A leg exoskeleton utilizing a magnetorheological actuator

Exoskeleton systems that can enhance people's performance or assist disabled people have been investigated in recent years. However, most exoskeletons utilize DC motors with batteries as the driving source. While the motors require a lot of power, the working time of the exoskeletons is a limiting factor for the implementation of mobile exoskeletons. This paper proposes a new leg exoskeleton that uses a magnetorheological (MR) actuator to provide controllable assistive torque. The designed MR device can function as a brake or clutch according to the working states of the user. When adjustable passive torque is preferred, the MR device will work as a brake, thus only very low power is consumed; when active torque is required, the MR device will work as a clutch, which transfers the torque generated by the motor to the user's leg. The working states of the knee joint are determined by measuring the knee joint angle and the floor reaction force. Utilizing the MR actuator, the exoskeleton will he more energy efficient.