Rajendra K. Godara and Manish M. Joglekar* Pages 99 - 113 ( 15 )
Background: This article presents a feedforward control technique to mitigate the contact bounces in electrostatically driven beam type nonprismatic microswitches. A comprehensive electromechanical model incorporates the effect of variable electrode geometry, large displacement effects, fringing field effect and squeeze film damping. The model allows the movable electrode to make an elastic contact with the dielectric substrate. In the investigation, the dielectric substrate is modeled as nonlinear spring-damper system. In order to discretize the resulting partial differential equation into ordinary differential equations, the Galerkin’s method is applied. The proposed technique relies on force equilibrium at a point during the transition between ON and OFF state of the switch. In order get reduced switching time variations in the geometry of the micro switch are exploited. The maximum reduction in switching time is 48% in the case of fixed-free microbeam and 54% in the case of the fixed-fixed microswitch. It is observed that the proposed technique mitigates the contact bounces significantly with reduced switching time.Methods: A feedforward control technique is proposed for controlling the contact bounces of electrostatically driven nonprismatic microbeams. To obtain the fundamental eigenfrequencies and associated modes shapes of nonprismatic microbeams the differential transform technique is employed. Further, to simulate the electromechanical response of electrostatically actuated beam type nonprismatic microswitches the Galerkin’s modal superposition technique is used. Results: A feed-forward control technique has been devised in order to suppress the contact bounces in the continuous microsystems. Further, the geometry variation of the micro switches is exploited in order to get reduced switching time. It has been demonstrated that over the range of taper parameter taken into consideration the proposed control strategy works well and is able to suppress the contact bounces significantly. Conclusion: The simultaneous application of nonlinear shapes of microbeams and proposed feedforward control technique result into the enhanced dynamic performance of the electrostatic MEMS switches.
Nonprismatic beam, electrostatic MEMS, contact bounces, microswitches, reliability.
Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, Roorkee- 247667