Nicolas Loix

Active damping of a stiff beam-like structure with acceleration feedback

This paper describes a local control scheme using acceleration feedback and a colocated proof-mass actuator for active damping of structures. The closed-loop system is unconditionally stable. The control law is implemented digitally on a stiff beam (f1=68 Hz) representative of an optical test bench. The modal damping ratio is improved from below 0.2 percent to above 4 percent.

Novel electrode concept for spatial filtering with piezoelectric films: experimental validation

This paper describes and demonstrates a technology for making distributed sensors with spatial filtering properties. The concept is based on a porous electrode with variable porosity, which allows to tailor the effective piezoelectric coefficients in two dimensions. Two applications are considered: (i) a modal filter for a cantilever beam, and (ii) a volume displacement sensor for a simply supported plate.

Spatial Filtering with Discrete Array Sensors and Distributed PVDF Films

There are two broad ways to achieve spatial filtering: (i) arrays of discrete sensors and (ii) continuous distributed sensors. Discrete sensor arrays may include accelerometers, strain gages, piezoelectric patches, etc..., while continuous distributed sensors may consist of piezoelectric films or optical fibers (the latter will not be considered in this study). The output of a piezoelectric sensor is a weighted average of the surface strains in the region covered by the electrodes on the film.

Active damping of tension truss structures

This paper presents a strategy for active damping of cable structures. The control algorithm has guaranteed stability, including at the parametric resonance. The paper also describes an efficient modelling technique for cable structures; simple and powerful results are established, which allow to predict the closed loop poles with a root locus technique.