Design And Implementation Of Thermostatic Control Strategy For Chashan Broadband Solar Millimeter Spectrometer(35-40 GHz)

Temperature stability is an important factor affecting the operating stability of the receiver in solar radio equipment.The fluctuation of temperature can lead to the fluctuation of the output voltage and the overall gain of the receiver.Therefore,in order to ensure the working stability of the receiver and improve the accuracy of the measured data,it is necessary to design a highprecision thermostatic control system suitable for the radiometer receiver.In this paper,a highprecision temperature control system is developed to satisfy the temperature stability requirements of Chashan Broadband Solar radio spectrograph at millimeter wavelength(CBS,35-40 GHz)in Chashan Solar Observatory(CSO)developed by the Laboratory for ElectromAgnetic Detection(LEAD)of the Institute of Space Science,Shandong University.The essential contents in the development,including chassis structure analysis,control algorithm design,hardware platform construction and overall scheme verification,are studied.Compared with the traditional temperature control systems,this miniaturized and lightweighted system can realize precise temperature control,with a fluctuation of 0.02℃.The main research contents are as follows:(1)The whole process scheme of the solar radio receiver chassis constant temperature system is first designed.Accoding to the working principle of Thermoelectric Cooler(TEC),we find that at least two TECs are needed to meet the cooling requirements.As the key performance,the thermal conductivity performance of the thermal conductivity plate is analyzed and tested to optimize the overall heat conduction and heat dissipation of the chassis.Finally,the test results of a single TEC experimental box show that the designed structure has a fast heat conduction speed and good effect.(2)The hardware platform of temperature control system of solar radio receiver is designed.The system is composed of three modules,i.e.the temperature acquisition module,the numerical control module and the driving module.The temperature acquisition module selects a platinum resistance temperature sensor with the precision of 0.01 ℃ to ensure the temperature control accuracy.The STM32H743 chip is selected as the core processor in the numerical control module.In the driving module,accoding to the comparison of the designed H-bridge and relay drive circuit,the relay circuit is used as the drive module of TEC for its lower energy loss and stable control effect.The hardware platform transmits data with the computer through the serial port.And the target temperature can be set,and the control results can be displayed on the host computer.(3)The constant temperature control algorithm of solar radio receiver is developed.Comparing with the PI control algorithm,the PID algorithm can realize smaller overshoot in temperature control and therefore is selected in the system design.Furthermore,considering the idealized assumptions made during the system model construction,the fuzzy PID control algorithm is designed.During the control at 10℃ temperature debugging,the algorithm can realize a stability time less than 1 minute and an overshoot below 0.7℃.(4)The temperature control system is tested in the CBS(35-40 GHz band).The performance of the thermostatic control system is tested and the results are as follows:the overshoot of less than 0.25℃,the temperature control precision of 0.02℃,the temperature fluctuation of within the range of set value ±0.10 ℃ after stabilization,and the RMSE is less than 0.025.These results show that the temperature control system meets the requirements and design expectations of the project,and the scheme and design in this paper are feasible.The temperature control system is designed with high-precision platinum resistor and microcontroller to develop the core temperature control circuit.Accoding to the temperature control strategy combining semiconductor refrigeration principle,the fuzzy PID control algorithm is used to achieve high-precision stable control of the temperature of CBS receiver box.The system has the characteristics of miniaturization,lightweight,simple operation,high temperature control accuracy,and provides a reference for the subsequent research on temperature control in the field of radio astronomy.