Rotation position detection device and air conditioner

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Solution Overview

Problem

The existing methods for detecting the rotation position of a motor using line voltage as a reference suffer from accuracy issues due to offsets caused by direct current (DC) voltage and floating capacitance, leading to deviations in detection values and reduced accuracy.

Innovation Solution

A device that detects the matching points of first and second line induced voltages relative to a reference potential, using a detector to identify when these voltages match, and a rotation-position setting unit to set an estimation value for the rotation position at these matching points, thereby enhancing accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If line voltage is used as a reference for rotation position detection, then the detection method is simple, but detection accuracy deteriorates due to offsets caused by DC voltage and floating capacitance

Engineering Contradiction:

Improvedetection method complexityVSAvoidrotation position detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts and compares only the induced voltage components from line voltages by detecting zero-crossing points, separating the useful detection signal from the harmful DC offset and capacitance effects. This extraction approach maintains simplicity while improving accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary comparison mechanism where two line induced voltages are compared against each other rather than against a fixed reference value. This intermediary comparison eliminates the impact of DC offsets and floating capacitance on detection accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If minimum phase is used as reference for line voltage, then the detection approach is simplified, but offset errors increase due to DC voltage influence

Engineering Contradiction:

Improvereference selection complexityVSAvoidline voltage detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Instead of using minimum phase as a fixed reference, the patent inverts the approach by using another line induced voltage as the reference for comparison. This inversion eliminates the systematic offset errors that occur when minimum phase is used as reference.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the reference parameter from minimum phase voltage to another line induced voltage that is dynamically selected. This parameter change allows the system to adapt to different operating conditions and eliminates fixed reference offsets.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If zero-crossing point detection is used, then the rotation position can be determined, but accuracy is reduced due to offset in detection values

Engineering Contradiction:

Improverotation position determinationVSAvoidrotation position detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the comparison between two line induced voltages provides continuous information about rotation position. The zero-crossing detection serves as feedback that confirms the rotation position while the comparative method eliminates offsets.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful effect of DC offsets and floating capacitance into a benefit by using comparative detection. The offsets affect both measurement channels equally, and by comparing them, the common-mode errors are eliminated while the useful rotation position information is preserved.

Inventive Principle:

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

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

This approach allows for accurate detection of the rotation position even with offsets, reducing errors and improving the estimation accuracy of the motor's position.

Implementation Method 1

phase potentials which the armature outputs due to an induced electromotive force

Methodology Applied

Scientific EffectInduced electromotive force: Electromagnetic Induction

Data Source

PatentEP2882093B1Rotation position detection device and air conditioner

Publication Date: 2022.05.25 DAIKIN INDUSTRIES LTD

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AI summary

The present invention is a device for detecting a rotation position that can detect a rotation position with high accuracy even when an offset has occurred. A motor (2) has: a field (22) which includes a permanent magnet, and an armature (21) which includes coils (21u, 21v, and 21w) of three or more phases. The field (22) and the armature (21) rotate relatively. A detector (431) detects whether or not a first line induced voltage (Vun) and a second line induced voltage (Vvn) match each other, the first line induced voltage (Vun) being a potential difference of a first phase potential of phase potentials relative to a reference potential, and the second line induced voltage (Vvn) being a potential difference of a second phase potential of the phase potentials other than the first phase potential relative to the reference potential. The phase potentials is outputted by the armature due to an induced electromotive force. The reference potential is any one of a minimum phase and a maximum phase. A rotation-position setting unit (432) sets, to a predetermined value, an estimation value of a rotation position of the motor 2 at a point in time when the first line induced voltage (Vun) and the second line induced voltage (Vvn) match each other.