Motorized Trunk Control Backrest for Wheelchair Users

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Solution Overview

Problem

Individuals with spinal cord injuries face challenges in controlling their torso, limiting their ability to perform daily tasks due to lack of trunk control, with existing solutions being either restraining or requiring surgery.

Innovation Solution

A trunk control system comprising a harness assembly and flexion control assembly that allows selective movement of the backrest member between retracted and extended positions, using a tensioning component and motor controlled by a user input device to adjust the position, providing greater flexibility and support without surgical intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a seat belt at the chest level is used to assist with trunk posture, then the user can maintain a vertical seated posture, but the functional reach with both hands is restrained and the user cannot lean forward to relieve pressure or maintain center of mass on inclined surfaces

Engineering Contradiction:

Improvetrunk posture stabilityVSAvoidtrunk movement flexibility

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The backrest member is made dynamically adjustable between a first position (providing trunk support) and a second position (allowing forward lean). The motorized actuation system enables the backrest to transition between these positions, allowing the user to dynamically adjust trunk posture based on task requirements rather than being fixed in a single restrictive position.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If no seat belt is used and the user manually controls trunk position with arms, then the user can achieve fully flexed trunk postures, but the available workspace for bimanual tasks is dramatically limited and arms must be continuously engaged to hold position

Engineering Contradiction:

Improvetrunk position rangeVSAvoidbimanual task performance

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The trunk support system operates autonomously through motorized actuation controlled by simple user inputs (e.g., joystick or button). The system self-adjusts the backrest position to provide trunk support, freeing the user's arms from the continuous effort of manually holding trunk position, thereby enabling natural bimanual task performance.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If implanted electrodes in hip and back extensor muscles are used for functional neuromuscular stimulation, then trunk extension control can be achieved, but surgical intervention is required which not all persons with SCI are interested in having

Engineering Contradiction:

Improvetrunk control capabilityVSAvoidimplementation complexity

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The patent replaces the biological/neuromuscular approach (implanted electrodes and FNS) with a mechanical system consisting of a motorized actuator and backrest member. This mechanical substitution eliminates the need for surgical implantation while providing comparable trunk control functionality through external mechanical assistance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Stability of the object's composition

If a tight chest strap connected to a rigid backrest is used, then trunk posture can be assisted, but the system is considered a form of restraint with limited acceptance

Engineering Contradiction:

Improvetrunk posture supportVSAvoiduser restraint perception

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the rigid backrest and tight chest strap configuration with a more flexible, adaptive system. The backrest member can dynamically adjust its position and the harness assembly provides support without the rigid constraint of a fixed backrest, reducing the perception of restraint while maintaining trunk posture stability.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS11654311B2Trunk control systems and wheelchairs comprising same

Publication Date: 2023.05.23 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A trunk control system having a harness assembly and a flexion control assembly. The harness assembly has a backrest member and a harness secured to the backrest member. The backrest member is configured to be moveably coupled to a wheelchair. The backrest member is selectively moveable about and between a fully retracted position and a fully extended position. The harness cooperates with the backrest member to define a receiving space for receiving at least a portion of a torso of a wheelchair user. The flexion control assembly is coupled to the backrest member of the harness assembly. The flexion control assembly is configured to selectively permit or restrict movement of the backrest member about and between the fully retracted position and the fully extended position.