Application Research Of The Multi-Model Adaptive Control To Microwave Lignite Drying

There are plentiful reserves of lignite(a kind of low rank coals) in China. However, direct use of lignite is of low thermal efficiency and serious pollution, due to some own characteristics, such as high moisture content and low heating efficiency. Microwave, a new high efficient and clean energy, has a great many of advantages: integrity, selectivity, safety,healthy, pollution-free, real-time and high energy efficiency, etc. At the same time, microwave heating technology has become a new type of high efficient industrial heating method. In the process of using microwave drying, some heating characters of lignite, such as dielectric constant, change with the altering of environment. It may appear the phenomenon of thermal runaway, greatly restrict the industrial application of microwave drying. Therefore, the multiple model adaptive control algorithm is introduced into the microwave lignite drying process in this paper,to achieve effective control of temperature in the process and ensure the security of the drying process.Controlled object is experimental system of microwave lignite drying. Input power and lignite temperature of system are selected as input and output. With the consideration that the control volume is with nonlinear input constraints, the effectiveness of multiple model adaptive control to control lignite temperature of the microwave lignite drying system and ensure the system safe and efficient operation is study in this paper. Main research contents of this paper is as follows:(1) Analysising the factors that affects the changing of dielectric coefficient of lignite.Identifying microwave lignite drying process system with least squares method uses the input and output data of system, and establishing the identification model of microwave lignite drying process.(2) Controllers are designed to use pole placement method and adaptive control pole placement method based on the identified model of microwave lignite drying system with disturbance, jumping parameters and constrained input. Then we verify the effectiveness of control in different situations.(3)In the presence of mutation or change of lignite parameters, multiple model adaptive control algorithm is used to control the microwave lignite drying process. Based on the identification of microwave drying lignite experimental data, we select 48 identification models,a conventional adaptive model, and an adaptive model with varying initial value as models library, With the condition of using nonlinear input constraints, we use multiple model adaptive algorithm to control the output temperature of the system. Finally, we verify the control effect of microwave lignite drying system based multiple-model adaptive control algorithm by the simulation results and microwave lignite drying experiment.