Overview
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Coreless linear actuators are used for the head drive of electronic packaging
machines and precision stages, both of which require high accuracy positioning.
Static thrust has a great effect on accurate positioning, since it varies
with the translation position of an actuator. Also, static thrust varies
with the amount of current, so it is important to obtain the static thrust
at each supply current from the analysis. This note presents the use of
magnetic field analysis to obtain static thrust characteristics of a voice
coil motor at different translation positions and different supply currents.
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Static Thrust at Different Translation Positions
| Figure 1 shows the static thrust at different translation positions when
the supply current is 0.05 A. Figure 2 shows the Lorentz force density
distribution of the coil at the translation position of 0 and 1 mm. In
Figure 1, the static thrust is maximized at the translation position of
1 mm where the coil is directly beneath each pole. As shown in Figure 2,
the Lorentz force density at the translation position of 0 mm is smaller
in the circle area compared with the translation position of 1 mm. In addition,
the magnetic field at the translation position of 0 mm is smaller in the
circle area. |
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Magnetic Field Distribution
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Figure 3 shows the magnetic field distribution at the translation position
of 0 and 1 mm. The magnetic field at the translation position of 0 mm is
weaker in the circle area, and also the direction of the magnetic field
is not perpendicular to the translation direction. Since the direction
and amount of the current flowing in the coil are constant, the static
force (Lorentz force) is determined by the strength and direction of the
magnetic field. So, the static force becomes smaller due to the magnetic
field distribution of the coil. |
Static Thrust at Different Supply Currents
| Figure 4 shows the static thrust at different supply currents. Static thrust
increases linearly with the increase of supply current. The thrust constant
is 6 N/A according to the slope of the graph. it is certain that the static
thrust can be controlled by the amount of supply current. |
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