A Variable Stiffness Methodology to Extend Travel Range of Microelectromagnetic Actuators

Short controllable travel due to pull-in instability limits some engineering applications of microelectromagnetic systems electromagnetic actuators. This letter presents a variable stiffness methodology to optimize the motion path for the movable armature. The nonlinearly increasing spring force versus the air gap partially offsets the nonlinearity of the electromagnetic force, contributing to a backward shift in the position of the instability point. Also, the relatively low actuator's stiffness compared to conventional linear spring can reduce the driving current. Theoretical calculations prove that this method effectively improves the controllable travel range while reducing the pull-in current and response time.