Thesis--Göttingen. / "Lebenslauf." "Verzeichnis der mehrfach benutzen Quellen-und Literaturwerke." p. vi-x.

Thesis--Göttingen. / "Lebenslauf." eContent provider-neutral record in process. Description based on print version record. "Verzeichnis der mehrfach benutzen Quellen-und Literaturwerke." p. vi-x.

Many applications for unmanned vehicles involve autonomous interaction between two or more craft, and therefore, relative navigation is a key issue to explore. Several high fidelity hardware simulations exist to produce accurate dynamics. However, these simulations are restricted by size, weight, and power needed to operate them. The use of a small Unmanned Ground Vehicle (UGV) for the relative navigation problem is investigated. The UGV has the ability to traverse large ranges over uneven terrain and into varying lighting conditions which has interesting applications to relative navigation. The basic problem of a vehicle following another is researched and a possible solution explored. Statistical pressure snakes are used to gather relative position data at a specified frequency. A cubic spline is then fit to the relative position data using a least squares algorithm. The spline represents the path on which the lead vehicle has already traversed. Controlling the UGV onto this relative path using a sliding mode control, allows the follow vehicle to avoid the same stationary obstacles the lead vehicle avoided without any other sensor information. The algorithm is run on the UGV hardware with good results. It was able to follow the lead vehicle around a curved course with only centimeter-level position errors. This sets up a firm foundation on which to build a more versatile relative motion platform. / Master of Science

In a variety of military operations, a convoy of autonomous followers may need to traverse the leader's path without using Global Positioning System (GPS), lane markers/magnets and/or a vision-based vehicle-following system. This can be achieved by using Visual Teach and Repeat (VT and R), which provides an effective method for autonomous repeating of a previously driven path. This thesis describes the design of a distributed control system that uses the idea behind the VT and R method to allow a convoy of inter-communicable autonomous vehicles to follow a manually-driven lead vehicle's path with a desired inter-vehicle spacing, even when the leader is not in the camera view of the followers. The longitudinal controller is designed for addressing a 1D spacing problem and then combined with a path tracker for tracking a path in a 2D environment. The designed control model is tested in simulations.

In a variety of military operations, a convoy of autonomous followers may need to traverse the leader's path without using Global Positioning System (GPS), lane markers/magnets and/or a vision-based vehicle-following system. This can be achieved by using Visual Teach and Repeat (VT and R), which provides an effective method for autonomous repeating of a previously driven path. This thesis describes the design of a distributed control system that uses the idea behind the VT and R method to allow a convoy of inter-communicable autonomous vehicles to follow a manually-driven lead vehicle's path with a desired inter-vehicle spacing, even when the leader is not in the camera view of the followers. The longitudinal controller is designed for addressing a 1D spacing problem and then combined with a path tracker for tracking a path in a 2D environment. The designed control model is tested in simulations.

GPS denied environments cause each unmanned ground vehicle (UGV) in an autonomous convoy to lose positional accuracy which can lead to inoperability, or even damage. In order for autonomous convoy systems to fill the needs of any particular field, a well-performing system must be designed such that a convoy can operate in any environment. Ultra-wideband (UWB) radios are a proposed solution to GPS denied localization.The main objective of this research is to use UWB radios to localize a leader vehicle within a convoy situation while in a GPS denied environment.

<p>Kretanje potiskivanog sklopa/sastava je njegova sposobnost da se premešta<br />nekom brzinom usled delovanja određene sile koja mu je pridodata.Ovu silu<br />stvaraju brodski propeleri i pri zadatoj brzini v=const ona treba da bude<br />jednaka sili otpora sredine-vode i vazduha.Iz tog razloga korisna sila koju<br />razvijaju propeleri broda-potiskivača pri plovidbi sa sastavom potisnica<br />pri v=const treba da savlada ne samo otpor svih potisnica u sastavu već i<br />sopstveni otpor broda. Za planere procesa vodnog prevoženja neophodno je,<br />osim poznavanja veličine otpora sredine pri plovidbi potiskivanih<br />sklopova i poznavanje redukovanih i specifičnih otpora pojedinih tipova<br />potiskivanih teretnjaka i sastva koje oni čine. Osim toga, predložene su<br />metode za proračun očekivanih brzina plovidbe u mirnoj vodi i očekivanih<br />vrednosti pokazatelja statičkog opterećenja utvrđenih na osnovu obavljenih<br />eksperimenata po pojedinim tipovima brodova i potiskivanih sastva. Takođe,<br />predloženi su novi tehnički i eksploatacioni pokazatelji za ocenu<br />ispravnosti rada potiskivača, koji do sada nisu primenjivani u Srbiji. Na<br />kraju disertacije prikazane su metode kojima se rešavaju praktični zadaci<br />prevoženja po različitimh brodovima potiskivačima i potiskivanim<br />sastavima.</p> / <p>Movement of convoy/pushed convoy is its ability to change place due to certain<br />force that drives it. This force is created by ship&rsquo;s propellers for given speed v=const<br />and it should be equal to resistance of surrounding water and air. This is the reason<br />why useful force created by ships propellers (thrust) created by propellers of pushboat<br />while navigating with a convoy at v=const needs to overcome not only the<br />resistance of barges but push-boat&rsquo;s resistance as well. For planers of transport<br />process it is necessary to know, besides the resistance of surroundings during<br />navigation of pushed convoys, the value of reduced and specific resistance for certain<br />types of barges and convoys that they form. Apart from that methods for calculation<br />of expected speeds of navigation, value of static load of engines based on<br />experimental research. Besides that new exploitation parameters for determination of<br />push-boat&rsquo;s work are proposed, which haven&rsquo;t been used in Serbia. At the end<br />dissertation presents methods to solve practical transportation tasks for different<br />ships with different convoys.</p>

The urge to consume does not seem to stop, thus, the need for transportation of goods will most likely not decrease. At the same time jurisdictions and regulations around greenhouse gas emissions are sharpening and pushing the industry towards a more environmentally friendly state. The freight and transportation industry is facing a huge challenge in the upcoming years and solutions are needed to feed the demand of society. Two, of many, proposals of solving, at least, parts of the above mentioned problem is platooning and the look-ahead controller. Platooning denotes the concept of slipstream where maximum utilization of aerodynamic drag reduction is endeavoured. The lookahead controller exploits the surrounding topographical information in order to yield an optimal driving strategy, often resulting in that the vehicle initiates the phenomenon of pulse and glide, which denotes alternating between high load operation points and freewheeling, i.e. engaging neutral gear. This work has sought to investigate these concepts to determine whether or not additional fuel-efficiency can be added by manipulating and re-designing the control unit of the system. The proposed addition is built upon the look-ahead controller and supplements it by enabling communication between vehicles such that micro-transactions may occur in order to aid decision making regarding the choice of driving strategies. A vehicle model, a platoon model and the novel optimization based look-ahead-controller was synthesized and developed, where dynamic programming was used as the optimization solver of the controller. The look-ahead controller was verified such that one can conclude that it behaves according to the assumptions of such a system. The proposed micro-transaction system was also verified to conclude that it behaves as assumed, yielding a reduction in fuel consumption. For a platoon of two members, a 1.2% and 1.7% reduction in fuel consumption for the leading and following vehicle respectively was obtained, compared to an identical platooning setup, using a lookahead controller, but where no negotiations using micro-transactions are allowed between the vehicles.

Autonomous heavy vehicles will enable the promise of decreased energy consumption through the ability to platoon in closer formation than is currently safe or legal. It is therefore increasingly important to understand the complex and dynamic wake interactions between vehicles operating in close proximity for aerodynamic gains. In recent years, a growing body of research has documented a bi-stable, shifting wake generated behind the Ahmed reference bluff body. At the same time, studies of platooning Ahmed bodies have focused on changes to the body forces and moments at different following distances or lateral offsets, typically based around time-averaged measurements or steady-state CFD. The present study attempts to understand the implications of bi-stability in the wake of two square-back, platooning Ahmed bodies, given the potential for transient instabilities. Temporally-correlated static pressures were measured on two identical wind tunnel models at various following distances to uncover the time-dependent interactions between platooning vehicles. Bi-stability is highly dependent on symmetry and the uniformity of oncoming flow, and it is shown that a shifting bi-stable wake behind the lead vehicle leads to correlated, bi-stable flow patterns on the following vehicle, even in the absence of a lateral offset. At a following distance of 0.25L, pressure data indicated there may be a point where this bi-stable behavior reaches a critical point between suppression and amplification, significantly affecting the aerodynamic loads on the lead vehicle. This leads to the conclusion that bi-stable wake interactions between vehicles may be useful to consider in the context of real-time organization of vehicle platoons.

Movement pattern mining involves the processing of movement data to understand the mobility behaviour of humans/animals. Movement pattern mining has numerous applications, e.g. traffic optimization, event planning, optimization of public transport and carpooling. The recent digital revolution has caused a wide-spread use of smartphones and other devices equipped with GPS. These devices produce a tremendous amount of movement data which contains valuable mobility information. Many interesting mobility patterns and algorithms to mine them have been proposed in recent years to mine different types of mobility behaviours, e.g. convoy, flock, group, swarm or platoon, etc. The drastic increase in the volumes of data being generated limits the use of these algorithms in the mining of movement patterns on real-world data sizes because of their lack of scalability.This thesis deals with three aspects of movement pattern mining, i.e. scalability, efficiency, and real-timeliness with a focus on convoy pattern mining. A convoy pattern is a group of objects moving together for a certain period. Mining of convoy pattern involves clustering of the movement dataset at each timestamp and then merging the clusters to form convoys. Clustering the whole dataset is a limiting factor in the scalability of existing algorithms. One way to solve the scalability problem is to mine convoys in parallel. Parallel mining can be done either using the existing distributed spatiotemporal data processing system like Parallel Secondo or by using a general distributed data processing system. We first test the scalability behaviour of Parallel Secondo for mining movement patterns and conclude that it is not an industrial grade system and its scalability is limited. An essential part of designing distributed data processing algorithms is the data partitioning strategy. We study three different data partitioning strategies, i.e. Object-based, spatial and temporal. We analyze their suitability to convoy pattern mining based on 5 properties, i.e. data exchange, data redundancy, partitioning cost, disk seeks and data ordering. Our study shows that the temporal partitioning strategy is best suited for convoy mining as it is easily parallelizable and less complicated. The observations in our study also apply to other movement pattern mining algorithms, e.g. flock, group or platoon, etc.Based on the temporal partitioning strategy, we propose a generic distributed shared nothing convoy mining algorithm called DCM which is linearly scalable concerning the data size, data density and the number of nodes. DCM can be implemented using any distributed data processing framework. For our experiments, we implemented the algorithm using the Hadoop MapReduce framework. It performs better than the existing sequential algorithms, i.e. CuTs family of algorithms by an order of magnitude on different computing architectures, e.g. single x86 machine, multi-core cluster with NUMA architecture and multi-node SMP clusters. Although DCM is a scalable distributed algorithm which can process huge datasets, the cost of maintaining the cluster is high. Also, the heavy computation it incurs because of the requirement of clustering the whole dataset is not resource-efficient.To solve the efficiency problem of DCM, we propose a new sequential algorithm called k/2-hop which even being a sequential algorithm can perform orders of magnitude faster than the existing state-of-the-art sequential as well as distributed algorithms. The main strength of the algorithm is its pruning capability. Our experiments show that it can prune up to 99% of the data. k/2-hop uses a notion of benchmark points which are timestamps separated by k/2 timestamps where k is the minimum length of the convoys to be mined. We prove that to be able to mine maximal convoys; we need to cluster the data belonging to the benchmark points only. For the timestamps between two consecutive benchmark points, we propose an efficient mining algorithm called the Hop Window Mining Tree (HWMT). HWMT clusters the data corresponding to only those objects that are part of a cluster in the benchmark points. k/2-hop is a batch algorithm that can mine convoys very fast, but we only get the result when the complete dataset has been processed. Also, it requires the data to be indexed for better performance and thus cannot be used in real-time scenarios. We propose a streaming variant of the k/2-hop algorithm which does not require the input dataset to be indexed and can process a stream of data. It outputs the mined convoys as and when they are discovered. The streaming k/2-hop algorithm is very memory efficient and can process data that is many times bigger than the memory made available to the algorithm. We show through experiments that if we include the data loading and indexing time in the runtime of the k/2-hop algorithm, streaming k/2-hop is the fastest convoy mining algorithm to date. Convoy pattern is part of a bigger category of co-movement patterns, and most of the observations (if not all) made in this thesis about convoy pattern mining also apply to other patterns of the category such as flock, group or platoon, etc. This applicability means that a generic batch and streaming distributed co-movement pattern mining framework can be build using the k/2 technique. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished