Attitude estimation and control of a ducted fan VTOL UAV

A significant area of current research is to develop aircraft which are unmanned. More specifically, some researchers are focusing on hovering type aircraft, or vertical take-off and landing (VTOL) aircraft. Since these types of aircraft do not need to be constantly in motion to maintain lift, they have certain advantages over fixed-wing aircraft. Suitable applications could involve aerial photography, atmospheric measurements or surveillance and defense. The most common type of VTOL aircraft is the helicopter. One disadvantage of this aircraft is the degree of danger involved due to the exposed rotor blades. This is one motivating factor behind the ducted fan system. This type of system uses a rotor which is enclosed in a aerodynamically shaped duct. The introduction of a duct also tends to increase the thrust obtained from the rotor, which is known as thrust augmentation. In traditional helicopters a tail rotor is used to counter the torque acting on the main rotor which is mainly due to the aerodynamic drag experienced by the rotor. To counter the rotor torque in the ducted fan system, a second counter-rotating rotor can be used. The two rotors are placed in series which is also known as a coaxial rotor.; In order for VTOL aircraft to be autonomous, a control system is required to provide attitude stabilization. Using this type of control, a pilot could then direct the aircraft while the onboard controller performs the required action to keep the aircraft stable and flying at the desired operating point. One crucial part in achieving this task is the requirement of accurate knowledge of the system's attitude. To obtain information related to the systems attitude, a number of inertial sensors can be used. These sensors usually consist of accelerometers, magnetometers, and gyroscopes. All of these sensors are often used since each sensor has its own limitations.; A description of the system aerodynamics is given to describe the system forces and torques. Also, a thorough description of several forms of attitude representation is given. A PD controller for the attitude regulation has been successfully implemented based on the use of attitude estimation algorithms relying on the IMU signals.; Simulations and experimental results are given to show the performance of the estimation and control algorithms. Also, a fully operational prototype has been developed which is used to carry out experimental results.