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  • 1.
    Diyar, Jamal
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Post-Pruning of Random Forests2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract 

    Context. In machine learning, ensemble methods continue to receive increased attention. Since machine learning approaches that generate a single classifier or predictor have shown limited capabilities in some contexts, ensemble methods are used to yield better predictive performance. One of the most interesting and effective ensemble algorithms that have been introduced in recent years is Random Forests. A common approach to ensure that Random Forests can achieve a high predictive accuracy is to use a large number of trees. If the predictive accuracy is to be increased with a higher number of trees, this will result in a more complex model, which may be more difficult to interpret or analyse. In addition, the generation of an increased number of trees results in higher computational power and memory requirements. 

    Objectives. This thesis explores automatic simplification of Random Forest models via post-pruning as a means to reduce the size of the model and increase interpretability while retaining or increasing predictive accuracy. The aim of the thesis is twofold. First, it compares and empirically evaluates a set of state-of-the-art post-pruning techniques on the simplification task. Second, it investigates the trade-off between predictive accuracy and model interpretability. 

    Methods. The primary research method used to conduct this study and to address the research questions is experimentation. All post-pruning techniques are implemented in Python. The Random Forest models are trained, evaluated, and validated on five selected datasets with varying characteristics. 

    Results. There is no significant difference in predictive performance between the compared techniques and none of the studied post-pruning techniques outperforms the other on all included datasets. The experimental results also show that model interpretability is proportional to model accuracy, at least for the studied settings. That is, a positive change in model interpretability is accompanied by a negative change in model accuracy. 

    Conclusions. It is possible to reduce the size of a complex Random Forest model while retaining or improving the predictive accuracy. Moreover, the suitability of a particular post-pruning technique depends on the application area and the amount of training data available. Significantly simplified models may be less accurate than the original model but tend to be perceived as more comprehensible. 

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  • 2.
    Fors, Christoffer
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Johansson, Philip
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering.
    Kollaborativa Robotar: Verifiering av kraft och tryck vid kollision mellan robot och människa2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Collaborative robots are a new type of robot that unlike industrial robots are to be used in close relation to humans without physical walls. Due to this, high demands are placed on the safety of collaborative robots as people must not be harmed. To verify the safety between robot and human, collision measurements are made. For the past 10 years, the number of published articles dealing with Human RobotCollaboration has gone from almost none to approximately 3000 published articles per year. It can also be seen that research on collisions together with cooperation between robots and humans has increased during the same period but not at all in the same size. The thesis is made together with Scania which is a truck manufacturer in Sweden. Scania has its own requirements for safety around collaborative robots and they require that collision measurements in the form of pressure and force take place during each implementation of a collaborative robot. The purpose is to provide a broader knowledge of collaborative robots and their safety. To provide knowledge of how collision measurements should be made and with which tools. Using a spiral development model, several practical measurements were performed on a collaborative robot. Other methods used were interviews, literature study, calculations and benchmarking. The results show that the values set in the robot do not always correspond to those obtained during practical feeds. It uses the robot to show permissible forces in a collaborative position, but also many impermissible force measurements have taken place at different switches and at different speeds. The distance between the robot's base and the robot’s arm where the collision cuts make a great impact on the measurements and show that it can be a danger. Running a collaborative robot at high speeds without external safety equipment also demonstrates risks. Pressure measurements show a large uncertainty of the result and the result is also above the permissible limit in several cases. The impermissible pressures indicate danger for people to work in close contact with collaborative robots. The high difference in the measurement result is only for pressure measurements and the result at 100measurements over force gave a low variation.

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  • 3.
    Gradolewski, Dawid
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Bioseco Sp. z. o. o, POL.
    Dziak, Damian
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Kaniecki, Damian
    Bioseco Sp. z. o. o, POL.
    Jaworski, Adam
    Bioseco Sp. z. o. o, POL.
    Skakuj, Michal
    Ekoaviation, POL.
    Kulesza, Wlodek
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    A runway safety system based on vertically oriented stereovision2021In: Sensors, E-ISSN 1424-8220, Vol. 21, no 4, p. 1-25, article id 1464Article in journal (Refereed)
    Abstract [en]

    In 2020, over 10,000 bird strikes were reported in the USA, with average repair costs exceeding $200 million annually, rising to $1.2 billion worldwide. These collisions of avifauna with airplanes pose a significant threat to human safety and wildlife. This article presents a system dedicated to monitoring the space over an airport and is used to localize and identify moving objects. The solution is a stereovision based real-time bird protection system, which uses IoT and distributed computing concepts together with advanced HMI to provide the setup’s flexibility and usability. To create a high degree of customization, a modified stereovision system with freely oriented optical axes is proposed. To provide a market tailored solution affordable for small and medium size airports, a user-driven design methodology is used. The mathematical model is implemented and optimized in MATLAB. The implemented system prototype is verified in a real environment. The quantitative validation of the system performance is carried out using fixed-wing drones with GPS recorders. The results obtained prove the system’s high efficiency for detection and size classification in real-time, as well as a high degree of localization certainty. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

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  • 4.
    Gradolewski, Dawid
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Intema Sp. z o.o., POL.
    Maslowski, Dawid
    Intema Sp Zoo, POL.
    Dziak, Damian
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Jachimczyk, Bartosz
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Mundlamuri, Siva Teja
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Intema Sp Zoo, Siennicka 25a, POL.
    Prakash, Chandran G.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. Intema Sp Zoo, Siennicka 25a, POL.
    Kulesza, Wlodek
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences. University of Social Sciences, POL.
    A Distributed Computing Real-Time Safety System of Collaborative Robot2020In: Elektronika ir Elektrotechnika, ISSN 1392-1215, Vol. 26, no 2, p. 4-14Article in journal (Refereed)
    Abstract [en]

    Robotization has become common in modern factories due to its efficiency and cost-effectiveness. Lots of robots and manipulators share their workspaces with humans what could lead to hazardous situations causing health damage or even death. This article presents a real-time safety system applying the distributed computing paradigm for a collaborative robot. The system consists of detection/sensing modules connected with a server working as decision-making system. Each configurable sensing module pre-processes vision information and then sends to the server the images cropped to new objects extracted from a background. After identifying persons from the images, the decision-making system sends a request to the robot to perform pre-defined action. In the proposed solution, there are indicated three safety zones defined by three different actions on a robot motion. As identification method, state-of-the-art of Machine Learning algorithms, the Histogram of Oriented Gradients (HOG), Viola-Jones, and You Only Look Once (YOLO), have been examined and presented. The industrial environment tests indicated that YOLOv3 algorithm outperformed other solutions in terms of identification capabilities, false positive rate and maximum latency.

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    A Distributed Computing Real-Time Safety System of Collaborative Robot
  • 5. Johansson, Fredrik
    Attacking the Manufacturing Execution System: Leveraging a Programmable Logic Controller on the Shop Floor2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background. Automation in production has become a necessity for producing companies to keep up with the demand created by their customers. One way to automate a process is to use a piece of hardware called a programmable logic controller (PLC). A PLC is a small computer capable of being programmed to process a set of inputs, from e.g. sensors, and create outputs, to e.g. actuators, from that. This eliminates the risk of human errors while at the same time speeding up the production rate of the now near identical products. To improve the automation process on the shop floor and the production process in general a special software system is used. This system is known as the manufacturing execution system (MES), and it is connected to the PLCs and other devices on the shop floor. The MES have different functionalities and one of these is that it can manage instructions. Theses instructions can be aimed to both employees and devices such as the PLCs. Would the MES suffer from an error, e.g. in the instructions sent to the shop floor, the company could suffer from a negative impact both economical and in reputation. Since the PLC is a computer and it is connected to the MES it might be possible to attack the system using the PLC as leverage. Objectives. Examine if it is possible to attack the MES using a PLC as the attack origin. Methods. A literature study was performed to see what types of attacks and vulnerabilities that has been disclosed related to PLCs between 2010 and 2018. Secondly a practical experiment was done, trying to perform attacks targeting the MES. Results. The results are that there are many different types of attacks and vulnerabilities that has been found related to PLCs and the attacks done in the practical experiment failed to induce negative effects in the MES used. Conclusions. The conclusion of the thesis is that two identified PLC attack techniques seems likely to be used to attack the MES layer. The methodology that was used to attack the MES layer in the practical experiment failed to affect the MES in a negative way. However, it was possible to affect the log file of the MES in one of the test cases. So, it does not rule out that other MES types are not vulnerable or that the two PLC attacks identified will not work to affect the MES.

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