Design and characterization of a magnetorheological elastomer linear actuator for low-frequency applications

This work presents the design and characterization of an innovative linear actuator for low-frequency applications based on a magnetorheological elastomer (MRE) disc coupled to an electromagnet. MREs are a class of smart materials in which micrometre-sized magnetic particles are suspended in an elastomeric matrix. Most research works study their applicability as semi-active systems, but less effort is devoted to their applicability in actuators, but their applicability in the field is possible and could lead to potential advantages in terms of integration of the system especially for microactuation. The proposed MRE device relies on a commercial electromagnet which provides linear motion of the MRE element. The stiffness of the elastomeric matrix is exploited to bring the system back to its initial position, so that the system is monostable. The magneto-mechanical behaviour is modelled both analytically and by means of finite element magneto-mechanical simulations, and the models are compared with the experimental tests. Two membrane thicknesses and two different gaps between the membrane and the electromagnetic actuator were manufactured and characterized. The results show the effect of the design variable on the actuator behaviour and confirm that the analytical model provided can predict the actuator's behaviour with a good approximation in all the configuration analysed. The dynamic range of the proposed system, regardless of the configuration selected, demonstrates that the magnetic contribution is always able to increase the actuator force by 50% and that the provided model can easily be used as a reliable design tool for this kind of smart system.