Introduction

A wide variety of MEMS devices has been built recently by using the VLSI processing techniques. Various MEMS devices applications can be found in [2][3][1][8][9][6]. During the designing process, it is very desirable to predict the effect of change of parameters. For some MEMS devices, it is tedious to derive analytic dynamic equations. Even if all equations are given, it is usually still tedious to solve them analytically to predict the dynamic behavior of the system. Therefore a general purpose dynamic simulator would be an excellent tool to study the design.

To build a reasonable simulation, one has to consider the following issues:

1. Simulatability: Usually there are some gaps between what the physical system is and what a simulator can simulate. Therefore one has to derive a suitable model to simulate. Some reasonable approximations should be expected in the derived model.

2. Suitability: In general any dynamic simulator is only suitable for a range of problems, although some of them are claimed to be general purpose simulators. For example, some simulators are better for linked structure, while some others are better for free body system. One good example for this is the impulse-based versus the constraint-based simulator.

3. Efficiency: Given a simulator and a MEMS structure to simulate, one may be able to build several simulation models that are all consistent with the true physical model. However among those, some are much more computationally efficient than others.

4. Scale: It is often that the true parameters are not in the suitable range of the simulator, one has to scale them consistently.

To build a simulatable, suitable, efficient simulation of the right scale, one needs insight about the problem itself as well as the simulator in hand.

In this report, the simulation of the linear electrostatic stepper motor [8] is presented as an example to address the above issues. We summarize the physical model of a linear electrostatic stepper motor in section 2. We present the simulation of the stepper motor using Impulse [5][4] in section 3 and the experimental result in section 4. We discuss the limitation of the simulation and possible extensions in section 5.