Design of longitudinal autopilot for Sky Sailor UAV using SLC and TECS controllers

in recent years, UAVs (Unmanned Aerial Vehicle) have become playing an active role and have been involved in a number of fields such as surveillance, photography, agriculture, transportation and communications. For this reason, the research institution is working to develop linear and non-linear controllers to make these UAVs more stable and effective while performing various tasks assigned to them. In this paper, a longitudinal autopilot was designed for a solar UAV (sky sailor) using two controllers, the first is SLC (Successive Loop Closure) which is a classic controller that is based on successive loops with a PID controller, and the second method is the TECS (Total Energy Control System) controller that depends on the total specific energy rate and the energy distribution rate to control the airspeed and altitude of the UAV. After detailing the working principle and tuning of each controller they were applied to the non-linear model of UAV using MATLAB Simulink. Through the results obtained from the simulations, we conclude that the TECS controller is better than the SLC controller in terms of stability and energy economy, being an ideal choice for solar UAVs to increase their endurance, and for civil aircraft to reduce the cost of flights.