First report on passive exoskeleton for easy running: PEXER IV

This paper proposes a passive-type exoskeleton called PEXER IV (Passive Exoskeleton for Easy Running, version IV) as shown Fig. 1 and its design objectives for development. PEXER IV is a wearable-type device, aiming reduction of physical load of a runner. The development of the assistive exoskeleton for running has some difficulties. The exoskeleton must sufficiently exert force to support a part of his/her upper body weight in the stance phase. It also allows the wearer to flex or extend his/her leg without any friction in the swing phase. Moreover, it should be a lightweight because the weight increases a gravitational and inertial effect. This paper therefore conducts preliminary experiments for investigation of the relationship between physical load, the support force and the weight of the exoskeleton. Results of preliminary experiments derive two necessary conditions for design of the exoskeleton. One is about the support force. The other is about limitation of weight of the exoskeleton. A variable length brace, including lock/unlock mechanism, allows the exoskeleton to support a part of the wearer´s body weight in stance phase and to freely swing his/her leg in the swing phase. Developed PEXER IV satisfies the conditions and this paper estimates decrease of physical load of 11.2 % at 6 [km/h].