GA-PID controller for position control of inverted pendulum

Stability is very necessary in control system and it becomes more difficult to achieve for a nonlinear system which inverted pendulum is an example. Most of the controllers available suffer from problems such as difficult in tuning process, sluggishness in response time, quick and global convergence etc. This paper considered Proportional-Integra-Derivative optimized with Genetic Algorithm (GA-PID) Controller on Inverted pendulum for the control of the angle position. Conventional PID controller was used to validate the proposed controller. A MATLAB script for genetic algorithm was written with the aim of obtaining optimum PID parameters that would keep the pendulum angle at equilibrium (i.e. returns the pendulum to a desire point as quick as possible) by minimizing an objective function (Integral time absolute error ITAE). On the other hand, a convention PID controller was designed using MATLAB/Simulink environment; the PID's gains were manually tuned until an optimum response is achieved. The results obtained in both schemes shows that GA-PID showed superiority in all the performance indices used in evaluating the two controller schemes and therefore can serves as a valuable controller for the system.

I Introduction

Inverted pendulum is a pendulum which has its mass above its pivot point. This system is inherently not stable and must be actively balanced by moving the pivot point horizontally which serve as a feedback to the system or by oscillating the support rapidly up and down so that the oscillation is sufficiently strong enough to restore the pendulum from perturbation in a striking counter intuitive manner.[1]. Inverted pendulum is used as benchmark for testing control algorithms due to its high degree of instability and non-linearity. Real application of the system can be found in Missiles guidance, Rockets, heavy Crane lifting containers in shipyards, self balancing Robots and etc.