Michel Perrier

3D Reconstruction of Natural Underwater Scenes Using the Stereovision System IRIS

The aim of this study is to propose a 3-dimension reconstruction method of small-scale scenes improved by a new image acquisition method for quantitative measurements. A stereovision system is used to acquire images in order to obtain several shots of an object, at regular intervals according to a predefined trajectory. A complete methodology of 3D reconstruction is exposed to perform a dense 3D model with texture mapping. A first result on natural images collected with the stereovision system during sea trials has been obtained.

Nonlinear control of an underwater vehicle/manipulator with composite dynamics

This paper deals with the problem of control design of an underwater vehicle/manipulator system composed of a free navigating platform equipped with a robot manipulator. This composite system is driven by actuators and sensors having substantially different bandwidth characteristics due to their nature. Two control laws are proposed. The first is a simplification of the computed torque control law which only requires partial compensation for the slow-subsystem. Feedback compensation is only-needed to overcome the coupling effects from the arm to the basis. The second aims at replacing this partial compensation by a robust nonlinear control that does not depend on the model parameters. The closed-loop performance of this controller is close to that of the model-based compensation. Both control laws are shown to be closed-loop stable in the sense of the perturbation theory. A comparative study between a linear PD controller, a partial model-based compensation, and the nonlinear robust feedback is presented.

UNION: underwater intelligent operation and navigation

The main goal of the UNION ESPRIT Basic Research Action is to develop methods for increasing the autonomy and intelligence of underwater remotely operated vehicles (ROVs). The project focuses mainly on the development of coordinated control and sensing strategies for combined manipulator and vehicle systems. Both fundamental theories and methods for the design of these heterogeneous systems are investigated. A complex canonical mission in the field of offshore inspection maintenance and repair tasks was chosen as an integration guideline of all the results.

Robust nonlinear control of an underwater vehicle/manipulator system with composite dynamics

The paper is devoted to the problem of nonlinear robust control design for underwater vehicle/manipulator (UVM) systems composed of a freefloating platform equipped with a robot manipulator. The different bandwidth characteristics of the composite vehicle/arm dynamics are used as a basis for the control design via singular perturbation theory. The main contribution of this paper is that a robust nonlinear control is only required in the slow-subsystem (vehicle dynamics). Thus, this control is only used to compensate the coupling effects from the arm to the base. The paper also presents a comparative study between simple PD, a partial linearized control and the nonlinear robust feedback.

Controlling an Uninstrumented Manipulator By Visual Servoing

In this paper we present a method to control the displacement of a robot arm with no proprioceptive sensor. The joint positions are not available and this manipulator is usually open-loop controlled. In order to get a more efficient control interface, we propose a closed-loop system based on an eye-to-hand visual servoing approach. We show that, using such an approach, measurement of the manipulator motion with proprioceptive sensors is not required to precisely control the end-effector motion. We propose solutions for position-based control and velocity control of the manipulator. To maintain the end effector in the camera field of view, the camera orientation is also controlled. Various results show the validity and the efficiency of the approach.

Performance oriented robust nonlinear control for subsea robots: experimental validation

This paper investigates the benefits of applying simple PID+nonlinear controller to subsea robot. This control structure has the advantage of only adding a supplementary nonlinear feedback loop to the existing linear PID-regulator and at the same time improving both the transient and stability margins. Several simulations and experiments have been performed on the experimental subsea robot (VORTEX) and have demonstrated the improvements of the PID+nonlinear controller over the simple PID.<<ETX>>

Control of underwater vehicle/manipulator with composite dynamics

This paper is devoted to the problem of control design of an underwater vehicle/manipulator (UVM) system composed of a free navigating platform equipped with a robot manipulator. This composite system is driven by actuators and sensors of different nature having substantially different bandwidth characteristics. Such a difference allows for a setup which can naturally treated by standard singular perturbation theory. The major finding here is that the computed torque control law can be substantially simplified while preserving the closed-loop stability, in the sense of perturbation theory.

ADVOCATE II: ADVanced On-Board Diagnosis and Control of Autonomous Systems II

A way to improve the reliability and to reduce costs in autonomous robots is to add intelligence to on-board diagnosis and control systems to avoid expensive hardware redundancy and inopportune mission abortion. According to this, the main goal of the ADVOCATE II project is to adapt legacy piloting software around a generic SOAP (Simple Object Access Protocol) architecture on which intelligent modules could be plugged. Artificial Intelligent (AI) modules using Belief Bayesian Networks (BBN), Neuro-Symbolic Systems (NSS), and Fuzzy Logic (FL) are coordinated to help the operator or piloting system manage fault detection, risk assessment, and recovery plans. In this paper, the specification of the ADVOCATE II system is presented.

Controlling the manipulator of an underwater ROV using a coarse calibrated pan/tilt camera

We present a vision-based method to control the displacement of robot arm mounted on an underwater remotely operated vehicle (ROV). A closed-loop system based on an eye-to-hand visual servoing approach has been designed to achieve this task. We show that, using such an approach, the measuring of the manipulator motion with proprioceptive sensors is not required to precisely control the end-effector motion. To maintain the end effector in the field of view, the camera orientation is also controlled. The results presented show the validity of the approach.

Joint evaluation of mission programming for underwater robots

Underwater robotic systems require a control architecture that handles automatic control aspects and discrete-event management while considering real-time issues within a formalized framework in order to achieve a high degree of autonomy and robustness while performing missions. To extract generic characteristics of working implementations, we examine two methodologies developed independently by French and American research organizations to control their underwater robots. In particular, we study how a specific reactive and complex mission is encoded under the two different methodologies. Details of the methodologies along with mission programs created by each team to accomplish the evaluation mission are presented.