Abstract: A temperature control apparatus and method for active control of a Stirling-cycle cryocooler cold finger tip temperature, by adjusting the cryocooler compressor piston stroke amplitude. In a control loop of the Stirling cryocooler, having a compressor in which the pistons are reciprocated by linear motors at fundamental frequency and the length of a stroke of the piston is varied as a direct function of cryocooler temperature, temperature is sensed at the cryocooler cold finger tip and the temperature signal is compared with a set temperature signal to produce a temperature error signal. This signal is input in a PID control law module which uses proportional, derivative, and integrated temperature error information to generate the required compressor piston stroke amplitude change for achieving the precision temperature control.

Abstract: A cryogenic cooling system having a mechanism for canceling vibration at a fundamental frequency and at harmonics thereof. The inventive system includes a first apparatus (28, 32) for cooling a mass. The first apparatus (28, 32) creates a vibration at a first frequency and a second frequency. In a typical application, the first frequency is a fundamental frequency and the second frequency is a harmonic of the first frequency. Often several harmonics are present. The invention includes a second apparatus (30, 34) for substantially eliminating vibration at the first frequency and a third apparatus (48, 50) for substantially eliminating vibration at the second frequency. The second apparatus includes a mass (30) and a motor (34) for driving same. The mass (30) is disposed to counter the vibration created by the first apparatus when the motor (34) is driven by a first current.

Abstract: A Stirling-cycle cryogenic cooler that employs a vibration control procedure based on adaptive feedforward principles. The vibration control procedure is particularly adapted for use as a spacecraft cryogenic cooler, and may be used to cool a detector array or other sensor located on the spacecraft. The vibration control procedure suppresses vibrational forces that occur during operation of the cooler. The cooler comprises an expander module and a compressor module. The expander and compressor modules employ separate motors that respectively drive an expander piston and a compressor piston, and a balancer piston is employed to dynamically balance the respective expander and compressor pistons. In the control procedure, current command signals are injected into a selected motor drive of either the compressor or expander module. The injected current command signals comprise higher-order harmonics with adaptively determined phases and amplitudes that provide for complete force cancellation in the cooler.