Design and Control of a Low-cost Non-backdrivable End-effector Upper Limb Rehabilitation Device

TL;DR

GARD is a novel low-cost, non-backdrivable upper limb rehabilitation device with advanced control algorithms, demonstrating high precision and unique functionalities, aimed at improving stroke patient therapy.

Contribution

Introduction of GARD, a new rehabilitation device employing innovative motor velocity-control algorithms for superior control and stability in stroke therapy.

Findings

Mean trajectory error of 0.023mm in tasks

Achieves O(n) runtime complexity for arbitrary trajectories

Offers functionalities comparable or superior to commercial devices

Abstract

This paper presents GARD, an upper limb end-effector rehabilitation device developed for stroke patients. GARD offers assistance force along or towards a 2D trajectory during physical therapy sessions. GARD employs a non-backdrivable mechanism with novel motor velocity-control-based algorithms, which offers superior control precision and stability. To our knowledge, this innovative technical route has not been previously explored in rehabilitation robotics. In alignment with the new design, GARD features two novel control algorithms: Implicit Euler Velocity Control (IEVC) algorithm and a generalized impedance control algorithm. These algorithms achieve O(n) runtime complexity for any arbitrary trajectory. The system has demonstrated a mean absolute error of 0.023mm in trajectory-following tasks and 0.14mm in trajectory-restricted free moving tasks. The proposed upper limb rehabilitation device offers all the functionalities of existing commercial devices with superior performance. Additionally, GARD provides unique functionalities such as area-restricted free moving and dynamic Motion Restriction Map interaction. This device holds strong potential for widespread clinical use, potentially improving rehabilitation outcomes for stroke patients.