607 research outputs found
Incremental embodied chaotic exploration of self-organized motor behaviors with proprioceptor adaptation
This paper presents a general and fully dynamic embodied artificial neural system, which incrementally explores and learns motor behaviors through an integrated combination of chaotic search and reflex learning. The former uses adaptive bifurcation to exploit the intrinsic chaotic dynamics arising from neuro-body-environment interactions, while the latter is based around proprioceptor adaptation. The overall iterative search process formed from this combination is shown to have a close relationship to evolutionary methods. The architecture developed here allows realtime goal-directed exploration and learning of the possible motor patterns (e.g., for locomotion) of embodied systems of arbitrary morphology. Examples of its successful application to a simple biomechanical model, a simulated swimming robot, and a simulated quadruped robot are given. The tractability of the biomechanical systems allows detailed analysis of the overall dynamics of the search process. This analysis sheds light on the strong parallels with evolutionary search
Integrated chaos generators
This paper surveys the different design issues, from mathematical model to silicon, involved on the design of integrated circuits for the generation of chaotic behavior.Comisión Interministerial de Ciencia y Tecnología 1FD97-1611(TIC)European Commission ESPRIT 3110
Symmetry in Chaotic Systems and Circuits
Symmetry can play an important role in the field of nonlinear systems and especially in the design of nonlinear circuits that produce chaos. Therefore, this Special Issue, titled “Symmetry in Chaotic Systems and Circuits”, presents the latest scientific advances in nonlinear chaotic systems and circuits that introduce various kinds of symmetries. Applications of chaotic systems and circuits with symmetries, or with a deliberate lack of symmetry, are also presented in this Special Issue. The volume contains 14 published papers from authors around the world. This reflects the high impact of this Special Issue
Dynamics of resonant tunneling diode optoelectronic oscillators
Tese de dout., Física, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012The nonlinear dynamics of optoelectronic integrated circuit (OEIC) oscillators comprising
semiconductor resonant tunneling diode (RTD) nanoelectronic quantum devices
has been investigated. The RTD devices used in this study oscillate in the microwave
band frequency due to the negative di erential conductance (NDC) of their nonlinear
current voltage characteristics, which is preserved in the optoelectronic circuit. The
aim was to study RTD circuits incorporating laser diodes and photo-detectors to obtain
novel dynamical operation regimes in both electrical and optical domains taking
advantage of RTD's NDC characteristic.
Experimental implementation and characterization of RTD-OEICs was realized in
parallel with the development of computational numerical models. The numerical models
were based on ordinary and delay di erential equations consisting of a Li enard's
RTD oscillator and laser diode single mode rate equations that allowed the analysis
of the dynamics of RTD-OEICs. In this work, several regimes of operation are
demonstrated, both experimentally and numerically, including generation of voltage
controlled microwave oscillations and synchronization to optical and electrical external
signals providing stable and low phase noise output signals, and generation of complex
oscillations that are characteristic of high-dimensional chaos.
Optoelectronic integrated circuits using RTD oscillators are interesting alternatives
for more e cient synchronization, generation of stable and low phase noise microwave
signals, electrical/optical conversion, and for new ways of optoelectronic chaos generation.
This can lead to simpli cation of communication systems by boosting circuits
speed while reducing the power and number of components. The applications of
RTD-OEICs include operation as optoelectronic voltage controlled oscillators in clock
recovery circuit systems, in wireless-photonics communication systems, or in secure
communication systems using chaotic waveforms
Optical computing by injection-locked lasers
A programmable optical computer has remained an elusive concept. To construct
a practical computing primitive equivalent to an electronic Boolean logic, one
should find a nonlinear phenomenon that overcomes weaknesses present in many
optical processing schemes. Ideally, the nonlinearity should provide a
functionally complete set of logic operations, enable ultrafast all-optical
programmability, and allow cascaded operations without a change in the
operating wavelength or in the signal encoding format. Here we demonstrate a
programmable logic gate using an injection-locked Vertical-Cavity
Surface-Emitting Laser (VCSEL). The gate program is switched between the AND
and the OR operations at the rate of 1 GHz with Bit Error Ratio (BER) of 10e-6
without changes in the wavelength or in the signal encoding format. The scheme
is based on nonlinearity of normalization operations, which can be used to
construct any continuous complex function or operation, Boolean or otherwise.Comment: 47 pages, 7 figures in total, 2 tables. Intended for submission to
Nature Physics within the next two week
- …