Master of Philosophy (M.Phil.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/18727

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item: Thesis-Full-text
Developing a policy framework for the design and manufacture of environmentally sustainable food packaging
(2023) Jagoda SUM; Gamage JR
Food packaging plays a vital role in human existence by eliminating barriers to satisfying food requirements regardless of geography. Since food is a basic requirement of all human beings, a billion-dollar industry has been developed surrounding the food supply chain. Providing protection against chemical (oxygen, moisture, carbon dioxide, etc.), physical (vibration and shock), and biological (insects, microorganisms) agents while facilitating the handling of food items in bulk or in appropriate portions for easy and efficient logistics are the primary requirements of food packaging. Concurrently, the adverse consequences of food packaging have caused higher resource consumption and waste generation. Food packaging contributes to significant plastic waste accumulated in landfills, open environments and oceans. Due to the high contribution to single-use plastic waste, organisations and nations are taking several actions to minimise the environmental burden caused by food packaging. However, limited efforts are being made to introduce systematic frameworks that could help packaging designers and policy developers to design and manufacture food packaging. This research focuses on proposing a policy framework for designing and manufacturing food packaging that oversees the triple bottom line of sustainability; environmental, economic, and social. The initial phase of the study identifies the considerations in the development of food packaging concerning rigid packaging and how sustainability could be numerically represented as a decision support tool. Multiple methods, such as public surveys, questionnaires, and focus group interviews, were used for data collection. Then, Quality Function Deployment (QFD) was used to analyse the data to identify the prioritised set of design considerations. Based on the analysis, different designs were developed and evaluated to identify the product characteristics that would influence the sustainability of food packaging. The next phase focused on developing a policy framework using the results of the from the analysis of the case studies. The design science research (DSR) method was used to develop the framework combining different food packaging aspects and graphically representing them in a diagram. The main outcome of this research is the policy framework for designing and manufacturing food packaging that integrates the three main aspects of food packaging. The proposed framework was modified and validated with expert insight, adding credibility to the research outcome.
item: Thesis-Abstract
Design and development of shape memory alloy based novel actuators for minimally invasive surgeries
(2022) Roshan TAU; Aamarasinghe YWR; Dayananda NWN
This work relates to the design and development of Shape Memory Alloy (SMA) based novel actuators for Minimally Invasive Surgeries (MIS). Compared to conventional open surgery, MIS procedures are favorable and developments are possible towards improving the effectiveness of MIS. Handheld slender instruments used in MIS are with limited degrees of freedom achieved using conventional actuation mechanisms which possess disadvantages in handling, durability, and cost. In this study, an SMA-based approach was considered to improve the operation of an MIS tool effectively. The complex behaviour of SMA led to the investigation of material behaviour before the application-oriented study. SMAs are smart alloys that are capable of remembering a parent shape according to the heat treatment (HT) temperature and aging time providing unique activation temperatures. Commercially available binary SMA material that is known as NiTiNOL was used for the study. NiTiNOL was subjected to different HT conditions and Differential Scanning Calorimetric (DSC) analysis was performed on the resulting material to obtain transformation temperatures. Test results demonstrated the ability to alter activation temperature by varying the HT conditions. Also, the samples were observed under an Optical Microscope (OM) and Scanning Electron Microscope (SEM) to identify morphology and elemental composition by Energy Dispersive X-Ray Spectroscopy (EDX) respectively. Furthermore, an SMA spring actuator element was fabricated using a NiTiNOL wire through a novel fixture to obtain desired spring parameters and geometry. NiTiNOL wire was held in the fixture undergoing a HT at experimented temperatures and aging times. Then, spring actuators were characterized based on maximum attainable force using a specially developed apparatus. A customizable hardware controller and a software interface were developed to set values, monitor temperature, and force output. Using the mentioned apparatus, the controller was validated in both temperature and force feedback controlling modes based on a Proportional-Integral-Derivative (PID) type controller. Two linear actuators were designed and developed using the characterized spring element. Firstly, an actuator was developed based on external heating using a heated fluid and cooled fluid to heat and cool the spring element, respectively. A novel actuator structure was developed to facilitate the spring element with leak-proof assembly and was used as the drive source of a gripper mechanism. Strain gauge-based force sensing and PID-based force feedback controlling methods were introduced to the gripper assembly. The second approach was utilizing a Joule heating-based method for activation which the passing current generates heat due to the inherent resistance of NiTiNOL resulting in an increment in temperature. The actuator was characterized in terms of stroke and then introduced to a laparoscopic retractor application to control the flexion-extension motion. A specially developed apparatus and a software interface are used to control parameters and acquire data. Finally, the retractor tool was characterized in terms of stroke.
item: Thesis-Full-text
Design and development of PZT based micropump for microfluidic applications
(2020) Munas FR; Amarasinghe Y.W.R
The present technical context is promptly growing in implementing onsite microfluidic utensils utilized in microfluidics owing to their great demand. The microfluidics mainly involves in implementing minuscule devices to deal with minute volumes of fluids. Manufacturing these microfluidic devices like micropumps is a great challenge and micropumps are very much indispensable to regulate and convey fluid in minute scale. In this research a PZT based micropump was designed and developed for microfluidic applications. A PZT actuated brass diaphragms and a comprehensive flow arrangement are the important elements of this micropump structure. Basically, the design prominences on a cross junction, engendered by a nozzle jet with a pump chamber and two inlet and an outlet channel respectively. In this sense, the fluid flow rectification is done by nozzle jet feature to expedite the fluid path within the system during every vibration cycle of PZT diaphragm. This micropump device was developed with layer by layer fabrication of polymethyl methacrylate (PMMA) plates using laser cutters and all the layers were squeezed in to attain required structure. In order to recognize the physiognomies of flow and to verify the experimental outcomes with simulated data, numerical simulation analysis in ANSYS were carried out. In addition, the PZT diaphragms were under taken for eigenfrequency study analysis in COMSOL Multiphysics as well. In this sense, the applied frequency of the piezoelectric diaphragms was varied by using the prescribed control system developed for this device. As per the test results, the maximum flow rate of 31.15 ml/min achieved at the frequency of 100 Hz. In addition, the thin film deposition techniques and the thermo elastic damping analysis on PZT actuators were also analyzed to identify the performance enhancement of this micropump. Since monitoring pressure and getting response is vital in microfluidic devices, design and simulation of MEMS based piezoresistive pressure sensor has been carried out. According to the piezoresistive structural coupled field analysis, the optimal diaphragm structure was chosen among three kinds of diaphragms considered for this study. Further, the thermo mechanical behavior of piezoresistive pressure sensors have also been considered in this research. At last, the complete numerical simulation was done for the micropump fluid flow coupled with the designed pressure sensor. According to this analysis, the pressure sensor gives the favorable sensitivity variation over micropump discharge pressure. Hence the developed micropump is not only for a specific application but also worthwhile in a wide range of microfluidic applications.
item: Thesis-Full-text
Development of safe operational criteria for ships based on vibration analysis
(2019) Dasanayaka DMPM; Perera PABAR
The origin of shipboard vibrations is dominantly determined by vessels propulsion system, main machinery, auxiliary systems, pumps, breaking of the waves at the ship hull, etc. All of these peripherals and systems origin the static and dynamic induction of vibration onboard a ship while various analytical and statistical methods may be declared to assess the levels of vibration in order to declare a combined safe operational criteria for ships depending on the spectrums. Few similar researches had been completed on identification and quantified estimation of the noise or the multiple vibrations resulted from ship and machinery during passage. However, those researches were addressed mainly towards developing a relationship for a single new ship or category particularly prior to commissioning. This research was focused on studying the shipboard transferred vibration (of the vessel's structure and to sea) and vibration spectra generated by shipboard machinery / structures using portable vibration analysers for in-service ships. Data was recorded onboard classes of ships/ craft (new and old) through a series of sea trials to establish a common relationship for ships and to comprehend use this methodology as a tool in understanding complex patterns of ship vibration spectra to predict possible defects. The study commenced on 05th May 2014 under the patronage and guidance of the Department of Mechanical Engineering, University of Moratuwa to identify the unique patterns of shipboard vibration signatures generated whilst vessels are on sail, paying attention to the external forces and to develop a data base with existing vibration levels after being identified as safe operational limits (depending on the observations based on datum readings). The research data was collected using two modern vibration analysers (Make: Areva, Model: Oneprod MVP -2C, Country of Origin: France, Frequency Range: 0 – 40,000 Hz) integrated with Areva XPR 300 software system uploaded computers for the spectrum analysing task. Sea trials at following conditions had been carried out. a. Sea State : 3 and below; b. Ship Loading Condition : Full Load, Half Load; c. Wind Condition : Moderate < 15 knots; d. Sea Direction : Ahead, Astern Numerical relationships and probabilities were established using practical outcomes of the sea trials. Data analysis and Spectrum datum comparison were used to identify and quantify the safe operational vibration limits with respect to individual classes of ships being the primary outcome. The similar defect patterns and respective statistics were averaged to find out a common relationship to identify a figure named “Shipboard Machinery Vibration Safety Index (Sv)”, which was the secondary outcome of the study.
item: Thesis-Abstract
Development of an anthropomorphic transhumeral prosthetic arm for upper ...
(2015-09-16) Bandara, DSV; Gopura, RARC; Hemapala, KTMU; Kiguchi, Kazuo
During the past few years there was a rapid development in robotic prosthetic limb technology to be used for the upper limb amputees. Anthropomorphic transhumeral arm prosthesis is proposed in this thesis to assist the activities of daily living of amputees. The prosthesis generates elbow flexion/extension, forearm supination/pronation, wrist ulna/radial deviation, wrist flexion/extension and another 11 DoF at the terminal device. In order to generate the wrist flexion/extension and ulna/radial deviation, a novel wrist mechanism is proposed based on the parallel prismatic manipulators. Two wrist motions occur in two different axes. The wrist design also follows the human anatomical structure. It is expected to realize high speed operation, higher positional accuracy and anthropomorphic features using the proposed mechanism. The arm prosthesis consists of an under-actuated hand as the terminal device with intrinsic actuation. A novel under-actuated mechanism is introduced as the finger designs, except for the thumb. The mechanism is capable of generating 3 DoF for the finger design. It further poses the capability of adjusting the finger joint angles passively, according to the geometry of the grasping object. With the intention of verifying the effectiveness of the mechanisms in motion generation, motion simulation and kinematic analysis are carried out. The results proved that the mechanisms are capable of generating the required DoFs to generate the lost motions of the human upper limb. Several experiments are carried out using the prototype of the arm prosthesis. Experimental results also proved the effectiveness of the proposed mechanisms for expected motion generation. Additionally a parameter to evaluate the finger designs of finger mechanisms is introduced
item: Thesis-Abstract
Development of an upper-limb power-assist exoskeleton robot to generate human like motion
(2015-08-28) Gunasekara, JMP; Gopura, RARC; Jayawardena, TSS
Weakness is inherently associated with ageing society. In fact, Exoskeleton robotic technology can be used to provide assistance for age society to perform activities of daily living (ADL) without depending on others. Upper limb exoskeleton robots are much suitable to perform ADL. Typically, upper limb exoskeleton robot consists of number of joints and links which are corresponding to joints and limbs of human upper limb. Further, exoskeleton robots differ from other conventional robots due to present of close interaction with wearer. In general, two types of interaction can be seen in exoskeleton robots: physical human robot interaction (pHRI) and cognitive human robot interaction (cHRI).Strengthening features of cHRI can be seen on recent developments of upper limb exoskeleton robots. However, there exists a vacuum to identify aspects of pHRI relating to performance of exoskeleton robots. The research work of this thesis is focused to design an upper limb exoskeleton robot for motion assist taking effect of kinematic redundancy. The proposed exoskeleton robot (6- REXOS) has four active degree of freedom (DOF) and two passive DOF in its kinematic chain. Two passive DOF are provided to 6-REXOS by means of flexible bellow coupling and those are positioned at wrist and elbow joint of the 6-REXOS to keep their axes parallel to each other. This configuration enhances kinematic redundancy in 6-REXOS. The effect of redundancy is verified with respect to dexterity measures, such as manipulability index, minimum singular value, and condition number. Further, manipulation of end-effector of 6- REXOS due to kinematic redundancy in operational space is presented base on manipulability ellipsoids. 4DOF kinematic model for human lower arm is proposed in thesis. Manipulability measure of human kinematic model is used to benchmark the performance of 6-REXOS. Different measures are taken into account in design of 6-REXOS to ensure smooth pHRI. Passive compliance of bellow coupling in order to reduce kinematic discrepancy as well as improve the manipulation of 6-REXOS is highlighted in this thesis.
item: Thesis-Abstract
Effect of blade friction on performance of Micro-Hydro pelton turbines : mathematical modeling and experimental verification
(2015-02-08) Atthanayake, IU; Fernando, MARV; Sugathapala, AGT
Water turbines have been used in electricity generation for well over a century. Hydroelectricity now supplies 19% of world electricity and 44% (as at 2012) of Sri Lanka's electricity also comes from hydropower. Micro Hydro is a term used for hydroelectric power installations that typically produce up to 20 kW of power in Sri Lankan context. Many Micro-hydro power plants are operated with Pelton turbines. The main reasons for using Pelton turbines are that they are very simple and relatively cheap. As the stream flow varies, water flow to the turbine can be easily controlled by changing the number of nozzles or by using adjustable nozzles. Since most of the micro hydro Pelton turbines are now manufactured locally, it was revealed that much attention is not paid to the surface finish of the turbine buckets. On the other hand due to sand erosion of turbine parts bucket surface are getting rough day by day. Most of the research that had been done on turbines were focused on improving the performance with particular reference to turbine components such as shaft seals, speed increasers and bearings. There is not much information available on effects of blade/bucket friction on the performance of Pelton turbine. The main objective of this research is to analyze the performance of Micro hydro Pelton turbine particularly with respect to their blade friction. The governing laws of fluid dynamics, relevant to the application were used to develop a theoretical model to estimate the effect of blade friction on Pelton turbine performance. Then the developed mathematical model was validated experimentally. All the experiments are carried out in a Pelton turbine standard test bench. The power developed by the turbine was measured by keeping all the relevant parameters that affect to the power development, constant other than the friction of the bucket. The friction of the buckets was varied by varying surface roughness of the buckets. Different roughnesses of the surface was obtained by pasting various grades of sands one at a time on the surface of the buckets . It was concluded from the developed mathematical model and the experimental testing that power developed by a Pelton turbine increases when the surface roughness of the turbine bucket decreases. It was also proved from the research that splitter thickness of the buckets is also affect the power developed by the turbine. When the thickness of the splitter increases power developed by the turbine decreases. Therefore it is recommended from the study that Pelton turbine buckets must be smooth as much as possible and splitter of the buckets should be as sharp as much as possible to generate more power from a power plant.
item: Thesis-Abstract
Improved rotor design for a small scale horizontal axis wind turbine suitable for low wind potential
(6/17/2011) Narayana, M; Sugathapala, AGT
The design wind speeds of most of the existing wind turbine rotors are in the range of 6 to 15 m/s with cut-in wind speed of 3.5 m/s. The performance of such a wind turbine in Sri Lanka is not satisfactory, where the wind velocities are relatively low. This is due to low initial torque, which leads to difficulty in starting, as well as due to poor running efficiencies. This makes wind turbines less attractive for areas with low wind speeds. The main objectives of this study were to predict the performance of the existing NERDC wind turbine system and identity the main causes for its poor running performance at low wind speed and thereby design a rotor with improved performance. When improve the performance of the rotor to extract more energy from low wind-speeds, cut-in wind speed and design wind speed of wind turbine should be reduced. Low starting torque of wind rotors was identified as a main restriction against the reduction of cut-in wind speed of wind turbines. This study intends to analyse the aerodynamics of wind rotors theoretically and thereby introduces appropriate changes to the geometrical parameters of the blades. Especially, possibility of increase of solidity of the rotor, without effecting adversely on its aerodynamic efficiency was analysed. The blade elementary theory and the momentum theory were used to analyse the aerodynamic performance of rotors theoretically and these results were validated by wind tunnel model testing. The results of this study indicate that the permanent magnet generator and rotor of the NERDC system were not matched properly, which resulted in low overall system efficiency. In addition, the design parameters of the rotor were not appropriate for sites with low wind potential. Other finding of this study was suitable wind rotor for extract more energy from low wine potential, should be· with higher diameter and higher solidity.
item: Thesis-Abstract
Vibration diagnostic of rotor mechanisms in ships
(6/15/2011) Jayarathne, GG; Perera, PABAR; Wimalasiri, WK
In ships, there are so many sources of noise and Vibration such as propulsion engines and electric generators in restricted spaces and structures of ships, which are made of steel, transmit vibration well. By the reasons, noise and vibration of ships are very big by nature and reduction of noise and vibration is important subject for ships. Regarding noise reduction, reduction of noise cause by vibration has difficulty and the major part of such noise is structure born noise. "Vibration" is not a problem. It is a physical manifestation of machinery imperfection. It is used to help find obvious and subtle deviations in machines. No machine runs perfect. "Diagnosis" is the Method of Detection. If, a fault develops and goes undetected, then, at best, the problem will not be too serious and can be remedied quickly and cheaply; at worst, it may result in expensive damage and down-time, injury, or even loss of life. There is no reason or excuse to have machinery operate unprotected. The areas of interest in vibration measuring in plant maintenance are general measurement, analysis, and corrective. All rotor mechanisms in ships consist of shafts, bearings, couplings, gears etc. These machinery operate under various load conditions from light to heavy. Ship propulsion system comparatively works under very heavy load conditions with rolling and pitching of the ship which may tend to cause overstressing of shafts.
item: Thesis-Abstract
Multi criteria measurement and decision model
Sun, YTP
This thesis presents the development of a Productivity measurement model and the use of the Productivity measurement model as an optimisation tool. The project could therefore be divided into two stages and these are: Stage 1: Development of a Productivity measurement model. Stage 2: Optimisation of the Productivity measurement model in order to generate technical parameters. The current Productivity measurement models could be broadly categorised as Quantitative and Qualitative. Each category of the current Productivity measurement models suffer from inherent limitations. The approach suggested is to effectively combine the strengths of Quantitative and qualitative models and evolve a hybrid technique. The intangible criteria of "Effectiveness" and "Efficiency" was defined using several relevant tangible variables and was finally correlated to Productivity using Principal Component analysis (Pf'A). The Productivity measurement model derived, is immensely useful in the following areas: a. Measurement tool to observe trend in productivity. b. Any adverse/favorable change in Productivity could be analysed in depth and the exact cause for the change identified. It could be thus utilised for Productivity Audit. c. Identification of the "top five" tangible variables creating the greatest impact on Productivity. This enables Organisations to set priorities in their Productivity improvement programmes. the final stage, the Productivity measurement model is optimised (using Non Linear programming)in order to generate future target figures for machine failure rates and Effective In the final stage, the productivity measurement model is potimised (using Non Linear Programming) in order to generate future target figures for machine failure rates and Effective utilization of Plant and machinery. An assumption of no capital infusion is maintained throughout the Optimisation exercise. These targets are for the years 1994 and 1995 and their achievement ensures that the objective of the business is optimised.

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