A magnetorheological actuation system: test and model

Abstract

Self-contained actuation systems, based on frequency rectification of the high frequencymotion of an active material, can produce high force and stroke output. Magnetorheological(MR) fluids are active fluids whose rheological properties can be altered by the applicationof a magnetic field. By using MR fluids as the energy transmission medium in such hybriddevices, a valving system with no moving parts can be implemented and used to control themotion of an output cylinder shaft. The MR fluid based valves are configured in theform of an H-bridge to produce bi-directional motion in an output cylinder byalternately applying magnetic fields in the two opposite arms of the bridge. Therheological properties of the MR fluid are modeled using both Bingham plasticand bi-viscous models. In this study, the primary actuation is performed using acompact terfenol-D rod driven pump and frequency rectification of the rod motion isdone using passive reed valves. The pump and reed valve configuration alongwith MR fluidic valves form a compact hydraulic actuation system. Actuatordesign, analysis and experimental results are presented in this paper. A timedomain model of the actuator is developed and validated using experimental data.