Encoder Signal Correction Using Lissajous Polar Residuals
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Solution Overview
Problem
Existing methods for correcting errors in 2-phase sinusoidal signals, such as offset, amplitude ratio, and phase difference errors, are inefficient and require high sampling rates or precise timing, which is challenging for low-power encoders and encoders with low sampling rates.
Innovation Solution
A method and apparatus that calculate correction values for 2-phase sinusoidal signals using polar coordinate calculations and least-squares methods to determine correction residuals for offset, amplitude ratio, and phase difference errors, allowing for efficient and accurate correction without high sampling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier analysis is performed using data with constant pitch to detect third harmonic components, then measurement precision of errors is improved, but productivity decreases due to time-consuming sampling of all segments
Solution Approach 1:
The patent extracts only the essential information needed for error detection by using a simplified calculation method that focuses on specific characteristic points of the Lissajous waveform, rather than performing comprehensive Fourier analysis on all segments. This allows rapid calculation of correction coefficients while maintaining sufficient measurement precision.
Solution Approach 2:
Instead of performing complete Fourier analysis on all segments, the patent applies a partial action approach by calculating correction coefficients using a simplified method that processes data more efficiently, achieving adequate error detection without the full computational burden of traditional Fourier analysis.
2Use of energy by moving object
If sampling rate is suppressed to reduce power consumption, then use of energy is improved, but measurement precision deteriorates because desired points cannot be sampled
Solution Approach 1:
The patent changes the calculation parameters by using a simplified method that does not require high sampling rates to capture specific waveform points. The correction coefficients are calculated using a different mathematical approach that works effectively with lower sampling rates, thus maintaining measurement precision while reducing power consumption.
Solution Approach 2:
The system uses the available sampled data itself to perform correction calculations without requiring additional high-rate sampling. The correction value calculation apparatus processes the existing low-rate sampled data through its simplified algorithm, making the system self-sufficient with the given sampling conditions.
3Ease of operation
If 2-phase sinusoidal signals are approximated separately by least-squares method, then ease of operation is improved, but measurement precision of amplitude ratio error deteriorates
Solution Approach 1:
The patent merges the approximation processes for the two-phase signals by calculating correction coefficients that simultaneously account for both signals and their interrelationships. This combined approach maintains calculation simplicity while improving the precision of amplitude ratio error detection by considering the signals together rather than separately.
Data Source
AI summary
A correction value calculation method calculates correction values to correct the 2-phase sinusoidal signals (X, Y) output by the encoder, and includes: a polar coordinate calculation step for calculating, for N phase angles and the Lissajous radius corresponding to each phase angle in the Lissajous waveform drawn by the 2-phase sinusoidal signals, a squared radius, which is the square of the Lissajous radius corresponding to each phase angle; and a correction value calculation step for calculating, based on each phase angle and corresponding squared radius, at least a correction residual of an offset error of the signal X, a correction residual of an offset error of the signal Y, a correction residual of an amplitude ratio error of the signals X and Y, and a correction residual of a phase difference error between the signal X and the signal Y, and then calculating correction values based on the correction residuals.