μ-sensitivities as an aid for robust identification

Identification for a model for robust control design is more complicated than for the standard linear system transfer function model-the structure of the uncertainty as well as bounds on its size must be determined. It is especially unclear as to which parts of the system should be better modeled to improve robust performance. This paper addresses this question through some new tools, the μ-sensitivities

Fast model predictive control for hydrogen outflow regulation in ethanol steam reformers

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In the recent years, the presence of alternative power sources, such as solar panels, wind farms, hydropumps and hydrogen-based devices, has significantly increased. The reasons of this trend are clear: contributing to a reduction of gas emissions and dependency on fossil fuels. Hydrogen-based devices are of particular interest due to their significant efficiency and reliability. Reforming technologies are among the most economic and efficient ways of producing hydrogen. In this paper we consider the regulation of hydrogen outflow in an ethanol steam reformer (ESR). In particular, a fast model predictive control approach based on a finite step response model of the process is proposed. Simulations performed using a more realistic non-linear model show the effectiveness of the proposed approach in driving the ESR to different operating conditions while fulfilling input and output constraints.Peer ReviewedPostprint (author's final draft

Probability-guaranteed set-membership state estimation for polynomially uncertain linear time-invariant systems

2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksConventional deterministic set-membership (SM) estimation is limited to unknown-but-bounded uncertainties. In order to exploit distributional information of probabilistic uncertainties, a probability-guaranteed SM state estimation approach is proposed for uncertain linear time-invariant systems. This approach takes into account polynomial dependence on probabilistic uncertain parameters as well as additive stochastic noises. The purpose is to compute, at each time instant, a bounded set that contains the actual state with a guaranteed probability. The proposed approach relies on the extended form of an observer representation over a sliding window. For the offline observer synthesis, a polynomial-chaos-based method is proposed to minimize the averaged H2 estimation performance with respect to probabilistic uncertain parameters. It explicitly accounts for the polynomial uncertainty structure, whilst most literature relies on conservative affine or polytopic overbounding. Online state estimation restructures the extended observer form, and constructs a Gaussian mixture model to approximate the state distribution. This enables computationally efficient ellipsoidal calculus to derive SM estimates with a predefined confidence level. The proposed approach preserves time invariance of the uncertain parameters and fully exploits the polynomial uncertainty structure, to achieve tighter SM bounds. This improvement is illustrated by a numerical example with a comparison to a deterministic zonotopic method.Peer ReviewedPostprint (author's final draft

LIONSIMBA: A Matlab Framework Based on a Finite Volume Model Suitable for Li-Ion Battery Design, Simulation, and Control

Consumer electronics, wearable and personal health devices, power networks, microgrids, and hybrid electric vehicles (HEVs) are some of the many applications of lithium-ion batteries. Their optimal design and management are important for safe and profitable operations. The use of accurate mathematical models can help in achieving the best performance. This article provides a detailed description of a finite volume method (FVM) for a pseudo-two-dimensional (P2D) Li-ion battery model suitable for the development of model-based advanced battery management systems. The objectives of this work are to provide: (i) a detailed description of the model formulation, (ii) a parametrizable Matlab framework for battery design, simulation, and control of Li-ion cells or battery packs, (iii) a validation of the proposed numerical implementation with respect to the COMSOL MultiPhysics commercial software and the Newman’s DUALFOIL code, and (iv) some demonstrative simulations involving thermal dynamics, a hybrid charge-discharge cycle emulating the throttle of an HEV, a model predictive control of state of charge, and a battery pack simulatio

Identification and Cross-Directional Control of Coating Processes: Theory and Experiments

Of special industrial interest is the cross-directional control of continuous coating processes, where the cross-direction refers to the direction perpendicular to the substrate movement. The objective of the controller is to maintain a uniform coating under unmeasured process disturbances based on assumptions relevant to coating processes found in industry. A model for control design is developed. This model is used to derive a model predictive controller with the objective of maintaining flat profiles of coating across the substrate by varying the liquid flows along the cross direction. Actuator constraints, measurement noise, and model uncertainty are investigated to determine which of these limit the achivable closed loop performance. From a knowledge of the effect of these limitations on performance we determine how the plant could be modified to improve the coating uniformity. The theory developed throughout the paper is rigorously verified though experiments on an industrial pilot plant

A Survey for H2O Megamasers III. Monitoring Water Vapor Masers in Active Galaxies

We present single-dish monitoring of the spectra of 13 extragalactic water megamasers taken over a period of 9 years and a single epoch of sensitive spectra for 7 others. Our data include the first K-band science observations taken with the new 100 m Green Bank Telescope (GBT). In the context of a circumnuclear, molecular disk model, our results suggest that either (a) the maser lines seen are systemic features subject to a much smaller acceleration than present in NGC 4258, presumably because the gas is farther from the nuclear black hole, or (b) we are detecting ``satellite'' lines for which the acceleration is in the plane of the sky. We also report a search for water vapor masers towards the nuclei of 58 highly inclined, nearby galaxies.Comment: accepted by ApJ

Screening plant designs and control structures for uncertain systems

Abstract--Screening tools are developed which provide nonconservative estimates of the achievable performance in the presence of general structured model uncertainty. These tools allow the rational selection among plant designs, or can be applied to provide recommedations on how to modify a plant design to improve the closed loop performance. Many of these tools are applicable to the pairing or partitioning of inputs and outputs of decentralized controllers. It is shown through examples that ignoring or improperly characterizing plant/model mismatch while selecting among plant designs can lead to erroneous results

Asymmetry in the Spectrum of High-Velocity H2O Maser Emission Features in Active Galactic Nuclei

We suggest a mechanism for the amplification of high-velocity water-vapor maser emission features from the central regions of active galactic nuclei. The model of an emitting accretion disk is considered. The high-velocity emission features originate in the right and left wings of the Keplerian disk. The hyperfine splitting of the signal levels leads to an asymmetry in the spectral profile of the water vapor maser line at a frequency of 22.235 GHz. We show that the gain profile asymmetry must lead to an enhanced brightness of the blueshifted high-velocity emission features compared to the redshifted ones. Such a situation is observed in the source UGC 3789.Comment: 11 pages 3 figure

Ramp-rate effects in transient enhanced diffusion and dopant activation

Use of high ramp rates ͑Ͼ400°C/s͒ in rapid thermal annealing after ion implantation leads to experimentally observed improvements in junction depth and the reverse narrow-channel effect. However, a straightforward explanation for this effect has been lacking. Via modeling, we find that increasing the heating rate permits clusters with dissociation energies lower than the maximum of 3.5-3.7 eV to survive to higher temperatures. This improved survival delays the increase in Si interstitial concentrations near the top of an annealing spike, which decreases the profile spreading

Discovery of Water Maser Emission in Five AGN and a Possible Correlation Between Water Maser and Nuclear 2-10 keV Luminosities

We report the discovery of water maser emission in five active galactic nuclei (AGN) with the 100-m Green Bank Telescope (GBT). The positions of the newly discovered masers, measured with the VLA, are consistent with the optical positions of the host nuclei to within 1 sigma (0.3 arcsec radio and 1.3 arcsec optical) and most likely mark the locations of the embedded central engines. The spectra of three sources, 2MASX J08362280+3327383, NGC 6264, and UGC 09618 NED02, display the characteristic spectral signature of emission from an edge-on accretion disk with maximum orbital velocity of ~700, ~800, and ~1300 km s^-1, respectively. We also present a GBT spectrum of a previously known source MRK 0034 and interpret the narrow Doppler components reported here as indirect evidence that the emission originates in an edge-on accretion disk with orbital velocity of ~500 km s^-1. We obtained a detection rate of 12 percent (5 out of 41) among Seyfert 2 and LINER systems with 10000 km s^-1 < v_sys < 15000 km s^-1. For the 30 nuclear water masers with available hard X-ray data, we report a possible relationship between unabsorbed X-ray luminosity (2-10 keV) and total isotropic water maser luminosity, L_{2-10} proportional to L_{H2O}^{0.5+-0.1}, consistent with the model proposed by Neufeld and Maloney in which X-ray irradiation and heating of molecular accretion disk gas by the central engine excites the maser emission.Comment: 16 pages, 5 tables, 3 figures, to appear in the November 10, 2006, v651n2 issue of the Astrophysical Journa