Linearization and analysis of level as well as thermal process using labview

Abstract

The processes encountered in the real world are usually multiple input multiple output (MIMO) systems. Systems with more than one input and/or more than one output are called MIMO system. The MIMO system can either be interacting or non-interacting. If one output is affected by only one input, then it is called non-interacting system, otherwise it is called interacting system. The control of interacting system is more complex than the control of non-interacting system. The output of MIMO system can either be linear or non-linear. In process industries,the control of level, temperature,pressure and flow are important in many process applications.In this work, the interacting non -linear MIMO systems (i.e. level process and thermal process) are discussed. The process industries require liquids to be pumped as well as stored in tanks and then pumped to another tank. Most of the time the liquid will be processed by chemical or mixing treatment in the tanks, but the level and temperature of the liquid in tank to be controlled at some desired value and the flow between tanks must be regulated.The interactions existing between loops make the process more difficult to design PI/PID controllers for MIMO processes than that for single input single output (SISO) ones and have attracted attention of many researcher in recent years.In case of level process, the level of liquid in the tank is controlled according to the input flow into the tank. Two input two output (TITO) process and four input four outputs (FIFO) process are described in the thesis work. The aim of the process is to keep the liquid levels in the tanks at the desired values. The output of the level process is non-linear and it is converted into the linear form by using Taylor series method. By using Taylor series method in the non-linear equation, the converted linear equation for the MIMO process is obtained. The objective of the thermal process is to cool a hot process liquid.The dynamic behaviour of a thermal process is understood by analysing the features of the solutions of the mathematical models. The mathematical model of the thermal process is obtained from the energy balance equation. The nonlinear equation is linearized by using Taylor series. The responses of the higher-order thermal process (3 x 2 and 3 x 3) are obtained and analysed. Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) is used to communicate with hardware such as data acquisition, instrument control and industrial automation. Hence LabVIEW is used to simulate the MIMO system.