Modern urban reconnaissance missions dictate the need for a MicroAirVehicle (MAV) platform capable of performing a complex mission : rapid and efficient ingress to a target location followed by slow loiter for quality image capture. This may be achieved using a tilt-body fixed-wing vehicle which combines the speed, range, and gust-hardiness of a fixed wing with the loiter and precision capability of a rotorcraft vehicle.
A hybrid dynamic model for bio-inspired robots with soft appendages - Application to a bio-inspired flexible flapping-wing microairvehicle.
Mathieu POREZ, Frédéric BOYER and Ayman BELKHIRI
Abstract— The paper deals with the dynamic modeling of bio-inspired robots with soft appendages as flying insect-like or swimming fish-like robots. In order to model such soft systems, we here propose to exploit the Mobile Multibody System framework introduced in , , . In such a framework, the robot is considered as a tree-like structure of rigid bodies whose the joint evolution is governed by stress-strain laws or control torques. Based on the Newton-Euler formulation of these systems, we propose a new algorithm able to compute at each step of a time loop both the net and passive joint accelerations along with the control torques supplied by the motors. For the purpose of illustration, following our works begun in , the proposed algorithm is applied to the simulation of the hovering flight of a soft flapping-wing insect-like robot (see the video at ).
The developed control scheme avoided the issues with singularities and was found to perform with good results for the control objective, as shown in the simulations and real-time results.
Future works include the use of this strategy for aerial manipulation tasks.
Supplementary Materials: The following are available online at: www.mdpi.com/2076-3417/7/1/13/s1, Video S1: Passivity-Based Control for a MicroAirVehicle Using Unit Quaternions.
Future work will focus on a prototype maintained within a fixed frame and allowed to rotate on a growing number of degrees of freedom.
I want to thank the foundation STAE / RTRA who contribute to this project in the project EMMAV (Electro for Morphing MicroAirVehicle). I would also like to thank the technical staff of the department of aerodynamics ISAE, especially Remy Chanton without whom, this study would not have been possible.
The optimisation of the kinematics of a two-dimensional flapping airfoil is carried out numerically for a small value of the Reynolds number. The main goal is to identify flapping parameters capable to ensure high aerodynamic performances for a microairvehicle application. Attention is focused on the lift and thrust forces and on the propulsive efficiency developed from the flapping motion. The control variables are the amplitudes of the combined motions of heaving and pitching and the phase angle between them. Additionally, the flapping frequency and the mean angle of attack are considered. The goals are, first, to find the optimal kinematics of the wing, and, second, to link these optimal configurations to observations in nature of animals using flapping motion for their locomotion, such as birds, insects and fish. Once achieved, the numerical optimisation may be seen as a proof that animals’ motion is naturally optimised for their environments and the various conditions they encounter. The methodology is based on the solution of the flow field around a NACA0012 airfoil submitted to translational and angular oscillations. Then, the gradients of the cost functional with respect to the control parameters are evaluated thanks to the sensitivity technique and the complex step derivative method. These two ap- proaches of optimisation can be linked to one another by simple examination of the equations corresponding to real and complex variables. The gradients are subse- quently used in a quasi-Newton update algorithm to direct the solution towards its optimal value.
ABSTRACT: The growing interest of rotary wing UAVs, for military and civilian applications, has encouraged designers to consider miniaturized configurations, more efficient in terms of endurance, payload capability and maneuverability. The purpose of this paper is to study a new configuration of coaxial rotor as applied to a micro aerial vehicle (MAV) with the intention to guarantee the vehicle maneuverability while removing unnecessary control surfaces which would increase wind gust sensitivity. Coaxial rotor configurations maximize the available rotor disk surface and allow for torque cancelation. Tilting rotors may allow for the vehicle control.
Miniaturizing MAVs requires satisfying stringent mass constraints as well as simple mechanisms which can be downscaled. Because it cancel the resulting torque and takes full advantage of the available disk surface, coaxial configurations have attracted the designers attention within the MAV community (A.P.K. Hall et al. ). Instead of resorting to swashplate cyclic pitch mechanisms which are fragile and difficult to miniaturize, the present study investigate tilting rotors as a control mode. The potential benefit from that kind of control is to get rid of any unnecessary control surface which would make the vehicle more sensitive to crosswinds. Eventually, the tilting mechanism shall be replaced by electroactive polymer actuators instead of the present servos. The present paper aims at studying a modified version of a conventional counter rotating coaxial rotor in which rotors may be tilted in order to create drift forces and moments potentially usable for maneuverability. In the presented prototype, the direction of the thrust of the two rotors can be redirected by tilting propellers laterally and longitudinally. A theoretical model of the mechanism has been developed based on a mechanical model which includes forces, moments and gyroscopic effects induced by the rotating parts (Fig. 1, left). A simple coaxial model due to G. Leishman [2,3] has been implemented in order to account for both mechanical and aerodynamic effects. In addition to the theoretical approach, an experimental setup has been developed. It is based on 5-component balance (Fig. 1, right) holding the coaxial system from above. For the present study only quasi-static measurements have been done. That configuration allows evaluating the forces and moments created by the many combinations of input parameters of the system. In this case, we also conduct a vibration analysis system in parallel configuration rotors. The experimental system has 6 inputs (Double angle control of the two rotors, and rotational speed control of the two motors) and 12 outputs (2 forces Fy / Fz, 3 torques Mx / My / Mz, the rotational speeds of the two rotors the voltage and current of the two motors, pressure and temperature). The rotors are regulated by a speed controller, and the rotors incidence is controlled via four servomotors, calibrated to + / - 0.1 °.
Designing a silent rotor goes through an aeroacoustic optimization, which implies under- standing the aerodynamic phenomena responsible for noise generation. Predicting the noise generated aerodynamically is relatively straightforward once detailed aerodynamics involved in the propulsion system is available through the use of direct noise computation or hybrid prediction. Aeroacoustic investigations 1–3 or optimizations in that framework are possible 4,5 but demanding in terms of computational cost, hence not realistic in an industrial context. To this aim, lower-fidelity tools are needed. Such models based on analytical developments seem promising 6 although generally found in small axial fans research. A pure aerodynamic optimization of micro-airvehicle (MAV) propellers has been published by Gur and Rosen 7 but an optimization based on both aerodynamic and acoustic characteristics has rarely been addressed although some noise reduction techni- ques were applied yielding promising conclusions such as an unequal blade spacing to reduce the tonal noise, 8 boundary layer trips 9 or trailing-edge serrations 10 to remove the broadband noise. In these earlier studies, the sound was considered as mainly tonal with a broadband contribution due to the scattering of boundary layer perturbations by the blade trailing edge. The tonal part is limited to the steady loading noise as inflow dis- tortions that are due to installation effects and inflow conditions are generally difficult to determine. The present contribution introduces an original methodology 11 for reducing the noise of MAV rotors while preserving or even increasing the endurance and this approach is suited for engineering purposes, from aerodynamic and acoustic prediction to shape optimization. A similar strategy has been followed by Wisniewski et al. 12 and Zawodny et al. 13 but the models used were based on empirical data at relatively high Reynolds numbers and for symmetrical foils while analytical models are proposed and justified in the present study. From the results yielded by the optimization and compar- ison with measurements, backed-up with experimental and numerical further investiga- tions, a new ranking of the noise sources in low Reynolds number rotors in hover is proposed. The paper outlines the following organization: an optimization accounting for aerodynamic power and tonal and broadband (trailing edge) acoustic components, an experimental investigation on the optimized rotor that highlighted the importance of turbulence interaction noise, investigations with numerical simulations to calibrate the modelling of the turbulence interaction noise and eventually to propose further noise reduction designs.
Microair vehicles with transitioning flight capabilities, or simply hybrid microair vehicles, combine the beneficial features of fixed-wing configurations, in terms of endurance, with vertical take-off and landing capabilities of rotorcrafts to perform five different flight phases during typical missions, such as vertical takeoff, transitioning flight, forward flight, hovering and vertical landing. This promising microairvehicle class has a wider flight envelope than conventional microair vehicles, which implies new challenges for both control community and aerodynamic designers. One of the major challenges of hybrid microair vehicles is the fast variation of aerodynamic forces and moments during the transition flight phase which is difficult to model accurately. To overcome this problem, we propose a flight control architecture that estimates and counteracts in real-time these fast dynamics with an intelligent feedback controller. The proposed flight controller is designed to stabilize the hybrid microairvehicle attitude as well as its velocity and position during all flight phases. By using model-free control algorithms, the proposed flight control architecture bypasses the need for a precise hybrid microairvehicle model that is costly and time consuming to obtain. A comprehensive set of flight simulations covering the entire flight envelope of tailsitter microair vehicles is presented. Finally, real-world flight tests were conducted to compare the model-free control performance to that of the Incremental Nonlinear Dynamic Inversion controller, which has been applied to a variety of aircraft providing effective flight performances.
We observed that both scholars and enterprises look at multi-level distribution systems as an effective solution to efficiently deliver goods in cities while preserving urban livability. However, this line of research is still recent and focuses on simplified frameworks, that usually do not represent real life situation. Synchronization among levels, for example, starts to be studied nowadays and room is left for future research. Furthermore, the multi- trip aspect that is a natural consequence of the eco-friendly vehicle usage is not considered in several papers. Last, but not the least, time-dependency has not been addressed yet from an algorithmic point of view when studying multi-level distribution systems. We strongly believe that efficient solutions can be found only integrating this feature in future models, due to the relation between time and traveling speed variation that characterizes routing in cities. Moreover, the distribution scheme based on city distribution centers (CDCs) located on the outskirts of the city can lead to original multi-trip vehicle routing problems where a vehicle can start at a given CDC and finish at another one. This organization can be done in conjunction with TSPs that move goods among CDCs.
A second area of research is oriented towards the concept of “intelligent road”. The idea is to enable vehicles to seamlessly gather information from any combination of signs, displays, sensors, and transponders.
In the first section, we will describe vehicle-to-roadside communications. We will notably examine how vehicles can gain “intelligence” from highways, roads, and streets. In the second section, we will present vehicle-to-vehicle communications. We will notably discuss some of the applications that can be promoted by this type of communications.
For field personnel, it is imperative to reduce the com- plexity of operating a robot, such as a MAV, which is used
primarily for the purpose of exploring an unknown environ- ment. Operators are under high workload, with their atten- tion divided between many tasks, and their goal is to obtain imagery (i.e., ISR missions), not to fly the vehicle. A solution is to make the control system simpler by reducing the order of the feedback loop to a position-based, zero-order control system, which require less attention and SA than higher- order systems, as well as significantly less training. However, for the precision positioning and orientation required to obtain eﬀective imagery in an ISR mission, position-based, zero-order control systems can be cumbersome and diﬃcult to use. While, in theory, they are safer and less prone to error, unwieldy zero-order control interfaces have impaired many teams at USAR competitions [ 20 ] and participants in Durlach et al.’s study [ 12 ]. Unfortunately, providing a velocity-based, 1st-order interface to a MAV operator can cause operator control instabilities (e.g., pilot-induced oscillations), as also demonstrated by the Durlach et al. study [ 12 ]. In addition, for field personnel controlling a MAV, the environmental pressures of a hostile setting, the need for formal and extensive training, and the issue of divided attention suggest that any type of rate-control systems are not appropriate [ 11 ]. As such, some balance between using position-based, zero-order and rate-based, higher- order control is warranted in these scenarios to optimize an operator’s performance.
Les enjeux qui concernent les cultures minoritaires en milieu occidental moderne sont nombreux et complexes. Comment concilier la permanence de certaines identités marginales, périphériques, avec les exigences qu’entrainent les phénomènes d’industrialisation, d’américanisation et de mondialisation de la culture de masse? L’Acadie fait partie des petites cultures qui furent, au vingtième siècle, confrontées à un double mouvement contradictoire menaçant leur identité : le repli identitaire (valorisation d’un modèle traditionnel d’existence, refus de l’autre, peur de l’assimilation, etc.) et la rupture radicale avec les spécificités culturelles (perte de la langue commune minoritaire, révolte contre le communautarisme étouffant, fuite et exode, etc.). Parmi les différents acteurs qui s’investirent dans les débats sur la modernisation de l’Acadie comme entité culturelle vivante, le poète Gérald Leblanc fut l’un de ceux dont le projet est des plus originaux et significatifs. En effet, entre l’assimilation pure et simple à la majorité de langue anglaise et le repli identitaire qui brime le développement de la société enfermée dans une vision passéiste d’elle-même, Leblanc fonde une réflexion qui transcende les extrêmes. En ce sens, son œuvre peut s’analyser à la lumière des théories de Michael Cronin sur le micro-cosmopolitisme. Nous tenterons par le présent travail de cerner certains éléments qui justifient cette position.
2.0 GAVIA as a Pipeline Inspection Vehicle
The GAVIA vehicle currently housed at the Institute for Ocean Technology was purchased through a joint venture between the NRC Institute for Ocean
Technology (IOT) and the NRC Institute for Research in Construction (IRC) in Ottawa. The purpose of the vehicle in this application is to inspect freshwater piping systems. Throughout North America, aging infrastructure in many major cities has created a need for internal inspection of these concrete pipes, while in service. The goal of this work is to develop a vehicle, based on the GAVIA platform, to carry the required sensors through these pipes, identify areas that need attention and do so without interrupting or contaminating the fresh water supply of the city.
Very little research exists specifically on operator inter- action with MAV. Durlach et al. completed a study in 2008 which examined training MAVs operators to perform ISR missions in a simulated environment [ 12 ]. Operators were taught to fly a simulated Honeywell RQ-16 MAV with either a mouse or game controller. Although Durlach et al. state that they limited the simulated MAV to a maximum velocity of six kilometers/second (km/s), the vehicle was fly-by-wire, with stabilized yaw, pitch, and roll axes to maintain balanced flight, which participants could only crash by colliding with other objects in the simulation. No mention was made as to the incorporation of video/communication delay. The study specifically looked at whether discrete or continuous input teleoperation controls yielded better performance using two di ﬀerent two interfaces.
With applications such as safety on the road, ad hoc vehic- ular networks and vehicle-to-vehicle are receiving increasing attention (see recent survey in ). Vehicular DTNs (Delay Tolerant Networks, i.e., networks in which end-to-end paths may not exist and communication routes may only be available through mobility and accumulation over time) have thus been considered in recent studies, and various analytical models have been proposed. The papers ,  focus on information propagation speed in one-dimensional vehicle-to-vehicle with constant speeds in each direction. In  the authors introduce
1.4.4. Conditions opératoires de micro-fraises du commerce Les conditions de coupe en micro-fraisage sont essentielles pour le bon déroulement de l’usinage. En effet, les micro-outils ne peuvent pas supporter des efforts supérieurs à quelques dizaines de newtons sous peine de casser. Une comparaison des conditions préconisées par certains fabricants d’outils pour des aciers exhibant une dureté comprise entre 50 et 60 HRC est présentée sur la Figure 1-16. On voit nettement que les conditions sont directement proportionnelles au diamètre de l’outil, mis à part la vitesse de coupe qui reste constante. En comparant ces préconisations, on remarque que les fabricants proposent des conditions menant à une variation du débit copeau d’un rapport 5. Certains de ces fabricants prônent ainsi des conditions beaucoup plus conservatrices. Ces conditions différentes suivant le fabricant ne sont pas forcément optimisées en termes d’usure, de durée de vie ou de productivité pour l’usage fait par l’opérateur.