| 1. |
- Lincoln, Bo, et al.
(författare)
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Efficient Pruning of Search Trees in LQR Control of Switched Linear Systems
- 2000
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Ingår i: Proceedings of the 39th IEEE Conference on Decision and Control, 2000.. - 0780366387 ; 2, s. 1828-1832
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper considers off-line optimization of a switching sequence fora given finite set of linear control systems and joint optimization ofcontrol laws. A linear quadratic full information criterion isoptimized and dynamic programming is used to find the optimalswitching sequence and control laws. The main result is a method for efficient pruning of the search tree to avoid combinatoric explosion.A method to prove optimality of a found candidate switch sequence and corresponding control laws is presented.
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| 2. |
- Lincoln, Bo, et al.
(författare)
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LQR Optimization of Linear System Switching
- 2002
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286. ; 47:10, s. 1701-1705
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers off-line optimization of a switching sequence fora given finite set of linear control systems, together with joint optimization ofcontrol laws. A linear quadratic full information criterion isoptimized and dynamic programming is used to find an optimalswitching sequence and control law. The main result is a method forefficient pruning of the search tree to avoid combinatoric explosion.A method to prove optimality of a found candidate switch sequence andcorresponding control laws is presented.
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| 3. |
- Lincoln, Bo, et al.
(författare)
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Optimal Control over Networks with Long Random Delays
- 2000
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Ingår i: Proceedings CD of the Fourteenth International Symposium on Mathematical Theory of Networks and Systems.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper studies the effects of stochastic time delays on automatic control systems which uses communication networks. We assume a linear process to be controlled and known delay probability distributions.The contribution of this paper is to extend the theory in(Nilsson 1998) to delays that may be longer than one sample period.Using a quadratic cost we find the optimal full-state-information controller. We also show that the standard Kalman filter is an optimal observer, and that the separation principle holds.
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| 4. |
- Cervin, Anton, et al.
(författare)
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How Does Control Timing Affect Performance?
- 2003
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Ingår i: Control Systems Magazine. - 0272-1708. ; 23:3, s. 16-30
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Tidskriftsartikel (refereegranskat)abstract
- The article presents two Matlab-based tools for analysis andsimulation of real-time control systems: Jitterbug andTrueTime.Jitterbug allows the user to compute aquadratic performance criterion for a linear control system undervarious timing conditions. The control system is described using anumber of continuous- and discrete-time linear systems. Astochastic timing model with random delays is used to describe theexecution of the system. The tool can also be used to investigateaperiodic controllers, multirate controllers, and jitter-compensatingcontrollers.TrueTime facilitates event-based co-simulation of amultitasking real-time kernel containing controller tasks and thecontinuous dynamics of controlled plants. The simulations capture thetrue, timely behavior of real-time controller tasks and communicationnetworks, and dynamic control and scheduling strategies can beevaluated from a control performance perspective. The controllers canbe implemented as Matlab functions, C functions, or ordinarydiscrete-time Simulink blocks.A number of examples that illustrate the use of the tools are given.
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| 5. |
- Cervin, Anton, et al.
(författare)
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Jitterbug and TrueTime: Analysis Tools for Real-Time Control Systems
- 2002
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Konferensbidrag (refereegranskat)abstract
- The paper presents two recently developed, Matlab-based analysis tools for realtime control systems. The first tool, called Jitterbug, is used to compute a performance criterion for a control loop under various timing conditions. The tool makes it easy to quickly judge how sensitive a controller is to implementation effects such as slow sampling, delays, jitter, etc. The second tool, called TrueTime, allows detailed co-simulation of process dynamics, control task execution, and network communication in a distributed real-time control system. Arbitrary scheduling policies may be used, and the tasks may be written in C code, Matlab code, or implemented as Simulink block diagrams.
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| 6. |
- Cervin, Anton, et al.
(författare)
-
Jitterbug - Reference Manual
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The manual describes the use of Jitterbug, a Matlab toolbox for analysis of real-time control performance. The tool facilitates the computation of a quadratic performance index for a linear control system under various timing conditions.
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| 7. |
- Cervin, Anton, et al.
(författare)
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The Jitter Margin and Its Application in the Design of Real-Time Control Systems
- 2004
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Ingår i: Proceedings of the 10th International Conference on Real-Time and Embedded Computing Systems and Applications.
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Konferensbidrag (refereegranskat)abstract
- Based on recent advances in control theory, we propose the notion of jitter margin for periodic control tasks. The jitter margin isdefined as a function of the amount of constant delay in the controlloop, and it describes how much additional time-varying delay can betolerated before the loop goes unstable. Combined with schedulingtheory, the jitter margin can be used to guarantee the stability andperformance of the controller in the target system. It can also beused as a tool for assigning meaningful deadlines to control tasks.We discuss the need for best-case response-time analysis in thiscontext, and propose a simple lower bound under EDF scheduling.Finally, a control-scheduling codesign procedure is given, whereperiods are assigned iteratively to yield the same relativeperformance degradation for each control task.
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| 8. |
- Engman, Cecilia, 1974, et al.
(författare)
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DNA adopts normal B-form upon incorporation of highly fluorescent DNA base analogue tC: NMR structure and UV-Vis spectroscopy characterization
- 2004
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 1362-4962 .- 0305-1048. ; 32:17, s. 5087-95
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the highly fluorescent tricyclic cytosine base analogue (tC) on duplex DNA conformation is investigated. The duplex properties are characterized by absorbance and circular dichroism (CD) for all combinations of neighbouring bases to tC, and an NMR structure is determined for one tC-containing sequence. For the oligonucleotides with one tC incorporated instead of cytosine, the melting temperature is increased on average by 2.7 degrees C above that for the unmodified ones. CD spectra are practically identical for modified and unmodified sequences, indicating an unperturbed B-DNA conformation. The NMR structure determination of the self-complementary sequence 5'-CTC(tC)ACGTGGAG shows a DNA conformation consistent with B-form for the whole duplex. The root-mean-square distance for the nucleotides of the eight central base pairs between the 10 structures with lowest CYANA target functions and a mean structure is 0.45 +/- 0.17 A. The NMR data confirm correct base pairing for tC by the observation of both intrastrand and interstrand imino proton NOEs. Altogether, this suggests that tC works well as a cytosine analogue, i.e. it is situated in the base stack, forming hydrogen bonds with G in the complementary strand, without distorting the DNA backbone conformation. This first example of an artificial, highly fluorescent DNA base that does not perturb the DNA conformation could have valuable applications for the study of the structure and dynamics of nucleic acid systems.
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| 9. |
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| 10. |
- Kao, ChungYao, et al.
(författare)
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Simple stability criteria for systems with time-varying delays
- 2004
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 40:8, s. 1429-1434
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the problem of checking stability of linear feedback systems with time-varying but bounded delays. Simple but powerful criteria of stability are presented for both continuous-time and discrete-time systems. Using these criteria, stability can be checked in a closed loop Bode plot. This makes it easy to design the system for robustness.
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