Encoder Phase Correction Circuit for Sinusoidal Signal Accuracy
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Solution Overview
Problem
Existing methods for correcting phase errors in sinusoidal signals of two phases in encoders are inefficient due to amplitude variations, time-consuming arithmetic processing, and inaccurate phase correction, especially when phase errors are large, leading to reduced position detection accuracy.
Innovation Solution
A phase correction circuit that includes an analog-to-digital converter, peak detector, offset/amplitude correction section, phase error detector, and phase correction section, which generates correction signals by detecting peak values and computing correction factors to accurately correct phase errors in sinusoidal signals of two phases with a 90-degree phase difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phase error correction is performed using conventional methods (computing sum and difference of signals after eliminating offsets), then phase difference can be set to 90 degrees, but amplitudes of A phase and B phase vary relative to each other and arithmetic processing becomes time-consuming
Solution Approach 1:
The correction process is divided into two independent stages: first eliminating offsets by computing differences of A and B phases, then correcting amplitudes by computing ratios of (A+ B) to (A- B). This segmentation allows each stage to be optimized independently, reducing overall computational complexity while maintaining phase correction accuracy.
Solution Approach 2:
Offset elimination is performed as a preliminary step before amplitude correction. By first computing the difference signals (A-B) and (A+B) to eliminate offsets, the subsequent amplitude correction using ratios becomes more efficient. This preliminary action simplifies the overall computation and reduces processing time.
2Manufacturing precision
If phase error correction is performed using approximate treatment (computing sin δ and cos δ), then correction can be applied, but phase error is not accurately corrected when phase error is large and amplitude fluctuation affects position detection accuracy
Solution Approach 1:
The method transforms the phase correction problem into parameter estimation by computing the ratio K = (A+ B)/(A- B), which directly relates to the phase error through trigonometric relationships. This parameter transformation allows for accurate correction even when phase error is large, avoiding the limitations of approximate treatments while maintaining computational efficiency.
3Manufacturing precision
If B phase is corrected with reference to one phase (A phase), then phase correction can be applied, but shift occurs in phases of interpolation signal and signal between slits and combination defect occurs when phase error is large
Solution Approach 1:
The method uses feedback from both A and B phases to compute correction factors. By computing ratios involving both (A+ B) and (A- B), the system creates a feedback mechanism that adjusts both phases symmetrically, preventing phase shifts in interpolation signals and maintaining reliable combination even when phase error is large.
Data Source
AI summary
A position detector has a peak detector for detecting peak values of an A1 signal and a B1 signal serving as output signals of an analog to digital (AD) converter, an offset/amplitude correction section for generating an A2 signal and a B2 signal by correcting offsets and amplitude errors using the peak values detected by the peak detector, and a position data conversion section for converting the sinusoidal signals of an A phase and a B phase into position data.