Passive Compliance Coupling for Robot Joint Impact Safety

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Solution Overview

Problem

Current mechanical motion transmission devices in robots face challenges with slow response times, high energy consumption, lack of safety, and reliability issues due to external forces and shocks, particularly in passive compliance solutions that become rigid under significant efforts and lack customizable safety thresholds.

Innovation Solution

A mechanical device with a rotatable connecting interface that allows for elastic rotation between segments, enabling compliant behavior and returning to an initial state after impact, featuring adjustable safety thresholds through positioning of the drive means relative to a secondary axis, and incorporating an elastic return mechanism for enhanced reliability and security.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If passive compliance solutions are designed to deform for significant efforts, then compliance is improved, but safety deteriorates because they quickly become rigid for significant efforts

Engineering Contradiction:
ImprovecomplianceVSAvoidsafety
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The connecting interface is designed to be elastically rotatable about a secondary axis, allowing the device to dynamically adapt its compliance level. The elastic element enables the interface to rotate and absorb shocks while maintaining safety through controlled deformation rather than rigid failure

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The safety threshold is adjusted by changing the position of the drive means relative to the secondary axis. By varying this position, the torque threshold for engaging the elastic rotation can be modified, allowing customization of compliance behavior while maintaining reliable safety protection

Inventive Principle:
Principle #35Parameter changes

2Reliability

If active compliance solutions with force sensors and control means are used, then safety is improved, but response time deteriorates due to latency

Engineering Contradiction:
ImprovesafetyVSAvoidresponse time
Core Design Contradiction:
ReliabilityVSSpeed

Solution Approach 1:

The device uses passive elastic compliance mechanisms that automatically respond to external forces without requiring active sensing or control systems. The elastic element inherently provides immediate mechanical response to shocks and forces, eliminating sensor latency and control processing delays while maintaining safety

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces active electronic compliance systems (sensors and controllers) with a passive mechanical elastic rotation mechanism. This substitution provides instantaneous mechanical response to external forces, achieving fast response times without the latency inherent in electronic sensing and control loops

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

3Reliability

If passive compliance solutions become compliant when external forces exceed the safety threshold, then safety is improved, but adaptability deteriorates because they do not allow adjustment of the safety threshold

Engineering Contradiction:
ImprovesafetyVSAvoidadjustability
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The device provides dynamically adjustable compliance characteristics by allowing the drive means to be repositioned relative to the secondary axis. This enables real-time modification of the torque threshold without changing the fundamental elastic rotation mechanism, achieving both safety and adaptability

Inventive Principle:
Principle #15Dynamics

4Reliability

If custom safety thresholds are implemented by resizing devices, then safety is improved, but device complexity increases

Engineering Contradiction:
ImprovesafetyVSAvoidcost
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The device achieves multiple safety threshold configurations using a single universal design. By allowing the drive means to be repositioned along the secondary axis, one device can serve multiple applications with different safety requirements, eliminating the need for multiple customized device variants and reducing overall complexity and cost

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 device provides a more secure, reliable, and customizable compliant behavior, reducing bulkiness and cost while ensuring the device does not get damaged under impact, with adjustable safety thresholds for varying environments and uses.

Implementation Method 1

said drive means is connected to said assembly by a connecting interface, elastically rotatable about an axis of rotation, called secondary, fixed relative to said assembly

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

the connecting interface, being elastically rotatable, allows the device according to the invention to return to its initial state before an impact, for example

Methodology Applied
Scientific EffectElastic recovery: Elastic Recovery

Data Source

PatentEP3676062B1Mechanical device with passive compliance for transmitting rotational movement
Publication Date: 2022.12.21 CENT NAT DE LA RECH SCI (C N R S)
  • EP3676062B1 patent drawingFigure 1a~3
  • EP3676062B1 patent drawingFigure 4a~4b
  • EP3676062B1 patent drawingFigure 5a~5b

AI summary

The invention concerns a mechanical device (100) for transmitting rotational movement about an axis of rotation (106), referred to as the main axis of rotation, from a first segment to a second segment of a robot, said device (100) comprising: - a first assembly (102) intended to be attached to said first segment, - a second assembly (104) intended to be attached to said second segment, - a drive means (108) between said assemblies (102,104); characterised in that, on the side of one of said assemblies (104), said drive means (108) is linked to said assembly (104) by a connection interface (110) that is able to rotate elastically about an axis of rotation (112), referred to as the secondary axis of rotation, that is stationary with respect to said assembly (104), allowing said drive means (108) to rotate with respect to said assembly (104).