Affiliations: [a] The State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China | [b] Qiushi College, Tianjin University, Tianjin, China
Abstract: This paper considers the pull-in of electromagnetic
actuator with permanent magnet for the first time. The pull-in mechanism of
electromagnetic actuator is explained from the perspective of system
stiffness. Pull-in is about to occur when system stiffness becomes null.
Based on the system stiffness analysis method, the pull-in parameters of an
E-core electromagnetic actuator with permanent magnet are derived. Then, the
effects of the permanent magnet on the derived pull-in parameters are
studied. The analysis results show that the permanent magnet enlarges the
pull-in displacement for its reluctance. If the permanent magnet length is
more than three times as large as the initial displacement, pull-in would
not occur. The effects of the permanent magnet on the pull-in current are
complicated, especially the effects of the permanent magnet length. A method
based on analyzing the roots of two properly defined equations is introduced
to study the effects of the permanent magnet length on the pull-in current.
The method is effective and simplifies the complicated analysis. Finally,
numerical simulations are presented to validate the pull-in model and
analysis methods in this paper. It is shown that the theoretical results are
in a good agreement with the simulation results.
Keywords: Pull-in, permanent magnet, electromagnetic actuator, system stiffness
