Robot Joint Encoder Layout for Reducer Wobble Accuracy
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Solution Overview
Problem
Deflection or wobble in the internal mechanism of a robot's reducer due to insufficient rigidity, which affects the accuracy and positioning of the robot's joints.
Innovation Solution
Incorporating a robot design with rotatable link members, a motor, a reducer, and both input-side and output-side encoders, where the output-side encoder includes a plate-like scale member and sensor to detect the relative rotation angle between link members, and a guide tube to secure the scale member and sensor, allowing for accurate detection and reduced interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output-side encoder is positioned between the two links adjacent in the rotation axis direction, then the detection accuracy of relative rotation angle is improved, but the scale member and sensor are difficult to access for maintenance and replacement
Solution Approach 1:
The encoder is repositioned from the radial direction (between links) to the axial direction (opposite sides of the second link member). This dimensional change allows the scale member and sensor to be accessed from the axial side, making them easily reachable for maintenance while maintaining detection accuracy through the guide tube structure.
Solution Approach 2:
A guide tube is introduced as an intermediary component to hold the scale member and sensor. This guide tube structure enables the encoder components to be positioned at the optimal detection location while providing a convenient access path for installation, maintenance, and replacement operations.
2Measurement precision
If the scale member is fixed to the second link member and the sensor is fixed to the first link member, then the relative rotation angle can be detected, but the encoder components are difficult to access for maintenance
Solution Approach 1:
The mounting positions of both the scale member and sensor are changed from radial mounting (between links) to axial mounting (opposite sides of the second link member). This dimensional repositioning maintains the functional relationship for detecting relative rotation angle while making both components accessible from the axial side for easy maintenance operations.
Solution Approach 2:
The guide tube serves as a mediator that holds both the scale member and sensor in position while providing a convenient access structure. This intermediary structure enables maintenance personnel to easily reach and service the encoder components without disassembling the entire robot mechanism.
3Measurement precision
If the encoder components are positioned close to the reducer internal mechanism, then the detection accuracy is improved, but the components are vulnerable to interference and difficult to maintain
Solution Approach 1:
The guide tube acts as a protective intermediary structure that houses the scale member and sensor. This structure shields the encoder components from mechanical interference and environmental factors while maintaining their close proximity to the reducer for accurate detection. The guide tube also provides a clear access path for maintenance.
Solution Approach 2:
By repositioning the encoder components to the axial side of the second link member, the design separates the detection function (maintained through guide tube positioning) from the vulnerability to interference and maintenance difficulty. This dimensional repositioning reduces exposure to harmful factors while preserving detection accuracy.
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
Improves the accuracy and positioning of the robot's joints by detecting relative rotation angles and reducing deflection or wobble, while also facilitating easy access and maintenance of the encoders.
Implementation Method 1
an output-side encoder that detects a relative rotation angle between the first link member and the second link member, wherein the output-side encoder includes a plate-like scale member that has an angle-detection pattern and a sensor that detects the pattern on the scale member
Data Source
AI summary
A robot including at least one joint shaft that includes: a first link member and a second link member that are coupled about a rotation axis; a reducer that has an input shaft part fixed to the first link member and an output shaft part fixed to the second link member; a motor that generates a driving force to be input to the reducer; and an input-side encoder that detects a rotation angle of a rotation shaft of the motor; and an output-side encoder that detects a rotation angle between the first link member and the second link member. The output-side encoder includes a scale member that has a pattern and a sensor that detects the pattern on the scale member. The scale member is fixed to an attachment surface, and the sensor is attached to a fixing member fixed to the first link member.