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The objective of this paper is to generate simplified structural configurations for the ANCE X-3d by considering the influence of structural flexibility on the flight dynamic characteristics and the aeroelastic phenomena. This air...
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The objective of this paper is to generate simplified structural configurations for the ANCE X-3d by considering the influence of structural flexibility on the flight dynamic characteristics and the aeroelastic phenomena. This aircraft consists of an unswept wing with double tail boom structure and two vertical stabilizers. Two structures were designed by an analytical approach and finite element models to create suitable structural arrangements for the wing, tail booms, and stabilizers, and carbon-fiber composite materials were selected for this purpose. Knowing the stiffness and mass properties of the main structural components, reduced order aero-structural models were developed to quantify the influence of the flexibility on the aircraft aerodynamics and stability characteristics. Flight dynamic evaluation of the airplane considering the flexibility of the structure was performed at different velocities and altitudes. The resultant flutter and divergence velocities fulfill the design criteria.
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摘要 :
The objective of this paper is to generate simplified structural configurations for the ANCE X-3d by considering the influence of structural flexibility on the flight dynamic characteristics and the aeroelastic phenomena. This air...
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The objective of this paper is to generate simplified structural configurations for the ANCE X-3d by considering the influence of structural flexibility on the flight dynamic characteristics and the aeroelastic phenomena. This aircraft consists of an unswept wing with double tail boom structure and two vertical stabilizers. Two structures were designed by an analytical approach and finite element models to create suitable structural arrangements for the wing, tail booms, and stabilizers, and carbon-fiber composite materials were selected for this purpose. Knowing the stiffness and mass properties of the main structural components, reduced order aero-structural models were developed to quantify the influence of the flexibility on the aircraft aerodynamics and stability characteristics. Flight dynamic evaluation of the airplane considering the flexibility of the structure was performed at different velocities and altitudes. The resultant flutter and divergence velocities fulfill the design criteria.
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Proportional-integral, single-input single-output (PI SISO) control is a common approach and therefore appealing for altitude and speed control loops. The aircraft dynamics of altitude and speed are inherently coupled. Total Energ...
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Proportional-integral, single-input single-output (PI SISO) control is a common approach and therefore appealing for altitude and speed control loops. The aircraft dynamics of altitude and speed are inherently coupled. Total Energy Control System (TECS) architectures can overcome coupling between speed and altitude control. The influence of the control architecture on control effort and motor activity which possibly influence flight time and range, as well as the architectural influence on control performance is critical when selecting the architecture for longitudinal control. This paper contributes to the design, the evaluation and choice of a proper control architecture, comparing advantages and disadvantages of the two approaches. For an uncertain model of a remote controlled UAV glider aircraft, altitude and speed control are developed and analysed. A robust control method, using non-smooth H_∞, design, is described for tuning both a fixed-structure TECS and a PI SISO controller architecture for altitude and speed control. The resulting controllers are based on the same criteria of loop shape and disturbance rejection and compared regarding their linear controller design, implementation and flight test performance on a UAV platform. Flight test data demonstrate the viability of the controller design approach. Performance indicators show reduced control effort for the TECS design without significant trade-offs in tracking.
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This paper focused on the development of a model to represent longitudinal aerodynamics of a wing and/or flight vehicle in ground effect when height is a function of time including high angles of attack. A general aerodynamic mode...
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This paper focused on the development of a model to represent longitudinal aerodynamics of a wing and/or flight vehicle in ground effect when height is a function of time including high angles of attack. A general aerodynamic model of a wing and/or airplane in ground effect which includes high angles of attack was created. The aerodynamic coefficients of wings studied herein were obtained by the unsteady vortex lattice method with Kirchhoff-based correction (UVLM-K). Wind tunnel measurements presented in the literature were used to validate the UVLM-K. Then, a rectangular wing was simulated at high angles of attack in takeoff and flare, and the aerodynamic characteristics at different heights aboveground were obtained along with the h derivatives during these maneuvers. The mathematical model presented herein is capable to model unsteady aerodynamic phenomena in ground effect at high angles of attack. When this model was used in static ground effect, values of R~2 equal to and greater than 0.999,0.981,0.993 were obtained for lift, induced drag, and pitching moment coefficient, respectively. In dynamic ground effect, the model can adjust the aerodynamic coefficient during the maneuvers.
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Highly-flexible aircrafts present high-aspect-ratio wings that introduce nonlinearities into the flight dynamics and make more complex models and control methods necessary. In this paper, a loop separation concept is applied to th...
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Highly-flexible aircrafts present high-aspect-ratio wings that introduce nonlinearities into the flight dynamics and make more complex models and control methods necessary. In this paper, a loop separation concept is applied to the X-HALE aircraft, giving rise to a control system comprising an inner-loop capable of controlling the shape of the aircraft while keeping the plant stable, and an outer-loop capable of controlling velocity, altitude, bank angle and sideslip angle. The outer-loop has a decoupled structure for longitudinal and for the lateral-directional axes. The matrices of the compensators were obtained using non-smooth optimization. Gain-scheduling techniques are implemented to bypass stability problems arising from changes in the plant with flight speed. Nonlinear simulations show promising results for implementation on the real aircraft.
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The objective of the present work is to apply analytical-empirical methods to determine the contribution of a running propeller into the longitudinal stability of a propeller-driven airplane using an analytical-empirical analysis....
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The objective of the present work is to apply analytical-empirical methods to determine the contribution of a running propeller into the longitudinal stability of a propeller-driven airplane using an analytical-empirical analysis. The method is based on the blade element theory to get the forces and moments associated to the rotating blade; and on the blade vortex theory to estimate the interactions between the airflow across the rotation disk of the propeller and the propeller itself. The purpose is to calculate the impact of the propulsion system on the stability derivatives of the aircraft and estimate the necessary parameters to evaluate the static and dynamic stability in the airplane. Although the pitching moment coefficient becomes a function of the airplane velocity due to the contribution of a running propeller, this does not produce significant effects in static stability. In addition, an automatic pilot was designed to control the longitudinal flight dynamics of the aircraft and non-linear simulations were carried out. The results show that there is no significant difference whether the contribution of a running propeller to the longitudinal flight dynamics on a rigid modeled medium unmanned aircraft is considered or not in the design process of the controller.
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摘要 :
The objective of the present work is to apply analytical-empirical methods to determine the contribution of a running propeller into the longitudinal stability of a propeller-driven airplane using an analytical-empirical analysis....
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The objective of the present work is to apply analytical-empirical methods to determine the contribution of a running propeller into the longitudinal stability of a propeller-driven airplane using an analytical-empirical analysis. The method is based on the blade element theory to get the forces and moments associated to the rotating blade; and on the blade vortex theory to estimate the interactions between the airflow across the rotation disk of the propeller and the propeller itself. The purpose is to calculate the impact of the propulsion system on the stability derivatives of the aircraft and estimate the necessary parameters to evaluate the static and dynamic stability in the airplane. Although the pitching moment coefficient becomes a function of the airplane velocity due to the contribution of a running propeller, this does not produce significant effects in static stability. In addition, an automatic pilot was designed to control the longitudinal flight dynamics of the aircraft and non-linear simulations were carried out. The results show that there is no significant difference whether the contribution of a running propeller to the longitudinal flight dynamics on a rigid modeled medium unmanned aircraft is considered or not in the design process of the controller.
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In the continuous search to increase efficiency in fuel consumption and reduce environmental impact, the aeronautical industry is getting more interested in enabling and developing higher aspect ratio wings. However, the increase ...
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In the continuous search to increase efficiency in fuel consumption and reduce environmental impact, the aeronautical industry is getting more interested in enabling and developing higher aspect ratio wings. However, the increase in flexibility tends to deteriorate flying qualities making it necessary to implement more complex controllers and to develop more complex numerical models to capture the real flight dynamics of the aircraft. Nevertheless, there are not enough demonstrators to provide validation data for such models. For these reasons, the Chair of Flight Mechanics, Flight Control, and Aeroelasticity of the TU-Berlin in cooperation with the DLR's Institute of Aeroelasticity is working on the development of TU-Flex, a remotely piloted vehicle designed to gather coupled flight and structural dynamics data to validate flexible/very flexible aircraft models with a typical transport aircraft configuration. This paper shows that it is feasible to attain the levels of deformations required to study the dynamics of flexible and very flexible aircraft in a low-cost scaled demonstrator. The aircraft was designed using an in-house development process that includes the use of DLR's ModGen/NASTRAN for dimensioning the main structural components, and the DLR's software Loads Kernel for the load analysis of the free-flying aircraft. The current geometry of the TU-Flex allows performing experiments in an available wind tunnel facility, and in flight test experiments for a gradual validation process. This demonstrator is capable to attain all main design requirements and it is in a detailed design process and construction. Time-domain simulations are in development with an in-house code for the flight dynamics of very flexible aircraft.
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The interest in the class of unmanned vehicle known as High Altitude Long Endurance aircraft has been growing in the latest years. In this paper, stability problems associated with flight control law design for flexible aircraft a...
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The interest in the class of unmanned vehicle known as High Altitude Long Endurance aircraft has been growing in the latest years. In this paper, stability problems associated with flight control law design for flexible aircraft are evidenced. A fuzzy-based gain-scheduling approach is proposed to adequate closed-loop response. The application of the technique was demonstrated for the flexible X-HALE aircraft and compared to classical interpolation-based gain-scheduling techniques. Nonlinear simulation results revealed that fuzzy-based gain-scheduling is promising for flexible aircraft control.
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摘要 :
The interest in the class of unmanned vehicle known as High Altitude Long Endurance aircraft has been growing in the latest years. In this paper, stability problems associated with flight control law design for flexible aircraft a...
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The interest in the class of unmanned vehicle known as High Altitude Long Endurance aircraft has been growing in the latest years. In this paper, stability problems associated with flight control law design for flexible aircraft are evidenced. A fuzzy-based gain-scheduling approach is proposed to adequate closed-loop response. The application of the technique was demonstrated for the flexible X-HALE aircraft and compared to classical interpolation-based gain-scheduling techniques. Nonlinear simulation results revealed that fuzzy-based gain-scheduling is promising for flexible aircraft control.
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