Flexible Trunk Exoskeleton With Flexor Columns for Postural Torque

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Solution Overview

Problem

Current solutions for spinal cord injury-induced paralysis focus on constraining the trunk, leading to increased muscle fatigue and limited dynamic movements due to inefficient muscle recruitment and rapid onset of fatigue, particularly in activities like driving or performing daily tasks, without effectively leveraging the flexion relaxation phenomenon of the intact spine.

Innovation Solution

A trunk exoskeleton comprising a flexible corset with flexor columns and optional functional neuromuscular stimulation, which generates a combined torque to maintain trunk posture, mimicking the flexion relaxation phenomenon and reducing muscle effort, by using semi-elastic rods and electrical stimulation to enhance stability and mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If functional neuromuscular stimulation is used to improve trunk stability, then pelvic tilt and bimanual reaching are improved, but rapid onset of fatigue occurs and neuroprostheses cannot leverage the entire strength of the trunk musculature

Engineering Contradiction:

Improvetrunk stabilityVSAvoidduration of dynamic movements

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The device segments the trunk support function into multiple flexor columns distributed across the lumbar region, each independently generating flexor righting torque. This segmentation allows the system to distribute the mechanical workload across multiple passive elements rather than relying on a single active stimulation system, thereby reducing fatigue and enabling prolonged dynamic movements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The flexor columns are designed to automatically generate flexor righting torque when the torso is angled from vertical, without requiring continuous active control or stimulation. This self-service mechanism mimics the natural flexion relaxation phenomenon, allowing the system to maintain trunk stability passively during prolonged dynamic movements without rapid onset of fatigue.

Inventive Principle:

Principle #25Self-service

2Adaptability or versatility

If FNS is used to achieve large dynamic movements, then upright seated posture is maintained, but stimulated contractions produce 35% less torque than able-body muscles

Engineering Contradiction:

Improverange of trunk movementsVSAvoidtrunk muscle torque

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

The flexor columns act as passive counterweight elements that generate flexor righting torque to counterbalance the gravitational moment on the trunk. By positioning these columns strategically across the lumbar region, the system creates a mechanical counterweight effect that compensates for the reduced torque output of stimulated paralyzed muscles, enabling large dynamic movements without relying solely on FNS torque generation.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Stability of the object's composition

If current constraining solutions are used, then lateral stability is obtained, but bilateral hand use is limited and workspace is restricted

Engineering Contradiction:

Improveseated balance stabilityVSAvoidbimanual reaching capability

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The device uses a flexible corset structure with vertically oriented flexor columns that conform to the lumbar spine region. This flexible design provides lateral stability through the passive flexor righting torque of the columns while allowing greater freedom of movement compared to rigid constraining solutions, thereby enabling improved bimanual reaching capability and expanded workspace.

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 exoskeleton significantly reduces muscle fatigue and enhances trunk stability and mobility by generating a combined torque that mimics the flexion relaxation phenomenon, allowing for prolonged dynamic movements and improved functional capabilities.

Implementation Method 1

Each of the plurality of flexor columns generates a flexor righting torque when bent from a vertical orientation

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The one or more electrodes provide electrical stimulation to the user's muscles to generate stimulated trunk torque

Methodology Applied

Scientific EffectElectrical stimulation: Electrical Impedance Tomography

Data Source

PatentUS12478495B2Trunk exoskeleton

Publication Date: 2025.11.25 THE UNITED STATES OF AMERICA AS REPRESENTED BY THE DEPT OF VETERANS AFFAIRS

AI summary

A trunk exoskeleton is provided including a flexible corset configured to wrap around a user's torso in the lumbar spine region. The flexible corset includes a plurality of vertical pockets formed around its perimeter. A plurality of flexor columns are included, each of which positioned in one of the plurality of vertical pockets. The flexor columns generate a flexor righting torque when bent from a vertical orientation. The multiple flexor righting torques from each of the plurality of flexor columns combine to generate a combined flexor righting torque. The combined flexor righting torque comprises a portion of a user trunk torque when the user's torso is angled from vertical.