Ducted Fan Configuration Research Articles

Robust Flight Control Using Nonsmooth Optimization for a Tandem Ducted Fan Vehicle

AbstractThis work addresses the aerodynamic modeling and near‐hover‐flight control design for an unconventional aerial robot of the tandem ducted fan configuration, which is intended to be prototypical of a flight service vehicle. The main model elements of this novel unmanned vehicle, which exhibit highly nonlinear and unstable open‐loop modes, are presented. A frequency‐domain controllability analysis concerning the plant's behavior around the hovering flight condition is then adopted to determine the expected control performance, which is of important practical significance to controllability improvement through vehicle design changes. A robust controller that stabilizes the unmanned vehicle under wind disturbances is designed using a newly developed nonsmooth optimization algorithm, which rigorously and efficiently tunes the arbitrarily predefined structured controller against multiple control requirements. A successive two‐loop architecture is employed in the designed controller. In this architecture, the inner loop provides stability augmentation and decoupling, and the outer loop guarantees the desired velocity tracking performance. Simulation results under stochastic wind gusts are presented to verify the performance of the proposed controllers. Preliminary flight tests are also carried out to demonstrate the performance of the system.

Flight Control of TUAV with Coaxial Rotor and Ducted Fan Configuration by NARMA-L2 Controllers for Enhanced Situational Awareness

Flight Control of TUAV with Coaxial Rotor and Ducted Fan Configuration by NARMA-L2 Controllers for Enhanced Situational Awareness

Nondimensional Modeling of Ducted-Fan Aerodynamics

The unique aerodynamic nature of the ducted-fan configuration makes it difficult to represent in terms of traditional nondimensional coefficients. Analysis of wind-tunnel data for an axisymmetric generic ducted-fan configuration has led to a new nondimensional modeling scheme. Force coefficients are plotted versus advance ratio for a range of angles of attack, yielding several observations. Each angle of attack yields a linear trend versus advance ratio, with all lines converging through a single point. This fulcrum point shares the same thrust coefficient value as hover tests but at a nonzero advance ratio. This suggests that a hovering ducted fan self-induces a freestream flow, even though the vehicle is stationary. The complicated pitching moment behavior is captured succinctly through modeling the center of pressuremovement. The fan power required was also successfully modeled using the figure of merit, typically a hover performance metric, over the entire flight regime to relate power required to thrust generated. A new wind-tunnel velocity correction for ducted fans is also presented. The new statistical modeling technique attains very high correlation for present and legacy data. It is possibly the most concise representation of ducted-fan aerodynamics to date, using 12 nondimensional coefficients.

Autonomous takeoff and landing control for a prototype unmanned helicopter

In this paper, an autonomous takeoff and landing control strategy is designed and implemented for a prototype coaxial unmanned helicopter with ducted fan configuration. The control strategy is designed such that longitudinal and lateral controls use ground forces, attitude and drifting feedbacks. Vertical control employs takeoff and landing decision and vertical velocity control is based on altitude tracking. Ground forces feedback is used to balance longitudinal forces and moments during liftoff effectively cancelling all ground forces. Attitude and drifting feedbacks are used to balance the longitudinal and lateral movements of the helicopter during takeoff and landing. The flight control strategy is successfully verified during flight tests.