Modeling Of Liquid Level Control System And Study Of Its Control Algorithms

Liquid level not only is a familiar variable in the field of industry process, but also it is easy to observe and to measure directly in process control. Liquid level process can constitute experiment system, can vividly carry on process combination and carry out various different control projects, such as SISO subjects of first-order, second-order, third-order and nonlinear two inputs and two outputs subjects. Liquid level control system is a importance research model and its research has important theoretical and actual meaning in process control.An equipment, which is called three-tank water control system, is designed as a process control experiment device in order to satisfy the need of Control Theory & Engineering laboratory construction. The thesis will further perfect software and hardware facilities construction of experiment system, give some advice and measure to improve and enforce the system actual value, and make experiment equipments apply in experiment teaching better.The thesis introduces the hardware structure, the work principle of various objects and the characteristic of the components of the independent designed three-tank liquid level control system as a whole. The thesis also gives a real setting scheme. Following this,after the thesis discussion and nonlinear analysis of the input water valve and the leak valve in detail, it gives several linear equations and a nonlinear compensation algorithm which is used in the application and gives models of the components of the device. Then the thesis finishes building models of various objects and identifying model parameters in system in the method of the step response and the least squares.Considering the three-tank liquid level control system as the research object, the thesis discusses and studies a few kind of control algorithms, including: PID control algorithm, integral separation PID control algorithm, Dahlin control algorithm, Smith predictor control algorithm, fuzzy and fuzzy-PID control algorithm. At the same time the paper accomplishes these algorithms by programming with C and simulating with Matlab, according to the comparison results of experiment, it comes to a conclusion on the possibility and superiority of the control algorithms.