Model-based Prototyping of a Controller for MR Actuators

Magnetorheological (MR) actuators are semi-active devices that leverage the smart properties of the MR fluids whose rheology can be controlled by an external magnetic field. Within the presence of an external magnetic field, the magnetic domains of the MR fluid align with the external field, which results in the yield stress induced in the fluid, thus undergoing a transition from a fluid to a semi-solid. Thus, the control challenge for MR actuators is in controlling the rheology of the material by magnetic flux. Typically the control system is based on the coil’s current feedback. However, this approach based purely on the current control is not optimal since it is the magnetic stimuli that directly controls the material’s yield stress and not the current. Thus, this work investigates the capability of a flux controller in handling the non-linearities of the actuator, including magnetic hysteresis. A model of an MR actuator that incorporates the magnetic hysteresis and the control coil dynamics is developed. The flux controller is tuned to handle the addition of the hysteresis effect. The obtained results show that the chosen control topology is very effective for the considered flux commands inputs.