INTERNATIONAL JOURNAL OF COMPUTERS COMMUNICATIONS & CONTROL Online ISSN 1841-9844, ISSN-L 1841-9836, Volume: 15, Issue: 5, Month: october, Year: 2020 Article Number: 3898, https://doi.org/10.15837/ijccc.2020.5.3898 CCC Publications Lyapunov-based Methods for Maximizing the Domain of Attraction H. Jerbi, F. Hamidi, S. Ben Aoun, S. C. Olteanu, D. Popescu Houssem Jerbi* University of Ha’il, College of Engineering Department of Industrial Engineering Hail 1234, KSA *Corresponding author: h.jerbi@uoh.edu.sa Faiçal Hamidi Laboratoire de Recherche Modélisation, Analyse et Commande des Systèmes University of Gabes, ENIG, 6029 Gabes, Tunisie faical.hmidi@isimg.tn Sondess Ben Aoun University of Ha’il, College of Computer Science and Engineering Department of Computer Engineering Hail 1234, KSA s.benaoun@uoh.edu.sa Severus Constantin Olteanu, Dumitru Popescu University ‘Politehnica’ of Bucharest Faculty of Automatic Control and Computer Science Bucharest Romania severus.olteanu@acse.pub.ro, popescu_upb@yahoo.com Abstract This paper investigates Lyapunov approaches to expand the domain of attraction (DA) of nonlinear autonomous models. These techniques had been examined for creating generic numerical procedures centred on the search of rational and quadratic Lyapunov functions. The outcomes are derived from all investigated methods: the method of estimation via Threshold Accepted Algorithm (TAA), the method of estimation via a Zubov technique and the method of estimation via a linear matrix inequality (LMI) optimization and genetic algorithms (GA). These methods are effective for a large group of nonlinear models, they have a significant ability of improvement of the attraction domain area and they are distinguished by an apparent propriety of direct application for compact and nonlinear models of high degree. The validity and the effectiveness of the examined techniques are established based on a simulation case analysis. The effectiveness of the presented methods is evaluated and discussed through the study of the renowned Van der Pol model. Keywords: Lyapunov function, nonlinear model, asymptotic stability, equilibrium point, ge- netic algorithm, threshold accepted algorithm, LMI. https://doi.org/10.15837/ijccc.2020.5.3898 2 1 Introduction During the previous decades, the complexity of approximating the attraction domain area has remained the focus of several benchmarking works [25, 30, 35, 36, 41], the references contained in them. The asymptotic stability area of physical systems is a significant property to be identified [18]. From a practical point of view, it is every so often insufficient to demonstrate the local asymptotic stability for point of equilibrium [4, 20, 21, 34, 42], however one may also require discerning the size of the stability region, as well [27, 33]. As a matter of fact, the stability area or attraction domain is described as the set of original starting criteria where the system states meet at the points of equi- librium [7, 8, 9]. Thus, it is vital to specify the state of this area. To achieve this, one can utilize a Lyapunov function [11, 13, 20, 25, 27, 32]. In fact, for a specified energy function providing stable local equilibrium, the biggest probable DA, the state of which is established by the Lyapunov energy function theory, is referred to be as the prevalent smooth function set integrated in a bounded domain where its derivative is negative [12, 22, 27, 40]. A significant number of approaches on estimating the area of attraction investigated in the liter- ature are established exploiting the established statements of LaSalle and Lefschetz [26, 29, 31, 32]. These later are based upon appropriately selected Lyapunov functions in [23, 24, 27]. Considered as one of the original outcomes as regard as the problematic of attraction domains estimation, the Zubov’s method has designed a Lyapunov function restricted by an open ball over a closed interval and consequently has sorted out an approximated DA [16, 43]. Similar complexity is detected when applying the algorithm synthesized by Knobloch and Kappel [8]. An LMI method to design polynomial Lyapunov functions for non-polynomial class of systems is provided in [10]. However, the problem of defining a truncation order for the Lyapunov function in the Taylor series expansion is not well addressed. In [11, 15] authors designate an LMI based technique for approximating the so-titled robust DA for a polynomial class of systems with model polytope uncertainties. In [9], authors formulate a fundamental analytical background in which particular classes of min- imum based distance problems are resolved via LMI calculations [14]. The previous specified ap- proaches, nevertheless, are appropriate for the class of smooth non-linear ODE systems. In general, there is no generic techniques for determining Lyapunov functions as a group of non- linear models [6, 8] are established. Nonetheless, Lyapunov theory is still considered as the most efficient method to analyze the nonlinear models stability, although the Lyapunov theorem does not need the class of algebraic functions that must be retained [1, 2, 3, 37]. In [11, 13] the maximum uncertain domain to preserve the stability and nominal performances (robustness) of the nonlinear optimal control systems, is estimated. The goal of this paper is to recommend analytical methods motivating systematic approximating approaches of the DA. With the aim of getting a definite expression of the estimated DA, an investi- gation of the Lyapunov theory exploiting parameterized Lyapunov function is conducted as described in [6]. As the DA is related with a specified function of Lyapunov, the proposal entails selecting the optimal parameters to attain the most significant DA area. These later are designed as results to an optimization problem [5]. Output response designs with quantifiable premise parameters have also been employed in [22]. The paper structure is as follows. Section 2 provides a representation of the Carleman Linearization and the methodology of obtaining the Lyapunov functions based upon Lyapunov stability techniques and TAA. In Section 3, a recursive technique to calculate the DA through rational Lyapunov function is discussed. The fundamental principles of the GA are evaluated in the last part of this section. The assessment of the global accomplishment for the different techniques is performed by means of a simulation study carried out on the Van der Pol model. Section 4 focuses on the conclusions and https://doi.org/10.15837/ijccc.2020.5.3898 3 future works. 2 Searching Lyapunov Function via Threshold Accepting Algorithms 2.1 The Carleman Linearization The development of f (x) into a Taylor series expansion provides [17, 19]: f (x) = ∑ l Alx[l] (1) wherein: Al = { 1 l! ∂lf (0) ∂xi1 . . .∂xil } (2) and: x[l] = x⊗x⊗x.. .⊗x︸ ︷︷ ︸ l−T imes (3) denotes the l power Kronocker product of vector x Performing algebraic operations one can rewrite the vector derivative ẋ[l] as follows: ẋ([l]) = ∑l j=1 x⊗ ..⊗ .. ẋ︸︷︷︸ j ⊗..⊗x (4) This means ẋ([l]) = ∑l j=1 x⊗ ..⊗ ..f(x) ⊗ ..⊗x (5) By substituting f (x) with (1), one obtains: ẋ[l] = ∑l j=1 x⊗ ..⊗ .. ∑ k Akx[k] ⊗ ..⊗x (6) Thus, it becomes ẋ[k] = ∑ l Alkx [k+l−1] (7) where Alk = A l 1 ⊗ I [k−1] + I ⊗Alk−1 (8) Let the change of variables given below be considered now: Ψ = ( x,x[2],x[3], . . . ,x[k], . . . )T (9) an infinite dimension linear system given as: Ψ̇ = H Ψ (10) is attained with: H =   H11 . . . H i 1 . . . . . . 0 H12 H22 . . . . . . 0 0 H13 H23 . . . ... ... ... ... ...   (11) https://doi.org/10.15837/ijccc.2020.5.3898 4 2.2 A Lyapunov theory case investigation In this paragraph, an overall Lyapunov hypothesis for stabilizing a linear infinite dimension dy- namical model is given. Consider the nonlinear system (1) where it is assumed that the origin is an equilibrium state (i.e.f(0) = 0). It is shown that system (1) can be expressed under a linear operator form with an infinite dimension as shown in (11) where the changed state vector is given by (10). Consider the nonlinear function given by [28]: V = 〈( x,x[2],x[3], ... ) , Υ ( x,x[2],x[3], ... )〉 (12) then V̇ = 〈( HT Υ + ΥH )( x,x[2], .. ) ( x,x[2], .. )〉 = − ∥∥∥(x,x[2],x[3], ...)∥∥∥2 = − ( e ‖x‖ 2 − 1 ) (13) whereΥ is a symmetric positive definite operator and ‖.‖ denotes the norm on the subset = ={( x,x[2], .... ) ,x ∈