Design and testing of assistive knee brace with magnetorheological actuator

Magnetorheological (MR) fluid is a smart fluid that its rheological behavior can be controlled by magnetic field. Rotary devices using MR fluids have the benefits of high torque, good controllability, and low power requirement. Recently, we developed a new MR actuator to be applied to an assistive knee brace. It was demonstrated that the MR actuator can provide sufficient torque for normal human activities. In this research, we develop an assistive knee brace that utilizing this MR actuator together with a DC motor. When active torque is desired, the DC motor works and the MR actuator functions as a clutch to transfer the torque generated by the motor to the leg; when passive torque is desired, the DC motor is turned off and the MR actuator functions as a brake to provide controllable passive torque. Potentiometer and strain gauges are used to detect the position and force information of the knee brace. The knee brace can provide active or passive assistive torque based on the working condition of the knee brace. A testing structure is developed for testing the knee brace. The motion of the knee brace in the testing structure is analysed. Preliminary experiments are carried out and the results show that this knee brace can provide proper assisting torque as expected.