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.