Encoder SIN COS Signal Correction via Lissajous Radius Feedback
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Solution Overview
Problem
Existing encoder systems face interpolation errors due to offsets, amplitude differences, and phase differences in SIN and COS waveforms, which are exacerbated by noise and waveform distortions, leading to inaccuracies in position detection.
Innovation Solution
An automatic correction method that detects offsets and differences in SIN and COS signals by extracting components from the radius variation waveform of a Lissajous waveform, feeding back these corrections to maintain a constant waveform radius, and reducing interpolation errors by stabilizing amplitude and phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the average of positive and negative peak values of COS waveform is used to detect offset, then the detection method is simple, but noise with vertically asymmetric waveform causes error in detected offset value
Solution Approach 1:
The patent applies feedback by continuously monitoring the Lissajous waveform characteristics and adjusting the offset correction values based on the actual waveform deviations. The correction values are fed back to the signal processing system to dynamically compensate for noise-induced errors in offset detection.
Solution Approach 2:
The patent replaces the simple mechanical averaging method with a more sophisticated signal processing approach using Lissajous waveform analysis. By substituting the peak-value averaging method with radius variation analysis of the Lissajous waveform, the system achieves higher precision while maintaining computational efficiency.
2Device complexity
If traditional interpolation methods are used, then the system is simple, but interpolation errors occur due to offset, amplitude difference, and phase difference in SIN and COS waveforms
Solution Approach 1:
The patent applies preliminary action by performing offset detection and correction before the interpolation calculation. By pre-correcting the SIN and COS waveforms for offset, amplitude difference, and phase difference, the system eliminates errors that would otherwise propagate through the interpolation process, thereby improving position data accuracy without complicating the interpolation itself.
Solution Approach 2:
The system uses feedback from Lissajous waveform analysis to continuously monitor and correct waveform parameters. The radius variation information is fed back to adjust the SIN and COS signals, ensuring accurate interpolation results while maintaining system simplicity.
3Reliability
If noise is present in SIN and COS waveforms, then signal processing becomes more complex, but noise causes waveform distortion and interpolation errors
Solution Approach 1:
The patent replaces direct peak-value detection with Lissajous waveform radius variation analysis. This substitution provides inherent noise resistance because the radius variation method averages out noise effects over the waveform cycle, achieving robust signal processing without adding significant complexity.
Solution Approach 2:
The system uses feedback from continuous Lissajous waveform monitoring to detect and correct noise-induced distortions. By analyzing radius variations and feeding back correction signals, the system maintains signal integrity even in noisy environments, improving reliability without requiring overly complex processing.
Data Source
AI summary
An automatic correction method, for an encoder system for reading periodic signals on a scale as “SIN” and “COS” signals and converting the periodic signals into position signals, includes performing feedback to the “SIN” or “COS” signal to reduce an interpolation error after the conversion.