Sinusoidal Encoder Disconnection Detection Using Absolute-Value Comparison

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Solution Overview

Problem

Conventional disconnection detection apparatuses for sinusoidal wave encoders in electric motors often fail to rapidly detect signal disconnections, leading to potential inrush damage during motor operation.

Innovation Solution

A disconnection detection apparatus that includes a first conversion unit to convert sinusoidal waves into absolute values, a determination unit to assess disconnection based on comparison values, and optional amplification and offset elimination units to enhance detection accuracy and speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional waveform conversion and verification methods are used to detect disconnection, then the detection process is simple, but the detection speed is slow and cannot detect disconnection before a full period

Engineering Contradiction:

Improvedisconnection detection speedVSAvoiddetection process complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent transforms the sinusoidal wave parameters by converting to absolute values, changing the detection parameter from waveform verification to amplitude comparison. This allows detection within half a period instead of requiring a full period verification, thereby improving detection speed while maintaining reasonable system complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional waveform conversion mechanism (comparing square waves) with a direct amplitude comparison mechanism using absolute values. This substitution eliminates the need for complete waveform verification and enables faster detection of disconnection conditions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If disconnection detection is delayed until a full period is completed, then false detection is reduced, but motor damage may occur during the delay period

Engineering Contradiction:

Improvedetection accuracyVSAvoidinrush damage to motor

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary disconnection detection by comparing absolute values of sinusoidal waves within half a period, rather than waiting for complete waveform verification. This preliminary action enables early detection of disconnection conditions, allowing the system to take protective measures before motor damage occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by detecting disconnection conditions early and enabling protective shutdown before harmful inrush current can damage the motor. The absolute value comparison method provides early warning that prevents the harmful effect from manifesting

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentEP3239725B1Disconnection detection apparatus of sinusoidal wave signal

Publication Date: 2024.06.05 LSIS CO LTD

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AI summary

Disclosed is a disconnection detection apparatus (20) for a device outputting two sine and cosine output signals having the same frequency and a defined phase shift of 90 degrees. The disconnection detection apparatus (20) of the present disclosure converts the sine and cosine signals into absolute values, respectively, and determines that disconnection occurs when a value of the first sinusoidal wave is less than a first low comparison value that is greater than a minimum value and a value of the second sinusoidal wave is less than a second higher comparison value which is less than the maximum value. Due to the defined phase shift between the signals one of them has to be close to the maximum when the other is close to the minimum, in case of normal operation.