ROBUST TRAJECTORY TRACKING FOR A SMALL-SCALE HYBRID AIRCRAFT
By hybrid aircraft, we mean a UAV that can vertically take-off, land and hover like a helicopter, and meanwhile can be converted to a fixed wing airplane to achieve high forward speed and long endurance than normal helicopters. This paper presents our recent work on control of a novel small scale hybrid aircraft. The proposed aircraft should follow a specific trend of trajectory to be able to convert from helicopter to airplane. For such a purpose, we design a robust trajectory tracking controller for helicopter mode of the aircraft. Finally, the simulation results are presented to demonstrate effectiveness of the proposed controller.
Control Law Modification According to Flight Test of Small Scaled Tilt Rotor UAV
A small scaled flight demonstration model of a tilt rotor aircraft for the Smart UAV Program has been developed. The tethered hover test following the ground test on a test rig with 4 degrees of freedom has been performed prior to the flight test of the scaled model. During the flight test and tethered hover test, the performances of a rotor speed governor and a rate SAS have been evaluated. Because the pilot could not confirm the aircraft attitude at high speed flight condition at low tilt angle, the control structure was modified to attitude SCAS system in pitch and roll axis. All conversion flight tests were performed by pilot’s manual control and the attitude SCAS control law and rotor governor were fully engaged. The pilot had to input the tilt commands during coordinated turn flight in order for the aircraft not to exceed pilot’s visual range. The rate SAS feedback system was also enough to meet handling qualities requirement at all axis so that it would be work as a manual mode in emergency condition. During flight test, the control law has been modified to improve many unexpected aircraft responses. This paper presents the conversion flight test results of small scaled tilt rotor model and also shows the control law updates according to unexpected flight characteristics of tilt rotor aircraft.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.