Magnetic Sensor Disc Mounting for Compact Joint Position Sensing
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Solution Overview
Problem
Existing position sensors for articulated structures, particularly in robotics, face a challenge in balancing accuracy and compactness, as larger magnetic rings provide more accurate position sensing but are not suitable for space-constrained applications like surgical robotics where compactness is crucial.
Innovation Solution
A position sensing arrangement featuring a disc with co-prime magnetic rings and sensor arrays, where the rings are concentric and radially separated by at least the length of a pole pair, allowing for accurate rotation sensing while minimizing interference and size, enabling precise position determination in compact designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If larger magnetic rings are used in the position sensor, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The magnetic ring is divided into multiple independent magnetic pole pairs arranged concentrically. Each pole pair contributes to the measurement precision, allowing the system to achieve high accuracy without requiring a single large magnetic ring. The segmentation of the magnetic field into discrete pole pairs enables compact positioning while maintaining precision.
Solution Approach 2:
Multiple magnetic rings with different numbers of pole pairs are nested concentrically on the same disc. The rings are radially separated but share the same central axis, creating a compact structure where smaller magnetic rings are positioned within the radial space of larger ones. This nesting approach maximizes the use of available space while maintaining compact overall dimensions.
2Measurement precision
If multiple magnetic rings with different pole pair counts are used, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The mounting features are arranged in an asymmetrical pattern on the disc, creating a unique orientation that ensures correct assembly. This asymmetrical design provides built-in alignment guidance, reducing manufacturing complexity by eliminating the need for complex alignment procedures or multiple adjustment steps during assembly.
Solution Approach 2:
Mounting features such as alignment notches and keyed positions are pre-formed on the disc during manufacturing. These preliminary structural features ensure that when multiple magnetic rings are assembled onto the disc, they automatically align to the correct positions and orientations, simplifying the assembly process and reducing the skill level required for manufacturing.
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 solution enhances the accuracy of position sensing while maintaining a compact form factor, suitable for applications like surgical robotics where precise and lightweight sensors are essential.
Implementation Method 1
Hall effect magnetic sensors are commonly used to sense relative motion between links
Data Source
AI summary
A position sensing arrangement for sensing the position of a revolute joint of an articulated structure. The position sensing arrangement comprises a disc and a magnetic sensor assembly. The disc comprises a first magnetic ring with m magnetic pole pairs, and a second magnetic ring with n magnetic pole pairs, where m and n are co-prime, and a mounting arrangement by which the disc is mountable to a magnetisation jig during manufacture and the articulated structure during operation, the mounting arrangement permitting the disc to be mounted to the magnetisation jig and articulated structure in a single orientation only. The magnetic sensor assembly comprises a first magnetic sensor array for detecting the magnetic pole pairs of the first magnetic ring, and a second magnetic sensor array for detecting the magnetic pole pairs of the second magnetic ring.