Abstract
In this article, global asymptotic stability analysis, and mixed and passive control for a class of control fractional-order systems is investigated. Based on the fractional-order Lyapunov stability theorem and some properties of fractional calculus, we propose sufficient conditions to ensure the mixed and passivity performance. More relaxed conditions by employing the new type of augmented matrices by using Kronecker product terms can be handled, which can be introduced. The derived criteria are expressed in terms of linear matrix inequalities that which can be checked numerically using toolbox MATLAB. Finally, two numerical examples are provided to demonstrate the correctness of the proposed results.
1. Introduction
Fractional calculus is a branch of applied mathematics that contain integrals and derivatives of any order, which may be developed as a superset of conventional integer order calculus. Many authors pointed out that the derivatives and integrals of non-integer-order are more appropriate for representing the properties of several real time materials and processes, e.g., polymers. That is, the generalization of the derivative order of a parameter enriches the system performance by expanding degree of freedom flexibility. The real-world applications of fractional-order differential equations are viscoelastic structure, system identification, quantitative finance and so on. Fractional order stability and synchronization results have been realized, see the reference therein [1–10].
The dynamics of complex networks have been widely studied on the basis of complex network models, with a focus on the interaction between the complexity of the overall topology and the local dynamical characteristics of the connected nodes. Hence, fractional-order complex networks can better model and reveals some remarkable results have been obtained [11–14]. The behaviour of the network nodes is similar throughout the existing literature on complex dynamical networks that takes drive and response systems under consideration. Examples of such complex networks can be found everywhere in our daily life, from physical objects such as the Internet, multi agent systems, neural networks, living organisms, etc. Numerous collective phenomena, including self-organization, synchronization, and spatiotemporal chaos, occur in complex dynamical neural networks. Synchronization, as a very important phenomenon, has often appeared in papers [15–17].
It is completely found out that the reason of controllers/filters is to assure the closed-loop error systems are stable with an norm bound restricted to disturbance attenuation [18, 19]. On the other hand, the Mixed and passivity control has been proved [20, 21]. Recently, state feedback control of commensurate fractional-order systems and model reduction for positive fractional-order systems were investigated in [22, 23]. The main key of passivity idea is that the passive properties can preserve the system inside stable and explicit to the belongings of vitality application. For the other one, thinking mixed and passive performance when designing controller is the ideal solution. It is really well worth bringing up that the ideal performs an critical role with inside the layout and evaluation of linear and nonlinear systems, which has attracted significant interest over the past decades [24–28]. To the best of the author knowledge, no results have been reported on the mixed and passive control for fractional-order system with hybrid couplings.
Furthermore, time delay in practice for the coupling connections in the neural networks is inevitable because of the finiteness of signal transmission speed over the links. The delayed coupling could describe the decentralized nature of real-world couple systems. Studying the synchronization of fractional-order neural networks with hybrid coupling is thus still a difficult but interesting topic. In real-world situation, time delay is ubiquitous in many physical systems due to the finite switching speed of amplifiers, finite signal propagation time in networks and so on.
The main contributions of this work are highlighted below:(1)We studied the problem of mixed and passive analysis of delayed fractional-order complex dynamical networks with hybrid coupling.(2)Novel Lyapunov functional consisting of Kronecker product is constructed to derive the main results.(3)This paper is to discuss issue of the fractional-order complex networks under a new reliable protocol subject to coupling delay.(4)The derivation process that leads in the feasible criteria applies a variety of inequality lemmas.(5)By using the Lyapunov direct method, a new sufficient condition is proposed to ensure the system to be global asymptotically stable with mixed and passivity performance level.(6)Then the criterion is adopted to design a state feedback controller in terms of linear matrix inequalities, which can be solved numerically by using standard computational LMI-based algorithms.(7)All the derived conditions obtained here are expressed in terms of LMIs whose feasibility can be easily checked by using numerically efficient MATLAB LMI Control toolbox.
2. Model Description and Preliminaries
There are four common definitions of fractional calculus, namely Riemann Liouville, Hadamard and Caputo definitions. Among them, Caputo fractional-order derivative is well understood in physical situations and more applicable to real-world problems, because of the same initial conditions as in integer-order derivatives. Thus, only Caputo fractional-order derivative is used in this paper. We firstly give some useful definitions and lemmas fractional derivative of order .
Definition 1 (see [29]). The Caputo fractional derivative of order for a function is defined bywhere n is a positive integer. In particular, when , we have
Lemma 1 (see [30]). Let be a differentiable vector-valued function. Then for , we havewhere is a symmetric positive definite matrix.
Lemma 2 (see [31]). If and , thenIn particular, when , we have
Lemma 3 (see [32]). For a given matrixWith , , then the following conditions are equivalent:
Lemma 4 (see [33]). Let denote the notation of Kronecker product. Then, the following relationships hold
Lemma 5 (see [34]). Let , , and , , , and , with , then
Lemma 6 (see [35]). Let H, S be any real matrix, , , , , and , with , and and are functions and defined in system (1). Then for any vectors p and q with appropriate dimensions, the following matrix inequality holds:
Property 1 (see [9]). If , then the following property
Property 2 (see [9]). For any constants , and two functions , , we have
Assumption 1 (see [36]). Bounded functions satisfying and for all Now the activation function , and , some constants are , , , , , and satisfyWe denote
3. Main Result
Consider the fractional-order complex dynamical network model consisting of coupled nodes of the formwhere , be the state vector of the th node at time ; is Bernoulli distributed stochastic variable such that , is a coupling delay and assumed to satisfying and , where , are known constants. c is coupling strength; , , denote the connection weight matrix and the delayed connection weight matrix, respectively. and represent constants inner coupling matrix at time t and the time ; is real constant matrices with appropriate dimension. and are the coupled configuration matrix and its elements satisfies the following conditions: if there is a connection between the nodes k and j, then ; otherwise for and the diagonal elements = .
Combining with the sign of Kronecker product, model (1) can be rewritten as
Definition 2 (see [35]). The system (1) is said to be globally asymptotically stable with mixed and passivity performance , if the following requirements are satisfied simultaneously;(i)The system (1) is globally asymptotically stable whenever ;(ii)Under zero initial condition, there exists a scalar such that the following condition is satisfiedFor all and any non-zero , where denotes a weighting parameter that represents the trade-off between the weighted performance index and the passivity performance index.
Theorem 1. For given , the system (1) is mixed and passive performance level , if there exist positive definite matrices , and positive diagonal matrices , , , , , such that the following LMIs holds
Proof. Choose the Lyapunov functional candidate:It follows from Lemma 1 that we obtain the -order Caputo derivative of as follows:From Assumption, for any positive diagonal matrices , , , , one hasTo show the mixed and passivity performance of of system (1). Then we have the following estimate:where,From (4), we getIntegrating (8) with respect to t from 0 to , we getBy using Property 1, Property 2 and Lemma 2, we haveOn the other hand, we haveUnder zero initial condition, we obtainHence with zero initial condition. Therefore, we haveBy Definition 2, system (1) is mixed and passivity performance . The proof of theorem is completed.
Theorem 2. The System (1) with is globally asymptotically stable if there exist positive definite matrix , and positive diagonal matrices , , , , , such that the following LMI holds
Proof. Choose the Lyapunov functional candidate:It follows from Lemma 1 that we obtain the -order Caputo derivative of as follows:,From Assumption, for any positive diagonal matrices , , , , one hasCombining (32)–(34),where,From (10), . Therefore, the system (1) with is globally asymptotically stable. This completes the proof of the theorem.
Remark 1. The System (1) can be rewritten asCombining with the sign of Kronecker product, model (15) can be rewritten as
Theorem 3. For given , the system (16) is mixed and passive performance level , if there exist positive definite matrices , and positive diagonal matrices , , , , , such that the following LMIs holds
Proof. Choose the Lyapunov functional candidate:It follows from Lemma 1 that we obtain the -order Caputo derivative of as follows:From Assumption, for any positive diagonal matrices , , , , one hasTo show the mixed and passivity performance of of system (16). Then we have the following estimate:where,From (17), we getIntegrating (22) with respect to t from 0 to , we getBy using Property 1, Property 2 and Lemma 2, we haveOn the other hand, we haveUnder zero initial condition, we obtainHence with zero initial condition. Therefore, we haveBy Definition 2, system (16) is globally asymptotically stable with mixed and passivity performance . The proof of theorem is completed.
4. State Feedback Control
The state feedback controller is designed as
Theorem 4. For given , the system (26) is mixed and passive performance level , if there exist positive definite matrices , and positive diagonal matrices , , , , , such that the following LMIs holds:Then system (26) is stabilizable by the control with disturbance attenuation .
Proof. Through derivation similar to that for Theorem 3,Pre and post-multiply matrix and applying the change of variable, where,Applying the change of variable, where,
Through derivation similar to that for Theorem 3, the proof of Theorem 4 can be completed.
Remark 2. If we consider the order in system (1), then the fractional-order neural networks with a time-varying delay and external disturbance will degenerate to an integer-order one. Correspondingly, the control result in Theorem 1 is still valid for the integer-order delayed neural networks model.
Remark 3. Some recent works investigated the asymptotic stability of the zero solution of fractional-order nonlinear systems. By using Lyapunov directed method, Theorem 2 derives a sufficient condition for the globally asymptotically stable of the fractional-order systems (1) with = 0. The result in Theorem 2 is quite general since many factors global asymptotic stability, are considered. Therefore, the obtained result in Theorem 1 generalizes those given in the previous literature.
Remark 4. Neural networks with time-varying delays have found widespread applications in many different fields such as signal and image processing, pattern recognition, optimization, and learning algorithm. To apply the neural networks to these applications, the stability must be guaranteed, so the stabilization problem has become a hot topic. On the other hand, external disturbances are usually unavoidable in neural networks systems because many reasons such as linear approximation, measurement errors, external noises and modeling inaccuracies. The external disturbances destroy stability, and hinder the performance of the system. One solution can be control method which reduces the effects of external disturbances on the system to a certain acceptable value namely performance. control method have adopted on the stabilization of neural networks with external disturbances.
Remark 5. This paper deals with the problem of control for delayed Fractional order neural networks in the sense of Caputo fractional derivative. How to extend the results in this paper to fractional-order neural networks in the sense of generalized fractional derivative are interesting problems. These require further investigation in future works.
Remark 6. It should be mentioned here that stability theory and Lyapunov stability theory are independent concepts, which neither implies nor exclude each other. Thus, the problem of control for delayed fractional-order neural networks in sense of Lyapunov stability theory is open issues. In this paper, we have investigated the problem of control for fractional-order neural networks with a time-varying delay and external disturbance for the first time. This is the main difference between the strategy developed in this paper and previous works.
Remark 7. Many results on fractional-order neural networks have been published in the recent years. For examples, the problem of stability analysis for fractional-order neural networks with or without time-varying delays was studied in previous decades. Some interesting results on the control problem for some kind of fractional order neural networks with time-varying delays have been proposed.
Remark 8. In recent years, many researchers have investigated synchronization of the isolated fractional-order neural networks with or without delay. They provide many approaches to study synchronization, but they seldom consider delay coupling for fractional-order neural networks. The general fractional-order model includes fractional-order delayed neural networks, fractional-order delayed cellular neural networks, and some famous chaotic systems, such as fractional-order Chuas system, fractional-order Chen system, fractional-order Rossler system, and so forth. We propose a complex networks with hybrid coupling.
5. Illustrative Examples
In this section, some numerical results are provided to demonstrate the main results.
Example 1. Consider the following fractional order complex networks (1),where , , is the state vector, is the unknown disturbance input vector. The system parameters are characterize as:We see that the activation functionsWe consider the problem of mixed and passivity performance for system (1). Then it is easy verify that , , and By using the Matlab solve the LMIs (4) in Theorem 1, we get the feasible solutions:The above results exhibits that the conditions expressed in Theorem 1 have satisfied and hence system (31) with the above given parameters are Mixed passive.
Example 2. Consider the following fractional order complex networks (26),The system parameters are characterize as:Let the function and noise intensity function vector be given byThen it is easy verify that , , , and By using the Matlab solve the LMIs (27) in Theorem 4, we get the feasible solutions:According to Theorem 4, system (32) is asymptotically stable with mixed and passivity performance under state feedback controller is given by
The above results exhibits that the conditions expressed in Theorem 4 have satisfied and hence system (32) with the above given parameters are Mixed passive. Thus the results show that the designed feedback controller is suitable for stabilizing the system (32).
6. Conclusions
Here, we investigate the Mixed and passive analysis of delayed fractional order complex dynamical networks with hybrid coupling. By using the most updated technique on stability analysis of fractional order neural networks, we derive delay-dependent and order-dependent stabilization criteria for fractional order neural networks. Then, the problem of control for fractional order neural networks with a time-varying delay and external disturbance is solved based on the proposed stabilization criteria and some auxiliary properties of fractional calculus. By utilizing a appropriate Lyapunov functional, we have shown that the Mixed passive performance of complex dynamical networks is solvable if a set of linear matrix inequalities (LMIs) are feasible. Finally, numerical examples has been presented to demonstrate the effectiveness of the proposed method. In the future, considering the applications of fractional order complex valued neural networks and stochastic type complex valued neural networks are an interesting topic.
Data Availability
There are no data associated with this work
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
The Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, Saudi Arabia, has funded this project, under grant no. (KEP-51-130-42).