Micro Helicopter-Airplane System: Trajectory Tracking and Attitude Control E. S. Espinoza, I. Lugo, O. Garcia, A. Malo and R. Lozano Abstract— This paper focuses on the regulation and trajec- tory tracking for a Micro Coaxial Rocket Helicopter (MCR UAV) and a mini aircraft. The former has the characteristic of performing hover and forward flight while the latter is considered as an external air transporter for the MCR UAV. For control purposes, the helicopter stabilization is based on the Backsteeping procedure, and a PD controller is implemented in the aircraft in order to execute semi-autonomous flight. The avionics for these aerial vehicles consists of an embedded computer, low-cost sensors and homemade modules (Signal Conditioning Circuits, Analog Filters) and the flight control algorithm is implemented in the embedded system. Simulation and experimental results show an effective performance of the developed system during the flight. I. I NTRODUCTION Nowadays, the interest of developing effective UAVs (Un- manned Aerial Vehicles) has been growing. There exists a wide number of applications for mini UAVs with great interest on autonomy and endurance for performing complete missions. This reveals the impact of vehicles that offer a wide operational scope to perform different kinds of missions such as search and rescue, bridge inspections, volcano monitoring and homeland security warfare. The proposed Micro Coaxial Rocket Helicopter (MCR UAV) has a number of advantages compared to other aero- dynamic configurations. It means, our design uses control surfaces (ailerons) to control the attitude flight, and employs the air produced by the coaxial propellers (prop-wash) over the control surfaces to maintain the vertical flight and can operate from any small clear space. However it suffers from well-known deficiencies in terms of range, endurance and forward speed limitations due to the propulsion systems where the thrust force is directed opposite to the weight. Thus, for increasing the autonomy and endurance of our proposed aerial vehicle, a mini aircraft is considered as an external air transporter which releases the MCR UAV in a desired place far away from the launching site, then the MCR UAV develops surveillance missions. Linear and nonlinear controllers, for some aerodynamic coaxial configurations, have been presented in [10]. In [2] E. S. Espinoza is with Polytechnic University of Pachuca, Hidalgo, Mexico. steed@upp.edu.mx I. Lugo, A. Malo and R. Lozano are with Lab- oratoire Franco-Mexicain d’Informatique et Automa- tique, LAFMIA UMI 3175 CNRS-CINVESTAV Mexico. {ilugo,alexmalo,rlozano}@ctrl.cinvestav.mx O. Garcia is with the Aerospace Engineering Research and Innovation Center at the Autonomous University of Nuevo Leon, Monterrey, Mexico. octavio.garcias@uanl.mx R. Lozano is with Laboratoire Heudiasyc, Université de Technologie de Compiègne, Compiègne, France. rlozano@hds.utc.fr presents a micro aerial vehicle which is catapulted by using an air launcher; that vehicle uses the swashplate and coaxial propellers which allow rotational degrees of freedom in order to control roll, pitch and yaw motion, respectively. [7] discusses the control of a micro UAV that is launched by an external device such as a catapult. The main contribution of this paper is to present an aero- dynamic model and control, based on the Backstepping tech- nique, of the MCR UAV for trajectory tracking tasks. This paper also describes the semi-autonomous aircraft which functions as the external air transporter (shuttle carrier) for the MCR UAV. This contribution represents the first stage (second task) of the MCR UAV project introduced in [4] (see Figure 1). This paper is organized as follows: section II discusses the Micro helicopter-airplane system. The dynamic model, based on the Newton-Euler approach, for the aerial vehicles is presented in Section III. In this section, the aerodynamic analysis is shown in hover and forward flight for the MCR vehicle. The Backstepping controllers and the stability anal- ysis in closed-loop are presented in Section IV whereas Section V describes the PD-based control for the mini aircraft. In addition, simulation results of the closed-loop system for hover and forward fight are shown for the MCR UAV and mini aircraft, respectively. Section VI discusses the avionics used and integrated on the vehicles, and the experimental results for the orientation of the mini aircraft are presented in Section VII. Finally, conclusions are given in Section VIII. Third stage Hover mode Fourth stage Cruise mode Five stage Landing in a safe area Camera Observation Second stage Release from the SCR First stage Shuttle Carrier Aircraft stage e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e Sec Fig. 1: Operational regime of the MCR UAV project.