Rather than using the popular metric approach, characterization of chaotic attractors is obtained using the topological approach (first-return map to Poincaré section, template or knot-holder, symbolic dynamics, etc.). A particular attention is paid to symmetry properties.
Another issue also deeply investigated concerns global modelling techniques from experimental data. The aim is to obtain a set of differential or difference equations from a recorded time series. In particular, the influence of the choice of the observable is studied. Thus, it has been shown that some variable (a physical quantity) provides a representation of the dynamics which is better than another variable. All of these techniques have been applied to many different experimental systems conducted by collaborators (electrodissolution, jet atomisation, plasma, combustion in car engines, hydrodynamical systems, pulsating stars, sunsport numbers, ...).