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Session 2559

A Programmable Controller/Driver for Electrostatic MEMS Micromotors

E. C. Wood and M. G. Guvench University of Southern Maine, Gorham, ME 04038

Abstract

This paper describes the design, operation, and use of a PC controlled drive circuit designed to be used to experiment with different drive waveforms on electrostatic MEMS (Micro-Electro-Mechanical-Systems) micromotors. The system designed features a selectible excitation pattern, a programmable frequency generator, and an adjustable high voltage source. The system features excitation patterns for wobble and rotary side drive micromotors. The excitation pattern generator was designed primarily to control wobble and rotary side drive micromotors, however, the system can easily be adapted to produce drive waveforms for almost any MEMS micromotor. Specifically, anyone possessing a universal programmer and the Xilinx Foundation Series Software can easily modify the excitation pattern generator to suit their needs. The excitation pattern generator offers maximum flexibility by allowing the pulse width applied to each stator to be varied from one to eight clock cycles. The system designed offers an adjustable high voltage source that only requires an input of 5V DC with a maximum supply current of 333 mA. In addition, the excitation frequency can be varied from 1Hz to 1 MHz. The operation of the controller is easy due to user friendly software that runs on a PC with the Windows95 or the Windows 98 operating system. The system designed is ideal for anyone doing research with MEMS micromotors.

1. Introduction

This paper describes the design, operation, and use of a PC controlled drive circuit designed to be used to experiment with different drive waveforms on electrostatic MEMS (Micro Electro Mechanical Systems) micromotors. The controller has been designed to drive different MEMS motors, namely, the wobble motor and the rotary side drive. Figure 1 displays a micrograph of a wobble motor with 12 stator electrodes while Figure 2 displays a micrograph of a rotary side drive motor with 8 rotor gears and 12 stator electrodes. These micromotors were designed along with some experimental sensor structures by one of the authors (Guvench) and fabricated at the Microelectronics Center of North Carolina through their "MUMPS" services. MEMS micromotors employ electrostatic attraction, rather than magnetic forces, and take advantage of relatively slow scaling of electrostatic forces at micrometer scales compared to the magnetic forces. Rotary motion is achieved by applying periodic pulses (20V - 200V peak) to a set of stators (typically 12) in a sequential manner from one stator to its neighbor so that the rotor experiences a net torque to spin at a rate proportional to the frequency of the waveform applied.[5,7]. Since optimal waveforms are not known, it is useful to have a drive waveform generator that can easily be adapted to control almost any micromotor. Currently, driver circuits for MEMS micromotors are not available on the market. Literature on MEMS does not supply information on a circuit or setup that can be reproduced either. In other words, one has to build the driver from scratch. One can observe that in some of the highly regarded and well referenced work[5] the investigation of the behavior of the motor designed was done with only two different pattern options available to the investigators, and worse, with waveform patterns having only six phases while half of the twelve poles needed to be driven.

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Wood, E., & Guvench, M. (2002, June), A Programmable Controller/Driver For Electrostatic Mems Micromotors Paper presented at 2002 Annual Conference, Montreal, Canada. 10.18260/1-2--10890