Autonomous Flight Control of a Vertical Takeoff and Landing Fixed-Wing Unmanned Aerial Vehicle

In this new age of UAVs, innovative and unconventional designs are becoming more popular due to their versatility and large mission scope. This paper will develop a gain scheduling control strategy for autonomous control of a... [ view full abstract ]

In this new age of UAVs, innovative and unconventional designs are becoming more popular due to their versatility and large mission scope. This paper will develop a gain scheduling control strategy for autonomous control of a fixed-wing tilt-rotor vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV). This innovative vehicle combines the long-range flight capabilities of traditional fixed-wing aircraft with the VTOL and hovering capabilities of helicopters. This greatly enlarges the flight envelope, which includes three flight regions: hovering and vertical flight, level forward flight, and the transition between the two aforementioned flight modes.

This vehicle contains nonlinear system dynamic behavior. In order to achieve acceptable controllability, a gain scheduling controller is proposed. This methodology uses a scheduling parameter, which will be taken as the angle between the tilt rotors and the aircraft’s body axis. The nonlinear system will then be linearized about a finite set of operating points resulting in a set of linear models that describe the aircraft’s dynamics throughout its flight envelope. Individually tuned linear PID controllers designed for each linear model will be implemented as required by the global gain scheduling control strategy. This controller will allow the fixed-wing tilt-rotor VTOL UAV to smoothly transition between hover flight and level forward flight, and back to hover flight. The main goal of this research is to design a transition maneuver controller that enables the fixed-wing VTOL UAV to complete the transition from vertical flight to level forward flight as quickly as possible, and with minimal energy losses.

In this paper, the proposed fixed-wing VTOL UAV dynamics model will be developed, and then a gain scheduling controller design will be presented, and demonstrated by extensive computer simulations. The stability of the system and its performance will be addressed in detail, for example, the time taken to complete the transition maneuver will be recorded and compared with similar VTOL UAVs. It will not be required that the altitude remain fixed during the transition maneuver, which will allow the aircraft to vertical takeoff and immediately transition into level forward flight. It is expected that the simulation results will show that gain scheduling is a viable option for the control of fixed-wing tilt-rotor VTOL UAVs and may even show that this controller’s response is superior to the current controllers found in literature.