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Battershell, Minder, Wachtveitl
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Magnetic Actuator modeling in 2D Ansoft Maxwell
Jon Battershell, Spencer Minder., and Zachary Wachtveitl
Abstract— Our project was to model the Magnetic Actuator described in section 6.5 of Senturia’s Microsystem Design[1]. We
modeled the system in Ansoft Maxwell to allow us to perform a force analysis of the magnetic field on the armature. The first
experiment conducted was to apply 1 A of current to the coil around the core of the actuator and examine the forces acting on the
armature over a total displacement of 10µm. After the initial experiment, two different spring constants were chosen to be
hypothetically modeled in the system. With these spring constants, we examined the amount of current and force required to move the
armature over the same total displacement of 10µm. In addition, the B fields and B vector lines within the system were examined at
different points along the armatures path through the gap. After we tested and verified our model, we produced graphical analysis of
our results and compared the experimental results versus the theoretical equations from the textbook.
Index Terms— Ansoft Maxwell, Magnetic Actuator, Magnetic Flux Density, MEMS
I. INTRODUCTION
T
HE principles behind energy conserving transducers in MEMS can be used in many different applications. The uses range from
piezoresistive sensors to electrostatic and magnetostatic actuators. These types of transducers can be useful in wireless
technology, automotive and biomedical fields as well. For our purposes, we chose to model a magnetic actuator. We chose this
type of actuator because we had already worked with electrostatic actuators and wanted to try a different energy domain. After
modeling the magnetic actuator, we wanted to compare the differences from electromechanical to magnetomechanical designs.
We chose to model the system Ansoft Maxwell 2D MEMS software package. This type of software is great for modeling
electrostatic or magnetostatic components of MEMS type devices that are relatively simple. It provides an easy user interface,
quick setup and small learning curve. The downfalls are that it is relatively limited in the types of solvers that can be used.
Only one type of domain can be analyzed at a time such as electrical, in the form of electrostatics, or magnetic, in the form of
magnetostatics. A more robust MEMS software could provide a multiphysics based solution using a magnetomechanical
solver. This would allow for modeling the entire magnetic actuator system. However, these sophisticated software packages
have a much steeper learning curve and were not feasible in the time allowed. Two experiments were conducted using Maxwell.
The first experiment was to look at the forces applied to the armature as it traversed the gap. The second experiment used two
different assumed spring constants and looked at the current required to move the armature through the gap. Both experiments
assumed the armature started at the same initial displacement and travelled the same total displacement.
The main focus of this paper is to compare the experimental results of these modeled experiments in Ansoft Maxwell to
the theoretical results derived in section 6.5 of the textbook Microsystem Design[1].
II. MODEL DEFINITION AND DESCRIPTION
The magnetic behavior of the magnetic actuator was modeled in Ansoft Maxwell 2D. The model was designed as a flat
structure in the xy plane since the actuator isn’t axisymmetric. It was designed using a micrometer scale as this actuator was
intended to be in a MEMS device. The model consists of the three necessary magnetic components of a magnetic actuator: the
core, the coil, and the armature, see Figure 1. The core is the blue rectangular shape shown in Figure 1. The core is designed to
have a gap for the armature to pass freely through. The gap is designed to be slightly larger than the width of the armature. To be
a magnetic actuator the core must be able to support the formation of a magnetic field within itself. Therefore, the core must be
use a material with a relatively large permeability. For this design, iron was the chosen material.
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