Abstract
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Cogging in a linear machine can be described as a
variation in the magnetic forces as the machine travels
along its linear uis. This effect can have a severe impact on
the overall precision and even stability of the linear uis. In
this paper an analytical method to predict the cogging
forces in Linear Induction Moton (LIMs) is presented. An
aecurate estimation of cogging is useful during the LIM
design stage to help millimize this performance limiting
factor. One common method used to predict cogging
torques in rotary induction moton is the tooth overlap
method. Due to the complexity of slot fringing effects in
slotted cores, and the fact that fringing effects significantly
influence the accuracy of this method, many researchers
alJo use Carter and Green coefficients to increase accuracy.
However, this approach does not accurately translate to the
linear motor case. In this paper an estimation of the
magnetic flux path (based on FEM simulations) is used,
along with the gradient ofthe magnetic energy stored in the
air gap, to predict the cogging forces in an LIM. The
aecuracy of this prediction method is also verified
experimentally through a cogging force analysis on a simple
one-tooth test-bed.