Stratégies de guidage visuel bio-inspirées : application à la stabilisation visuelle d’un micro-drone et à la poursuite de cibles

Insects, like hoverflies are able of outstanding performances to avoid obstacles, reject disturbances and hover or track a target with great accuracy. These means that fast sensory motor reflexes are at work, even if they are minimalist, they are perfectly optimized for the flapping flight at insect scale. Additional refined mechanisms, like gaze stabilization relative to the body, allow to increase their flight capacity.In this PhD thesis, we present the design of a quadrotor, which is highly similar to an insect in terms of perception (visual system) and implements a bio-inspired gaze control system through the mechanical decoupling between the body and the visual system. The design of the quadrotor (open-source), itspilot and its decoupled eye are thoroughly detailed. New visual processing algorithms make it possible to faithfully track a moving target, in spite of a very limited number of pixels (only 24 pixels). Using this efficient gaze stabilization, we developed new strategies to stabilize the robot above a target and finely control its position relative to the target. These new strategies do not need classical aeronautic sensors like accelerometers and magnetometers. As a result, the quadrotor is able to take off, move and land automatically using only its embedded rate-gyros, its insect-like eye, and an altitude measurement. All these experiments were validated in a flying arena equipped with a VICON system. Finally, we describe a new toolbox, called RT-MaG toolbox, which generate automatically a real-time standalone application for Linux systems from a Matlab/Simulink model (http://www.gipsalab.fr/projet/RT-MaG/). These make it possible to simulate, design control laws and monitor the robot’s flight in real-time using only Matlab/Simulink. As a result, the "time-to-flight" is considerably reduced and the final application is highly reconfigurable (real-time monitoring, parameter tuning, etc.).Les insectes sont capables de prouesses remarquables lorsqu’il s’agit d’éviter des obstacles,voler en environnement perturbé ou poursuivre une cible. Cela laisse penser que leurs capacités de traitement, aussi minimalistes soient-elles, sont parfaitement optimisées pour le vol. A cela s’ajoute des mécanismes raffinés, comme la stabilisation de la vision par rapport au corps, permettant d’améliorer encore plus leurs capacités de vol.Ces travaux de thèse présentent l’élaboration d’un micro drone de type quadrirotor, qui ressemble fortement à un insecte sur le plan perceptif (vibration rétinienne) et reprend des points structurels clés, tels que le découplage mécanique entre le corps et le système visuel. La conception du quadrirotor (de type open-source), son pilotage automatique et son système occulo-moteur sont minutieusement détaillés.Des traitements adaptés permettent, malgré un très faible nombre de pixels (24 pixels seulement), de poursuivre finement du regard une cible en mouvement. A partir de là, nous avons élaboré des stratégies basées sur le pilotage par le regard, pour stabiliser le robot en vol stationnaire, à l’aplomb d’une cible et asservir sa position ; et ce, en se passant d’une partie des capteurs habituellement utilisés en aéronautique tels que les magnétomètres et les accéléromètres. Le quadrirotor décolle, se déplace et atterrit de façon autonome en utilisant seulement ses gyromètres, son système visuel original mimant l’oeil d’un insecte et une mesure de son altitude. Toutes les expérimentations ont été validées dans une arène de vol, équipée de caméras VICON.Enfin, nous décrivons une nouvelle toolbox qui permet d’exécuter en temps réel des modèles Matlab/Simulink sur des calculateurs Linux embarqués de façon complètement automatisée (http://www.gipsalab.fr/projet/RT-MaG/). Cette solution permet d’écrire les modèles, de les simuler, d’élaborer des lois de contrôle pour enfin, piloter en temps réel, le robot sous l’environnement Simulink. Cela réduit considérablement le "time-to-flight" et offre une grande flexibilité (possibilité de superviser l’ensemble des données de vol, de modifier en temps réel les paramètres des contrôleurs, etc.)

Bio-Inspired Hovering Control for an Aerial Robot Equipped with a Decoupled Eye and a Rate Gyro

International audienceThis work provides an hovering control strategy for a sighted robot, the eye of which being decoupled from the body and controlled by means of a tiny rotative piezo motor. The main purpose of this paper is to show the effectiveness and the efficiency of this fundamental bio-inspired mechanical decoupling. Indeed, it exhibits several benefits: * it enables to stabilize the robot's gaze on the basis of three bio-inspired oculomotor reflexes (ORs) : a visual fixation reflex (VFR), a translational and rotational vestibulo- ocular reflexes (tVOR and rVOR), * the eye can better, quickly and accurately compensate for sudden, untoward disturbances caused by the vagaries of the supporting head or body, * it yields a reference visual signal that can be used to unbias the rate gyro used to implement the VORs and to stabilize the hovering robot, * it increases the tracking accuracy with moving targets compared to without OR, This paper shows also that lateral disturbances are rejected 2 times faster with the decoupled eye robot, and roll perturbations induce a retinal error 20 times smaller. The occulomotor reflexes enables to cancel retinal error 6 times faster with 5 times lower retinal error picks. The conclusion of the paper is that decoupled eye must be considered as an efficient autonomous flight solution

Decoupling the Eye: A Key toward a Robust Hovering for Sighted Aerial Robots

International audienceInspired by natural visual systems where gaze stabilization is at a premium, we simulated an aerial robot with a decoupled eye to achieve more robust hovering above a ground target despite strong lateral and rotational disturbances. In this paper, two different robots are compared for the same disturbances and displacements. The first robot is equipped with a fixed eye featuring a large field-of-view (FOV) and the second robot is endowed with a decoupled eye featuring a small FOV (about ±5°). Even if this mechanical decoupling increases the mechanical complexity of the robot, this study demonstrates that disturbances are rejected faster and the computational complexity is clearly decreased. Thanks to bio-inspired visuo-motor reflexes, the decoupled eye robot is able to hold its gaze locked onto a distant target and to reject strong disturbances by profiting of the small inertia of the decoupled eye

Novel Hyperacute Gimbal Eye for Implementing Precise Hovering and Target Tracking on Board a Quadrotor

International audienceThis paper presents a new minimalist bio-inspired artificial eye of only 24 pixels, able to locate accurately a target placed in its small field of view (10°). The eye is mounted on a very light custom-made gimbal system which makes the eye able to track faithfully a moving target. We have shown here, that our gimbal eye can be embedded onboard a small quadrotor to achieve accurate hovering with respect to a target placed onto the ground. Our aiborne oculomotor system was enhanced with a bio-inspired reflexe in charge to lock efficiently the robot’s gaze onto a target and compensate for the robot’s rotations and disturbances. The use of very few pixels allowed to implement a visual processing algorithm at a refresh rate as high as such as 400 Hz. This high refresh rate coupled to a very fast control of the eye’s orientation allowed the robot to track efficiently a target moving at a speed up to 200°/s

Strategies for bio-inspired visual guidance : application to control an UAV and to track a target

Les insectes sont capables de prouesses remarquables lorsqu’il s’agit d’éviter des obstacles,voler en environnement perturbé ou poursuivre une cible. Cela laisse penser que leurs capacités de traitement, aussi minimalistes soient-elles, sont parfaitement optimisées pour le vol. A cela s’ajoute des mécanismes raffinés, comme la stabilisation de la vision par rapport au corps, permettant d’améliorer encore plus leurs capacités de vol.Ces travaux de thèse présentent l’élaboration d’un micro drone de type quadrirotor, qui ressemble fortement à un insecte sur le plan perceptif (vibration rétinienne) et reprend des points structurels clés, tels que le découplage mécanique entre le corps et le système visuel. La conception du quadrirotor (de type open-source), son pilotage automatique et son système occulo-moteur sont minutieusement détaillés.Des traitements adaptés permettent, malgré un très faible nombre de pixels (24 pixels seulement), de poursuivre finement du regard une cible en mouvement. A partir de là, nous avons élaboré des stratégies basées sur le pilotage par le regard, pour stabiliser le robot en vol stationnaire, à l’aplomb d’une cible et asservir sa position ; et ce, en se passant d’une partie des capteurs habituellement utilisés en aéronautique tels que les magnétomètres et les accéléromètres. Le quadrirotor décolle, se déplace et atterrit de façon autonome en utilisant seulement ses gyromètres, son système visuel original mimant l’oeil d’un insecte et une mesure de son altitude. Toutes les expérimentations ont été validées dans une arène de vol, équipée de caméras VICON.Enfin, nous décrivons une nouvelle toolbox qui permet d’exécuter en temps réel des modèles Matlab/Simulink sur des calculateurs Linux embarqués de façon complètement automatisée (http://www.gipsalab.fr/projet/RT-MaG/). Cette solution permet d’écrire les modèles, de les simuler, d’élaborer des lois de contrôle pour enfin, piloter en temps réel, le robot sous l’environnement Simulink. Cela réduit considérablement le "time-to-flight" et offre une grande flexibilité (possibilité de superviser l’ensemble des données de vol, de modifier en temps réel les paramètres des contrôleurs, etc.).Insects, like hoverflies are able of outstanding performances to avoid obstacles, reject disturbances and hover or track a target with great accuracy. These means that fast sensory motor reflexes are at work, even if they are minimalist, they are perfectly optimized for the flapping flight at insect scale. Additional refined mechanisms, like gaze stabilization relative to the body, allow to increase their flight capacity.In this PhD thesis, we present the design of a quadrotor, which is highly similar to an insect in terms of perception (visual system) and implements a bio-inspired gaze control system through the mechanical decoupling between the body and the visual system. The design of the quadrotor (open-source), itspilot and its decoupled eye are thoroughly detailed. New visual processing algorithms make it possible to faithfully track a moving target, in spite of a very limited number of pixels (only 24 pixels). Using this efficient gaze stabilization, we developed new strategies to stabilize the robot above a target and finely control its position relative to the target. These new strategies do not need classical aeronautic sensors like accelerometers and magnetometers. As a result, the quadrotor is able to take off, move and land automatically using only its embedded rate-gyros, its insect-like eye, and an altitude measurement. All these experiments were validated in a flying arena equipped with a VICON system. Finally, we describe a new toolbox, called RT-MaG toolbox, which generate automatically a real-time standalone application for Linux systems from a Matlab/Simulink model (http://www.gipsalab.fr/projet/RT-MaG/). These make it possible to simulate, design control laws and monitor the robot’s flight in real-time using only Matlab/Simulink. As a result, the "time-to-flight" is considerably reduced and the final application is highly reconfigurable (real-time monitoring, parameter tuning, etc.)

Hovering by Gazing: A Novel Strategy for Implementing Saccadic Flight-based Navigation in GPS-denied Environments

International audienceHovering flies are able to stay still in place when hovering above flowers and burst into movement towards a new object of interest (a target). This suggests that sensorimotor control loops implemented onboard could be usefully mimicked for controlling Unmanned Aerial Vehicles (UAVs). In this study, the fundamental head-body movements occurring in free-flying insects was simulated in a sighted twin-engine robot with a mechanical decoupling inserted between its eye (or gaze) and its body. The robot based on this gaze control system achieved robust and accurate hovering performances, without an accelerometer, over a ground target despite a narrow eye field of view (±5 ). The gaze stabilization strategy validated under Processor-In-the-Loop (PIL) and inspired by three biological Oculomotor Reflexes (Ors) enables the aerial robot to lock its gaze onto a fixed target regardless of its roll angle. In addition, the gaze control mechanism allows the robot to perform short range target to target navigation by triggering an automatic fast "target jump" behaviour based on a saccadic eye movement

RT-MaG: an open-source SIMULINK Toolbox for Real-Time Robotic Applications

International audienceThe new open-source Matlab/Simulink toolbox called RT-MaG presented here generates reliable standalone robotic applications running on real-time embedded Linux targets such as tiny Computers On Module (e.g., Gumstix boards). This toolbox gives direct access from Simulink to the main communication drivers classically used in robotics: network interfaces (via UDP), asynchronous and synchronous serial port interfaces (RS232, SPI), Pulse-width-modulation (PWM), general purpose input-output (GPIO) and analog-todigital converters (ADCs). A Simulink model is automatically converted into a standalone multi-task program, which guarantees a repeatable execution time within each sampling time. The toolbox includes efficient debug modes which detect problems such as unsuitable configurations and hardware failure. The main features of the toolbox and its structure are described here. We also discuss the real-time performances and I/Os delays and show that a control loop can be implemented at frequencies of up to 1kHz. The tests performed show that RTMaG can be used to efficiently implement all the control laws involved in stabilizing a quadrotor

RT-MaG: an open-source SIMULINK Toolbox for Linux-Based Real-Time Robotic Applications

2014 IEEE International Conference on Robotics and Biomimetics (ROBIO), Bali, INDONESIA, DEC 05-10, 2014International audienceThe new open-source Matlab/Simulink toolbox called RT-MaG presented here generates reliable standalone robotic applications running on real-time embedded Linux targets such as tiny Computers On Module (e.g., Gumstix boards). This toolbox gives direct access from Simulink to the main communication drivers classically used in robotics: network interfaces (via UDP), asynchronous and synchronous serial port interfaces (RS232, SPI), Pulse-width-modulation (PWM), general purpose input-output (GPIO) and analog-to-digital converters (ADCs). A Simulink model is automatically converted into a standalone multi-task program, which guarantees a repeatable execution time within each sampling time. The toolbox includes efficient debug modes which detect problems such as unsuitable configurations and hardware failure. The main features of the toolbox and its structure are described here. We also discuss the real-time performances and I/Os delays and show that a control loop can be implemented at frequencies of up to 1kHz. The tests performed show that RT-MaG can be used to efficiently implement all the control laws involved in stabilizing a quadrotor

Agile robotic fliers: a morphing based approach

International audienceThe aerial robot presented here for the first time was based on a quadrotor structure, which is capable of unique morphing performances based on an actuated elastic mechanism. Like birds, which are able to negotiate narrow apertures despite their relatively large wingspan, our Quad-Morphing robot was able to pass through a narrow gap at a high forward speed of 2.5 m.s− 1 by swiftly folding up the structure supporting its propellers. A control strategy was developed to deal with the loss of controllability on the roll axis resulting from the folding process, while keeping the robot stable until it has crossed the gap. In addition, a complete recovery procedure was also implemented to stabilize the robot after the unfolding process. A new metric was also used to quantify the gain in terms of the gap-crossing ability in comparison with that observed with classical quadrotors with rigid bodies. The performances of these morphing robots are presented, and experiments performed with a real flying robot passing through a small aperture by reducing its wingspan by 48% are described and discussed