Six-axis force sensor using T-shaped legs and single-axis strain gauges

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Solution Overview

Problem

Existing six-axis force sensors are costly and complex, with shear strain gauges requiring large sizes and expensive machining processes, making them difficult to miniaturize and integrate into small robots effectively.

Innovation Solution

A six-axis force sensor design using T-shaped legs with single-axis-type strain gauges attached to cross and vertical beams, allowing for strain detection in multiple axes while simplifying the structure and manufacturing process, and utilizing semiconductor-type strain gauges for enhanced sensitivity and cost-effectiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If shear strain gauges are used to detect shear strain in L-shaped or T-shaped legs, then measurement capability is achieved, but device complexity and manufacturing cost increase due to required concave pockets and complex machining processes

Engineering Contradiction:
Improveshear strain detection capabilityVSAvoidstructure complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces shear strain gauges with strain gauges that detect elongation strain instead. By measuring elongation strain in the legs rather than shear strain, the invention eliminates the need for concave pockets and complex machining processes, thereby reducing device complexity while maintaining measurement capability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from shear strain to elongation strain. This parameter change allows the use of simpler strain gauge configurations without requiring specialized pocket structures, thus simplifying the overall device structure and manufacturing process

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If shear strain gauges are used with concave pockets to improve sensitivity, then sensitivity to shearing force is enhanced, but manufacturing cost and process complexity increase

Engineering Contradiction:
Improvesensitivity to shearing forceVSAvoidmachining process complexity
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent substitutes shear strain measurement with elongation strain measurement, eliminating the need for concave pockets. This substitution maintains sensitivity while dramatically simplifying the machining process, as standard strain gauge mounting surfaces can be used without complex pocket structures

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If six-axis force sensor is designed with traditional leg structure, then force and moment measurement capability is achieved, but device size is large making it difficult to integrate into small robots

Engineering Contradiction:
Improvesix-axis measurement capabilityVSAvoidsensor size
Core Design Contradiction:
Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent changes the measurement approach from shear strain to elongation strain, which enables more efficient use of space in the leg structure. This parameter change allows for a more compact six-axis force sensor design that maintains full measurement capability while reducing overall sensor volume for better integration into small robots

Inventive Principle:
Principle #35Parameter changes

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

The design enables a low-cost, compact six-axis force sensor with improved sensitivity and strength, facilitating easier integration into robotic systems while reducing manufacturing complexity and costs.

Implementation Method 1

detects strains generated in the legs, due to applying a load to one of the pair of members, thereby measuring one or both of a force and a moment acting on one of the pair of members

Methodology Applied
Scientific EffectStrain: Deformation

Data Source

PatentEP1707934B1Six-axis force sensor
Publication Date: 2012.12.12 FANUC LTD
  • EP1707934B1 patent drawingFigure 1~2
  • EP1707934B1 patent drawingFigure 3~4
  • EP1707934B1 patent drawingFigure 5

AI summary

A six-axis force sensor includes a pair of members, and at least three legs scatteringly disposed between the pair of members on the periphery of the members. Each leg includes a T-shaped leg consisting of a cross beam supported at both ends thereof by one of the pair of members and extending on the periphery of the member in a circumferential direction, and a vertical beam extending from the center of the cross beam to a direction perpendicular to the cross beam and connected to the other of the pair of members. The strains on the legs are detected by first single-axis-type strain gauges and second single-axis-type strain gauges. A first single-axis-type strain gauge is attached to a surface of the cross beam facing the side opposite to the vertical beam or a surface of the cross beam facing the vertical beam, so as to be able to detect a strain generated in the cross beam in a longitudinal axis direction thereof, and a second single-axis-type strain gauge is attached to a side surface of the vertical beam facing in a circumferential direction, so as to be able to detect a strain generated in the vertical beam in a longitudinal axis direction thereof.