In this work, one and two degrees of freedom (DOF) lumped mass models of Micro-Electro-Mechanical System (MEMS) actuators are introduced, investigated, and comparedto experimental results. A one degree of freedom system representing the actuators out-of planebending motion under the electrostatic excitation is demonstrated. The capacitivegap between the movable plate and stationary electrode decreases when the microplateinclination angle is accounted for in the model.We investigate experimentally the primary, superharmonic of order two, and subharmonicof order one-half resonances of an electrostatic MEMS actuator under direct excitation.We identify the parameters of a 1-DOF generalized Duffing oscillator, model thatrepresents it. The experiments were conducted in soft vacuum in order to reduce squeeze-film damping and the actuator response was measured optically using a laser vibrometer.The predictions of the identified model were found to be in close agreement with the experimentalresults. We also identified the power level of process (actuation voltage) andmeasurement noise.A one DOF model of the actuator;;s torsional motion under the electrostatic torque isalso introduced. It was found that utilizing electrostatic actuation in torsional motion isnot e ffective. The maximum angle obtained was 0.04 degrees at high voltage. Finally, anovel two DOF model of the MEMS actuator;;s torsion and bending under electrostatic andelectromagnetic excitation was demonstrated analytically and compared to experimentalresults. Torsional motions were driven by a torque arising from a Lorentz force. It succeededin generating a large torsion angle, 1 degree at 1.35 T magnetic field density, anda current of 3.3 mA.
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