Altitude and Horizontal Motion Control of Quadrotor UAV in the Presence of Air Turbulence M. Kamran Joyo, D. Hazry, S. Faiz Ahmed, M. Hassan Tanveer, Faizan. A. Warsi, A. T. Hussain Centre of Excellence for Unmanned Aerial System (COEUAS) Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia. Email: g1330610953@studentmail.unimap.edu.my , hazry@unimap.edu.my , syedfaiz@unimap.edu.my Abstract—Quad-rotor Unmanned Aerial Vehicles (UAVs) have become prominent rotorcraft amongst the helicopter type UAVs. They have been studied immensely in the recent past years. Several issues regarding its position and altitude control have been observed in conditions such as heavy wind gusts. In these circumstances it is necessary for quadrotor to carry a robust controller that responds quick enough to reduce the risk of terrific descent and drift from its original position. This article presents improved PID control technique to hold the horizontal position and descent rate of UAV under intense turbulent environments. The parameters of PID are extracted from auto tuned PID. The proposed control design is simulated on MATLAB platform. The outcomes of the research work demonstrate that under the extreme air turbulence the proposed control design works effectively for altitude and horizontal motion controlling of quadrotor UAV. Keywords— Quadrotor, UAV, PID, Altitude, Horizontal motion Control. I INTRODUCTION UAVs are becoming extensively well-known in several military and civil applications. Forces have been exploiting the area of UAVs immensely. The utmost military interest has led UAVs to become more sophisticated machine. Improved technological advancement has directed UAVs to operate and effectively accomplish complex missions. The sudden surge in their demand is due to their saturation in all aspects of major civil and military applications. Military utilize UAVs for special purpose applications such as spying, border patrolling [1], coast guard surveillance and target acquisition [2][3]. UAVs are also becoming part of civil applications such as geographic environmental inspection, assessment of weather forecast and most importantly they are involved in search and rescue missions [4]. Quadrotor is a unique type of rotorcraft which carry numerous abilities including the above mentioned capabilities. Likewise helicopters, quadrotor UAVs are also capable to quickly manoeuver from one point to another point. Quadrotor UAVs are available in variety of sizes. The minimum length available is in centimetres [5]. The development of quadrotor is simple as its structural design is not complex as compared to other rotorcrafts. Regardless of its uniqueness, quadrotor UAV is completely nonlinear in nature due to which it carries numerous issues regarding flight controls for its stabilization. The altitude and position controlling in heavy tabulated areas has remained an issue in the past years. This article presents a robust PID control technique for position and altitude steadiness of quadrotor under heavy wind gusts. A Related Work Several algorithms have been developed for altitude and horizontal motion control of quadrotor. Adaptive neural controller for handling attitude control system of UAV [6]. PID was used for altitude and attitude controlling of quadrotor [7]. Sliding mode and PID control was used for the quadrotor system [8]. Backstepping and sliding mode method was used for altitude, attitude and position control of a quad-rotor, the results of this technique showed a flexible control structure and it was also presented in the article that quad-rotor was able to perform autonomous hovering with altitude control and autonomous take-off and landing [9]. Fuzzy logic control was applied on position, altitude and attitude [10]. Dynamic Surface Control (DSC) method was used for altitude control and position control [11]. This paper presents a control technique based on LQR controller for altitude and horizontal motion stabilization. The proposed algorithm is simulated on (MATLAB). The organization of the paper is structured as the section II refers to the system modelling in which kinematics and kinematics of quadrotor have been discussed. Section III is regarding the proposed Control design while section IV includes the implementation of proposed control design and section V comprises of the simulation results. II SYSTEM MODELLING The quadrotor comprises of four motors individually positioned at the end of the cross frame. The direction of motors is set in such a way that a pair of motors rotate clockwise while other pair rotates counter clockwise as shown in Fig. 1. This arrangement of motors is set in order to generate vertical lifting force to raise the quadrotor in the 2013 IEEE Conference on Systems, Process & Control (ICSPC2013), 13 - 15 December 2013, Kuala Lumpur, Malaysia 978-1-4799-2209-3/13/$31.00 ©2013 IEEE 16