Olivier Parodi

Coordinated Formation Control of Multiple Autonomous Underwater Vehicles for Pipeline Inspection

This paper addresses the control problem of inspecting underwater pipeline on the seabed, with coordinated multiple autonomous underwater vehicles in a formation. Based on the leader-follower strategy, the dedicated nonlinear path following controller is rigorously built on Lyapunov-based design, driving a fleet of vehicles onto assigned parallel paths elevated and offset from the underwater pipeline, while keeping a triangle formation to capture complete 3D images for inspection. Due to the spatial-temporal decoupling characteristics of individual path following controller, the velocities of the followers can be adapted in the coordinated control level, only relying on the information of generalized along-path length from the leader, in order to build the desired formation. Thus, the communication variable broadcast from the leader is kept to a minimum, which is feasible under the severely constraints of acoustic communication bandwidth. Simulation results illustrate the efficiency of coordinated formation controller proposed for underwater pipeline inspection.

Coordinated path following control of multiple nonholonomic vehicles

This paper addresses the problem of coordinated path following control of multiple nonholonomic vehicles. The control laws are derived based on the leader-follower strategy, driving unicyle-type nonholonomic vehicles at kinematic level onto predefined parallel paths, while keeping an in-line formation. Due to the spatial-temporal decoupling characteristics of individual path following controller, the velocity of the follower can be adapted only based on the information of generalized along-path length from the leader, which keeps the inter-vehicle communication to a minimum. Simulation results illustrate the efficacy of the solution to coordinated control proposed here. Moreover, the theoretical analysis in this paper reveals some important issues raising that the path following control on the first-order unicyle-type nonholonomic systems can be extended to underactuated AUVs in future work.

Coordinated path following control of multiple wheeled mobile robots through decentralized speed adaptation

This paper addresses the problem of coordinated path following of multiple wheeled mobile robots while keeping a desired formation. The control laws proposed are categorized into two envelopes, one is steering individual robots to trace along predefined paths, and the other is ensuring tracked paths to be well defined in the formation, by means of decentralized speed adaption.Within this framework, geometric paths following are built on Lyapunov theory and backstepping techniques, while injecting helmsman like behavior into individual path following control. Speed adaption with minimum communication variable under the constraints of multi-robot communication topology, is elaborately designed without relative speeds between neighboring robots requested. The simple but effective controller design, enables multi-robot system to be coordinated and stabilized into an invariant manifold, and all speeds converge to desired profiles in addition. Simulation results illustrate the efficacy of the solution proposed.

Hardware-in-the-loop simulators for multi-vehicles scenarios: survey on existing solutions and proposal of a new architecture

The aim of this paper is to review the available simulators defining in a first step the necessary requirements to cope with the multi-vehicles cooperation context. In order to get a complete overview of these tools, a new classification is proposed and is used to sort the existing simulators. It is worth to be noted that we focus our interest on simulators which can at least address the problem of marine robotics.

Vehicle-following guidance for unmanned marine vehicles

Abstract The problem of an unmanned surface vehicle following another vessel, both underwater or on the surface, without having any a priori information about its path is addressed in this paper. Theoretically the problem is solved extending nonlinear Lyapunov-based control techniques to the case of a master-slave vehicle formation, introducing a virtual controlled degree of freedom for the target to be followed on the path. In order to validate the proposed approach for different classes of vehicles, two typical operational cases are considered: i ) a slave USV, acting as a communication relay, is required to remain over the vertical of a master AUV; ii ) a slave USV is required to follow the path of a master USV at a desired range, for instance, for collecting bathymetric profiles with two different sensors. Experiments on the AUV-USV case study are performed in the multi-vehicle simulation environment Thetis, developed by CNRS-LIRMM considering a joined mission of the Taipan AUV and Charlie USV. The effectiveness of the proposed approach in the USV-USV case has been demonstrated by at sea trials carried out with the Charlie and ALANIS USVs.

Design, simulation and experimental results of Taipan 300, a new Autonomous Underwater Vehicle prototype

In this paper we present a new small Autonomous Underwater Vehicle (AUV) called Taipan 300. First, we detail its technical features. Then, we explain how the particular hardware design of this vehicle makes its recovery easier in case of software or hardware failure. In fact this prototype offers enhanced safety measures in order to detect computer failure and to facilitate vehicle localization after it has resurfaced. In a third part, we describe the sliding control used. The last part consists in the presentation of the results obtained during experiments.

Comparison between results obtained with Thetis, a real-time multi-vehicles hardware-in-the-loop simulator, and results obtained during sea trials

The purpose of this paper is to present Thetis: a real-time multi-vehicles hybrid simulator for heterogeneous vehicles. This simulator allows Hardware In Loop (HIL) simulations including virtual sensors which allow to provide a representation of a virtual world, and including the support of communication devices. The architecture of this simulator is conceived so that it ensures a temporal decoupling between the virtual environment, the vehicles, sensors and communication simulators and, of course, the actual embedded controller which warrants us the quality of the results. This paper presents a classification and a short state-of-the-art of the different types of existing simulators. Then we will introduce the architecture and functionalities of Thetis. Finally we will compare results obtained during sea-trial with our AUV Taipan300 and with our simulator.

Missions preparation and design of new algorithms for Charlie and Taipan within Thetis, a HIL simulator

Abstract The purpose of this paper is to present why and how the new simulator, called Thetis , can be used to test and validate new coordinated command algorithms. We focus on examples involving the Autonomous Underwater Vehicle (AUV) Taipan 2 developed at LIRMM-CNRS (France) and the Autonomous Surface Vehicle (ASV) Charlie developed at ISSIA-CNR (Italy). Thetis is a new real-time multi-vehicles simulator for heterogeneous vehicles. It allows Hardware In The Loop (HIL) simulations including the use of virtual sensors providing a representation of a virtual world, including the support of communication devices. After a short state-of-the-art study, we introduce the main mechanisms of our simulator and we present the specificities of our tool compared to the other existing solutions. Finally we show a set of typical missions involving Taipan 2 and Charlie, focusing on the ability of our tool to validate ongoing propositions concerning flotilla strategy.

Optimized Gait Generation for Anguilliform Motion

In this paper, we are looking for a solution to optimize the path generation of an eel-like robot. Previous works have shown that a successful approach to generate path is to control explicitly the local system curvature. This control design based on Lyapunov methods warrants the convergence of the system shape towards the desired curvature profile. Then the purpose of this work is to determine a local optimized couple of curvature parameters which are able to guarantee a fast system response, an efficient propulsion which minimizes the spent energy or both of them. This is made through three criteria which are able to give us a local solution. Finally, we present results from simulations in motion planning for a ten-link-eellike robot, to illustrate the performance of the proposed solution.