Robot Joint Sensor Mounting for Accurate Angle Detection

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Solution Overview

Problem

Existing robots face challenges in accurately detecting joint angles due to deformation and angular deviation of rotation sensors, which affect the precision of rotation detection.

Innovation Solution

The robot system incorporates a holding member fixedly attached to the first link to hold and allow the rotator to rotate about the joint axis, reducing decentering and angular deviation of the rotation sensor, thereby improving accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a rotation sensor is directly coupled to the output shaft of the speed reducer through a shaft coupling, then the rotation detection can be implemented, but the accuracy of rotation detection deteriorates due to deformation and angular deviation of the sensor

Engineering Contradiction:

Improverotation detection accuracyVSAvoidsensor stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent divides the sensor support structure into separate components: a holding member fixed to the first link and a support structure on the second link. This segmentation isolates the rotation sensor from the deforming second link, preventing deformation-induced measurement errors while maintaining rotational detection capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a holding member as an intermediary component that is fixed to the first link. This holding member supports the rotation sensor and the rotator, acting as a stable reference frame that eliminates the harmful effect of second link deformation on sensor accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the rotation sensor is mounted on the second link, then the sensor can detect joint rotation, but the sensor experiences decentering and angular deviation affecting measurement accuracy

Engineering Contradiction:

Improvesensor mountingVSAvoidjoint angle detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

Instead of mounting the sensor on the moving second link, the patent inverts the approach by fixing the holding member to the stationary first link. This inversion makes the sensor's reference frame stationary, eliminating decentering and angular deviation caused by second link movement while still enabling joint angle detection through the rotator's rotation

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP4647213A1robot

Publication Date: 2025.11.12 YASKAWA DENKI KK

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AI summary

A robot is effective in improving the accuracy of rotation detection by a rotation sensor that directly detects a joint angle. The robot (2) includes a first link and a second link that are coupled to each other through a joint axis (Ax), a rotator (50) that is fixedly attached to the second link and rotates relative to the first link about the joint axis (Ax), a rotation sensor (40) that is held by a holding member (70) and detects rotation of the rotator (50), and the holding member (70) that is fixedly attached to the first link to hold the rotation sensor (40) and holds and allows the rotator (50) to rotate about the joint axis (Ax).