Compliant Force Sensing System for Legged Robots

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional strain gauge based force/torque sensors are fragile, sensitive to inertial noise, and expensive, making them unsuitable for dynamic physical interactions, particularly in applications like legged robots undergoing ground locomotion where lightweight, cost-effective, and robust sensing systems are needed for accurate force and contact location measurement.

Innovation Solution

A sensing system comprising a compliant contact pad and multiple sensors that detect physical parameters associated with deformation, using a trained statistical model to determine the magnitude, direction, and contact location of forces applied, allowing for improved shear sensitivity and contact detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If strain gauge based force/torque sensors are used, then force and torque measurement capability is achieved, but the system becomes fragile and sensitive to inertial noise

Engineering Contradiction:

Improveforce measurement accuracyVSAvoidsensor robustness

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces traditional strain gauge based mechanical sensing systems with a compliant sensor system that uses a soft compliant body and capacitive sensors. This substitution eliminates the fragility and inertial noise sensitivity of strain gauges while maintaining force measurement capability through measurement of compliance body deformation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs a compliant body made from soft materials that deforms under applied forces. This flexible structure replaces rigid strain gauge mounts, providing inherent robustness while enabling force sensing through deformation measurement, directly addressing the reliability issue.

Inventive Principle:

Principle #30Flexible shells and thin films

2Measurement precision

If conventional force sensors are used, then force sensing capability is provided, but the system becomes expensive

Engineering Contradiction:

Improveforce sensing accuracyVSAvoidsystem cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent uses inexpensive capacitive sensors and soft compliant materials instead of expensive strain gauge assemblies. The compliant body can be manufactured from low-cost elastomers or similar materials, significantly reducing system cost while maintaining adequate measurement precision for the application.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The replacement of expensive strain gauge based mechanical sensing with a combination of soft compliant body and capacitive sensing provides a cost-effective alternative that maintains force measurement capability without requiring precision mechanical components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Weight of moving object

If lightweight sensing systems are used for dynamic interactions, then suitability for legged robots is improved, but measurement precision may be compromised

Engineering Contradiction:

Improvesensor system weightVSAvoidforce measurement accuracy

Core Design Contradiction:

Weight of moving objectVSMeasurement precision

Solution Approach 1:

The compliant body is constructed from soft, lightweight materials such as elastomers that can be formed into thin-walled structures. This provides the necessary compliance and deformation for sensing while keeping the overall mass low, suitable for dynamic robotic applications.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs composite structures combining soft compliant materials with embedded capacitive sensors. This composite approach enables lightweight construction while maintaining measurement precision through the synergistic combination of material compliance and electronic sensing.

Inventive Principle:

Principle #40Composite materials

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 system provides accurate and robust force and contact location measurement, enhancing the ability to infer contact details and estimate allowable contact force ranges, suitable for dynamic systems like legged robots, with a balance between accuracy and computational cost.

Implementation Method 1

sensors configured to detect a physical parameter associated with deformation of the compliant contact pad

Methodology Applied

Scientific EffectDeformation: Deformation

Implementation Method 2

Some force sensors may rely on capacitive techniques

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Data Source

PatentUS11300397B2Compliant force sensing system

Publication Date: 2022.04.12 MASSACHUSETTS INST OF TECH

AI summary

Sensing systems as well as their methods of operation and training are described. In some embodiments, a sensing system may include a compliant contact pad configured to contact an environment, and a plurality of sensors configured to detect a physical parameter associated with deformation of the compliant contact pad. A processor configured to receive signals from the plurality of sensors may determine a magnitude and direction of a force applied to the compliant contact pad.