Master of Science in Electronics & Telecommunications

Permanent URI for this collectionhttp://192.248.9.226/handle/123/233

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Browsing Master of Science in Electronics & Telecommunications by Author "Munasinghe, R"

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    item: Thesis-Abstract
    Development of holonomic mobile platform for field robotic applications
    (2014-08-12) De Silva, WR; Munasinghe, R
    Most mobile platforms or vehicles used today are non holonomic. They only have one or two independent degrees of freedom. Due to that its maneuverability is limited and often requires much space to control functions like turning and parking. By improving degrees of freedom (improving the maneuverability) of a vehicle, it can follow many complex trajectories that are difficult or impossible by conventional non holonomic vehicles. Any mobile platform that has three independent degrees of freedom in a plane is a holonomic platform. Independent degrees of freedom means that it can change its orientation or position without effecting other motions unlike in car type vehicles that require turning or changing its orientation when need to move. Holonomic motion is very useful to acquire abilities such as, avoid any obstacle while keeping its orientation the same, capability to move in constrained spaces and track a target while moving in an arbitrary trajectories etc. Because of these advantages and capabilities some of the scientific and industrial researches are targeting to develop holonomic mobile platforms. Already robotics community have managed to build some working models and used in applications like robot soccer games and mobile robot manipulators. Many different mechanisms have been created to achieve the holonomic capability. These include various arrangements of Swedish wheels or omni wheels, chains of spherical or cylindrical wheels, ball wheels and powered caster wheels etc. While most of these designs are practical in indoor environments they are not suitable for outdoor operations in large scale versions. In this research project our goal was to develop a viable design to achieve holonomic capability that minimizes these problems and more suited to outdoor operations. The proposed design has a wheel arrangement similar to a car but with the capability of independent driving and steering capability of each of the four wheels. Car type rolling and steering mechanism avoid any uneven wear of the wheels and avoid lateral forces applied on the wheels. Wheel driving and steering mechanism was designed such a way that wheels can be steered 360 degrees continuously without interfering with the wheel drive system. This enables the platform to move in complex trajectories continuously without stopping for wheel resetting. The developed platform has increased ground clearance that is necessary for outdoor rough terrain operations like farming. Although these benefits exist, controlling the robot to acquire the desired motion is very complex and need innovative algorithm. Four independent wheels with eight degrees of freedoms to achieve three degree of freedom motion is a redundant control problem and require complex control system. Using inverse kinematics model of the platform and multiprocessor design with advance micro-controllers we have tried to solve these issues and were able to achieve successful performance.
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    item: Thesis-Abstract
    High resolution stepper motor controller for tunable laser
    (2015-06-24) Ganeshanathan, V; Munasinghe, R
    Tunable laser systems use stepper motors to rotate the wave selective opticalelements. Stepper motors can rotate with high accuracy and precision. This research focuses on the stepper motor controller, with the feedback to improve the accuracy and the precision of the movement. Sine cosine and trapezoidal current controlling techniques for micro stepping are analyzed, and used in two different types of situations. The variable step interval technique is proposed to overcome the speed variation in the trapezoidal current controlling technique. The proposed controller uses the linear interpolation and sine cosine current controlling technique to improve the rotation accuracy by two times than the resolution of the encoder. The technique is proposed to detect the obstacle by using the encoder and the static characteristic of the stepper motor. The simulation and the experimental results show that proposed controller can produce the required accuracy, the precision and obstacle detection. Also, the movement smoothness could be achieved by variable step intervals. Therefore, proposed controller has better performance to suit the tunable laser system.
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    item: Thesis-Abstract
    Input voltage imbalance compensation in peak current mode controled half bridge converters
    Fernando, LTN; Munasinghe, R
    Instability of the input capacitors’ midpoint voltage has been observed to be one of the major obstacles ofimplementing the peak current mode control in symmetric half bridge converters. Slight variation of the voltage balance in input capacitors may cause serious damages to the operation of the half bridge converter leading total failure ofthe operation ofthe power converter. Some methods have been proposed in various papers some of them includes major changes in the power stage which requires specific application oriented design of some of the basic power stage components (ie: transformer) reducing the availability of components for custom designs. This analysis proposes simple but reliable solution to the aforesaid matter without applying any major modification to the power stage of the half bridge converter circuit and its hardware implementation. This discussion will also extend to analyze various instability phenomena’s possible in the peak current controlled half bridge converter applications in power conversion.
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    item: Thesis-Abstract
    Ukuwela-Polgolla remote telemetry system & forecasting water level of Polgolla Barrage
    Amarasinghe, D; Munasinghe, R
    In this project, a wireless telemetry system was designed and implemented to monitor the water level information of Polgolla barrage from the control room of Ukuwela power station. Using the water level variation, a mathematical algorithm was developed to predict the time to reach minimum / maximum water levels. The wireless telemetry system consists ofthree sub systems. They are I. Data transmitting unit located at Polgolla dam: The water levels are digitized by “Analog Input Modules” and fed the the Telemetry Module. The gate Open / Close status are directly fed to the Telemetry Module serialize these information and send the Data Radio. The Data Radio modulates these information and transmit in to the air. II. The Repeater Station located at Dunuwila: Receives this information and re transit after five seconds. (Store & Forward Repeater) III. Data receiving unit located at Ukuwela Power Station: The information received by Data Radio are sent to the Telemetry Module. It de-multiplexes the information and a) Updates Analog Output modules so that these output modules can re-construct original water level information. b) Outputs gate open / close status through relay contacts. The mathematical algorithm uses two sets of input data. I. Water volume, V(h) vs water level, h ; This is available as a table. II. Water level, h(t); This is given by the above mentioned telemetry system. This model can be run on a personal computer and can be used to estimate the time taken to reach maximum and minimum water level and raise alarms.