https://www.um.edu.mt/library/oar/handle/123456789/5674 2026-04-22T14:43:22Z https://www.um.edu.mt/library/oar/handle/123456789/77494 Title: Modelling and control of urban junctions Abstract: Continuous migration towards major cities around the world has brought an increase in the number of inhabitants in urban areas. With more people using the limited road infrastructure, mobility demands are exceeding the infrastructure capacity leading to increased traffic congestion. To address this problem a model predictive control scheme is developed and tested in this work to control in real time the traffic light timings. The scheme is based on a state space representation of the traffic dynamics through an urban traffic network. The proposed model incorporates a switching mechanism capturing both the nonlinear dynamics of normal traffic conditions and the linear evolution of vehicle queues during junction block-back scenarios. Moreover, while competing models suffer a quadratic increase in computational cost with every added junction, the proposed model exhibits only a linear increase in dimensionality and thus significantly lowers its computational demands. The simulation results from the proposed model are validated against a standard micro-modelling simulation package. A hierarchical control strategy based on this model is developed and tested in this dissertation to control in real time the traffic light timings of multiple urban junctions. The comparative advantages of the hierarchical controller over decentralised control are highlighted through an example. Results will show that with minimal computational power, communication requirements and infrastructure investment, the hierarchical control strategy manages to stabilize the queues on all the links in the network while improving the traffic flow through the network by minimizing the effect of junction block-back. The consistency of the results obtained are highlighted through Monte Carlo runs. Description: M.SC.ENG. 2015-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/77480 Title: Autonomous exploration and mapping with mobile robots Abstract: The discovery of uncharted territories has been one of the greatest and earliest fascinations of mankind. Exploration of unknown environments mostly leads to the creation of a map of the terrain being explored. Robotics finds itself in the midst of the necessity for exploration and mapping. Until recent years, robotic mapping of environments had been performed by manually steering the robot around the environment while it uses its onboard sensors and algorithms to construct a world model. Novel research has revealed techniques through which both the robot navigation during exploration, and the mapping process are performed autonomously. In general, an autonomous exploration and mapping robotic system consists of three main components: Simultaneous Localization and Mapping, SLAM, explo ration and a path planning (motion control) component. SLAM is a process through which the robot creates a model of the physical environment (mapping) while at the same time estimates its location within that map (localization). Moreover, given a current robot location in the map, an exploration strategy decides upon the next best location in the environment that the robot should visit in order to expand its charted territory and improve localization. Finally, the path planning and motion control component is responsible for the safe planning and execution of a path for the robot from its current location to a goal location. This dissertation aims to investigate the state-of-the-art techniques that can be used to design and implement such a robotic system. For this purpose, the research robot, Powerbot™, equipped with Robot Operating System (ROS) - a software development framework for robots - was used. The modularity of the implemented scheme enabled three different exploration strategies to be experimentally validated on Powerbot™, running the same SLAM, path planning and motion control components, in a real-life environment. This work contributes to the robotics community by providing ROS implementations of three exploration strategics. In addition these strategies are validated and compared on a real robot running ROS. The experimental results show that there is a statistically significant difference between the performance of the three strategies. These differences are analysed and discussed in detail in this dissertation. Description: M.SC.ELEC.ENG. 2015-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/5899 Title: A writing and sketching robot Abstract: The use of robotic manipulators has been on the rise for the past couple of years and as a result the interaction between humans and robots has become more commonplace. Robot manipulators have proven to be a very useful tool in a number of situations and have been suitably modified to cater for a multitude of applications. With the advancements in mechanical hardware technology and computational power, a growing body of interest in the development of robot manipulators to perform basic functions of human arm has emerged. One such task is the ability to write or sketch. The main objective of this dissertation is to implement on an industrial manipulator the necessary control schemes in order to allow the manipulator to be able to write or sketch a given trajectory on a flat whiteboard surface using standard markers. In this project, a parallel position/force controller was successfully implemented on a 5 degree of freedom (DOF) anthropomorphic robot manipulator equipped with a force/torque (F/T) sensor system to measure the contact force between the end-effector and the environment. The effectiveness of the implemented controller has been illustrated and verified through a comprehensive series of experiments. Description: B.ENG.(HONS) 2015-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/5898 Title: Object search, recognition and following in a cluttered environment Abstract: The popularity of mobile robots is increasing as we are becoming more aware of how powerful and useful these machines can be in everyday life. Autonomous robots are even more attractive as these can complete jobs assigned to them without the need of any supervision. Such robots should be capable of operating in around cluttered environments without damaging themselves or creating a hazard to humans sharing the same space. This project endeavors to create a system where the mobile robot first searches for a desired object using a vision system, and when the object is found, the robot starts to approach it and at the same time avoid any obstacles lying in its path towards the target. As the robot arrives at a pre-defined distance away from the target object, it stops and if the target moves, the robot is able to continue following it. This whole system consists of a number of algorithms that work harmoniously together to perform multiple tasks depending on the need at that particular circumstance. A thorough study about existing algorithms has been carried out at the start of the project. Some of these algorithms were simulated and studied into more detail. For the ‘search’ task, no existing algorithm which satisfies the requirements could be found and therefore a new algorithm was developed to accommodate all the requirements mainly imposed on the system by the hardware of the robot used. The designed system was successfully implemented on the Khepera III mobile robot. Description: B.ENG.(HONS) 2015-01-01T00:00:00Z