Feed Motor Lock Detection via Back-EMF Polarity

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Solution Overview

Problem

Conventional lock detection methods in optical disc drive apparatuses, such as mechanical switches and photosensor switches, increase component costs and circuit board size, and are sensitive to mechanical variations and laser light fluctuations, making them inconvenient to implement.

Innovation Solution

A lock detection device that detects back-electromotive voltage in a feed motor to determine its driven or non-driven state, using magnetic polarity change detecting circuits and back-electromotive voltage detecting circuits to check the voltage levels and polarity changes, thereby reducing component costs and circuit board size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical switch or photosensor switch is used to detect feed motor state, then the pickup movement limit position can be detected, but component costs and circuit board size increase

Engineering Contradiction:

Improvepickup movement limit position detectionVSAvoidcomponent costs and circuit board size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical switches and photosensor switches with an electrical detection method using back-electromotive voltage. The feed motor driver detects the motor's driven state by monitoring back-electromotive voltage levels and polarity changes, eliminating the need for separate mechanical or optical detection components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The feed motor itself provides the detection signal through its back-electromotive voltage. The motor's own electrical characteristics during operation are used to determine its driven state, eliminating the need for external detection devices.

Inventive Principle:

Principle #25Self-service

2Reliability

If a mechanical switch is used for lock detection, then the pickup movement limit position can be detected, but mechanical variations among individual pickups must be accommodated

Engineering Contradiction:

Improvepickup movement limit position detectionVSAvoidmechanical variations among individual pickups

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical switch-based detection with electrical back-electromotive voltage detection. This eliminates sensitivity to mechanical variations in pickup assembly because the detection is based on the electrical characteristics of the feed motor itself rather than mechanical contact points.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a photosensor switch is used for lock detection, then the pickup movement limit position can be detected, but variations in laser light and reflected light must be accommodated

Engineering Contradiction:

Improvepickup movement limit position detectionVSAvoidvariations in laser light and reflected light

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces photosensor-based optical detection with electrical back-electromotive voltage detection. This eliminates sensitivity to optical variations such as laser light intensity changes and reflected light variations, as the detection method relies on electrical signals from the motor rather than optical signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If back-electromotive voltage detection is used, then component costs and circuit board size are reduced, but detection accuracy must be maintained despite voltage fluctuations

Engineering Contradiction:

Improvecomponent costs and circuit board sizeVSAvoidfeed motor state detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The feed motor driver continuously monitors back-electromotive voltage and uses this feedback to determine the motor's driven state. The driver compares the detected voltage against expected ranges and uses polarity change detection to confirm state transitions, ensuring accurate detection despite voltage fluctuations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent detects changes in back-electromotive voltage parameters, specifically polarity changes and magnitude variations. By monitoring parameter changes rather than absolute values, the system can accurately detect state transitions even when voltage levels fluctuate during motor operation.

Inventive Principle:

Principle #35Parameter changes

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 solution allows for accurate detection of a feed motor's state without increasing component costs or circuit board size, is less sensitive to mechanical variations, and stabilizes back-electromotive voltage detection, preventing erroneous state detection.

Implementation Method 1

a lock detection device is so configured as to detect a back-electromotive voltage in a feed motor and check whether the feed motor is in a driven state or in a non-driven state based on the level of the back-electromotive voltage

Methodology Applied

Scientific EffectBack-electromotive voltage: Electromagnetic Induction

Data Source

PatentUS7906928B2Feed motor lock detection device

Publication Date: 2011.03.15 ROHM CO LTD

AI summary

A feed motor lock detection device detects a back-electromotive voltage in a feed motor M and checks whether the feed motor M is in a driven state or in a non-driven state based on the level of the back-electromotive voltage.