Conference Papers-Time Delay

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Note: The papers on this website may differ from the published versions, both in format and in content.

1. S. Tarbouriech, M. Ariola, C.T. Abdallah, "Bounded Controller Design of an ABR Explicit Rate Algorithm for ATM Switches", Proceedings of the 42nd IEEE Conference on Decision and Control, pp.2519-2524, Maui, HI, Dec. 2003.   [pdf]

   Abstract: Congestion control in the Available Bit Rate (ABR) class of Asynchronous Transfer Mode (ATM) networks poses interesting challenges due to the presence of delays, magnitude and rate constraints, and addutive disturbances. In this paper, we consider a discrete-time fixed-structure controller for an ATM/ABR switch, and solve a robust tracking control problem in which the target is a threshold on the queue level.




2. S.I. Niculescu, K. Gu, C.T. Abdallah, "Some Remarks on the Delay Stabilizing Effect in SISO systems", Proceedings of the American Control Conference, pp.2670-2675, Denver, CO, June 2003.   [pdf]

   Abstract: This note addresses the stabilization problem of a class of SISO systems with a time delay in the input, and explore the stabilizing effect of time delay. More precisely? for a fixed feedback gain such that the closed loop system is unstable when the delay is set to zero, we shall present necessary and suficient conditions for the delays such that the stability in closed-loop is achieved, and provide an explicit construction of the controllers. Next, we shall analyze conditions for preserving the closed-loop stability if parametric or time-varying delay uncertainties are present in the control law. Illustrative examples are also proposed.




3. C. T. Abdallah, J. D. Birdwell, J. Chiasson, Z. Tang, N. Alluri and, T. Wang, "The Effect of Communication Time Delays in Parallel Computations", 40th Annual Allerton Conference on Communication, Control and Computing, July 2002.   [pdf]

   Abstract:




4. J. Chiasson, and C. T. Abdallah, "Robust Stability Of Time Delay Systems: Theory", Proceedings of the 3rd IFAC Workshop on Time Delay Systems, pp. 125-130, Santa Fe, NM, Dec. 8-10, 2001.   [pdf]  [ps]

   Abstract: Given that a time-delay system is stable for some delay h₀ > 0, a procedure is given to find the stability interval [h^*; h₂^*] such that h₀ Î [h₁^*; h₂^*] and for all h satisfying h₁^* < h < h₂^*  the system is stable. Further, the system is shown to be unstable if h = h₁^* or h = h₂^*. It is then shown how this can be applied to test the robust stability (with respect to delay values) of a Smith-Predictor based controller.




5. S. Tarbouriech, C.T. Abdallah, M. Ariola, "Bounded Control of Multiple-Delay Systems with Applications to ATM Networks", Proceedings of the 40th IEEE Conference on Decision and Control, pp.2315-2320, Orlando, Fl, Dec. 2001.   [pdf]

   Abstract: Congestion control in the Available Bit Rate (ABR) class of Asynchronous Transfer Mode (ATM) networks poses interesting challenges due to the presence of multiple-delays, magnitude and rate constraints on the inputs and additive disturbances. We consider a fixed-structure controller for an ATM/ABR network, and solve a robust tracking control problem in which the target is a threshold on the queue level.




6. S.I. Niculescu, C.T. Abdallah, "Delay Effects on Static Output Feedback Stabilization", Proceedings of the 39th IEEE Conference on Decision and Control, pp.2811-2816, Sydney, Australia, Dec. 2000.   [pdf]

   Abstract: This paper addresses conditions for characterizing static output feedback controllers including delays for some proper (finite dimensional) transfer functions. The interest of such study is in controlling systems which can not be stabilized by the classical, nondelayed static output feedback, and its difficulty lies in computing delay intervals guaranteeing closed-loop stability, since stability switches/reversals may occur for the same (matrix) gain if the delay is seen as a ‘free’ (design) parameter. The derived conditions are expressed in terms of some appropriate matrix pencils or MIMO Nyquist tests. Illustrative examples are also presented.




7. W.H. Haddad, V. Kapila and C. T. Abdallah, "Stabilization of linear and nonlinear systems with time delay", Proceedings of the American Control Conference, Albuquerque, NM, pp.3220-3224, 1997.   [pdf]

   Abstract: This paper considers the problem of stabilizing linear and nonlinear continous-time systems with state and measurement delay. For linear systems we address stabilization via fixed-order dynamic output feedback compensators and present sufficient conditions for stabilization involving a system of modified Riocati equations. For nonlinear systems we provide sufficient conditions for the design of static full-state feedback stabilizing controllers. The controllers obtained are delay-independent and hence apply to systems with infinite delay.




8. C. T. Abdallah, P. Dorato, J. Benitez-Read and R. Byrne, "Delayed Positive Feedback Can Stabilize Oscillatory Systems", Proceedings of the American Control Conference, San Francisco, CA, pp.3106-3107, 1993.   [pdf]  [ps]

   Abstract: This paper expands on a method proposed in [1] for stabilizing oscillatory systems with positive, delayed feedback. The closed-loop system obtained is shown (using the Nyquist criterion) to be stable for a range of delays.