DESIGN AND CONSTRUCTION OF A SPEED CONTROL OF A DC FAN USING A FUZZY CONTROLLER

DESIGN AND CONSTRUCTION OF A SPEED CONTROL OF A DC FAN USING A FUZZY CONTROLLER

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND STUDY

Temperature Control cuts through a variety of Industrial and domestic processes such as temperature controlled heat exchangers, baths, green houses, incubators. A DC motor may be used as Fan in accomplishing temperature control. An Electric Fan is basically a device which comprises of three blades at 120 degrees mounted on the DC motor spindle.An electric fan circulates the air around its environment while an air-conditioning system changes the temperature of the air in it environment. Many system used in our daily life which require controlling are non-linear in nature; hence, a detailed system dynamics is difficult to represent mathematically. Temperature control is stochastic and a slowly changing process which requires heuristic based control. Many authors have proposed Fuzzy Logic Inference System in dealing with temperature control.  In households during summer which is analogous to dry season in West Africa, Air conditioners are responsible for 60-70% of summer electricity bill. A window air-conditioning unit uses 500 to 1440 watts,while a 2.5-ton central system uses 3500 watts .However, an electric fan uses only 90 watts, depending upon the speed and size (Ali Newaz Bahar et al, 2012). An electric fan is a device that on the long run will on the one hand help in keeping us cool in summer and on the other hand help in saving money as well as protecting the environment by limiting the release of Carbon-monoxide (Lakshya Kumar et al, 2015).

In this project, a Fuzzy logic controller design is proposed for deployment of the process variable due to the fact that temperature is a slowly changing variable. Hence, for precision control of a stochastic process variable Fuzzy logic based control suffices. While all the regularly used systems are defined by mathematical equations. The temperature of the metal plate decides the amount of current that can pass through it. Temperature of the metal plate is measured with the help of temperature sensors (Lakshya Kumar et al, 2015). The amount of energy supplied to the fan is to be controlled by SVM or PWM technique.

The human brain has an unpredictable way of reasoning and thus has a high adaptive approach with recourse to control. It does not reason as computers do. Computers reason in a clear statement that uses true or false (0 or 1) – an element is either a number of a given set or it is not. There are many complex systems which do not fit into the precise categories of conventional set theory. This is because of the fact that there is no way to define a precise  threshold  to  represent  their  complex  boundary,  and  as  such  their  control  system  is  complex.  Fuzzy logic was developed owing to this imprecise nature of solving control problems by computer. In a  fuzzy  logic-based  system,  a  variable  can take  any  truth  value from  a  close  set  [0,  1]  of  real  numbers  thus  generalizing  Boolean truth  values [1]. But  the  fuzzy  facts are  true only  to some  degrees  between  0  and  1,  and  they  are  false  to  some  degrees  (Isizoh A. N., et al, 2012). The Fuzzy inference is based on Human heuristic reasoning pattern. But computers  cannot  do  so  because  its  logic  is  based  on  approximate  reasoning  in  a  more  familiar  Boolean  forms  of  logic used in conventional set theory.  Fuzzy logic allows the  use of labels like “slightly”, “moderately”, medium, and “very” so  that  statements  may  be  made  with  varying  degree  of precision. This flexibility is useful in coping with the imprecision of real-world situations such as designing precision environmental control systems. In a broad sense, fuzzy logic refers to fuzzy sets – a set with non-sharp boundaries. Fuzzy logic is widely used in machine controls, as it allows for  a  generalization  of  conventional  logic  and  provides  for terms  between  “true”  and  “false”,  like  “almost  true”  or partially  false”.

DESIGN AND CONSTRUCTION OF A SPEED CONTROL OF A DC FAN USING A FUZZY CONTROLLER