T.-B Johansson

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.<<ETX>>

3D optimization of average torque of electrostatic micromotors

The paper presents a technique to optimize electrostatic micromotors. The finite element technique is combined with different types of optimization strategies, one of them, a version of the evolution strategy is discussed. It further involves an automated generation of 3D meshes where the dimensions and rotor positions of the motor models can be chosen arbitrarily. It also involves constructing equivalent circuit models for the electrostatic motors. Both, the automated 3D mesh generation and the construction of the equivalent circuit model are treated in detail in this paper. The possibilities of producing powerful tools in the field of optimization are described, but also some warnings and limitations concerning the automated optimization are mentioned.

Design and optimisation of electrostatic micromotors

This paper presents the techniques used to optimise the geometry of electrostatic micromotors for maximum average torque. The optimisation of the geometry is done under consideration that the excitation is also optimised for maximum average torque. The most important part of this optimisation is automation. Automation of the mesh generation for the finite element calculation, and of the equivalent circuit generation, are the parts that produce an optimisation-tool out of an otherwise fairly tedious technique.<<ETX>>