514 research outputs found
Bio-Inspired Stereo Vision Calibration for Dynamic Vision Sensors
Many advances have been made in the eld of computer vision. Several recent research trends
have focused on mimicking human vision by using a stereo vision system. In multi-camera systems, a
calibration process is usually implemented to improve the results accuracy. However, these systems generate
a large amount of data to be processed; therefore, a powerful computer is required and, in many cases,
this cannot be done in real time. Neuromorphic Engineering attempts to create bio-inspired systems that
mimic the information processing that takes place in the human brain. This information is encoded using
pulses (or spikes) and the generated systems are much simpler (in computational operations and resources),
which allows them to perform similar tasks with much lower power consumption, thus these processes
can be developed over specialized hardware with real-time processing. In this work, a bio-inspired stereovision
system is presented, where a calibration mechanism for this system is implemented and evaluated
using several tests. The result is a novel calibration technique for a neuromorphic stereo vision system,
implemented over specialized hardware (FPGA - Field-Programmable Gate Array), which allows obtaining
reduced latencies on hardware implementation for stand-alone systems, and working in real time.Ministerio de Economía y Competitividad TEC2016-77785-PMinisterio de Economía y Competitividad TIN2016-80644-
An AER-Based Actuator Interface for Controlling an Anthropomorphic Robotic Hand
Bio-Inspired and Neuro-Inspired systems or circuits are a
relatively novel approaches to solve real problems by mimicking the biology
in its efficient solutions. Robotic also tries to mimic the biology and
more particularly the human body structure and efficiency of the muscles,
bones, articulations, etc. Address-Event-Representation (AER) is
a communication protocol for transferring asynchronous events between
VLSI chips, originally developed for neuro-inspired processing systems
(for example, image processing). Such systems may consist of a complicated
hierarchical structure with many chips that transmit data among
them in real time, while performing some processing (for example, convolutions).
The information transmitted is a sequence of spikes coded using
high speed digital buses. These multi-layer and multi-chip AER systems
perform actually not only image processing, but also audio processing,
filtering, learning, locomotion, etc. This paper present an AER interface
for controlling an anthropomorphic robotic hand with a neuro-inspired
system.Unión Europea IST-2001-34124 (CAVIAR)Ministerio de Ciencia y Tecnología TIC-2003-08164-C03-0
On the AER Convolution Processors for FPGA
Image convolution operations in digital computer
systems are usually very expensive operations in terms of
resource consumption (processor resources and processing time)
for an efficient Real-Time application. In these scenarios the
visual information is divided into frames and each one has to be
completely processed before the next frame arrives in order to
warranty the real-time. A spike-based philosophy for computing
convolutions based on the neuro-inspired Address-Event-
Representation (AER) is achieving high performances. In this
paper we present two FPGA implementations of AER-based
convolution processors for relatively small Xilinx FPGAs
(Spartan-II 200 and Spartan-3 400), which process 64x64 images
with 11x11 convolution kernels. The maximum equivalent
operation rate that can be reached is 163.51 MOPS for 11x11
kernels, in a Xilinx Spartan 3 400 FPGA with a 50MHz clock.
Formulations, hardware architecture, operation examples and
performance comparison with frame-based convolution
processors are presented and discussed.Ministerio de Ciencia e Innovación TEC2006-11730-C03-02Ministerio de Ciencia e Innovación TEC2009-10639-C04-02Junta de Andalucía P06-TIC-0141
Real time unsupervised learning of visual stimuli in neuromorphic VLSI systems
Neuromorphic chips embody computational principles operating in the nervous
system, into microelectronic devices. In this domain it is important to
identify computational primitives that theory and experiments suggest as
generic and reusable cognitive elements. One such element is provided by
attractor dynamics in recurrent networks. Point attractors are equilibrium
states of the dynamics (up to fluctuations), determined by the synaptic
structure of the network; a `basin' of attraction comprises all initial states
leading to a given attractor upon relaxation, hence making attractor dynamics
suitable to implement robust associative memory. The initial network state is
dictated by the stimulus, and relaxation to the attractor state implements the
retrieval of the corresponding memorized prototypical pattern. In a previous
work we demonstrated that a neuromorphic recurrent network of spiking neurons
and suitably chosen, fixed synapses supports attractor dynamics. Here we focus
on learning: activating on-chip synaptic plasticity and using a theory-driven
strategy for choosing network parameters, we show that autonomous learning,
following repeated presentation of simple visual stimuli, shapes a synaptic
connectivity supporting stimulus-selective attractors. Associative memory
develops on chip as the result of the coupled stimulus-driven neural activity
and ensuing synaptic dynamics, with no artificial separation between learning
and retrieval phases.Comment: submitted to Scientific Repor
Inter-spike-intervals analysis of AER Poisson-like generator hardware
Address–Event–Representation (AER) is a communication protocol for transferring images between chips, originally developed for
bio-inspired image-processing systems. Such systems may consist of a complicated hierarchical structure with many chips that transmit
images among them in real time, while performing some processing (for example, convolutions). In developing AER-based systems it is
very convenient to have available some means of generating AER streams from on-computer stored images. Rank order coding (ROC)
and Poisson rate coding are the extremes of spikes coding. In this paper, we present a pseudo-random hardware method for generating
AER streams in real time from a sequence of images stored in a computer’s memory. The Kolmogorov–Smirnov test has been applied to
quantify that this method follows a Poisson distribution of the spikes. A USB–AER board, developed by our RTCAR group, have been
used for the measurements. An example scenario of use under the EU CAVIAR project is presented.European Commission IST-2001-34124Ministerio de Ciencia y Tecnología TIC-2003-08164-C03-0
On the potential role of lateral connectivity in retinal anticipation
We analyse the potential effects of lateral connectivity (amacrine cells and
gap junctions) on motion anticipation in the retina. Our main result is that
lateral connectivity can-under conditions analysed in the paper-trigger a wave
of activity enhancing the anticipation mechanism provided by local gain control
[8, 17]. We illustrate these predictions by two examples studied in the
experimental literature: differential motion sensitive cells [1] and direction
sensitive cells where direction sensitivity is inherited from asymmetry in gap
junctions connectivity [73]. We finally present reconstructions of retinal
responses to 2D visual inputs to assess the ability of our model to anticipate
motion in the case of three different 2D stimuli
On Real-Time AER 2-D Convolutions Hardware for Neuromorphic Spike-Based Cortical Processing
In this paper, a chip that performs real-time image
convolutions with programmable kernels of arbitrary shape is presented.
The chip is a first experimental prototype of reduced size
to validate the implemented circuits and system level techniques.
The convolution processing is based on the address–event-representation
(AER) technique, which is a spike-based biologically
inspired image and video representation technique that favors
communication bandwidth for pixels with more information. As
a first test prototype, a pixel array of 16x16 has been implemented
with programmable kernel size of up to 16x16. The
chip has been fabricated in a standard 0.35- m complimentary
metal–oxide–semiconductor (CMOS) process. The technique also
allows to process larger size images by assembling 2-D arrays of
such chips. Pixel operation exploits low-power mixed analog–digital
circuit techniques. Because of the low currents involved (down
to nanoamperes or even picoamperes), an important amount of
pixel area is devoted to mismatch calibration. The rest of the
chip uses digital circuit techniques, both synchronous and asynchronous.
The fabricated chip has been thoroughly tested, both at
the pixel level and at the system level. Specific computer interfaces
have been developed for generating AER streams from conventional
computers and feeding them as inputs to the convolution
chip, and for grabbing AER streams coming out of the convolution
chip and storing and analyzing them on computers. Extensive
experimental results are provided. At the end of this paper, we
provide discussions and results on scaling up the approach for
larger pixel arrays and multilayer cortical AER systems.Commission of the European Communities IST-2001-34124 (CAVIAR)Commission of the European Communities 216777 (NABAB)Ministerio de Educación y Ciencia TIC-2000-0406-P4Ministerio de Educación y Ciencia TIC-2003-08164-C03-01Ministerio de Educación y Ciencia TEC2006-11730-C03-01Junta de Andalucía TIC-141
Automatic Tuning of a Retina Model for a Cortical Visual Neuroprosthesis Using a Multi-Objective Optimization Genetic Algorithm
The retina is a very complex neural structure, which contains many different types of neurons interconnected with great precision, enabling sophisticated conditioning and coding of the visual information before it is passed via the optic nerve to higher visual centers. The encoding of visual information is one of the basic questions in visual and computational neuroscience and is also of seminal importance in the field of visual prostheses. In this framework, it is essential to have artificial retina systems to be able to function in a way as similar as possible to the biological retinas. This paper proposes an automatic evolutionary multi-objective strategy based on the NSGA-II algorithm for tuning retina models. Four metrics were adopted for guiding the algorithm in the search of those parameters that best approximate a synthetic retinal model output with real electrophysiological recordings. Results show that this procedure exhibits a high flexibility when different trade-offs has to be considered during the design of customized neuro prostheses
Hardware design of LIF with Latency neuron model with memristive STDP synapses
In this paper, the hardware implementation of a neuromorphic system is
presented. This system is composed of a Leaky Integrate-and-Fire with Latency
(LIFL) neuron and a Spike-Timing Dependent Plasticity (STDP) synapse. LIFL
neuron model allows to encode more information than the common
Integrate-and-Fire models, typically considered for neuromorphic
implementations. In our system LIFL neuron is implemented using CMOS circuits
while memristor is used for the implementation of the STDP synapse. A
description of the entire circuit is provided. Finally, the capabilities of the
proposed architecture have been evaluated by simulating a motif composed of
three neurons and two synapses. The simulation results confirm the validity of
the proposed system and its suitability for the design of more complex spiking
neural network
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