Abstract: A method includes identifying a magnitude and phase angle of vibration forces resulting from a previous cancellation signal, where a first measured force vector is defined by this magnitude and phase angle. The method also includes identifying a magnitude and phase angle of a first cancellation force and transmitting a first AFF cancellation signal configured to generate the first cancellation force, where a first cancellation force vector is defined by this magnitude and phase angle. The method further includes identifying a magnitude and phase angle of vibration forces resulting from the first AFF cancellation signal, where a first resultant force vector is defined by this magnitude and phase angle. Moreover, the method includes determining whether a phase angle difference between the phase angles of the first resultant force vector and the first measured force vector is substantially equal to zero. If so, the method includes continuing to transmit the first AFF cancellation signal.

Abstract: A system includes a multi-stage cryocooler having multiple stages and a temperature control system configured to regulate temperatures of the multiple stages of the multi-stage cryocooler. The temperature control system includes an input interface configured to receive (i) temperature setpoints for the stages of the multi-stage cryocooler and (ii) temperature information corresponding to temperatures measured at the stages of the multi-stage cryocooler. The temperature control system also includes processing circuitry configured to determine temperature errors and calculate at least one of a compressor stroke error and a pressure-volume phase error. The temperature control system further includes at least one controller configured to adjust at least one of a compressor setting and a pressure-volume phase of the multi-stage cryocooler.

Abstract: A method includes identifying a magnitude and phase angle of vibration forces resulting from a previous cancellation signal, where a first measured force vector is defined by this magnitude and phase angle. The method also includes identifying a magnitude and phase angle of a first cancellation force and transmitting a first AFF cancellation signal configured to generate the first cancellation force, where a first cancellation force vector is defined by this magnitude and phase angle. The method further includes identifying a magnitude and phase angle of vibration forces resulting from the first AFF cancellation signal, where a first resultant force vector is defined by this magnitude and phase angle. Moreover, the method includes determining whether a phase angle difference between the phase angles of the first resultant force vector and the first measured force vector is substantially equal to zero. If so, the method includes continuing to transmit the first AFF cancellation signal.

Abstract: A system includes a multi-stage cryocooler having multiple stages and a temperature control system configured to regulate temperatures of the multiple stages of the multi-stage cryocooler. The temperature control system includes an input interface configured to receive (i) temperature setpoints for the stages of the multi-stage cryocooler and (ii) temperature information corresponding to temperatures measured at the stages of the multi-stage cryocooler. The temperature control system also includes processing circuitry configured to determine temperature errors and calculate at least one of a compressor stroke error and a pressure-volume phase error. The temperature control system further includes at least one controller configured to adjust at least one of a compressor setting and a pressure-volume phase of the multi-stage cryocooler.

Abstract: Disclosed are a low vibration cryocooler and a method of reducing vibration in a cryocooler. The cryocooler can be a Stirling class cryocooler includes at least one motor that drives a mass, the motor having a main drive winding and a separate trim winding. A motor controller outputs a main drive signal that is coupled to the main drive winding and a separate vibration reducing signal that is coupled to the trim winding.

Abstract: A system and method for sensing position of an oscillating moving element. The inventive position sensor includes a first arrangement for sampling the position of the element at first positions thereof and providing samples in response thereto and a second arrangement for calculating other positions of the element using the sample of the first position. In the illustrative application, the first arrangement includes an LED and a photodiode and the moving element is a piston of a long-life cryogenic cooler. A processor receives samples from the photodiode and solves an equation of motion therefor. The equation of motion is P(t)=A·sin(?t+?)+B, where P(t)=the position of the element; A=position waveform amplitude; B=position waveform DC Offset; ?=angular frequency of operation; t=time; and ?=position waveform phase.

Abstract: A system and method for sensing position of an oscillating moving element. The inventive position sensor includes a first arrangement for sampling the position of the element at first positions thereof and providing samples in response thereto and a second arrangement for calculating other positions of the element using the sample of the first position. In the illustrative application, the first arrangement includes an LED and a photodiode and the moving element is a piston of a long-life cryogenic cooler. A processor receives samples from the photodiode and solves an equation of motion therefor. The equation of motion is P(t)=A·sin(?t+?)+B, where P(t)=the position of the element; A=position waveform amplitude; B=position waveform DC Offset; ?=angular frequency of operation; t=time; and ?=position waveform phase.

Abstract: An adaptive feedforward vibration control system reduces vibrations at fundamental and harmonic frequencies of matched reciprocating pistons, such as back-to-back compressor pistons in Stirling cycle cryocooler, by driving the pistons with correction signals. The system is also applicable to reducing the vibrations generated by a pair of opposite expander and balancer pistons in a cryocooler. The correction signals are computed iteratively to increase their accuracy, and need only be updated relatively infrequently to adjust the pistons' motions, thereby enabling the use of a relatively slow microprocessor.

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.