A 3D reconstruction from real-time stereoscopic images using GPU

IEEE Xplore Compliant Files 979-10-92279-01-6International audienceIn this article we propose a new technique to obtain a three-dimensional (3D) reconstruction from stereoscopic images taken by a stereoscopic system in real-time. To parallelize the 3D reconstruction we propose a method that uses a Graphics Processors Unit (GPU) and a disparity map from block matching algorithm (BM). The results obtained permit us to accelerate the images processing time, measured in frames per second (FPS) with respect to the same method using a Central Processing Unit (CPU). The advantage of speed using GPU advocates our system for practical applications such as aerial reconnaissance, cartography, robotic navigation and obstacle detection

Integral backstepping control for trajectory tracking of a hybrid vehicle

International audienceThis article is focused on the trajectory tracking using a hybrid terrestrial aerial vehicle. An integral back-stepping control is proposed for the UAV vehicle mode. In addition, a nested saturation control is developed and applied to regulate the position of the cart vehicle. These control laws are validated by simulations and some experimental results on position control was performed by applying the techniques aforementioned. I. SYSTEM DESCRIPTION In this work control laws are developed for trajectory tracking of a hybrid terrestrial aerial vehicle. These kinds of vehicles have the advantage to be used as a flying vehicle or as a cart depending on the situation. Some situations may be when the vehicle find an obstacle and it has to take the more convenient mode of operation to overcome or to avoid the obstacle. Controlling these hybrid vehicles becomes a challenge. It is necessary to design and implement control laws for the trajectory following in the air and over the floor. The control strategy has to generate a smooth transition when the drone is passing from air to floor or vice versa. There are several works dedicated to path following with hexarotors and also for carts, see for example [1]–[3]. This work considers a particular hybrid vehicle : a mini-UAV that is converted in a cart by attaching to it two wheels without any additional motors as in Fig. 1. The orientation and position of the cart will be controlled by the yaw and pitch angles and by the thrust generated by its helices. Among its characteristics, the thrust direction can be inversed as a result of the pitch angle variation. Therefore, the cart-drone can move forward or backward depending on the sign of pitch angle. This hybrid vehicle in terrestrial mode can turn around z axis. It is also a nonholonomic system because it is not capable to move on the wheels axis direction in terrestrial mode. For more references in cart control refer to [4]–[6]

Velocity control of mini-UAV using a helmet system

International audienceThe usage of a helmet to command a mini-unmanned aerial vehicle (mini-UAV), is a telepresence system that connects the operator to the vehicle. This paper proposes a system which remotely allows the connection of a pilot's head motion and the 3D movements of a mini-UAVs. Two velocity control algorithms have been tested in order to manipulate the system. Results demonstrate that these movements can be used as reference inputs of the controller of the mini-UAV

Position Control of a Quadrotor under External Constant Disturbance

International audienceIn the present work, an adaptive backstepping algorithm is developed in order to counteract the effects of disturbances. These disturbances are modeled as a constant force in the translational model part and as a constant torque in the orientation model part. We make the deduction of the mathematical expression for the proposed control algorithm and also we show its performance in simulation. Additionally, we include some experiments for validating the results obtained via simulation

An Intermediary Quaternion-based Control for Trajectory Following Using a Quadrotor

International audience— This work uses the intermediary quaternions in the design of a backstepping control technique with integral properties in order to perform an autonomous trajectory tracking using a quadcopter vehicle. Nowadays, in order to determine the orientation of a vehicle, most of the inertial systems of aircrafts can give directly the rotation matrix and taking advantage of this fact, the intermediary quaternions can be determined in a simple way from this matrix. Moreover, one specific orientation corresponds to only one intermediary quaternion and this helps to cope the unwinding phenomenon presented when working with the classical quaternions. The proposed control algorithm is validated numerically and experimentally when the quadrotor follows a circular trajectory. In addition, during the simulation part, some external perturbations and white noise were added in order to test the robustness of the algorithm

Vision Based Tracking for a Mini-Rotorcraft Using Vanishing Points

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Vision-based autonomous hovering for a miniature quad-rotor

International audienceIn this paper, a vision-based scheme for the autonomous hovering of a miniature quad-rotor is developed. Cameras are used to estimate the position and the translational velocity of the vehicle. The dynamic model of the miniature quad-rotor is developed using the Newton-Euler approach. A nonlinear controller based on a separated saturation control strategy for a miniature quad-rotor is presented. To validate the theoretical results, an embedded control system for the miniature quad-rotor has been developed. Thus, the analytic results are supported by experimental tests. Experimental results have validated the proposed control strategy

Vision Based Autonomous Hover of a Mini-Rotorcraft

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