Search

International audience

Summary This paper addresses the directional control problem of autonomous air vehicles in order to obtain trajectory tracking capabilities when flying in other than calm conditions. The control strategy is designed in the framework of the Lyapunov theory, and adaptive techniques are employed for online wind identification. An application of light fixed-wing unmanned aerial vehicles that consists in tracking straight-line paths between geo-referenced waypoints is first formulated, and the dynamic of the cross track error with respect to such trajectory is further obtained from the lateral airplane equations of motion. The dynamic order of the closed-loop adaptive system is guaranteed to be minimal by choosing the proper variables so that the tuning functions method could be applied. Several simulations taking into account unknown wind have been performed to analyze the behavior and the robustness of the control scheme. Copyright © 2014 John Wiley & Sons, Ltd.

In this paper we consider a special class of integral delay systems arising in several stability problems of time-delay systems. For these integral systems we derive stability and robust stability conditions in terms of Lyapunov–Krasovskii functionals. More explicitly, after providing the stability conditions we compute quadratic functionals and apply them to derive exponential estimates for solutions, and robust stability conditions for perturbed integral delay systems. Copyright © 2008 John Wiley & Sons, Ltd.

In this paper we present a control strategy for the stabilization of a rigid beam balanced by a cart. The control problem consists of horizontally balancing the beam by moving the cart backwards and forwards along the beam. The cart movement is restricted to always remain over the beam. The control strategy is based on the interconnection and damping assignment passivity based controller. The stability analysis is carried out using LaSalles's theorem. Copyright © 2008 John Wiley & Sons, Ltd.

This paper describes the design of an embedded control system for a four-rotor unmanned aerial vehicle (UAV) to perform hover flights. A dynamic model of the vehicle is presented using an Euler–Lagrange approach. A control strategy based on nested saturation is proposed. An embedded control system architecture is described for autonomous hover flight. The main components of the system are a microcontroller, an inertial measurement unit (IMU), a global positioning system (GPS) and infrared sensors. The Euler angles are computed using a data fusion algorithm. The experimental results show that the on-board control system performs satisfactorily for autonomous hovering indoors. Copyright © 2007 John Wiley & Sons, Ltd.

In this paper, we focus on the design and implementation of a controller for a two degree-of-freedom system. This system is composed of a small-scale helicopter which is mounted on a vertical platform. The model is based on Lagrangian formulation and the controller is obtained by classical pole-placement techniques for the yaw dynamics and adaptive pole-placement for the altitude dynamics. Experimental results show the performance of such a controller. Copyright © 2004 John Wiley & Sons, Ltd.

The problem of on-line identification of a parametric model for continuous-time, time-varying systems is considered via the minimization of a least-squares criterion with a forgetting function. The proposed forgetting function depends on two time-varying parameters which play crucial roles in the stability analysis of the method. The analysis leads to the consideration of a Lyapunov function for the identification algorithm that incorporates both prediction error and parameter convergence measures. A theorem is proved showing finite time convergence of the Lyapunov function to a neighbourhood of zero, the size of which depends on the evolution of the time-varying error terms in the parametric model representation. Copyright © 2001 John Wiley & Sons, Ltd.

We consider the control of a hovercraft having only two control inputs with three degrees of freedom. The model is obtained from equations of a simplified ship which is nonlinear and underactuated. Using a co-ordinate transformation the model is given by polynomial equations which describe its kinematics and dynamics. Two control laws are proposed. The first one controls the velocity of the hovercraft. The other one stabilizes both its position and the (underactuated) side velocity and provides global convergence to the origin. The convergence analysis is based on a Lyapunov approach. Copyright © 2000 John Wiley & Sons, Ltd.

In this paper we study new relationships between a class of Lyapunov functions and the passivity theorem. It is proved that under some (sufficient) conditions a Lyapunov-stable system can be analysed as the feedback connection of two (strictly) passive subsystems. It is also shown that very recent adaptive schemes for linear plants of any relative degree can in a certain sense be unified through a passivity point of view.

The standard least squares (LS) estimation algorithm is modified in such a way that it becomes passive. Therefore the scope of application of the LS algorithm is extended to those adaptive schemes whose convergence proof is based on passivity. The passive version of LS is presented in both continuous and discrete time.