Transient aerodynamics effect on v-tail aircraft in lateral stability

The trend in applying unconventional aircraft configurations for aerodynamic efficiency has caused some problems in flight dynamics especially in aircraft stability. Although, the mathematical modelling of flight dynamics has been established, however the accuracy of aerodynamic data, normally in the form of aerodynamic derivatives may affect the actual motion responses of the aircraft in design process for stability and control simulation. The aerodynamic derivatives may differ from small to large aircraft motion amplitude and may also vary in transient conditions. Clear that it is important to establish methods in estimating the aerodynamic derivatives accurately. This research work presents the effort in introducing a reliable method in estimating the aerodynamic derivative for V-tail aircraft in lateral motions focusing on Dutch roll mode using wind tunnel testing technique. Two methods of estimation are presented, first the steady-state measurement by static wind tunnel test and second transient measurement by dynamic oscillatory test. CAMAR UTMUAV has been used in this study for several V-tail configurations with dihedral angles of 35°, 47°, 55° (later use V35, V47, V55 respectively) including a conventional tail for reference. In static wind tunnel test, the static derivatives of C?ß and C?ß were measured for different tail configurations within ±25° yaw angle with range of wind speed from 10 m/s to 40 m/s. Meanwhile in dynamic oscillatory test, the transient condition was simulated at range of reduced frequencies, ?m of 0.05 - 0.25 by varying oscillation frequency through various spring stiffness, ?s. Hence, the dynamic oscillatory test was measured within yaw angle (±10°). Static wind tunnel test results showed that within ±10° yaw angle, all configurations possess positive yaw stability. When compare with conventional tail, found that V47 and V55 have higher degree of stability except for V35. For yaw angles more than ±10°, the Vtail showed better stability as it reaches neutral stability later than the conventional tail. However, measurements by static wind tunnel tests indicated there are discrepancies in representing the derivatives during transient condition and unable to measure dynamic derivatives of C?r and C?r. Meanwhile, aerodynamic derivatives of C?ß , C?ß, C?r and C?r were measured in the dynamic oscillatory test. The result from the dynamic oscillatory test are then compared with static wind tunnel test results and presented in the form of amplification factor. Within tested reduced frequencies, C?ß measured dynamically for all Vtail are more than static measured (amplification factor more than unity). This factor highlights the existence of the transient effects in the estimation of aerodynamic derivatives where it indicated the steady-state measurement underestimated the derivatives. At the same time, the steady-state derivative has also overestimated the aerodynamic damping in Dutch Roll simulation with crosswind input about 50%-90% depending on tail configurations. Meanwhile, through dynamic simulation using state-space equation of Dutch roll motion resulted the V55 has a higher sensitivity in response to crosswind followed by V47 and V35 respectively

Transient aerodynamics effect on v-tail aircraft in lateral stability

The trend in applying unconventional aircraft configurations for aerodynamic efficiency has caused some problems in flight dynamics especially in aircraft stability. Although, the mathematical modelling of flight dynamics has been established, however the accuracy of aerodynamic data, normally in the form of aerodynamic derivatives may affect the actual motion responses of the aircraft in design process for stability and control simulation. The aerodynamic derivatives may differ from small to large aircraft motion amplitude and may also vary in transient conditions. Clear that it is important to establish methods in estimating the aerodynamic derivatives accurately. This research work presents the effort in introducing a reliable method in estimating the aerodynamic derivative for V-tail aircraft in lateral motions focusing on Dutch roll mode using wind tunnel testing technique. Two methods of estimation are presented, first the steady-state measurement by static wind tunnel test and second transient measurement by dynamic oscillatory test. CAMAR UTMUAV has been used in this study for several V-tail configurations with dihedral angles of 35°, 47°, 55° (later use V35, V47, V55 respectively) including a conventional tail for reference. In static wind tunnel test, the static derivatives of C?ß and C?ß were measured for different tail configurations within ±25° yaw angle with range of wind speed from 10 m/s to 40 m/s. Meanwhile in dynamic oscillatory test, the transient condition was simulated at range of reduced frequencies, ?m of 0.05 - 0.25 by varying oscillation frequency through various spring stiffness, ?s. Hence, the dynamic oscillatory test was measured within yaw angle (±10°). Static wind tunnel test results showed that within ±10° yaw angle, all configurations possess positive yaw stability. When compare with conventional tail, found that V47 and V55 have higher degree of stability except for V35. For yaw angles more than ±10°, the Vtail showed better stability as it reaches neutral stability later than the conventional tail. However, measurements by static wind tunnel tests indicated there are discrepancies in representing the derivatives during transient condition and unable to measure dynamic derivatives of C?r and C?r. Meanwhile, aerodynamic derivatives of C?ß , C?ß, C?r and C?r were measured in the dynamic oscillatory test. The result from the dynamic oscillatory test are then compared with static wind tunnel test results and presented in the form of amplification factor. Within tested reduced frequencies, C?ß measured dynamically for all Vtail are more than static measured (amplification factor more than unity). This factor highlights the existence of the transient effects in the estimation of aerodynamic derivatives where it indicated the steady-state measurement underestimated the derivatives. At the same time, the steady-state derivative has also overestimated the aerodynamic damping in Dutch Roll simulation with crosswind input about 50%-90% depending on tail configurations. Meanwhile, through dynamic simulation using state-space equation of Dutch roll motion resulted the V55 has a higher sensitivity in response to crosswind followed by V47 and V35 respectively

Commande référencée vision pour drones à décollages et atterrissages verticaux

La miniaturisation des calculateurs a permis le développement des drones, engins volants capable de se déplacer de façon autonome et de rendre des services, comme se rendre clans des lieux peu accessibles ou remplacer l'homme dans des missions pénibles. Un enjeu essentiel dans ce cadre est celui de l'information qu'ils doivent utiliser pour se déplacer, et donc des capteurs à exploiter pour obtenir cette information. Or nombre de ces capteurs présentent des inconvénients (risques de brouillage ou de masquage en particulier). L'utilisation d'une caméra vidéo dans ce contexte offre une perspective intéressante. L'objet de cette thèse était l'étude de l'utilisation d'une telle caméra dans un contexte capteur minimaliste: essentiellement l'utilisation des données visuelles et inertielles. Elle a porté sur le développement de lois de commande offrant au système ainsi bouclé des propriétés de stabilité et de robustesse. En particulier, une des difficultés majeures abordées vient de la connaissance très limitée de l'environnement dans lequel le drone évolue. La thèse a tout d'abord étudié le problème de stabilisation du drone sous l'hypothèse de petits déplacements (hypothèse de linéarité). Dans un second temps, on a montré comment relâcher l'hypothèse de petits déplacements via la synthèse de commandes non linéaires. Le cas du suivi de trajectoire a ensuite été considéré, en s'appuyant sur la définition d'un cadre générique de mesure d'erreur de position par rapport à un point de référence inconnu. Enfin, la validation expérimentale de ces résultats a été entamée pendant la thèse, et a permis de valider bon nombre d'étapes et de défis associés à leur mise en œuvre en conditions réelles. La thèse se conclut par des perspectives pour poursuivre les travaux.The computers miniaturization has paved the way for the conception of Unmanned Aerial vehicles - "UAVs"- that is: flying vehicles embedding computers to make them partially or fully automated for such missions as e.g. cluttered environments exploration or replacement of humanly piloted vehicles for hazardous or painful missions. A key challenge for the design of such vehicles is that of the information they need to find in order to move, and, thus, the sensors to be used in order to get such information. A number of such sensors have flaws (e.g. the risk of being jammed). In this context, the use of a videocamera offers interesting prospectives. The goal of this PhD work was to study the use of such a videocamera in a minimal sensors setting: essentially the use of visual and inertial data. The work has been focused on the development of control laws offering the closed loop system stability and robustness properties. In particular, one of the major difficulties we faced came from the limited knowledge of the UAV environment. First we have studied this question under a small displacements assumption (linearity assumption). A control law has been defined, which took performance criteria into account. Second, we have showed how the small displacements assumption could be given up through nonlinear control design. The case of a trajectory following has then been considered, with the use of a generic error vector modelling with respect to an unknown reference point. Finally, an experimental validation of this work has been started and helped validate a number of steps and challenges associated to real conditions experiments. The work was concluded with prospectives for future work.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Recent Progress in Some Aircraft Technologies

The book describes the recent progress in some engine technologies and active flow control and morphing technologies and in topics related to aeroacoustics and aircraft controllers. Both the researchers and students should find the material useful in their work

Development of a dynamic model of a ducted fan VTOL UAV

The technology of UAV (Unmanned Aerial Vehicle) has developed since its conception many years ago. UAVs have several features such as, computerised and autonomous control without the need for an on-board pilot. Therefore, there is no risk of loss of life and they are easier to maintain than manned aircraft. In addition, UAVs have an extended range/endurance capability, sometimes for several days. This makes UAVs attractive for missions that are typically "dull, dirty and dangerous". With the development of technology, the application of UAVs is becoming commonplace for both military and civil missions. Examples of this are reconnaissance, surveillance, environmental monitoring, disaster observation, etc. The School of Aerospace, Mechanical and Manufacturing Engineering (SAMME) at RMIT University has designed a novel concept for a ducted-fan UAV with vertical takeoff and landing capability and the option to transition to horizontal flight. The aerodynamic analysis, preliminary and detailed design, of this ducted-fan VTOL UAV, is the first and most important step. To optimize the aerodynamic characteristics, evaluating aerodynamic coefficients and analyzing the flow patterns around the vehicle at different speeds and angles of attack is necessary. In this project, CFD plays an important role in predicting the longitudinal and lateral stability and control characteristics of a full-scale model of ducted fan VTOL UAV at both vertical and horizontal flight without any prior knowledge of existing wind tunnel or flight test data. Prior to carrying out experiments in the wind tunnel, the manufacture of ducted fan VTOL UAV was focused on. Particular attention was paid to the propulsion system as the key point. The full-scale model of UAV was produced using the Rapid Prototyping Facility at SAMME to ensure its accurate geometric shape for testing in the wind tunnel. The experiments of the full-scale UAV model with engines was conducted in RMIT's Industrial Wind Tunnel where its aerodynamic characteristics and its properties of counter-rotating propulsion system were tested. In addition, the correlation between experimental data and CFD results was evaluated and the accuracy of the dynamic model of ducted fan VTOL UAV was improved. Flight dynamics is concerned with the motion of an aircraft due to internally or externally generated forces. The ducted fan VTOL UAV stability and control derivatives are determined and used as a basis in a flight simulation environment. This simulation showed that the vehicle is stable and controllable for a range of flight speeds. Finally, a MIMO linear control system was designed to control the vehicle in hovering and low-speed slide flight. The real-time simulation and modeling in MATLAB combined with a flight-simulator showed several animations and trajectories of UAV missions with or without crosswind effect during flight. These simulations were very helpful in determining the dynamic behaviour of the vehicle under various flight conditions