Sensing armature motion in high-speed solenoids

Abstract

The invention relates to a technique for discerning a status of an armature of a high-speed solenoid at any time during its operational cycle. In high speed solenoids, motion of an armature does not occur until after a finite and indeterminate lapse of time after application of a driving voltage. In the present invention, a pulsed driving voltage is used to drive the solenoid. A resultant current in a coil of the solenoid exhibits discontinuities in its rate of change when the armature moves. Occurrences of the discontinuities are used to produce control signals and coordinate operation of the solenoids and other controllable events. Occurrence of these discontinuities exactly correlates with armature motion. Consequently, time lapse between application of voltage and motion of the armature becomes inconsequential in design of a control system. In other words, control and coordination of operation of high-speed solenoids can be performed without consideration of uncertainties of the time lapse. In an exemplary illustration, the invention is applied to controlling speed of a turbine generator of a type used in space vehicles. High-speed solenoids are used to control bursts of hydrogen and oxygen flow into a combustion chamber of the turbine generator. Speed control is maintained by controlling a rate and duration of the bursts.