摘要 :
Most commercial transport aircraft configure the high-lift settings stepwise. The timing when the slats/flaps are deployed by the automatic system varies from the standard conventional approach. In the standard procedure, the airs...
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Most commercial transport aircraft configure the high-lift settings stepwise. The timing when the slats/flaps are deployed by the automatic system varies from the standard conventional approach. In the standard procedure, the airspeed is reduced to the maximum allowable speed of the next slat/flap configuration, then the pilot commands the next higher slat/flap setting. Thus, most of the time the aircraft does not fly in its optimal aerodynamic configuration, when it maneuvers in the terminal area during approach. This paper describes the development of two different slat/flap deployment functions to optimize the landing approach in terms of fuel consumption. The effects of a high-lift system with continuously moving slats and flaps and with an automatic stepwise system are investigated. Different wind scenarios and different airspeed schedules are simulated and discussed. The investigated high-lift system with continuously moving high-lift devices automatically adapts the slat/flap setting based on the airspeed and aircraft mass and enables the aircraft to fly in an aerodynamic configuration close to optimum with minimal power. The automatic system is optimized on an approach with a previously set stabilization height, i.e. the height where an a priori defined low velocity for landing must be reached and no configuration change is needed. The simulation comparisons showed that the automatic slat/flap function is beneficial, when there are no airspeed restrictions and the aircraft can configure correspondingly to its optimal airspeed schedule, resulting in a similar fuel saving than the continuous function. However, in high-density traffic scenarios with strict airspeed commands by ATC to guarantee safe spacing between two aircraft, the continuous function should be employed instead.
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摘要 :
During approach most airliners move the flap system in fixed steps. As soon as the structural maximum speed of the next higher flap position is undershot, the pilot commands the next flap position via a cockpit lever. The timing w...
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During approach most airliners move the flap system in fixed steps. As soon as the structural maximum speed of the next higher flap position is undershot, the pilot commands the next flap position via a cockpit lever. The timing when the slats/flaps are deployed by the automatic system proposed by the authors varies from the standard conventional approach. This paper describes the results of a flight simulator study with airline pilots to evaluate the automatic continuously moving slat/flap function, including a gear deployment recommendation function. Different mass and center of gravity scenarios and different approach scenarios are flown and discussed. The investigated high-lift system with continuously moving high-lift devices automatically adapts the slat/flap setting based on flight mechanical optimal points and enables the aircraft to fly in an aerodynamic configuration close to minimal power. The automatic system allows a stabilized approach, which means that an a priori defined low velocity for landing is reached before descending below 1,000 ft and no configuration change is needed afterwards. The flight simulator study showed that the automatic continuous slat/flap function is beneficial for the pilots, and can be integrated to acutal approach procedures. For the use of the higher drag configuration, further investigations in the coupling with flight path and airspeed is needed to avoid oscillations.
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The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic mod...
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The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic modal shapes and their properties (damping factors and frequencies) is acquired by generating structural models that are validated in ground vibration tests and then supplemented with unsteady aerodynamic models. The aeroelastic model is validated in flight test, especially to confirm the calculated aerodynamic damping factors. Subsequently, the aeroelastic model and the flight mechanical rigid-body model may be combined to the flight mechanical model for the flexible aircraft that is used for control law design. For small general aviation aireraft for which theoretical aeroelastic models are lacking, an alternative approach is to derive a model from in-flight aeroelastic model identification. With this objective, a flight test campaign was performed for the motor glider STEMME S15. Sine-sweep commands of the control surfaces provided the excitation of the aircraft structure. The most important results of the in-flight modal analysis are presented and discussed in this paper.
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摘要 :
The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic mod...
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The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic modal shapes and their properties (damping factors and frequencies) is acquired by generating structural models that are validated in ground vibration tests and then supplemented with unsteady aerodynamic models. The aeroelastic model is validated in flight test, especially to confirm the calculated aerodynamic damping factors. Subsequently, the aeroelastic model and the flight mechanical rigid-body model may be combined to the flight mechanical model for the flexible aircraft that is used for control law design. For small general aviation aircraft for which theoretical aeroelastic models are lacking, an alternative approach is to derive a model from in-flight aeroelastic model identification. With this objective, a flight test campaign was performed for the motor glider STEMME S15. Sine-sweep commands of the control surfaces provided the excitation of the aircraft structure. The most important results of the in-flight modal analysis are presented and discussed in this paper.
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摘要 :
The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic mod...
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The development of high-bandwidth automatic flight control systems (AFCS) requires the simultaneous consideration of both the aircraft flight dynamics and the aircraft structural dynamics. The knowledge of the aircraft elastic modal shapes and their properties (damping factors and frequencies) is acquired by generating structural models that are validated in ground vibration tests and then supplemented with unsteady aerodynamic models. The aeroelastic model is validated in flight test, especially to confirm the calculated aerodynamic damping factors. Subsequently, the aeroelastic model and the flight mechanical rigid-body model may be combined to the flight mechanical model for the flexible aircraft that is used for control law design. For small general aviation aircraft for which theoretical aeroelastic models are lacking, an alternative approach is to derive a model from in-flight aeroelastic model identification. With this objective, a flight test campaign was performed for the motor glider STEMME S15. Sine-sweep commands of the control surfaces provided the excitation of the aircraft structure. The most important results of the in-flight modal analysis are presented and discussed in this paper.
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This study aims at the attenuation of the unsteady fluctuations along a two-dimensional mixing layer which may be considered as a prototypical problem for the evaluation of estimation and control techniques, and also a canonical p...
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This study aims at the attenuation of the unsteady fluctuations along a two-dimensional mixing layer which may be considered as a prototypical problem for the evaluation of estimation and control techniques, and also a canonical problem, when compressibility is considered, for sound radiation by low-Reynolds-number free shear flows. Two strategies are proposed for the estimation of the time evolution of wavepackets based on upstream data of the simulation: a Parabolised-stability-equation (PSE) based transfer function between two positions and an empirical-transfer-function identification technique, which relies on the theoretical background established by the PSE. Both techniques present a similar performance for prediction of the fluctuations between streamwise-separated input and output positions. Furthermore, the identification method is used to determine the response of the flow to a body force actuation which allows for the elaboration of a Feedforward control framework for the fluctuations via a phase-opposition actuation. This strategy, which is evaluated with three different control laws, presents encouraging results both for the linearized system (i.e. described in terms of transfer functions) and for the non-linear, direct numerical simulation of the mixing layer, in which significant delays of vortex pairing are observed. The established framework is thus seen as a promising technique for real-time flow control aiming at the attenuation of wavepackets, and the corresponding reduction of the radiated sound.
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摘要 :
This study aims at the attenuation of the unsteady fluctuations along a two-dimensional mixing layer which may be considered as a prototypical problem for the evaluation of estimation and control techniques, and also a canonical p...
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This study aims at the attenuation of the unsteady fluctuations along a two-dimensional mixing layer which may be considered as a prototypical problem for the evaluation of estimation and control techniques, and also a canonical problem, when compressibility is considered, for sound radiation by low-Reynolds-number free shear flows. Two strategies are proposed for the estimation of the time evolution of wavepackets based on upstream data of the simulation: a Parabolised-stability-equation (PSE) based transfer function between two positions and an empirical-transfer-function identification technique, which relies on the theoretical background established by the PSE. Both techniques present a similar performance for prediction of the fluctuations between streamwise-separated input and output positions. Furthermore, the identification method is used to determine the response of the flow to a body force actuation which allows for the elaboration of a Feedforward control framework for the fluctuations via a phase-opposition actuation. This strategy, which is evaluated with three different control laws, presents encouraging results both for the linearized system (i.e. described in terms of transfer functions) and for the non-linear, direct numerical simulation of the mixing layer, in which significant delays of vortex pairing are observed. The established framework is thus seen as a promising technique for real-time flow control aiming at the attenuation of wavepackets, and the corresponding reduction of the radiated sound.
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The paper discusses an unmanned aerial vehicle (UAV) trajectory planning tool that assesses areas in an urban environment with respect to Global Navigation Satellite Systems (GNSS) availability, separation to obstacles, energy exp...
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The paper discusses an unmanned aerial vehicle (UAV) trajectory planning tool that assesses areas in an urban environment with respect to Global Navigation Satellite Systems (GNSS) availability, separation to obstacles, energy expanded, and impact of wind. The tool determines what areas of the urban environment are navigable, i.e., where does have GNSS sufficient performance (accuracy, integrity, availability, and continuity) to support safe collision-free operation. The tool, furthermore, uses the input from sensors located throughout the city to estimate the local wind field. Based on the wind field and safe navigation areas, both an energy-based cost function and a speed adjustment scheme are adopted to determine the best, in terms of energy usage, trajectory from origin to destination. Preliminary results show that up to 18% of energy savings while navigating at a safe distance from the buildings.
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