Study On Temperature Control Of Microwave Heating Process Based On Model-free Adaptive Control

Microwave heating technique is an efficient way that is capable of generating thermal energy through the direct interaction between the heated medium and microwave. Comparing to the traditional heating method, microwave heating has some advantages, such as shorter processing time, higher temperature homogeneity, its selective heating and no pollution. The interaction between the complex time-varying electromagnetic field and temperature field are involved in the microwave heating process. The local overheating and thermal runaway phenomenon may also occur in this heating process. And the controlled planted in this heating process has characteristics of nonlinear, coupling, time-varying and uncertainty. Further, the actuator has the physical constraints and the sensor has characteristics of time-delay. So it is of big difficulty and challenge to build up the accurate model of the microwave heating system. In order to realize the heated medium temperature control in microwave heating process, and ensure the safe and efficient operation of the controlled system, model-free adaptive control algorithm based on the medium temperature characteristic and limited real-time feedback data has been applied. The stability and effectiveness of model free adaptive control algorithm with nonlinear constraint and time-delay characteristics are studied in order to achieve the tracking temperature control of the heated medium through the real-time adjustment of the output power of microwave source. The main research contents of this thesis as follows:Firstly, the development status of the medium temperature control in microwave heating process and the model-free adaptive control algorithm is analyzed. Based on simplified mathematical model of microwave heating system, the model free adaptive control algorithm with constraints is designed and its stability was verified through theoretical analysis and simulation.Secondly, to reduce the influence of nonlinear input constraints and time-delay characteristics on the medium temperature control, novel model free adaptive control algorithm is designed and its stability is verified through theoretical analysis and simulation.Finally, to facilitate the realization and extension of control algorithms for microwave heating system, its software control interface is designed. To improve the temperature control effect, the existing problems in microwave heating experiment control system are analyzed by using the off-line experimental data and the corresponding solutions are proposed to assist in realizing temperature control of microwave heating system.