Soft Semi-active Back Support Device with Adaptive Force Profiles using Variable-elastic Actuation and Weight Feedback

2026-03-03

AI Summary

This work proposes a lightweight, soft semi-active back support system that overcomes the limitations of existing devices—either bulky (active) or non-adaptive (passive)—by integrating variable-stiffness passive elements with pneumatic artificial muscle actuators. For the first time in a soft structure, the system enables coordinated control of discrete stiffness and active assistance. It leverages real-time forearm electromyography and upper-back inertial data to identify load-carrying states and dynamically modulate assistive force accordingly. Ex vivo and wearable experiments demonstrate significant reductions in lumbar extensor muscle activation across five participants during symmetric lifting tasks, with similar trends observed in asymmetric tasks, thereby validating the system’s adaptive assistance efficacy.

Technology Category

• Humans and AI: Interaction Techniques and Devices
• Intelligent Robots: Manipulation
• Machine Learning: Active Learning

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Search and Retrieval-Augmented AI: Assisted, interactive, and conversational search

Abstract

Portable active back support devices (BSDs) offer tunable assistance but are often bulky and heavy, limiting their usability. In contrast, passive BSDs are lightweight and compact but lack the ability to adapt their assistance to different back movements. We present a soft, lightweight, and compact BSD that combines a variable-stiffness passive element and an active element (an artificial muscle) in parallel. The device provides tunable assistance through discrete changes in stiffness values and active force levels. We validate the device's tuning capabilities through bench testing and on-body characterization. Further, we use the device's tuning capabilities to provide weight-adaptive object lifting and lowering assistance. We detect the weight handled by the user based on forearm force myography and upper-back inertial measurement unit data. Furthermore, electromyography analyses in five participants performing symmetric object lifting and lowering tasks showed reductions in back extensor activity. Preliminary results in one participant also indicated reduced muscle activity during asymmetric lifting.

Problem

• back support device
• adaptive assistance
• variable stiffness
• muscle activity reduction
• portable exoskeleton

Innovation

• variable-elastic actuation
• weight-adaptive assistance
• soft wearable robotics
• force myography
• semi-active back support