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Assessment of the control performance of fixed structure control for a process with limitations
2010 (English)Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

In this thesis, the assessment of performance of multivariable systems (MIMO) that have time delays is presented. A time delay is defined as the difference of time between a sent signal and the received one. Therefore, time delays are in any dynamic system.A time delay imposes a serious limitation on achievable control performance. The assessment of systems that contain time delays are complex, since a delay is represented mathematically as a irrational function. It can not be analysed with classical methods, so approximations to rational functions are needed. The problem is that this approximations are not accurate for systems with high time delays. Moreover, the multivariable systems have interactions between its elements, which make them more difficult to analyse. Hence, for assess the performance of a multivariable system with time delays, under the frequency domain, is necessary to apply special mathematical techniques. Gershgorin circles will be used, for measuring the interactions between the elements of a system. This circles are located on the Nyquist diagram for all the frequencies and the radius is given by the amplitude of the off-diagonal elements at each frequency. It has been aplied a measure method (ultimate point) and it has been developed other (modulus margin) for finding out what is the maximum delay that the system can bear before getting instable. It can be also useful for finding out what is the bandwidth of the system with delays. Thus, it can be seen how the bandwidth is reduced because of the presence of time delays. As a result, the delays that are in the off diagonal will not have influence on the system performance, since the Gershgorin Circles depend on the magnitude of those off diagonal elements and for the time delays is unitary for all frequencies. From this point of view, the delays are only important if they are in the diagonal elements.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Performance assessment, Gershgorin bands, time delays
Keyword [sv]
URN: urn:nbn:se:ltu:diva-49730ISRN: LTU-PB-EX--10/045--SELocal ID: 70b60b91-3512-4b55-b45a-802014bd389fOAI: diva2:1023076
Subject / course
Student thesis, at least 15 credits
Educational program
Electrical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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