Digital Fluid Power for Exoskeleton Actuation – Guidelines, Opportunities, Challenges

Exoskeleton technology is currently getting a strong momentum by increasing academic and industrial R&D work, by the foundation of new enterprises, and by rising sales numbers. More and more rumours are circulating about hydraulic actuation. Hydraulics companies are exploring the business opportunities as a basis to decide on investments in the development of appropriate hydraulic actuation technologies. This paper starts with some insight into the state of the art of exoskeletons and actuation technologies. General requirements are discussed first. More specific ones are studied by the simulation of a knee joint actuator for two specific motions, a squat and fast walking. Finally, the concept of a digital hydraulic cylinder and its control by a hydraulic binary counter for a knee joint is presented. It is assessed by these two motions and some design aspects are discussed.