Research On High Stability Multistage Temperature Control Technology Of Mechanical Cryocooler

With the further exploration of space detection technology in China,the performance requirements of infrared detection technology are getting higher and higher.Taking the infrared reference load in the field of climate change research as an example,it is required that the temperature change recognized by the infrared reference load is less than 1K per hundred years at present,so the infrared reference load developed must be characterized by high sensitivity,spectral continuity and spectral resolution.The infrared reference load is very sensitive to the small change of the cold head temperature of the cryocooler,so the small change of the cold head temperature will affect the performance requirements of the infrared reference load.Mechanical cryocooler generally adopts active closed-loop temperature control mode,that is,PID control operation is carried out on the temperature deviation value of the cold head,and the cooling power is output according to the control value calculated by the PID controller to adjust the temperature of the cold head,so as to keep the temperature of the cold platform stable.However,the temperature stability of the cryocooler only using the active closed-loop temperature control mode cannot meet the requirements of high-performance infrared the detector for the temperature stability of the cold head at present.Therefore,how to improve the temperature stability of the cold head of the mechanical cryocooler has become a difficult problem that needs to be solved at present.In view of these problems,this paper studies the mechanical cryocooler to achieve high stability temperature control technology in the following aspects:Firstly,the working principle of Stirling type pulse tube cryocooler is introduced.The mathematical model of multi-stage temperature control system is extracted from the coupling system of pulse tube cryocooler and infrared reference load,and the comprehensive transfer function of multi-stage temperature control system is obtained.Secondly,according to the comprehensive transfer function,the multi-stage temperature control strategy of the cryocooler is proposed: on the basis of the temperature control of the cryocooler shell and the cryocooler 's active closed-loop temperature control,the precision compensation temperature control device is supplemented to output small heating to adjust the tiny temperature fluctuation of the cold head.Thirdly,according to the cryocooler multistage refrigerator temperature control strategy multi-stage temperature control system is established.By comparing The characteristics of position and increment PID control algorithm and PID parameter setting method,the multi-stage temperature control system of mechanical cryocooler uses incremental PID control algorithm to adjust the temperature of the cold head and adopts PID parameter setting method based on stability margin to determine the multi-stage temperature control parameters,and the effect of thermal load change on the system stability performance is analyzed.Then,the coupling system of the cryocooler,the integrated multi-stage temperature control algorithm and the control circuit is integrated into modeling and simulation,and the initial value of the temperature control parameters of the integrated multi-stage temperature control system is obtained.On this basis,the stability margin analysis of the temperature control parameters is carried out and the temperature control parameters are reset.Finally,the multi-stage temperature control strategy of the cryocooler and the multi-stage temperature control system were verified through experiments,and the temperature control parameters of the multi-stage temperature control system of the cryocooler were modified.Finally,the temperature stability of the multi-stage temperature control system of the mechanical cryocooler was ±10mK/30 min.