(A) study of an active ankle foot orthosis for stabilization in gait with spasticity

Abstract

In this paper, a cable-driven ankle foot orthosis (AFO) for gait stabilization of spastic patients is introduced. Spasticity is a phenomenon in which the movement of a joint becomes stiff due to increased muscle tension. In particular, spastic joints have a speed-dependent characteristic. The faster the joint speed, the more contracture occurs, in which the muscles momentarily stiffen on the spot. This phenomenon in the ankle joint, which has a great influence on gait stability, is directly related to the patient's safety, and gait stabilization through precise assistance is required. Therefore, in this paper, the active AFO that can precisely control the ankle of a spastic patient by considering the speed-dependent characteristics is proposed. The ankle is fixed with a rigid frame to prevent deformation of the spasticity, and it is designed in consideration of wearability and safety so that daily life can be sufficiently performed. In addition, a control algorithm to prevent contracture was implemented and confirmed that gait assistance is performed within a range that does not exceed the critical speed at which contracture occurs. Furthermore, the ankle joint of the spastic patient was implemented in the normal ankle joint, and as a result of the gait test, the improved gait stability and symmetry by the proposed active ankle brace were verified.