Designing PID Controller using LABVIEW for Controlling Liquid Level in Tank Project Members: M.Premraj (91710112022) G.Rakesh (91710112023) J.Rameshwaran (91710112303) Guide Name: K.Kalanithi M.Tech AP / ICE

ABSTRACT In this project we have designed a virtual PID using LabVIEW to replace the conventional PID controller. There are some difficulties in the conventional PID controller such as precise mathematical model of a real time system and transfer functions are difficult to calculate, and it requires necessary space for hardware and interfaces. The designed PID controller reduces the risk of complex circuits, accumulation of space and also the mathematical calculation. The virtual PID controller is connected to the real time systems using Data Acquisition card (DAQ). This designed PID is used for level control process in our project. 

EXISTING METHOD In the existing method, a conventional PID is used for controlling process. Conventional control approaches are more complex for time varient systems.  The present system employs conventional controlling mechanisms like P, PI and PID.

DISADVANTAGES The conventional PID is complex in design due to mathematical expressions. The maintenance cost of the conventional PID is high. Design of conventional PID logic needs more period of time. The conventional PID cannot be upgraded.

PROPOSED METHOD In the present era of industrial automation, ease of work is one of the major concerns. The virtual PID design enables the operator to operate the process sophisticatedly with an ease. Instead of giving manual inputs to the PID, this designed PID can adjust the input parameters just by mouse clicks. By using this PID we are going to control the fluid level of the tank.

BLOCK DIAGRAM OUTPUT FCE Process tank PID SP DAQ Level sensor LabVIEW

BLOCK DESCRIPTION The designed virtual PID controller is used as a control element which provides necessary control actions. The level sensor is used to read the input signals from the tank and transmits the signal to the DAQ, which reads the analog input signal corresponding to the level of the tank. The DAQ sends the digital signal to pc to compare it with the set point. Then signal from the pc actuates the solenoid valve.

VIRTUAL INSTRUMENTATION Virtual instrumentation is the use of customizable software and modular measurement hardware to create user defined measurement systems, called the virtual instruments.

LABVIEW LabVIEW is a program development application, much like various commercial C or BASIC development systems, or National Instruments Lab Windows.

LEVEL SENSOR Infrared sensors are used as level sensing element. These sensors provide the analog output to determine the level. Black surfaces provide the devices a noise free surroundings. These infrared sensors are based on the principle of transmitting and receiving infrared signals. This sensor provides an accurate analog value for the level for further process of data.

DAQ CARD Data Acquisition card (DAQ) is a device which is used to interface the real time system with the pc programmed software DAQ card converts the real time analog signal into digital signal which is understandable for the pc. The DAQ used in the project is NI USB 6009 which consists of 8 analog inputs, 2 analog outputs and 12 digital I/O ports.

RELAY DRIVER The solenoid valve is controlled through normally closed type relay switches. The relay used here is ULN 2803 which is a 18 pin chip. The first 8 pins and the last 8 pins are the inputs and outputs respectively. The 9th and the 10th pins are the ground and common respectively. After the level is sensed, the relay drives the solenoid valve corresponding the level.

HARDWARE REQUIREMENT SOFTWARE REQUIREMENT Data Acquisition card (DAQ) Infrared level sensor Solenoid valve Relay switch SOFTWARE REQUIREMENT VI LabVIEW

ADVANTAGES Conventional PID instrument is replaced with virtual PID. Saves time of manufacturing of an instrument. Need less maintenance. Easy to upgrade. Real time integration. Graphical user interface.

CONCLUSION The experimental investigation in NI LabVIEW show that the new system developed would be highly flexible and easy in controlling the level. This new system will create a new era in the field of automation

FUTUREWORK In future, the current virtual PID is applicable for time variant systems. When the system has uncertainties and difficult to find mathematical model, the fuzzy logic controller will give a better results. The virtual PID based on fuzzy logic will give a satisfactory performance for those time variant and non linear systems. Here in this project solenoid valve is used but in order to increase its accuracy a motorized valve can be used. And since LabVIEW is used here the level can be monitored and controlled from anywhere in the world.

SCREEN SHOT Screen shot of block diagram

SCREEN SHOT

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