Browsing by Author "Marais, Stephen"

Now showing 1 - 11 of 11
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    Design and development of an autonomous duct inspection and mapping robot
    (2008) Booysen, Tracy; Marais, Stephen
    Just a few years ago, the idea of having robots in factories and households was science fiction. But, as robotic technology develops, this is becoming reality. Nowadays, robots not only perform simple household chores, but are used in most production lines and are even employed by the army. Visual inspection robots are very common and are used in many industries, including inspecting the interior of duct systems. Duct systems are in place in almost all large buildings and require ongoing maintenance and cleaning. Systems that are not properly maintained can pose a health risk as dust and mold form and are then blown throughout the building. In some cases, access holes have to be cut to allow access for inspection to occur. A robotic system, small enough to enter a duct through any existing access panel, would be advantageous. An autonomous robot would be even more useful as no operator would be needed thus reducing operating costs. To this end, a robot was developed that could autonomously navigate through a duct system, recoding video images and mapping the internal profile. The development of which is discussed in this thesis, included the design of the robotic platform, the inclusion of appropriate sensors and accompanying circuitry, generation of a simulation to test the control algorithm and implementing embedded software to control the robot. From the testing of the entire system the following conclusions were drawn. The robot as a whole performed well and navigated autonomously through the duct with a success rate of 90%. The system tests were repeatable and the odometry data closely matched the actual paths for straight line travel. The sonar data closely corresponded to the duct walls but was hard to interpret when the odometry and actual paths diverged. These paths diverged from each other due to wheel slip caused as the robot turned. The simulation developed showed that the control algorithm would ensure that the robot recursively inspected any duct system and provided information about the system as a whole. Further work should concentrate on improving the correlation between the odometry path and the actual path, perhaps by adding in a bearing measurement system. Sensors with greater range and accuracy should be implemented and the entire system re-tested. The embedded controller allowed for expansion should additional requirements be needed and was more then adequate for the task.
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    Development of a 6 degree-of-freedom manipulator arm for use on an urban search and rescue robot
    (2012) Henson, Peter MA; Marais, Stephen
    This document reports on the design, construction and testing of the manipulator arm that is to be fitted to UCT's Urban Search and Rescue Robot (USRR), named the Ratel. The 6 degree-of-freedom manipulator arm is mounted on the crawler base. The USRR is designed to traverse difficult terrain in search of survivors. The base is therefore equipped with variable geometry tracks to enable it to traverse stairs and other tricky terrain. The sensor payload is equipped with life detection equipment and the manipulator arm enables the USRR to manipulate with its environment (opening doors etc.) and to interact with survivors, passing them water or food packs.
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    Development of a robotic platform for the exploration of hazardous environments
    (2012) Dreyer, Eugene; Marais, Stephen
    This report documents the research, design, manufacturing, and testing of an Unmanned Ground Vehicle (UGV) robotic platform. Robotic pjatbrms such as these are typically used as Urban Search and Resue (USAR) platforms, as in the World Trade Tower collapses in 2001, however this platform was designed to be a general purpose platform with applications beyond search and rescue. This is the 5th iteration of the platform. It was originally conceived as a platform for transporting mapping equipment into the ore passes or mines. As the project matured it progressed from a solution to this specific problem into a general purpose vehicle for transporting a variety of equipment into variety af hazardous environments. Through the University of Cape Town (UCT) Robotics and Agents Research Laboratory's involvement with the RoboCup Soccer project, the RoboCup Rescue competition emerged as an ideat test bed and development community for this type of platform. While the competition focuses specifically on USAR robots, the test procedures and equipment in use have many possible applications. Papers detailing the design of participating robots were analysed for useful design features and failings to avoid the many stumbling blocks for development of such a platform. Commercial robotic platforms such as the iRobot? Pock Bot were also investigated.
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    The development of localisation capabilities and control for a low-cost robot
    (2008) McWilliams, Kate; Marais, Stephen
    A fully autonomous robot which can perform dangerous or mundane tasks is the ideal outcome of robotic research. A variety of commercially available household robots such as robotic vacuum cleaners exist but are limited in their navigation ability. In general, they tend to use random search patterns to navigate a room and overestimate the time required to clean the room in order to ensure covering the entire area. The ability to map the environment and then use this map to navigate is an essential step towards total autonomy, and would greatly improve the efficiency of these household robots. Autonomous mapping is a complex problem as the robot must use sensor readings to generate a map while at the same time using that map to locate itself and navigate. One component of the mapping task is localisation. This is the process of determining position and orientation from sensor data given a known map. This was the focus of this work as a first-step towards an autonomous mapping robot. This project continued the work of an undergraduate thesis in which a robot vacuum base was built. Using this base, the sensing and control systems were developed. The selection of a suitable controller was an important aspect of the development. It had to be suitable not only for this task but allow for expansion of the control capabilities should the project be extended. The Gumstix/Roboaudiostix embedded system was chosen and performed successfully. Its extremely small size and low power requirements are a feature of the system.
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    The development of the control for an urban search and rescue robot manipulator arm
    (2013) Springer, Bradley Mark; Marais, Stephen
    The University of Cape Town (UCT) Robotics and Agents Research Laboratory (RARL) began research into developing a USAR robot in 2006. The final design of the fourth generation USAR robot developed by UCT [is] named RATEL... This document reports on the research and development of the control for the four degree-of-freedom manipulator arm and pan/tilt system located on the RATEL USAR robot. The report initially discusses control methods used on previously developed teleoperated manipulators in the fields of kinematic modelling, motor control, communications architectures, teleoperative interfaces as well as collision detection and proceeds to discuss the development of the control for the RATEL manipulator.
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    Development of the power distribution system and communications hub for an underwater remotely operated vehicle
    (2014) De Smidt, Roger; Marais, Stephen
    This report details the research, design, development and testing of the third generation underwater remotely operated vehicle (ROV) produced by the University of Cape Town’s Robotics and Agents Research Laboratory (RARL). The ROV was designed and built in response to a request from the Department of Zoology for an ROV to aid their oceanic research. The two generations that had gone before this ROV had provided the research group with good experience, but a new vehicle was required that would offer a more robust research tool for the zoologists and a more versatile platform for future development within the RARL. ROV System Together with project partner Thomas Knight, a new ROV design was developed that was based on the open frame designs commonly used on commercially available ROVs. The ROV was to be propelled by five individual thruster modules and carried four high-powered LED light modules to provide lighting for the ROV’s forward and aft video cameras. In order to navigate the ROV a sonar unit was also incorporated on board. In order to provide power and communications from the surface station to each of the modules on board the ROV, distribution systems for each were required. As the project progressed, it became clear that these distribution systems were critical to the reliability and versatility of the vehicle and became the focus of the author’s scope. The report starts with a description of the design process that resulted in the decision to design a new ROV and then a brief description is provided of the ROV systems incorporated in the final design. The detailed design of the power and communications distribution systems is then presented using a bottom-up design approach, starting with the distribution of power and communications on board the ROV. Brief descriptions of the major components in these systems follow below. Electronics Pod The Electronics Pod (E-Pod) was designed to distribute power to each module on the ROV at the required voltages and currents, and to distribute serial communications to each module over an RS- 485 multi-drop network. The E-Pod incorporated two microcontrollers that were used to control the switching of power to each of the modules and were also connected on the RS-485 communications network. This RS-485 network was connected to the surface via an optical fibre link in the ROV’s tether, and the two converters required to establish this link were also housed in the E-Pod. Video feeds from the on-board cameras were fed into an encoder in the E-Pod and transmitted to the surface controller also via the fibre link. The power required by the E-Pod was drawn from the Power Pod on the ROV, which is described below. Power Pod The Power Pod was designed to convert the 400 VDC supply from the tether into 5 V, 12 V, 15 V and 48 V, which were required by the E-Pod. A total of 1.66kW was to be supplied to the E-Pod so compact, high-power DC-DC converters were integrated into the design of custom-made printed circuit boards (PCBs) in order to provide the required power. Currents sensors, temperature sensors and voltage level sensors were incorporated in the Power Pod circuitry. A microcontroller in the Power Pod was used to read all of the sensors and communicate the values to the surface controller via the E-Pod. Subsea Junction Box Because the ROV’s tether contained copper cores for power transmission and optical fibres for communications transmission, a very expensive hybrid subsea connector was required if it was to plug directly into the Power Pod or E-Pod. A junction box was therefore designed in which the copper cores of tether were separated from the optical fibres. The copper cores were fed to the Power Pod and the optical fibres to the E-Pod. The junction box was filled with oil and pressure compensated to reduce the risk of water ingress. Surface Power Supply Unit Including power losses in the distribution system, 2kW of power was required to be supplied to the tether. A surface power supply unit (PSU) was designed with an isolated, ungrounded 400 VDC power supply, which ran off a standard 230 V, 16 A mains supply. Start and emergency-stop switches were provided on the PSU enclosure, as well as a lockable isolator. The PSU incorporated an Ethernet network switch and fibre optic media converter to provide the link necessary between the tether and the laptop running the user interface and sonar software.
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    EROBOT : a second-generation NDE inspection robot
    (2007) Baldwin, Ian Alan; Marais, Stephen
    Includes bibliographical references (p. 66-69).
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    The further research, development and design of a Robotic Unmanned Ground Vehicle Platform for Urban Search Rescue
    (2013) Lwabona, David Kababa; Marais, Stephen
    This report details the further research, development and design of a Robotic Unmanned Ground Vehicle (UGV) Platform for use in Urban Search And Rescue (USAR). The platform depicted in the figure 0.1 is dubbed Ratel (the Afrikaans name for honey badger) and it is the 5th generation UGV developed in the Robotics and Agents Research Laboratory (RARL) at the University of Cape Town (UCT).
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    Omnidirectional robotic platform : the control of an omnidirectional robotic platform for use in robot soccer
    (2008) Levesque, Sally-Ann; McPhillips, Graeme; Marais, Stephen; Reed, Brandon
    The University of Cape Town competes in a national robot soccer competition. Teams of five small robots compete in the game of soccer without any human intervention. The robots are controlled by the artificial intelligence on a host computer connected to an overhead imaging system. The host computer controls the robots by sending them instructions via wireless communications. The robot soccer platform calls for the integration of electronic, mechanical and computer technologies and provides an exciting area for research. UCT first competed in the robot soccer competition in 2003, using differential drive robots designed by Graeme McPhillips. Research has shown that in the international robot soccer competition, teams are replacing their differential drive robots with omnidirectional robots – robots which can move in any direction without first changing their orientation to face the direction of motion. These robots have proved to be highly manoeuvrable and the winning teams in the small robot league are consistently those that use omnidirectional robots. In 2004, Craig Inman-Bamber designed and implemented UCT’s first omnidirectional robot platform. It is this platform that this dissertation is concerned with controlling. Electronic components were designed and implemented and software code written to control the robot in an omnidirectional manner.
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    Research and development of a rescue robot end-effector
    (2013) Rieger, Michael; Marais, Stephen
    This report details the research, design, development and testing of an end-effector system for use on an Urban Search and Rescue (USAR) robot which is in development in the Robotics and Agents Research Laboratory (RARL) at the University of Cape Town (UCT). This is the 5th generation Mobile Robot Platform (MRP) that UCT has developed ... codenamed ‘Ratel’. USAR robots used to be mainly of the observation type, but new robots (including UCT’s Ratel MRP) are being developed to deal with inherently dynamic, complex and unpredictable disaster response situations, particularly related to object manipulation and gripping. In order to actively interact with the environment, a flexible and robust gripping system is vital. [an] end-effector solution ... was developed for the Ratel manipulator arm to fulfil these functions.
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    Research, design and construction of a team of Small Size League Soccer robots for RoboCup Soccer
    (2013) Pead, Justin Charles; Marais, Stephen
    Small Size League (SSL) Soccer at RoboCup uses the complexity of a well kown human sport to extend the capabilities of mobile robotics as well as automated computer control. The game creates a environment where technically complicated miniature soccer robots are required to perform the tasks based on computer algorithms to outsmart similar systems. SSL creates a publically accessible window into complicated systems that an outsider is capable of comprehending.