Rotational Magnetorheological Fluid Device and its Application

Magnetorheological (MR) fluids, a type of functional fluid, are capable of rapidly and reversibly altering their rheological properties in response to an external magnetic field.This unique characteristic enables their application in various mechatronic devices that require semi-active control of resistance and transmission forces.To integrate MR fluids into such force-control devices, two essential components are required: magnetic poles for applying a magnetic field to the fluid layer, and a mechanical structure capable of converting changes in the fluid's dynamic properties into device output.This paper provides an overview of rotary-type MR fluid devices in which the magnetic poles and the moving components are integrated and perform rotational motion.As application examples, we introduce two devices recently developed by the authors: a miniature MR fluid device using a cylindrical rotor, and a fail-safe MR fluid device using both electromagnets and permanent magnets.