1,969 research outputs found
A new criterion of delay-dependent asymptotic stability for Hopfield neural networks with time delay
In this brief, the problem of global asymptotic stability for delayed Hopfield neural networks (HNNs) is investigated. A new criterion of asymptotic stability is derived by introducing a new kind of Lyapunov-Krasovskii functional and is formulated in terms of a linear matrix inequality (LMI), which can be readily solved via standard software. This new criterion based on a delay fractioning approach proves to be much less conservative and the conservatism could be notably reduced by thinning the delay fractioning. An example is provided to show the effectiveness and the advantage of the proposed result. © 2008 IEEE.published_or_final_versio
Validation of Neural Network Controllers for Uncertain Systems Through Keep-Close Approach: Robustness Analysis and Safety Verification
Among the major challenges in neural control system technology is the
validation and certification of the safety and robustness of neural network
(NN) controllers against various uncertainties including unmodelled dynamics,
non-linearities, and time delays. One way in providing such validation
guarantees is to maintain the closed-loop system output with a NN controller
when its input changes within a bounded set, close to the output of a robustly
performing closed-loop reference model. This paper presents a novel approach to
analysing the performance and robustness of uncertain feedback systems with NN
controllers. Due to the complexity of analysing such systems, the problem is
reformulated as the problem of dynamical tracking errors between the
closed-loop system with a neural controller and an ideal closed-loop reference
model. Then, the approximation of the controller error is characterised by
adopting the differential mean value theorem (DMV) and the Integral Quadratic
Constraints (IQCs) technique. Moreover, the Relative Integral Square Error
(RISE) and the Supreme Square Error (SSE) bounded set are derived for the
output of the error dynamical system. The analysis is then performed by
integrating Lyapunov theory with the IQCs-based technique. The resulting
worst-case analysis provides the user a prior knowledge about the worst case of
RISE and SSE between the reference closed-loop model and the uncertain system
controlled by the neural controller. The suitability of the proposed technique
is demonstrated by the results obtained on a nonlinear single-link robot system
with a NN trained to control the movement of this mechanical system while
keeping close to an ideal closed-loop reference model.Comment: 19 pages, 10 figures, Journal Paper submitted to IEEE Transactions on
Control Systems Technolog
The time dimension of neural network models
This review attempts to provide an insightful perspective on the role of time within neural network models and the use of neural networks for problems involving time. The most commonly used neural network models are defined and explained giving mention to important technical issues but avoiding great detail. The relationship between recurrent and feedforward networks is emphasised, along with the distinctions in their practical and theoretical abilities. Some practical examples are discussed to illustrate the major issues concerning the application of neural networks to data with various types of temporal structure, and finally some highlights of current research on the more difficult types of problems are presented
Comparative evaluation of approaches in T.4.1-4.3 and working definition of adaptive module
The goal of this deliverable is two-fold: (1) to present and compare different approaches towards learning and encoding movements us- ing dynamical systems that have been developed by the AMARSi partners (in the past during the first 6 months of the project), and (2) to analyze their suitability to be used as adaptive modules, i.e. as building blocks for the complete architecture that will be devel- oped in the project. The document presents a total of eight approaches, in two groups: modules for discrete movements (i.e. with a clear goal where the movement stops) and for rhythmic movements (i.e. which exhibit periodicity). The basic formulation of each approach is presented together with some illustrative simulation results. Key character- istics such as the type of dynamical behavior, learning algorithm, generalization properties, stability analysis are then discussed for each approach. We then make a comparative analysis of the different approaches by comparing these characteristics and discussing their suitability for the AMARSi project
Interpretable PID Parameter Tuning for Control Engineering using General Dynamic Neural Networks: An Extensive Comparison
Modern automation systems rely on closed loop control, wherein a controller
interacts with a controlled process, based on observations. These systems are
increasingly complex, yet most controllers are linear
Proportional-Integral-Derivative (PID) controllers. PID controllers perform
well on linear and near-linear systems but their simplicity is at odds with the
robustness required to reliably control complex processes. Modern machine
learning offers a way to extend PID controllers beyond their linear
capabilities by using neural networks. However, such an extension comes at the
cost of losing stability guarantees and controller interpretability. In this
paper, we examine the utility of extending PID controllers with recurrent
neural networks-namely, General Dynamic Neural Networks (GDNN); we show that
GDNN (neural) PID controllers perform well on a range of control systems and
highlight how they can be a scalable and interpretable option for control
systems. To do so, we provide an extensive study using four benchmark systems
that represent the most common control engineering benchmarks. All control
benchmarks are evaluated with and without noise as well as with and without
disturbances. The neural PID controller performs better than standard PID
control in 15 of 16 tasks and better than model-based control in 13 of 16
tasks. As a second contribution, we address the lack of interpretability that
prevents neural networks from being used in real-world control processes. We
use bounded-input bounded-output stability analysis to evaluate the parameters
suggested by the neural network, thus making them understandable. This
combination of rigorous evaluation paired with better interpretability is an
important step towards the acceptance of neural-network-based control
approaches. It is furthermore an important step towards interpretable and
safely applied artificial intelligence
Literature Review on Big Data Analytics Methods
Companies and industries are faced with a huge amount of raw data, which have information and knowledge in their hidden layer. Also, the format, size, variety, and velocity of generated data bring complexity for industries to apply them in an efficient and effective way. So, complexity in data analysis and interpretation incline organizations to deploy advanced tools and techniques to overcome the difficulties of managing raw data. Big data analytics is the advanced method that has the capability for managing data. It deploys machine learning techniques and deep learning methods to benefit from gathered data. In this research, the methods of both ML and DL have been discussed, and an ML/DL deployment model for IOT data has been proposed
Bacterial Foraging Based Channel Equalizers
A channel equalizer is one of the most important subsystems in any digital
communication receiver. It is also the subsystem that consumes maximum computation
time in the receiver. Traditionally maximum-likelihood sequence estimation (MLSE) was
the most popular form of equalizer. Owing to non-stationary characteristics of the
communication channel MLSE receivers perform poorly. Under these circumstances
‘Maximum A-posteriori Probability (MAP)’ receivers also called Bayesian receivers
perform better.
Natural selection tends to eliminate animals with poor “foraging strategies” and favor the
propagation of genes of those animals that have successful foraging strategies since they
are more likely to enjoy reproductive success. After many generations, poor foraging
strategies are either eliminated or shaped into good ones (redesigned). Logically, such
evolutionary principles have led scientists in the field of “foraging theory” to
hypothesize that it is appropriate to model the activity of foraging as an optimization
process.
This thesis presents an investigation on design of bacterial foraging based channel
equalizer for digital communication. Extensive simulation studies shows that the
performance of the proposed receiver is close to optimal receiver for variety of channel
conditions. The proposed receiver also provides near optimal performance when channel
suffers from nonlinearities
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