SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
https://stccj.ucv.ro/index.php/stccj
<p>The System Theory, Control and Computing Journal – issued from merging of journals traditionally (along some half-century) edited by Control and Computing Engineering departments and faculties (schools) – is promoting theoretical and applied results in a large field of System Theory, Control and Computing (with particular reference to Applied Informatics and Applications in Systems and Control).</p> <p><span dir="ltr" role="presentation">ISSN: <strong>2810–4099</strong></span><br /><span dir="ltr" role="presentation">ISSN–L: <strong>2668–2966</strong></span></p>University of CraiovaenSYSTEM THEORY, CONTROL AND COMPUTING JOURNAL2668-2966Homogeneous Parametric Modeling of Airloads
https://stccj.ucv.ro/index.php/stccj/article/view/44
<p>This work proposes two parametric modeling strategies for steady aerodynamic forces. We point out that airloads are homogeneous and introduce a parametrization based on spherical harmonics and a neural network. The parametrization using spherical harmonics enables an analogue of frequency-based truncation and a variation on the Singular Value Decomposition (SVD), constituting an orthogonal decomposition of the modeled airloads. Since neural networks are universal function approximators, the model based on this allows for more flexible parametrizations, including actuations and model inversions. Both parametrization strategies are showcased for model identification and reduction purposes, highlighting their strengths and weaknesses.</p>
ArticlesAirloadsHomogeneitySpherical HarmonicsNeural NetworkSVDFinn MatrasDirk Peter ReinhardtKristoffer GryteMorten Dinhoff Pedersen
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-3011110.52846/stccj.2023.3.1.44The Over-Damped String Stability Condition for a Platooning System
https://stccj.ucv.ro/index.php/stccj/article/view/45
<p>The over-damped string stability criterion is a very strong stability condition that not only addresses the stability in a stricter sense but also adequately captures the safety performance of a platoon. However, the mathematical representation of this criterion is incomplete in the literature. Here, this representation is completely described. Moreover, this article presents the mathematical test method to evaluate this stability condition for linear or linearized systems from the transfer function. The classical sting stability condition does not address the transient undesired convergent dynamics of a platoon, such as over-shooting, under-shooting or damped oscillating dynamics. This paper demonstrates that the over-damped string stability characteristic significantly attenuates these undesired convergent dynamics in the upstream direction. Thus, the advantage of this condition over the classical criterion for linear system is clarified theoretically and by simulation. Later, the numerical method to analyze the over-damped string stability criterion for nonlinear systems is discussed. Additionally, numerical simulations of an over-damped string stable adaptive cruise control (ACC) vehicle model are compared with that of some experimental test results on platoons of commercially implemented ACC equipped vehicles.</p>
Articlesover-damped string stabilityclassical string stabilityplatooning controladaptive cruise controlParthib KhoundPeter WillAntoine TordeuxFrank Gronwald
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-30121910.52846/stccj.2023.3.1.45Transfer function approaches for SEEG brain electrode interface applied to tissue classification
https://stccj.ucv.ro/index.php/stccj/article/view/46
<pre style="-qt-block-indent: 0; text-indent: 0px; margin: 0px;">This paper is about transfer function approaches for brain-electrode interface modelling in the context of StereoElectroEncephaloGraphy, and their possible use in tissue classification (between grey and white matter). Monopolar and bipolar configurations are first reviewed, giving rise to possible nonparametric and parametric identification methods, as well as related possible classification results (for identical tissues and distinct tissues at measurement points, respectively). A method combining both approaches is then proposed, so as to end up with a classification at each measurement point in any case. The proposed methodology is implemented with clinical data collected from a set of epileptic patients, confirming its interest by providing more than 70% of accuracy in the obtained results.</pre>
ArticlesSEEGdynamical modellingsystem identificationclassificationclinical dataMariana Mulinari Pinheiro MachadoAlina VodaGildas BesançonGuillaume BecqPhilippe KahaneOlivier David
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-30202810.52846/stccj.2023.3.1.46Distributed Buck Converter Realization Based on a Transmission Line
https://stccj.ucv.ro/index.php/stccj/article/view/47
<p>The buck converter is a widely used switched converter to adapt a higher DC voltage to a lower DC voltage. In the conventional design, the converter has two reactive elements, an inductor and a capacitor. Replacing these dynamical elements by a transmission line results in a distributed buck converter. Modeling the transmission line by the telegrapher's equations yields a model with completely new properties. We investigate the behavior of this system and present a practical circuit realization.</p>
Articlesbuck convertertransmission linepartial differential equationsdistributed systemscircuit simulationKlaus RöbenackRichard Herrmann
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-30293510.52846/stccj.2023.3.1.47Analysis of Industrial Sensor Data Using Statistical and Regression Methods
https://stccj.ucv.ro/index.php/stccj/article/view/48
<p>Today's industrial landscape is primarily driven by rapid and effective data processing and evaluation. Consequently, industries should devote considerable attention and resources towards real-time examination of the large data sets acquired, enabling timely extraction of vital information for outlier detection, fake data identification, and predictive analysis to mitigate unforeseen expenses. This rigorous process of data analysis necessitates the employment of a diverse set of algorithms that align with the specific objectives, spanning a wide spectrum of potential solutions. In this manuscript, we demonstrate how Apache Spark's unified engine can be harnessed for conducting statistical analysis of time series data, thereby expediting industrial data analysis processes. Furthermore, we examine and implement both linear and random forest regression models within the context of the demonstrated use case.</p>
ArticlesIoTIIoTregression modelsalgorithmspredictionsoutlier detectionsApache SparkKatalin FerenczJózsef DomokosLevente Kovács
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-30364410.52846/stccj.2023.3.1.48Sewer Network Multi-objective Optimization using Genetic Algorithms
https://stccj.ucv.ro/index.php/stccj/article/view/49
<p>This paper focuses on the multi-objective optimization of a sewer network that serves a medium-sized Romanian city, with a population of 250,000 residents. The sewer network is modeled using BSMSewer software package. The obtained results are based on numerical simulations with the optimization algorithm considering two performance criteria: the volume of overflow and the quality of the overflowed wastewater. For optimization, two approaches that use a controlled elitist genetic algorithm were employed: a multi-objective optimization and a two-steps multi-objective optimization. Results analysis involved comparing them with a scenario where each performance criterion was separately minimized. Additionally, a comparison was made to the situation where the sewer network operated without a control system, meaning the valves were fully open and the pumps were running at maximum capacity.</p>
Articleswastewatersewer networkmulti-objective optimizationcontrolled elitist genetic algorithmIulian VasilievLaurențiu LucaMarian BarbuRamon VilanovaSergiu Caraman
Copyright (c) 2023 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2023-06-302023-06-30455010.52846/stccj.2023.3.1.49Harnessing performance counters to detect malware using deep learning models
https://stccj.ucv.ro/index.php/stccj/article/view/42
<p>Computing systems are challenged by security exploits and malware. The following methods are used for detecting anomalies and discovering vulnerabilities in computing systems: malware aware processors, static program analysis, and dynamic program analysis. Online hardware to detect malware is not always a practical and scalable solution because of the costs. Automated static analysis tools have limited performance and detection capabilities that may not meet the criticality requirements of the project regarding static analysis methods. In the latest trends, dynamic analysis has overcome static analysis. Several approaches have been used to analyze performance counters in this sense. Performance counters are collected from both operating systems/software and processors/hardware and stored as time series: 1) in the presence and 2) in the absence of malware. For software performance counters (SPCs), fourteen deep learning models were used for time series classification, while for hardware perfornamce counters (HPCs), ten deep learning models were used. For SPCs two models were able to detect accurately malware in infected operating systems, while the rest tend to overfit the data. For HPCs three models were able to detect malware.</p>
Articlesmalwaresoftware performance countershardware performance countersprogram behaviourtime series classificationdeep learning classification modelsrecurrent neural networksOmar MohamedCiprian-Bogdan Chirila
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-31404910.52846/stccj.2022.2.2.42Application of Heavy and Underestimated Dynamic Models in Adaptive Receding Horizon Control Without Constraints
https://stccj.ucv.ro/index.php/stccj/article/view/36
<p>In the heuristic “Adaptive Receding Horizon Controller” (ARHC) the available dynamic model of the controlled system usually is placed in the role of a constraint under which various cost functions can be minimized over a horizon. A possible secure design can be making calculations for a “heavy dynamic model” that may produce high dynamical burden that is efficiently penalized by the cost functions and instead of the original nominal trajectory results a “deformed” one that can be realized by the controlled system of “less heavy dynamics”. In the lack of accurate system model a fixed point iterationbased adaptive approach is suggested for the precise realization of this deformed trajectory. To reduce the computational burden of the control the usual approach in which the dynamic model is considered as constraint and Lagrange-multipliers are introduced as co-state variables is evaded. The heavy dynamic model is directly built in the cost and the computationally greedy Reduced Gradient Algorithm is replaced by a transition between the simple and fast Newton-Raphson and the slower Gradient Descent algorithms (GDA). In the paper simulation examples are presented for two dynamically coupled van der Pol oscillators as a strongly nonlinear system. The comparative use of simple nondifferentiable and differentiable cost functions is considered, too.</p>
ArticlesNewton-Raphson AlgorithmGradient Descent AlgorithmReduced Gradient AlgorithmReceding Horizon ControlFixed Point Iteration-based Adaptive ControlAwudu Atinga Jozsef Kazmer Tar
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-311810.52846/stccj.2022.2.2.36On Certain Noise Filtering Techniques in Fixed Point Iteration-based Adaptive Control
https://stccj.ucv.ro/index.php/stccj/article/view/38
<p>In control applications the use of noise-burdened sensor signals cannot be evaded. Also, certain signals can be lost. This problem traditionally is tackled by the use of Kalman filters that provide some “optimal solution” to these problems based on reasonable assumptions that are not always well underpinned in the practice. These are assumptions are made with regard to the system model and the statistical distribution of the noise signals. The Fixed Point Iteration-based adaptive controller is applicable for various strongly nonlinear models. Because feeding back the order of time-derivative of the system’s variable that immediately can be varied by the control signal, its noise sensitivity can be considerable. In this paper the operation of an unscented Kalman filter-based technique is compared with that of a simple moving window with affine signal approximation, and the use of a third order low pass filter in the control of a modified van der Pol oscillator. In this model a quadratic drag term is added to the original model to describe the motion of the system in turbulent fluid environment. According to the numerical simulations it can be stated that the simpler methods can replace the more complicated Kalman filter.</p>
Articlesunscented Kalman filterfixed point iteration- based adaptive controlnonlinear dynamic systemsnoise filteringHazem IssaMahmod Al-BkreeJozsef K. Tar
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-3191610.52846/stccj.2022.2.2.38Application Development with Finite Element Method to Calculate Photogeneration Rate and Open-Circuit Voltage of Dye Sensitized Solar Cell
https://stccj.ucv.ro/index.php/stccj/article/view/39
<p>Amongst the several alternative resources, renewable energy source (RES) can provide continuous and clean energy. Furthermore, RESs have received a worldwide attention and an outstanding role is attributed to them. The sun energy can be exploited using light energy conversion applications such as photovoltaics. Dye Sensitized Solar Cell (DSSC) is third-generation photovoltaic device and a forwardlooking, easily producible solar cell. Nevertheless, buying a commercially available DSSC, datasheet and material information are unavailable. Thus, the purchased DSSC is a black box. The main motivation is that to develop a MatLab application which is able to determine the material information and parameters of the Dye Sensitized Solar Cell from some incoming parameters. The goal of the study is to describe the peration of the developed MatLab application which calculated the photogeneration rate in function of the thickness of the cell, the open-circuit voltage, and to illustrate its operation via an example. The photogeneration rate is solved using the numerical finite element method as a numerical procedure. In our model the Beer-Lambert law is implemented. The model takes into consideration the measured parameters of the light such as photoncount-wavelength spectrum, transmissionwavelength spectrum and irradiation intensity-wavelength spectrum. Furthermore, the open-circuit voltage is an elementary electric parameter of a solar cell.</p>
ArticlesDye Sensitized Solar CellDSSCPhotogeneration rateOpen-Circuit VoltageModellingNumerical SolutionZoltan VargaErvin Racz
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-31172410.52846/stccj.2022.2.2.39Approach to the Design of a Microservice Architecture Based on Praxeme
https://stccj.ucv.ro/index.php/stccj/article/view/40
<p>Frequent updates of business needs are one of the factors of the evolution of a company. These permanent changes require a large flexibility of the Information System (IS). SOA (Service Oriented Architecture) is an architecture that offers more scalability to an application by subdividing the monolithic block into independent services. Nevertheless, it is not sufficiently suitable in terms of accessibility of services and data. It is thus necessary to orient the design of the IS towards a new architecture called Microservice Architecture (MSA). The objective of this paper is to recommend a methodology to design MSA. Indeed, our approach is based on Praxeme which is an enterprise methodology appropriate to SOA. The result obtained from the approach proposed in this paper is a model allowing to automate the MSA design.</p>
ArticlesSOAMSAMDAUMLMonolithic Architecturesoftware architecture design methodologyPraxemeReLELMihajasoa Léa FanomezanaAndrianjaka Miary RapatsalahyNicolas Raft RazafindrakotoCostin Bădică
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-31253110.52846/stccj.2022.2.2.40Limiting State Estimation of Switched Interval Systems with Metzler-Takagi-Sugeno Models
https://stccj.ucv.ro/index.php/stccj/article/view/41
<p>The paper deals with interval observer design for fuzzy switched positive systems. The systems are represented by the Takagi-Sugeno fuzzy models, with premise variables depending on a measurable part of the state vector. Stability conditions for the proposed interval observer structure are formulated via linear matrix inequalities to ensure nonnegative system state estimation. The proposed method allows to compute the lower and upper bounds of the system state under the assumption that the system disturbance are bounded. The properties of proposed approach are illustrated in numerical example.</p>
ArticlesTakagi-Sugeno models, switched systems, Metzler systems, parametric constraints, interval observer design.Dusan KrokavecAnna Filasova
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-12-312022-12-31323910.52846/stccj.2022.2.2.41Sparse Filtering Under Norm-Bounded Exogenous Disturbances Using Observers
https://stccj.ucv.ro/index.php/stccj/article/view/29
<p>The paper considers the sparse filtering problem under arbitrary norm-bounded exogenous disturbances. We propose a simple and universal observer-based approach to its solution, based on the LMI technique and the method of invariant ellipsoids; it allows the use of a reduced number of system outputs. From a technical point of view of application, we reduce the original problem to semi-definite programming, which is easily solved numerically. The proposed simple approach is easy to implement and can be equally extended to systems in continuous and discrete time.</p>
Articleslinear systemfilteringsparsityexogenous disturbanceslinear matrix inequalitiesinvariant ellipsoidsMikhail Khlebnikov
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-06-302022-06-301710.52846/stccj.2022.2.1.29Global Position Feedback Tracking Control of a Serial Robot Manipulator with Revolute Joints
https://stccj.ucv.ro/index.php/stccj/article/view/30
<p>In this paper, we present the controller which globally stabilizes a non-stationary motion of a serial robot manipulator with revolute joints without velocity measurements.<br>A family of desired manipulator motions is considered such that the first vertical link of the manipulator performs a given rotation, and the remaining links retain the given relative angular positions. It is proved that such motions of the manipulator can be made globally asymptotically stable using dynamic position feedback. The problem is solved taking into account the periodicity of the dynamics equations along the angular coordinates of the links. As an example, a numerical simulation of the three-link manipulator motion under the constructed controller is presented.</p>
Articlesstabilization control problemserial robot manipulatorrevolute jointdynamic position feedbackLyapunov functionAzizbeck AkhmatovJamshid BuranovJumanazar KhusanovOlga Peregudova
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-06-302022-06-3081210.52846/stccj.2022.2.1.30Full and Partial Eigenvalue Placement for Minimum Norm Static Output Feedback Control
https://stccj.ucv.ro/index.php/stccj/article/view/32
<p>The controller design for linear time-invariant state space systems seems to be straightforward and well established. This is not true for static output feedback control, which is still a challenging task. This paper deals with controller design based on eigenvalue assignment. We consider the placement of distinct as well as multiple real eigenvalues or complex conjugate pairs. The desired eigenvalue configurations are characterised in terms of algebraic divisibility of the characteristic polynomial of the closed-loop system. We also consider the problem of partial eigenvalue placement, where not all eigenvalues are fixed by feedback. Degrees of freedom in the controller design are used for the minimization of various matrix norms of the feedback gain matrix.</p>
ArticlesLinear time-invarianteigenvalue placementstatic output feedbackpolynomial idealsGröbner basesquantifier eliminationnorm minimizationKlaus RöbenackDaniel Gerbet
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-06-302022-06-30223310.52846/stccj.2022.2.1.32On functional differential equations connected to Huygens synchronization under propagation
https://stccj.ucv.ro/index.php/stccj/article/view/33
<p>The structure represented by one or several oscillators couple to a one-dimensional transmission environment (e.g. a vibrating string in the mechanical case or a lossless transmission line in the electrical case) turned to be attractive for the research in the field of complex structures and/or complex behavior. This is due to the fact that such a structure represents some generalization of various interconnection modes with lumped parameters for the oscillators.<br />On the other hand the lossless and distortionless propagation along transmission lines has generated several research in electrical, thermal, hydro and control engineering leading to the association of some functional differential equations to the basic initial boundary value problems.<br />The present research is performed at the crossroad of the aforementioned directions. We shall associate to the starting models some functional differential equations - in most cases of neutral type - and make use of the general theorems for existence and stability of forced oscillations for functional differential equations. The challenges introduced by the analyzed problems for the general theory are emphasized, together with the implication of the results for various applications.</p>
Articlesconservation lawsdistortionless propagationtime delaysVladimir Rasvan
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-06-302022-06-30344310.52846/stccj.2022.2.1.33Flat input based canonical form observers for non-integrable nonlinear systems
https://stccj.ucv.ro/index.php/stccj/article/view/31
<p>In this contribution, the design of canonical form observers for nonlinear non-integrable systems is investigated. These systems cannot be transformed into observer canonical form, therefore an exact observer error linearization cannot be achieved. However, using flat inputs and dynamic compensators, the original dynamics can be rendered into an integrable flat system. For this modified flat input system a canonical form observer can be designed. By utilizing a state transformation, it is then possible to obtain an estimate of the original state, where the observer error is approximately linearized. This procedure is exemplified by the Rössler system. Furthermore, we illustrate the relationship of this approach with high-gain observers.</p>
Articlesnonlinear systemsobserver designobserver error linearizationdifferential flatnessflat inputsKlemens FritzscheKlaus RöbenackYuhang Guo
Copyright (c) 2022 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2022-06-302022-06-30132110.52846/stccj.2022.2.1.31Conservation Laws -- a Source for Distortionless Propagation and Time Delays
https://stccj.ucv.ro/index.php/stccj/article/view/12
<p>Since the very first paper of J. Bernoulli in 1728, a connection exists between initial boundary value problems for hyperbolic Partial Differential Equations (PDE) in the plane (with a single space coordinate accounting for wave propagation) and some associated Functional Equations (FE). From the point of view of dynamics and control (to be specific, of dynamics <em>for </em><em>control</em>) both type of equations generate dynamical and controlled dynamical systems. The functional equations may be difference equations (in continuous time), delay-differential (mostly of neutral type) or even integral/integro-differential. It is possible to discuss dynamics and control either for PDE or FE since both may be viewed as self contained mathematical objects.</p> <p>A more recent topic is control of systems displaying conservation laws. Conservation laws are described by <em>nonlinear </em>hyperbolic PDE belonging to the class ``lossless'' (conservative); their dynamics and control theory is well served by the associated energy integral. It is however not without interest to discuss association of some FE. Lossless implies usually distortionless propagation hence one would expect here also lumped time delays.</p> <p>The paper contains some illustrating applications from various fields: nuclear reactors with circulating fuel, canal flows control, overhead crane, drilling devices, without forgetting the standard classical example of the nonhomogeneous transmission lines for distortionless and lossless propagation. Specific features of the control models are discussed in connection with the control approach wherever it applies.</p>
Articlesconservation laws, distortionless propagation, time delaysVladimir Rasvan
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-3111110.52846/stccj.2021.1.2.12Systems Actuated by Shape Memory Alloys: Identification and Modeling
https://stccj.ucv.ro/index.php/stccj/article/view/20
<p>This paper presents the identification of thermal and mechanical parameters of shape memory alloys by using the heat transfer equation and a constitutive model. The identified parameters are then used to describe the mathematical model of a fiber-elastomer composite embedded with shape memory alloys. To verify the validity of the obtained equations, numerical simulations of the SMA temperature and composite bending are carried out and compared with the experimental results.</p>
Articlesidentificationmodelingshape memory alloysNajmeh KeshtkarJohannes MerschKonrad KatzerFelix LohseLars NatkowskiGerald GerlachMartina ZimmermannChokri CherifKlaus Röbenack
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31122010.52846/stccj.2021.1.2.20Accelerated Reduced Gradient Algorithm with Constraint Relaxation in Differential Inverse Kinematics
https://stccj.ucv.ro/index.php/stccj/article/view/23
<p><span dir="ltr" role="presentation">The Moore-Penrose pseudoinverse-based solution of </span><span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">differential</span> <span dir="ltr" role="presentation">inverse</span> <span dir="ltr" role="presentation">kinematic</span> <span dir="ltr" role="presentation">task</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">redundant</span> <span dir="ltr" role="presentation">robots </span><span dir="ltr" role="presentation">corresponds</span> <span dir="ltr" role="presentation">to</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">result</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">a</span> <span dir="ltr" role="presentation">particular</span> <span dir="ltr" role="presentation">optimization</span> <span dir="ltr" role="presentation">under</span><span dir="ltr" role="presentation">constraints</span> <span dir="ltr" role="presentation">in</span> <span dir="ltr" role="presentation">which</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">implementation</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">Lagrange’s</span> <span dir="ltr" role="presentation">Reduced</span><span dir="ltr" role="presentation">Gradient</span> <span dir="ltr" role="presentation">Algorithm</span> <span dir="ltr" role="presentation">can</span> <span dir="ltr" role="presentation">be</span> <span dir="ltr" role="presentation">evaded</span> <span dir="ltr" role="presentation">simply</span> <span dir="ltr" role="presentation">by</span> <span dir="ltr" role="presentation">considering</span> <span dir="ltr" role="presentation">the z</span><span dir="ltr" role="presentation">ero</span> <span dir="ltr" role="presentation">partial</span> <span dir="ltr" role="presentation">derivatives</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">”Auxiliary</span> <span dir="ltr" role="presentation">Function”</span> <span dir="ltr" role="presentation">associated </span><span dir="ltr" role="presentation">with this problem. This possibility arises because of the fact that </span><span dir="ltr" role="presentation">the cost term is built up of quadratic functions of the variable of </span><span dir="ltr" role="presentation">optimization</span> <span dir="ltr" role="presentation">while</span> <span dir="ltr" role="presentation">the </span><span dir="ltr" role="presentation">constraint</span> <span dir="ltr" role="presentation">term</span> <span dir="ltr" role="presentation">is</span> <span dir="ltr" role="presentation">linear</span> <span dir="ltr" role="presentation">function</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">the </span><span dir="ltr" role="presentation">same</span> <span dir="ltr" role="presentation">variables.</span> <span dir="ltr" role="presentation">Any</span> <span dir="ltr" role="presentation">modification</span> <span dir="ltr" role="presentation">in</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">cost</span> <span dir="ltr" role="presentation">and/or</span> <span dir="ltr" role="presentation">constraint </span><span dir="ltr" role="presentation">structure</span> <span dir="ltr" role="presentation">makes</span> <span dir="ltr" role="presentation">it</span> <span dir="ltr" role="presentation">necessary</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">use</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">numerical</span> <span dir="ltr" role="presentation">algorithm. </span><span dir="ltr" role="presentation">Anyway, the penalty effect of the cost terms is always overridden </span><span dir="ltr" role="presentation">by</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">hard </span><span dir="ltr" role="presentation">constraints</span> <span dir="ltr" role="presentation">that</span> <span dir="ltr" role="presentation">makes</span> <span dir="ltr" role="presentation">practical</span> <span dir="ltr" role="presentation">problems</span> <span dir="ltr" role="presentation">in</span> <span dir="ltr" role="presentation">the </span><span dir="ltr" role="presentation">vicinity of kinematic singularities where the possible solution still</span><br role="presentation"><span dir="ltr" role="presentation">exists</span> <span dir="ltr" role="presentation">but</span> <span dir="ltr" role="presentation">needs</span> <span dir="ltr" role="presentation">huge</span> <span dir="ltr" role="presentation">joint</span> <span dir="ltr" role="presentation">coordinate</span> <span dir="ltr" role="presentation">time-derivatives.</span> <span dir="ltr" role="presentation">While</span> <span dir="ltr" role="presentation">in </span><span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">special</span> <span dir="ltr" role="presentation">case</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">pseudoinverse</span> <span dir="ltr" role="presentation">simply</span> <span dir="ltr" role="presentation">can</span> <span dir="ltr" role="presentation">be</span> <span dir="ltr" role="presentation">deformed,</span> <span dir="ltr" role="presentation">in</span><br role="presentation"><span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">more</span> <span dir="ltr" role="presentation">general</span> <span dir="ltr" role="presentation">one</span> <span dir="ltr" role="presentation">more</span> <span dir="ltr" role="presentation">sophisticated</span> <span dir="ltr" role="presentation">constraint</span> <span dir="ltr" role="presentation">relaxation </span><span dir="ltr" role="presentation">can</span> <span dir="ltr" role="presentation">be</span> <span dir="ltr" role="presentation">applied.</span> <span dir="ltr" role="presentation">In</span> <span dir="ltr" role="presentation">this</span> <span dir="ltr" role="presentation">paper</span> <span dir="ltr" role="presentation">a</span> <span dir="ltr" role="presentation">formerly</span> <span dir="ltr" role="presentation">proposed</span> <span dir="ltr" role="presentation">accelerated</span><br role="presentation"><span dir="ltr" role="presentation">treatment</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">the</span> <span dir="ltr" role="presentation">constraint</span> <span dir="ltr" role="presentation">terms</span> <span dir="ltr" role="presentation">is</span> <span dir="ltr" role="presentation">further</span> <span dir="ltr" role="presentation">developed</span> <span dir="ltr" role="presentation">by</span> <span dir="ltr" role="presentation">the </span><span dir="ltr" role="presentation">introduction</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">a</span> <span dir="ltr" role="presentation">simple</span> <span dir="ltr" role="presentation">constraint</span> <span dir="ltr" role="presentation">relaxation.</span> <span dir="ltr" role="presentation">Furthermore,</span> <span dir="ltr" role="presentation">the</span><br role="presentation"><span dir="ltr" role="presentation">numerical results of the algorithm are smoothed by a third order </span><span dir="ltr" role="presentation">tracking</span> <span dir="ltr" role="presentation">strategy</span> <span dir="ltr" role="presentation">to</span> <span dir="ltr" role="presentation">obtain</span> <span dir="ltr" role="presentation">dynamically</span> <span dir="ltr" role="presentation">implementable</span> <span dir="ltr" role="presentation">solution.</span><br role="presentation"><span dir="ltr" role="presentation">The improved method’s operation is exemplified by computation </span><span dir="ltr" role="presentation">results</span> <span dir="ltr" role="presentation">for</span> <span dir="ltr" role="presentation">a</span> <span dir="ltr" role="presentation">7</span> <span dir="ltr" role="presentation">degree</span> <span dir="ltr" role="presentation">of</span> <span dir="ltr" role="presentation">freedom</span> <span dir="ltr" role="presentation">open</span> <span dir="ltr" role="presentation">kinematic</span> <span dir="ltr" role="presentation">chain</span></p>
Articlesdifferential inverse kinematic taskreduced gradient algorithmMoore-Penrose pseudoinverseredundant open kinematic chainconstraint relaxationBence VargaHazem IssaRichárd HorváthJózsef Tar
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31213210.52846/stccj.2021.1.2.23Controlling Agents by Constrained Policy Updates
https://stccj.ucv.ro/index.php/stccj/article/view/24
<p>Learning the optimal behavior is the ultimate goal in reinforcement learning. This can be achieved by many different approaches, the most successful of them are policy gradient methods. However, they can suffer from undesirably large updates of policies, leading to poor performance. In recent years there has been a clear trend toward designing more reliable algorithms. This paper addresses to examine different restriction strategies applied to the widely used Proximal Policy Optimization (PPO-Clip) technique. We also question whether the analyzed methods are able to adapt not only to low-dimensional tasks but also to complex, high-dimensional problems in control and robotic domains. The analysis of the learned behavior shows that these methods can lead to better performance compared to the original PPO-Clip algorithm, moreover, they are also able to achieve complex behavior and policies in high-dimensional environments.</p>
ArticlesControlConstrained policyProximal Policy OptimizationReinforcement learningMónika FarsangLuca Szegletes
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31333910.52846/stccj.2021.1.2.24Sub-optimal Solution of the Inverse Kinematic Task of Redundant Robots without Using Lagrange Multipliers
https://stccj.ucv.ro/index.php/stccj/article/view/25
<p>In the paper a novel approach is suggested for solving the inverse kinematic task of redundant open kinematic chains. Traditional approaches as the Moore-Penrose generalized inverse-based solutions minimize the sum of squares of the timederivative of the joint coordinates under the constraint that contains the task itself. In the vicinity of kinematic singularities where these solutions are possible the hard constraint terms produce high time-derivatives that can be reduced by the use of a deformation proposed by Levenberg and Marquardt. The novel approach uses the basic scheme of the Receding Horizon Controllers in which the Lagrange multipliers are eliminated by direct application of the kinematic model over the horizon in the role of the ”control force”, and no reduced gradient has to be computed. This fact considerably decreases the complexity of the solution. If the cost function contains penalty for high joint coordinate time-derivatives the kinematic singularities are ab ovo better handled. Simulation examples made for a 7 degree of freedom robot arm demonstrate the operation of the novel approach. The computational need of the method is still considerable but it can be further decreased by the application of complementary tricks.</p>
Articlesinverse kinematic taskgradient descent methodreduced gradient algorithmMoore-Penrose pseudoinversereceding horizon controlBence VargaHazem IssaRichárd HorváthJózsef Tar
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31404810.52846/stccj.2021.1.2.25Voice User Interface: Literature review, challenges and future directions
https://stccj.ucv.ro/index.php/stccj/article/view/26
<p>Natural user interfaces are increasingly popular these days. One of the most common of these user interfaces today are voice-activated interfaces, in particular intelligent voice assistants such as Google Assistant, Alexa, Cortana and Siri.</p> <p>However, the results show that although there are many services available, there is still a lot to be done to improve the usability of these systems. Speech recognition, contextual understanding and human interaction are the issues that are not yet solved in this field.</p> <p>In this context, this research paper focuses on the state of the art and knowledge of work on intelligent voice interfaces, challenges and issues related to this field, in particular on interaction quality, usability, security and usability. As such, the study also examines voice assistant architecture components following the expansion of the use of technologies such as wearable computing in order to improve the user experience. Moreover, the presentation of new emerging technologies in this field will be the subject of a section in this work.</p> <p>The main contributions of this paper are therefore: (1) overview of existing research, (2) analysis and exploration of the field of intelligent voice assistant systems, with details at the component level, (3) identification of areas that require further research and development, with the aim of increasing its use, (4) various proposals for research directions and orientations for future work, and finally, (5) study of the feasibility of designing a new type of voice assistant and general presentation of the latter, whose realisation will be the subject of a thesis.</p>
ArticlesArtificial intelligenceHuman Machine InteractionLiterature reviewMachine learningNatural language processingVoice assistantFrancis RakotomalalaHasindraibe Niriarijaona RandriatsarafaraAimé Richard HajalalainaNdaohialy Manda Vy Ravonimanantsoa
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31658910.52846/stccj.2021.1.2.26A vehicular traffic congestion predictor system using Mamdani fuzzy inference
https://stccj.ucv.ro/index.php/stccj/article/view/27
<p>The process of traffic control systems significantly relies on the immediate detection of breakdown states. As a result of their crisp (non-fuzzy) based calculation procedures, conventional traffic estimators and predictors cannot effectively model traffic states. In fact, these methods are characterized by exact features, while traffic is defined by uncertain variables with vague properties. Furthermore, typical numerical methodologies have constraints on evaluating the overall system status in heterogeneous and convoluted networks mainly due to the absence of reliable and real-time data. This study develops a fuzzy inference system that uses data from the Hungarian freeway networks for predicting the severity of congestion in this complex network. Congestion severity is considered the output variable, and traffic flow along with the length and the number of lanes of each section are assigned as input variables. Seventy-five fuzzy production rules were generated using accessible datasets, percentile distribution, and experts' consensus. The MATLAB fuzzy logic toolbox simulates the designed model and analysis steps. According to available resources, the results demonstrate linkages among input variables. Analyses are also used to construct intelligent traffic modeling systems and further service-related planning.</p>
ArticlesFuzzy inferenceintelligent transportationcongestion predictionMehran AminiMiklos F. HatwagnerGergely Cs. MikulaiLaszlo T. Koczy
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31495710.52846/stccj.2021.1.2.27Modeling of probable maximum values in autonomous driving
https://stccj.ucv.ro/index.php/stccj/article/view/28
<p>In this paper, we approximate the probable maximum (very rare, extremal) values of highly autonomous driving sensor signals by reviewing two methods based on dynamic time series scaling and multifractal statistics.The article is a significantly revised and modified version of the conference material ("Determination of extreme values in autonomous driving based on multifractals and dynamic scaling") presented at the conference "2021 IEEE 15th International Symposium on Applied Computational Intelligence and Informatics, SACI".</p> <p>The method of dynamic scaling is originally derived from statistical physics and approximates the critical interface phenomena. The time series of the vibration signal of the corner radar can be considered as a fractal surface and grow appropriately for a given scale-inverse dynamic equation. In the second method we initiate, that multifractal statistics can be useful in searching for statistical analog time series that have a similar multifractal spectrum as the original sensor time series.</p>
ArticlesHighly autonomous drivingextreme valueprobable maximum valuetestingsynamic scalingmultifractal analysisPeter BakuczGabor Kiss
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-12-312021-12-31586410.52846/stccj.2021.1.2.28Baseline removal in spectrometry gamma by observation of local minima
https://stccj.ucv.ro/index.php/stccj/article/view/4
<p>This paper presents a Baseline Removal method in the context of spectrometry gamma. The method implements an estimator for the full continuum based on the observation of local minima. This estimator is constructed from the statistical properties of the signal and is therefore easily explainable. The method involves a limited number of fixed parameters, which allows the automation of the process. Moreover, the method is adaptable to any peaks width, which makes it suitable for both HPGe spectrometers and scintillators. Application to real gamma spectrometry measurements are presented, as well as a discussion about the choice of the parameters, for which an adjustment is proposed.</p>
Articlesbackground removalbaseline correctiongamma spectrometrycontinuum estimationpeak characterizationlocal minimaKélian ThisLaurent Le BrusquetAdrien FrigerioSébastien ColasPascal Bondon
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-06-302021-06-3011210.52846/stccj.2021.1.1.4On the Backward Path Tracking Control of N-Trailer Systems
https://stccj.ucv.ro/index.php/stccj/article/view/6
<p>This paper considers the lateral control of articulated wheeled vehicles in backward motion. The parameterized articulated vehicle is composed of a car-like truck and N passive trailers, resulting in one single steerable axle. First a nonlinear path tracking control law based on exact linearization of an offset model is reviewed and the general stability conditions of such systems is presented. Second, a stability analysis for some vehicle cases is performed and verified in simulation. The possible application of this path tracking control law in real world articulated vehicles is discussed, and its limitations are shown.</p>
Articlestruck-trailerarticulated vehiclebackward motionpath trackingnonlinear controlexact linearizationstabilizationJulius KolbGunter NitzscheSebastian WagnerKlaus Röbenack
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-06-302021-06-30132010.52846/stccj.2021.1.1.6Application Study of Newton-Raphson-Type Nonlinear MPC for Hydrostatic Transmissions Under Disturbance and System Uncertainty
https://stccj.ucv.ro/index.php/stccj/article/view/7
<p>Model predictive control is well established and has a huge practical relevance in many industrial applications, especially for chemical or thermal plants. This paper presents the design and the implementation of a nonlinear model predictive control aiming at an accurate tracking control of desired output trajectories under disturbances and uncertainties for a nonlinear hydrostatic transmission system with multiple control inputs, which represents a fast mechatronic system. The benefit of this solution is that it can be easily adapted to either velocity tracking control or torque tracking control -- which is not the case with alternative model-based approaches. The control design is based on a numerical optimization within a moving horizon using the Newton-Raphson method in combination with the optimization-over-some variables technique. The unmeasurable system state variables as well as the system disturbances are reconstructed by an unscented Kalman filter which is well suited for nonlineaer systems subject to process and measurement noise. The proposed control scheme is investigated by simulations and experimentally validated on a test rig at the Chair of Mechatronics, University of Rostock. The results indicates the robustness of the proposed control structure by a high tracking accuracy despite system disturbances and uncertainties.</p>
ArticlesMultivariable SystemsHydrostatic TransmissionModel Predictive ControlReal-Time ImplementationNgoc Danh DangHarald Aschemann
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-06-302021-06-30212910.52846/stccj.2021.1.1.7On σ-entropy Analysis of Linear Stochastic Systems in State Space
https://stccj.ucv.ro/index.php/stccj/article/view/8
<p>In this paper the problem of random disturbance attenuation capabilities in linear continuous systems is studied. It is supposed that the system operates under random disturbances with bounded σ-entropy level. σ-entropy norm indicates a performance index of the continuous system on the set of the random signals with bounded σ-entropy. This paper presents a time-domain solution to the calculation of σ-entropy norm of the continuous linear time-invariant system. σ-entropy norm is defined after solving coupled matrix equations: one algebraic Riccati equation, one nonlinear equation over log determinant function, and two Lyapunov equations.</p>
Articlesstochastic systemslinear systemssystem sensitivityentropy functionVictor BoichenkoAlexey Belov
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-06-302021-06-30303510.52846/stccj.2021.1.1.8Automatic Generation of Object-Oriented Code from the ReLEL Requirements Model
https://stccj.ucv.ro/index.php/stccj/article/view/9
<p>The final executable code should no longer be considered as a central element in a software development process but rather a naturally important component that results from a model transformation. The objective of the MDA (Model Driven Architecture) approach is to lift the lock of software development automation from the CIM (Computation Independent Model) requirements until the code of an application is obtained. Therefore, we have proposed in the framework of MDA an approach that consists of <br>automatically generating object-oriented code from the CIM model represented by ReLEL (Restructuring extended Lexical Elaborate Language). ReLEL is a natural language-oriented model that represents both the client requirements and the conceptual level of a system. However, the MDA framework does not recommend the type of UML model that corresponds to each business activity. Consequently, automating the software development process from the CIM model specified by ReLEL becomes a complex task. Our strategy in this paper includes the instantiation of the ReLEL model in the Praxeme methodology, which models each of the company's concerns, grouped in a homogeneous whole, using the UML (Unified Modeling Language) and which considers the articulation of these aspects by adopting the MDA principle. To do this, we propose to automate the articulation that covers the intentional, semantic, logical, and software aspects of Praxeme. To validate our approach, we measure the coupling and cohesion of the UML class diagram obtained from the Java code generated from this article using the slicing technique. The results show that the coupling is weak, and the cohesion is strong. It can be deduced that the method proposed in this paper can produce a more reliable and efficient system. </p>
ArticlesUMLCode generationmodel driven architectureAndrianjaka Miary RapatsalahyHajarisena RazafimahatratraThomas MahatodyMihaela IlieSorin IlieRaft Nicolas Razafindrakoto
Copyright (c) 2021 SYSTEM THEORY, CONTROL AND COMPUTING JOURNAL
2021-06-302021-06-30364710.52846/stccj.2021.1.1.9