Research Of Modeling And Internal Model Control For Coupled-Tank System

Liquid level precision control technology has been widely used in chemical production,solution filtration,beverage processing and cosmetics manufacturing industries.Many liquid level systems can be abstracted into a tank system model.The tank system has characteristics such as time-varying,hysteresis,and non-linearity,and can well simulate some characteristics of a complex industrial level system.Therefore,it is very significant to study the advanced level control method of the water tank system and then to guide the control of the liquid level in some actual industrial systems.This project is mainly focused on the Coupled-Tank level control system produced by Canada's Quanser Company as an experimental object,and the optimization of Coupled-Tank modeling and the model-based Coupled-Tank system liquid level precise control problem are studied.In this paper,the hardware and software system of the Coupled-Tank is introduced briefly,and its basic working principle is described.Then,the mathematical model of the Coupled-Tank level control system under ideal conditions is established.Under the premise of no flowmeter,an experimental method was designed to measure the flow characteristics of the pump.It was found that there was a good linear relationship between the drive voltage of the water pump and the flow rate of the water pump,and through the fitting method according to the experimental data to determine the pump flow coefficient.Considering that the water leakage hole of the water tank is fouled or due to the influence of pressure and level height,the actual water flow shrinks when the water outlet passes through the water outlet.In the mathematical model,the correction coefficients of the outlet section of the upper tank and the lower water tank1?and2?are introduced,and the two coefficients are identified based on the experimental data using the particle swarm optimization algorithm.Experimental results show that the revised simulation system can better simulate the characteristics of the actual system.Secondly,the basic principle and implementation process of state feedback controller for Coupled-Tank level system are introduced.The gain of state feedback controller is obtained by LQR optimization method,and the influence of LQR parameters on system performance is discussed in detail.Finally,for the disadvantages of the steady-state performance and poor anti-interference ability of the simple state feedback control,the internal model control method of the Coupled-Tank is proposed.In addition to the state variable feedback,the designed controller also contains the internal model of the reference step input.This paper gives the controller design process in detail.Using matrix inequality(LMI)optimization method,the state feedback gain matrix is obtained by arranging the closed-loop poles in the specified region,and the influence of the regional parameters on the system performance is discussed in detail,providing guiding principles for controller parameter setting in practical application.The experimental results show that the closed-loop system with internal model control has better control performance in terms of constant value tracking,square wave tracking and interference suppression.