DEVELOPMENT OF A MATHEMATICAL MODEL OF A FIXED WING UAV FOR AUTOMATIC LANDING SYSTEM DESIGN AND SIMULATION
Unmanned Aerial Vehicles (UAVs), especially fixed wing type, have been used in many fields to improve efficiency, safety, and performance such as in farming, mapping, and surveillance. Fixed wing type UAVs, despite of their advantages in speed, altitude, and range, they have certain disadvantages compare to rotary wing type. Rotary wings, especially multicopters, are much easier to control thanks to the relatively slow flying speed, and the readily embedded automatic flight control system. Fixed wings UAV, on the other hand, are inherently fast and requires a well-trained pilot in a ground station to control it properly. Fortunately, this can be solved by implementing automatic flight control system in it. One problem in fixed wings control difficulty is on the landing phase. The most common method is to use a net to catch the UAV after a mission, which will increase dependencies from ground station and reduces the UAV portability. Therefore, developing a suitable automatic landing system for fixed wing UAV might be a better solution. This research is conducted to develop a complete fixed wing UAV model that can simulate a complete mission and can be used as basis to build a desired yet simple automatic landing control and guidance law. The UAV model is built on MATLAB/Simulink environment, which can simulate the vehicle in all its 6 Degree of Freedom. Two additional blocks are added in the model to describe specific condition in landing. The first is the wind model to accommodate the windy situation, while the second one is the landing gear dynamic model to observe the landing loads on impact and the ground maneuvers. Using pole placement for stabilization loop and PID controller for the control and guidance loop, the automatic landing system can perform automatic landing with no wind disturbance. The automatic landing system can also guide the UAV to do turn around maneuver if the UAV position is not proper to start landing. The result shows that the required landing distance from 100 m altitude with 20 m/s airspeed and 2.5 degrees glideslope is 2500 m. To accommodate wind disturbance during landing, the automatic landing system need to be improved with more robust control design method.