R/D Converter Noise Reduction via Band Elimination Filter

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Solution Overview

Problem

Existing R/D converters are unable to effectively eliminate normal mode noise caused by a magnetic field produced by a motor, leading to output angle errors in digital angle signals.

Innovation Solution

An R/D converter configuration that includes a band elimination filter between the synchronous detection circuit and the controller, which reduces noise components by filtering out frequencies near the excitation signal frequency, thereby minimizing the impact of magnetic field-induced noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the resolver is disposed close to the motor for compact design, then space is saved, but the resolver is strongly affected by magnetic field produced by motor causing noise

Engineering Contradiction:

ImprovespaceVSAvoidmagnetic field noise

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful magnetic field noise into a manageable signal characteristic by identifying its specific frequency properties (excitation signal frequency ± rotational frequency). The band elimination filter then uses these frequency characteristics to selectively remove the noise, effectively converting the harmful proximity effect into a frequency-based filtering opportunity

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Measurement precision

If band elimination filter is added to remove normal mode noise, then output angle error is reduced, but device complexity increases

Engineering Contradiction:

Improveangle detection accuracyVSAvoidfilter circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by making the band elimination filter frequency-selective rather than broadband. The filter is designed to eliminate only the specific frequency range where normal mode noise occurs (excitation signal frequency ± rotational frequency), leaving other frequency components unaffected. This localized filtering approach minimizes impact on signal quality while effectively removing noise

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution significantly reduces output angle errors by eliminating or reducing normal mode noise, improving the accuracy of angle detection in the presence of motor-generated magnetic fields.

Implementation Method 1

a band elimination filter which eliminates or reduces the noise component superposed on the resolver signal by referring to the frequency of the excitation signal

Methodology Applied

Scientific EffectBand elimination filtering: Filter (electronic)

Implementation Method 2

the noise component in the signal output from a synchronous detector has a peak in the vicinity of the frequency of the excitation signal

Methodology Applied

Scientific EffectSynchronous detection: Homodyne Detection

Data Source

PatentEP2073390B1R/D converter and angle detecting apparatus

Publication Date: 2011.05.18 JAPAN AVIATION ELECTRONICS IND LTD

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AI summary

A band elimination filter 35 that eliminates or reduces a low frequency noise superposed on resolver signals S 1 and S2 is provided between a synchronous detection circuit 34 that performs synchronous detection by referring to an excitation signal and a controller 36 that controls a digital angle output ϕ to make a deviation (sin (θ - ϕ)), which is the output of the synchronous detection circuit, zero.