Browsing by Author "Munasinghe, R"

Now showing 1 - 20 of 21

item: Conference-Abstract
Aerial Image matching based relative localization of a UAV in urban environments
Chathuranga, TS; Munasinghe, R
This paper presents a method for localizing an Unmanned Aerial Vehicle (UAV) using geo-referenced aerial images, in case of GPS failure. When flying in urban environments in low altitudes the inaccurate GPS localization has become a major problem. The proposed method fuses measurements from inertial sensors and visual odometer and perform image registration process using the images captured by the onboard down looking camera. A pre-built local orthomosaic map with geotagged aerial images is used for the registration. The problem of unreliable matches caused by the dynamic objects is addressed in our approach. The experiment results show that it is possible to localize the UAV in urban environments with a low margin of error by using our method
item: Thesis-Abstract
Analysis of human gait cycle using motion capture
Kumara, HKPM; Munasinghe, R
Bio mechanics is the study of body movements in order to design and produce ideal prosthesis. Biomechanical gait analysis is used widely as an objective tool to evaluate the walking capability of patient before and after various sorts of treatments (e.g. surgery or rehabilitation), design of locomotive apparatus etc. It is therefore important to know the test-retest reliability of each gait analysis, pattern of gait cycle with respect to time and rate of change of angular movements of each joint with respect to the given world reference frame. Irrespective of different expensive and sophisticated system are available such as VICON system, Ariel Performance Analysis System (APAS), we have built the low cost camera calibration system with the elementary stereo geometry in canonical configuration method to gait analysis process in a sagittal plane. The makers' base motion capture methodology was used to analyze the gait cycle with two different speeds. Finally, all the results have taken through the process feed for the graphical illustration of the gait cycle against to time function and hence rate of change of extension and flexion movements, joints accelerations and jerks values during the gait cycle was calculated. Two different speeds have shown that significant change of joint angles and joint velocities in each leg joint. More importantly jerk values which are generating in leg joints shown these differences sharply. In knee and toe joints the generated jerk patterns have shown more noises and which mean that the knee and toe joints are more vulnerable joints during the normal gait of human being. The rate of change of joint angles and joint accelerations with jerk values where it has obtained as the experimental results can be used for future works such as to evaluate and verify the healing process of the patients who have undergone the leg surgeries or lost their normal walking ability. Out of that this will also help to design of artificial limbs to people who has lost their legs due to various accidents.
item: Thesis-Full-text
Design and implementation of a vision based motion capturing apparatus for human gait analysis
Jinadasa, SAP; Munasinghe, R
Walking results from a complicated process involving the brain, spinal cord, peripheral nerves, muscles, bones and joints. Gait analysis is the systematic study of human walking. Gait analysis is often important for clinical gait assessment. Study of biological systems like human walking has paved the way for the development of various biomechanical systems like robot locomotion system. This research proposes a low cost methodology to capture human gait cycle information. As the first step it was required to identify the important movements of the leg during walking. A study of human anatomy and biomechanics enabled this identification. Secondly, it has to be investigated what methodology to be followed to capture identified important movements of the leg during walking. For the study of human gait a spectrum of methodologies are being used throughout the world ranging from the absence of technological aids, at one extreme, to the use of complicated and expensive equipment at the other. Through a study on various techniques used to capture motion, and after comparing these methods it was decided that multi-view marker based system is suitable for the requirement. This vision based methodology had the advantage that it can provide accurate motion information with low cost hardware and readily available software. When the two camera model is selected among other alternatives, it had to be studied how the pixel data obtained from motion capture are converted to the 3D spatial coordinates. Through a series of techniques, camera calibration, stereo calibration and triangulation, conversion of pixel data to 3D spatial coordinates was done. Based on this study the motion capture set up was created and motion capture was done. The results obtained of the two camera model, camera parameters and parameters of the stereo system are presented in this thesis. Validation of the human gait cycle information obtained from this technique was done by comparing this information with gait pattern obtained with more accurate and sophisticated techniques.
item: Thesis-Abstract
Design and simulation of fuzzy inference based multiple PID controllers for 6-dof unmanned underwatter vehicle
Makawita, CD; Munasinghe, R
Unmanned underwater vehicles are currently being utilised for scientific, commercial and military underwater applications. These vehicles require autonomous guidance and control systems in order to perform underwater tasks. Modelling, simulation and control ofthese vehicles are still major active areas ofresearch and development. This thesis explores the design of a control system for a 6-Dof unmanned underwater vehicle. The thesis consists oftwo phases; the first involves the design ofthree single decoupled PID controllers for surge, yaw and depth. Then it is shown that it is not possible to cover the entire range of operations of UUV using only single controller by simulation using MATLAB SIMULINK. The second phase is concerned with the design ofmultiple PID controllers covering the entire range of UUV operation, as well as the fuzzy inference based supervisor design to switch between the different controllers as the operations conditions vary. The design ofthe PID controllers are based on MATLAB PID tuning algorithms which is a robust response time tuning algorithms that allows for faster design process with robust gain values. It is shown that these new tuning methods as well as graphical tuning interface overcome the adhoc and time consuming process offinding the PID gains. Further it is shown that fuzzy gain scheduling using fuzzy inference mechanism is a valid method for controlling a UUV with nonlinear dynamics. It can be concluded that new tools such as MATLAB tuning algorithms and Fuzzy toolbox allows for fast and accurate design of controllers for highly complex systems as well as the viability offuzzy inference multiple controllers as a method for UUV control with desired response characteristics. Finally the author recommends an actual vehicle implementation and testing as future work to be carried out.
item: Conference-Full-text
Development of a quad-rotor fixed-wing hybrid unmanned aerial vehicle
(IEEE, 2018-05) Gunarathna, JK; Munasinghe, R; Chathuranga, D
This paper describes the development of a quadrotor fixed-wing hybrid unmanned aerial vehicle (UAV). By combining the flying qualities of quadrotor UAV and that of fixed-wing UAVs it is possible to achieve superior flying qualities. This way, the vertical take-off and landing capability of quadrotors and the long endurance of fixedwing UAVs have been put together, while eliminating the disadvantages of both of these UAV types. The proposed hybrid drone has shown exciting performance in takingoff, cruising and landing fully autonomously. Control transition from quadrotor to fixed-wing and backwards have been analyzed. Sky Scout fixed-wing drone has been used to build the hybrid UAV, and the performance has been successfully demonstrated through flight tests. This paper precent the complete design of a quadrotor fixed-wing hybrid aerial vehicle with modelling, simulation and experimental verification.
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.
item: Thesis-Abstract
Development of negative pressure wound care system with a novel control concept as an alternative treatment method for non-healing wounds
(2015-07-07) Abeysinghe, GHTS; Munasinghe, R; Wijerathna, M
Negative Pressure Wound Therapy (NPWT) is a noninvasive system that creates a localized, controlled sub atmospheric (negative) pressure environment conducive for wound healing. However, this alternative treatment is yet to acclaim widespread recognition throughout the medical community as a standard treatment method due to the lack of scientifically conducted research data confirming its effectiveness. Most of the available negative pressure wound care systems are of proprietary design and offer limited controls for the medical researcher. The purchase price of the wound care devise as well as the consumables is comparatively high especially for a developing country like Sri Lanka. These factors prove to be a hindrance and limit the possibility of gathering data and carrying out medical research. Our project is aimed at developing a negative pressure wound therapy system which is superior in functionality, yet affordable so that it could be widely adopted it for treatment as well as research purposes. In our effort we were able to develop and successfully implement a novel concept to control a vacuum by controlled injection of atmospheric air into the system. The developed machine automatically generates, monitor and maintain a given negative pressure in and around the wound being treated. Specific emphasis was given for two major factors during the project.  Offering maximum flexibility and ease of operation for carrying out medical research during the clinical trials  Developing a reasonably priced –yet reliable NPWT devise suitable for general use Diabetic patients with resistant ischaemic foot ulcers without granulation were treated during the clinical trials using the devise. Using the new NPWT devise, we tested a pulsating vacuum profile which is generally recommended for wound treatment. The patients were ambulatory and comfortable throughout the duration of negative pressure therapy. A dramatic increase in healthy granulation with reduction in purulence of the exudates and a significant reduction in wound width was noted in all treated wounds. All the wounds were ready for grafting after a treatment period of two weeks thus, proving the suitability of the system for wound treatment.
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.
item: Conference-Abstract
Identifying the cruising dynamics of a medium scale UAV I : longitudinal dynamics
Gamage, CI; Samarasekera, SC; Tennakoon, A; Lalantha, R; Munasinghe, R
Pitch and airspeed responses of a medium scale UAV were identified using the prediction error method. Data collection was conducted with an active closed loop autopilot control system. A naive SISO open loop transfer function was estimated using the parametric direct approach. Since its predictability was not significant, better estimators were developed using MISO parametric direct, and SISO parametric indirect method. The model validations were done to quantify their predictability.
item: Conference-Full-text
Identifying the Cruising Dynamics of a Medium Scale UAV I: Longitudinal Dynamics
(2015-08-03) Gamage, CI; Samarasekera, SC; Tennakoon, A; Lalantha, R; Munasinghe, R
Pitch and airspeed responses of a medium scale UAV were identified using the prediction error method. Data collection was conducted with an active closed loop autopilot control system. A naive SISO open loop transfer function was estimated using the parametric direct approach. Since its predictability was not significant, better estimators were developed using MISO parametric direct, and SISO parametric indirect method. The model validations were done to quantify their predictability.
item: Article-Full-text
Improved state estimation in quadrotor MAVs: A novel drift-free velocity estimator
(IEEE, 2013) Abeywardena, D; Kodagoda, S; Dissanayake, G; Munasinghe, R
quadrotor microaerial vehicles (MAVs) are simple robotic platforms with regard to their construction. In their basic form, they are no more than two counterrotating propeller pairs attached symmetrically to a rigid crosslike frame, along with the means to control the speed of each individual propeller. This symmetric design has enabled the quadrotor to become a simple but powerful vertical takeoff and landing aerial platform popular among the robotics community.
item: Article-Full-text
Indic language computing
(Association for Computing Machinery, 2019) Bhattacharyya, P; Murthy, H; Ranathunga, S; Munasinghe, R
In April 2019, following the Easter Sunday bomb attacks, the Government of Sri Lanka had to shut down Facebook and YouTube for nine days to stop the spreading of hate speech and false news, posted mainly in the local languages Sinhala and Tamil. This came about simply because these social media platforms did not have the capability to detect and warn about the provocative content. India's Ministry of Human Resource Development (MHRD) wants lectures on Swayama and NPTELb—the online teaching platforms—to be translated into all Indian languages. Approximately 2.5 million students use the Swayam lectures on computer science alone. The lectures are in English, which students find difficult to understand. A large number of lectures are manually subtitled in English. Automatic speech recognition and machine translation into Indian languages will be great enablers for the marginalized sections of society.
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.
item: Thesis-Abstract
Linear Stirling Generator Feasibility Study for Distributed Power Generation
(2014-08-06) Gunawardana, KIM; Munindradasa, AMI; Munasinghe, R
The Stirling engine was originally patented 1816 by the Reverend Robert Stirling, and was eighteen years before Carnot's ideas were published. It is a reciprocating engine that has proved reversible both practically and, thermodynamically [l]. The ideal Stirling cycle has the Carnot efficiency [2]. The Stirling engine is a closed cycle external combustion engine that employs a gaseous working fluid inside the engine.
item: Conference-Full-text
motion planning of novel stair-climbing wheelchair for elderly and disabled people
(IEEE, 2020-07) Thamel, SR; Munasinghe, R; Lalitharatne, T; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
This research paper presents a novel track based stair-climbing wheelchair design with improved stability and performance. The proposed design has an adaptable arrangement to the staircase especially at the top of the staircase. In the existing wheelchair designs, this particular feature has not been adequately addressed. The proposed design consists of body frame and supporting rubber track arms. Of the two main operations; ascending and descending, the most critical operations is at the top of the staircase, which is smoothly controlled by following the staircase profile. This motion is achieved by properly synchronizing the rubber track arms according to a pre-planned motion profile. As a result, user does not feel sudden motions in position and attitude. Furthermore, the proposed wheelchair is adaptable to any staircase.
item: Thesis-Abstract
A study of lower limb motions using inertial measurement units
Lalitharathna, SWHMTD; Munasinghe, R
Lower limb motions are vital for human to maintain their everyday life. However, ability ofthe lower limb movements can be affected by different problems. Due to many reasons there large numbers of the population live with various lower limb disabilities. For these people, sometimes it is not an easy task to perform their normal daily life activities. On the other hand, as potential solutions, lower limb prosthetics have been proposed for lower limb amputees and lower limb exoskeletons have been proposed for assisting and rehabilitation processes for the lower limb disabled individuals. However, design and development of the control techniques for such bio-robotics devices is not a straight forward task. Often study and analysis of lower limb motions are important for design and development of the control techniques. Among several methods of studying lower limb motions, Inertial Measurement Units (IMU) based methods have been able to gain lots of attention due several advantages over other methods. Moreover, IMUs can be used in control approaches of bio-robotics applications such as prosthetics or exoskeletons as potential input sources. In this context, the objective of this thesis to study about the lower limb motions using IMUs and investigate the potentials of IMUs to be used in control approaches of bio-robotics applications such as lower-limb prosthetics and exoskeletons. First half ofthis thesis focused on analyzing the human lower-limb motions using IMU sensors mounted over the thigh, shank and foot ofsubjects. IMU sensor data were recorded during walk on horizontal floor, stair ascending and stair descending motions. Comprehensive analyses of lower limb motions were conducted based on recorded accelerometer, gyroscope data of IMUs and sensor fused data. Furthermore, signals from the accelerometer which mounted over the foot were used to detect the heel strike event of the lower limb motions. Based on this heel strike recognition, recorded data were segmented and analyze between each gait cycle. The second half of this thesis, mainly attempted on classification/prediction of walking mode (i.e walk vs stair ascending vs stair descending)and continuous estimation ofthe impaired leg’s foot motions using an IMU mounted over the sound leg’s foot to be used in control approaches of bio-robotics applications such as ankle exoskeletons and lower-limb prosthetics. All the proposed methods were experimentally validated and results highlighted the potential use of IMUs in lower limb motion capturing and control approaches of bio-robotics.
item: Thesis-Full-text
Trajectory planning for 6-DOF robot manipulator based on offline robot programming approach
(2019) Fernando, MDM; Munasinghe, R
Industrial robot manipulators are highly involved in modern manufacturing industries. Robot programming is the procedure to carry out generating a sequence of robot instruction. Teaching method is highly applied where a teach pendent is used to generate the robot programme by teaching one point at a time. This process tends to consume more time and the accuracy can be varied depends on the application. Several other methods are used to program robot movement nevertheless industrial applications of these systems are still developing. Programming tends to be difficult and restricts the productivity and industrial application. Hence, requirement of flexible programming methods is still challenging for inexpert robot operators. Trajectory planning for a robot system is still a developing area where the accuracy, productivity and high quality on various operations are highly concerned. To address these limitations, off-line programming systems can be used where computer systems with realistic graphics, interfaces and features can be used to plan and program robot motions without using robot hardware. The research is aimed to present methods for finding a better mathematical way of optimized trajectory planning of 6-DOF industrial robot manipulator. Computer Aided Design software systems are used to implement off-line programming technique by developing human robot interface in order to create robot moving sequence and achieve required data for further calculations. Welding process of machine head cover using a 6 DOF robot manipulator is used to demonstrate and evaluate the proposed method. Methods for Point allocation along the robot moving path and data extraction are presented. Inverse kinematic model for the 6 DOF manipulator is developed and implemented in order to get joint space data represented by joint angles. Derived data is studied to analyze the manipulator motion behavior while moving along predefined path via points allocated. Robot path planning and trajectory planning with CAD system involvement as off-line programming technique is analyzed by comparing results in order to evaluate the performance of the proposed method.
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.
item: Thesis-Abstract
Universal dynamic simulator for robotic manipulator: dynamics analysis and software development
De Silva, HRPS; Munasinghe, R
A simulation has a very important role in robotics. This research project was focused to develop an efficient universal n link serial link manipulator simulator which can be interacted through graphical user interface with zero code environment using object orient language of Visual C++. This simulator support to wide range of robotics manipulators and computes manipulator links motions under the influence of external forces and internal configuration with sufficient efficiency and allow user interaction.
item: Thesis-Full-text
Universal dynamic simulator for robotic manipulators : kinematic modeling
Kurukularachchi, L; Munasinghe, R
This project highly focuses on a total simulating solution to the robotic manipulator users. The existing simulators are narrow with limited applications. Therefore the simulator users do not have an adequate solution for the universal manipulators. The simulating solution developed through this project is the combination of kinematic, dynamic, trajectory planning and frictional model on a one interface. This project has been divided into four different research components because of the vast extent of the research areas. This thesis is based on the kinematic behavior of this robotic simulator. Under the kinematic behavior, the forward kinematic and the reverse kinematic have been focus on. In the forward kinematic bases, the systematic analytic approaches are used to develop the algorithm. This algorithm describes the spatial relationship between links & link parameters of the manipulator and it supports to find the end-effector position and orientation with respect to the joint space parameters in a graphical way. On the other hand the forward kinematic supports to visualize the manipulator in the 3D environment. The reverse kinematic is required to find a set of joint variables that would bring the end-effector in the specified position and orientation. In general this solution is non-unique for the universal model, but solving the inverse 'kinematic is most important to design the practical manipulators. Therefore the inverse kinematic algorithm is the combination of Jacobian transformation and the Taylor series expansion. This combination is ideal to solve the inverse kinematic in this simulator. The software tool is the final output of this project. -The kinematics module supports to find the manipulator geometry and the joint angles. But the software tool is the combination of kinematics, dynamics and the trajectory planning. The object-oriented program is well adapted to this application since OOP can describe each part of the robot as one object with its own properties and behavior. Even if C++ is not a perfect 00 language, a lot of very useful libraries are available, and maintains very good efficiency for intensive computations. The robotic applications will be highly popular in the future. Therefore this software tool may be most important to develop the manipulator application because it provides a total solution for designing the application. Still nobody has developed this type of an application tool to manipulator designers. This software application operates with out any hindrance and the major advantage is that this simulator can be used for universal serial link manipulator for N-degree of freedom.