Research On Temperature Control System Of Thermoacoustic Motor Based On Model Prediction

With the continuous improvement of the requirements for low-temperature refrigeration technology in military,medical and commercial fields,the traditional refrigeration mode based on steam compression is facing a series of technical problems such as insufficient refrigeration capacity,low efficiency,poor reliability and environmental pollution.In recent years the lowtemperature Stirling cryocooler based on closed cycle has developed rapidly due to its advantages of high efficiency,long life,wide refrigeration temperature range and green environmental protection.In particular,the free piston Stirling cryocooler has the characteristics of compact structure,low noise and high reliability,and has broad application prospects.The research object of this subject is the 1k W free piston Stirling cryocooler driven by singlephase linear motor designed and manufactured by Jiangsu Thermoacoustic Electromechanical Technology Co.,Ltd.Its series products are also known as "Thermoacoustic Cryocooler".Based on PIC30 F series chips of microchip company,the driving controller of the Thermoacoustic Cryocooler is designed in this thesis to realize the safe and stable operation of cryocooler and the accurate control of cold end temperature during operation.The controller has good commercial potential.In terms of controller hardware,the power part adopts single-phase H full bridge inverter circuit to output AC to control the reciprocating motion of linear compressor.The driving circuit adopts DC-DC isolated power supply to realize reliable driving.The sampling and conditioning circuits of voltage,current and temperature signals are designed to collect system parameters to realize accurate control.The serial port communication between computer and single chip microcomputer is carried out by using host computer software to realize command transmission.And sinusoidal pulse width modulation(SPWM)technology is used for voltage regulation.In the aspect of control algorithm,the order and specific parameters of cryocooler model are determined by mechanism method and test method respectively.In view of the time-varying model parameters in the refrigeration process of thermoacoustic motor,the recursive least square algorithm with forgetting factor is applied to the on-line parameter identification of the refrigeration process to obtain the dynamic model of the system in real time.In view of the poor control effect of PID control strategy on the refrigeration process with large inertia and long time delay,the generalized predictive control algorithm is introduced to accurately control the refrigeration process.Through MATLAB simulation,the temperature control effects of traditional PID control,improved Smith-PID control and generalized predictive control algorithm are analyzed,and the effectiveness of the method proposed in this thesis is verified by simulation.Finally,the driving control experimental platform of the Thermoacoustic Cryocooler is built based on ds PIC30F4011 main control chip to complete the performance test of auxiliary switching power supply,power circuit and driving circuit,as well as the temperature control system experiment of PI control in voltage loop and PID control and generalized predictive control in temperature loop.The experimental results show that the drive controller of the Thermoacoustic Cryocooler designed and manufactured in this thesis runs reliably.When using the generalized predictive temperature control method,it can realize fast and accurate refrigeration,the dynamic and steady-state performance of temperature response is good,and all indexes meet the design requirements.