2,044 research outputs found
Recursive model-based virtual in-cylinder pressure sensing for internal combustion engines
Das Drucksignal im Zylinder ist ein sehr nützlicher Indikator für moderne Hochleistungs-Verbrennungsmotoren. Allerdings sind direkte Messungen des Zylinderdrucks unpraktisch, da die
Bedingungen in den Zylindern von Verbrennungsmotoren ungünstig sind sowie die Installation von
Zylinderdrucksensoren schwierig ist. Zahlreiche Methoden (z. B. virtuelle Messmethoden) wurden
untersucht, um den Druck im Zylinder aus extern gemessenen Signalen zu rekonstruieren, z. B. aus dem
Schwingungssignal des Motorblocks und der Winkelgeschwindigkeit der Kurbelwelle.
Viele der vorgeschlagenen Methoden haben vielversprechende Ergebnisse erbracht. Allerdings gibt es
immer noch einige Nachteile wie z.B. eine schlecht konditionierte Inversion oder die Notwendigkeit
einer großen Datenmenge, um ein inverses Modell durch künstliche neuronale Netze abzuleiten. In
dieser Arbeit werden unter Berücksichtigung der aktuellen Zylinderdruck-Rekonstruktionsprobleme
lineare modellbasierte, nichtlineare modellbasierte und inverse modellbasierte ZylinderdruckRekonstruktionsmethoden vorgeschlagen, die eine Alternative zu den bestehenden ZylinderdruckRekonstruktionsmethoden darstellen. Alle vorgeschlagenen Methoden basieren auf der rekursiven
Zustandsrekonstruktion unter Verwendung des Kalman-Filters oder eines Beobachters, so dass eine
direkte Inversion vermieden werden kann. Darüber hinaus werden alle vorgeschlagenen Methoden
rekursiv im Zeitbereich durchgeführt, so dass sie für Echtzeit-Implementierungen geeignet sind und auch
keine Probleme im Frequenzbereich, wie z. B. Leckeffekte, aufweisen. Darüber hinaus handelt es sich bei
allen vorgeschlagenen Methoden um modellbasierte Methoden, und die Modelle werden mit Hilfe von
Systemidentifikationstechniken unter Ausschluss künstlicher neuronaler Netze identifiziert, so dass keine
großen Datenmengen erforderlich sind.
Für die Systemidentifikation und die Validierung der vorgeschlagenen Methoden wurden Datensätze
eines Vierzylinder-Dieselmotors unter verschiedenen Motorbetriebsbedingungen erfasst. Die erfassten
Daten reichen von der Betriebsbedingung 1200 U/min, 60 Nm bis zur Betriebsbedingung 3000 U/min,
180 Nm. Die rekonstruierten Zylinderdruckkurven und die beiden Verbrennungsmetriken
Zylinderdruckspitze und Spitzenort wurden zur Validierung der vorgeschlagenen
Zylinderdruckrekonstruktionsmethoden verwendet. Die Ergebnisse der Rekonstruktion des
Zylinderdrucks, die mit den in dieser Arbeit vorgeschlagenen Methoden erzielt wurden, zeigen, dass alle
vorgeschlagenen Methoden sowohl unter stationären als auch unter nicht-stationären
Betriebsbedingungen verwendet werden können und dass die Ergebnisse der Rekonstruktion des
Zylinderdrucks mit den Ergebnissen der bestehenden Methoden zur Rekonstruktion des Zylinderdrucks
vergleichbar sind. Darüber hinaus kann festgestellt werden, dass es mehrere Faktoren gibt, die die
Genauigkeit der Druckrekonstruktion beeinflussen, wie z.B. die Qualität der identifizierten Modelle, des
Verzögerungsblocks und der momentanen Motordrehzahl.The in-cylinder pressure signal is a very useful indicator for modern high-performance internal combustion
engines. Unfortunately, direct measurements of the in-cylinder pressure are impractical because installing
cylinder pressure sensors is difficult and conditions in internal combustion engine cylinders are adverse.
Numerous methods (such as virtual sensing methods) have been investigated to reconstruct the incylinder pressure from externally measured signals, such as the engine block structural vibration signal
and the engine crank angular speed.
Many of the proposed methodologies have shown promising results. However, there still exist some
drawbacks, such as ill-conditioned inversion and the need of large number of data to derive an inverse
model by artificial neural networks. In this thesis, considering current in-cylinder pressure reconstruction
problems, linear model-based, nonlinear model-based, and inverse model-based in-cylinder pressure
reconstruction methods, which are alternative to existing cylinder pressure reconstruction methods, are
proposed. All the proposed methods are based on the recursive state reconstruction by using the Kalman
filter or observer such that a direct inversion can be avoided. Moreover, all the proposed methods are
recursively conducted in time domain, so they are suitable for real-time implementations and they also do
not have frequency-domain problems such as spectral leakage. Additionally, all the proposed methods are
model-based methods, and the models are identified by using system identification techniques excluding
artificial neural networks, so the need of a large number of data is not necessary.
For system identification and the validation of the proposed methods, the datasets under different engine
operating conditions were acquired from a four-cylinder diesel engine. Data acquired is from the operating
condition 1200 rpm, 60 Nm to the operating condition 3000 rpm, 180 Nm. The reconstructed cylinder
pressure curves and two combustion metrics cylinder pressure peak and peak location were used for
validating the proposed cylinder pressure reconstruction methods. According to the cylinder pressure
reconstruction results obtained based on using the proposed methods in this thesis, it can be found that
all the proposed methods can be used under both stationary and non-stationary operating conditions, and
the reconstructed cylinder pressure results are comparable among existing cylinder pressure
reconstruction methods. Furthermore, it can also be found that there exist several factors affecting the
pressure reconstruction accuracy, such as the quality of the identified models, delay block and
instantaneous engine cycle frequency
SYSTEM IDENTIFICATION AND MODEL PREDICTIVE CONTROL FOR INTERACTING SERIES PROCESS WITH NONLINEAR DYNAMICS
This thesis discusses the empirical modeling using system identification technique and the implementation of a linear model predictive control with focus on interacting series processes. In general, a structure involving a series of systems occurs often in process plants that include processing sequences such as feed heat exchanger, chemical reactor, product cooling, and product separation. The study is carried out by experimental works using the gaseous pilot plant as the process. The gaseous pilot plant exhibits the typical dynamic of an interacting series process, where the strong interaction between upstream and downstream properties occurs in both ways.
The subspace system identification method is used to estimate the linear model parameters. The developed model is designed to be robust against plant nonlinearities. The plant dynamics is first derived from mass and momentum balances of an ideal gas. To provide good estimations, two kinds of input signals are considered, and three methods are taken into account to determine the model order. Two model structures are examined. The model validation is conducted in open-loop and in closed-loop control system.
Real-time implementation of a linear model predictive control is also studied. Rapid prototyping of such controller is developed using the available equipments and software tools. The study includes the tuning of the controller in a heuristic way and the strategy to combine two kinds of control algorithm in the control system.
A simple set of guidelines for tuning the model predictive controller is proposed. Several important issues in the identification process and real-time implementation of model predictive control algorithm are also discussed. The proposed method has been successfully demonstrated on a pilot plant and a number of key results obtained in the development process are presented
On-The-Fly Processing of continuous high-dimensional data streams
[EN] A novel method and software system for rational handling of time series of multi-channel measurements is presented. This quantitative learning tool, the On-The-Fly Processing (OTFP), develops reduced-rank bilinear subspace models that summarise massive streams of multivariate responses, capturing the evolving covariation patterns among the many input variables over time and space. Thereby, a considerable data compression can be achieved without significant loss of useful systematic information.
The underlying proprietary OTFP methodology is relatively fast and simple it is linear/bilinear and does not require a lot of raw data or huge cross-correlation matrices to be kept in memory. Unlike conventional compression methods, the approach allows the high-dimensional data stream to be graphically interpreted and quantitatively utilised in its compressed state. Unlike adaptive moving-window methods, it allows all past and recent time points to be reconstructed and displayed simultaneously.
This new approach is applied to four different case-studies: (i) multi-channel Vis-NIR spectroscopy of the Belousov Zhabotinsky reaction, a complex, ill understood chemical process; (ii) quality control of oranges by hyperspectral imaging; (iii) environmental monitoring by airborne hyperspectral imaging; (iv) multi-sensor process analysis in the petrochemical industry. These examples demonstrate that the OTFP can automatically develop high-fidelity subspace data models, which simplify the storage/transmission and the interpretation of more or less continuous time series of high-dimensional measurements to the extent there are covariations among the measured variables.This research work was partially supported by the Spanish Ministry of Economy and Competitiveness under the project DPI2014-55276-C5-1R, Shell Global Solutions International B.V. (Amsterdam, The Netherlands), Idletechs AS (Trondheim, Norway), the Norwegian Research Council (Grant 223254) through the Centre of Autonomous Marine Operations and Systems (AMOS) at the Norwegian University of Science and Technology (Trondheim, Norway) and the Ministry of Education, Youth and Sports of the Czech Republic (CENAKVA project CZ.1.05/2.1.00/01.0024 and CENAKVA II project L01205 under the NPU I program). The authors want to acknowledge Prof. Bjorn Alsberg for providing the Vis-NIR equipment and the Laboratorio de Sistemas e Tecnologia Subaquatica of the University of Porto, the Hydrographic Institute of the Portuguese Navy and the University of the Azores for carrying out the REP15 exercise, during which the hyperspectral push broom image was collected.Vitale, R.; Zhyrova, A.; Fortuna, JF.; De Noord, OE.; Ferrer, A.; Martens, H. (2017). On-The-Fly Processing of continuous high-dimensional data streams. Chemometrics and Intelligent Laboratory Systems. 161:118-129. doi:10.1016/j.chemolab.2016.11.003S11812916
Challenges of Big Data Analysis
Big Data bring new opportunities to modern society and challenges to data
scientists. On one hand, Big Data hold great promises for discovering subtle
population patterns and heterogeneities that are not possible with small-scale
data. On the other hand, the massive sample size and high dimensionality of Big
Data introduce unique computational and statistical challenges, including
scalability and storage bottleneck, noise accumulation, spurious correlation,
incidental endogeneity, and measurement errors. These challenges are
distinguished and require new computational and statistical paradigm. This
article give overviews on the salient features of Big Data and how these
features impact on paradigm change on statistical and computational methods as
well as computing architectures. We also provide various new perspectives on
the Big Data analysis and computation. In particular, we emphasis on the
viability of the sparsest solution in high-confidence set and point out that
exogeneous assumptions in most statistical methods for Big Data can not be
validated due to incidental endogeneity. They can lead to wrong statistical
inferences and consequently wrong scientific conclusions
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