Magnetorheological fluids based multifunctional actuator for assistive knee braces

This paper is aimed to develop a new actuator used in assistive knee braces for helping elderly or disabled people to recover their mobility. In the design, magneto-rheological (MR) fluids are integrated into the actuator to provide controllable torque and improve the braking control performance. With MR fluids, the actuator possesses multiple functions as motor, clutch, and brake while meeting the requirement of normal walking as well. In this paper, design considerations including actuator configuration, magnetic circuit and influence of permanent magnet on MR fluids are discussed. Finite element model of the actuator is built and analyzed. Modeling of the actuator in different functions is presented. A prototype of the actuator is fabricated and tested. Braking torque control of the actuator is investigated. The results show that the developed multifunctional actuator is promising for assistive knee braces.