Design and test of biologically inspired multi-fiber Hydro Muscle actuated ankle

Advancements in robotics are expected to have a profound impact on the economy, industry, jobs, education, health, warfare, space and planetary exploration etc. Progress in fields like Biomechatronics has the potential to further redefine the notion of human identity. An experimental platform for study of a biologically inspired muscular approach to joint actuation by synthetic Gastrocnemius, Soleus, and Tibialis Anterior muscles has been designed and the prototype tested. Three major lower leg muscle groups, that actuate a one degree of freedom ankle, have a multi-fiber composition allowing for active control of stiffness and force similar to recruitment in biological muscles. Muscle fibers actuating the lower leg utilize Hydro Muscle technology; fibers efficiently elongate when internal fluid, either water or air, is pressurized and contract when pressure is relieved. In contrast to the Pneumatic Artificial Muscle (PAM), McKibben artificial muscle, the Hydro Muscle can achieve strains identical to and even beyond a biological muscle. The viscoelastic properties of muscle fibers are also characterized. Results of preliminary position, stiffness, and force tests suggest that a substantial range of biological muscle performance can be achieved by the proposed muscle fiber recruitment approach. This platform could also provide a basis to create more realistic prosthetic legs that are able to mimic properly the form and movements of a human leg, allowing for not only better prosthetic integration but also more biologically accurate humanoid robotics. Furthermore this soft robotics platform allows for safer interaction and interface with the human body. The Hydro Muscle is an inexpensive actuator that could help reduce the high cost of current robotic options, allowing for a more wide spread adoption by society.