Review of dynamic positioning control in maritime microgrid systems

For many offshore activities, including offshore oil and gas exploration and offshore wind farm construction, it is essential to keep the position and heading of the vessel stable. The dynamic positioning system is a progressive technology, which is extensively used in shipping and other maritime structures. To maintain the vessels or platforms from displacement, its thrusters are used automatically to control and stabilize the position and heading of vessels in sea state disturbances. The theory of dynamic positioning has been studied and developed in terms of control techniques to achieve greater accuracy and reduce ship movement caused by environmental disturbance for more than 30 years. This paper reviews the control strategies and architecture of the DPS in marine vessels. In addition, it suggests possible control principles and makes a comparison between the advantages and disadvantages of existing literature. Some details for future research on DP control challenges are discussed in this paper

A Wide Area Hierarchical Voltage Control for Systems with High Wind Penetration and an HVDC Overlay

The modern power grid is undergoing a dramatic revolution. On the generation side, renewable resources are replacing fossil fuel in powering the system. On the transmission side, an AC-DC hybrid network has become increasingly popular to help reduce the transportation cost of electricity. Wind power, as one of the environmental friendly renewable resources, has taken a larger and larger share of the generation market. Due to the remote locations of wind plants, an HVDC overlay turns out to be attractive for transporting wind energy due to its superiority in long distance transmission of electricity. While reducing environmental concern, the increasing utilization of wind energy forces the power system to operate under a tighter operating margin. The limited reactive capability of wind turbines is insufficient to provide adequate voltage support under stressed system conditions. Moreover, the volatility of wind further aggravates the problem as it brings uncertainty to the available reactive resources and can cause undesirable voltage behavior in the system. The power electronics of the HVDC overlay may also destabilize the gird under abnormal voltage conditions. Such limitations of wind generation have undermined system security and made the power grid more vulnerable to disturbances. This dissertation proposes a Hierarchical Voltage Control (HVC) methodology to optimize the reactive reserve of a power system with high levels of wind penetration. The proposed control architecture consists of three layers. A tertiary Optimal Power Flow computes references for pilot bus voltages. Secondary voltage scheduling adjusts primary control variables to achieve the desired set points. The three levels of the proposed HVC scheme coordinate to optimize the voltage profile of the system and enhance system security. The proposed HVC is tested on an equivalent Western Electricity Coordinated Council (WECC) system modified by a multi-terminal HVDC overlay. The effectiveness of the proposed HVC is validated under a wide range of operating conditions. The capability to manage a future AC/DC hybrid network is studied to allow even higher levels of wind

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 43)

Abstracts are provided for 128 patents and patent applications entered into the NASA scientific and technical information system during the period Jan. 1993 through Jun. 1993. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Inorganic micro/nanostructures-based high-performance flexible electronics for electronic skin application

Electronics in the future will be printed on diverse substrates, benefiting several emerging applications such as electronic skin (e-skin) for robotics/prosthetics, flexible displays, flexible/conformable biosensors, large area electronics, and implantable devices. For such applications, electronics based on inorganic micro/nanostructures (IMNSs) from high mobility materials such as single crystal silicon and compound semiconductors in the form of ultrathin chips, membranes, nanoribbons (NRs), nanowires (NWs) etc., offer promising high-performance solutions compared to conventional organic materials. This thesis presents an investigation of the various forms of IMNSs for high-performance electronics. Active components (from Silicon) and sensor components (from indium tin oxide (ITO), vanadium pentaoxide (V2O5), and zinc oxide (ZnO)) were realised based on the IMNS for application in artificial tactile skin for prosthetics/robotics. Inspired by human tactile sensing, a capacitive-piezoelectric tandem architecture was realised with indium tin oxide (ITO) on a flexible polymer sheet for achieving static (upto 0.25 kPa-1 sensitivity) and dynamic (2.28 kPa-1 sensitivity) tactile sensing. These passive tactile sensors were interfaced in extended gate mode with flexible high-performance metal oxide semiconductor field effect transistors (MOSFETs) fabricated through a scalable process. The developed process enabled wafer scale transfer of ultrathin chips (UTCs) of silicon with various devices (ultrathin chip resistive samples, metal oxide semiconductor (MOS) capacitors and n‐channel MOSFETs) on flexible substrates up to 4″ diameter. The devices were capable of bending upto 1.437 mm radius of curvature and exhibited surface mobility above 330 cm2/V-s, on-to-off current ratios above 4.32 decades, and a subthreshold slope above 0.98 V/decade, under various bending conditions. While UTCs are useful for realizing high-density high-performance micro-electronics on small areas, high-performance electronics on large area flexible substrates along with low-cost fabrication techniques are also important for realizing e-skin. In this regard, two other IMNS forms are investigated in this thesis, namely, NWs and NRs. The controlled selective source/drain doping needed to obtain transistors from such structure remains a bottleneck during post transfer printing. An attractive solution to address this challenge based on junctionless FETs (JLFETs), is investigated in this thesis via technology computer-aided design (TCAD) simulation and practical fabrication. The TCAD optimization implies a current of 3.36 mA for a 15 μm channel length, 40 μm channel width with an on-to-off ratio of 4.02x 107. Similar to the NRs, NWs are also suitable for realizing high performance e-skin. NWs of various sizes, distribution and length have been fabricated using various nano-patterning methods followed by metal assisted chemical etching (MACE). Synthesis of Si NWs of diameter as low as 10 nm and of aspect ratio more than 200:1 was achieved. Apart from Si NWs, V2O5 and ZnO NWs were also explored for sensor applications. Two approaches were investigated for printing NWs on flexible substrates namely (i) contact printing and (ii) large-area dielectrophoresis (DEP) assisted transfer printing. Both approaches were used to realize electronic layers with high NW density. The former approach resulted in 7 NWs/μm for bottom-up ZnO and 3 NWs/μm for top-down Si NWs while the latter approach resulted in 7 NWs/μm with simultaneous assembly on 30x30 electrode patterns in a 3 cm x 3 cm area. The contact-printing system was used to fabricate ZnO and Si NW-based ultraviolet (UV) photodetectors (PDs) with a Wheatstone bridge (WB) configuration. The assembled V2O5 NWs were used to realize temperature sensors with sensitivity of 0.03% /K. The sensor arrays are suitable for tactile e-skin application. While the above focuses on realizing conventional sensing and addressing elements for e-skin, processing of a large amount of data from e-skin has remained a challenge, especially in the case of large area skin. A Neural NW Field Effect Transistors (υ-NWFETs) based hardware-implementable neural network (HNN) approach for tactile data processing in e-skin is presented in the final part of this thesis. The concept is evaluated by interfacing with a fabricated kirigami-inspired e-skin. Apart from e-skin for prosthetics and robotics, the presented research will also be useful for obtaining high performance flexible circuits needed in many futuristic flexible electronics applications such as smart surgical tools, biosensors, implantable electronics/electroceuticals and flexible mobile phones

Flash Memory Devices

Flash memory devices have represented a breakthrough in storage since their inception in the mid-1980s, and innovation is still ongoing. The peculiarity of such technology is an inherent flexibility in terms of performance and integration density according to the architecture devised for integration. The NOR Flash technology is still the workhorse of many code storage applications in the embedded world, ranging from microcontrollers for automotive environment to IoT smart devices. Their usage is also forecasted to be fundamental in emerging AI edge scenario. On the contrary, when massive data storage is required, NAND Flash memories are necessary to have in a system. You can find NAND Flash in USB sticks, cards, but most of all in Solid-State Drives (SSDs). Since SSDs are extremely demanding in terms of storage capacity, they fueled a new wave of innovation, namely the 3D architecture. Today “3D” means that multiple layers of memory cells are manufactured within the same piece of silicon, easily reaching a terabit capacity. So far, Flash architectures have always been based on "floating gate," where the information is stored by injecting electrons in a piece of polysilicon surrounded by oxide. On the contrary, emerging concepts are based on "charge trap" cells. In summary, flash memory devices represent the largest landscape of storage devices, and we expect more advancements in the coming years. This will require a lot of innovation in process technology, materials, circuit design, flash management algorithms, Error Correction Code and, finally, system co-design for new applications such as AI and security enforcement

Optimal Control of Hybrid Systems and Renewable Energies

This book is a collection of papers covering various aspects of the optimal control of power and energy production from renewable resources (wind, PV, biomass, hydrogen, etc.). In particular, attention is focused both on the optimal control of new technologies and on their integration in buildings, microgrids, and energy markets. The examples presented in this book are among the most promising technologies for satisfying an increasing share of thermal and electrical demands with renewable sources: from solar cooling plants to offshore wind generation; hybrid plants, combining traditional and renewable sources, are also considered, as well as traditional and innovative storage systems. Innovative solutions for transportation systems are also explored for both railway infrastructures and advanced light rail vehicles. The optimization and control of new solutions for the power network are addressed in detail: specifically, special attention is paid to microgrids as new paradigms for distribution networks, but also in other applications (e.g., shipboards). Finally, optimization and simulation models within SCADA and energy management systems are considered. This book is intended for engineers, researchers, and practitioners that work in the field of energy, smart grid, renewable resources, and their optimization and control

Ultrafast Radiographic Imaging and Tracking: An overview of instruments, methods, data, and applications

Ultrafast radiographic imaging and tracking (U-RadIT) use state-of-the-art ionizing particle and light sources to experimentally study sub-nanosecond dynamic processes in physics, chemistry, biology, geology, materials science and other fields. These processes, fundamental to nuclear fusion energy, advanced manufacturing, green transportation and others, often involve one mole or more atoms, and thus are challenging to compute by using the first principles of quantum physics or other forward models. One of the central problems in U-RadIT is to optimize information yield through, e.g. high-luminosity X-ray and particle sources, efficient imaging and tracking detectors, novel methods to collect data, and large-bandwidth online and offline data processing, regulated by the underlying physics, statistics, and computing power. We review and highlight recent progress in: a.) Detectors; b.) U-RadIT modalities; c.) Data and algorithms; and d.) Applications. Hardware-centric approaches to U-RadIT optimization are constrained by detector material properties, low signal-to-noise ratio, high cost and long development cycles of critical hardware components such as ASICs. Interpretation of experimental data, including comparisons with forward models, is frequently hindered by sparse measurements, model and measurement uncertainties, and noise. Alternatively, U-RadIT makes increasing use of data science and machine learning algorithms, including experimental implementations of compressed sensing. Machine learning and artificial intelligence approaches, refined by physics and materials information, may also contribute significantly to data interpretation, uncertainty quantification and U-RadIT optimization.Comment: 51 pages, 31 figures; Overview of ultrafast radiographic imaging and tracking as a part of ULITIMA 2023 conference, Mar. 13-16,2023, Menlo Park, CA, US

Magnetic diagnostics algorithms for LISA Pathfinder: system identification and data analysis

LISA (Laser Interferometer Space Antenna) is a joint mission of ESA and NASA, which aims to be the first space-borne gravitational wave observatory. LISA will consist in a constellation of three spacecraft at the vertexes of an equilateral triangle of side 5 million kilometers. The constellation will orbit around the Sun trailing the Earth by some 20 degrees. Each of the spacecraft harbors two proof masses, carefully protected against external disturbances such as solar radiation pressure and charged particles, which ensures they are in nominal free-fall in the interplanetary gravitational field. Gravitational waves will show as differential accelerations between pairs of proof masses, and the main aim of LISA is to measure such acceleration using laser interferometry. The technologies required for the LISA mission are many and challenging. This, coupled with the fact that some flight hardware cannot be tested on ground, led ESA to define a technology demonstrator to test in flight the required critical technologies. This precursor mission is called LISA Pathfinder (LPF). The payload of LISA Pathfinder is the LISA Technology Package (LTP), and will be the highest sensitivity geodesic explorer flown to date. The LISA Technology Package is designed to measure relative accelerations between two test masses in nominal free fall placed in a single spacecraft, since one LISA arm is squeezed from 5 million kilometer to 35 cm. Its success will prove the maturity of the necessary technologies for LISA such as the Optical Metrology System and the Drag Free concept. The differential acceleration reading will be perturbed by identified disturbances, such as thermal fluctuations or magnetic effects. These disturbances are monitored by the Diagnostics Subsystem. The Magnetic Diagnostics System is one of its modules and is a critical subsystem, since magnetic noise is apportioned to 40% of the total noise budget. In this respect, to estimate the magnetic noise contribution, the Magnetic Diagnostics Subsystem will have two main tasks: (1) estimate the magnetic properties of the test masses, i.e., their remanent magnetic moment and susceptibility, and (2) infer the magnetic field and its gradient at the location of the test masses. To this end, the Magnetic Diagnostics Subsystem includes two coils which generate controlled magnetic fields at the locations of the test masses. These magnetic fields will excite the dynamical response of both test masses. Thus, by adequate processing of the kinematic excursions delivered by the interferometer, the magnetic characteristics of the test masses can be estimated within 1% accuracy level. Additionally, the Magnetic Diagnostic Subsystem includes a set of four tri-axial fluxgate magnetometers. However, the magnetic field and its gradient need to be measured at the positions of the test masses and the readouts of the magnetometers do not provide a direct measurement of the magnetic field at these positions. Thus, an interpolation method must be implemented to calculate them. This is a difficult problem, mostly because the magnetometers are too distant from the locations of the test masses (more than 20 cm away) and because there are not sufficient magnetic channels to go beyond a classical linear interpolation method, which yields extremely poor interpolation results. Consequently, in this thesis we present and validate an alternative interpolation method based on neural networks. We put forward its robustness and accuracy in several mission scenarios and we stress the importance of an extensive magnetic testing campaign. Under these assumptions, we deliver magnetic field and gradient estimates with 10% accuracy. Finally, the estimate of the magnetic noise contribution to the total acceleration between the two LPF’s test masses is determined with an accuracy of 15%. This result represents an enhancement of the estimation quality in one order of magnitude with respect to former studies.LISA (Laser Interferometer Space Antenna) és un missió espacial conjunta de l’ESA i la NASA, que serà el primer detector d’ones gravitacionals a l’espai. LISA consisteix en una constel·lació de tres satèl·lits situats als vèrtexs d’un triangle equilàter de 5 milions de quilòmetres de costat. La constel·lació orbitarà al voltant del Sol seguint la Terra a uns 20 graus. Cada un dels satèl·lits contindrà dues masses de prova, curosament protegides de pertorbacions externes com la pressió de la radiació solar, assegurant que estiguin en una caiguda lliure nominal en el camp gravitacional interplanetari. Les ones gravitacionals creen acceleracions diferencials entre el parell de masses de prova. Així doncs el principal objectiu de LISA és mesurar l’esmentada acceleració utilitzant interferometria làser. Les tecnologies necessàries per LISA són molt exigents. A més, la majoria d’elles no poden ser testejades a la Terra. Per tant, l’ESA va determinar la necessitat de llançar una missió precursora que actués com a demostrador tecnològic, aquesta missió és LISA Pathfinder (LPF). La seva càrrega útil és el LISA Technology Package (LTP) i serà el sensor geodèsic de més alta sensitivitat a l’espai. El LISA Technology Package està dissenyat per mesurar acceleracions diferencials entre dues masses de prova en caiguda lliure situades en un sol satèl·lit, reduint un dels braços de LISA des de 5 milions de quilòmetres fins a 35 cm. L’èxit de la missió suposaria la demostració de la maduresa de les tecnologies necessàries per LISA, com són el Optical Metrology System i el concepte Drag Free. La mesura de l’acceleració diferencial estarà afectada per certes pertorbacions com podrien ser les fluctuacions tèrmiques o els efectes magnètics a l’interior del satèl·lit. Aquestes pertorbacions són monitoritzades pel Subsistema de Diagnòstic. El Subsistema de Diagnòstic Magnètic és un dels seus mòduls i és un sistema crític, perquè el soroll magnètic representa un 40% del soroll total. Amb la finalitat d’estimar la contribució del soroll magnètic, el Subsistema de Diagnostic Magnètic ha de (1) estimar les propietats magnètiques de les masses de prova, i.e., el seu moment magnètic remanent i la seva susceptibilitat, i (2) estimar el camp magnètic i el seu gradient a la posició de les masses de prova. Així doncs, aquest subsistema integra dues bobines per generar camps magnètics a la posició de les masses. Aquests camps magnètics exciten la resposta dinàmica de les dues masses. Finalment, amb el processament de les excursions cinemàtiques proporcionades per l’interferòmetre podem estimar les característiques magnètiques amb una precisió de l’1%. D’altra banda, el Subsistema de Diagnòstic Magnètic també integra 4 magnetòmetres triaxials. No obstant, el camp magnètic i el seu gradient ha de ser mesurat a la posició de les masses de prova i les lectures dels magnetòmetres no estan situades en aquestes posicions. Per tant, cal implementar un sistema d’interpolació. Aquest problema presenta una dificultat especial perquè els magnetòmetres estan situats lluny de les masses de prova (més de 20 cm) i perquè només hi ha mesures magnètiques per realitzar una interpolació de primer ordre. Aquest mètode dóna resultats inacceptables, per tant en aquesta tesi presentem i validem un mètode d’interpolació alternatiu basat en xarxes neuronals. En demostrem la seva robustesa i exactitud en diferents casos i remarquem la importància de disposar d’una extensa campanya de tests magnètics. Sota aquests supòsits, estimem el camp magnètic i el seu gradient amb un error inferior al 10%. Finalment, l’estimat de la contribució del soroll magnètic en la mesura de l’acceleració diferencial de les dues masses de prova es pot determinar amb una exactitud del 15%. Aquest resultat suposa una millora de la qualitat d’estimació en un ordre de magnitud en comparació a estudis previs