Angular Resolver Imbalance Detection Circuit
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Solution Overview
Problem
Angular resolvers in noisy environments, such as gasoline-engine compartments, face challenges in accurately determining motor shaft position and speed due to electromagnetic interference (EMI) degrading the quality and resolution of electrical signals, limiting the control precision of physical devices like motors and robots.
Innovation Solution
A circuit and method for detecting angular resolver imbalance by comparing the root mean square (RMS) values of sine and cosine output signals from a resolver sensor, using different time windows to integrate and average the signals, and generating a fault signal when imbalances exceed a threshold, effectively decoupling the exciter reference signal and compensating for noise and amplitude imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are used in electrically noisy environments (such as gasoline-engine compartments), then positioning information can be obtained, but electromagnetic interference degrades the quality and resolution of electrical signals
Solution Approach 1:
The patent converts the harmful effect of electromagnetic interference into a useful diagnostic tool by monitoring signal imbalance. The EMI causes asymmetric degradation of sine and cosine signals, which the system detects through imbalance detection. This allows the system to identify when signals are being corrupted and take appropriate corrective actions, such as requesting re-sampling or switching to alternative sensing methods.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors the quality of resolver signals and adjusts its operation accordingly. When signal imbalance exceeds thresholds, the system generates feedback to request re-sampling of the resolver or switch to alternative control strategies, creating a closed-loop system that adapts to noisy environments.
2Reliability
If conventional fault detection methods are used (sum of squares filtering), then fault detection is possible, but the method does not effectively decouple the exciter reference signal from noise and imbalances
Solution Approach 1:
The patent extracts the exciter reference signal component from the resolver output signals through synchronous detection. By multiplying the sine and cosine signals with reference signals at the exciter frequency and low-pass filtering the results, the system separates the useful position information from the excitation carrier and noise components, achieving effective decoupling.
Solution Approach 2:
The patent introduces intermediary processing steps including synchronous detectors and low-pass filters that act as mediators between the raw resolver signals and the final position calculation. These intermediaries selectively pass the desired signal components while blocking noise and interference, improving both reliability and measurement precision.
Data Source
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AI summary
In described examples, an angular resolver system includes an imbalance detector (1600) for detecting degraded resolver output signals. The imbalance detector (1600) includes first (1602) and second (1604) power averaging circuits and a comparator circuit (1662, 1664, 1670). The first power averaging circuit (1602) includes a first integrator (1646) for generating over a first time window a first average power signal (Vcl) in response to resolver sensor output signals. The second power averaging circuit (1604) includes a second integrator (1648) for generating over a second time window a second average power signal (Vc2) in response to the resolver sensor output signals, where the first time window is longer than the second time window. The comparator circuit (1662, 1664, 1670) compares the first average power signal and the second average power signal and generates a fault signal (1670) when the first average power signal and the second average power signal differ by a selected voltage threshold (1654, 1658).