| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Hansson, Anders, et al.
(författare)
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Stability Analysis of Nonlinear Systems using Frozen Stationary Linearization
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - 0780383354 ; , s. 424-428
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Konferensbidrag (refereegranskat)abstract
- This work discusses how to compute stability regions for nonlinear systems with slowly varying parameters using frozen stationary linearization. It is shown that larger stability regions can be obtained as compared to traditional approaches using recent stability results for linear parameter-varying systems.
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| 7. |
- Ianelli, Luigi, et al.
(författare)
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Dither shape in the averaging of switched systems
- 2004
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Ingår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6. - : IEEE. - 0780383354 ; , s. 5812-5817
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Konferensbidrag (refereegranskat)abstract
- It was shown by Zames and Shneydor that a high-frequency dither of a quite arbitrary shape can be used to smooth the effective nonlinear sector of Lipschitz continuous feedback systems. Here it is shown that also systems with discontinuous nonlinearities can be smoothed using dither signals, as long as the amplitude distribution function of the dither is Lipschitz continuous.
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| 8. |
- Iliev, Boyko, et al.
(författare)
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Minimum-time sliding mode control for second-order systems
- 2004
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Ingår i: Proceedings of the 2004 American control conference, 2004. - 0780383354 ; , s. 626-631
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Konferensbidrag (refereegranskat)abstract
- Our approach for near time-optimal control is based on Takagi-Sugeno fuzzy model of the maximum slope SMC sliding surface as an adaptive technique for tuning the current slope of the sliding surface to the maximum feasible slope depending on the current state of system. The stability conditions of this method are proved and respective measures about the feasible maximum slope are presented. Experimental results demonstrate the system behaviour.
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| 9. |
- Karlsson, Rickard, 1970-, et al.
(författare)
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Model-Based Statistical Tracking and Decision Making for Collision Avoidance Application
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - Linköping : Linköping University Electronic Press. - 0780383354 ; , s. 3435-3440
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Konferensbidrag (refereegranskat)abstract
- A growing research topic within the automotive industry is active safety systems. These systems aim at helping the driver avoid or mitigate the consequences of an accident. In this paper a collision mitigation system that performs late braking is discussed. The brake decision is based on estimates from tracking sensors. We use a Bayesian approach, implementing an extended Kalman filter (EKF) and a particle filter to solve the tracking problem. The two filters are compared for different sensor noise distributions in a Monte Carlo simulation study. In particular a bi-modal Gaussian distribution is proposed to model measurement noise for normal driving. For ideal test conditions the noise probability density is derived from experimental data. The brake decision is based on a statistical hypothesis test, where collision risk is measured in terms of required acceleration to avoid collision. The particle filter method handles this test easily. Since the test is not analytically solvable a stochastic integration is performed for the EKF method. Both systems perform well in the simulation study under the assumed sensor accuracy. The particle filter based algorithm is also implemented in a real-time testbed and fulfilled the on-line requirements.
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| 10. |
- Kuroiwa, Yohei, et al.
(författare)
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H-infinity control with preview and delay
- 2004
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Ingår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6. - 0780383354 ; , s. 4794-4799
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Konferensbidrag (refereegranskat)abstract
- An H-infinity control problem with simultaneous consideration of preview and delay is solved, where past signals and future signals are essential to describe. behaviors of the control system. Solvability conditions and complete controller parameterization are derived in the frequency domain within the scope of finite dimensional computations, that is, infinite dimensional aspects attributed to preview and delay are transformed to equivalent finite dimensional problems. The two-degree-of-freedom version is also considered.
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| 11. |
- Ljung, Lennart, 1946-
(författare)
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Integrated Frequency-Time Domain Tools for System Identification
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - 0780383354 ; , s. 5594-5599
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Konferensbidrag (refereegranskat)abstract
- The duality between time and frequency domain methods for linear systems is well known. It plays a crucial role for example in control systems design, and the domains are thought of complementing rather than competing. Quite recently, the full interplay and duality between the two domains have been clear also in system identification applications. In this contribution, this duality is discussed. The emphasis is on how it can be used to create a software environment for linear system identification that is as transparent as possible with respect to the data domains.
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| 12. |
- Ljung, Lennart, 1946-
(författare)
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State of the Art in Linear System Identification : Time and Frequency Domain Methods
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference. - 0780383354 ; , s. 650-660 vol.1
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Konferensbidrag (refereegranskat)abstract
- —Identication of time-invariant linear dynamic systems is a mature subject. In this contribution we focus on the interplay between methods that use time and frequency domain data, respectively. The frequency domain data could be either input/output Fourier transforms or frequency functions. We explain how these different kinds of data types are used to fit models, and how closely related the methods are. Of special interest is how transients (initial conditions and deviations from periodic signals) are handled. Direct estimation of time-continuous models is also discussed, as well as software aspects.
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| 13. |
- 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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| 14. |
- 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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