Gregory Dubus

A vision-based method for estimating vibrations of a flexible arm using on-line sinusoidal regression

A vision-based vibration suppression scheme has previously been proposed to control the vibrational behaviour of long-reach arms operating in fusion reactors. In this paper we describe a new method to reconstruct the vibration using sinusoidal regression. This change makes the overall scheme more efficient since it enables the estimation of the tip oscillation whatever its origin may be. Both an exact solution and a simplified method are proposed to solve the regression problem. To limit the trade-off between good tracking capability and quality of the vibration reconstruction, these regression algorithms are performed over a variable-length sliding window. Consequently this paper also describes the change detection scheme used to automatically adjust the window length. Experimental results validate the proposed method.

On-line estimation of time varying capture delay for vision-based vibration control of flexible manipulators deployed in hostile environments

Thanks to recent advances in machine vision technology, vibration control of flexible manipulators using cameras have recently led to very promising results. However, in methods such as on-line sinusoidal regression [1], synchronization between the measured signal and the physical vibrational phenomenon is critical to properly damp vibrations. This paper comes back on the capture delay estimation as done in previous works and highlights the limitations of such a method. Then a new method using a synchronization sensor is proposed. Based on a cross-correlation technique, a novel algorithm for effective time delay estimation is derived. Experimental validation demonstrates that this method yields improved delay estimation which could be beneficial to the vibration damping.

Making hydraulic manipulators cleaner and safer: From oil to demineralized water hydraulics

This paper presents the developments carried out at CEA LIST to adapt the 6-DOF hydraulic manipulator Maestro to work with pure water instead of oil. Its elbow joint has been redesigned for water applications and a prototype of water hydraulic pressure servovalve has been manufactured. Both performances of the actuator and its pre-actuator are discussed. A model of the servovalve is proposed to identify its driving parameters and validate the next evolutions in its design, anticipating the second generation of prototypes.

Status of the design refinement and the characterisation of the in Vessel Viewing system for ITER

The paper describes the key concepts of the In Vessel Viewing System probe in phase of design refinement in ENEA Frascati laboratories and presents an integrated survey both on the design activities and the numerous test activities that have been performed to characterize the system and to verify the compliance of its key elements with the ITER environmental conditions.