Back-drivability of powered knee orthosis for knee free swing and knee extension

Nowadays, Powered Knee Orthosis (PKO) becomes an important assisting device in helping rehabilitation activities such as hemiplegic gait, neuropathic gait and stroke gait. A few existing PKO are mainly designed to assist the rehabilitation activities. However, most of the developed PKO restricted to external power to drive them to perform knee flexion or extension. This leads to discouragement of natural volunteer able-body in assisting movement with PKO and avoid the use of functional electrical stimulation, FES simultaneously with the developed PKO. This paper presents the design and development of a novel powered knee orthosis with high back-driveability that allows knee free swing activities and knee extension with PKO for rehabilitation purposes. The PKO designed uses the Outrunner type of brushless DC motor (BLDCM) as an actuator that used to give an external power to drive knee flexion or extension and also able to allows natural volunteer able body movement. A knee free swing and knee extension experiments were carried out and tested on three healthy subjects by measuring the knee angle movement both with and without the PKO. The results demonstrate the effectiveness of the proposed PKO. Thus the developed PKO is able to assist knee free swing and knee extension activities with highly back drivability with no external power.