Quadrature Decoder Filtering for Noisy Motor Direction Signals
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Solution Overview
Problem
Conventional filtering circuitry struggles to effectively suppress spurious pulses caused by large dust particles and scratches on optical disks in motor speed/rotation sensors, leading to inaccurate direction detection and positioning issues.
Innovation Solution
A quadrature decoder filtering circuitry that uses one quadrature signal to correct errors in the other, employing edge detection and counting mechanisms to differentiate between actual direction changes and noise-induced errors, thereby recovering noisy signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filtering is applied to suppress spurious pulses, then noise is reduced, but valid pulses may be incorrectly filtered causing direction detection errors
Solution Approach 1:
The system employs feedback by continuously monitoring the relationship between quadrature signals A and B. When a pulse is detected in one signal, the system checks the corresponding state of the other signal to verify validity. This feedback mechanism ensures that only genuine pulses are counted while spurious pulses are identified and corrected, preventing direction detection errors.
Solution Approach 2:
The patent changes the parameter of signal validation from simple threshold-based filtering to a relational parameter check between two quadrature signals. By examining whether pulses in signal A correspond with expected transitions in signal B (or vice versa), the system dynamically adjusts pulse acceptance criteria based on the quadrature relationship, thereby maintaining direction detection accuracy while suppressing noise.
Data Source
AI summary
The disclosed quadrature decoder filtering circuitry for motor control uses one quadrature signal to correct an error in the other quadrature signal, thus allowing a noisy signal due to large dust particles or scratches to be recovered. In some implementations, a system processing for quadrature signals comprises a first circuitry triggered by edges of a first quadrature signal to detect inactivity of a second quadrature signal during consecutive edges of the first quadrature signal. A second circuitry is operable to count the number of consecutive edges of the first quadrature signal during inactivity of the second quadrature signal. A third circuitry is operable to combine transitions of the first quadrature signal with the second quadrature signal during a period of time determined by the count value of the second circuitry.