Development of a Belt-actuated Robotic Platform for Early Rehabilitation

In order to promote early rehabilitation, we proposed a system which provides full-body arm-leg training for patients in a bed-lying position. As the preliminary development, a platform for leg movement was investigated. An innovative system with four servo drives was designed and manufactured. An artificial leg frame was attached to the platform via belts. The positions of the hip and knee joints were recorded using potentiometers. Closed-loop PID position control algorithms were implemented for production of various stepping movements. Technical evaluation on a test participant showed that the platform tracked the circular trajectory of the foot in a supine-lying position with an area difference of 8.2%, and produced walking-like trajectories in the hip and knee joints in a side-lying position with a mean error of 10.6%. The mechanical structure can be resized, and the control system can be expanded, so as to produce 3-dimensional stepping movement in both arms and legs. This innovative platform combined with the closed-loop position control strategy shows the technical potential to be a promising full-body rehabilitation platform for the patients in the early post-injury stage.

I. Introduction

Patients after neurological injury require a certain period of bed rest due to unstable physical state, orthostatic hypotension [1] or weak leg muscle. However, neuronal plasticity occurs immediately after the injury, and the outcome of neuroplasticity ultimately depends on the training activity [2]. To explore the largest potential of neuroplasticity, rehabilitation should be initiated even when the patients are restricted in the bed-resting phase. Furthermore, when the patients perform rehabilitation in a bed-lying position, they do not have concern about losing balance. The patients may be more focused on motor relearning [3,4]. Therefore, rehabilitation systems which allow training for the patients in a lying position are desirable.