Semyon M. Meerkov

Feedback control of congestion in packet switching networks: the case of a single congested node

Addresses a rate-based feedback approach to congestion control in packet switching networks where sources adjust their transmission rate in response to feedback information from the network nodes. Specifically, a controller structure and system architecture are introduced and the analysis of the resulting closed loop system is presented. Conditions for asymptotic stability are derived. A design technique for the controller gains is developed and an illustrative example is considered. The results show that, under appropriately selected control gains, a stable (nonoscillatory) operation of store-and-forward packet switching networks with feedback congestion control is possible. >

Vibrational control of nonlinear systems: Vibrational stabilizability

In this work, the theory of vibrational control for nonlinear systems is developed. The present paper gives criteria for stabilizability of nonlinear systems by linear multiplicative vibrations, by almost periodic forcing and by vector additive vibrations. Illustrative examples are also considered. In a subsequent paper, the problem of vibrational controllability and transient behavior will be addressed.

Vibrational feedback control: Zeros placement capabilities

It is shown that in addition to closed-loop pole placement, vibrational feedback controllers lead, in the sense specified below, to a possibility of open-loop zeros assignability. On this basis, the superior performance characteristics of continuous-time periodic controllers, discovered in [3]-[6], are explained.

DT-bottlenecks in serial production lines: theory and application

The bottleneck (BN) of a production line is a machine that impedes the systems performance in the strongest manner. It has been shown in previous work that the so-called downtime bottlenecks (DT-BNs) are of main industrial importance. In this paper, a method for DT-BN identification is developed in the framework of serial production lines with unreliable (Markovian) machines and finite buffers. The identification tool derived is based on the probabilities of machine blockages and starvations. To evaluate these probabilities, a novel aggregation technique is proposed. The results obtained are applied to the design of a production line at an automotive component plant.

A system-theoretic property of serial production lines: improvability

A production system is described as improvable if the limited resources involved in its operation can be redistributed so that a performance measure is improved. In this paper the property of improvability is analysed for the case of a particular system, the serial production line. Improvability of the production rate with respect to machine efficiency and work-in-process distribution is analysed, appropriate indicators of improvability are derived, and their utilization in the process of continuous improvement is discussed. It is shown, in particular, that in a well-designed system each buffer is on average half-full, and each intermediate machine has equal frequencies of blockages and starvations

c-Bottlenecks in serial production lines: Identification andapplication

The bottleneck of a production line is a machine that impedes the system performance in the strongest manner. In production lines with the so-called Markovian model of machine reliability, bottlenecks with respect to the downtime, uptime, and the cycle time of the machines can be introduced. The two former have been addressed in recent publications [1] and [2]. The latter is investigated in this paper. Specifically, using a novel aggregation procedure for performance analysis of production lines with Markovian machines having different cycle time, we develop a method for c-bottleneck identification and apply it in a case study to a camshaft production line at an automotive engine plant.

Homogeneous, asymptotically reliable serial production lines: theory and a case study

A model of homogeneous, asymptotically reliable serial production lines is introduced, analyzed, and applied to the problem of performance evaluation of a modular paint shop at an automobile assembly plant. The results obtained indicate that the homogeneous, asymptotically reliable production lines are, on the one hand, simpler for analysis than traditional models and, on the other, sufficiently rich to reflect the behavior of real manufacturing systems. The asymptotic theory developed gives analytical formulas for production rates as a function of system parameters and, therefore, can be used as an inexpensive tool for the analysis and design of manufacturing processes in mass production systems, eliminating, in some cases, the necessity of complex and costly computer simulations. >

A resilient condition assessment monitoring system

An architecture and supporting methods are presented for the implementation of a resilient condition assessment monitoring system that can adaptively accommodate both cyber and physical anomalies to a monitored system under observation. In particular, the architecture includes three layers: information, assessment, and sensor selection. The information layer estimates probability distributions of process variables based on sensor measurements and assessments of the quality of sensor data. Based on these estimates, the assessment layer then employs probabilistic reasoning methods to assess the plant health. The sensor selection layer selects sensors so that assessments of the plant condition can be made within desired time periods. Resilient features of the developed system are then illustrated by simulations of a simplified power plant model, where a large portion of the sensors are under attack.

Feedback control of congestion in packet switching networks: The case of multiple congested nodes

In this paper, an analytical method for the design of a congestion control scheme in packet switching networks is presented. This scheme is particularly suitable for implementation in ATM switches, for the support of the available bit rate (ABR) service in ATM networks. The control architecture is rate-based with a local feedback controller associated with each switching node. The controller itself is a generalization of the standard proportional-plus-derivative controller, with the difference that extra higher-order derivative terms are involved to accommodate the delay present in high-speed networks. It is shown that, under the specific service discipline introduced here, there exists a set of control gains that result in asymptotic stability of the linearized network model. A method for calculating these gains is given. In addition, it is shown that the resulting steady state rate allocation possesses the so-called max-min fairness property. The theoretical results are illustrated by a simulation example, where it is shown that the controller designed, using the methods developed here, works well for both the service discipline introduced in this paper and for the standard FCFS scheme.

Buffer Capacity for Accommodating Machine Downtime in Serial Production Lines

This paper investigates the smallest level of buffering (LB), necessary to ensure the desired production rate in serial lines with unreliable machines. The reliability of machines is assumed to obey either exponential, or Erlang, or Rayleigh models. The LB is measured in units of the average downtime, T down . The dependence of LB on the reliability model, the number of machines, M , the average uptime, T up , and the efficiency, e = T up /( T up + T down ) is analysed. It is shown that reliability models with larger coefficient of variation require larger LB, and an empirical law that connects LB of the exponential model with those for other reliability models is established. It is shown that LB is an increasing function of M , but with an exponentially decreasing rate, saturating at around M = 10. Also, it is shown that LB does not depend explicitly on T up and is a decreasing function of e . Based on these results, rules-of-thumb are provided for selecting buffer capacity, which guarantee sufficiently high line efficiency.