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Order Reduction (order + reduction)

Distribution by Scientific Domains

Engineering	90%

Kinds of Order Reduction

model order reduction

Selected Abstracts

Nonlinear Model Order Reduction in Nanoelectronics: Combination of POD and TPWL

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008
T. Bechtold
In this paper we demonstrate model order reduction of a nonlinear academic model of an inverter chain. Two reduction methods, which are suitable for nonlinear differential algebraic equation systems are combined, the trajectory piecewise linear approach and the proper orthogonal decomposition. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Reduced-order robust adaptive control design of uncertain SISO linear systems

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2008
Qingrong Zhao
Abstract In this paper, a stability and robustness preserving adaptive controller order-reduction method is developed for a class of uncertain linear systems affected by system and measurement noises. In this method, we immediately start the integrator backstepping procedure of the controller design without first stabilizing a filtered dynamics of the output. This relieves us from generating the reference trajectory for the filtered dynamics of the output and thus reducing the controller order by n, n being the dimension of the system state. The stability of the filtered dynamics is indirectly proved via an existing state signal. The trade-off for this order reduction is that the worst-case estimate for the expanded state vector has to be chosen as a suboptimal choice rather than the optimal choice. It is shown that the resulting reduced-order adaptive controller preserves the stability and robustness properties of the full-order adaptive controller in disturbance attenuation, boundedness of closed-loop signals, and output tracking. The proposed order-reduction scheme is also applied to a class of single-input single-output linear systems with partly measured disturbances. Two examples are presented to illustrate the performance of the reduced-order controller in this paper. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Combining Krylov subspace methods and identification-based methods for model order reduction

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2007
P. J. Heres
Abstract Many different techniques to reduce the dimensions of a model have been proposed in the near past. Krylov subspace methods are relatively cheap, but generate non-optimal models. In this paper a combination of Krylov subspace methods and orthonormal vector fitting (OVF) is proposed. In that way a compact model for a large model can be generated. In the first step, a Krylov subspace method reduces the large model to a model of medium size, then a compact model is derived with OVF as a second step. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Krylov model order reduction of finite element approximations of electromagnetic devices with frequency-dependent material properties

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2007
Hong Wu
Abstract A methodology is presented for the Krylov subspace-based model order reduction of finite element models of electromagnetic structures with material properties and impedance boundary conditions exhibiting arbitrary frequency dependence. The proposed methodology is a generalization of an equation-preserving Krylov model order reduction scheme for methodology for second-order, linear dynamical systems. The emphasis of this paper is on the application of this method to the broadband model order reduction of planar circuits including lossy strips of arbitrary thickness and lossy reference planes. In particular, it is shown that the proposed model order reduction methodology provides for the accurately modelling of the impact of the frequency dependence of the internal impedance per unit length of the thick lossy strip on the electromagnetic response of the stripline structure over a very broad, multi-GHz frequency band, extending all the way down to frequencies in the DC neighbourhood. In addition, the application of the proposed methodology to the broadband modelling of electromagnetic coupling between strips on either side of a lossy ground plane is demonstrated. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Model order reduction of linear and nonlinear 3D thermal finite-element description of microwave devices for circuit analysis

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2005
Raphaël Sommet
Abstract Electrothermal models of power devices are necessary for the accurate analysis of their performances. For this reason, this article deals with a methodology to obtain an electrothermal model based on a reduced model of a 3D thermal finite-element (FE) description for its thermal part and on pulsed electrical measurements for its electrical part. The reduced thermal model is based on the Ritz vector approach, which ensures a steady-state solution in every case. An equivalent SPICE subcircuit implementation for circuit simulation is proposed and discussed. An extension of the method to a nonlinear reduced model based on the Kirchoff transformation is also proposed. The complete models have been successfully implemented in circuit simulators for several HBT or PHEMT device structures. Many results concerning devices and circuits are presented, including simulation of both the static and dynamic collector-current collapse in HBTs due to the thermal phenomenon. Moreover, the results in terms of the circuit for an X-band high-power amplifier are also presented. As for the nonlinear approach, results concerning an homogeneous structure is given. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Plant zero structure and further order reduction of a singular H, controller

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2002
Takao Watanabe
Abstract A new class of reduced-order controllers is obtained for the H, problem. The reduced-order controller does not compromise the performance attained by the full-order controller. Algorithms for deriving reduced-order H, controllers are presented in both continuous and discrete time. The reduction in order is related to unstable transmission zeros of the subsystem from disturbance inputs to measurement outputs. In the case where the subsystem has no infinite zeros, the resulting order of the H, controller is lower than that of the existing reduced-order H, controller designs which are based on reduced-order observer design. Furthermore, the mechanism of the controller order reduction is analysed on the basis of the two-Riccati equation approach. The structure of the reduced-order H, controller is investigated. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Optimal operation of GaN thin film epitaxy employing control vector parametrization

AICHE JOURNAL, Issue 4 2006
Amit Varshney
Abstract An approach that links nonlinear model reduction techniques with control vector parametrization-based schemes is presented, to efficiently solve dynamic constraint optimization problems arising in the context of spatially-distributed processes governed by highly-dissipative nonlinear partial-differential equations (PDEs), utilizing standard nonlinear programming techniques. The method of weighted residuals with empirical eigenfunctions (obtained via Karhunen-Loève expansion) as basis functions is employed for spatial discretization together with control vector parametrization formulation for temporal discretization. The stimulus for the earlier approach is provided by the presence of low order dominant dynamics in the case of highly dissipative parabolic PDEs. Spatial discretization based on these few dominant modes (which are elegantly captured by empirical eigenfunctions) takes into account the actual spatiotemporal behavior of the PDE which cannot be captured using finite difference or finite element techniques with a small number of discretization points/elements. The proposed approach is used to compute the optimal operating profile of a metallorganic vapor-phase epitaxy process for the production of GaN thin films, with the objective to minimize the spatial nonuniformity of the deposited film across the substrate surface by adequately manipulating the spatiotemporal concentration profiles of Ga and N precursors at the reactor inlet. It is demonstrated that the reduced order optimization problem thus formulated using the proposed approach for nonlinear order reduction results in considerable savings of computational resources and is simultaneously accurate. It is demonstrated that by optimally changing the precursor concentration across the reactor inlet it is possible to reduce the thickness nonuniformity of the deposited film from a nominal 33% to 3.1%. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]