Resonant piston compressor having improved stroke control for

Abstract

A method and apparatus for controlling a resonant piston compressor of the type comprising an electrodynamic linear reciprocating motor adapted to be driven cyclically by an alternating current power source and having at least one piston coupled to and adapted to be driven within a selectively valved working cylinder by the linear reciprocating motor in synchronism with the frequency of the alternating current power source. Enclosed volumes of gas act as resilient gas springs coacting with the piston and with the linear reciprocating motor to form a mechanical resonant system having a resonant frequency substantially centered on the frequency of the alternating current power source. A midstroke porting arrangement is responsive to the position of the resonant piston for selectively communicating a gas spring control valve with said gas springs. The invention operates to variably control with the gas spring control valve the pressure of the gas in the gas springs to thereby dynamically modulate the stiffness of the resilient gas spring in a manner to control the stroke of the resonant piston compressor within predetermined safe limits. The method and apparatus further include sensing a plurality of different operating parameters of the resonant piston compressor and deriving output sensed signals representative of the respective parameters, combining the sensed parameter output signals to derive therefrom an output control signal and applying the output control signal to the gas spring control valve to variably control the opening and closing of the gas spring control valve.