Abstract—Optimizing the parameters in the controller plays a vital role in the control theory and its applications. Optimizing the PID parameters is finding out the best value from the feasible solutions. Finding the optimal value is an optimization problem. Inverted Pendulum is a very good platform for control engineers to verify and apply different logics in the field of control theory. It is necessary to find an optimization technique for the controller to tune the values automatically in order to minimize the error within the given bounds. In this paper, the algorithmic concepts of Harmony search (HS) and Genetic Algorithm (GA) have been analyzed for the given range of values. The experimental results show that HS performs well than GA. Keywords—Genetic Algorithm, Harmony Search Algorithm, Inverted Pendulum, PID Controller. I. INTRODUCTION A. Inverted Pendulum N inverted pendulum is a pendulum which has its centre of mass above its pivot point. It is often implemented with the pivot point mounted on a cart that can move horizontally and may be called a cart and pole. Most applications limit the pendulum to 1 degree of freedom by affixing the pole to an axis of rotation. Whereas a normal pendulum is stable when hanging downwards, an inverted pendulum is inherently unstable, and must be actively balanced in order to remain upright; it can be done either by applying a torque at the pivot point, by moving the pivot point horizontally as part of a feedback system, changing the rate of rotation of a mass mounted on the pendulum on an axis parallel to the pivot axis and thereby generating a net torque on the pendulum, or by oscillating the pivot point vertically. The inverted pendulum is a classic problem in dynamics and control theory and is used as a benchmark for testing control strategies. A second type of inverted pendulum is a tilt meter for tall structures which consists of a wire anchored to the bottom of the foundation and attached to a float in a pool of oil at the top of the structure which has devices for measuring movement of the neutral position of the float away from its original position. The Inverted pendulum also has certain parameters like mass of the pendulum, length, force to be applied to the cart and so on [1]. Thus the parameter and the value needed for this work are given in Table I. Arulanand N. is with the PSG College of Technology, Coimbatore, Tamil Nadu, India (e-mail: arulnat@yahoo.com). Dhara P. is with the Bannari Amman Institute of Technology, Sathyamangalam, Tamil Nadu, India (e-mail: dhara.saran@gmail.com). Fig. 1 Structure of Inverted Pendulum TABLE I PARAMETERS OF THE INVERTED PENDULUM Parameter Nomenclature Value M Mass of the cart 0.5kg m Mass of the pendulum 0.2kg B Friction of the cart 0.1N/m/sec L Length to pendulum center of mass 0.3m I Inertia of the pendulum 0.006 kg*m^2 Theta Pendulum angle from vertical In degree B. PID Controller A controller is a device, historically using mechanical, hydraulic, or electronic techniques often in combination, but more recently in the form of a microprocessor or computer, which monitors and physically alters the operating conditions of a given dynamical system. Typical applications of controllers are to hold settings for temperature, pressure, flow or speed. A system can either be described as a Multiple Input and Multiple Output (MIMO) system, having multiple inputs and outputs, therefore requiring more than one controller; or a Single Input and Single Output SISO system, consisting of a single input and single output, hence having only a single controller. Depending on the set-up of the physical system, adjusting the system's input variable (assuming it is SISO) will affect the operating parameter, otherwise known as the controlled output variable. Upon receiving the error signal that marks the disparity between the desired value (setpoint) and the actual output value, the controller will then attempt to regulate controlled output behaviour. The controller achieves this by either attenuating or amplifying the input signal to the plant so that the output is returned to the set point. A proportional-integral-derivative (PID controller) is widely used in industrial control systems. A PID controller finds an error value as the difference between a measured process variable and a target point. The controller tries to Optimizing PID Parameters Using Harmony Search N. Arulanand, P. Dhara A World Academy of Science, Engineering and Technology International Journal of Mechanical and Mechatronics Engineering Vol:9, No:4, 2015 667 International Scholarly and Scientific Research & Innovation 9(4) 2015 ISNI:0000000091950263 Open Science Index, Mechanical and Mechatronics Engineering Vol:9, No:4, 2015 publications.waset.org/10002675/pdf