Design of a Highly Dynamical Actuator to Investigate the Transient Behavior of MR Fluids

In this contribution, optimization rules for achieving a fast response of the mechanical torque of MR actuators are proposed which are based on analytical models. Considering the electrical and magnetic domains, the design of the coil as well as the magnetic circuit are optimized with respect to the small- and large-signal behavior. Regarding the mechanical domain, the shear gap design as well as the shear-stress characteristic of the MR fluids are discussed with respect to dynamic aspects. Based on this method, a highly dynamical MR actuator with an axial shear gap is realized which is presented in detail. Furthermore, a stiff test rig is designed offering eigenmodes at high frequencies for the dynamic investigation. The outstanding dynamic of this actuator is proven by measurements considering large and small signal excitations under different load conditions. Fast switching times of about 5 ms for the torque of the MR actuator can be observed. Additionally, the transient rheological behavior is investigated experimentally by small signal excitations. The measurement results point out that an almost proportional behavior between flux density and torque generated by the MR effect can be assumed within a certain bandwidth.