Performance Analysis of Aircraft Pitch Control By Linear Quadratic Regulator and Fuzzy Controller

Abstract

Today's aircraft consist of number of automatic controller that helps the airplane crew in airplane management and piloting the aircraft. Usually, the control strategies of aircraft can be grouped into two categories as follows: lateral and longitudinal control. In longitudinal control, the pitch angle has been employed for an aircraft system. Pitch of an aircraft may be described as a rotation around the lateral axis. An elevator is used to control pitch of aircraft which is located at the back of an airplane. So in this paper, a pitch control of an aircraft has been implemented by using Fuzzy controller. The stability of aircraft system is of major concern in real interface system. Thus, aircraft system must be accurate having stable response of aircraft system and should approaches to reference over a certain interval of time i.e. it should not oscillate over a long time. So this work exhibits the design of fuzzy control strategy for controlling the pitch angle of an aircraft. Two control strategies: Linear quadratic regulator (LQR) control and Fuzzy control strategies have been employed and compared. After that a comparative analysis of these control strategies has been done. The whole system has been implemented in MATLAB SIMULINK environment. Keywords: Pitch control, longitudinal l control, Lateral control, Fuzzy controller, linear quadratic regulator (LQR). I.INTRODUCTION Pitch control is a longitudinal control; therefore longitudinal model of an aircraft is used to design the pitch angle controller of an aircraft. Roll control is a lateral control. Therefore lateral model of an aircraft is required to design the roll angle controller of an aircraft. The roll angle is used to control the rolling motion of an aircraft. Elevator is used to control pitch of an aircraft and ailerons are used to control roll of an aircraft. The ultimate aim is to follow the elevator and ailerons command with minimum delay and maximum accuracy. To reduce the complexity of system, assume aircraft as a rigid body and aircraft's motion consist of a small deviation from its equilibrium flight condition [1]. In addition, the aircraft control system can be divided into two parts, namely longitudinal and lateral control [2]. In longitudinal control, the elevator controls pitch or the longitudinal motion of aircraft system whereas in lateral control lateral motion (roll and yaw) of aircraft system is controlled. Pitch of an aircraft may be described as a rotation around the lateral axis. It might be calculated as the angle between the direction of speed in a horizontal line and vertical plane Pitch of aircraft is control by elevator which usually situated at the rear of the airplane running parallel to the wing that houses the ailerons [3]. Elevator is used to control pitch or to control the tail planes of an aircraft which is located at the back of an airplane. The elevator pivoted at the rear of an aircraft work in pairs; when the right elevator goes up, the left elevator also goes up. The linear zed mathematical model is o...