Development of a Linearly Responsive Electromagnetic Actuator

Abstract

A novel electromagnetic actuator is reported in this paper. The device can be used as a precision position provider, as the movement of the free solenoid responds linearly to the input electric current. Such a linear relationship can make it very easy to control the device, with a simple open-loop control scheme. The novel actuator comprises of two solenoids and an elastomeric cone, sandwiched in between the solenoids. The elastomeric cone provides non-linear reaction force in resistance to the electromagnetic force, and as a result, force equilibrium can be achieved at the desired working points to form a straight line of position response versus input current. Finite element analysis was used for accurate calculation of the highly non-linear spring characteristics of the elastomeric cone. Among the geometries studied, it was found that a cone shape of 6mm in height, 7mm in diameter, and an aperture of 57 o produces a force-displacement curve that best suits the need for the spring performance. A prototype of the actuator, along with the elastomeric cone was made and tested. The results showed that the movement of the actuator responds to the input current quite linearly, with an R 2 of 0.983.