A Model For The Pull-in Parameters Of Torsional Magnetostatic Actuators With Fringing Effect

In contrast to electrostatic actuators, magnetostatic microactuators have some particular advantages, magnetostatic microactuators may be more capable of producing large force or torque; the driving voltages are compatible with IC; magnetostatic microactuators may operation in dust-filled or conducting fluid-filled environment; magnetostatic microactuators can generate repulsive forces in addition to attractive forces. As a result, MEMS magnetostatic actuators are drawing much attention. The Pull-in Parametes are critical to magnetostatic actuators. The model for the Pull-in parameters of magentostatic actuators is not accurate in some cases, such as the actuator is so small that fringing effect can not be ignored. It is necessary to do some in-depth studies about the model for the Pull-in parameters of magnetostatic actuators. In the case of considering fringing effect, we study Pull-in phenomenon of the MMF-controlled parallel magnetostatic actuator with a liner displacement and MMF-controlled torsion actuator.(1). The finite element method is an effective method to solve engineering problems. In this thesis, the finite element method is introduced. Then, the various modules of ANSYS are introduced. A flow diagram to simulate by finite element method is presented.(2). Take the MMF-controlled parallel magnetostatic actuator with a liner displacement as a example, the Pull-in phenomenon is analyzed. Because the initial gap decreases, the magnetic force increases much faster than linear spring force. At a critical gap, the stability of equilibrium is broken, and Pull-in occurs. In addition,"energy method"is introduced. For the MMF-controlled parallel magnetostatic actuator with a liner displacement, a leakage reluctance model is given. On this basis, a model for the Pull-in parameters with fringing effect is derived. It is shown that the Pull-in parameters derived from leakage reluctance coincide with FEM results well in a wide range of size. But, in some size, the tolerance becomes lager when leakage is ignored.(3). The phenomenon of a magnetic microactuator with a multilevel meander magnetic core is discussed. A leakage reluctance model with more accuracy is derived. On this basis, a model for the Pull-in parameters with fringing effect is presented. The analytical results considering leakage and ignoring leakage are respectively to be compared with FEM results. The tolerance in different size is analyzed.