Encoder Fault Detection via Command-Position Comparison in Robots

Solution Overview

Problem

Existing methods for detecting encoder abnormalities in motor systems, particularly in general-purpose robots, require additional sensors or modifications to the servo driver, increasing costs and complexity, and are not applicable to systems without pre-existing abnormality detection functions.

Innovation Solution

An abnormality detection method and device that compares command position information from a controller with detection position information calculated from an encoder output, determining encoder abnormalities based on a predetermined threshold, without requiring new configurations or functions in the servo driver, using a safety unit connected to both the controller and encoder.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional sensors or modifications to the servo driver are used to detect encoder abnormalities, then encoder abnormality detection capability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveencoder abnormality detection capabilityVSAvoidsystem configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system uses its own existing command position information and encoder output signals to perform self-diagnosis of encoder abnormalities. The safety unit leverages data already present in the control system without requiring external sensors or modifications, allowing the system to monitor its own health using internally generated and collected information.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

A safety unit is introduced as an intermediary component that receives both command position information from the controller and output signals from the encoder. This intermediary performs the comparison and abnormality determination, isolating the detection function from both the controller and encoder while utilizing their existing outputs without requiring additional sensors or modifications.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If additional sensors or modifications to the servo driver are used to detect encoder abnormalities, then encoder abnormality detection capability is improved, but cost increases

Engineering Contradiction:

Improveencoder abnormality detection capabilityVSAvoidsystem implementation cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The system uses its own existing command position information and encoder output signals to perform self-diagnosis of encoder abnormalities. The safety unit leverages data already present in the control system without requiring external sensors or modifications, allowing the system to monitor its own health using internally generated and collected information.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

A safety unit is introduced as an intermediary component that receives both command position information from the controller and output signals from the encoder. This intermediary performs the comparison and abnormality determination, isolating the detection function from both the controller and encoder while utilizing their existing outputs without requiring additional sensors or modifications.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If encoder abnormality detection is implemented without pre-existing detection functions, then adaptability to general-purpose robots is improved, but device complexity increases

Engineering Contradiction:

Improveapplicability to general-purpose robotsVSAvoiddetection system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The safety unit performs multiple functions: it receives command position information from the controller, receives output signals from the encoder, calculates detection position information, compares the two, and determines encoder abnormalities. This multi-functional approach allows the same component to serve general-purpose robots without requiring pre-existing detection functions, making the system adaptable while managing complexity through functional integration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own existing command position information and encoder output signals to perform self-diagnosis of encoder abnormalities. The safety unit leverages data already present in the control system without requiring external sensors or modifications, allowing the system to monitor its own health using internally generated and collected information.

Inventive Principle:

Principle #25Self-service

Data Source

PatentEP3530423B1Method and device for detecting abnormality of encoder, and robot control system

Publication Date: 2022.04.13 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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AI summary

An abnormality detection method of an encoder includes an output step, a control step, an information acquisition step, and an abnormality determination step. The abnormality determination step compares command position information with detection position information of a motor calculated based on an output signal, and determines that the encoder is abnormal in a case where a difference between the command position information and the detection position information of the motor is equal to or more than a predetermined value.