Development of Hybrid Ankle Foot Prosthesis

Abstract

Limb loss of humans produces a permanent disability that impacts the amputee s self-confidence, self-care, and limb movement. Specifically, lower limb loss results in slow and less stable locomotion. Below-knee (transtibial) amputation is one of the most frequent types of amputation around the world. The ankle-foot prosthesis is one of the solutions meant to provide support and assistance to the transtibial amputee. The majority of available ankle-foot prostheses are passive and not able to provide required push-off and seamless movement during locomotion. However, active ankle-foot prostheses can provide desired characteristics and seamless operation to achieve by embedding subject locomotion intention in the control sequence of the prosthesis. EMG signal is a well-reorganized way of capturing neural information of human limb movements to identify the locomotion intention of the subject. The prime objective of the present research work was to develop a hybrid ankle-foot prosthesis prototype. Here, the EMG signal of six lower limb below-knee muscles for non-weight bearing and weight-bearing dorsiflexion/plantarflexion ankle-foot movements had been analyzed. Tibialis Anterior and Gastrocnemius muscles had been found suitable for repetitive ankle-foot movements. Further, to incorporate subject locomotion intention in the control sequence of the prosthesis, hybrid information (EMG+knee joint angle) based activity and locomotion prediction module had been designed. It had a two-level classification approach, the first level of classification predicts the activity (standing or walking) of the subject, whereas the second level predicts the locomotion (level walking, stair ascent, stair descent, ramp ascent, and ramp descent) intention of the subject only if at level-1 walking activity had been identified. EMG signal of four lower limb muscles