Technique for finding the optimum geometry of electrostatic micromotors

This paper presents a computer-based method for finding the optimum geometry of very small electrostatic motors based on the variable capacitance principle. Not only is the geometry taken into account, but 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 parameters is automated. The extraction of the torque and capacitance values is done in batch procedure, constructed around a commercial finite-element CAD package. This automation makes the system an optimization tool of an otherwise very tedious technique