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We report numerical and experimental results indicating successful stabilization of unstable steady states and periodic orbits in an electrochemical system. Applying a continuous delayed-feedback technique not only periodic and chaotic oscillations are suppressed via stabilization of steady-state solutions but also the chaotic dynamics can be converted to periodic behavior. In all cases the feedback perturbation vanishes as a target state is attained.

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Les associations administratives des systèmes d’aqueducs et d’égouts au Costa Rica approvisionnent une grande partie de l’eau à la population rurale. Ces associations réclament de plus grandes compétences légales et de ressources financières afin d’améliorer la distribution de l’eau, d’assurer la protection des sources aquifères, d’augmenter l’autonomisation de leurs employés et de fournir une éducation environnementale aux utilisateurs de l’eau. L’État fera face à ce défi et tentera de remplir ces demandes à travers la décentralisation institutionnelle et une plus grande autonomie, mais sans renoncer à assurer un accès adéquat et suffisant aux sources d’eau potables.

We report experimental control of complex (periodic and chaotic) oscillatory dynamics in an electrochemical system by applying a nonfeedback control method. By choosing an appropriate frequency for the periodic modulation of an accessible control parameter (e.g., circuit potential) not only are the chaotic dynamics converted to regular periodic behavior (controlling chaos) but also the character of the oscillatory dynamics is altered (for example, 1 → 10). This is different from previously reported experiments involving simple entrainment of oscillatory dynamics, since in our experiments the frequency of sinusoidal modulation is chosen such that the existing unstable dynamics are targeted and subsequently stabilized. Consequently, the maximum amplitude of the control signal is less than ±5% of its base value. Since resonant control strategy can be easily implemented without a complicated precontrol procedure it seems relevant for applications to real systems.