Variable structure control of pH neutralization of a prototype waste water treatment plant using LabVIEW

This paper aims at developing a control technique using Variable Structure control [VSC] methodology for a pH control plant. The pH control process involves a prototype model in which acidic and alkaline streams are mixed into a Continuous Stirred Tank Reactor [CSTR] in proper proportions so as to control the pH of the plant. The control mechanism involved controls the flow rate of the acid and alkaline solutions. Sliding Mode Control is a type of VSC which is a type of nonlinear control. As the neutralization process is also non linear, VSC serves as a better solution. Also PID control and fuzzy control are incorporated on the same process and the results are compared. The unique feature of this paper is that all the control methods are implemented using LabVIEW SOFTWARE. LabVIEW stands for Laboratory Virtual Instrumentation Workbench. The programming done with this software is applied to the prototype model and the results of PID, fuzzy and VSC are compared and it is found that VSC controller is better suited than PID and fuzzy controllers.