Evaluating Energy Consumption of an Active Magnetorheological Knee Prosthesis This paper presents a study of energy consumption of the AMRK, an Active Magnetorheological Knee actuator developed for transfemoral prostheses. The system consists of an active motorunit composed by an EC motor, harmonic drive and magnetorheological (MR) clutch; that is displayed in parallel to an MR brake. With this configuration, the AMRK can work as a motor, clutch, or brake, reproducing movements similar to those of a healthy knee. We used the dynamic models of the MR clutch, MR brake and motor unit to simulate the energy consumption during overground walking under three different situations: using the complete AMRK, using just the motorreducer of the AMRK, to simulate a common active prosthesis (CAKP), and using just the MR brake, to simulate a common semiactive prosthesis (CSAKP). The operation strategy of AMRK uses the motorunit only when concentric contraction is required to raise the body center of gravity during midstance. When power dissipation is required, only the MR brake operates. The results show that the AMRK spends just 14.8 J during the gait cycle, with is 3.9 times lower than the CAKP (57.2 J), while the CSAKP spends just 6.0 J.

MRLift: a Semiactive Lower Back Support Exoskeleton based on MR Fluid and Force Retention Technology Wearable robots suffer from issues of usability, costperformance, and battery life. These drawbacks hinder the development of their market and their implementation in healthcare and industry. Back support exoskeletons in particular rely heavily on mechanical storing of energy but are still mostly using traditional mechanical elements and actuators to achieve the task. The core technology of our work, named MRLink, uses a smart fluid in combination with a compression spring to produce a unique energy storeandrelease functionality. With only 5 Watts MRLink can produce over 500N of braking force. The braking force, variable viscosity, can be continuously controlled through the supply current. With appropriate selection of the spring and control method, the required assist energy can be acquired from body weight and movement dynamics, stored momentarily and, released at the appropriate timing to assist the body motion. The MRLink does not require an external power source like pneumatic actuators, does not require gearboxes and large batteries like DC motors, and comes in a compact package. Thus, this technology has the potential to significantly contribute to wearable exoskeletons in general, and back support exoskeletons in particular. In this work we present the development of a back support exoskeleton prototype based on MRLink, we describe its functional details, and a pilot test partially verifying the proposed functions.