Passive Compliant Wrist for Upper Limb Prosthesis

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Solution Overview

Problem

Existing prosthetic wrist units are bulky and restrict wrist movements, limiting the ability of amputees to perform daily activities due to limited degrees of freedom and a robotic appearance.

Innovation Solution

A passive compliance wrist unit for upper limb prostheses that allows for Extension/Flexion, Radial/Ulnar Deviation, and Supination/Pronation movements using a compliant four-bar mechanism and snap-clip buttons, with a flexible and water-resistant design having no mechanical moving parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional prosthetic wrist units are used, then structural stability is maintained, but wrist movement freedom is restricted and the design becomes bulky

Engineering Contradiction:

Improvewrist movement freedomVSAvoidwrist unit size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The wrist unit is divided into multiple independent degree of freedom joints (radial/ulnar deviation joint, extension/flexion joint, supination/pronation joint), each capable of independent movement. This segmentation allows the wrist to achieve complex movements without requiring a single bulky universal joint, thereby increasing movement freedom while reducing overall volume.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs flexible materials and thin-film structures in the wrist unit construction, replacing traditional rigid mechanical components. This allows the wrist to achieve compliance and natural movement patterns while maintaining a compact, sleek appearance that does not add bulk to the prosthetic device.

Inventive Principle:

Principle #30Flexible shells and thin films

2Adaptability or versatility

If additional mechanical parts are added to increase degrees of freedom, then wrist functionality is improved, but device complexity increases

Engineering Contradiction:

Improvedegrees of freedomVSAvoidmechanical parts

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple degree of freedom capabilities (radial/ulnar deviation, extension/flexion, supination/pronation) are integrated into a unified wrist unit structure. The patent combines these different movement types into a single compact assembly rather than using separate mechanical systems, thereby increasing functionality while reducing overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces traditional complex mechanical joint systems with compliant mechanisms and flexible structures. This substitution eliminates the need for numerous separate mechanical parts, bearings, and actuators, achieving multiple degrees of freedom through material compliance and geometric design rather than complex mechanical assemblies.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If circular bearing design is used, then manufacturing is simplified, but appearance becomes robotic and movement is limited

Engineering Contradiction:

Improvebearing designVSAvoidwrist appearance

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The patent employs asymmetric and organic shapes in the wrist unit design, departing from traditional circular bearing configurations. The wrist components feature natural, anatomically-inspired geometries that provide multiple axes of rotation and movement while creating a sleek, non-robotic appearance that blends better with the user's body.

Inventive Principle:

Principle #4Asymmetry

4Adaptability or versatility

If traditional prosthetic wrist design is used, then structural robustness is maintained, but water resistance and compliance are reduced

Engineering Contradiction:

ImprovecomplianceVSAvoidwater resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent utilizes flexible, water-resistant materials and thin-film encapsulation techniques to create compliant wrist joints that can move naturally while maintaining water resistance. The flexible shell design allows for compliant movement without requiring open mechanical joints that would be vulnerable to water ingress, thereby achieving both compliance and reliability in wet environments.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS20250186228A1A passive compliant wrist for upper limb prosthesis

Publication Date: 2025.06.12 LIFE & LIMB PTE LTD

AI summary

The present disclosure relates to the field of artificial limbs for amputees and specifically to a passive compliant wrist unit 210 for upper limb prosthesis. The passive compliant can comprise a plurality of fingers controlled by a compliant four bar mechanism. The arm is capable of extension/flexion, radial/ulnar deviation on application of a force on the snap joint. The limb is also capable of pronation/supination actions. By application of a force on an arm snap joint, the flexible wrist 216 can be adapted to perform extension/flexion, radial/ulnar deviation.