Limited space heterogeneous queueing problem with an additional special feeding source

This paper considers a limited queue space, single channel, first come first served heterogeneous queueing system. There are two operating states sayE and F. For either state, the time in transition from one state to the other, follows an exponential distribution. In both the states E and F, the arrivals are Poissonian with different parameters and the service times have different exponential distributions. In either state, an additional number M of units join the system whenever the number already there declines to one unit. Thus the channel is busy at all times.     

A general method for writing the dynamical equations of nonholonomic systems with ideal constraints

The basic notions of the dynamics of nonholonomic systems are revisited in order to give a general and simple method for writing the dynamical equations for linear as well as non-linear kinematical constraints. The method is based on the representation of the constraints by parametric equations, which are interpreted as dynamical equations, and leads to first-order differential equations in normal form, involving the Lagrangian coordinates and auxiliary variables (the use of Lagrangian multipliers is avoided). Various examples are illustrated.      

Piotrowski's Infinite Series of Steiner Quadruple SystemsRevisited

The construction of Bays and deWeck [1] of a SteinerQuadruple System SQS(14) was generalized by Piotrowskiin his dissertation ([7], p. 34) to an SQS(2p), p 7 mod 12 with a group transitive on thepoints. However he gave no proof of his construction and hispresesntation was open to misinterpretation. So Hanfried Lenzsuggested to analyse Piotrowski's construction and to supplyit with a proof. In the following we will present Piotrowski'sideas somewhat differently and will furnish a proof of the construction.     

Uniform Stability for Time-Varying Infinite-Dimensional Discrete Linear Systems

Stability for time-varying discrete linear systems in a Banachspace is investigated. On the one hand is established a fairlycomplete collection of necessary and sufficient conditions foruniform asymptotic equistability for input-free systems. Thisincludes uniform and strong power equistability, and uniformand strong l_p-equistability, among other technical conditionswhich also play an essential role in stability theory. On theother hand, it is shown that uniform asymptotic equistabilityfor input-free systems is equivalent to each of the followingconcepts of uniform stability for forced systems: l_p-input l_p-state,e_o-input e_o-state, bounded-input bounded-state, l_p-input bounded-state(with p>1), e_o-input bounded-state, and convergent-inputbounded-state; these are also equivalent to their nonuniformcounterparts. For time-varying convergent systems, the aboveis also equivalent to convergent-input convergent-state stability.The proofs presented here are all ‘lementary’ inthe sense that they are based essentially only on the Banach–Steinhaustheorem.     

Impulsive Markov jump linear systems: Stability analysis and H2 control

In this work, we present an impulsive Markov jump linear system model. We show how the present model generalises previous works from the literature, and we devise necessary and sufficient conditions for stability and performance, together with mode-dependent state-feedback control design conditions for such systems. An applied example shows how the developed theory can be used to control strategies under actuator and sensor failures.     

Suboptimal control of systems with multiple delays

The application of Pontryagin's maximum principle to the optimization of linear systems with time delays results in a system of coupled two-point boundary-value problems involving both delay and advance terms. The exact solution of this system of TPBV problems is extremely difficult, if not impossible. In this paper, a fast-converging iterative approach is developed for obtaining the suboptimal control for nonstationary linear systems with multiple state and control delays and with quadratic cost. At each step of the proposed method, a linear nondelay system with an extra perturbing input must be optimized. The procedure can be extended for the optimization of nonlinear systems with multiple time-varying delays, provided that some of the nonlinearities satisfy the Lipschitz condition.     

Dwell-time stability and stabilization conditions for linear positive impulsive and switched systems

Several results regarding the stability and the stabilization of linear impulsive positive systems under arbitrary, constant, minimum, maximum and range dwell-time are obtained. The proposed stability conditions characterize the pointwise decrease of a linear copositive Lyapunov function and are formulated in terms of finite-dimensional or semi-infinite linear programs. To be applicable to uncertain systems and to control design, a lifting approach introducing a clock-variable is then considered in order to make the conditions affine in the matrices of the system. The resulting stability and stabilization conditions are stated as infinite-dimensional linear programs for which three asymptotically exact computational methods are proposed and compared with each other on numerical examples. Similar results are then obtained for linear positive switched systems by exploiting the possibility of reformulating a switched system as an impulsive system. Some existing stability conditions are retrieved and extended to stabilization using the proposed lifting approach. Several examples are finally given for illustration.     

Hybrid systems: Modelling and analysis using emergent dynamics

In this paper, we discuss modelling and analysis of hybrid systems with physical interaction dynamics. Such systems are typically considered complex and they are modelled using abstractions. Abstractions may, however, unintentionally exclude critical details, leading to partial or false results. Therefore, we study here use of a particle system in modelling and analysis. The novelty of the particle system is that it is designed to reveal interaction dynamics as emergent dynamics; thus, supporting analysis of complex and intricate interaction dynamics with acceptable modelling effort. As the main contribution, we formalize the particle system, and use it to model and analyze hybrid systems, both mechanical and biological, with nontrivial interaction dynamics.     

Analysis of switched linear systems in the plane,part 1: Local behavior of trajectories and local cycle geometry

This paper investigates the problem of control of switched linear systems evolving inR ². The concept of an opposition point is introduced, and its properties related to the existence of closed trajectories in the phase plane are investigated. The geometry of cycles in a neighborhood of an opposition point is also studied.This research was supported by the Office of Naval Research, ONR Contract No. N0013-80-C-0199, and the United States Department of Energy, DOE Contract No. DE-AC01-79-ET-29363.     

Analysis of switched linear systems in the plane,part 2: Global behavior of trajectories,controllability and attainability

The controllability and attainability properties of switched linear systems in the plane are investigated. A main result is the state-space decomposition theorem which classifies various convex regions inR ² according to their controllability properties. A preliminary investigation into the problem of determining minimum switch trajectories between two points inR ² is also presented.This research was supported by the Office of Naval Research, ONR Contract No. N0014-80-C-0199, and the United States Department of Energy, DOE Contract No. DE-AC01-79-ET-29363.     

Stability analysis of a class of nonlinear positive switched systems with delays

This paper addresses the stability problem of delayed nonlinear positive switched systems whose subsystems are all positive. Both discrete-time systems and continuous-time systems are studied. In our analysis, the delays in systems can be unbounded. Two conditions are established to test the local asymptotic stability of the considered systems. The method to compute the domains of attraction is also proposed provided that the system is locally asymptotically stable. When reduced to general nonlinear positive systems, that is, the considered switched system consists of only one mode, an interesting conclusion follows that the proposed nonlinear positive system is locally asymptotically stable for all admissible delays and nonnegative nonlinearities which satisfy an extra condition at the origin, if and only if the system represented by the linear part is asymptotically stable for all admissible delays. Finally, a numerical example is presented to illustrate the obtained results.     

时间可逆系统的等时中心问题

若在中心附近的闭轨线都具有相同的周期,则此中心称为等时中心. 时间可逆多项式系统的等时中心问题是一类公开问题. 为了构造性地解决这一难题,讨论一类范围更广的时间可逆解析动力系统, 给出相应横截交换系统的递推公式,此公式可以用于等时中心条件的推导. 在递推公式的基础上,以吴特征集方法为工具,给出一类时间可逆三次系统具有横截交换系统的充要条件.     

Control by Interconnection and Energy Shaping of the Timoshenko Beam

In this paper, the dynamical control of a mixed finite and infinite dimensional mechanical system is approached within the framework of port Hamiltonian systems. In particular, a flexible beam, modeled according to the Timoshenko theory and in distributed port Hamiltonian form, with a mass under gravity field connected at a free end, is considered. The control problem is approached by generalization of the concept of structural invariant (Casimir function) to the infinite dimensional case and the so-called control by interconnection technique is extended to the infinite dimensional case. In this way, finite dimensional passive controllers can stabilize distributed parameter systems by shaping their total energy, i.e., by assigning a new minimum in the desired equilibrium configuration that can be reached if a dissipation effect is introduced.     

New approach to control and filtering of mechanical systems by using the estimates of their Lagrangians

When a mechanical system is defined by its Lagrangian, some control problems can be solved by using directly the latter, instead of the dynamical equations themselves; this is based upon the property that the dynamics is continuous with respect to the Lagrangian. After stating the main lemma which supports the approach, we consider applications to active mechanical systems, that is to say, with time-varying structural parameters, to tracking control via external applied forces, and to state estimation problems for which we propose a new variational principle.This research was supported by the National Research Council of Canada.     

Controllability of nonlinear integrodifferential systems in Banach space

Sufficient conditions for controllability of nonlinear integrodifferential systems in a Banach space are established. The results are obtained using the Schauder fixed-point theorem.The work of the first and third authors was supported by CSIR, New Delhi, India.     

Null controllability of semilinear integrodifferential systems in Banach space

Sufficient conditions for null controllability of semilinear integrodifferential systems with unbounded linear operators in Banach space are established. The results are obtained using semigroup of linear operators, fractional powers of operators, and the Schauder fixed point theorem. An application to partial integrodifferential equations is given.     

Balancing singular discrete-time systems

In this work, we deal with normalizable-balanced singular systems, that is, singular systems where the obtained closed-loop system is balanced by an appropriate feedback. In the invariant case, we use a proportional and derivative feedback to obtain systems without infinite poles. In addition, the existence and construction of state-feedbacks to obtain normalizable-balanced N-periodic singular systems is analyzed.