Application of inertial instruments for DSN antenna pointing and tracking

The feasibility of using inertial instruments to determine the pointing attitude of the NASA Deep Space Network antennas is examined. The objective is to obtain 1 mdeg pointing knowledge in both blind pointing and tracking modes to facilitate operation of the Deep Space Network 70 m antennas at 32 GHz. A measurement system employing accelerometers, an inclinometer, and optical gyroscopes is proposed. The initial pointing attitude is established by determining the direction of the local gravity vector using the accelerometers and the inclinometer, and the Earth's spin axis using the gyroscopes. Pointing during long-term tracking is maintained by integrating the gyroscope rates and augmenting these measurements with knowledge of the local gravity vector. A minimum-variance estimator is used to combine measurements to obtain the antenna pointing attitude. A key feature of the algorithm is its ability to recalibrate accelerometer parameters during operation. A survey of available inertial instrument technologies is also given

Innovative Solutions for Navigation and Mission Management of Unmanned Aircraft Systems

The last decades have witnessed a significant increase in Unmanned Aircraft Systems (UAS) of all shapes and sizes. UAS are finding many new applications in supporting several human activities, offering solutions to many dirty, dull, and dangerous missions, carried out by military and civilian users. However, limited access to the airspace is the principal barrier to the realization of the full potential that can be derived from UAS capabilities. The aim of this thesis is to support the safe integration of UAS operations, taking into account both the user's requirements and flight regulations. The main technical and operational issues, considered among the principal inhibitors to the integration and wide-spread acceptance of UAS, are identified and two solutions for safe UAS operations are proposed: A. Improving navigation performance of UAS by exploiting low-cost sensors. To enhance the performance of the low-cost and light-weight integrated navigation system based on Global Navigation Satellite System (GNSS) and Micro Electro-Mechanical Systems (MEMS) inertial sensors, an efficient calibration method for MEMS inertial sensors is required. Two solutions are proposed: 1) The innovative Thermal Compensated Zero Velocity Update (TCZUPT) filter, which embeds the compensation of thermal effect on bias in the filter itself and uses Back-Propagation Neural Networks to build the calibration function. Experimental results show that the TCZUPT filter is faster than the traditional ZUPT filter in mapping significant bias variations and presents better performance in the overall testing period. Moreover, no calibration pre-processing stage is required to keep measurement drift under control, improving the accuracy, reliability, and maintainability of the processing software; 2) A redundant configuration of consumer grade inertial sensors to obtain a self-calibration of typical inertial sensors biases. The result is a significant reduction of uncertainty in attitude determination. In conclusion, both methods improve dead-reckoning performance for handling intermittent GNSS coverage. B. Proposing novel solutions for mission management to support the Unmanned Traffic Management (UTM) system in monitoring and coordinating the operations of a large number of UAS. Two solutions are proposed: 1) A trajectory prediction tool for small UAS, based on Learning Vector Quantization (LVQ) Neural Networks. By exploiting flight data collected when the UAS executes a pre-assigned flight path, the tool is able to predict the time taken to fly generic trajectory elements. Moreover, being self-adaptive in constructing a mathematical model, LVQ Neural Networks allow creating different models for the different UAS types in several environmental conditions; 2) A software tool aimed at supporting standardized procedures for decision-making process to identify UAS/payload configurations suitable for any type of mission that can be authorized standing flight regulations. The proposed methods improve the management and safe operation of large-scale UAS missions, speeding up the flight authorization process by the UTM system and supporting the increasing level of autonomy in UAS operations

Micro/Nano Manufacturing

Micro manufacturing involves dealing with the fabrication of structures in the size range of 0.1 to 1000 µm. The scope of nano manufacturing extends the size range of manufactured features to even smaller length scales—below 100 nm. A strict borderline between micro and nano manufacturing can hardly be drawn, such that both domains are treated as complementary and mutually beneficial within a closely interconnected scientific community. Both micro and nano manufacturing can be considered as important enablers for high-end products. This Special Issue of Applied Sciences is dedicated to recent advances in research and development within the field of micro and nano manufacturing. The included papers report recent findings and advances in manufacturing technologies for producing products with micro and nano scale features and structures as well as applications underpinned by the advances in these technologies

Enhancement of Energy Efficiency for Thermal Energy and Biomass Driven Applications

The importance of gas turbine blades is to convert the thermal energy into shaft work output, which makes the turbine blades are one of the critical components of the gas turbines. Besides the mechanical stresses caused by the centrifugal force and the fluid forces, the thermal stresses arise because of the temperature gradient within the blade materials. This paper aims to have a uniform circumferential temperature field at the combustor exit, consequently reducing the thermal stresses caused by the non-uniform temperature distribution along the turbine blade. The validation of the simulation results with the experiments showed an acceptable agreement with available experimental data. The agreement includes the uniformity factor and the normalized mixture fraction at two different flowrates.Furthermore, sixteen cases studies have been implemented to study the effect of changing Internal Guide Vanes location, concerning the test section holes and the primary stream. The results show that the best location of the Internal Guide vanes is to be placed on the large holes of the dilution section with a 30o angle to the primary stream direction. This method gives 25% higher in thermal uniformity compared to attach them to the small holes. Compared to different orientations, it provides 14% higher regarding the thermal uniformity. Another location of the guide vanes, External Guide Vanes, was experimentally and numerically tested. The results show that the external guide vanes with a 30o orientation gave the most uniform temperature flow for the two different flow rates. Compared to the internal guide vanes with the same orientation, the external guide vanes gave a 7.5% higher uniformity factor and 2% lower pressure drop. The main reason for this result is that the external guide vanes direct the cold stream to penetrate the dilution zone with an angel enhance the swirling effect which are the main factors for excellent mixing, while the pressure drop is lower as the external guide vanes are facing the lower flowrate which is the secondary stream. Another advantage of the external guide vanes over the internal ones is that they are subjected to less thermal stresses as they are facing the cold flow. Furthermore, the external guide vanes are reachable and easy to maintain compared to the internal guide vanes. Finally, the combustor outer surface design has been investigated. Four different angles have been tested numerically and experimentally with a maximum error of 5% at two different Reynolds numbers. Designing the outer combustor surface with a 45-angle bend can give a more uniform temperature distribution of 37% higher than the basic design with only a 0.5% higher pressure drop. Moving to biomass, different thermochemical conversion processes on different biomass species were presented. The results show it is recommended to use the lowest heating rate to allow a quasi-equilibrium state through slow heating, hence avoiding measurement errors. Chicken manure, thermal degradation of the three main components of the chicken manure was obtained. The initial results show that for the slow heating rates, 5oC/min, the thermal degradation of the cow manure is different compared to that one obtained from chicken manure. The Hemicellulose decomposition took place at 250oC and 300oC for the chicken manure and cow manure, respectively. The Cellulose decomposition was started at 300oC for chicken manure and 470oC for cow manure. Gasification, all reactions were endothermic when CO2 used as a gasifying agent. Consequently, the energy must be supplied in terms of heating to sustain the reaction while air gasification was exothermic, which means that the reaction can be sustained without external heating where the self-ignition was observed between 450oC - 600oC. In addition, it was observed that carbon dioxide had the most complicated mechanism with four stages. The cow manure as well has been tested for gasification using the air and CO2 as gasifying agents. At the same temperatures of pyrolysis process the breakup of the hemicellulose and cellulose has occurred 302 oC and 500 oC while the lignin thermal degradation occurred at 745 oC. The 5 oC/min heat rate shows the best results in terms of keeping a very stable exothermic reaction compared to the other heating rates. The CO2 gasification for the cow manure shows poor results (endothermic reactions). This means that the carbon dioxide cannot be used with the cow manure as a gasifying agent since it needs a lot of energy to generate syngas. CO-Pyrolysis, results show the 40%RH-60%CH decreasing the energy of activation by 12% compared to Chicken manure. In addition, an increase in the conversion greater than 3% was achieved. The 40% CM-60%CH shows a positive result in terms of keeping an exothermic reaction over the Co-Pyrolysis process. Finally, CO-gasification, air is used as a gasifying agent, of the cow manure with the sheep manure has been investigated to show that the blend mixture of 20% sheep manure and 80% cow manure give the highest exothermic reaction among all other cases

Assessment on the Flammability of External Façade Materials via Advanced Pyrolysis Kinetics Search Algorithms Coupled with CFD Simulations

Façade fire is the root cause of catastrophe fires in high-rise commercial and residential buildings. Due to the extensive use of combustible polymers in interior furnishing and exterior façade systems, the frequency of high-rise façade fires has increased by seven times worldwide over the last three decades. A novel technique to assess the fire performance of the new generation of polymeric materials would be beneficial to realise the cladding fire issue. Furthermore, considering the façade system and incorporating it in the building simulation model as a whole is critical for accurate prediction, precaution and responding measures. In this study, a methodical approach including (i) material testing, (ii) pyrolysis kinetics characterisation, (iii) model validation, and (iv) application, has been formulated for the assessment of the fire performance and burning behaviour of existing household furnishing materials as well as flame retardant polymers. On the other hand, the addition of FR compounds is one of the effective methods to reduce the flammability of polymers. A series of bench-scale fire tests have been conducted to acquire the thermal stability and flammability limits of the materials, including thermogravimetric analysis (TGA), and the cone calorimeter test coupled with Fourier transform infrared spectroscopy (FTIR) gas analysis. Through the genetic algorithm approach, precise pyrolysis kinetics can be extracted and provide quality data input for computational fluid dynamics (CFD) modelling. A pyrolysis database is then formulated to fill the gaps that restrict the research capability of fire modelling and mathematical models since they are of little value without adequate validation by experimental data. An innovative in-house fire field model based on the Large Eddy Simulation (LES) method embraces a multiple species transportation combustion model, fully-coupled with soot formation, and radiation models have been utilised for façade fire modelling. This LES model considers the interacting physical and chemical phenomena for a turbulent reacting flame involving the fluid mixture. Generally, these equations comprise mass, energy and momentum conservation along with applicable boundary conditions. All fundamental behaviours and phenomena of non-premixed flame can be modelled. Two fire field models have been created and examined: (i) bench-scale pyrolysis model and (ii) up-scale façade fire model. The heat release rate (HRR) time profile and their magnitudes were in good agreement with the experimental results. The overall results demonstrated that the model was capable of capturing the fire development process. With the consideration of detailed reaction mechanisms, the formation of both hydrocarbon and nitrogen oxides involved in combustion processes identified that asphyxiant gases including CO and CO2 can be reasonably predicted. With enhanced computational ability, this mechanism can be utilised in numerous fire scenarios to assess fire hazards, which would otherwise require large-scale fire tests to achieve optimal fire prevention and protection for façade systems

QUANTUM DETECTION AND PARAMETER ESTIMATION FOR CONTINUOUSLY MEASURED SYSTEMS

Ph.DDOCTOR OF PHILOSOPH

Resource-efficient strategies for mobile ad-hoc networking

The ubiquity and widespread availability of wireless mobile devices with ever increasing inter-connectivity (e. g. by means of Bluetooth, WiFi or UWB) have led to new and emerging next generation mobile communication paradigms, such as the Mobile Ad-hoc NETworks (MANETs). MANETs are differentiated from traditional mobile systems by their unique properties, e. g. unpredictable nodal location, unstable topology and multi-hop packet relay. The success of on-going research in communications involving MANETs has encouraged their applications in areas with stringent performance requirements such as the e-healthcare, e. g. to connect them with existing systems to deliver e-healthcare services anytime anywhere. However, given that the capacity of mobile devices is restricted by their resource constraints (e. g. computing power, energy supply and bandwidth), a fundamental challenge in MANETs is how to realize the crucial performance/Quality of Service (QoS) expectations of communications in a network of high dynamism without overusing the limited resources. A variety of networking technologies (e. g. routing, mobility estimation and connectivity prediction) have been developed to overcome the topological instability and unpredictability and to enable communications in MANETs with satisfactory performance or QoS. However, these technologies often feature a high consumption of power and/or bandwidth, which makes them unsuitable for resource constrained handheld or embedded mobile devices. In particular, existing strategies of routing and mobility characterization are shown to achieve fairly good performance but at the expense of excessive traffic overhead or energy consumption. For instance, existing hybrid routing protocols in dense MANETs are based in two-dimensional organizations that produce heavy proactive traffic. In sparse MANETs, existing packet delivery strategy often replicates too many copies of a packet for a QoS target. In addition, existing tools for measuring nodal mobility are based on either the GPS or GPS-free positioning systems, which incur intensive communications/computations that are costly for battery-powered terminals. There is a need to develop economical networking strategies (in terms of resource utilization) in delivering the desired performance/soft QoS targets. The main goal of this project is to develop new networking strategies (in particular, for routing and mobility characterization) that are efficient in terms of resource consumptions while being effective in realizing performance expectations for communication services (e. g. in the scenario of e-healthcare emergency) with critical QoS requirements in resource-constrained MANETs. The main contributions of the thesis are threefold: (1) In order to tackle the inefficient bandwidth utilization of hybrid service/routing discovery in dense MANETs, a novel "track-based" scheme is developed. The scheme deploys a one-dimensional track-like structure for hybrid routing and service discovery. In comparison with existing hybrid routing/service discovery protocols that are based on two-dimensional structures, the track-based scheme is more efficient in terms of traffic overhead (e. g. about 60% less in low mobility scenarios as shown in Fig. 3.4). Due to the way "provocative tracks" are established, the scheme has also the capability to adapt to the network traffic and mobility for a better performance. (2) To minimize the resource utilization of packet delivery in sparse MANETs where wireless links are intermittently connected, a store-and-forward based scheme, "adaptive multicopy routing", was developed for packet delivery in sparse mobile ad-hoc networks. Instead of relying on the source to control the delivery overhead as in the conventional multi-copy protocols, the scheme allows each intermediate node to independently decide whether to forward a packet according to the soft QoS target and local network conditions. Therefore, the scheme can adapt to varying networking situations that cannot be anticipated in conventional source-defined strategies and deliver packets for a specific QoS targets using minimum traffic overhead. ii (3) The important issue of mobility measurement that imposes heavy communication/computation burdens on a mobile is addressed with a set of resource-efficient "GPS-free" soluti ons, which provide mobility characterization with minimal resource utilization for ranging and signalling by making use of the information of the time-varying ranges between neighbouring mobile nodes (or groups of mobile nodes). The range-based solutions for mobility characterization consist of a new mobility metric for network-wide performance measurement, two velocity estimators for approximating the inter-node relative speeds, and a new scheme for characterizing the nodal mobility. The new metric and its variants are capable of capturing the mobility of a network as well as predicting the performance. The velocity estimators are used to measure the speed and orientation of a mobile relative to its neighbours, given the presence of a departing node. Based on the velocity estimators, the new scheme for mobility characterization is capable of characterizing the mobility of a node that are associated with topological stability, i. e. the node's speeds, orientations relative to its neighbouring nodes and its past epoch time. iiiBIOPATTERN EU Network of Excellence (EU Contract 508803