Closed-loop Position Control of a Pediatric Soft Robotic Wearable Device for Upper Extremity Assistance

TL;DR

This paper presents a closed-loop control system for a soft robotic wearable device designed to assist infant upper limb movements, using proprioceptive feedback and a PD controller to accurately track desired arm trajectories.

Contribution

It introduces a novel soft wearable device with proprioceptive feedback and a PD control scheme tailored for infant arm support and movement assistance.

Findings

Successful trajectory tracking on a mannequin model

Effective regulation of actuator pressure for desired movements

Potential for future infant reaching support applications

Abstract

This work focuses on closed-loop control based on proprioceptive feedback for a pneumatically-actuated soft wearable device aimed at future support of infant reaching tasks. The device comprises two soft pneumatic actuators (one textile-based and one silicone-casted) actively controlling two degrees-of-freedom per arm (shoulder adduction/abduction and elbow flexion/extension, respectively). Inertial measurement units (IMUs) attached to the wearable device provide real-time joint angle feedback. Device kinematics analysis is informed by anthropometric data from infants (arm lengths) reported in the literature. Range of motion and muscle co-activation patterns in infant reaching are considered to derive desired trajectories for the device's end-effector. Then, a proportional-derivative controller is developed to regulate the pressure inside the actuators and in turn move the arm along desired setpoints within the reachable workspace. Experimental results on tracking desired arm trajectories using an engineered mannequin are presented, demonstrating that the proposed controller can help guide the mannequin's wrist to the desired setpoints.