Observer design for position and velocity bias estimation from a single direction output

This paper addresses the problem of estimating the position of an object moving in $R^n$ from direction and velocity measurements. After addressing observability issues associated with this problem, a nonlinear observer is designed so as to encompass the case where the measured velocity is corrupted by a constant bias. Global exponential convergence of the estimation error is proved under a condition of persistent excitation upon the direction measurements. Simulation results illustrate the performance of the observer.Comment: 6 pages, 6 figure

A Standardized Workflow Based on the STAVIRO Unbaited Underwater Video System for Monitoring Fish and Habitat Essential Biodiversity Variables in Coastal Areas

Essential Biodiversity Variables (EBV) related to benthic habitats and high trophic levels such as fish communities must be measured at fine scale but monitored and assessed at spatial scales that are relevant for policy and management actions. Local scales are important for assessing anthropogenic impacts, and conservation-related and fisheries management actions, while reporting on the conservation status of biodiversity to formulate national and international policies requires much broader scales. Measurements must account for the fact that coastal habitats and fish communities are heterogeneously distributed locally and at larger scales. Assessments based on in situ monitoring generally suffer from poor spatial replication and limited geographical coverage, which is challenging for area-wide assessments. Requirements for appropriate monitoring comprise cost-efficient and standardized observation protocols and data formats, spatially scalable and versatile data workflows, data that comply with the FAIR (Findable, Accessible, Interoperable, and Reusable) principles, while minimizing the environmental impact of measurements. This paper describes a standardized workflow based on remote underwater video that aims to assess fishes (at species and community levels) and habitat-related EBVs in coastal areas. This panoramic unbaited video technique was developed in 2007 to survey both fishes and benthic habitats in a cost-efficient manner, and with minimal effect on biodiversity. It can be deployed in areas where low underwater visibility is not a permanent or major limitation. The technique was consolidated and standardized and has been successfully used in varied settings over the last 12 years. We operationalized the EBV workflow by documenting the field protocol, survey design, image post-processing, EBV production and data curation. Applications of the workflow are illustrated here based on some 4,500 observations (fishes and benthic habitats) in the Pacific, Indian and Atlantic Oceans, and Mediterranean Sea. The STAVIRO’s proven track-record of utility and cost-effectiveness indicates that it should be considered by other researchers for future applications.publishedVersio

Contributions à l'asservissement visuel de véhicules aériens autonomes

L asservissement visuel est une technique de commande reposant sur des mesures issues d une caméra. Cette technique est apparue à la fin des années 80 pour contrôler des robots mobiles ou des bras manipulateurs. Depuis peu, l asservissement visuel est appliqué aux engins volants, pour lesquels ce type de contrôle a un fort potentiel opérationnel. Dans cette thèse, nous nous intéressons à la conception d asservissements visuels pour deux types d engins volants : les minidrones à voilures tournantes et les avions. Nous essayons autant que possible de spécifier le problème en termes de régulation dans l image en prenant en compte des contraintes forte sur la nature des capteurs utilisés. Ainsi nous considérons uniquement les capteurs embarqués, autonomes, et dont la qualité est compatible d un asservissement précis. Pour cela, nous proposons des lois d asservissement visuels adaptés à la dynamique des engins considérés, à leurs structures de contrôle et à leurs systèmes de mesures. Pour les minidrones à voilures tournantes, une série de lois de commande est proposée pour stabiliser l engin relativement à une cible plane dont quelques amers sont détectés en temps réel. Ces commandes ont la particularité de ne pas nécessiter de mesure de vitesse de translation. Caractéristique intéressante puisque cette grandeur est particulièrement difficile à mesurer sans GPS. L un des algorithmes a été validé en vol sur la plateforme Hovereye de Bertin Technologies, il s agissait, à notre connaissance du premier asservissement visuel basé image, réalisé en intérieur, sur un minidrone. Pour les engins à voilures fixes une nouvelle technique d atterrissage autonome basée sur la détection des bords de la piste est proposée. Cette technique est basée image et prend en compte les spécificités du vol d un avion ainsi qu une estimation de la vitesse du vent. La validation de cette approche est réalisée sur un simulateur complexe incluant la chaîne de traitement d image. Enfin, nous avons cherché de nouvelles applications à l asservissement visuel basé image d engins à voilures fixes. Une loi de commande permettant une stabilisation précise sur une orbite d observation a ainsi été synthétisée. Elle repose sur la détection d un unique amer et du flux optique de translation. Des simulations illustrent les performances de ce dernier algorithme.The visual servo control technology is based on measurements form a camera. This technique appeared in the late 80 s to control mobile robots or manipulators. Recently, visual servoing is applied to flying vehicles, for which this type of control has a strong operational potential. In this thesis, we focus on the design of visual servoing for two types of flying vectors : the VTOL minidrones and fixed-wing aircrafts. We try wherever possible to specify the problem in terms of regulation in the picture by taking into account the limitations of the sensors used. Thus we consider only the onboard sensors autonomous, and whose quality is consistent with a the considered visual servoing tasks. For this, we propose visual servoing laws adapted to the considered systems intheir control structures and their measurement systems. For VTOL minidrones, a series of control laws is proposed to stabilize the vehicle with respect to a relativity flat target which some landmarks are detected in real time. These commands have the distinction of not requiring measurements of the speed of translation. This characteristic is especially interesting, since this variable is particularly difficult to measure without GPS. One of the algorithms has been, validated in fight ion the platform. HoverEye developed by Bertin Technologies, it was, to our knowledge the first image based visual servoing, conducted indoors on a minidrones. For fixed-wing aircrafts, a next autonomous landing technique based on the detection of runway s edges is proposed. This technique is image based and takes into account the specificities of aircraft flight dynamics. Moreover a specific estimate of cross-wind is proposed. Validation of this approach is performed on a complex simulator which includes images processing. Finally, we sought new applications in image based visual servoing for fixed-wing aircrafts. A control law for precise stabilization on observation orbit has been synthesized. It is based on the detection of a single landmark and translational optical flow. Simulations illustrate the performance of that algorithm.NICE-BU Sciences (060882101) / SudocSudocFranceF

Visual Servoing of a VTOL Vehicle using Virtual States

An Image-Based Visual Servo (IBVS) control strategy is proposed for a class of under actuated systems. The class of systems considered includes dynamic models of vehicles capable of quasi-stationary flight. The paper extends earlier works that stabilise

Image-Based Visual Servo Control for Circular Trajectories for a Fixed-Wing Aircraft

This paper describes a new visual-servo control algorithm to stabilize an aircraft along a circular trajectory using a single visual landmark on textured flat ground. The control algorithm requires a sensor suite consisting of inertial measurement unit, along with a single embedded camera capable of detecting and tracking a visual feature and estimating optic flow. The proposed control algorithm does not require independent position or velocity measurements and functions effectively in the absence of global positioning system (GPS) signals.We prove local asymptotic convergence of the closed-loop system and provide simulation results to illustrate the closed-loop system performance

Output based Observation and Control for Visual Servoing of VTOL UAV's

An Image-Based Visual Servo (IBVS) control strategy for stabilisation of Vertical Take-Off and Landing (VTOL) vehicles with respect to a fixed target is proposed. A visual feature based on the combination of the first order un-normalized spherical momen

Dynamic Image Based Visual Servo Control For An Aerial Robot: Theory and Experiments

This article considers the question of dynamic image-based visual servo control for a vertical take-off and landing unmanned aerial vehicle. The visual targets considered are colored blobs on a flat surface to which the normal direction is known. A full

Output feedback observation and control for visual servoing of VTOL UAVs

This paper considers the question of stabilizing vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) using a minimal and an inexpensive sensor suite. The sensor suite considered consists of rate gyros and a single embedded video camera system. The approach taken is based on the principles of dynamic image-based visual servo control and extends the authors' earlier work by removing dependence on additional sensors, such as accelerometers and magnetometers. The technique presented has potential for mini-UAVs evolving in urban areas where global positioning system signals may not be available. The control algorithms and coupled state observers are presented in details. The main result of the paper is synthesized in a theorem along with a rigorous stability analysis of the closed-loop system. An estimate of the basin of attraction for the closed-loop system is provided. Simulation results are performed to illustrate the performance of the proposed control