Design and Preliminary Evaluation of a Torso Stabiliser for Individuals with Spinal Cord Injury

2024-03-26

arXiv.org

AI Summary

Spinal cord injury (SCI) patients face elevated fall risk due to trunk instability, yet existing stabilizers suffer from excessive rigidity and restricted mobility. To address this, we propose a non-restrictive, single-degree-of-freedom mechanical trunk stabilizer inspired by centrifugal clutches and automotive seatbelts. Its novel velocity-threshold–triggered (80–100 cm/s) passive dual-mode control—transparent during low-speed daily activities and compliant impedance upon high-speed imbalance—enables seamless transition between modes. Integrated motion capture, OpenSim musculoskeletal modeling, and mechanical design optimization determined an optimal 55–60 cm unconstrained stroke length. Prototype evaluation confirmed preservation of natural trunk kinematics, reliable mode switching, and immediate pre-fall protection. This work overcomes the traditional trade-off between functional support and user comfort in rigid trunk-support devices.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Computer Vision: Motion & Tracking
• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Large-scale security measurements

Abstract

Spinal cord injuries generally result in sensory and mobility impairments, with torso instability being particularly debilitating. Existing torso stabilisers are often rigid and restrictive. We present an early investigation into a non-restrictive 1 degree-of-freedom (DoF) mechanical torso stabiliser inspired by devices such as centrifugal clutches and seat-belt mechanisms. First, the paper presents a motion-capture (MoCap) and OpenSim-based kinematic analysis of the cable-based system to understand the requisite device characteristics. The evaluation in simulation resulted in the cable-based device to require 55-60,cm of unrestricted travel, and to lock at a threshold cable velocity of 80-100,cm/s. Next, the developed 1-DoF device is introduced. The proposed mechanical device is transparent during activities of daily living, and transitions to compliant blocking when incipient fall is detected. Prototype behaviour was then validated using a MoCap-based kinematic analysis to verify non-restrictive movement, reliable transition to blocking, and compliance of the blocking.

Problem

• Develop non-restrictive torso stabiliser
• Address spinal cord injury instability
• Ensure compliance during daily activities

Innovation

• 1-DoF mechanical torso stabiliser
• MoCap and OpenSim kinematic analysis
• Compliant blocking for fall detection