AIICS

AIICS Publications

Student Theses

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2014
[14] Anders Wikström. 2014.
Resource allocation of drones flown in a simulated environment.
Student Thesis. 24 pages. ISRN: LIU-IDA/LITH-EX-G--14/003—SE.

In this report we compare three different assignment algorithms in how they can be used to assign a set of drones to get to a set of goal locations in an as resource efficient way as possible. An experiment is set up to compare how these algorithms perform in a somewhat realistic simulated environment. The Robot Operating system (ROS) is used to create the experimental environment. We found that by introducing a threshold for the Hungarian algorithm we could reduce the total time it takes to complete the problem while only sightly increasing total distance traversed by the drones.

2013
[13] Jakob Pogulis. 2013.
Testramverk för distribuerade system.
Student Thesis. 46 pages. ISRN: LIU-IDA/LITH-EX-G--13/010--SE.

When developing software that is meant to be distributed over several different computers and several different networks while still working together against a common goal there is a challenge in testing how updates within a single component will affect the system as a whole. Even if the performance of that specific component increases that is no guarantee for the increased performance of the entire system. Traditional methods of testing software becomes both hard and tedious when several different machines has to be involved for a single test and all of those machines has to be synchronized as well.This thesis has resulted in an exemplary application suite for testing distributed software. The thesis describes the method used for implementation as well as a description of the actual application suite that was developed. During the development several important factors and improvements for such a system was identified, which are described at the end of the thesis even though some of them never made it into the actual implementation. The implemented application suite could be used as a base when developing a more complete system in order to distribute tests and applications that has to run in a synchronized manner with the ability to report the results of each individual component.

[12] Christopher Bergdahl. 2013.
Modeling Air Combat with Influence Diagrams.
Student Thesis. 64 pages. ISRN: LIU-IDA/LITH-EX-A--13/031--SE.

Air combat is a complex situation, training for it and analysis of possible tactics are time consuming and expensive. In order to circumvent those problems, mathematical models of air combat can be used. This thesis presents air combat as a one-on-one influence diagram game where the influence diagram allows the dynamics of the aircraft, the preferences of the pilots and the uncertainty of decision making in a structural and transparent way to be taken into account. To obtain the players’ game optimal control sequence with respect to their preferences, the influence diagram has to be solved. This is done by truncating the diagram with a moving horizon technique and determining and implementing the optimal controls for a dynamic game which only lasts a few time steps.The result is a working air combat model, where a player estimates the probability that it resides in any of four possible states. The pilot’s preferences are modeled by utility functions, one for each possible state. In each time step, the players are maximizing the cumulative sum of the utilities for each state which each possible action gives. These are weighted with the corresponding probabilities. The model is demonstrated and evaluated in a few interesting aspects. The presented model offers a way of analyzing air combat tactics and maneuvering as well as a way of making autonomous decisions in for example air combat simulators.

[11] Johan Fredborg. 2013.
Spam filter for SMS-traffic.
Student Thesis. 82 pages. ISRN: LIU-IDA/LITH-EX-A--13/021-SE.

Communication through text messaging, SMS (Short Message Service), is nowadays a huge industry with billions of active users. Because of the huge userbase it has attracted many companies trying to market themselves through unsolicited messages in this medium in the same way as was previously done through email. This is such a common phenomenon that SMS spam has now become a plague in many countries.This report evaluates several established machine learning algorithms to see how well they can be applied to the problem of filtering unsolicited SMS messages. Each filter is mainly evaluated by analyzing the accuracy of the filters on stored message data. The report also discusses and compares requirements for hardware versus performance measured by how many messages that can be evaluated in a fixed amount of time.The results from the evaluation shows that a decision tree filter is the best choice of the filters evaluated. It has the highest accuracy as well as a high enough process rate of messages to be applicable. The decision tree filter which was found to be the most suitable for the task in this environment has been implemented. The accuracy in this new implementation is shown to be as high as the implementation used for the evaluation of this filter.Though the decision tree filter is shown to be the best choice of the filters evaluated it turned out the accuracy is not high enough to meet the specified requirements. It however shows promising results for further testing in this area by using improved methods on the best performing algorithms.

2012
[10] Full text  Jonatan Olofsson. 2012.
Towards Autonomous Landing of a Quadrotorusing Monocular SLAM Techniques.
Student Thesis. 102 pages. ISRN: LIU-IDA/LITH-EX-A--12/026--SE.

Use of Unmanned Aerial Vehicles have seen enormous growth in recent years due to the advances in related scientific and technological fields. This fact combined with decreasing costs of using UAVs enables their use in new application areas. Many of these areas are suitable for miniature scale UAVs - Micro Air Vehicles(MAV) - which have the added advantage of portability and ease of deployment. One of the main functionalities necessary for successful MAV deployment in real-world applications is autonomous landing. Landing puts particularly high requirements on positioning accuracy, especially in indoor confined environments where the common global positioning technology is unavailable. For that reason using an additional sensor, such as a camera, is beneficial. In this thesis, a set of technologies for achieving autonomous landing is developed and evaluated. In particular, state estimation based on monocular vision SLAM techniques is fused with data from onboard sensors. This is then used as the basis for nonlinear adaptive control as well trajectory generation for a simple landing procedure. These components are connected using a new proposed framework for robotic development. The proposed system has been fully implemented and tested in a simulated environment and validated using recorded data. Basic autonomous landing was performed in simulation and the result suggests that the proposed system is a viable solution for achieving a fully autonomous landing of a quadrotor.

[9] Full text  Anders Hongslo. 2012.
Stream Processing in the Robot Operating System framework.
Student Thesis. 79 pages. ISRN: LIU-IDA/LITH-EX-A--12/030--SE.

Streams of information rather than static databases are becoming increasingly important with the rapid changes involved in a number of fields such as finance, social media and robotics. DyKnow is a stream-based knowledge processing middleware which has been used in autonomous Unmanned Aerial Vehicle (UAV) research. ROS (Robot Operating System) is an open-source robotics framework providing hardware abstraction, device drivers, communication infrastructure, tools, libraries as well as other functionalities.This thesis describes a design and a realization of stream processing in ROS based on the stream-based knowledge processing middleware DyKnow. It describes how relevant information in ROS can be selected, labeled, merged and synchronized to provide streams of states. There are a lot of applications for such stream processing such as execution monitoring or evaluating metric temporal logic formulas through progression over state sequences containing the features of the formulas. Overviews are given of DyKnow and ROS before comparing the two and describing the design. The stream processing capabilities implemented in ROS are demonstrated through performance evaluations which show that such stream processing is fast and efficient. The resulting realization in ROS is also readily extensible to provide further stream processing functionality.

[8] Full text  Viet Ha Nguyen. 2012.
Design Space Exploration of the Quality of Service for Stream Reasoning Applications.
Student Thesis. 35 pages. ISRN: LIU-IDA/LITH-EX-A--12/027--SE.

An Unmanned Aerial Vehicle (UAV) is often an aircraft with no crew that can fly independently by a preprogrammed plan, or by remote control. Several UAV applications, like autonomously surveillance and traffic monitoring, are real-time applications. Hence tasks in these applications must complete within specied deadlines.Real Time Calculus (RTC) is a formal framework for reasoning about realtime systems and in particular streaming applications. RTC has its mathematical roots in Network Calculus. It supports timing analysis, estimating loads and predicting memory requirements.In this thesis, a formal analysis of real-time stream reasoning for UAV applications is conducted. The performance analysis is based on RTC using an abstract performance model of the streaming reasoning on board a UAV. In this study, we consider two dierent scheduling methods, first-in-first-out (FIFO) and fixed priority (FP). In the FIFO scheduling model the priorities of the tasks are assigned and processed based on the order of their arrival, while in the FP scheduling model the priorities of the tasks are preassigned. The Quality of Service (QoS) of these applications is calculated and analyzed in a proposed design space exploration framework.QoS can be defined dierently depending on what field we are studying and in this thesis we are interested in studying the delays of the real-time stream reasoning applications when (i) we fix jitters and number of instances and vary the periods, (ii) we fix the periods and number of instances and vary the jitters, and (iii) we fix the periods, jitters and vary the number of instances.

[7] Full text  Daniel Lazarovski. 2012.
Extending the Stream Reasoning in DyKnow with Spatial Reasoning in RCC-8.
Student Thesis. 74 pages. ISRN: LIU-IDA/LITH-EX-A--12/008--SE.

Autonomous systems require a lot of information about the environment in which they operate in order to perform different high-level tasks. The information is made available through various sources, such as remote and on-board sensors, databases, GIS, the Internet, etc. The sensory input especially is incrementally available to the systems and can be represented as streams. High-level tasks often require some sort of reasoning over the input data, however raw streaming input is often not suitable for the higher level representations needed for reasoning. DyKnow is a stream processing framework that provides functionalities to represent knowledge needed for reasoning from streaming inputs. DyKnow has been used within a platform for task planning and execution monitoring for UAVs. The execution monitoring is performed using formula progression with monitor rules specified as temporal logic formulas. In this thesis we present an analysis for providing spatio-temporal functionalities to the formula progressor and we extend the formula progression with spatial reasoning in RCC-8. The result implementation is capable of evaluating spatio-temporal logic formulas using progression over streaming data. In addition, a ROS implementation of the formula progressor is presented as a part of a spatio-temporal stream reasoning architecture in ROS.

2011
[6] Full text  Zlatan Dragisic. 2011.
Semantic Matching for Stream Reasoning.
Student Thesis. 110 pages. ISRN: LIU-IDA/LITH-EX-A--11/041--SE.

Autonomous system needs to do a great deal of reasoning during execution in order to provide timely reactions to changes in their environment. Data needed for this reasoning process is often provided through a number of sensors. One approach for this kind of reasoning is evaluation of temporal logical formulas through progression. To evaluate these formulas it is necessary to provide relevant data for each symbol in a formula. Mapping relevant data to symbols in a formula could be done manually, however as systems become more complex it is harder for a designer to explicitly state and maintain thismapping. Therefore, automatic support for mapping data from sensors to symbols would make system more flexible and easier to maintain.DyKnow is a knowledge processing middleware which provides the support for processing data on different levels of abstractions. The output from the processing components in DyKnow is in the form of streams of information. In the case of DyKnow, reasoning over incrementally available data is done by progressing metric temporal logical formulas. A logical formula contains a number of symbols whose values over time must be collected and synchronized in order to determine the truth value of the formula. Mapping symbols in formula to relevant streams is done manually in DyKnow. The purpose of this matching is for each variable to find one or more streams whose content matches the intended meaning of the variable.This thesis analyses and provides a solution to the process of semantic matching. The analysis is mostly focused on how the existing semantic technologies such as ontologies can be used in this process. The thesis also analyses how this process can be used for matching symbols in a formula to content of streams on distributed and heterogeneous platforms. Finally, the thesis presents an implementation in the Robot Operating System (ROS). The implementation is tested in two case studies which cover a scenario where there is only a single platform in a system and a scenario where there are multiple distributed heterogeneous platforms in a system.The conclusions are that the semantic matching represents an important step towards fully automatized semantic-based stream reasoning. Our solution also shows that semantic technologies are suitable for establishing machine-readable domain models. The use of these technologies made the semantic matching domain and platform independent as all domain and platform specific knowledge is specified in ontologies. Moreover, semantic technologies provide support for integration of data from heterogeneous sources which makes it possible for platforms to use streams from distributed sources.

[5] Full text  Marjan Alirezaie. 2011.
Semantic Analysis Of Multi Meaning Words Using Machine Learning And Knowledge Representation.
Student Thesis. 74 pages. ISRN: LiU/IDA-EX-A- -11/011- -SE.

The present thesis addresses machine learning in a domain of naturallanguage phrases that are names of universities. It describes two approaches to this problem and a software implementation that has made it possible to evaluate them and to compare them.In general terms, the system's task is to learn to 'understand' the significance of the various components of a university name, such as the city or region where the university is located, the scienti c disciplines that are studied there, or the name of a famous person which may be part of the university name. A concrete test for whether the system has acquired this understanding is when it is able to compose a plausible university name given some components that should occur in the name.In order to achieve this capability, our system learns the structure of available names of some universities in a given data set, i.e. it acquires a grammar for the microlanguage of university names. One of the challenges is that the system may encounter ambiguities due to multi meaning words. This problem is addressed using a small ontology that is created during the training phase.Both domain knowledge and grammatical knowledge is represented using decision trees, which is an ecient method for concept learning. Besides for inductive inference, their role is to partition the data set into a hierarchical structure which is used for resolving ambiguities.The present report also de nes some modi cations in the de nitions of parameters, for example a parameter for entropy, which enable the system to deal with cognitive uncertainties. Our method for automatic syntax acquisition, ADIOS, is an unsupervised learning method. This method is described and discussed here, including a report on the outcome of the tests using our data set.The software that has been implemented and used in this project has been implemented in C.

2010
[4] Full text  Fredrik Ă…slin. 2010.
Evaluation of Hierarchical Temporal Memory in algorithmic trading.
Student Thesis. 32 pages. ISRN: LIU-IDA/LITH-EX-G--10/005--SE.

This thesis looks into how one could use Hierarchal Temporal Memory (HTM) networks to generate models that could be used as trading algorithms. The thesis begins with a brief introduction to algorithmic trading and commonly used concepts when developing trading algorithms. The thesis then proceeds to explain what an HTM is and how it works. To explore whether an HTM could be used to generate models that could be used as trading algorithms, the thesis conducts a series of experiments. The goal of the experiments is to iteratively optimize the settings for an HTM and try to generate a model that when used as a trading algorithm would have more profitable trades than losing trades. The setup of the experiments is to train an HTM to predict if it is a good time to buy some shares in a security and hold them for a fixed time before selling them again. A fair amount of the models generated during the experiments was profitable on data the model have never seen before, therefore the author concludes that it is possible to train an HTM so it can be used as a profitable trading algorithm.

2009
[3] Full text  Mikael Nilsson. 2009.
Spanneröar och spannervägar.
Student Thesis. 126 pages. ISRN: -.

In this Master Thesis the possibility to efficiently divide a graph into spanner islands is examined. Spanner islands are islands of the graph that fulfill the spanner condition, that the distance between two nodes via the edges in the graph cannot be too far, regulated by the stretch constant, compared to the Euclidian distance between them. In the resulting division the least number of nodes connecting to other islands is sought-after. Different heuristics are evaluated with the conclusion that for dense graphs a heuristic using MAX-FLOW to divide problematic nodes gives the best result whereas for sparse graphs a heuristic using the single-link clustering method performs best. The problem of finding a spanner path, a path fulfilling the spanner condition, between two nodes is also investigated. The problem is proven to be NP-complete for a graph of size n if the spanner constant is greater than n^(1+1/k)*k^0.5 for some integer k. An algorithm with complexity O(2^(0.822n)) is given. A special type of graph where all the nodes are located on integer locations along the real line is investigated. An algorithm to solve this problem is presented with a complexity of O(2^((c*log n)^2))), where c is a constant depending only on the spanner constant. For instance, the complexity O(2^((5.32*log n)^2))) can be reached for stretch 1.5.

[2] Full text  Tommy Persson. 2009.
Evaluating the use of DyKnow in multi-UAV traffic monitoring applications.
Student Thesis. 75 pages. ISRN: LIU-IDA/LITH-EX-A--09/019--SE.

This Master’s thesis describes an evaluation of the stream-based knowledge pro-cessing middleware framework DyKnow in multi-UAV traffic monitoring applica-tions performed at Saab Aerosystems. The purpose of DyKnow is “to providegeneric and well-structured software support for the processes involved in gen-erating state, object, and event abstractions about the environments of complexsystems.\" It does this by providing the concepts of streams, sources, computa-tional units (CUs), entity frames and chronicles.This evaluation is divided into three parts: A general quality evaluation ofDyKnow using the ISO 9126-1 quality model, a discussion of a series of questionsregarding the specific use and functionality of DyKnow and last, a performanceevaluation. To perform parts of this evaluation, a test application implementinga traffic monitoring scenario was developed using DyKnow and the Java AgentDEvelopment Framework (JADE).The quality evaluation shows that while DyKnow suffers on the usability side,the suitability, accuracy and interoperability were all given high marks.The results of the performance evaluation high-lights the factors that affect thememory and CPU requirements of DyKnow. It is shown that the most significantfactor in the demand placed on the CPU is the number of CUs and streams. Italso shows that DyKnow may suffer dataloss and severe slowdown if the CPU istoo heavily utilized. However, a reasonably sized DyKnow application, such as thescenario implemented in this report, should run without problems on systems atleast half as fast as the one used in the tests.

1996
[1] Jonas Kvarnström. 1996.
A New Tractable Planner for the SAS+ Formalism.
Student Thesis. In series: LiTH-IDA-Ex #9625. 283 pages. ISRN: LiTH-IDA-Ex-9625.

Computer science