Development of real time digital controller for a liquid level system using ATMEGA32 microcontroller

Abstract

This project describes how to implement a digital controller algorithm like PI controller in real time using a simple yet effective digital control device-ATMEGA32 microcontroller for controlling a prototype model of a liquid level control system. A liquid level sensor(rotary potentiometer) detects the present level of the liquid in the tank in terms of the voltage across the potentiometer and feeds it to the microcontroller and the control action generated by the microcontroller is amplified through a suitable amplifier that actuates the actuator(the pump) and finally controls the flow output of the pump. The operator has to set the desired level in the microcontroller and accordingly the feedback control in the real time will get operated for achieving the desired level.
In the present project work , a dicretized model of the liquid level system is developed using PI controller and is simulated in MATLAB Simulink so as to observe the nature of the PI controlled system output. It is also compared with the uncontrolled liquid level system model simulation output so as to see the advantage of using a PI controller. Also, an attempt has been made for developing a dummy representation of the actual prototype model for automatic controlling the liquid level so as to know the proper functioning of the algorithm.
The hardware is set up and the devices like the microcontroller, D/A, power amplifier are interfaced with each other .The devices are also tested for their proper functioning. The PI controller is developed in discrete domain and its parameters are determined using the open loop Ziegler Nichols tuning method. The dicretized control algorithm is then implemented in the microcontroller using C language for coding. The nature of the controller is observed and results are shown . Also the experimental results are compared with the simulated results to show the similarity and accuracy of the controller.
This liquid level study will be useful for several industrial and household applications like boiler level control , household supplies and many more.