Rotational Angle Calculation Using Harmonic Correction
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Solution Overview
Problem
Existing methods for detecting the position of a moving object using incremental optical rotary encoders face challenges in achieving high accuracy due to harmonic components in the encoder signals, leading to detection errors and increased memory requirements for correction values, as well as reduced accuracy in calculating detection errors.
Innovation Solution
An information processing apparatus that acquires first and second phase signals from a moving object and calculates a rotational angle using an iterative CORDIC algorithm, incorporating higher harmonics of cosine and sine waves to correct for harmonic distortions in the encoder signals, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correction values are prepared for each detected position to correct detection errors, then detection accuracy is improved, but memory area increases enormously
Solution Approach 1:
The patent transforms the correction approach from storing discrete correction values for each position to using continuous mathematical functions (Fourier series) with adjustable parameters (coefficients). By changing the representation from position-specific values to parameter-based functions, the system achieves accurate correction across all positions without requiring large memory storage.
Solution Approach 2:
Instead of storing actual correction values for each position, the patent creates a mathematical model (Fourier series approximation) that copies the essential pattern of detection errors. This model can generate correction values for any position on demand, eliminating the need to store all possible correction values while maintaining accuracy.
2Ease of operation
If detection error is calculated using detected position including error, then calculation is simplified, but accuracy of detection error calculation is reduced
Solution Approach 1:
The patent implements an iterative feedback mechanism where the detection error calculation uses the previously calculated (imperfect) position, then refines this position by applying correction values derived from the error pattern. The process feeds the corrected position back into the calculation, progressively improving accuracy while maintaining computational simplicity through the use of mathematical approximation.
Data Source
AI summary
An information processing apparatus includes an acquisition unit configured to acquire a first phase signal and a second phase signal that are acquired by measuring a rotation of a moving object, and a calculation unit configured to calculate a rotational angle by an iterative calculation so as to satisfy a relational expression bearing an arctangent. The relational expression bearing the arctangent uses a first cosine wave and a second cosine wave at a higher harmonic of the first cosine wave for the first phase signal, and a first sine wave and a second sine wave at a higher harmonic of the first sine wave for the second phase signal. The first phase signal and the second phase signal may, for example, be analog signals having a wave shape.