Controlling sensori-motor systems in higher animals or complex robots is a challenging combinatorial problem, because many sensory signals need to be simultaneously coordinated into a broad behavioural spectrum. To rapidly interact with the environment, this control needs to be fast and adaptive. Present robotic solutions operate with limited autonomy and are mostly restricted to few behavioural patterns. Here we introduce chaos control as a new strategy to generate complex behaviour of an autonomous robot. In the presented system, 18 sensors drive 18 motors by means of a simple neural control circuit, thereby generating 11 basic behavioural patterns (for example, orienting, taxis, self-protection and various gaits) and their combinations. The control signal quickly and reversibly adapts to new situations and also enables learning and synaptic long-term storage of behaviourally useful motor responses. Thus, such neural control provides a powerful yet simple way to self-organize versatile behaviours in autonomous agents with many degrees of freedom

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The current-voltage (I-V) characteristics of industrially fabricated, crystalline silicon solar cells are often influenced by non-linear shunts that originate from localized, highly disturbed regions and cause ideality factors n >2. We show that recombination within such locations needs model descriptions that go beyond the Shockley-Read-Hall (SRH) approximation, because the density of defects is so high that recombination does not occur via isolated, but coupled defect states. We use a variant of coupled defect level (CDL) recombination, the donor-acceptor-pair (DAP) recombination, but via deep levels (as opposed to shallow levels). With this model, we quantitatively reproduce the I-V curves of solar cells that we subjected to various degrees of cleaving, laser scribing or diamond scratching to form shunt locations in a controlled manner. The suggested model explains the transition from ideality factors 2 when going from low to high defect densities. We also explain the non-saturating reverse I-V characteristics. We show that an additional source of currents with ngt;2 is SRH recombination in an inversion layer that extends from the front p-n junction to the rear contact along the cell's edge or along a micro-crack

The measured effective surface recombination velocity Seff at the interface between crystalline p-type silicon (p-Si) and amorphous silicon nitride (SiNx) layers increases with decreasing excess carrier density Δn<1015 cm−3 at dopant densities below 1017 cm−3. If such an interface is incorporated into Si solar cells, it causes their performance to deteriorate under low-injection conditions. With the present knowledge, this effect can neither be experimentally avoided nor fully understood. In this paper, Seff is theoretically reproduced in both p-type and n-type Si at all relevant Δn and all relevant dopant densities. The model incorporates a reduction in the Shockley–Read–Hall lifetime in the Si bulk near the interface, called the surface damage region (SDR). All of the parameters of the model are physically meaningful, and a parametrization is given for numerical device modeling. The model predicts that a ten-fold reduction in the density of defect states within the SDR is sufficient to weaken this undesirable effect to the extent that undiffused surfaces can be incorporated in Si solar cells. This may serve to simplify their fabrication procedures. We further discuss possible causes of the SDR and suggest implications for experiments.

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