I.J. Information Technology and Computer Science, 2018, 1, 16-23 Published Online January 2018 in MECS (http://www.mecs-press.org/) DOI: 10.5815/ijitcs.2018.01.02 Copyright © 2018 MECS I.J. Information Technology and Computer Science, 2018, 1, 16-23 Optimal PID Design for Control of Active Car Suspension System O. Tolga Altinoz Ankara University, Department of Electrical and Electronics Engineering, Ankara, 06830, Turkey E-mail: taltinoz@ankara.edu.tr A. Egemen Yilmaz Ankara University, Department of Electrical and Electronics Engineering, Ankara, 06830, Turkey E-mail: aeyilmaz@eng.ankara.edu.tr Received: 13 October 2017; Accepted: 01 December 2017; Published: 08 January 2018 Abstract—This research is based on the determination of the parameters of the PID and fractional-order PID controllers designed for quarter-car suspension system. Initially, without considering the active suspension structure, the performance of the passive suspension system under different wheel load index is presented by using the transfer function of the system. Then, by adding a wheel-load, the classical PID controller is designed and applied to the current controlled hydraulic actuator as a part of active suspension system. The parameters of this controller are determined by three heuristic optimization algorithms; Particle Swarm Optimization (PSO), Differential Evolution (DE) and Gravitational Search Algorithm (GSA). As the second part of this study after evaluating the performance of classical PID controller, fractional-order PID controller is designed and applied to the problem to improve the performance of the classical PID controller. Similarly, the parameters of this controller are also obtained by using the same optimization algorithms. In the paper, for modeling the road, instead of sinusoidal (road with hill) or random changes, a saw tooth signal is preferred as a relatively harder condition. Implementation results are showed that the performance of the fractional-order PID controller is much better that PID controller and also instead of relatively complex and expensive controller, it is possible to use fractional-order PID controller for the problem. Index Terms—PID Control, Fractional-order PID control, Particle Swarm Optimization, Differential Evolution, Gravitational Search Algorithm, suspension system, quarter-car. I. INTRODUCTION Suspension systems are installed between car body and wheel to absorb the undesired vibration which occurs due to the road condition. Road handling capability of any transportation vehicle (wheeled vehicles) is the key factor for safety and comfort of the passengers, and it has direct relation with suspension system. The necessity of suspension systems can be summarized as: i. To absorb the vibration due to the imperfect conditions of the way, ii. To comfort of the passengers from way conditions, iii. To transfers braking force to the wheel and protect the integrity between wheel and car body. Similar to air platforms, wheeled vehicles are under three main oscillation force as graphically presented in Fig. 1. Saltation: movement of the car from up to down caused from light rough road at high speed Swing: movement of the front and end of the car caused from heavy rough road at relatively slow speed (fast speed isn‟t suggested) Rollover: movement of the left and right of the car, caused from turns. Each of these movements corresponds to the force on the suspension system from ground to car body. In other words, the change at the position of the wheel causes these oscillations, and it is expected from the suspension system to handle these conditions and guarantee (if it is possible) a safe and comfort travel. Rollover Swing Saltation Fig.1. Three oscillation behavior on the wheeled (road) vehicle. In a general manner, the models of the suspension can be divided into three forms with respect to the control perspective: passive, semi-active [1] and active [2] suspension systems. Passive suspension systems are pre- designed and plug-in devices such that almost all parameters are determined at the production phase. Hence,