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2nd International Conference on Control and Fault-Tolerant Systems (SysTol)

作者： Koenings, Tim Esch, Jonas Kandler, Christoph Ding, Steven X. Louen, Chris Univ Duisburg Essen Inst Automat Control & Complex Syst AKS D-47057 Duisburg Germany

ISBN: (纸本)9781479928552

In this paper we consider the problem of tuning a PI-controller for robust, optimal performance with an integrator plus delay plant with varying plant parameters. The integrated absolute error for set-point tracking is considered as the performance index to be minimised by tuning. To this end, classical worst case and mean value based techniques for robust, performance optimal controller tuning are discussed. It is shown that these techniques require the consideration of an infinite amount of possible plant parameters in the optimisation step and are thus infeasible. To overcome this, we adopt randomised algorithms that allow an approximation of the original problem with a finite number of plant parameter samples in every step. Furthermore, we show that the minimisation problems to be solved in the randomised algorithm are convex and can thus be solved to their global minimiser, using readily available iterative algorithms. This is shown to introduce convexity of the set of stabilising controller parameters as a necessary condition, which is proven to hold for the problems considered here. Application of the proposed algorithm is shown for the tuning of a level controller in a continuous stirred tank heater demonstrator plant.

关键词： PI control control system synthesis delays iterative methods minimisation optimal control performance index randomised algorithms robust control variable structure systems

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randomised subspace system identification: complexities and error bounds

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INTERNATIONAL JOURNAL OF CONTROL 2025年

作者： Kedia, Vatsal Chakraborty, Debraj Indian Inst Technol Dept Elect Engn Mumbai 400076 India

Recently, a novel randomised subspace system identification method (RandSID) for estimating LTI state-space models was proposed in Kedia, V., & Chakraborty, D. (2023), which aimed to address the computational issues faced by traditional subspace identification methods when the recorded dataset is large. In this article, we propose a modified version of RandSID and analyse the complexity of this proposed algorithm in terms of memory cost, data movement, flop count and computation time, and quantitatively establish the computational advantages over conventional algorithms. Further, we derive a bound on the ratio of mean squared errors for the proposed and conventional algorithms, thereby characterising the loss of accuracy specifically due to randomisation. The effectiveness of the proposed algorithm is established by various real and simulated case studies.

关键词： System Identification Subspace Identification Identification for Control randomised algorithms State-space modeling

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Control analysis and design via randomised coordinate polynomial minimisation

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INTERNATIONAL JOURNAL OF CONTROL 2022年第1期95卷 158-172页

作者： Calafiore, Giuseppe C. Novara, Carlo Possieri, Corrado Politecn Torino Dipartimento Elettron & Telecomunicaz Turin Italy Consiglio Nazl Ric IASI CNR Ist Anal Sistemi & Informat A Ruberti Turin Italy Consiglio Nazl Ric IASI CNR Ist Anal Sistemi & Informat A Ruberti Via Taurini 19 I-00185 Rome Italy

A relevant family of control analysis and design problems can be reduced to the minimisation of a multivariate polynomial objective over a semialgebraic set. Such control problem formulations, however, are nonconvex in general and hard to solve in practice. In this paper, we propose a novel approach to polynomial control design based on iterations that involve either a fast coordinate-wise minimisation or a univariate minimisation along a randomly chosen direction. We provide a detailed iteration complexity analysis of the method, and we prove its convergence in probability to the global optimum. The practical effectiveness of the proposed method is also illustrated via a comparison with state-of-the-art tools available in the literature. An example of application to an automated space rendezvous manoeuvre is finally presented, showing how the method can be particularly relevant in the context of nonlinear model predictive control.

关键词： Nonlinear control optimisation methods randomised algorithms robustness optimal control

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On a new generalised LMI condition and randomised algorithm for robust stabilisation via static-output-feedback

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INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE 2020年第1期51卷 61-71页

作者： Peretz, Y. Merzbach, O. Moyall, S. Jerusalem Coll Technol Lev Acad Ctr Comp Sci Dept POB 16031 Jerusalem Israel

For a given system with time-invariant affine uncertainties, ranging in a unit hypercube or, equivalently, in a hyper-rectangle, new LMI sufficient conditions for the verification of a given simultaneous static-output-feedback for hypercube nodes, being robust static-output-feedback for the whole system, are proved. The conditions generalise previous results in the sense that we do not assume that the state-to-measurement or the input-to-state matrix is constant. Based on the LMI conditions, a randomised algorithm is suggested. The effectiveness of the method is reinforced through experiments on real-life systems.

关键词： Continuous-time linear systems State-space representation Feedback stability Robust stabilisabiliy Simultaneous stabilisation Static-output-feedbacks NP-hard control problems randomised algorithms

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A randomised approach for NARX model identification based on a multivariate Bernoulli distribution

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INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE 2017年第6期48卷 1203-1216页

作者： Bianchi, F. Falsone, A. Prandini, M. Piroddi, L. Politecn Milan Dipartimento Elettron Informaz Bioingn Milan Italy

The identification of polynomial NARX models is typically performed by incremental model building techniques. These methods assess the importance of each regressor based on the evaluation of partial individual models, which may ultimately lead to erroneous model selections. A more robust assessment of the significance of a specific model term can be obtained by considering ensembles of models, as done by the RaMSS algorithm. In that context, the identification task is formulated in a probabilistic fashion and a Bernoulli distribution is employed to represent the probability that a regressor belongs to the target model. Then, samples of the model distribution are collected to gather reliable information to update it, until convergence to a specific model. The basic RaMSS algorithm employs multiple independent univariate Bernoulli distributions associated to the different candidate model terms, thus overlooking the correlations between different terms, which are typically important in the selection process. Here, a multivariate Bernoulli distribution is employed, in which the sampling of a given term is conditioned by the sampling of the others. The added complexity inherent in considering the regressor correlation properties is more than compensated by the achievable improvements in terms of accuracy of the model selection process.

关键词： Nonlinear model identification model structure selection polynomial NARX models randomised algorithms multivariate Bernoulli distribution prediction error minimisation methods

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randomised multi-modulo residue number system architecture for double-and-add to prevent power analysis side channel attacks

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IET CIRCUITS DEVICES & SYSTEMS 2013年第5期7卷 283-293页

作者： Ambrose, Jude Angelo Pettenghi, Hector Jayasinghe, Darshana Sousa, Leonel Univ New S Wales Sch Engn & Comp Sci Sydney NSW Australia Inst Super Tecn Inst Engn Sistemas & Comp INESC ID P-1000029 Lisbon Portugal

Security in embedded systems is of critical importance since most of our secure transactions are currently made via credit cards or mobile phones. Power analysis-based side channel attacks have been proved as the most successful attacks on embedded systems to retrieve secret keys, allowing impersonation and theft. State-of-the-art solutions for such attacks on public key cryptographic algorithms, such as elliptic curve cryptography, mostly in software, hinder performance and repeatedly attacked using improved techniques. To protect these public key ciphers from both simple power analysis and differential power analysis, as a hardware solution, we propose to take advantage of the inherent parallelisation capability in multi-modulo residue number systems (RNS) architectures to obfuscate the secure information. Random selection of moduli is proposed to randomly choose the moduli sets for each key bit operation. This solution allows us to prevent power analysis, although still providing all the benefits of RNS. In this study, the authors show that differential power analysis, cross correlation analysis and correlation power analysis for a simple binary double-and-add operation are thwarted using their solution.

关键词： correlation methods data privacy embedded systems public key cryptography randomised algorithms residue number systems randomised multimodulo residue number system architecture power analysis side channel attack prevention embedded security system mobile phone credit card secret key retrieval public key cryptographic algorithm elliptic curve cryptography public key cipher RNS differential power analysis cross correlation power analysis binary double-and-add operation

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Energy efficient randomised communication in unknown AdHoc networks

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THEORETICAL COMPUTER SCIENCE 2009年第27-29期410卷 2549-2561页

作者： Berenbrink, Petra Cooper, Colin Hu, Zengjian D Wave Syst Burnaby Software Technol Burnaby BC V5C 6G9 Canada Simon Fraser Univ Sch Comp Sci Burnaby BC V5A 1S6 Canada Kings Coll London Dept Comp Sci London WC2R 2LS England

This paper Studies broadcasting and gossiping algorithms in random and general AdHoc networks. Our goal is not only to minimise the broadcasting and gossiping time, but also to minimise the energy consumption, which is measured in terms of the total number of messages (or transmissions) sent. We assume that the nodes of the network do not know the network, and that they can only send with a fixed power, meaning they can not adjust the area sizes that their messages cover. We believe that under these circumstances the number of transmissions is a very good measure for the overall energy consumption. For random networks, we present a broadcasting algorithm where every node transmits at most once. We show that our algorithm broadcasts in O(log n) steps, w.h.p., where n is the number of nodes. We then present a O(d log n) (d is the expected degree) gossiping algorithm using O(log n) messages per node. For general networks with known diameter D, we present a randomised broadcasting algorithm with optimal broadcasting time O(D log(n/D) + log(2) n) that uses all expected number of O(log(2) n/log(n/D)) transmissions per node. We also show a tradeoff result between the broadcasting time and the number of transmissions: we construct a network Such that any oblivious algorithm using a time-invariant distribution requires Omega(log(2) n/log(n/D)) messages per node in order to finish broadcasting in optimal time. This demonstrates the tightness of our upper bound. We also show that no Oblivious algorithm call complete broadcasting w.h.p. using o(log n) messages per node. (C) 2009 Published by Elsevier B.V.

关键词： AdHoc networks Broadcasting Gossiping randomised algorithms

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A simple randomised algorithm for convex optimisation

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MATHEMATICAL PROGRAMMING 2014年第1-2期147卷 207-229页

作者： Dyer, M. Kannan, R. Stougie, L. Univ Leeds Dept Comp Sci Leeds W Yorkshire England Microsoft Res Labs Bangalore Karnataka India Vrije Univ Amsterdam Div Econometr & Operat Res Dept Econ & Business Adm Amsterdam Netherlands CWI NL-1090 GB Amsterdam Netherlands

We consider maximising a concave function over a convex set by a simple randomised algorithm. The strength of the algorithm is that it requires only approximate function evaluations for the concave function and a weak membership oracle for the convex set. Under smoothness conditions on the function and the feasible set, we show that our algorithm computes a near-optimal point in a number of operations which is bounded by a polynomial function of all relevant input parameters and the reciprocal of the desired precision, with high probability. As an application to which the features of our algorithm are particularly useful we study two-stage stochastic programming problems. These problems have the property that evaluation of the objective function is #P-hard under appropriate assumptions on the models. Therefore, as a tool within our randomised algorithm, we devise a fully polynomial randomised approximation scheme for these function evaluations, under appropriate assumptions on the models. Moreover, we deal with smoothing the feasible set, which in two-stage stochastic programming is a polyhedron.

关键词： Convex optimisation Stochastic programming randomised algorithms Polynomial time randomised approximation scheme

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A randomised algorithm for computing static-output-feedbacks for large-scale systems

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INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE 2019年第16期50卷 2898-2917页

作者： Peretz, Y. Wu, W. Jerusalem Coll Technol Lev Acad Ctr Dept Comp Sci POB 16031 Jerusalem Israel Southwest Jiaotong Univ Sch Elect Engn Chengdu Sichuan Peoples R China

A randomised algorithm is proposed for computing globally optimal static-output-feedbacks for large-scale systems. The algorithm is based on the Ray-Shooting Method and involves some heuristics to accelerate the search. We also improve the basic Ray-Shooting Algorithm and make the search in the controller parameter-space (which generally, is much more smaller than the certificate parameter-space), thus enabling its efficient use for large-scale systems.

关键词： Continuous-time systems large-scale control systems large structures feedback stability static-output-feedbacks approximation algorithms randomised algorithms the Ray-Shooting method convergence in probability heuristics

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Design of a randomised arrangement AMC surfaces for RCS reduction based on equivalent circuit modelling

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IET MICROWAVES ANTENNAS & PROPAGATION 2018年第10期12卷 1684-1690页

作者： Varkani, Ali Ramezani Firouzeh, Zaker Hossein Nezhad, Abolghasem Zeidaabadi Isfahan Univ Technol Dept Elect & Comp Engn Esfahan *** Iran

This study aims to present a thin and broadband meta-surface for both mono-static and bi-static radar cross-section (RCS) reduction being able to operate in large range of incident angles and different polarisations. Meta-surfaces are formed through the combination of two artificial magnetic conductor (AMC) cells arranged in periodic and randomised fashions in order to suppress the scattered fields in low levels in all directions as well as minimising the maximum RCS of the metallic surface. By appropriate design of each AMC, and using equivalent circuit method, the reflection coefficients of these surfaces are designed in a way to reach 180 (+/- 37 degrees) phase difference over a wide range of frequencies and incident angles. The bandwidth for 10dB mono-static RCS reduction is about 53% for both periodic and randomised structures at the normal incidence. It is illustrated that the randomised arrangement structure has 3dB lower maximum bi-static RCS compared with the periodic structure. Finally, the periodic and randomised arrangement prototypes are fabricated and measurements of their mono-static RCS are conducted. The validity of the study design is fulfilled by achieving an acceptable agreement between the measured and simulated results.

关键词： radar cross-sections equivalent circuits randomised algorithms frequency selective surfaces electromagnetic metamaterials electromagnetic wave polarisation randomised arrangement AMC surface monostatic RCS reduction equivalent circuit modelling broadband metasurface monostatic radar cross-section reduction bistatic radar cross-section reduction polarisation artificial magnetic conductor equivalent circuit method reflection coefficient bistatic RCS reduction periodic structure angular stability gain 10 dB

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