Controlling of D.C. Motor using Fuzzy Logic Controller

摘要

Most of the industrial controllers in use today utilize PID controllers. In this paper four methods for tuning of a PID controller are compared. A mathematical model of the most commonly used dynamic system i.e., a d.c. motor is derived and a PID controller is used in conjunction to it. Ziegler-Nichols rule based on the value of Kp is used to tune the PID controller and the response is studied. Further, fuzzy controller is used with PID i.e. Fuzzy PID Controller. The results obtained are compared and a conclusion is drawn that Fuzzy controlled PID responds better in case of change in load and other system disturbances. 1.Introduction: Because of their high reliabilities, flexibilities and low costs, DC motors are widely used in industrial applications, robot manipulators and home appliances where speed and position control of motor are required. PID controllers are commonly used for motor control applications because of their simple structures and intuitionally comprehensible control algorithms. Controller parameters are generally tuned using hand-tuning or Ziegler-Nichols frequency response method. Both of these methods have successful results but long time and effort are required to obtain a satisfactory system response. Two main problems encountered in motor control are the time-varying nature of motor parameters under operating conditions and existence of noise in system loop. Analysis and control of complex, nonlinear and/or time-varying systems is a challenging task using conventional methods because of uncertainties. Fuzzy set theory (Zadeh , 1965) which led to a new control method called Fuzzy Control[1] which is able to cope with system uncertainties. DC motor control is generally realized by adjusting the terminal voltage applied to the armature but other methods such as adjusting the field resistance, inserting a resistor in series with the armature circuit are also available. Ziegler-Nichols [2] frequency response method is usually used to adjust the parameters of the PID controllers. However, It is needed to get the system into the oscillation mode to realize the tuning procedure. The proposed approach uses both fuzzy controllers and response optimization method to obtain the approximate values of the controller parameters. Then the parameters may be slightly varied to obtain the user-defined performance of the real-time control system. Then the parameters may be slightly varied to obtain the user-defined performance of the real-time control system. Thus, it’s an actual problem to design adaptive PID controllers without getting the system into the oscillation mode. Here the mathematical model of a dc motor is used to obtain a transfer function between shaft position and applied armature voltage. This model is then built in MATLAB Simulink. Then design and tuning of proportional-integral-derivative (PID) controllers are reviewed in Simulink with the proposed design procedure. 2. DC motor model In armature control of separately excited DC motors, the voltage applied to the armature of the motor is adjusted without changing the voltage applied to the field. Figure shows a separately excited DC motor equivalent model. ( ) ( ) ( ) ( ) ( ) Conference on Advances in Communication and Control Systems 2013 (CAC2S 2013) © 2013. The authors Published by Atlantis Press 666 ( ) ( ) .(2) ( ) ( ) ( )