Composite prototyping and vision based hierarchical control of a quad tilt-wing UAV

As the attention to unmanned systems is increasing, unmanned aerial vehicles (UAVs) are becoming more popular based on the rapid advances in technology and growth in operational experience. The main motivation in this vast research field is to diminish the human driven tasks by employing UAVs in critical civilian and military tasks such as traffic monitoring, disasters, surveillance, reconnaissance and border security. Researchers have been developing featured UAVs with intelligent navigation and control systems on more efficient designs aiming to increase the functionality, flight time and maneuverability. This thesis focuses on the composite prototyping and vision based hierarchical control of a quad tilt-wing aerial vehicle (SUAVI: Sabanci University Unmanned Aerial VehIcle). With the tilt-wing mechanism, SUAVI is one of the most challenging UAV concepts by combining advantages of vertical take-off and landing (VTOL) and horizontal flight. Various composite materials are tested for their mechanical properties and the most suitable one is used for prototyping of the aerial vehicle. A hierarchical control structure which consists of high-level and low-level controllers is developed. A vision based high-level controller generates attitude references for the low-level controllers. A Kalman filter fuses data from low-cost inertial sensors to obtain reliable orientation information. Low-level controllers are typically gravity compensated PID controllers. An image based visual servoing (IBVS) algorithm for VTOL, hovering and trajectory tracking is successfully implemented in simulations. Real flight tests demonstrate satisfactory performance of the developed control algorithms

Robust hovering control of a quad tilt-wing UAV

This paper presents design of a robust hovering controller for a quad tilt-wing UAV to hover at a desired position under external wind and aerodynamic disturbances. Wind and the aerodynamic disturbances are modeled using the Dryden model. In order to increase the robustness of the system, a disturbance observer is utilized to estimate the unknown disturbances acting on the system. Nonlinear terms which appear in the dynamics of the vehicle are also treated as disturbances and included in the total disturbance. Proper compensation of disturbances implies a linear model with nominal parameters. Thus, for robust hovering control, only PID type simple controllers have been employed and their performances have been found very satisfactory. Proposed hovering controller has been verified with several simulations and experiments

Robust position control of a tilt-wing quadrotor

This paper presents a robust position controller for a tilt-wing quadrotor to track desired trajectories under external wind and aerodynamic disturbances. Wind effects are modeled using Dryden model and are included in the dynamic model of the vehicle. Robust position control is achieved by introducing a disturbance observer which estimates the total disturbance acting on the system. In the design of the disturbance observer, the nonlinear terms which appear in the dynamics of the aerial vehicle are also treated as disturbances and included in the total disturbance. Utilization of the disturbance observer implies a linear model with nominal parameters. Since the resulting dynamics are linear, only PID type simple controllers are designed for position and attitude control. Simulations and experimental results show that the performance of the observer based position control system is quite satisfactory

LQR and SMC stabilization of a new unmanned aerial vehicle

We present our ongoing work on the development of a new quadrotor aerial vehicle which has a tilt-wing mechanism. The vehicle is capable of take-off/landing in vertical flight mode (VTOL) and flying over long distances in horizontal flight mode. Full dynamic model of the vehicle is derived using Newton-Euler formulation. Linear and nonlinear controllers for the stabilization of attitude of the vehicle and control of its altitude have been designed and implemented via simulations. In particular, an LQR controller has been shown to be quite effective in the vertical flight mode for all possible yaw angles. A sliding mode controller (SMC) with recursive nature has also been proposed to stabilize the vehicle’s attitude and altitude. Simulation results show that proposed controllers provide satisfactory performance in achieving desired maneuvers

Mathematical modeling and vertical flight control of a tilt-wing UAV

This paper presents a mathematical model and vertical flight control algorithms for a new tilt-wing unmanned aerial vehicle (UAV). The vehicle is capable of vertical take-off and landing (VTOL). Due to its tilt-wing structure, it can also fly horizontally. The mathematical model of the vehicle is obtained using Newton-Euler formulation. A gravity compensated PID controller is designed for altitude control, and three PID controllers are designed for attitude stabilization of the vehicle. Performances of these controllers are found to be quite satisfactory as demonstrated by indoor and outdoor flight experiments

Yeni bir insansız hava aracının (SUAVİ) prototip üretimi ve algılayıcı-eyleyici entegrasyonu

Bu çalısmada, dört-döner rotoru ile helikopter gibi dikine kalkıs ve inis yapabilen aynı zamanda da uçak gibi uzun menzil yatay uçus yeteneğine sahip yeni bir insansız otonom hava aracının mekanik ve aerodinamik tasarımı, karbon kompozit imalatı, algılayıcı eyleyici sistem entegrasyonu ve uçus deneyleri anlatılmıstır. Gelistirilen sistem ve içinde kullanılan algılayıcı eyleyici entegrasyonunun basarımı benzetim ve deneylerle doğrulanmıstır

Aerodynamic design and characterization of a quad tilt-wing UAV via wind tunnel tests

This paper presents aerodynamic design and characterization of a new quad tilt-wing unmanned aerial vehicle [Sabancı University unmanned aerial vehicle (SUAVI)] through wind tunnel tests and provides experimental data for the design of similar aerial platforms. SUAVI is capable of vertical takeoff and landing (VTOL) and horizontal flight, and it can perform both indoor and outdoor surveillance. Aerodynamic design of the vehicle directly affects its operational performance, including flight stability and flight duration in vertical, transition, and horizontal flight modes. Selection of the propulsion system and determination of the shape of the fuselage and the wings are done in an optimal manner by taking several aerodynamic criteria into account. Flow simulations reveal that the rear wings are affected by the downwash of the front wings. To solve this problem, the rear wings are placed at a higher incidence angle than the front wings. Wind tunnel tests are performed to measure the lift and drag forces and pitching moments for level flight in the entire speed range. Furthermore, the rear and front motor throttle settings and the wing incidence angle combinations for the nominal flight are measured and tabulated. To eliminate undesired spanwise air flows at the wing tips, several winglets with different shapes and sizes are introduced, and the optimum winglet is developed by several simulations and experiments. Some of the results presented in this paper are novel contributions to the literature and can be used in the design of new hybrid unmanned aerial vehicles (UAVs)