Design and kinematic investigation of an actuated prosthetic ankle during walking

Abstract

Due to the varied needs of persons who have lost a lower limb in their everyday lives, ankle-foot prosthetic technology is continually evolving. Numerous prosthetic ankles have been created in recent years to restore the ankle function of lower limb amputees. Most ankle foot prostheses, on the other hand, are passive, such as the solid ankle cushion heel and the energy storage and release foot (ESAR). The solid ankle foot can only provide steady vertical support during ambulation; however, the ESAR foot can store energy and gradually release it throughout human walking periods, hence increasing the walking pace of amputees. The aim of this work is to describe the design and manufacture of an actuated ankle-foot prosthesis. The main benefit of powered ankles is that they are capable of mimicking natural stride, particularly in steep or uneven terrain conditions. The primary objective is to establish two degrees of freedom of ankle rotation in two planes, plantar flexion and dorsiflexion in the sagittal plane, besides inversion and eversion in the frontal plane. As software can improve the gait stability, an automatic modifiable transmission arrangement was prepared for delivering the current design motions in the sagittal plane based on empirical collected biomechanical data related to passive prosthetic normal gait circumstances. However, the ankle rolling in the frontal plane was guided mechanically by means of mono leaf spring. The majority of the ankle mechanical components are made of 7075-T6 aluminum alloy and are integrated onto ESAR carbon fiber laminated foot. For a unilateral above-knee amputee, the ankle function at self-selected walking was assessed, achieving maximum results of 10° inversion, 10° eversion, 12° plantar flexion and 18° dorsiflexion ankle angles. Also, the patient gait experiment in a normal cadence showed an improvement in plantar flexion behavior for the powered ankle in contrast with the passive ankle