Walking-Assistance Apparatus as a Next-Generation Vehicle and Movable Neuro-Rehabilitation Training Appliance

Abstract

We have developed a prototype for a walkingassistance apparatus that serves as a next-generation vehicle or a movable neuro-rehabilitation training appliance for the elderly or motor palsy patients. Our prototype uses a novel spatial parallel link mechanism with a weight-bearing lift. The flat steps of the apparatus move in parallel with the ground; the apparatus supports complete leg alignment, including the soles of the feet, and assists walking behavior at the ankle, knee, and hip joints simultaneously. To estimate the walking phase of each leg of the user, pressure sensors were attached under the thenar eminence and the heel of the sole and the pressure variation at each sensing point was measured. To determine the direction in which the user is walking, a pressure sensor was attached to the flexible crural link. To adapt to the variations in the user’s walking velocity, the stride length and walking cycle while walking with the apparatus were compensated for using the concept of the walking ratio (the stride length times the walking cycle is constant). The apparatus can therefore be controlled in response to the user’s intent. We developed a control method for the apparatus by using impedance control, taking into account the dynamics of the apparatus and the user’s legs, as well as the assist ratio for the user. By adjusting the natural angular frequency of the desired dynamic equation for the user, our apparatus assists walking according to the user’s desired response. Motor palsy patients and those with weak muscles can walk with the assistance of the apparatus. Patients who have ambulation difficulty can also use the apparatus with a weight-bearing lift that we developed. Using the apparatus with this lift helps prevent stumbling and enables walking movement to be input to the brain’s motor area. The validity of the weightbearing lift is confirmed from the results of measured %Maximum Voluntary Contraction (%MVC).