Linear Position Control Using Simple Solenoids and an Electromagnet

Simple solenoid plunger type electromagnets are commonly used in devices such as switches, relays, and solenoid valves (to name but a few). In most cases these are on/off applications where the plunger is moved from one extreme position (when turned on) to another (when turned off). In this paper a scheme is presented to enable positioning of a linear actuator based on two simple solenoids, a flat faced electromagnet, and a microprocessor. The paper describes the configuration and performance of such a system which uses pulsed signals from a microprocessor to activate the solenoids and the electromagnet. The plungers connected by a shaft in a push pull arrangement move in an axial direction while an electromagnet orthogonal to the shaft latches it at a desired position. An algorithm to control the input pulses to the solenoids and the electromagnet is developed and experimental results using this control scheme are presented.