Design of an Adjustable Fail-Safe MRF Clutch With a Novel Field Blocking Mechanism for Robotic Applications

A permanent magnet-based magnetorheological fluid clutch (MRF) with a novel field blocking mechanism for torque adjustment is presented in this article. Magnetostatic simulations were used to optimize the design of the MRF clutch so as to increase its performance. A magnetic flux density measurement setup was used to confirm the correctness of the magnetostatic simulations. The MRF clutch was then characterized by measuring the transmitted torque with different magnetization and input angular velocity conditions. In addition to this, a 3D printed gripper was used to test the use of the MRF clutch both in normal working conditions and as a torque-limiting fail-safe mechanism. A torque control system which used an unscented Kalman filter to produce a torque feedback signal was implemented to showcase the use of the gripper under normal conditions. A simulated failure case in which the driving actuator was driven at its maximum velocity was then used to test the MRF clutch as a fail-safe mechanism.