Showing papers by "Swaroop Darbha published in 2002"
02 Dec 2002
TL;DR: It is shown how a two-parameter compensator can always be designed for any Linear Time Invariant plant, that does not have a zero at the origin, to render its step response non-overshooting.
Abstract: In this paper, we show how a two-parameter compensator can always be designed for any Linear Time Invariant (LTI) plant, that does not have a zero at the origin, to render its step response non-overshooting.
56 citations
TL;DR: This paper shows that a necessary and sufficient condition on the plant for the existence of a compensator that makes the closed loop impulse response sign invariant is that there be no real, positive, nonminimum phase plant zeros.
Abstract: In this paper, we consider the problem of designing controllers for discrete-time linear time-invariant (LTI) plants that render the closed-loop impulse response nonnegative. Such systems have a non-undershooting and non-overshooting step response. We first show that the impulse response of any discrete-time LTI system changes sign at least "r" times if it has "r" real, positive zeros outside a circular disk centered at the origin and containing all its poles. We then show that a necessary and sufficient condition on the plant for the existence of a compensator that makes the closed loop impulse response sign invariant is that there be no real, positive, nonminimum phase plant zeros. Finally, we show, by construction, how such a compensator may be synthesized when the plant does satisfy the existence condition.
24 citations
TL;DR: A discrete dynamical systems approach is developed that is particularly well suited to describe the dynamics of large systems such as traffic, which are not large enough to be treated as a continuum.
Abstract: The flow of traffic is usually described using a continuum approach as that of a compressible fluid, a statistical approach via the kinetic theory of gases or cellular automata models. These approaches are not suitable for modeling dynamical systems such as traffic. While such systems are large collections, they are not large enough to be treated as a continuum. We provide a rationale for why they cannot be appropriately described using a continuum model, the kinetic theory of gases, or by appealing to cellular automata models. As an alternative, we develop a discrete dynamical systems approach that is particularly well suited to describe the dynamics of large systems such as traffic.
20 citations
TL;DR: In this paper, the authors considered the problem of designing a decentralized detection filter for a large homogeneous collection of LTI systems, where the collection of systems considered here draws inspiration from platoons of vehicles and the considered interactions amongst systems in the collection are banded and lower triangular, mimicking the typical "look-ahead" nature of interactions in a platoon of vehicles.
Abstract: In this paper, the problem of designing a decentralized detection filter for a large homogeneous collection of LTI systems is considered. The collection of systems considered here draws inspiration from platoons of vehicles, and the considered interactions amongst systems in the collection are banded and lower triangular, mimicking the typical “look-ahead” nature of interactions in a platoon of vehicles. A fault in a system propagates to other systems in the collection via such interactions.The decentralized detection filter for the collection is composed of interacting detection filters, one for each system. The feasibility of communicating the state estimates to other systems in the collection is assumed here. An important concern is the propagation of state estimation errors. In order that the state estimation errors not amplify as they propagate, a ℋ ∞ constraint on the state estimation error propagation dynamics is imposed. A sufficient condition for constructing a decentralized detection filter for the collection is presented. An example is provided to illustrate the design procedure.
17 citations
TL;DR: In this article, it was shown that if the weak interaction condition among systems in the string is satisfied (i.e., the sum of the ∞-norms of the interaction/error propagation transfer functions is less than unity), then the string was L p stable for every p ≥ 1.
Abstract: This note concerns the stability of a string of LTI systems; it is shown here that, if the weak interaction condition among systems in the string is satisfied (i.e., the sum of the ∞-norms of the interaction/error propagation transfer functions is less than unity), then the string is L p stable for every p ≥ 1. Since the ∞-norm of a transfer function is the smallest of all its induced L p norms, the result presented here enables one to obtain a tighter estimate of the geometric rate of attenuation of the states of systems in the string.
16 citations
08 May 2002
TL;DR: In this paper, the authors consider the problem of designing controllers for discrete-time LTI plants that render the closed-loop impulse response non-negative and show that a necessary and sufficient condition on the plant for the existence of a compensator that makes the closed loop impulse response sign invariant is that there be no real, positive, non-minimum phase plant zeros.
Abstract: We consider the problem of designing controllers for discrete-time LTI plants that render the closed loop impulse response non-negative. Such systems have a non-undershooting and non-overshooting step response. We first show that the impulse response of any discrete-time LTI system changes sign at least "r" times if it has "r" real, positive zeros outside a circular disk centered at the origin and containing all its poles. We then show that a necessary and sufficient condition on the plant for the existence of a compensator that makes the closed loop impulse response sign invariant is that there be no real, positive, nonminimum phase plant zeros. Finally, we show, by construction, how such a compensator may be synthesized when the plant does satisfy the existence condition.
14 citations
01 Jun 2002
TL;DR: The idea of the proposed scheme is that if the observed queue length and packet drop probability do not match with the predicted results from the TCP model, then the error must come from the non-responsive traffic; it can then be used for estimating non- responsive traffic.
Abstract: In this paper, we propose a scheme for estimating the proportion of the incoming traffic that is not responding to congestion at a router. The idea of the proposed scheme is that if the observed queue length and packet drop probability do not match with the predicted results from the TCP model, then the error must come from the non-responsive traffic; it can then be used for estimating non-responsive traffic. The proposed scheme utilizes queue length history, packet drop history, expected TCP and queue dynamics to estimate the proportion. We show that the proposed scheme is effective over a wide range of traffic scenarios through simulations.
1 citations