Evaluation of open-loop torque performance of haptic MR fluid clutch

State-of-the-art teleoperation systems are installed in various specialized robots, such as disaster, underwater, and surgical robots. However, the sensitive nature of their tasks causes psychological stress in operators. To reduce this stress, bilateral controllers are used to achieve a force feedback function that can support operational skills with gravity/friction compensation and haptic perception. Therefore, we developed several types of haptic devices with magnetorheological (MR) fluids as the core technology for fine haptics. MR fluids are composite materials comprising ferromagnetic particles, medium oils, and several types of additives. Their rheological properties change rapidly, stably, and repeatedly with the application of an external magnetic field. In our previous study, we developed desktop and standalone MR fluid (MRF)-based haptic devices for surgical simulations. However, handheld devices have not yet been developed. Therefore, we designed and developed a compact MR fluid device with a total mass and maximum torque of approximately 100 g and 0.3 Nm, respectively. Static, step, hysteresis, and repeat tests were conducted for the 0.3 Nm-class MRF device. According to the results of the repeat tests, the variation coefficient was 0.5% for a current input of 0.5 A, demonstrating the suitability of the developed device as a fine haptic generator.