Vincent Creuze

From PD to Nonlinear Adaptive Depth-Control of a Tethered Autonomous Underwater Vehicle

This paper deals with an experimental comparison between a proportional derivative (PD) controller and an adaptive nonlinear state feedback one, both applied on a tethered autonomous underwater vehicle. The aim is to show the behavior of the closed loop system in the nominal case for each of these two controllers, and then to test their robustness towards some parameters changes. The PD on one hand has a good performance for systems with an unknown model. The adaptive control law on the other hand is known to adjust the unknown parameters of the plant in order to converge to the desired trajectory. This study shows experimental results performed using each of the above mentioned control laws.

Adaptive Terminal Sliding Mode Control of a Redundantly-Actuated Cable-Driven Parallel Manipulator: CoGiRo

This paper presents an extended adaptive control scheme via terminal sliding mode (TSM) for cable-driven parallel manipulators (CDPM). Compared with linear hyperplane-based sliding mode control, TSM is able to guarantee high-precision and robust tracking performances which arise from its main feature of finite-time convergence. This motivates applying TSM to robotic manipulators in general and, as presented in this paper, to CDPM in particular. The scheme presented in this paper extends early developed TSM control schemes which are based on partial knowledge of system dynamics. Instead, making use of the property that the dynamic models of mechanical manipulators are linear in inertial parameters, an adaptive control law is synthesised based on an appropriate choice of Lyapunov function which guarantees finite-time convergence to neighborhood of sliding mode. A key challenge of the control of CDPM is that cable tensions must be admissible, i.e. lying in a non-negative range of admissible values. As long as cable tensions are admissible, the overall dynamics of CDPM can be easily written in either actuator space or operational space which in turn facilitates control system design. The extended adaptive control scheme has been applied to a large redundantly actuated CDPR prototype, CoGiRo. Simulation results show the effectiveness of the proposed control method.

A novel application of multivariable ℒ 1 adaptive control: From design to real-time implementation on an underwater vehicle

This paper presents the design and experimental implementation of an ℒ1 adaptive control on a tethered underwater vehicle. This controller, well known for its fast adaptation and its robustness, is proposed to be applied for the first time in the field of underwater vehicles control. This paper summarizes the implementation and experimental results obtained on a modified version of the AC-ROV underwater vehicle. Various experimental scenarios are presented to illustrate the ability of the ℒ1adaptive law not only to successfully control pitch and depth (even with strong modeling uncertainties), but also to be efficient towards disturbances like waves or buoyancy changes.

A new extension of the L1 adaptive controller to drastically reduce the tracking time lags

Abstract The lrc; 1 adaptive control scheme has proven its effectiveness and robustness in various fields thanks to its particular architecture where robustness and adaptation are decoupled. It was though noted that whenever the trajectory is varying, an inherent lag is present compared to other adaptive schemes due to the presence of a filter in the control architecture. To achieve a better tracking, we propose extending the architecture of the lrc; 1 controller by augmenting it with a control input that could take the form of a nonlinear proportional or a proportional integral term. The extended scheme is validated through simulations via an illustrative example as well as experimental results performed on an underwater vehicle.

Stability analysis of a new extended L 1 controller with experimental validation on an underwater vehicle

L1 adaptive control is a recent scheme elaborated in order to ensure a decoupling between robustness and fast adaptation. This controller was validated in simulations and experimental results. Research is currently being developed in order to improve its architecture and design challenges. Our study focuses on the inherent time lag observed in presence of a varying reference trajectory. The solution proposed in this regard is the extended L1 controller in which we suggest an augmentation of the original one with a PID aiming to reduce the tracking error. The stability analysis of this new scheme is shown in this paper. Experimental results on an underwater vehicle subjected to a varying trajectory under several disturbances are then displayed to illustrate the efficiency of the method.

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.

3D-bottom tracking based on acoustic diffraction for autonomous underwater vehicles

Navigation of autonomous underwater vehicles (A.U.V.) in very shallow waters implies acoustic detection. In single beam sonar systems, sound emitted by ultrasonic transducers is diffracted and secondary lobes appear. Considering the sea bottoms backscattering properties, secondary lobes can be used to work out the three-dimensional equation of the plane that represents the seabed. In this paper, we first consider characteristics of electro-acoustic transducers with rectangular aperture and study the resulting acoustic diffraction. Then, we explain how to choose the best dimensions of the transducer and the related best orientation. Moreover, we introduce a method aiming to extract the seabed 3D equation from the received acoustic echo. Thus single beam sonar systems can be used for bottom tracking purposes. We present the results of our simulations and our experimental device

Using sound diffraction to determine the seabed slope

Navigation of autonomous underwater vehicles (A.U.V.) in very shallow waters implies acoustic detection. In single beam sonar systems, sound emitted by ultrasonic transducers is diffracted and secondary lobes appear. Considering the sea bottoms backscattering properties, secondary lobes can be used to enhance knowledge of seabed features such as slope, and marked variations. In this paper, we firstly consider characteristics of electro-acoustic transducers and study the resulting acoustic diffraction. Then, we introduce a new method aiming to extract seabed features from the received acoustic echo. Thus, single beam sonar systems can be used for bottom tracking purposes. We present the results of our simulations and experimental validation.

French Archaeology’s Long March to the Deep—The Lune Project: Building the Underwater Archaeology of the Future

This paper describes our project to study the wreck of the Lune and the determination of French archaeologists to develop viable techniques for working on deep-water wrecks. We begin by sketching out the general context of underwater archaeology in France before describing in detail our long march to the deep. We conclude with an overview of the Corsaire Concept project for deep sea archaeology.

Extended Model-Based Feedforward Compensation in ℒ1 Adaptive Control for Mechanical Manipulators: Design and Experiments

This paper deals with a new control scheme for Parallel Kinematic Manipulators (PKMs) based on the L1 adaptive control theory. The original L1 adaptive controller is extended by including an adaptive loop based on the dynamics of the PKM. The additional model-based term is in charge of the compensation of the modeled nonlinear dynamics in the aim of improving the tracking performance. Moreover, the proposed controller is enhanced to reduce the internal forces, which may appear in the case of Redundantly Actuated PKMs (RA-PKMs). The generated control inputs are first regulated through a projection mechanism that reduces the antagonistic internal forces, before being applied to the manipulator. To validate the proposed controller and to show its effectiveness, real-time experiments are conducted on a new four degrees-of-freedom (4-DOFs) RA-PKM developed in our laboratory.