| 1. |
- Bengtsson, Johan, et al.
(författare)
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Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference, ACC : June 30 - July 2, 2004, Boston Sheraton Hotel, Boston, Massachusetts. - 0743-1619. - 0780383354 ; 5, s. 4048-4053
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Konferensbidrag (refereegranskat)abstract
- The Homogeneous Charge Compression Ignition (HCCI) combustionconcept lacks direct ignition timing control, instead the autoignition depends on the operating condition. Since auto ignition of ahomogeneous mixture is very sensitive to operating conditions, a fastcombustion timing control is necessary for reliable operation. Hence,feedback is needed and the crank angle of 50% burnt (CA50) has provedto be a reliable feedback indicator of on-going combustion inpractice. CA50 or other methods for detecting on-going cylinderpressure used in the feedback control of a HCCI engine all rely onpressure sensors. This paper presents a newcandidate for control of HCCI engine by using the electronicconductive properties in the reaction zone. This phenomenon is calledion current. This paper perform combustion timing control based on ioncurrent and compare it with control based on pressure sensor. Thecombustion timing control is performed on cycle-to-cycle basis and the engine is a one-cylinder version of a heavy duty engine equipped with a port injection system using dual fuels.
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| 2. |
- Robertsson, Anders, et al.
(författare)
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Design and evaluation of load control in web-server systems
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference, ACC : June 30 - July 2, 2004, Boston Sheraton Hotel, Boston, Massachusetts. - 0743-1619. - 0780383354 ; , s. 1980-1985
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Konferensbidrag (refereegranskat)abstract
- Nonlinear discrete-time modeling of a Web server system is investigated. Server systems typically contain nonlinearities such as saturations and bounded queue lengths. The incoming traffic and service rates are best modeled by stochastic processes, well described and analyzed by queuing theory. Here, we develop and validate a control theoretic model of a general single server queue, a so-called G/G/1-system. Based on the nonlinear system model, design of admission controllers are presented and the closed loop stability is analyzed. The behavior of the server model is verified with respect to queue theoretic models. Finally, experimental evaluation is performed on an Apache Web server in a laboratory network. A traffic generator is used to represent client requests. The control of the Apache server has been re-written to implement our algorithms. We show that the control theoretic model aligns well with the experiments on the Web-server. Measurements in the laboratory setup show the robustness of the implemented controller, and how it corresponds to the results from the theoretical analysis and the simulations.
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| 3. |
- Sandberg, Henrik, et al.
(författare)
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Frequency-Domain Analysis of Linear Time-Periodic Systems
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference.. - 0743-1619. - 0780383354 ; 4, s. 3357-3362
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Konferensbidrag (refereegranskat)abstract
- In this paper we study how a system with a time-periodic impulse response may be expanded into a sum of modulated time-invariant systems. This allows us to define a linear frequency-response operator for periodic systems, called the harmonic transfer function (HTF). Similar frequency-response operators have been derived before for sampled-data systems and periodic finite-dimensional state-space systems. The HTF is an infinite-dimensional operator that captures the frequency coupling of a time-periodic system. The paper includes analysis of convergence of truncated HTFs. For this reason the concepts of input/output roll-off are developed and related to time-varying Markov parameters.
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| 4. |
- Abdelzaher, Tarek, et al.
(författare)
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Practical Application of Control Theory to Web Services
- 2004
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Ingår i: Proceedings of the American Control Conference. - 0743-1619. ; 3, s. 1992-1997
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Konferensbidrag (refereegranskat)abstract
- This tutorial describes experiences with applying a control theoretical approach to achieving performance guarantees in Web servers, with emphasis on delay control. A model for the server is formulated and translated into a control problem formulation. Limitations of the control theoretic approach are identified that arise due to system non-linearities and modeling inaccuracies. Solutions are proposed that augment the feedback control framework with elements of scheduling and queuing theory. The theoretical results and QoS control loops presented by the authors are implemented in a middleware package, called ControlWare, which provides the software mechanisms and interfaces that allow control of real server performance. Implementation and performance of ControlWare is described.
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| 5. |
- Almér, Stefan, et al.
(författare)
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Global stability analysis of DC-DC converters using sampled-data modeling
- 2004
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Ingår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6. - 0780383354 ; , s. 4549-4554
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Konferensbidrag (refereegranskat)abstract
- The paper presents stability analysis of a class of pulse-width modulated (PWM) systems which incorporates many different DC-DC converters. Two types of pulse-width modulation (digital and analog control) are considered. A procedure is developed for systematic search for Lyapunov functions. The state space is partitioned in such a way that stability is verified if a set of coupled Linear Matrix Inequalities (LMIs) is feasible. Global stability is considered as well as the computation of local regions of attraction.
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| 6. |
- Campbell, S.L., et al.
(författare)
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A numerical integrator for simulation of unstructured implicit models
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - 0743-1619. ; 6, s. 5647-5652
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Konferensbidrag (refereegranskat)abstract
- Object oriented modeling naturally leads to implicitly defined dynamical systems or, as they are also called, differential algebraic equations (DAEs). Most existing DAE integrators require the equations defining the dynamical system to have a special structure. Progress on the development of a new integrator for general unstructured DAEs is presented. The new integrator is called UCP. Computational tests are given to show that the new method can successfully integrate problems that other methods have trouble with.
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| 7. |
- Falkman, Petter, 1972, et al.
(författare)
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Combined Process Algebra and Petri Nets for Specification of Resource Booking Problems
- 2001
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Ingår i: American Control Conference. - 0743-1619. - 0780364953 ; 6, s. 4949-4955
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Konferensbidrag (refereegranskat)abstract
- A modeling framework for general routing and resource booking problems is presented. The task is to specify desired routes for individual objects (products, data packets, vehicles), which are to be served by a number of shared resources (machines, computers, communication links). A high level language is presented in order to simplify the specification of desired routes. This modeling language combines Petri nets and process algebra. Process operators are introduced for specification of sequences, alternative choices, arbitrary ordered sequences and process synchronization. Multiple as well as alternative resources are easily specified utilizing sets of resources. These sets and operators imply a very compact and efficient representation of complex routing specifications. In fact, the representation is suitable for verification and synthesis based on symbolic tools such as BDDs.
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| 8. |
- Freidovich, Leonid, 1973-, et al.
(författare)
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Comparison of logic-based switching control designs for a nonlinear system
- 2004
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Ingår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6. - 0780383354 ; , s. 1221-1222
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Konferensbidrag (refereegranskat)abstract
- We consider an example of a second order nonlinear system with large parametric uncertainties. The two parameters of the system are assumed to belong to a finite set. The goal is to guarantee (practical) convergence of the system output to a given constant reference signal. Feedback linearization-based candidate controllers with pole placement are designed for each possible set of parameters. After that, we consider the design of a high-level logic-based supervisor to organize switching between these candidate controllers. Three different approaches are used and compared.
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| 9. |
- Gattami, Ather, et al.
(författare)
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A frequency domain condition for stability of interconnected MIMO systems
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - 0780383354 ; , s. 3723-3728
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Konferensbidrag (refereegranskat)abstract
- Analysis of interconnected dynamical systems is considered. A framework for the analysis of stability of the interconnection is given. The results of Fax and Murray that studies the SISO-case for a constant interconnection matrix are generalized to the MIMO-case where arbitrary interconnection is allowed. The analysis shows the existence of a separation principle that is very useful in the sense of the simplicity for stability analysis. Stability could be checked graphically using a Nyquist-like criterion. The problem with time-delays and interconnection variation and robustness appear to be natural special cases of the general framework, and hence, simple stability criteria are derived easily
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| 10. |
- Gustafsson, Fredrik, et al.
(författare)
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Transmission Timing - A Control Approach to Distributed Uplink Scheduling in WCDMA
- 2004
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Ingår i: Proceedings of Reglermöte 2004. - Linköping : Linköping University Electronic Press. ; , s. 1667-1672 vol.2
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Centralized control and coordination of the connections in a wireless network is not possible in practice. To keep the delay from measure-ment instants to actuating the decisions, distributed control is required. This paper focuses on the uplink (from mobiles to base stations) and dis-cusses distributing the decision of when and when not to transmit data (distributed scheduling) to the mobiles. The scheme, uplink transmission timing, utilizes mobile transmitter power control feedback from the base station receiver to determine whether the channel is favorable or not compared to the average channel condition. Thereby, the battery consumption and disturbing power to other connections are reduced. The algorithm can be described as a feedback control system. Some transient behaviors are analyzed using systems theory, and supported by wireless network simulations of a system with a WCDMA (Wideband Code Division Multiple Access) radio interface as in most 3G systems.
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