Algorithms for the Real-Time Compensation of Hysteresis in MR Actuators Caused by Partially Filled Shear Gaps

Magnetorheological fluids (MRF) are suspensions of fine, magnetically polarizable particles in a non-magnetic carrier fluid. Under the influence of a magnetic field the particles form chains in the direction of the field lines, whereby the resulting shear stress can be changed high dynamical, largely linear with a good reproducibility by several orders of magnitude. Furthermore, the MRF technology provides a drag torque-free operation by a magnetically induced MR-fluid movement control, resulting in new perspectives regarding the increase of energy-efficiency with improved switching dynamics and comfort for applications e.g. in the powertrain of vehicles. A certain drawback of the MR-fluid control is a hysteresis behavior of the torque generation with respect to the controlling current caused by the partially filled shear gaps. In addition, the hysteresis depends on the rotational speed due to the resulting centrifugal forces, so that the influence of this external disturbance must be compensated, too. In order to obtain a linearized force characteristic of the actuator, a modified Prandtl-Ishlinskii approach for the hysteresis compensation is designed, parametrized and validated by experiments within this paper.