Angle Detection Offset Correction for Rotary Machines

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Solution Overview

Problem

Conventional angle detecting apparatuses struggle to correct 1f angle errors in rotary machines due to frequency components twice the standard wave in sine and cosine signals, and at high speeds, phase shifts occur due to increased error waveform frequencies, leading to inaccurate corrections.

Innovation Solution

An angle detecting apparatus computes offset correction values for sine and cosine signals from the angle signal, using an angle error obtained by removing lower frequency components and extracting higher frequency components to correct the signals, thereby addressing 1f angle errors and reducing phase shift issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional angle detecting apparatus uses midpoint correction values stored in EEPROM or calculated from peak and bottom values, then 1f angle errors can be corrected, but the apparatus cannot correct 1f angle errors resulting from sine and cosine signals containing frequency components that are two times the 1f angle error

Engineering Contradiction:

Improveangle detection accuracyVSAvoidcorrection capability for different error types

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent uses the detected angle signal as feedback to calculate offset correction values. The angle error Δθ is computed from the angle signal, and this error information is fed back to determine the correction values for sine and cosine signals, enabling dynamic correction of 1f angle errors including those from second harmonic components.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the parameter used for correction from static midpoint values stored in EEPROM to dynamic offset correction values calculated from the angle signal. This allows the system to adapt to different operating conditions and correct various types of 1f angle errors effectively.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the angle error estimator calculates error waveform signal at high rotation speeds, then the frequency of error waveform signal increases, but phase shift occurs due to wasteful calculation time, leading to inaccurate correction

Engineering Contradiction:

Improverotary machine speedVSAvoidcorrection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent replaces the conventional angle error estimator that processes alternating quantity error waveform signals with an offset correction value calculator that processes direct quantity signals. This substitution eliminates the phase shift problem caused by calculation time delays at high speeds, as the correction values are derived directly from the angle signal without requiring high-speed alternating quantity processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11047679B2Angle detecting apparatus

Publication Date: 2021.06.29 MITSUBISHI ELECTRIC CORP

AI summary

An angle detecting apparatus is obtained. The angle detecting apparatus is capable of correcting an electrical angle frequency component of an angle signal contained angle signal. An angle detecting apparatus computes an angle signal of a rotary machine from a sine signal and a cosine signal obtained from the angle signal. Offset correction values for the sine signal and the cosine signal are computed from the angle signal. The computed offset correction value for the sine signal is added to the sine signal to correct the sine signal, and the computed offset correction value for the cosine signal is added to the cosine signal to correct the cosine signal.