System and methods for vibration control

Abstract

A system for vibration control of a cryocooler that cools an imager. The system includes a vibration sensor that is physically affixed to the cryocooler. The vibration sensor senses a physical vibration of the cryocooler and to generates a vibration signal therefrom. The system also includes cryocooler drive electronics operatively coupled to the vibration sensor and the cryocooler. The cryocooler drive electronics output a drive waveform that drives the cryocooler so as to reduce the vibration impact of the cryocooler. The harmonic content of the cryocooler drive waveform is controlled by the cryocooler drive electronics based on the vibration signal.

1 . A system for vibration control, the system comprising:
 a cryocooler configured to cool an imager based on a drive waveform;   a vibration sensor physically affixed to the cryocooler, the vibration sensor configured to sense a physical vibration of the cryocooler and to generate a vibration signal therefrom; and   cryocooler drive electronics operatively coupled to the vibration sensor and the cryocooler, the cryocooler drive electronics configured to output the drive waveform to drive the cryocooler so as to reduce the vibration impact of the cryocooler,   wherein the harmonic content of the cryocooler drive waveform is controlled based on the vibration signal, and   wherein the cryocooler drive electronics include a controller configured to determine the drive waveform by executing the following sequence entirely within the controller:
 (a) set a start point for each harmonic to a neutral point, 
 (b) for a current harmonic, generate a phase-amplitude matrix based on an initial start point, an amplitude step size and a phase step size, wherein the phase-amplitude matrix consists of a plurality of phase-amplitude points, each corresponding to a phase-amplitude measurement indicated by the vibration signal, 
 (c) determine which of the phase-amplitude points has the lowest vibration signal level based on sampling the phase-amplitude matrix from the start point, 
 (d) set the start point for the current harmonic to the phase-amplitude points having the lowest vibration signal level, 
 (e) reduce the amplitude step size and the phase step size, 
 (f) increase the current harmonic number and return to (b) until the current harmonic is greater than a specified maximum harmonic, and 
 (g) execute a dithering routine having a preset dithering step size. 
   
     
     
         2 . The system of  claim 1 , wherein the imager is a focal plane array imager. 
     
     
         3 . The system of  claim 1 , wherein the cryocooler is configured to cool electronics associated with the imager. 
     
     
         4 . The system of  claim 1 , wherein the cryocooler includes a cold head and a compressor. 
     
     
         5 . The system of  claim 1 , wherein the controller includes at least one field-programmable-gate array. 
     
     
         6 . The system of  claim 1 , wherein the cryocooler drive electronics are configured to operate the cryocooler to cool the imager in accordance with a temperature control process. 
     
     
         7 . The system of  claim 1 , wherein the cryocooler includes a compressor, and the drive waveform drives the compressor. 
     
     
         8 . The system of  claim 1 , wherein the cryocooler drive electronics are configured to discrete Fourier transform the vibration signal according to a specified harmonic number.