Technique for finding the optimum geometry of electrostatic micromotors

A computer-based method for finding the optimum geometry of very small electrostatic motors based on the variable capacitance principle is presented. The geometry is taken into account and different excitation schemes are studied in order to find the maximum average output torque and/or the minimum vibration component in the output torque. Different combinations of stator and rotor poles are treated. The most important part of this optimization is automation of the procedure. For the actual calculation of the electrostatic field distribution, the finite element method is used. The mesh generation for the machine as a function of the rotor position and the design parameter is automated. The extraction of the torque and capacitance values is done in a batch procedure, constructed around a commercial finite element CAD (computer-aided design) package