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You searched for subject:(diagramme de Nyquist). Showing records 1 – 2 of 2 total matches.

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EPFL

1. Kunze, Marc. Frequency-domain controller design by linear programming.

Degree: 2009, EPFL

In this thesis, a new framework to design controllers in the frequency domain is proposed. The method is based on the shaping of the open-loop transfer function in the Nyquist diagram. A line representing a lower approximation for the crossover frequency and a line representing a new linear robustness margin guaranteeing lower bounds for the classical robustness margins are defined and used as constraints. A linear programming approach is proposed to tune fixed-order linearly parameterized controllers for stable single-input single-output linear time-invariant plants. Two optimization problems are proposed and solved by linear programming. In the first one, the new robustness margin is maximized given a lower approximation of the crossover frequency, whereas in the second one, the closed-loop performance in terms of load disturbance rejection, output disturbance rejection and tracking is maximized subject to constraints on the new robustness margin. The method can directly consider multi-model systems. Moreover, this new framework can be used directly with frequency-domain data. Thus, it can also consider systems with frequency-domain uncertainties. Using the same framework, an extension of the method is proposed to tune fixed-order linearly parameterized gain-scheduled controllers for stable single-input single-output linear parameter varying plants. This method directly computes a linear parameter varying controller from a linear parameter varying model or from a set of frequency-domain data in different operating points and no interpolation is needed. In terms of closed-loop performance, this approach leads to extremely good results. However, the global stability cannot be guaranteed for fast parameter variations and should be analyzed a posteriori. Nevertheless, for certain classes of switched systems and linear parameter varying systems, it is also possible to guarantee the stability within the design framework. This can be accomplished by adding constraints based on the phase difference of the characteristic polynomials of the closed-loop systems. This frequency-domain methodology has been tested on numerous simulation examples and implemented experimentally on a high-precision double-axis positioning system. The results show the effectiveness and simplicity of the proposed methodologies. Advisors/Committee Members: Longchamp, Roland, Karimi, Alireza.

Subjects/Keywords: robust controller; gain-scheduled controller; linear programming; Nyquist diagram; frequency-domain data; quadratic stability; régulateur robuste; régulateur à gains programmés; programmation linéaire; diagramme de Nyquist; données fréquentielles; stabilité quadratique

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Kunze, M. (2009). Frequency-domain controller design by linear programming. (Thesis). EPFL. Retrieved from http://infoscience.epfl.ch/record/135606

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Kunze, Marc. “Frequency-domain controller design by linear programming.” 2009. Thesis, EPFL. Accessed November 17, 2017. http://infoscience.epfl.ch/record/135606.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Kunze, Marc. “Frequency-domain controller design by linear programming.” 2009. Web. 17 Nov 2017.

Vancouver:

Kunze M. Frequency-domain controller design by linear programming. [Internet] [Thesis]. EPFL; 2009. [cited 2017 Nov 17]. Available from: http://infoscience.epfl.ch/record/135606.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kunze M. Frequency-domain controller design by linear programming. [Thesis]. EPFL; 2009. Available from: http://infoscience.epfl.ch/record/135606

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


EPFL

2. Galdos Sanz de Galdeano, Gorka. Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models.

Degree: 2010, EPFL

This thesis proposes a new method to design fixed-order controllers in frequency domain using convex optimization. The method is based on the shaping of open-loop transfer function in the Nyquist diagram with infinity norm constraints on weighted closed-loop transfer functions. A parametric model is not required in this method as it directly uses frequency-domain data. Furthermore, systems with multi-model uncertainty as well as systems with frequency-domain uncertainties can be considered. Fixed-order linearly parameterized controllers are designed with the proposed method for single-input single-output (SISO) linear time-invariant plants. The shaping of the open-loop transfer function is performed based on the minimization of the difference with a desired open-loop transfer function under H∞ constraints on the closed-loop sensitivity functions. Since these constraints represent a nonconvex set in the space of the controller parameters, an inner convex approximation of this set is proposed using the desired open-loop transfer function. This approximation makes the problem of robust fixed-order controller design a convex optimization problem. An extension of the method is proposed to design two-degree-of-freedom (2DOF) controllers for SISO plants. The method is also extended to tune fixed-order linearly parameterized multivariable controllers for multiple-input multiple-output (MIMO) linear time-invariant plants where the stability of the closed-loop system is guaranteed using Gershgorin bands. The control problem is solved only using a finite number of frequency-domain samples. However, the stability and performance conditions between frequency samples are also verified if a frequency-domain uncertainty is considered. It is shown that this adds some conservatism to the solution. The proposed frequency-domain method has been tested on many simulation examples. The method has been applied to a flexible transmission benchmark for robust controller design giving extremely good results. Additionally, the method has also been implemented on an experimental high-precision double-axis positioning system. These results show the effectiveness of the proposed methods. Advisors/Committee Members: Longchamp, Roland, Karimi, Alireza.

Subjects/Keywords: robust controller; convex optimization; Nyquist diagram; spectral models; frequency-domain data; H-[infinity]; régulateur robuste; optimisation convexe; diagramme de Nyquist; modèles spectraux; données fréquentielles; H-[infini]

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Galdos Sanz de Galdeano, G. (2010). Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models. (Thesis). EPFL. Retrieved from http://infoscience.epfl.ch/record/149802

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Galdos Sanz de Galdeano, Gorka. “Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models.” 2010. Thesis, EPFL. Accessed November 17, 2017. http://infoscience.epfl.ch/record/149802.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Galdos Sanz de Galdeano, Gorka. “Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models.” 2010. Web. 17 Nov 2017.

Vancouver:

Galdos Sanz de Galdeano G. Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models. [Internet] [Thesis]. EPFL; 2010. [cited 2017 Nov 17]. Available from: http://infoscience.epfl.ch/record/149802.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Galdos Sanz de Galdeano G. Fixed-Order Robust Controller Design by Convex Optimization Using Spectral Models. [Thesis]. EPFL; 2010. Available from: http://infoscience.epfl.ch/record/149802

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.