Four Rotors Helicopter Yaw and Altitude Stabilization

AbstractSIn this paper an appropriate four rotors helicopternonlinear dynamic model for identication and control lawsynthesis is obtained via modelization procedure where severalphenomena are included like gyroscopic effects and aerodynamicfriction. The numerical simulations of the model obtained showthat the control law stabilizes the four rotors helicopter withgood tracking. I. I NTRODUCTION Autonomous Unmanned Air vehicles (UAV) are increas-ingly popular platforms, due to their use in military applica-tions, trafc surveillance, environment exploration, structureinspection, mapping and aerial cinematography [1]. For theseapplications, the ability of helicopters to take off and landvertically, to perform hover ight, as well as their agility, makethem ideal vehicles.Four rotors helicopter Fig.1 have several basic advantagesover manned systems including increased manoeuvrability[2],low cost, reduced radar signatures. Vertical take off andlanding type UAVs exhibit further advantages in the manoeu-vrability features. Such vehicles are to require little humanintervention from take-off to landing. This helicopter is oneof the most complex ying systems that exist. This is duepartly to the number of physical effects (Aerodynamic effects,gravity, gyroscopic, friction and inertial counter torques) actingon the system [4].The idea of using four rotors is not new. Afull-scale four rotors helicopter was built by De Bothezat in1921[3].Helicopters are dynamically unstable and therefore suitablecontrol methods are needed to stabilise them. In order to beable to optimize the operation of the control loop in terms ofstability, precision and reaction time, it is essential to knowthe dynamic behavior of the process wich can be establishedby a representative mathematical model.II. D