Modeling And Control Of Quadruple-tank System

The quadruple-tank system is a typical liquid level system with nonlinear,hysteresis,time-varying and other characteristics.As a typical representative of liquid level control in industrial production,the quadruple-tank system contains the complex characteristics of almost all industrial liquid level systems.The four-input and double-output quadruple-tank system is more complex on the basis of the original single-capacity and dual-capacity systems.Its coupling,minimum phase and non-minimum phase characteristics,and inaccuracy of model parameters are its liquid level precise control zone.It is difficult.In addition,during the liquid level control process,when the controller output exceeds the pump's operating voltage range,the liquid level can not be accurately controlled.On the basis of the problems found in the quadruple-tank system,firstly,the software and hardware system of the liquid level system experimental device are introduced,and the basic working principle of the device is explained.Then the ideal is established based on the Bernoulli equation.The mathematical model of the liquid level control of the quadruple-tank system in the state.Because of the lack of flowmeters,we have adopted a new method to determine the flow characteristics of the pump.It is found that there is a good linear relationship between the input voltage of the pump and its flow characteristics,and the experimental data is fitted to determine the flow of the pump.Characteristics,and then the other parameters of the tank model are identified by the balance equation.Then,the open-loop characteristics,nonlinearity,and coupling of the quadruple-tank system are tested and the minimum phase and non-minimum phase characteristics are analyzed.Secondly,the high-gain adaptive control algorithm of the quadruple-tank liquid level system is introduced.The relative gain array(RGA)of the dual-input dual-output system is determined.Based on the analysis results of the relative gain array,the quadruple-tank system is determined to be the minimum phase.The relative gain between the two inputs and the two outputs in the two different operating conditions of the characteristic and non-minimum phase characteristics,based on which the distributed control scheme is determined,and the high-gain control algorithm is used to coordinately control the quadruple-tank system and obtain Corresponding simulation curve.Finally,using the nonlinear system feedback linearization technology,the dual-input dual-output quadruple-tank system is statically decoupled and decomposed into two single-input systems,and then the variable-position PID control algorithm is used to achieve liquid level adjustment.The variable structure PID control algorithm not only retains the advantages of conventional PID control,but also controls the input voltage return constraint to improve the control performance of the system.