The Development Of High Precision Low Temperature Generation System Based On Multistage Thermoelectric Coolers

With the deep research in the fields of petrochemical,aeronautics,biological medicine and other fields,the related instrument temperature control system requires higher temperature control precision and wider low temperature range.The multistage thermoelectric coolers(multistage-TEC)has wide application prospects in the instrument temperature generation system due to its advantages of large temperature difference,small thermal inertia,convenient lifting temperature switching and so on.This paper took multistage-TEC as the object,and researched the high-precision low temperature generation system from the aspects of overall design,model calculation and temperature control algorithm.Firstly,this paper combined with the application of low temperature characteristic analyzer,select the three stage thermoelectric coolers as the cooling/ heating source,put forward the heat dissipation way of compressor auxiliary hot sink cooling,and designed temperature control object and temperature generation system.After analysing the relationship between the different parameters in the multistage-TEC and calculating the heat loss,this paper established the dynamic model and the steady state parameter prediction model of the multistage-TEC,and affirmed the accuracy of the model by experiments.The parameters of the compressor are determined according to the results of the calculation.Secondly,combined with the nonlinear and time-varying characteristics of multistage-TEC,designed positional integral anti saturation variable speed integral PID as temperature control strategy,and analysed its parameter setting method.Furthermore,designed incremental variable gain single neuron PID as temperature rise or drop rate control strategy,and used genetic algorithm to solve local minimum defect caused by different initial values in single neuron PID.Finally,set up the high precision low temperature generation system,and calibrated the thermocouple measurement system.The experimental results of evaluating the temperature measurement,temperature limit and temperature control performance show that the accuracy of the thermocouple temperature measurement is better than 0.025?,the limit of temperature range is higher than 70? and lower than-70?,temperature rate range meet the-10?/min~10?/min,the temperature control accuracy is 0.03?,and the control accuracy of temperature rise or drop rate is better than 0.07?/min.