Design of a Magnetorheological Elastomeric Actuator: Analytical and Numerical Model With Experimental Validation

Abstract

This work presents the design and characterization of an innovative linear actuator based on a magneto-rheological elastomer (MRE) coupled to an electromagnet. According to technical literature, this class of materials has many potential applications in engineering fields, ranging from vibration control and suppression to actuator fields and hydraulic applications, such as integrated valves or peristaltic pumps. MREs are a class of smart materials where micrometric magnetic particles are suspended in an elastomeric matrix. We manufactured the MRE by using a 30% volume fraction of carbonyl iron particles in suspension in a commercial RTV silicon matrix, namely Sylgard 184. The MRE was cast in a membrane shape under vacuum, and its magneto-mechanical behaviour was modelled both analytically and by means of finite element simulations. The MRE membrane was coupled with a commercial electromagnet so that the magnetic field was able to provide controlled linear displacement in the axial direction, while the stiffness of the elastomeric matrix was exploited to bring the system back to its initial position. Two membrane thicknesses and two different gaps between the membrane and the electromagnetic actuator were manufactured and tested. Experimental tests were carried out on the actuator by measuring the stroke for a given magnetic field and by applying an external displacement and measuring the force for several current values in the four different actuator configurations. The results confirm that the analytical model can predict the actuator's behaviour in all the various combinations of parameters considered with good precision, which means that it can be easily used as a reliable design tool for this kind of smart system.