A new FEM approach for field and torque simulation of electrostatic microactuators

A novel finite-element method (FEM) floating-conductor formulation for the numerical electromagnetic analysis of electrostatic microactuators is presented and discussed in this paper. It is based on the assumption that the moving part of the microdevice can be modeled as a perfect conductor and leads to a considerable reduction of the mesh size, as the region occupied by the moving part does not need to be discretized at all. It is also shown that the developed formulation can be easily coupled with the well-known method of equivalent charges for the computation of the driving torque acting upon the rotor of the microdevice. This coupling is performed directly in terms of variables involved in the solution process of the final algebraic system and it allows acquiring torque information without any postprocessing operation. The proposed approach has been applied to the analysis of an electrostatic micromotor with radial field. When compared to simulations obtained with a commercial FEM electromagnetic code using a classical high-permittivity formulation, this method proves to be accurate and exhibits an overall reduction of preprocessing, processing and postprocessing time.