Force Sensor Design Using Magnetic Displacement Detection

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Solution Overview

Problem

Existing force sensors face challenges in achieving high sensitivity and compactness due to the need for increased length of column portions to accommodate bending moments, which decreases measurement sensitivity and increases sensor thickness, affecting the operable range of robots.

Innovation Solution

A force sensor design that uses a relative displacement detection method between a first member and a second member coupled via elastic structures, with an intermediate member, to measure torque and force, allowing for a shorter distance between detection targets and increasing sensitivity while maintaining compactness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the length of column portions is increased to make them flexible against rotational torque, then the flexibility against rotational torque is improved, but the distance between the first member and the second member is increased, which decreases measurement sensitivity

Engineering Contradiction:

Improveflexibility against rotational torqueVSAvoidmeasurement sensitivity

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The sensor is divided into functional segments: column portions for bending moment support and a strain-generating portion for torque measurement. This segmentation allows each part to be optimized independently - columns can be rigid for bending while the strain-generating portion remains sensitive to torque through elastic deformation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the sensor structure have different rigidity characteristics. The column portions are designed with high rigidity to resist bending moments, while the strain-generating portion is designed with appropriate elasticity to deform under torsional torque. This local differentiation of mechanical properties resolves the contradiction between overall structural rigidity and measurement sensitivity.

Inventive Principle:

Principle #3Local quality

2Strength

If the length of column portions is increased to support bending moment, then the support capability for bending moment is improved, but the sensor thickness is increased, which affects the operable range of robots

Engineering Contradiction:

Improvesupport capability for bending momentVSAvoidsensor thickness

Core Design Contradiction:

StrengthVSLength of stationary object

Solution Approach 1:

The sensor design transitions from a one-dimensional length increase to a two-dimensional area increase. Instead of making columns longer (increasing thickness), the sensor uses a larger surface area with optimized column arrangement and spacing. This allows bending moment support through increased structural footprint rather than increased thickness, maintaining robot operable range.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If the distance between the first member and the second member is increased, then the column portions can be made flexible against rotational torque, but the measurement sensitivity decreases

Engineering Contradiction:

Improveflexibility against rotational torqueVSAvoidmeasurement sensitivity

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent replaces traditional mechanical strain measurement with magnetic field-based displacement detection. Magnetic displacement gauges can accurately measure small displacements over the increased distance between members, enabling both column flexibility for torque accommodation and high measurement sensitivity through non-contact magnetic field sensing rather than mechanical strain gauges.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 achieves high detection precision and compactness by reducing the distance between detection targets, enhancing sensitivity and reducing sensor thickness, thus improving the kinematic performance of robots.

Implementation Method 1

A magnetic displacement gauge is a displacement gauge that utilizes a fact that the strength of magnetic field of a permanent magnet changes in accordance with distance.

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS11220010B2Force sensor, torque sensor, force-sense sensor, fingertip-force sensor, and method of manufacturing the same

Publication Date: 2022.01.11 CANON KK

AI summary

A force sensor includes a first member, a second member, an intermediate member, a first elastic structure that couples the first member and the intermediate member, a second elastic structure that couples the second member and the intermediate member, and a displacement detector that measures displacements of the first member and the second member. It is possible to provide a force sensor that has high detection precision and that is compact.