Optimization of System Identification for Multi-Rail DC-DC Power Converters

Ph. D. Thesis.There have been many recursive algorithms investigated and introduced in real time parameter estimation of Switch Mode Power Converters (SMPCs) to improve estimation performance in terms of faster convergence speed, lower computational cost and higher estimation accuracy. These algorithms, including Dichotomous Coordinate Descent (DCD) - Recursive Least Square (RLS), Kalman Filter (KF) and Fast Affine Projection (FAP), etc., are commonly applied for performance comparison of system identification of single-rail power converters. When they need to be used in multi-rail architectures with a single centralized controller, the computational burden on the processor becomes significant. Typically, the computational effort is directly proportional to the number of converters/rails. This thesis presents an iterative decimation approach to significantly alleviate the computational burden of centralized controllers applying real-time recursive system identification algorithms in multirail power converters. The proposed approach uses a flexible and adjustable update rate rather than a fixed rate, as opposed to conventional adaptive filters. In addition, the step size/forgetting factors are varied, as well, corresponding to different iteration stages. As a result, reduced computational burden and faster model update can be achieved. Recursive algorithms, such as Recursive Least Square (RLS), Affine Projection (AP) and Kalman Filter (KF), contain two important updates per iteration cycle. Covariance Matrix Approximation (CMA) update and the Gradient Vector (GV) update. Usually, the computational effort of updating Covariance Matrix Approximation (CMA) requires greater computational effort than that of updating Gradient Vector (GV). Therefore, in circumstances where the sampled data in the regressor does not experience significant fluctuations, re-using the Covariance Matrix Approximation (CMA), calculated from the last iteration cycle for the current update can result in computational cost savings for real- time system identification. In this thesis, both iteration rate adjustment and Covariance Matrix Approximation (CMA) re-cycling are combined and applied to simultaneously identify the power converter model in a three-rail power conversion architecture. Besides, in multi-rail architectures, due to the high likelihood of the at-the-same-time need for real time system identification of more than one rail, it is necessary to prioritize each rail to guarantee rails with higher priority being identified first and avoid jam. In the thesis, a workflow, which comprises sequencing rails and allocating system identification task into selected rails, was proposed. The multi-respect workflow, featured of being dynamic, selectively pre-emptive, cost saving, is able to flexibly change ranks of each rail based on the application importance of rails and the severity of abrupt changes that rails are suffering to optimize waiting time and make-span of rails with higher priorities

Optimized state feedback regulation of 3DOF helicopter system via extremum seeking

In this paper, an optimized state feedback regulation of a 3 degree of freedom (DOF) helicopter is designed via extremum seeking (ES) technique. Multi-parameter ES is applied to optimize the tracking performance via tuning State Vector Feedback with Integration of the Control Error (SVFBICE). Discrete multivariable version of ES is developed to minimize a cost function that measures the performance of the controller. The cost function is a function of the error between the actual and desired axis positions. The controller parameters are updated online as the optimization takes place. This method significantly decreases the time in obtaining optimal controller parameters. Simulations were conducted for the online optimization under both fixed and varying operating conditions. The results demonstrate the usefulness of using ES for preserving the maximum attainable performance

Reactor design, reaction engineering and cocatalyst development for photocatalytic water splitting half-reactions

Global warming concerns have brought energy conversion into the spotlight. The conversion of renewable energy into chemical energy carriers has required keen inventiveness of the scientific community to find feasible solutions within today´s global economy. The success of such solutions requires collective efforts of multiple stakeholders, but from a purely technical perspective, this translates to the search for materials that can readily split water using a renewable energy input. For example, by using the right combination of light absorbing and catalytically active materials — or simply photocatalysts — that can simultaneously harvest sunlight and catalyze water splitting (aka artificial photosynthesis). An efficient water splitting photocatalyst aims to transform as much power of the solar spectrum as possible into chemical energy stored in the form of hydrogen and oxygen. The efficiency of this conversion is the result of multiple steps ultimately related to the sequence of light absorption, charge separation and transport, and electron transfer reactions. A photocatalyst is a semiconductor material with properties (i.e., optical band gap and crystallinity) that facilitate that sequence. Photocatalyst optimization is the process of tweaking the rate of those multiple steps (i.e., through material properties) such that the losses along the sequence are minimized. This work focuses on the optimization of the photocatalytic performance of TiO2, WO3, and covalent organic frameworks (COFs). Energy conversion efficiencies using these, and state of the art photocatalysts remain far from the target set for commercial feasibility. However, since the first water splitting experience on TiO2, various materials have been also demonstrated promising photocatalytic properties for water splitting half reactions, like WO3 and COFs. While both WO3 and TiO2 (band gap ~ 2.75 and 3.2 eV, respectively) are n-type semiconductors with valence bands that provide enough thermodynamic driving force for the oxygen evolution reaction (OER), WO3 allows additional harvesting of the visible solar spectrum. COFs are crystalline organic semiconductors that can be synthesized from earth abundant elements which have demonstrated the photocatalytic hydrogen evolution reaction (HER). Differently to the existing myriad of inorganic HER photocatalysts, the superior chemical tunability of COFs allows rational design and almost unlimited options for the tailoring of their photocatalytic properties. Multiple strategies can be found in the literature to optimize the photocatalytic performance of TiO2, WO3 and COFs by the modification of the light harvester material properties. The workflow presented herein differs from those, because it zooms to other aspects that are equally crucial to explain photocatalyst performance but that are typically less explored by material researchers. These are the increase of material photocatalytic performance upon decoration with cocatalysts (HER or OER electrocatalyst), and the intricate interplay between that performance and the nanoparticulate suspensions' multiphysics (optics, transport phenomena, and colloidal suspension stabilization). The latter rationalizes the photoreactor design presented along this work, which simplifies persisting instrumental problems and uncertainties of the artificial photosynthesis field related to reaction modeling, and the accuracy, reproducibility, and sensitivity of the quantification of photocatalyst performance. Commercial TiO2 (P25) is a standardized photocatalyst with the potential to benchmark photocatalytic OER rates among different laboratories, but it requires the addition of an OER catalyst to overcome water oxidation kinetic limitations. In this work a RuOx cocatalyst is developed in-situ on P25 for such purpose. With the instrumentals developed for sensitive O2 detection, the P25@RuO2 benchmark is optimized in terms of activity and reproducibility (at simulated sunlight, AM1.5G) and its resulting external (0.2%) and internal photonic efficiency (16%) is presented. Along with the establishment of this OER benchmark, this work also drafts good practices for reporting OER rates (i.e., adventitious O2 control), and innovative photoreactor engineering and optical modelling for the disentangling of the multiple factors determining photocatalysis physics. Using the same instrumentals for OER detection and a more elaborated cocatalyst tuning approach, a novel 2D RuOx electrocatalyst (ruthenium oxide nanosheet, RONS) is added to WO3 nanoparticles to enhance photocatalytic OER rates. First, the tuning of a top-down method to produce size-controlled unilamellar RONS is developed. Then, the composites resulting from RONS impregnation on WO3 are compared to conventionally impregnated RuO2 nanoparticles (RONP) on WO3, the former displaying a 5-fold increase in photonic efficiency. These results are explained from the electrocatalytic properties at the RONS edges, and the optical properties of the resulting 2D/0D morphology of the RONS/WO3 that decreases the optical losses due to parasitic cocatalyst light absorption. COFs have enormous potential as photocatalysts by design. In this work the photocatalytic performance of a TpDTz COF is analyzed in terms of its interaction with a molecular HER cocatalyst (Ni-ME) and reaction modeling. The TpDTz COF/Ni-ME system, which is one of the few existing COF-molecular cocatalyst known to date that can produce hydrogen, shows relatively high HER photocatalytic activity (~1 mmol h-1 g-1, AM1.5G) compared to other organic visible light responsive semiconductor benchmarks (i.e., like g-C3N4) and it operates in aqueous suspension (containing triethanolamine as electron donor). The TpDTz COF/Ni-ME surprisingly overperforms Pt modified TpDTz COF. Nonetheless, the COFs' charge transport properties are not well understood and most likely short-ranged. This blurs the experimental access to COFs' photocatalytic performance bottlenecks, including the prominent case of the TpDTz COF/Ni-ME system. Regardless of such difficulties, this work deepens the HER reaction understanding of the TpDTz COF/Ni-ME by analyzing dynamic HER reaction trends detected using the aforesaid photoreactor designs and instrumentals. From the modeled HER cycle kinetics and rapid dark step, the HER rate limiting step of the TpDTz COF/Ni-ME is placed at the electron transfer to the resting Ni-ME state. These HER mechanisms on COFs are experimentally challenging to access and are herein partially accessed in-situ from a reaction engineering and modelling perspective. On the whole, this work is the culmination of a multidisciplinary effort to find new opportunities to understand and optimize materials used for energy conversion processes, ranging from fundamental material research, solid-state and optics physics, applied catalysis, to reactor engineering

Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes

The book documents 25 papers collected from the Special Issue “Advances in Condition Monitoring, Optimization and Control for Complex Industrial Processes”, highlighting recent research trends in complex industrial processes. The book aims to stimulate the research field and be of benefit to readers from both academic institutes and industrial sectors

Advanced 1,2,3-triazolate-based coordination compounds: from carbonic anhydrase mimics, molecular building blocks, and catalyst supports to electrically conducting spin-crossover MOFs

Kuratowski complexes and related metal-organic frameworks (MOF), especially of the MFU-4-type, built from 1,2,3-triazolate-based ligands gained increasing interest in the last years due to their variable side ligands and metal sites. Such materials and their post-synthetic modifications have shown an outstanding potential for applications such as adsorption, capture, separation and kinetic trapping of gases, drug delivery, atmospheric water harvesting, sensing, H2/D2 quantum sieving, investigation of fundamental magnetic phenomena, and in particular catalysis. In this respect, MFU-4-type MOF catalysts were shown to outperform other heterogeneous catalysts for the dimerization and polymerization of olefins with some applications already advancing toward commercial applicability. This thesis mainly aims to extend the functionality of 1,2,3-triazolate-based coordination materials via advanced linker designs, novel framework assembly strategies, and post-synthetic modifications, as well as through a better understanding of the underlying material properties. During this project, several new organic and complex building blocks, as well as advanced framework structures were prepared and characterized. Furthermore, additional emphasis was directed to the investigation and interpretation of resulting physical phenomena like phase transitions, magnetism, and electrical conductivity. The Zn-MFU-4l ([Zn5IICl4(BTDD)3]; H2-BTDD = bis(1H-1,2,3-triazolo[4,5-b][4′,5′-i])dibenzo[1,4]dioxin) and Co-MFU-4l ([Zn1.3IICo3.7IICl4(BTDD)3]) metal-organic frameworks were prepared according to the literature procedures and modified by a post-synthetic side ligand exchange of the chloride anions, which led to MFU-4-type structures featuring organometallic metal-carbon bonds. Overall, five new Zn-MFU-4l structures of the general formula [Zn5IILxCl4–x(BTDD)3] (4 ≥ x > 3; L = methanido, ethanido, n-butanido, tert-butanido, 3,3-dimethyl-1-butyn-1-ido; Zn-MFU-4l-Me, -Et, -n-Bu, -t-Bu, -Butyne) and two new Co-MFU-4l structures, Co-MFU-4l-Me ([Zn1.5IICo3.5IIMe3.1Cl0.9(BTDD)3]) and Co-MFU-4l-OH ([Zn1.4IICo3.6II (OH)3.1Cl0.9(BTDD)3]), were obtained. Such side ligands were not characterized for MFU-4-type MOFs before, although they are presumed responsible for the metal site activation during olefin catalysis reactions, which require organometallic co-catalysts. For this purpose, a combination of simulated and measured IR spectra was developed as well-suited characterization technique for such insoluble materials, which preclude analytical methods like liquid state NMR and mass spectroscopy. A high stability of the organometallic Zn-MFU-4l derivatives was observed, whereas the Co-MFU-4l-Me was of a pyrophoric nature and reacted upon water contact to Co-MFU-4l-OH, which exhibited a CO2 binding mechanism comparable to that of carbonic anhydrase. Synthesis of Kuratowski complexes built from 1H-benzotriazole-5,6-diamine (H-btda) ligands and post-synthetic exchange of the chloride side ligands with Tp/Tp* (Tp= hydrotris(pyrazolyl)borate; Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) provided us with a variety of six-fold diamine-functionalized molecular building blocks intended for the development of novel MOF construction pathways. Crystallization of those compounds have already led to the assembly of porous metal hydrogen-bonded frameworks (M-HOF), some of which have even exhibited permanent porosity. This is a rare property of this material class, which is still in its infancy with only a few structures reported so far. Overall, five new metal hydrogen-bonded framework assemblies (CFA-20-X ((2,6-lutidinium)+[Zn5X4(btda)6X]−· n(DMF); X= Cl−, Br−), CFA-20-Tp, CFA-20-Tp*, CFA-20-Tp*-DMSO ([Zn5Y4(btda)6]; Y = Tp, Tp*) could be characterized, thus representing a significant contribution to this field of study. Although no MOFs could be crystallized from reactions of these complexes with metal salts, preliminary results have shown that direct incorporation of metal sites is a suitable pathway to convert M-HOFs into more stable MOFs. Taking the functionality of MFU-4-type frameworks to the next level, the novel 1,1',5,5'-tetrahydro-6,6'-biimidazo[4,5-f]benzotriazole (H4-bibt) ligand was developed to potentiate the post-synthetic modification possibilities compared to other MFU-4-type frameworks via introduction of additional and easily accessible biimidazole coordination sites at the linker backbone. This gave rise to the five most sophisticated MFU-4-type structures prepared so far. Post-synthetic Tp ligand exchange in the resulting MFU-4-type CFA-19 ([Co5IICl4(H2-bibt)3]) provided the stable CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3]) framework, in which the additional coordination sites were saturated in a third modification step with MIBr(CO)3 (M= Re, Mn) moieties or deprotonated via introduction of ZnEt moieties. The resulting materials exhibit high metal site density single-crystal X-ray structures with over 1700 atoms per unit cell for the ReBr(CO)3@CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3·(ReIBr(CO)3)2.8]) and a thermally induced release of all CO ligands for the MnBr(CO)3@CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3(MnIBr(CO)3)3]·3.1(MnIBr(CO)X)). Preliminary results also indicate a facile incorporation of other coordination moieties such as MIICl2 (M= PdII, PtII). These proof-of-principle incorporations of coordination moieties and open metal sites render such CFA-19-type scaffolds promising supports for an even larger variety of active species intended for the binding and activation of small molecules in future investigations. Coincidental synthesis of the novel CFA-23 ((((propan-2-yl)oxidanium)+[Mn6IICl5(ta)8]−; H-ta= 1H-1,2,3-triazole) coordination framework provided the opportunity to investigate changes of the resulting magnetic properties in comparison to a similar structure built from 1H-1,2,3-benzotriazole, as well as the ultra-narrow character of the pore channels in CFA-23. High purity samples of the literature-known Fe(ta)2 (H-ta= 1H-1,2,3-triazole) framework were prepared and investigated in detail to unveil its record hysteresis spin-crossover phase transition. Aiming at the use of Fe(ta)2 in surface acoustic wave-based sensor applications, experimental and theoretical insights into the material’s electrical conductivity changes upon adsorption of inert gases were assisted with the measurement of adsorption isotherms and the determination of the resulting isosteric enthalpies of adsorption

Memorial Issue Dedicated to Dr. Howard D. Flack: The Man behind the Flack Parameter

The book is dedicated to the work and achievements of Howard Flack. It combines articles which describe his own work and the advances he made in the field of crystallography, with original research articles which focus on aspects related to Howard Flack's interests

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information about HabEx can be found here: https://www.jpl.nasa.gov/habex