Automated 3D mesh generation for efficient torque computation of electrostatic micromotors

The application range of micromotors leads from systems for the maintenance of fine tubes in power plants to inspection of blood vessels in the human body. One of the requirements for implementing motors in such applications, is that their outer dimensions has to be reduced dramatically. Major developments in the past years have been done in the field of fabrication technologies, in order to process sufficiently small motors. At this moment, investigations are carried out to predict the operational behaviour and to optimise the shape of such micromotors, in order to fit into the specific operations. A conceivable problem is that friction effects become more significant as the dimensions are scaled down. In addition to this, torque pulsation excited by the electric field causes problems during operation. In this paper an efficient way to calculate the average torque and the torque ripple of electrostatic micromotors will be demonstrated. An equivalent circuit is derived from the field solutions which are obtained using a finite element (FE) technique. Due to the axial very flat geometry of most of the electrostatic micromotors a 3 dimensional evaluation of the field problem is necessary. Different motor concepts will be discussed comparing the torque ripple and the average torque