State-of-the-art teleoperation systems are installed in various fields such as disaster, underwater and surgical robots. However, their sensitive tasks cause psychological stress to operators. To reduce such stresses, bilateral controllers are used to achieve the force feedback function which can support operation skills with gravity / friction compensation and haptic perception. Therefore, we have developed several types of haptic devices with magnetorheological (MR) fluids as a core technology for fine haptics.
 MR fluids are composite materials made of ferromagnetic particles, medium oils, and several types of additives. Their rheological properties change rapidly, stably, and repeatedly with external magnetic fields. The basic properties of the MRFs have been investigated such as dynamic ranges of the MR effect for wide ranges of temperature and shear rates, and response times of the MR effect with the field input. However, better material selection from a viewpoint of the haptic feedback has not been sufficiently investigated. In our previous study, we evaluated the response characteristics of our haptic MRF clutch for three commercially available MR fluids containing micron-order ferromagnetic particles. However, we have not investigated using the newly developed MR fluids mixed with micro and nano ferromagnetic particle. Therefore, in our study, we evaluated the short-term response characteristics (step response, hysteresis characteristics) and long-term response characteristics (static response, repeatability) for a 0.3-Nm-class haptic MRF clutch with MR fluids mixed micro and nano ferromagnetic particle. According to the results on the repeat tests, the variation coefficients were 0.12% and 0.34% for 78% and 100% of the rated torque of the device, restrictive.
 

MR fluid,Haptics,long-term response