PROJECT TITLE :
Actuator With Angle-Dependent Elasticity for Biomimetic Transfemoral Prostheses
Despite tremendous enhancements in recent years, lower-limb prostheses are still inferior to their biological counterparts. Most powered knee joints use impedance control, but it's unknown that impedance profiles are required to duplicate physiological behavior. Recently, we have developed a technique to quantify such profiles from standard gait information. Primarily based on this methodology, we have a tendency to derive stiffness needs for knee prostheses, and we tend to propose an actuation concept where physical actuator stiffness changes in function of joint angle. The idea is to specific stiffness and moment requirements as functions of angle, and then to mix a series elastic actuator (OCEAN) with an optimized nonlinear transmission and parallel springs to reproduce the profiles. By considering the angle-dependent stiffness demand, the higher bound for the impedance in zero-force management may be reduced by a factor of 2. We realize this ANGle-dependent ELAstic Actuator (ANGELAA) in a leg, with rubber cords as series elastic components. Hysteresis within the rubber is accounted for, and knee moment is estimated with a mean error of zero.7 Nm. The nonlinear parallel elasticity creates equilibria close to 0$^circ$ also ninety$^circ$ knee flexion, frequent postures in standard of living. Experimental analysis in an exceedingly test setup shows force control bandwidth around five–nine Hz, and a pilot experiment with an amputee subject shows the feasibility of the approach. While weight and power consumption are not optimized during this prototype, the incorporated mechatronic principles might pave the method for cheaper and lighter actuators in artificial legs and in other applications where stiffness requirements rely on kinematic configuration.
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