Harmonic force of linear motor acts directly on the drive element
which reduces the motion stability of the feed system. The servo drive circuit and the nonlinear of motor structure are considering. With the equivalent magnetizing current method and Maxwell equations
the analytic expression of ripple force
cogging force
end effect force
coupling force and inductance asymmetry force are obtained. In the computation process
the coupling effect between multiple harmonic factor is considered
which makes up for the former single factor analysis of harmonic force. The results show that the thrust in the linear motor contains multiple harmonic force
influenced by the servo drive circuit and the nonlinear of motor structure
and each harmonic component gets mutually coupled. These harmonic force acts directly on the mechanical system to lead to the displacement wave of feed system. The effect of the harmonic force rises with the increasing speed. Near the speed of 5
20 and 33 m/min
the harmonic force results in system resonance to seriously weaken motion stability of the feed system. The amplitude of ripple force declines with the decreasing amplitude of the harmonic current. The ratio between pole pitch and tooth space pitch and ratio between tooth space opening and pitch exert an important influence on the harmonic frequency and amplitude of cogging force
especially
the cogging force disappears in the ratio of tooth space opening and pitch of 0.625.
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references
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