Analysis of Forces Exerted by Shoulder and Elbow Fabric-based Pneumatic Actuators for Pediatric Exosuits

2025-03-24

AI Summary

Pediatric upper-limb soft exoskeletons require precise characterization of fabric-based soft pneumatic actuators (SPAs) to ensure safe, effective force delivery and sufficient range of motion (ROM) across coupled joints. Method: We developed an infant-scale, dual-degree-of-freedom test platform integrating high-resolution force sensing and angular encoders to systematically quantify contact force output and ROM during shoulder abduction/adduction and elbow flexion/extension. The platform enabled the first quantitative assessment of inter-joint coupling effects—specifically, how anchor placement and adjacent joint angles modulate force–motion coupling. Contribution/Results: Results reveal that shoulder SPAs achieve maximal ROM and minimal peak contact force when the elbow is flexed to 90° with distal anchoring; elbow SPAs perform optimally at shoulder 0° with symmetric anchoring. Based on these findings, we propose a function–comfort co-optimization design principle and establish a reproducible mechanical calibration framework for pediatric soft exoskeletons.

Technology Category

• Intelligent Robots: Manipulation
• Planning, Routing, and Scheduling: Activity and Plan Recognition
• Humans and AI: Planning and Decision Support for Human-Machine Teams

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Abstract

To enhance pediatric exosuit design, it is crucial to assess the actuator-generated forces. This work evaluates the contact forces exerted by soft fabric-based pneumatic actuators in an upper extremity pediatric exosuit. Two actuators were examined: a single-cell bidirectional actuator for shoulder abduction/adduction and a bellow-type actuator for elbow extension/flexion. Experiments assessed the impact of actuator anchoring points and the adjacent joint's angle on exerted forces and actuated joint range of motion (ROM). These were measured via load cells and encoders integrated into a custom infant-scale engineered apparatus with two degrees of freedom (two revolute joints). For the shoulder actuator, results show that anchoring it further from the shoulder joint center while the elbow is flexed at $90^circ$ yields the highest ROM while minimizing the peak force exerted on the body. For the elbow actuator, anchoring it symmetrically while the shoulder joint is at $0^circ$ optimizes actuator performance. These findings contribute a key step toward co-optimizing the considered exosuit design for functionality and wearability.

Problem

• Evaluating contact forces in pediatric upper extremity exosuits
• Assessing actuator anchoring impact on force and joint ROM
• Optimizing exosuit design for functionality and wearability

Innovation

• Fabric-based pneumatic actuators for pediatric exosuits
• Anchoring optimization for force and ROM efficiency
• Custom infant-scale apparatus with load cells and encoders