In this paper, the use of a class of robust control technique as a tool to compute the robustness margin for a closed loop multi-agent system is discussed. Our approach is based on a leader/follower structure of the multiple robot systems. It is shown that, for multiple agent system with cyclic, chain and balanced topology of information exchange, the result is achieved. A Lyapunov based robust control design for coordination and trajectory tracking of multiple agent systems with parametric uncertainty is presented. The results are illustrated with examples and simulations.

This paper is about the collaborative use of a far-infrared spectrum human detector and a visible spectrum human detector; the idea is to make collaborate these two detectors of different nature to automatically adapt the human detection whatever the luminosity changes and whatever the infrared emission changes of the scene. Our collaborative approach of detection handles: 1) gradual luminosity changes due, for instance, to the passage from night to day (and vice-versa), 2) sudden luminosity changes due, for instance, to navigation in a forest (when going through a glade in a forest), 3) infrared emission saturation when the global temperature of the scene is very high and does not permit to distinguish human people in infrared. Our approach of detection permits to detect people 24 hours a day and regardless the weather conditions. Furthermore, the proposed approach is relatively fast: it is practically as fast as using one detector alone whereas two are used in the same time.

Nowadays pedestrian detectors are fast, scale-robust and quite efficient. Embedded within a UAV such a detector would open new possibilities. In this paper the very well known HOG detector is adapted for UAV use and a new kind of training dataset is proposed in order to increase the detector's angular robustness. A more appropriate set of detection windows, together with a new detection pipeline, is proposed in order to reduce the search space and consequently reduce the computation time. Tests conducted using the improved detector show significantly better results on aerial images.

Human detection is a very popular field of computer vision. Few works propose a solution for detecting people whatever the camera's viewpoint such as for UAV applications. In this context even state-of-the-art detectors can fail to detect people. We found that the Integral Channel Features detector (ICF) is inoperant in such a context. In this paper, we propose an approach to still benefit from the assets of the ICF while considerably extending the angular robustness during the detection. The main contributions of this work are: a new framework based on the Cluster Boosting Tree and the ICF detector for viewpoint robust human detection; a new training dataset for taking into account the human shape modifications occuring when the pitch angle of the camera changes. We showed that our detector (the PRD) is superior to the ICF for detecting people from complex viewpoints in uncluttered environments and that the computation time of the detector is real-time compatible.

The growing need of energy, global warming and recent nuclear power plant accidents have shown that renewable energies need to be developed for tomorrow's world. Wind energy is generally harvested using wind turbines. Unfortunately, these systems have some drawbacks such as their cost, and the amount of steel and concrete used for construction. As their size grows, their complexity increases exponentially. This paper studies an alternative solution for the production of wind energy, using a kite's traction force. The aim of this paper is to control the amount of energy produced by the kite, and to be able to fly it safely in the presence of strong wind gusts. Our theoretical work has been implemented in a scale model flying autonomously in a wind tunnel. The proposed control strategy has led to control the system output power with an accuracy greater than 95%, with unknown wind speeds varying from 7.5 to 9 m/s.

In this paper, the coordination and trajectory tracking control design of multiple mini rotorcraft systems are discussed. The dynamic model of a mini rotorcraft is presented using the Newton-Euler formalism. Our approach is based on a leader/follower structure of multiple robot systems. The centroid of the coordinated control subsystem is used for trajectory tracking purposes. A nonlinear coordinated control design for multiple autonomous vehicle synchronization is developed. The analytic results are supported by simulation tests.

This paper addresses the coordination and trajectory tracking control design for a multiple mini rotorcraft system. The dynamic model of the mini rotorcraft is presented using the Newton-Euler formalism. Our approach is based on a leader/follower structure of multiple robot systems. A nonlinear controller based on nested saturations and a multi-agent consensus control are combined to obtain a flight formation control for a multiple mini rotorcraft system. The centroid of the coordinated control subsystem is used for trajectory tracking purposes. The analytic results are supported by simulation tests.

An original configuration of a small aerial vehicle having eight rotors is presented. Four rotors are devoted to the stabilization of the orientation of the helicopter, and the other four are used to drive the lateral displacements. A precompensation on the roll and pitch angles has been introduced so that the attitude dynamics is practically independent of the translational dynamics. This compensation is directly related to the velocity of the lateral motors. The dynamical model is obtained using the Euler–Lagrange approach. The proposed configuration is particularly useful for image processing since the the camera orientation is held constant. The eight-rotor rotorcraft is simpler to pilot than other rotorcrafts. A control strategy is proposed that uses the optical flow measurements to achieve a hover flight that is robust with respect to perturbations like wind. The new aerial configuration and control strategy have been tested in real-time experiments.

In this paper we present the dynamic model and the stabilisation of an original configuration of an small helicopter having eight rotors. This configuration is not yet presented in the literature and in our knowledge is also the first prototype of this kind of helicopters. The equations of motion for the VTOL aircraft are obtained using Euler-Lagrange approach. Due to the configuration of the aircraft the attitude dynamics are practically independent of the translational dynamics corresponding to the lateral displacements (x and y). A nonlinear control strategy based in the Lyapunov analysis is proposed to stabilize this aircraft at hover. The performance of the nonlinear control algorithm is illustrated with real-time experiments.

In this paper, the modeling and control design of a vertical flight attitude control for a mini tail-sitter with variable pitch propeller is discussed. Tail-sitters VTOL-UAVs have operational flexibility of typical helicopters while having the cruise performance of fixed wing airplanes. The configuration proposed in this work is highly unstable in its natural flight state in vertical mode. A dynamic model is developed and a linear control strategy has been developed to stabilize the platform. The results are supported by experimental tests.

This paper presents an original configuration for a small aerial vehicle based on three rotors with fixed-angle propellers. The process of control vectors generation is described, and a detailed mathematical modeling of the aircraft dynamics is presented. We have also proposed a control strategy for full stabilization of the tri-rotor aircraft considering some real constraints specific to small UAVs. The synthesized controller is simple and results in good performance as demonstrated in simulations and in real-time experiments. We have also developed a useful Simulink-based platform for real-time control purposes

This paper presents recent work concerning a small tiltrotor aircraft with a reduced number of rotors. The design consists of two propellers which can tilt laterally and longitudinally. A model of the full birotor dynamics is provided, and a controller based on the backstepping procedure is synthesized for the purposes of stabilization and trajectory tracking. The proposed control strategy has been tested in simulation

We present a dynamical model of an original trirotor helicopter obtained using the Euler-Lagrange approach. The obtained nonlinear model is then used for designing a nonlinear controller based on nested saturations. The controller performance is shown in real-time experiments.

In this paper we present a controller design and implementation on a mini-rotorcraft having four rotors. A Lagrangian model of the helicopter was used for the controller synthesis. The proposed controller is based on Lyapunov analysis. Experimental results show that the controller is able to perform autonomously the tasks of taking-off, hovering and landing.

In this paper a simplified model and a nonlinear control algorithm for a coaxial helicopter are presented. The model of the helicopter dynamics is obtained in hover conditions. By neglecting the small body forces due to the mechanism used to obtain the torque control, a dynamic controller, based on backstepping techniques, is developed. Some simulation results are presented to illustrate the performance of such a controller.

A simplified model of the dynamics of an autonomous model helicopter valid for manoeuvres close to hover is considered. The control task is to track a given path in the position co-ordinates as accurately as possible. This is made difficult since the model contains weakly non-minimum phase zero dynamics which cannot be stably inverted. By placing constraints on the physical weight distribution associated with the necessary sensor and computer components that must be carried by the autonomous unit a new representation the dynamics of the system in block pure feedback form is derived. The exact tracking problem is solved using input/output linearization techniques.

Considers the set-point regulation control problem of rigid and flexible-joint electrically driven robots with model uncertainties and unknown payloads. The proposed control scheme is based on simple linear state and output feedbacks. The resulting controller can also be implemented in a case where the current signal is not measurable. Applications of the approach when the Coulomb friction forces are taken into account have also been considered.