Slave Shaft Brake Abnormality Detection in Twin-Motor Robots

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Solution Overview

Problem

Existing brake abnormality detection systems for twin-motor-driven robots are unable to accurately detect brake abnormalities in the slave shaft, as these systems rely on position deviation detection, which is not applicable to slave shafts under current control without a position command.

Innovation Solution

A brake abnormality detection system and method that involves giving a fine operation command to the master shaft while releasing the excitation brakes of both the master and slave shafts, allowing the slave shaft to be finely operated and its operation amount detected and compared to a reference value to diagnose brake abnormalities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If position deviation detection is used for brake abnormality detection, then brake abnormalities in master shaft can be detected, but slave shaft brake abnormalities cannot be detected because slave shaft is under current control without position command

Engineering Contradiction:

Improvebrake abnormality detection accuracyVSAvoidapplicability to slave shaft

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent uses the master shaft as an intermediary to indirectly control and detect the slave shaft's brake status. By commanding the master shaft to move and observing the slave shaft's response through current measurements, the system can detect brake abnormalities in the slave shaft without needing direct position control, thus resolving the contradiction between detection accuracy and adaptability to slave shaft

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical position deviation detection method with an electrical current measurement method. Instead of measuring position deviation which requires position commands, the system measures the current consumed by the slave shaft motor during master shaft movement to infer brake status, enabling slave shaft brake abnormality detection without position control infrastructure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If current is flowed to both motors simultaneously for control, then twin-motor coordination is achieved, but brake abnormality diagnosis of individual motors becomes difficult

Engineering Contradiction:

Improvetwin-motor control coordinationVSAvoidbrake abnormality diagnosis difficulty

Core Design Contradiction:

Ease of operationVSDifficulty of detecting and measuring

Solution Approach 1:

The patent segments the control and detection process into distinct phases: during normal operation both motors receive current for coordinated control, but during brake abnormality detection only the master shaft is commanded to move while the slave shaft's current consumption is monitored separately. This temporal segmentation allows both coordinated control and individual brake diagnosis to function properly

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by commanding only the master shaft to move during brake detection mode, rather than controlling both motors simultaneously. This partial activation of the master shaft creates a test condition where the slave shaft's brake status can be diagnosed through its current consumption pattern without requiring full twin-motor coordinated operation

Inventive Principle:

Principle #16Partial or excessive action

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 enables accurate detection of brake abnormalities in the slave shaft, preventing motor lock issues and secondary failures that could lead to robot stops, thereby ensuring continuous operation.

Implementation Method 1

a brake is used to maintain the posture of a robot when a motor is stopped

Methodology Applied

Scientific EffectElectromagnetic excitation: Electromagnet

Implementation Method 2

when accretion (for example, grease) adheres to a friction plate of the brake, a braking torque required by the brake drastically declines

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

a braking torque required by the brake drastically declines, and when the excitation of the motor is stopped, the posture of a robot such as a robot arm, for example, can become unable to be maintained

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12337486B2Abnormality detection method in twin-motor-driven robot

Publication Date: 2025.06.24 NACHI FUJIKOSHI CORP

AI summary

An operation controller configured to give a fine operation command to a master shaft in a state in which servomotors are excited and respective excitation brakes of the master shaft and the slave shaft are released, and an abnormality detector configured to perform detection of an abnormality of the excitation brake of the slave shaft by detecting an operation amount of the slave shaft that is obtained when the slave shaft is finely operated in accordance with the fine operation command to the master shaft in a controlled manner, and comparing the operation amount with a reference value are included.