首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 78 毫秒
1.
A basic theorem describing the convexity of the energy domain for the general family of linear time-invariant (active or passive, reciprocal or non-reciprocal, lumped or distributed, single variable or multivariable) physical system {T} is proved.Theorem: Let F = P + jQ represent the complex energy associated with any linear physical system T (n-port). For any specified excitation of frequency s and the family of constant energy content input signals {i:∥i∥= constant}, the point F describes a convex domain in the {P;Q} plane.Part I contains a mathematical and a network theoretic proof of the foregoing theorem. In Part II the geometric nature of the energy loci for the two-ports is examined. It is shown that for all two-ports with double eigenvalves the energy domain is circular. For two-ports with distinct eigenvalves, the convex energy domain is an ellipse. The geometric characterization of this elliptic domain is examined and examples verified by computer.The concept of convexity is frequently exploited in optimization of energy in electric power system and quadratic cost functions in control theory. In this respect the central theorem of this paper, its proof and geometric ramifications should prove to be of basic interest for all linear systems.  相似文献   

2.
Modelling and simulation of switching devices with bond graphs is a subject which has no totally satisfying solutions. In this paper, switching devices are represented by flow or effort sources, with a variable circuit topology at switching time. For the simulation, the usual method uses causality resistors to insure integral causality to energy storage elements. The choice of those resistors is quite arbitrary and can lead to stiff systems. We propose, for linear systems, an approach without such resistors. When components lose the integral causality, the order of the state vector changes, provoking the use of pulse variables. A solution is proposed to compute the amplitude of the pulse and the value of the new variables.  相似文献   

3.
A new theorem expands the domain of the scalar immittance functions Z(p) to the operator Z(T) where T(s) is an invertible linear passive n-port system. Elements R, L, C of Z(p) are replaced by operators RI, LT, and [CT] - 1. All frequency transformations may be considered contained in this theorem when T is a scalar.  相似文献   

4.
针对欠驱动漂浮基空间多体系统,将欠驱动关节分解为主动和被动关节,研究用李群和李代数表示其动力学问题.将牛顿-欧拉反向动力学方法推广到适合于含主被动关节的形式,同时得到了漂浮基空间多体系统的主被动关节递推动力学建模方法.该方法可以用于对链式、树形拓扑结构的空间系统建模,也可用于对采用有限段方法建立的柔性梁式构件的离散模型进行高效率递推计算.结果表明,用李群李代数理论中的方法和符号更有助于形成递推的高效动力学建模,得到的动力学公式简明、清晰.  相似文献   

5.
In this paper, the approximation problem of T–S fuzzy linear singular system for a class of nonlinear singular system with derivative of input is considered and the nonlinear singular system has impulses. Consider a numerical example and a two-wheel drive robot, the T–S fuzzy singular systems are calculated for original system with derivative of input. According to solvability and steps of solving of the two examples, the results are extended to more generally nonlinear singular system with derivative of input. The theorem and algorithm that are given if input-state system is bounded impulse-free item and separable impulse item, it can be approximated by T–S fuzzy singular system with arbitrary accuracy. Finally, a numerical simulation is carried out to show the consistency with theoretical analysis and illustrate the effectiveness of approximation.  相似文献   

6.
Applying a state-space technique and the reactance extraction principle in the realization of multiport network functions by means of grounded active RC networks containing grounded voltage-controlled voltage sources (VCVSs) and using a minimum number of grounded capacitors, a new theorem concerning the least upper bound on the number of grounded VCVSs sufficient for the realization is proved. The obtained expression for the least upper bound allows one to generate the least upper bound on the number of VCVSs sufficient to realize each of all possible different types of multiport network functions.The proof of the theorem is based upon the use of results concerning the number of VCVSs sufficient and, in general, necessary to realize an arbitrary real multiport network function by means of grounded active resistive multiport networks embedding grounded VCVSs, and on the results concerning the possibility of choosing a convenient equivalent minimal system realization.  相似文献   

7.
The linear canonical transform (LCT) has been shown to be a powerful tool for optics and signal processing. Many theories for this transform are already known, but the uniform sampling theorem, as well as the sampling rate conversion theory about arbitrary lattices sampling in the LCT domain are still to be determined. Focusing on these issues, this paper carefully investigates arbitrary lattices sampling, the sampling with separable matrices and nonseparable matrices, to obtain uniform sampling theorem and the sampling rate conversion theory in the LCT domain. Firstly, the spectral expression of the discrete-time signal sampled via arbitrary lattice is deduced in the LCT domain. Based on it we propose the alias-free sampling relationship between two matrices and present the perfect reconstruction expressions for bandlimited signals in the LCT domain. Secondly, for further research on discrete signals to obtain sampling rate conversion theory, we define the multidimensional discrete time linear canonical transform (MDTLCT), as well as the convolution for the MDTLCT. Thirdly, the formulas of multidimensional interpolation and decimation via integer matrices in the LCT domain are derived. Then, based on the results of interpolation and decimation, we make analyses of the sampling rate conversion via rational matrices in the LCT domain, including spectral analyses and the formulas in time domain. Finally, simulation results and the potential applications of the theories are also presented.  相似文献   

8.
The conventional definition of quality factor Q in terms of time-average stored energy is widely assumed to be a measure of the input bandwidth of any ordinary electromagnetic system. But the extent to which this assumption is true has never been established. In the case of all radiating systems, for example, it is known to fail completely. It can be made true quite generally, however, by including only those parts of the total time-average stored energy that give a physically observable contribution to the input bandwidth. Explicit formulas for these newly defined observable stored energies are developed that are valid for any electromagnetic system that is linear, passive, and time-invariant.  相似文献   

9.
In this paper, we deal with the finite-time stability of positive switched linear time-delay systems. By constructing a class of linear time-varying copositive Lyapunov functionals, we present new explicit criteria in terms of solvable linear inequalities for the finite-time stability of positive switched linear time-delay systems under arbitrary switching and average dwell-time switching. As an important application, we apply the method to finite-time stability of linear time-varying systems with time delay.  相似文献   

10.
The generalized sampling theorem of Kramer is derived and interpreted in the context of the theory of linear systems satisfying a generalized form of translation invariance. The results are extended to the form of expansions developed by Papoulis and by Campbell.  相似文献   

11.
In this paper, the global stability of coupled control systems (CCSs) is discussed. Assembling the energy of each vertex system with the help of graph theory, a systematic method for constructing a global Lyapunov function of CCSs is proposed. Then, two kinds of stability criteria by Lyapunov-type theorem and coefficient-type theorem with the condition of the system topology are derived. Subsequently, the theoretical results are applied to the microgrid and the criterion of global asymptotical stability of the microgrid is developed. Meanwhile, based on the actual demand of the microgrid, the secondary frequency distributed consistency sliding mode control of the microgrid is proposed using the consensus algorithm. In the presence of a time-varying load, the control can not only quickly stabilize the frequency at the equilibrium point but also dynamically achieve active power sharing. Finally, the simulation of an islanded microgrid is conducted to test the validity and feasibility of our results.  相似文献   

12.
A complete account is given of the theory of so-called dissipative dynamical systems. The concept of dissipativeness is defined as a general input-output property which includes, as notable special cases, passivity and other properties related to finite-gain. The aim is to treat input-output and state properties side-by-side with emphasis on exploring connections between them. The key connection is that a dissipative system in general possesses a set of energy-like functions of the state. The properties of these functions are studied in some detail. It is demonstrated that this connection represents a direct generalization of the well-known Kalman-Yakubovich lemma to arbitrary dynamical systems. Applications to stability theory and passive system synthesis are briefly discussed for non-linear systems.  相似文献   

13.
This paper is concerned with the problem of state estimation for a class of discrete-time switched positive linear systems (SPLS) with average dwell time (ADT) switching. By utilizing the multiple linear copositive Lyapunov function (MLCLF) approach, the ADT switching is introduced to tackle the state estimation of the underlying system. Some sufficient conditions of the existence of the estimator are derived in terms of a set of linear matrix inequalities for the underlying systems with ADT switching. The results for the SPLS under arbitrary switching can be easily obtained by reducing MLCLF to the common linear copositive Lyapunov function used for the system in the literature. Finally, a numerical example is given to show the validity of the obtained theoretical results.  相似文献   

14.
This brief communication establishes a two-step iterative algorithm based on the orthogonal projection for reducing order of the high-order system transfer function or state variable equations. A two-step iterative algorithm which has been developed by the authors (1) consists of the residue and pole (or eigenvalue) optimization with respect to the objective function. Here, the optimum residues in the first step can be determined by using the reciprocal basis in the projection theorem. The reciprocal basis allows one to avoid performing the Grammian inversion. Selecting the new basis, the optimum poles in the second step can be also applied for the orthogonal projection. Although the resulting reduced-order models derived from this geometrical point of view are consistent with models of a two-step iterative algorithm, the algorithm is thus a computationally much simpler way to derive the formula.  相似文献   

15.
In this paper we investigate some qualitative aspects of the solutions of a new theory of thermoelasticity with voids based on the concept of volume fraction derived by Cicco and Diaco [A theory of thermoelasticity with voids without energy dissipation, J. Thermal Stresses 25 (2002) 493–503]. This theory has been established in the frame work of linear thermoelasticity without energy dissipation. The theory permits the propagation of heat as thermal waves at finite speed. By means of the logarithmic convexity method a uniqueness theorem is proved. With the help of the semigroup theory of linear operators an existence result is obtained.  相似文献   

16.
In this paper, the problem of adaptive fuzzy fault-tolerant control is investigated for a class of switched uncertain pure-feedback nonlinear systems under arbitrary switching. The considered actuator failures are modeled as both lock-in-place and loss of effectiveness. By utilizing mean value theorem, the considered pure-feedback systems are transformed into a class of switched nonlinear strict-feedback systems. Under the framework of backstepping design technique and common Lyapunov function (CLF), an adaptive fuzzy fault-tolerant control (FTC) method with predefined performance bounds is developed. It is proved that under the proposed controller, all the signals of the close-loop systems are bounded and the state tracking error for each step remains within the prescribed performance bound (PPB) regardless of actuator faults and the system switchings. In addition, the tracking errors and magnitudes of control inputs can be reduced by adjusting the PPB parameters of errors in the first and last steps. The simulation results are provided to show the effectiveness of the proposed control scheme.  相似文献   

17.
This paper focuses on the problem of advancing a theorem to estimate the stability bound of delay decay rate α and upper bound delay time τ to guarantee the stability of time-delay systems. Based on the Lyapunov–Krasovskii functional techniques and linear matrix inequality tools, exponential stability and decaying rate for linear time-delay systems are also derived. These results are shown to be less conservative than those reported in the literature. Examples are included to illustrate our results.  相似文献   

18.
This paper studies the global asymptotic stability of a class of interval fractional-order (FO) nonlinear systems with time-delay. First, a new lemma for the Caputo fractional derivative is presented. It extends the FO Lyapunov direct method allowing the stability analysis and synthesis of FO nonlinear systems with time-delay. Second, by employing FO Razumikhin theorem, a new delay-independent stability criterion, in the form of linear matrix inequality is established for ensuring that a system is globally asymptotically stable. It is shown that the new criterion is simple, easy to use and valid for the FO or integer-order interval neural networks with time-delay. Finally, the feasibility and effectiveness of the proposed scheme are tested with a numerical example.  相似文献   

19.
Fractional Fourier domains form a continuum of domains making arbitrary angles with the time or frequency domains on the time-frequency plane. Signal representations in these domains are related to the fractional Fourier transform (FrFT). In this paper, a new proof on the shift-invariance of linear time-frequency distributions on fractional Fourier domains is given. We show that short-time Fourier transform (STFT) is the unique linear distribution satisfying magnitude-wise shift-invariance in the fractional Fourier domains. The magnitude-wise shift-invariance property in arbitrary fractional Fourier domains distinguishes STFT among all linear time-frequency distributions and simplifies the interpretation of the resultant distribution as shown by numerical examples.  相似文献   

20.
《Journal of The Franklin Institute》2023,360(14):10517-10535
Variable fractional-order (VFO) differential equations are a beneficial tool for describing the nonlinear behavior of complex dynamical phenomena. In comparison with the constant FO derivatives, it describes the memory properties of such systems that can vary in the time domain and spatial location. This article investigates the stability and stabilization of VFO neutral systems in the presence of time-varying structured uncertainties and time-varying delay. FO Lyapunov theorem is adopted to achieve order-dependent and delay-dependent criteria for both nominal and uncertain VFO neutral delay systems. The obtained conditions are given in respect of linear matrix inequality by designing a delayed state feedback controller. Simulations verify the main results.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号