Walking Assistance for Cerebral Palsy with Robot Suit HAL

Abstract

The purpose of this study is to propose a method of a walking assistance by using an exoskeletal system “Hybrid Assistive Limb (HAL)” for cerebral palsy (CP) patients who cannot stand up and walk due to the abnormal generation of the bioelectrical signals (BES) in their lower limbs associated with the brain disease, and to verify the effectiveness of the proposed method through a clinical trial. HAL was developed to support the voluntary movement of the wearer based on the BES. The proposed method consists of two algorithms, that is, an assistance of voluntary movement in the swing phase and an assistance of weight bearing in the stance phase. The assistance of the voluntary movement determines the rotational direction of the actuator from the ratio of the abnormal BES by using sigmoid function during the swing phase. On the other hand, the assistance of the weight bearing adjusts automatically the stiffness and viscosity of the joint during the stance phase. In the clinical walking trial with a 3-meter walk using parallel bars, we confirmed that HAL including the proposed method achieved the patient's walking assistance. Especially, the assistance of the voluntary movement in the swing phase produced his leg-swing based on the BES signals. As a result, the walking speed, cadence and stroke width of the patient with HAL during this trial are 1.6m/min, 11.4 steps/min and 0.14m, respectively. In conclusion, we have proposed the method of the walking assistance method and thus, confirmed the effectiveness of the proposed method.