See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/285904716 Switched systems based on unstable dissipative systems**This work received financial support from CONACYT through project No. 181002. Article in IFAC-PapersOnLine · December 2015 DOI: 10.1016/j.ifacol.2015.11.021 CITATIONS READS 2 155 1 author: Eric Campos-Cantón Instituto Potosino de Investigación Científica y Tecnológica 123 PUBLICATIONS 1,223 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Special Issue Call for Papers View project Patents: Non-linear dynamics and chaotic behavior View project All content following this page was uploaded by Eric Campos-Cantón on 10 February 2016. The user has requested enhancement of the downloaded file. 4th IFAC Conference on Analysis and Control of Chaotic Systems 4th IFAC26-28, Conference on Analysis Control of Chaotic Systems August 2015. Tokyo, Japan and 4th IFAC IFAC Conference Conference on Analysis Analysis and Control of Chaotic Systems 4th on August 26-28, 2015. Tokyo, Japan and Control of Chaotic Systems Available online at www.sciencedirect.com August August 26-28, 26-28, 2015. 2015. Tokyo, Tokyo, Japan Japan ScienceDirect IFAC-PapersOnLine 48-18 (2015) 116–121 Switched systems based on unstable Switched systems on unstable Switcheddissipative systems based based on unstable systems dissipative systems dissipative systems ∗ E. Campos-Cantón ∗ E. Campos-Cantón ∗∗ E. E. Campos-Cantón Campos-Cantón ∗ ∗ División de Matemáticas Aplicadas, Instituto Potosino de División de Matemáticas Aplicadas, Instituto de ∗ Investigación y Tecnológica A.C., CaminoPotosino a la Presa ∗ DivisiónCientı́fica de Aplicadas, Instituto Potosino de DivisiónCientı́fica de Matemáticas Matemáticas Aplicadas, Instituto Potosino de San Investigación y Tecnológica A.C., Camino a la Presa San José 2055 col. Lomas 4a Sección, 78216, San Luis Potosı́, SLP, Investigación Cientı́fica y Tecnológica A.C., Camino a la Presa San Investigación Cientı́fica y Tecnológica A.C.,San Camino a la Presa San José 2055 col. Lomas 4a Sección, 78216, Luis Potosı́, SLP, México. (e-mail: eric.campos@ipicyt.edu.mx) José 2055 2055 col. col. Lomas Lomas 4a 4a Sección, Sección, 78216, 78216, San San Luis Luis Potosı́, Potosı́, SLP, SLP, José México. (e-mail: eric.campos@ipicyt.edu.mx) México. México. (e-mail: (e-mail: eric.campos@ipicyt.edu.mx) eric.campos@ipicyt.edu.mx) Abstract: In this work we present an unified theory of how to yield multi-scroll chaotic Abstract: In this we present an unified theory of to yield multi-scroll chaotic attractors based on work step function, saturation, hysteresis andhow deterministic Brownian motion. Abstract: In work we an theory how to chaotic Abstract: In this this work we present present an unified unified theory of of how to yield yield multi-scroll multi-scroll chaotic attractors based on step function, saturation, hysteresis and deterministic Brownian motion. This class of systems is constructed with a switching control law by changing the equilibrium attractors based on step function, saturation, hysteresis and deterministic Brownian motion. attractors based on step function, saturation, hysteresis and deterministic Brownian motion. This systems is with aa switching control law by changing the equilibrium point class of anof system. switching control governs position This class ofunstable systems dissipative is constructed constructed with The switching control lawlaw by that changing the the equilibrium This class of systems is constructed with a switching control law by changing the equilibrium point of an unstable dissipative system. The switching control law that governs the of the equilibrium point changes according to the number of scrolls that is displayed in the point of of an an unstable unstable dissipative dissipative system. system. The The switching switching control control law law that that governs governs the the position position point position of the equilibrium point changes according to the number of scrolls that is displayed in the attractor. of the equilibrium point changes according to the number of scrolls that is displayed in of the equilibrium point changes according to the number of scrolls that is displayed in the the attractor. attractor. attractor. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Keywords: Chaos theory; switching functions; system design; piecewise linear analysis; Keywords: theory; multi-scroll attractors. Keywords: Chaos Chaos theory; switching switching functions; functions; system system design; design; piecewise piecewise linear linear analysis; analysis; Keywords: Chaos theory; switching functions; system design; piecewise linear analysis; multi-scroll attractors. multi-scroll attractors. attractors. multi-scroll 1. INTRODUCTION in space using a step function. Lü et al. (2004 A); Deng 1. INTRODUCTION in space using aa step function. Lü etusing al. (2004 A); Deng & Lü (2007) an approach hysteresis that 1. INTRODUCTION in space using Lü al. A); 1. INTRODUCTION in space usingpresented a step step function. function. Lü et etusing al. (2004 (2004 A); Deng Deng & Lü (2007) presented an approach hysteresis that Switched systems have been widely used in many different enables the creation of 1D n-scrolls, 2D n × m-grid scrolls & Lü (2007) presented an approach using hysteresis that & Lü (2007) presented an n-scrolls, approach 2D using hysteresis that Switched systems have been widely used in many different enables the creation of 1D n × m-grid scrolls areas in science. Some recent analysis have been made 3D n × m × l-grid scrolls chaotic attractors. Switched systems systems have have been been widely widely used used in in many many different different and enables the creation of 1D n-scrolls, 2D n × m-grid scrolls Switched enables the creation of 1D n-scrolls, 2D n × m-grid scrolls areas in science. Some recent analysis have been made and 3D n × m × l-grid scrolls chaotic attractors. regarding their stability (See analysis Chiou ethave al. (2010); Ma and areas in science. science. Some recent recent analysis have been made made andthis 3D n nwork, ×m m× × l-grid scrolls chaotic attractors. areas in Some been 3D × scrolls attractors. wel-grid present a chaotic generalized theory that is regarding their stability (See Chiou et al. (2010); Ma & Zhao (2010); Aleksandronov et al. (2011), and the In regarding their stability (See Chiou et al. (2010); Ma In this work, we present a generalized theory that is regarding their stability (See Chiou et al. (2010); Ma capable of explaining different approaches as saturation, & Zhao (2010); Aleksandronov et al. (2011), and the In this work, we present a generalized theory that In this of work, we present a generalized theory that is is references therein). There is someet in generating & Zhao (2010); (2010); Aleksandronov etinterest al. (2011), (2011), and the the capable explaining different approaches as saturation, 3 & Zhao Aleksandronov al. and threshold and step functions in ℜ . This class of systems references therein). There is some interest in generating capable of of explaining explaining different different approaches approaches as saturation, saturation, 3 as chaotic or hyperchaotic attractors multiple scroll with capable references therein). There There is some somewith interest in generating generating threshold and step functions in ℜ . This class of systems references therein). is interest in 3 constructed withfunctions unstable in systems (UDS) chaotic attractors multiple scroll threshold and ℜ of threshold and step step functions indissipative ℜ3 .. This This class class of systems systems this kindor systems. Since the workwith reported by Suykens & is chaotic orofhyperchaotic hyperchaotic attractors with multiple scroll with with is constructed with unstable dissipative systems (UDS) chaotic or hyperchaotic attractors with multiple scroll with (Campos-Cantón et al., 2010) and a control law to display this kind of systems. Since the work reported by Suykens & is constructed with unstable dissipative systems (UDS) is constructed with unstable dissipative systems (UDS) Vandewalle (1993) about scroll from Chua’s this kind of of systems. systems. Sincen-Double the work work reported reported by the Suykens & (Campos-Cantón et al., 2010) and a control law to display this kind Since the by Suykens & various multi-scroll strange attractors. The multi-scroll Vandewalle (1993) about n-Double scroll from the Chua’s (Campos-Cantón et al., 2010) and a control law to display (Campos-Cantón et al., 2010) and a control law to display system(Chua et al., 1986; Madan , 1993), there have been Vandewalle (1993) about n-Double scroll from the Chua’s various multi-scroll strange attractors. The multi-scroll Vandewalle (1993) about n-Double scroll from the Chua’s strange fromattractors. the combination of several system(Chua al., ,, 1993), there been various attractors multi-scrollresult strange attractors. The multi-scroll multi-scroll multi-scroll strange The many differentet to yield multi-scroll attractors system(Chua etapproaches al., 1986; 1986; Madan Madan 1993), there have have been various strange attractors result from the combination of several system(Chua et al., 1986; Madan , 1993), there have been unstable “one-spiral” trajectories by means of a switching many different approaches to yield multi-scroll attractors strange attractors result from the combination of several attractors result from theby combination of several in thedifferent last coupled decades. Thesemulti-scroll approachesattractors may be strange many different approaches to yield yield multi-scroll attractors unstable “one-spiral” trajectories means of a switching many approaches to given by the control law. Without loss of generality we in the last coupled decades. These approaches may be unstable “one-spiral” trajectories by means of a switching unstable “one-spiral” trajectories by means of a switching ranged from modifying the Chua’s system by replacing the in the last coupled decades. These approaches may be by the control law. Without loss of generality we in the from last coupled decades. These approaches may the be given focus our study to the simple jerk equation and a switchranged modifying the Chua’s system by replacing given by the control law. Without loss of generality we given by the control law. Without loss of generality we nonlinear part with different nonlinear functions (Suykens ranged from modifying the Chua’s Chua’s system by replacing replacing the focus our study to the simple jerk equation and a switchranged from modifying the system by the ing control law to generate PWL systems that produce nonlinear part with different nonlinear functions (Suykens focus our study to the simple jerk equation and a switchfocus our study to the simple jerk equation and a switch& Vandewalle, 1993; Suykens et al., 1997; Yalçin et al., nonlinear part part with with different different nonlinear nonlinear functions functions (Suykens (Suykens ing control law to generate PWL systems that produce nonlinear multiscroll & Vandewalle, Suykens et 1997; et control law ing control attractors. law to to generate generate PWL PWL systems systems that that produce produce 2000; Tang et al.1993; , 2001), to the use of nonsmooth nonlinear & Vandewalle, 1993; Suykens et al., al., 1997; Yalçin Yalçin et al., al., ing multiscroll attractors. & Vandewalle, 1993; Suykens et al., 1997; Yalçin et al., 2000; Tang et al. , 2001), to the use of nonsmooth nonlinear multiscroll attractors. multiscroll attractors. functions such as, hysteresis (Lü et al. , 2004 A; Deng & 2000; Tang et al. , 2001), to the use of nonsmooth nonlinear This paper is organized as follow: In Section 2, we intro2000; Tangsuch et al.as, , 2001), to the(Lü useetof al. nonsmooth nonlinear functions hysteresis ,, Sánchez-López 2004 A; Deng & This paper is organized as follow: In Section 2, we introLü, 2007), saturation (Lü et al., 2004 B; et functions such as, hysteresis (Lü et al. 2004 A; Deng & duce the UDS theory to explain the generation of multiThis paper is organized as follow: In Section 2, we introfunctions such as, hysteresis (Lü2004 et al. , Sánchez-López 2004 A; Deng et & This paper is organized as follow:the In generation Section 2, we introLü, 2007), saturation (Lü et al., B; duce the UDS theory to explain of multial., 2010), threshold and step functions (Lü, Murali et al., Lü, 2007), 2007), saturation saturation (Lü (Lü et et al., al., 2004 2004 B; B; Sánchez-López Sánchez-López et et scrolls attractors, along with some examples using the duce the UDS theory to explain the generation of multiLü, duce the UDS theory to explain the generation of multial., 2010), threshold and step functions (Lü, Murali et al., scrolls attractors, along with some examples using 2008; Elwakil et al., and 2000; Yalçin et al.,(Lü, 2002; Yu et al., 2010), threshold and step functions (Lü, Murali et al., al., jerky equation. In along Sectionwith 3 we use examples the UDS using theorythe to scrolls attractors, along with some examples using the al., 2010), threshold step functions Murali et scrolls attractors, some the 2008; Elwakil et al., 2000; Yalçin et al., 2002; Yu et al., jerky equation. In Section 33 as we use the UDS theory to 2005; Lü et al., 2003; Qiang & Xin, 2006; Xie et al., 2008; 2008; Elwakil et al., 2000; Yalçin et al., 2002; Yu et al., generate different approaches step function, saturation jerky equation. In Section we use the UDS theory 2008; Elwakil et2003; al., 2000; Yalçin et2006; al., 2002; Yu et2008; al., jerky equation. Inapproaches Section 3 as we step use function, the UDS saturation theory to to 2005; Lü et al., Qiang & Xin, Xie et al., generate different Campos-Cantón et al.,Qiang 2008,& 2005; Lü Lü et et al., al., 2003; 2003; Qiang &2010). Xin, 2006; 2006; Xie Xie et et al., al., 2008; 2008; and hysteresis. In approaches Section 4 we present a mechanism for generate different as step function, saturation 2005; Xin, generate different approaches as step function, saturation Campos-Cantón et al., 2008, 2010). and hysteresis. In Section 44 we present Campos-Cantón etwith al., piecewise 2008, 2010). 2010). motion generation terms aaaof mechanism UDS, and for in and In present mechanism for Campos-Cantón al., 2008, and hysteresis. hysteresis. In Section Section 4 we wein present mechanism for It is known that et linear functions one can Brownian Brownian motion generation in terms of UDS, and in Section 5 we draw conclusions. It is known that with piecewise linear functions one can Brownian motion generation in terms of UDS, and in Brownian motion generation in terms of UDS, and in achieve the generation of multiscroll chaotic attractors, It is is known known that that with with piecewise piecewise linear linear functions functions one one can can Section 5 we draw conclusions. It achieve the generation of multiscroll chaotic attractors, Section 55 we draw conclusions. Section we draw conclusions. which are based on the location of the equilibrium points achieve the generation of multiscroll chaotic attractors, achieve the generation of multiscroll chaotic attractors, which are on the the points 2. SWITCHED SYSTEMS BASED ON UNSTABLE introduced to the alongof the commutation which are based based on system the location location ofwith the equilibrium equilibrium points which are based on the location of the equilibrium points 2. SWITCHED SYSTEMS BASED ON UNSTABLE introduced to the system along with the commutation DISSIPATIVE SYSTEMS 2. SYSTEMS ON law or threshold bounds and gives a introduced to the the that system alongthe withscrolls the commutation commutation 2. SWITCHED SWITCHED SYSTEMS BASED BASED ON UNSTABLE UNSTABLE introduced to system along with the DISSIPATIVE SYSTEMS law or threshold that bounds the scrolls and gives a DISSIPATIVE specific the bounds flow. The about law or direction threshold tothat that bounds themultiple scrolls papers and gives gives a DISSIPATIVE SYSTEMS SYSTEMS law or threshold the scrolls and a specific direction to flow. multiple papers this topic have been different ideasabout and We consider the class of affine linear system given by specific direction to the thepresented flow. The Theas multiple papers about specific direction to the flow. The multiple papers about consider the class of affine linear system given by this topic have been presented as different ideas and several theories have been developed to explain how to We We this topic have been presented as different ideas and We consider consider the the class classχ̇of of=affine affine linear system given given by by (1) Aχ +linear B, system this topic have have been been presented as different ideas and several theories developed to explain how to χ̇ = Aχ + B, (1) generatetheories multi-scroll attractors. to A natural several theories havechaotic been developed developed to explainquestion how to to several have been explain how χ̇ = Aχ + B, (1) generate multi-scroll chaotic attractors. A natural question (1) TAχ + B, n is the following: is there a theory thatA these where χ = [x1 , . . . ,χ̇x= generate multi-scroll chaotic attractors. Aexplains natural all question ] ∈ ℜ is the state variable, generate multi-scroll chaotic attractors. natural question n T n is the following: is there a theory that explains all these where χ = [x , . ∈ ℜ is the state variable, T. . , xn ]n approaches as one? For example, Yalçin et al. (2002), T n 1 is the following: is there a theory that explains all these B = [βχ .= . . , [x β1n,,]..T.. ..∈,, x ℜ real vector, A = T stands is the following: is there aexample, theory that explains all(2002), these where ∈ is state variable, n ]]n χ11 ,,n×n ∈ ℜ ℜn for is aathe the state variable, approaches as Yalçin et 1n ]T ∈xℜ n B = [β ..= .. .. ,, [x β stands for real vector, A = reported that 1D, For 2D and 3D-grid of scrolls be where n approaches as aone? one? For example, Yalçin et al. al. may (2002), [α ] ∈ ℜ denotes operator. Considering that T ∈ aℜlinear n stands approaches as one? For example, Yalçin et al. (2002), B = [β , β ] for a real vector, = ij 1 n n×n B =] ∈[βℜ . . . , denotes βn ] ∈ aℜlinear stands for a real vector, A A = reported that aa 1D, 2D and 3D-grid of scrolls may be 1 ,n×n [α operator. Considering that introduced locating them around the equilibrium points ij reported that 1D, 2D and 3D-grid of scrolls may be matrix A is not singular then the equilibrium point is n×n reported that a 1D,them 2D and 3D-grid of scrolls may be [α [αij ] ∈ ℜ denotes a linear operator. Considering that ] ∈ ℜ denotes a linear operator. Considering that introduced locating around the equilibrium points ij matrix A is not singular then the equilibrium point is ∗ −1 introduced locating them around around the equilibrium points matrix ⋆ located at χ = −A B. The dynamics of the system is introduced them points A is not singular then the equilibrium point This work locating received financial support the from equilibrium CONACYT through ∗ not singular −1 matrix A is thendynamics the equilibrium point is is ⋆ This work received financial support from CONACYT through located at χ = −A B. The of the system ∗ −1 ⋆ This No. given byat matrix due define a vector field Ax.system Suppose project 181002. ∗ =A −1to located χ −A B. The dynamics of the is work received financial support from CONACYT through ⋆ located at χ = −A B. The dynamics of the system is This work received financial support from CONACYT through given by matrix A due to define a vector field Ax. Suppose project No. 181002. given project given by by matrix matrix A A due due to to define define aa vector vector field field Ax. Ax. Suppose Suppose project No. No. 181002. 181002. Copyright © 2015, 2015 IFAC 116 Hosting by Elsevier Ltd. All rights reserved. 2405-8963 © IFAC (International Federation of Automatic Control) Copyright © 2015 IFAC 116 Copyright © 2015 IFAC 116 Peer review under responsibility of International Federation of Automatic Copyright © 2015 IFAC 116Control. 10.1016/j.ifacol.2015.11.021 IFAC CHAOS 2015 August 26-28, 2015. Tokyo, Japan E. Campos-Cantón et al. / IFAC-PapersOnLine 48-18 (2015) 116–121 that the matrix A has j negative eigenvalues λ1 , . . . , λj and n−j positive eigenvalues λj+1 , . . . , λn . Let {v1 , . . . , vn } be the corresponding set of eigenvectors. Then the stable and unstable subspaces of the affine linear system (1), E s and E u , are the linear subspaces spanned by {v1 , . . . , vj } and {vj+1 , . . . , vn }, respectively; i.e., E s = Span{v1 , . . . , vj }, E u = Span{vj+1 , . . . , vn}. According to the above discussion and considering real and complex eigenvalues, it is possible to define a UDS as follows: Definition 1. A system given by (1) in ℜn and eigenvalues λi ,∑ with i = 1, . . . , n. We said that system (1) is a UDS n if i=1 λi < 0, and at least one λi is a positive real eigenvalue or two λi are complex eigenvalues with positive real part Re{λi } > 0. None of them is pure imaginary eigenvalue. The next proposition is important to mention in order to realize what kinds of behaviors are possible to find in the system given by (1). Proposition 2. Let the system (1) be a UDS with ordered real and complex eigenvalues set Λ = {λ1 , . . . , λn } and Re{λ1 } ≤ . . . ≤ Re{λj } < 0 < Re{λj+1 } ≤ . . . ≤ Re{λn }. Then, the system has a stable manifold E s ⊂ ℜn and another unstable E u ⊂ ℜn with 1 ≤ j ≤ n and the following statements are true: (a) All initial condition χ0 ∈ ℜn /E s leads to an unstable trajectory that goes to infinity. (b) All initial condition χ0 ∈ E s leads to a stable trajectory that settles down at χ∗ and the system does not generate oscillations. (c) The basin of attraction B is E s ⊂ ℜn . Now, we consider a switching system based on the affine linear system (1) given by χ̇ = Aχ + B(χ), B1 , if χ ∈ D1 ; (2) .. B(χ) = ... . B , if χ ∈ D . k k Where ℜn = ∪ki=1 Di and ∩ki=1 Di = ∅. Thus, the equilibria of the system (2) is χ∗i = −A−1 Bi , with i = 1, . . . , k. So the goal is to define vectors Bi which can generate a class of dynamical systems in Rn with oscillations into an attractor, that is, the flow Φ(χ(0)) of the system (2) is trapped in an attractor A by defining at least two vectors B1 and B2 . This class of systems can display various multiscroll strange attractors as a result of the combination of several unstable “one-spiral” trajectories by means of the commutation of B(χ), i.e., we are interested in a vector field which can yield multi-scroll attractors constitute by a commuted vector, Bi with i = 1, . . . , k and k ≥ 2. Each domain, Di ⊂ ℜn , contains the equilibrium χ∗i = −A−1 Bi . According to the above discussion we can define a multiscroll chaotic system based on UDS as follows: Definition 3. A system given by (2) in ℜn and equilibrium points χ∗i , with i = 1, . . . , k and k > 2. We said that system (2) is a multi-scroll chaotic system if each χ∗i 117 117 contains oscillations around and the flow ϕ(χ0 ) generates an attractor A ⊂ ℜn . According to the above discussion, it is possible to define two types of UDS in ℜ3 , and two types of corresponding equilibria, for more details see Campos-Cantón et al. (2010, 2012). Definition 4. Consider the system (1) in ℜ3 with eigen∑3 values λi , i = 1, 2, 3 such that i=1 λi < 0. Then the system is said to be an UDS of type I (UDS-I) if one of its eigenvalues is negative real and the other two are complex conjugate with positive real part; and it is said to be of type II (UDS-II) if one of its eigenvalues is positive real and the other two are complex conjugate with negative real part. In order to illustrate our approach we consider the particular case of the linear ordinary differential equation(ODE) written in the jerky form as d3 x/dt3 + α33 d2 x/dt2 + α32 dx/dt + α31 x + β3 = 0, representing the state space equations of (1), where the matrix A and the vector B are described as follows: ) ( ) ( 0 0 1 0 0 , 0 0 1 ;B = (3) A= β3 −α31 −α32 −α33 where the coefficients α31 , α32 , α33 , β3 ∈ ℜ may be any arbitrary scalars that satisfy the definition 4. The characteristic polynomial of matrix A given by (3) takes the following form: λ3 + α33 λ2 + α32 λ + α31 . (4) For simplicity, we vary the coefficient α31 ∈ ℜ and set the others coefficients at α32 = 1, α33 = 1. The coefficient α31 has to assure the system will be UDS-I or UDS-II. Fig. 1 shows the location of the roots, for example the UDS’sII are given for α31 < 0, and the UDS’s-I for α31 > 1. The system has a sink for 0 < α31 < 1. We are setting α31 = 1.5 in order to assure a UDS-I, with these values the eigenvalues result in λ1 = −1.20, λ2,3 = 0.10 ± 1.11i, which satisfy Definition 4 for UDS-I. The parameter β3 is governed by the following switching control law (SCL): { 0.9, if x1 ≥ 0.3; β3 = (5) 0 otherwise. The equilibrium points of the system (2) using the matrix A and vector B defined in (3) and the SCL (5) are χ∗1 = (0.6, 0, 0)T with B1 = (0, 0, 0.9)T and χ∗2 at the origin with B2 = (0, 0, 0)T . Figure 2 a) depicts the projection of the double-scroll attractor onto the (x1 , x2 ) plane generated by the β3 SCL (5) under equations (2)-(3). Now, if we change the control signal given by SCL then it is possible to generate an attractor with triple-scroll. Therefore the β3 parameter is given as follows: { 0.9, if 0.3 ≤ x1 ; if −0.3 < x1 < 0.3; (6) β3 = 0 −0.9, if x1 ≤ −0.3. Notice that χ∗3 = −χ∗1 . This issue is intentionally defined to illustrate the symmetry scrolls. Figure 2 b) shows the IFAC CHAOS 2015 118 August 26-28, 2015. Tokyo, Japan E. Campos-Cantón et al. / IFAC-PapersOnLine 48-18 (2015) 116–121 The β3 , given by the SCL’s (7) and (8), introduces other equilibrium points located at χ∗4 = (1.2, 0, 0)T and χ∗5 = (−1.2, 0, 0)T , respectively. Figures 2 c) and 2 d) show the projection of the quadruple-scroll and quintuple-scroll attractors given by the β3 SCL (7) and (8), respectively. Introducing more equilibrium points to the system, along with the corresponding switching control law, one can create any number of scrolls inside the 1D, 2D and 3Dgrid Campos-Cantón (2016). The direction of the scrolls is not restricted to the state variable direction. Real part of the roots 1 0.5 0 −0.5 3. MULTI-SCROLL ATTRACTORS VIA UDS IN R3 −1 −1.5 −2 −1 0 α31 1 2 Fig. 1. The location of the roots: UDS-II for α31 < 0; UDS-I for α31 > 1. In order to make a generalization on the UDS’s-I and illustrate our approach, in this section we analyze some of the systems that generate n-scrolls by different methods as hysteresis, step function and saturation. We focus on those that describe their experiments using the ODE written in the jerky form (3). This type of system, was implemented in Elwakil et al. (2000); Yalçin et al. (2002); Xie et al. (2008); Lü et al. (2004 A); Lü et al. (2004 B); Deng & Lü (2007), and the characteristic polynomial takes the form (4) regardless of the method used ( hysteresisLü et al. (2004 A), saturationLü et al. (2004 B), step functionYalçin et al. (2002)). Hysteresis: Lü et al. (2004 A), implemented a hysteresis series to obtain multiscroll chaotic attractors in 1-D nscroll, 2-D n × m-grid scroll, and 3-D n × m × l-grid scroll. The hysteresis series is given by equations (1), (2) and (3) in Lü et al. (2004 A), as follows: { 0, for x1 < 1, h(x1 ) = (9) 1, for x1 > 0, where h(x1 ) is the hysteresis function that is used to define the following hysteresis series, q p ∑ ∑ h(x1 , p, q) = h−i (x1 ) + hi (x1 ), (10) i=1 Fig. 2. The projection of the attractor onto the (x1 , x2 ) plane generated by different control signal: a) (5); b) (6); c) (7); and d) (8), with α31 = 1.5 and initial condition (0.9, 0, 0)T . projection of triple-scroll attractor onto the (x1 , x2 ) plane generated by the β3 SCL (6) under equations (2)-(3). So, quadruple and quintuple scroll attractors are yielded by controlling the β3 parameter as follows: 1.8, if 0.9 ≤ x1 ; 0.9, if 0.3 ≤ x1 < 0.9; β3 = (7) if −0.3 < x1 < 0.3; 0, −0.9, if x1 ≤ −0.3. 1.8, if 0.9 ≤ x1 ; 0.9, if 0.3 ≤ x1 < 0.9; if −0.3 < x1 < 0.3; (8) β3 = 0, −0.9, if −0.9 < x1 ≤ −0.3; −1.8, if x1 ≤ −0.9. 118 i=1 where p and q are positive integers, and hi (x1 ) = h(x1 − i + 1) and h−i (x1 ) = −hi (x1 ). Equation (10) can be recast as follows: −p, for x {1 < −p + 1, i − 1 < x1 < i + 1, h(x1 , p, q) = i, for (11) i = −p + 1, . . . , q − 1, q, for x1 > q − 1. Using the equation (2) but redefine the vector B as follows B = −AΘ(χ), where Θ(χ) = (h(x1 , p, q))T , it is possible to generate multiscroll attractors based on hysteresis series. This approach may be explained with the UDS definition. Considering the parameters described by the authors, matrix A in (3) takes the following values: α31 = 0.8, α32 = 0.72, α33 = 0.6. Therefore the eigenvalues result in λ1 = −0.85, λ2,3 = 0.12 ± 0.95i, where Definition 4 is satisfied for UDS-I. The equilibrium points for the 1-D n-scroll are located along the x-axis. The corresponding switching control law is governed by parameter β3 which takes the form described next: { 1 β3+ , if dx dt > 0, β3 = (12) dx1 β3− , if dt < 0, IFAC CHAOS 2015 August 26-28, 2015. Tokyo, Japan E. Campos-Cantón et al. / IFAC-PapersOnLine 48-18 (2015) 116–121 119 15 10 x 2 5 0 −5 −10 −15 Fig. 3. The projection of the attractor onto the (x1 , x2 ) plane generated by a hysteresis serie. The equilibrium points are marked with asterisk, and the switching surface with a dotted line. where −4, if x1 < −3; −3, if −3 < x1 < −2, −2, if −2 < x1 < −1, −1, if −1 < x1 < 0, β3+ = (13) 0, if 0 < x1 < 1, 1, if 1 < x < 2, 1 2, if 2 < x1 < 3, 3, if x1 > 3, and β3− −3, −2, −1, 0, = 1, 2, 3, 4, if if if if if if if if x1 < −3; −3 < x1 < −2, −2 < x1 < −1, −1 < x1 < 0, 0 < x1 < 1, 1 < x1 < 2, 2 < x1 < 3, x1 > 3. (14) From this it may be concluded that the hysteresis series acts similarly to the switching control law described previously in (2). Equilibrium points are being introduced and the system is forced to oscillate around them. Since both systems are UDS-I, the orbit escapes by means of the unstable manifold E u until it reaches the commutation surface and generates a change to other equilibrium point. This may be seen in Figure 3. Saturation: A saturation function was implemented in Lü et al. (2004 B), this approach may generate 1-D nscroll, 2-D n × m-grid scroll, and 3-D n × m × l-grid scroll chaotic attractors. The saturation function implemented in Lü et al. (2004 B) can be described with UDS-I and -II by means of equation (3) and a switching control law taking the following form: { 7, if x1 > 1, β3 = 0, if |x1 | ≤ 1, (15) −7, if x1 < −1. According to the specific values described in Lü et al. (2004 B), the matrix A in (3) takes the following values α31 = α32 = α33 = 0.7, for |x1 | > 1. The system presents a double scroll chaotic attractor with eigenvalues λ1 = −0.848, λ2,3 = 0.074 ± 0.905i, satisfying Definition 4 for UDS-I. The equilibrium points are located at (±10, 0, 0)T , 119 −20 −10 0 x1 10 20 Fig. 4. The projection onto the plane (x1 , x2 ) of the attractors generated by a saturation serie. The equilibrium points are marked with red dots, and the switching surface with black lines at x1 = ±1. this may be appreciated in Figure 4. For |x1 | ≤ 1, the matrix A in (3) takes the following values α31 = 6.3, α32 = α33 = 0.7. Thus, A has the following eigenvalues λ1 = 1.530, λ2,3 = −1.115 ± 1.694i, satisfying Definition 4 for UDS-II. The equilibrium point is located at the origin (0, 0, 0)T . Here there are three equilibrium points and the flow of the system crosses from one to another because the system contains UDS-I and -II. In this way it is possible to describe all systems presented in Lü et al. (2004 B). The mechanism of generation of the attractor presented in Fig. 4 in terms of UDS is given as follows: { type I, if x1 > 1, U DS = type II, if |x1 | ≤ 1, (16) type I, if x1 < −1. Notice that the Chua’s system can be described in a similar way that saturated functions for generation of multiscroll attractors. Here there are some open questions, for example about the length of the middle region that contains the UDS-II in order to maintain the attractor, another question is about the minimum proximity of the equilibrium point to the commutation surface in order to generate a scroll around it. Step function: Yalçin et al. (2002) made an implementation of a step function from which they can generate 1D, 2D, 3D-grid scroll attractors. The step function depicted in equations (3) and (4) in Yalçin et al. (2002), may be interpreted with UDS-I as follows: 0, if x1 < 0.5 1, if 0.5 ≥ x1 > 1.5 β3 = (17) 2, if 1.5 ≥ x1 > 2.5 3, if x1 ≥ 3.5. Using the parameters described by the authors (α31 = 0.8, α32 = α33 = 1) according to the five 1D-grid scroll as shown in Figure 5. The eigenvalues result in λ1 = −0.89, λ1,2 = 0.04 ± 0.94i. Here the equilibrium points are (i, 0, 0)T with i = 0, 1, 2, 3, 4. The switching control law is taking the same form as the system described in Section 2. So Definition 4 is also satisfied for UDS-I. IFAC CHAOS 2015 120 August 26-28, 2015. Tokyo, Japan E. Campos-Cantón et al. / IFAC-PapersOnLine 48-18 (2015) 116–121 methods to yield multiscroll attractors: hysteresis, step function and saturation, and can be extended to Brownian motion generation. Controlling the vector B with the switching control law it is possible to generate any number of scrolls in whatever direction. Also, the UDS approach has been extended to generate hyperchaotic multiscroll attractors. The future work is about the generation of 2D and 3D grids of families of multi-scroll attractor given by UDS-I and II, in the same spirit that Aguirre-Hernádez et. al. (2015) gave a family based on UDS-I. REFERENCES Fig. 5. The projection onto the plane (x1 , x2 ) of the attractors generated by a step function. The equilibrium points are marked with asterisk, and the switching surface with a dotted line. 4. BROWNIAN MOTION The mechanism described by Huerta-Cuellar et. al. (2014) for Brownian motion generation can be described in terms of UDS-I. The Langevin model for Brownian motion generation is given as follows: ẋ = y, (18) ẏ = −γy + Af (t). The evolution of the flow Eq. (18) with the stochastic term Af exhibits the characteristic properties of Brownian motion, such as a linear growth of the mean square displacement and an approximately -2 power law frequency spectrum. In order to generate deterministic Brownian motion Huerta-Cuellar et. al. (2014) added an additional degree of freedom to the phenomenological system Eq. (18), where the fluctuating acceleration Af (t) is now replaced by variable z defined by a third differential equation. The proposed variable z, which acts as fluctuating acceleration, produces a deterministic dynamical motion with a chaotic behavior. When a particle is moving in a fluid, friction and collisions with other particles existing in the environment necessarily produces changes in the motion velocity and acceleration; all these changes are considered in the jerky equation. In this work, a UDS-I was defined as follows: ẋ = y, ẏ = −γy + z, (19) ż = −α1 x − α2 y − α3 z + α4 , where γ, αi , i = 1, . . . , 4, are parameters. The first two equations are derived from the Langevin Eq. (18) with a little change: the stochastic term is replaced by the deterministic term which is technically known as jerk. A trajectory of deterministic Brownian motion was presented by switching one hundred UDS-I. The parameters values were γ = 7 × 10− 5α1 = 1.5, α2 = 1.2, α3 = 0.1. The eigenvalues result in λ1 = −0.8303, λ1,2 = 0.3652±1.2935i that correspond to a UDS-I. Details can be seen in HuertaCuellar et. al. (2014). 5. 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