the value of sin^2 θ + cos^2 θ can vary within and outside normal ranges due to rotation angle and noise, leading to false negatives and false positives.
Innovation Solution
A malfunction detection device that includes a test value calculation unit, a malfunction detection unit, a count unit, and a reset unit to determine malfunctions based on threshold values and count values, preventing false determinations by incrementing the count only when malfunctions persist and resetting during normal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the value of sin^2 θ + cos^2 θ is used for malfunction detection, then the detection method is simple, but the detection accuracy deteriorates because the value varies between inside and outside normal range according to rotation angle
Solution Approach 1:
The detection range is segmented into a fault determination region and a non-fault determination region based on rotation angle. The malfunction detection unit selectively performs detection only in the fault determination region where malfunction indicators are reliable, avoiding the non-fault region where false positives occur due to normal signal variations.
Solution Approach 2:
The system pre-determines and stores the fault determination region (where |sin θ| ≥ √0.5 or |cos θ| ≥ √0.5) before actual malfunction detection. This preliminary classification of detection regions allows the system to apply detection logic only when conditions are favorable, preventing false detections during normal operation in non-fault regions.
2Speed
If malfunction detection is performed continuously, then responsiveness to actual malfunctions is improved, but false detections increase due to temporary noise influences
Solution Approach 1:
The malfunction detection unit applies different detection qualities to different signal conditions. In the fault determination region, full detection sensitivity is applied. In the non-fault determination region, detection is suppressed or modified to avoid false positives, even though this reduces responsiveness slightly, overall reliability improves.
Solution Approach 2:
The rotation angle θ serves as an intermediary parameter that mediates between the sine and cosine signals. By evaluating the rotation angle first, the system determines whether the current signal state is suitable for reliable malfunction detection, acting as a gatekeeper that prevents false detections during normal signal variations.
3Measurement precision
If the fault determination region is restricted to improve detection accuracy, then false positives are reduced, but the detection coverage area decreases
Solution Approach 1:
The system exploits the periodic nature of sinusoidal signals. Although detection is restricted to specific regions within each cycle (where |sin θ| ≥ √0.5 or |cos θ| ≥ √0.5), the periodic repetition of these favorable regions ensures that malfunctions will be detected multiple times per rotation, maintaining effective coverage despite localized detection zones.
Data Source
AI summary
A malfunction detection device for a resolver detects malfunction in a resolver with accuracy and stability even if a value of a square sum is varied between inside and outside of a normal range. When the resolver is in malfunction, a sine signal and a cosine signal are read. It is determined whether a malfunction determination of the resolver is prohibited, or not, from read values of the sine signal and the cosine signal, or square values thereof. When it is determined that the malfunction determination of the resolver is prohibited, the count value is accumulated and incremented every time the test value falls outside a normal range. When the count value arrives at a given value or higher, it is determined that the resolver is in malfunction.