Rotation Angle Detection Device Orthogonality Error Correction

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Solution Overview

Problem

The existing rotation angle detection devices face errors due to low orthogonality between sine and cosine signals, leading to rotation angle errors of 2f, which occur when the phase difference between these signals is not 90 degrees and when their amplitudes differ.

Innovation Solution

A rotation angle detection device is designed with an intermediate signal generation unit that produces a signal based on the product of sine and cosine signals, and a multiplication unit that removes high-frequency components, improving orthogonality and reducing errors by adding or subtracting these signals to correct the rotation angle calculation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the phase difference between sine signal and cosine signal is not 90 degrees, then the signals are not orthogonal, but rotation angle errors of 2f occur

Engineering Contradiction:

Improverotation angle detection accuracyVSAvoidsignal orthogonality

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the phase difference between sine and cosine signals to maintain 90-degree orthogonality. The phase adjustment unit modifies the phase of either the sine or cosine signal based on detected orthogonality levels, ensuring the signals remain orthogonal despite variations in the rotating body's operation conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback through an orthogonality detection unit that continuously monitors the orthogonality between sine and cosine signals. This feedback is used by the phase adjustment unit to dynamically correct phase differences, creating a closed-loop control system that maintains signal orthogonality and eliminates rotation angle errors of 2f.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the amplitude of sine signal and cosine signal are different, then amplitude ratio is unbalanced, but rotation angle errors of 2f occur

Engineering Contradiction:

Improverotation angle detection accuracyVSAvoidsignal amplitude balance

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the amplitude ratio between sine and cosine signals. The amplitude adjustment unit modifies the amplitude of either signal based on detected amplitude ratios, ensuring balanced amplitudes that prevent rotation angle errors of 2f caused by unbalanced signal strengths.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback through an amplitude ratio detection unit that continuously monitors the amplitude relationship between sine and cosine signals. This feedback enables the amplitude adjustment unit to dynamically correct amplitude imbalances, creating a closed-loop control system that maintains equal amplitudes and eliminates rotation angle errors.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If center point correction is applied to sine and cosine signals, then signal accuracy is improved, but rotation angle errors of 2f are not suppressed

Engineering Contradiction:

Improvesignal center point accuracyVSAvoidrotation angle error suppression

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies segmentation by separating the signal correction process into distinct functional units: orthogonality detection, phase adjustment, amplitude ratio detection, and amplitude adjustment. This modular approach allows independent optimization of each correction aspect, effectively suppressing rotation angle errors of 2f that center point correction alone cannot address.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediary units (orthogonality detection unit, phase adjustment unit, amplitude ratio detection unit) that mediate between the raw sine and cosine signals and the final rotation angle calculation. These intermediaries detect and correct signal quality issues before they cause rotation angle errors, providing comprehensive error suppression beyond simple center point correction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12258081B2Rotation angle detection device and electric power steering device including same rotation angle detection device

Publication Date: 2025.03.25 MITSUBISHI ELECTRIC CORP

AI summary

Provided is a rotation angle detection device including: an intermediate signal generation unit configured to generate an intermediate signal based on a product of a sine signal and a cosine signal which are based on a rotation angle of a rotating body; a first multiplication unit; and a first rotation angle calculation unit. The intermediate signal generation unit includes: a first multiplier configured to calculate the product of the sine signal and the cosine signal; and a first low-pass filter configured to remove frequency components equal to or higher than twice a frequency of fundamental waves of the sine signal and the cosine signal from an output of the first multiplier.