SUST Journal of Engineering and Computer Science (JECS), Vol. 17, No. 2, 2016 19 Performance Evaluation of a Fractional Order PID Controller Applied to Separately Excited Direct Current Motor Speed Control Aamir Hashim Obeid Ahmed School of Electrical & Nuclear Engineering, Sudan University of Science and Technology (SUST) aamirahmed@sustech.edu ; Aamir_elec@yahoo.com Received: 11.01.2015 Accepted: 02.08.2015 ABSTRACT - At the present time, Direct Current (DC) motors have been widely used in many industrial applications. The main reason for their popularity is the ability to control their torque and flux easily and independently. The most commonly used controller for the speed control of DC motor is conventional Proportional-Integral-Derivative (PID) controller. However, the conventional PID controller has some disadvantages. To overcome these disadvantages, various types of modified conventional PID controllers such as Fractional Order PID (FOPID) controllers were developed. This paper presents a comparison of time response specifications between FOPID and conventional PID controllers for a speed control of DC motor. Performance of two controllers has been verified through simulation results using MATLAB/SIMULINK software. Simulation results show that the FOPID controller performs better performance and more robustness than a conventional PID controller. Keywords: Direct Current Motor, Speed Control, PID Controller, FOPID Controller. ال مستخلص- فى الوقت ال حا لى, شر تستخدم فى العديدلمبار التيات ا فإن محركا من اللصناعت ا تطبيقا ي ة. ب الرئيس والسب ىا هو لشعبيته ى التحكم فقدرة عل ال ى ان و عزم الدور الفيض بسهولة و بشكل مستقل. فى سرعة محركلتحكم ل  ماتحكم الكثر إستخدا الم المباشرر ا لتيا هو كمة التنلحا ا اسبية- تكاملية ال- تفاضلية ال اتقليدية ل. و مع ذلك، فإنلتناسبيةكمة الحا ا- تكاملية ال- تفاضلية التقليدية ال لها بعض ا لمساوئ. لتغلب على لذه ه ال مساوئ، تم تطوير أنواع مختلفة من التناسبيةكمة ا لحا- تكاملية ال- تفاضلية التقليدية ال مثل الح واكملتناسبية ا- تكاملية ال- تفاضلية ك ال سرية الرتبة. ذه الورقة هية بينبة الزمنلستجات اصفارنة لموا مقا تقدم الح اكم ةلتناسبية ا- تكاملية ال- ية كسرية الرتبةتفاضل ال و لتناسبيةكمة الحا ا- تكاملية ال- تفاضلية اليدية لتقل ال لتحكم فى سرعة محرك اللمباشرر ا تيا. ق من أداء تم التحقلحاكمتين ال نتائج من خل لمحاكاة ب ا إستخدام برنامجMATLAB/SIMULINK . لمحاكاةئج ا نتا توضح أن الح اكم ةلتناسبية ا- تكاملية ال- ية كسرية الرتبةتفاضل ال أ ظهرت أداء أفضل و أكثر متانة منلحاكمة التناسبية ا- تكاملية ال- تفاضلية التقليدية ال. INTRODUCTION Direct current motor drives, because of their simplicity, ease of implementation; high reliabilities, flexibilities and favorable cost have long been a backbone of industrial applications. They cover wide range of applications including computer peripherals, robotic manipulators, actuators, steel rolling mills, electrical vehicles, paper machine and home appliances [1] . Therefore, the control of the speed of a DC motor is an important issue and has been studied since the early decades in the last century. Numerous controllers have been developed in literature for DC motor speed control. Some of these methods were based on classical and also intelligent approaches [2-5] . Out of various closed loop controller designs available till date, the most commonly used controller for the speed control of DC motors is classical PID controller [5-7] . This is mainly because the classical PID controller is easy to implement either by hardware or by software. No deep mathematical theory is necessary to understand how the classical PID controller works, so everybody is able to imagine what is happening inside the controller during the control process. Furthermore, it has the ability to eliminate steady state offset trough integral action and it can anticipate the changes through