Gait generation for powered Hip-Ankle-Linkage-Orthosis

A hip-knee-ankle-foot orthotic system called `HALO'(Hip and Ankle Linked Orthosis) for paraplegic walking has been developed in our previous study. Each ankle joint of the HALO system is linked with a medial single joint via a wire which allows both feet of the orthosis to stay always parallel to the floor during walking and assists swinging the leg. The tests of the HALO system demonstrated that it allows smoother walking and easy don/doff. In order to improve further the characteristics of the previous design, we started a new project called pHALO aiming at further reducing of the energy expenditure during walking. As a difference from the previous solution where ankle joints were restrained, the new solution will incorporate two actuators to control the ankle joints angles. As an intermediate step from the development of the pHALO system, in this study we added to the existing system a feedback PI controller to control the ankle joint angle of the right foot in the push-off phase and conducted an experiment to evaluate the effect of the new design on the walking patterns and energy efficiency. The results showed longer stride length, faster gait speed, smaller variation of the CoG, and less energy consumption.