Abderraouf Benali

Asymptotic Backstepping Stabilization of an Underactuated Surface Vessel

This brief addresses the problem of controlling the planar position and orientation of an autonomous underactuated surface vessel. Under realistic assumptions, we show, first, that there exists a natural change of coordinates that transforms the whole dynamical system into a cascade nonlinear system, and, second, the control problem of the resulting system can be reduced to the stabilization of a third-order chained form. A time-invariant discontinuous feedback law is derived to guarantee global uniform asymptotic stabilization of the system to the desired configuration. The construction of such a controller is based on the backstepping design approach. A simulation example is included to demonstrate the effectiveness of the suggested approach

New algorithm for observer error linearization with a diffeomorphism on the outputs

In this paper, we give the necessary and sufficient conditions that guarantee the existence of a diffeomorphism which allows one to transform a multi-output nonlinear dynamical system into a normal observable canonical form. In particular, we propose an algorithm that permits one to derive such diffeomorphism. The main feature of the canonical form is that it is obtained by allowing a diffeomorphism on the outputs and it also allows one to design an observer with linear error dynamics. We first consider multi-output nonlinear dynamical system without inputs. We then extend the results obtained to multi-output nonlinear dynamical system with inputs.

About the observability of piecewise dynamical systems

Abstract In this paper, we give some sufficient geometrical conditions to analyse the observability of a class of hybrid systems: piecewise-smooth dynamical systems. For the subclass of piecewise linear systems, the analysis of the observability is refined. Indeed, thanks to the algebraic structure of this subclass, we improve one of these sufficient conditions by using the rank of a matrix associated to a piecewise linear system. This matrix takes into account all the observability matrices of the subsystems as well as the switch linear function. Throughout this paper we give examples to highlight our method.

Modelling and control of an omnidirectional mobile manipulator

Abstract A new approach to control an omnidirectional mobile manipulator is developed. The robot is considered to be an individual agent aimed at performing robotic tasks described in terms of a displacement and a force interaction with the environment. A reactive architecture and impedance control are used to ensure reliable task execution in response to environment stimuli. The mechanical structure of our holonomic mobile manipulator is built of two joint manipulators mounted on a holonomic vehicle. The vehicle is equipped with three driven axles with two spherical orthogonal wheels. Taking into account the dynamical interaction between the base and the manipulator, one can define the dynamics of the mobile manipulator and design a nonlinear controller using the input-state linearization method. The control structure of the robot is built in order to demonstrate the main capabilities regarding navigation and obstacle avoidance. Several simulations were conducted to prove the effectiveness of this approach.

Geometrical conditions for observer error linearization with a diffeomorphism on the outputs

Abstract This paper gives the sufficient and necessary conditions which guarantee the existence of a diffeomorphism which transforms the dynamic of a multi outputs nonlinear system without input into a linear dynamic up to a vector field which depends only on the outputs. The same diffeomorphism yields a diffeomorphism on the outputs. In this case we can design an observer which linearizes the error of the dynamical system under consideration.

Observer design for linear switched systems : A common Lyapunov function approach

In this paper, we give sufficient conditions for the stability of a class of switched systems. Based on the symmetric part of the state space matrix and on LaSalles invariance principle, to ensure the asymptotic stability of switched linear systems, under a special class of switching signals. The proposed stability results are used to design an observer of switched linear systems for which the discrete state is available. Examples are given to highlight our propositions.

Force-position control of a holonomic mobile manipulator

In this article we develop a new approach to control an omnidirectional mobile manipulator. This approach is based on a layered command structure and impedance control technique. First we define multiple control behaviors depending on the robot tasks. Two behaviors are considered here the synchronized one and the independent one. Each behavior mentioned above is described in terms of force and position models in order to allow each robot to regulate his corresponding behavior. In the case of synchronized situation, kinematic modeling is presented with particular emphasis on redundancy. We use the additional task concept to solve the control problem of these redundant holonomic systems by taking into account the external forces.

Modelling and feedback control of an omni-directional mobile manipulator

In this article we develop a new approach to control an omnidirectional mobile manipulator. The robot is considered as an individual agent aimed to perform robotic tasks described in terms of displacement and force interaction with the environment. A reactive architecture and impedance control are used to ensure reliable task execution in response to environment stimuli. The mechanical structure of our holonomic mobile manipulator is built from two joint manipulator mounted on an holonomic vehicle. The vehicle is equipped using three motorized axles with two spherical orthogonal wheels. The dynamics of the mobile manipulator robot is defined tacking into account the dynamical interaction between the base and the manipulator. Then we design a nonlinear controller for the robot using input-state linearization method. The control structure of the robot is built in order to demonstrate the main capabilities in navigation and obstacle avoidance. Several simulations were conducted to prove the effectiveness of our concept.

A MULTI-AGENT STRATEGY FOR A SIMPLE COOPERATIVE BEHAVIOR

This paper presents an application of the multi-agent system approach to mobile manipulators that cooperate to achieve displacement of heavy and large objects. Therefore, the task is distributed between agents, and each agent offers and negotiates its services that help in accomplishing the mission. The multi-agent system has been developed using the oRis platform. The main components of such a system include communication and negotiation protocols. Hence we present the behavior of robots, their interaction, and their behavior toward obstacles. Computer simulations are conducted in order to demonstrate the feasibility of the proposed approach.

Dynamic Controller of Switched Linear Systems : a Common Lyapunov Function Approach

This paper is devoted to the problem of design a dynamic controller of switched linear systems. In the first part of this paper, we give some remarks about the influences of switching signal on the asymptotic stability of switched systems. We give a practical example to generate a large class of switching signals. The second part is devoted to the switched dynamic controller design, based on a common Lyapunov function approach. A sufficient condition is formulated as an LMI problem for the switched controller design under arbitrary switching. A stabilizing switched controller with regional pole placements is also formulated as a convex problem, an LMI approach is used to derive the switched dynamic controller with performance limitations