Browsing by Subject "Distributed parameter control systems"
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Item Open Access Aggregate profile clustering for streaming analytics(Oxford University Press, 2015) Abbasoğlu, M. A.; Gedk, B.; Ferhatosmanoğu H.Many analytic applications require analyzing user interaction data. In particular, such data can be aggregated over a window to build user activity profiles. Clustering such aggregate profiles is useful for grouping together users with similar behaviors, so that common models could be built for them. In this paper, we present an approach for clustering profiles that are incrementally maintained over a stream of updates. Owing to the potentially large number of users and high rate of interactions, maintaining profile clusters can have high processing and memory resource requirements. To tackle this problem, we apply distributed stream processing. However, in the presence of distributed state, it is a major challenge to partition the profiles over nodes such that memory and computation balance is maintained, while keeping the clustering accuracy high. Furthermore, in order to adapt to potentially changing user interaction patterns, the partitioning of profiles to nodes should be continuously revised, yet one should minimize the migration of profiles so as not to disturb the online processing of updates. We develop a re-partitioning technique that achieves all these goals. To achieve this, we keep micro-cluster summaries at each node and periodically collect these summaries at a central node to perform re-partitioning. We use a greedy algorithm with novel affinity heuristics to revise the partitioning and update the routing tables without introducing a lengthy pause. We showcase the effectiveness of our approach using an application that clusters customers of a telecommunications company based on their aggregate calling profiles.Item Open Access Aggregate profile clustering for telco analytics(2013) Abbasoğlu, M.A.; Gedik, B.; Ferhatosmanoğlu H.Many telco analytics require maintaining call profiles based on recent customer call patterns. Such call profiles are typically organized as aggregations computed at different time scales over the recent customer interactions. Customer call profiles are key inputs for analytics targeted at improving operations, marketing, and sales of telco providers. Many of these analytics require clustering customer call profiles, so that customers with similar calling patterns can be modeled as a group. Example applications include optimizing tariffs, customer segmentation, and usage forecasting. In this demo, we present our system for scalable aggregate profile clustering in a streaming setting. We focus on managing anonymized segments of customers for tariff optimization. Due to the large number of customers, maintaining profile clusters have high processing and memory resource requirements. In order to tackle this problem, we apply distributed stream processing. However, in the presence of distributed state, it is a major challenge to partition the profiles over machines (nodes) such that memory and computation balance is maintained, while keeping the clustering accuracy high. Furthermore, to adapt to potentially changing customer calling patterns, the partitioning of profiles to machines should be continuously revised, yet one should minimize the migration of profiles so as not to disturb the online processing of updates. We provide a re-partitioning technique that achieves all these goals. We keep micro-cluster summaries at each node, collect these summaries at a centralize node, and use a greedy algorithm with novel affinity heuristics to revise the partitioning. We present a demo that showcases our Storm and Hbase based implementation of the proposed solution in the context of a customer segmentation application. © 2013 VLDB Endowment.Item Open Access Auto-parallelizing stateful distributed streaming applications(2012) Schneider, S.; Hirzel, M.; Gedik, Buğra; Wu, K. -L.Streaming applications transform possibly infinite streams of data and often have both high throughput and low latency requirements. They are comprised of operator graphs that produce and consume data tuples. The streaming programming model naturally exposes task and pipeline parallelism, enabling it to exploit parallel systems of all kinds, including large clusters. However, it does not naturally expose data parallelism, which must instead be extracted from streaming applications. This paper presents a compiler and runtime system that automatically extract data parallelism for distributed stream processing. Our approach guarantees safety, even in the presence of stateful, selective, and userdefined operators. When constructing parallel regions, the compiler ensures safety by considering an operator's selectivity, state, partitioning, and dependencies on other operators in the graph. The distributed runtime system ensures that tuples always exit parallel regions in the same order they would without data parallelism, using the most efficient strategy as identified by the compiler. Our experiments using 100 cores across 14 machines show linear scalability for standard parallel regions, and near linear scalability when tuples are shuffled across parallel regions. Copyright © 2012 by the Association for Computing Machinery, Inc. (ACM).Item Open Access CAPSULE: Language and system support for efficient state sharing in distributed stream processing systems(ACM, 2012) Losa, G.; Kumar, V.; Andrade, H.; Gedik, Buğra; Hirzel, M.; Soulé, R.; Wu, K. -L.Data stream processing applications are often expressed as data flow graphs, composed of operators connected via streams. This structured representation provides a simple yet powerful paradigm for building large-scale, distributed, high-performance applications. However, there are many tasks that require sharing data across operators, and across operators and the runtime using a less structured mechanism than point-to-point data flows. Examples include updating control variables, sending notifications, collecting metrics, building collective models, etc. In this paper we describe CAPSULE, which fills this gap. CAPSULE is a code generation and runtime framework that offers an easy to use and highly flexible framework for developers to realize shared variables (CAPSULE term for shared state) by specifying a data structure (at the programming-language level), and a few associated configuration parameters that qualify the expected usage scenario. Besides the easy of use and flexibility, CAPSULE offers the following important benefits: (1) Custom Code Generation - CAPSULE makes use of user-specified configuration parameters and information from the runtime to generate shared variable servers that are tailored for the specific usage scenario, (2) Composability - CAPSULE supports deployment time composition of the shared variable servers to achieve desired levels of scalability, performance and fault-tolerance, and (3) Extensibility - CAPSULE provides simple interfaces for extending the CAPSULE framework with more protocols, transports, caching mechanisms, etc. We describe the motivation for CAPSULE and its design, report on its implementation status, and then present experimental results. Copyright © 2012 ACM.Item Open Access Cumulant-based parametric multichannel FIR system identification methods(Elsevier, 1994) Özgen, M. T.; Alshebeili, S. A.; Çetin, A. Enis; Venetsanopoulos, A. N.In this paper, “least squares” and recursive methods for simultaneous identification of four nonminimum phase linear, time-invariant FIR systems are presented. The methods utilize the second- and fourth-order cumulants of outputs of the four FIR systems of which the common input is an independent, identically distributed (i.i.d.) non-Gaussian process. The new methods can be extended to the general problem of simultaneous identification of three or more FIR systems by choosing the order of the utilized cumulants to be equal to the number of systems. To illustrate the effectiveness of our methods, two simulation examples are included.Item Open Access Decentralized control and periodic feedback(IEEE, 1994) Khargonekar P. P.; Özgüler, A. B.The decentralized stabilization problem for linear, discretetime, periodically time-varying plants using periodic controllers is considered. The main tool used is the technique of lifting a periodic system to a time-invariant one via extensions of the input and output spaces. It is shown that a periodically time-varying system of fundamental period N can be stabilized by a decentralized periodic controller if and only if: 1) the system is stabilizable and detectable, and 2) the N-lifting of each complementary subsystem of identically zero input-output map is free of unstable input-output decoupling zeros. In the special case of N = 1, this yields and clarifies all the major existing results on decentralized stabilization of time-invariant plants by periodically time-varying controllers. © 1994 IEEEItem Open Access Dynamic boundary control of the timoshenko beam(Pergamon Press, 1992) Morgül, Ö.We consider a clamped-free Timoshenko beam. To stabilize the beam vibrations, we propose a dynamic boundary control law applied at the free end of the beam. We prove that with the proposed control law, the beam vibrations uniformly and exponentially decay to zero. The proof uses a Lyapunov functional based on the energy of the system. © 1992.Item Open Access A dynamic control law for the wave equation(Elsevier, 1994) Morgül, Ö.We consider a system described by the one-dimensional linear wave equation in a bounded domain with appropriate boundary conditions. To stabilize the system, we propose a dynamic boundary controller applied at the free end of the system. The transfer function of the proposed controller is restricted to be a positive real function which could be strictly proper. We then show that, if the transfer function of the controller is strictly proper, then the resulting closed-loop system is asymptotically stable, and if proper but not strictly proper, then the resulting closed-loop system is exponentially stable.Item Open Access An exponential stability result for the wave equation(Elsevier, 2002) Morgül, Ö.We consider a system described by the one-dimensional linear wave equation in a bounded domain with appropriate boundary conditions. To stabilize this system, we propose a dynamic boundary controller applied at the free end of the system. The transfer function of the proposed controller is a proper rational function which consists of a strictly positive real function and some poles on the imaginary axis. We then show that under some conditions the closed-loop system is exponentially stable. © 2002 Published by Elsevier Ltd.Item Open Access On algebraic properties of general proper decentralized systems(Elsevier, 1993) Yu, R.; Sezer, M. E.; Gao, W.The new concepts of the decentralized output feedback variable polynomial, the decentralized output feedback cycle index of general proper systems, and the geometric multiplicities of decentralized fixed modes are introduced. Their computational methods and some algebraic properties are presented. It is shown that the decentralized output feedback cycle index of a general proper system is equal to one when the system has no fixed modes or equal to the maximum of the geometric multiplicities of its decentralized fixed modes. It is also shown that almost all decentralized output feedback can be used to make the zeros of the decentralized variable polynomial distinct, and disjoint from any given finite set of points on the complex plane.Item Unknown Optimal control of a two-stage stochastic hybrid manufacturing system with Poisson arrivals and exponential service times(IEEE, 2005) Gökbayrak, Kağan; Selvi, ÖmerExtending earli'er work on single-stage stochastic hybrid system models, we consider a two-stage stochastic hybrid system where the job arrivals are represented through a Poisson process, and the service times required to attain a desired physical state are exponentially distributed dependent on the controllable process rates. For the case where the costs associated with the process rates and the inventory levels are non-decreasing convex, and the process rates take values from finite sets, we show that there exist threshold policies on both inventory levels for selecting the optimal process rates at each station.Item Unknown Parameter identification for partially observed diffusions(Kluwer Academic Publishers-Plenum Publishers, 1992) Dabbous, T.E.; Ahmed, N.U.In this paper, we consider the identification problem of drift and dispersion parameters for a class of partially observed systems governed by Ito equations. Using the pathwise description of the Zakai equation, we formulate the original identification problem as a deterministic control problem in which the unnormalized conditional density (solution of the Zakai equation) is treated as the state, the unknown parameters as controls, and the likelihood ratio as the objective functional. The question of existence of elements in the parameter set that maximize the likelihood ratio is discussed. Further, using variational arguments and the Gateaux differentiability of the unnormalized density on the parameter set, we obtain the necessary conditions for optimal identification. © 1992 Plenum Publishing Corporation.Item Unknown SPL: an extensible language for distributed stream processing(Association for Computing Machinery, 2017) Hirzel M.; Schneider S.; Gedik, B.Big data is revolutionizing how all sectors of our economy do business, including telecommunication, transportation, medical, and finance. Big data comes in two flavors: data at rest and data in motion. Processing data in motion is stream processing. Stream processing for big data analytics often requires scale that can only be delivered by a distributed system, exploiting parallelism on many hosts and many cores. One such distributed stream processing system is IBM Streams. Early customer experience with IBM Streams uncovered that another core requirement is extensibility, since customers want to build high-performance domain-specific operators for use in their streaming applications. Based on these two core requirements of distribution and extensibility, we designed and implemented the Streams Processing Language (SPL). This article describes SPL with an emphasis on the language design, distributed runtime, and extensibility mechanism. SPL is now the gateway for the IBM Streams platform, used by our customers for stream processing in a broad range of application domains. © 2017 ACM.Item Unknown Stabilization and disturbance rejection for the beam equation(IEEE, 2001) Morgül, Ö.We consider a system described by the Euler-Bernoulli beam equation. For stabilization, we propose a dynamic boundary controller applied at the free end of the system. The transfer function of the controller is a marginally stable positive real function which may contain poles on the imaginary axis. We then give various asymptotical and exponential stability results. We also consider the disturbance rejection problem.Item Unknown Stabilization and disturbance rejection for the wave equation(Institute of Electrical and Electronics Engineers, 1998-01) Morgül, Ö.We consider a system described by the one-dimensional linear wave equation in a bounded domain with appropriate boundary conditions. To stabilize the system, we propose a dynamic boundary controller applied at the free end of the system. The transfer function of the proposed controller is a proper rational function of the complex variable s and may contain a single pole at the origin and a pair of complex conjugate poles on the imaginary axis, provided that the residues corresponding to these poles are nonnegative; the rest of the transfer function is required to be a strictly positive real function. We then show that depending on the location of the pole on the imaginary axis, the closed-loop system is asymptotically stable. We also consider the case where the output of the controller is corrupted by a disturbance and show that it may be possible to attenuate the effect of the disturbance at the output if we choose the controller transfer function appropriately. We also present some numerical simulation results which support this argument.Item Open Access Two-channel decentralized integral-action controller design(IEEE, 2002) Gündeş, A. N.; Özgüler, A. B.We propose a systematic controller design method that provides integral-action in linear time-invariant two-channel decentralized control systems. Each channel of the plant is single-input-single-output, with any number of poles at the origin but no other poles in the instability region. An explicit parametrization of all decentralized stabilizing controllers incorporating the integral-action requirement is provided for this special case of plants. The main result is a design methodology that constructs simple low-order controllers in the cascaded form of proportional-integral and first-order blocks.