Optical 6-Axis Force Torque Sensor for Compliant Robot Fingers

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Solution Overview

Problem

Existing force and torque sensors for robotic manipulation are limited by high cost, lack of compliance, difficulty in integration, and sensitivity to external environments, making them prone to damage and difficult to package.

Innovation Solution

A 6-axis force/torque sensor using LEDs as both light emitters and receivers, integrated with a flexible structure, allows for high sensitivity and easy integration into robot fingers, providing robust overload protection and low-cost manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an off-the-shelf six-axis force and torque sensor is incorporated into a robotic finger base, then force and torque measurement capability is achieved, but the system becomes stiff, expensive, and difficult to integrate

Engineering Contradiction:

Improveforce and torque measurement capabilityVSAvoidintegration difficulty and cost

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The sensor is divided into separate functional components: a first structure with light sources, a second structure with light receivers, and an elastic material connecting them. This segmentation allows each component to be optimized independently and simplifies integration into robotic fingers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Traditional mechanical strain gauge-based force sensors are replaced with an optical sensing system. Light sources emit light through the elastic material to light receivers, and displacement is measured optically rather than mechanically, reducing stiffness and integration complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If industrial F/T sensors are used with high resolution, then measurement precision is improved, but overload protection is limited and the sensors are easily damaged

Engineering Contradiction:

ImproveresolutionVSAvoidoverload protection

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The elastic material's physical properties (stiffness, elasticity) are optimized to provide both high resolution for small displacements and sufficient strength for overload protection. The optical measurement system can accurately measure very small displacements while the elastic material itself provides mechanical overload protection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The elastic material acts as a mechanical cushion that protects the sensor system from overload damage before excessive forces can damage the structures or electronics. The compliant nature of the elastic material prevents hard impacts from transmitting directly to sensitive components.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Measurement precision

If traditional F/T sensors are made stiff for precision, then measurement accuracy is improved, but compliance for dexterous manipulation is reduced

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidcompliance for manipulation

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The elastic material connecting the two structures provides compliance while maintaining measurement accuracy. This flexible element allows the sensor to adapt to dexterous manipulation tasks while the optical system maintains precision in measuring the compliant displacements.

Inventive Principle:

Principle #30Flexible shells and thin films

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 sensor achieves high sensitivity and accuracy in detecting small displacements, enabling effective dexterous manipulation with minimal footprint and cost, while maintaining compliance and ease of integration.

Implementation Method 1

an elastic material connecting the first surface of the first structure and the second surface of the second structure, the elastic material configured to displace in response to an external force

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a light source attached to the first surface of the first structure, the light source configured to emit a light beam; and a light receiver attached to the second surface of the second structure, the light receiver configured to receive the light beam

Methodology Applied

Scientific EffectLight transmission: Light

Implementation Method 3

an amount of the received light beam in relation to the emitted light beam is based on displacement of the elastic material in response to the external force

Methodology Applied

Scientific EffectPhotodetection: Photoelectric Effect

Data Source

PatentUS20250383249A1Systems, apparatus and methods for sensing force and torque

Publication Date: 2025.12.18 THE TRUSTEES OF COLUMBIA UNIV IN THE CITY OF NEW YORK

AI summary

Systems, apparatus and methods are disclosed for force and torque sensing techniques including a first structure having a first surface, a second structure having a second surface, and an elastic material connecting the first surface and the second surface. The elastic material is configured to displace in response to an external force. A light source attached to the first surface emits a light beam and a light receiver attached to the second surface receives the light beam. The change of the light beam is based on displacement of the elastic material in response to the external force. The light source can be a light-emitting diode (LED) or laser. The light receiver can be a photodiode or LED. A data converter translates the change of the light beam to a digital signal, which can control an actuator. The digital signal can be further processed.