Doctor of Philosophy (Ph.D.)
http://dl.lib.uom.lk/handle/123/2055
2024-03-28T21:46:37ZDevelopment of a soft linear actuator to use in wearable assistive exosuits
http://dl.lib.uom.lk/handle/123/22105
Development of a soft linear actuator to use in wearable assistive exosuits
Kulasekera AL
Wearable exosuits require flexible, linearly contractile, and lightweight actuators to
provide sufficient force to move the respective limb. This thesis presents the concept,
design, fabrication, experimental performance characterization, and numerical modeling
of two types of respectively thin and low-profile vacuum-driven, soft, linearly
contractile actuators. The proposed soft actuators are made of an inextensible yet flexible
thin-skinned pouch supported by a collapsible skeleton that orients the collapse of
the actuator in the longitudinal axis upon the evacuation of the air within the pouch.
The proposed novel soft, lightweight, contractile actuators are thin (ThinVAc) and lowprofile
(LPVAc). Both these actuators are lightweight (ThinVAc: 0.75 g; LPVAc: 14
g), provide high maximum blocked forces (ThinVAc: 5.2 N; LPVAc: 39 N), provide
maximum stresses similar to that expected from biological muscles (ThinVAc: 184
kPa; LPVAc: 117 kPa) and have high force-to-weight ratios (ThinVAc: 477; LPVAc:
285). The ThinVAc can combine to create multifilament actuators for force scaling.
Combining 15 units of 500 mm ThinVAcs generates a maximum blocked force of 54
N (Max. stress: 62 kPa), 290 times the self-weight. The LPVAc integrates a position
sensor based on an inductive sensor allowing closed-loop control with minimal error at
0.25 Hz. Numerical models for the contraction and blocked force of mono- and multifilament
actuators allow for predicting their behavior independent of external sensors.
The proposed actuators are tested in wearable applications to check their suitability.
The ThinVAc is integrated into a knee rehabilitation assist device, and the LPVAc is
incorporated into a novel mono-articular sit-to-stand transition (StSt) assist exosuit,
helping to reduce muscle activity by 45%. These actuators have the potential to be
integrated into a wide range of assistive devices and orthoses, such as knee or ankle
braces, exoskeletons, and prosthetics, to provide the necessary support for people with
mobility impairments.
2023-01-01T00:00:00ZModeling of ground - level ozone formation in urban air - sheds of Sri Lanka
http://dl.lib.uom.lk/handle/123/21190
Modeling of ground - level ozone formation in urban air - sheds of Sri Lanka
Perera GBS
Physical phenomenon of the relation among ground-level ozone (O
3
), oxides of nitrogen
(NO
X
) and volatile organic compounds (VOC) is governed by complex nonlinear
photochemistry. To predict and control O
3
concentration, it is vital to know, how O
3
concentration changes in response to prescribed changes in source emissions of NO
X
and VOCs. In this research, a theoretical model was developed and validated for
ground-level O
3
formation in urban air-sheds of Sri Lanka. Hourly averaged weekly
results of ambient pollutant concentration data of eleven cities in the base years 2013,
2014 and 2015 in Sri Lanka was assessed and an urban air shed model was developed.
The model was calibrated using influential parameters measured. Then Colombo as the
most complicated urban air-shed in Sri Lanka was analyzed in detail. Model was
validated using measured 24-hour air quality monitoring data from the mobile air
quality monitoring stations at major traffic locations in Colombo in the year 2018 and
2019. Operational schedules of emission sources including train scheduled data,
working hours of the thermal power plants, and vehicle counts were conducted at
identified critical locations in Colombo to investigate the responsible sources. Gases
from the exhaust line of different types of vehicles was collected and analyzed using
Gas Chromatography Mass Spectroscopy (GCMS).
Results confirm that there exist two regimes of NO
X
-VOC-O
3
sensitivity as NO
x
sensitive
regime
and VOC-sensitive regime. The urban air-shed model is capable of
estimating the ground-level steady state ozone concentration (O
3ss
) and contributions
from each regime. The univariate linear regression model using predicted and observed
O
3
values confirmed that O
3ss
concentration was significantly correlated with the
predicted O
3
concentration. Analysis of urban air shed in Colombo also confirms the
predicted and observed O
3ss
concentration were significantly correlated. This research
provides a detailed understanding of photochemical degradation on formation of
ground-level O
3
in urban air-sheds of Sri Lanka and provides critical information for
the scientific community and decision-makers to formulate air pollution mitigation
policies.
2022-01-01T00:00:00ZA framework developed using ergonomic principles and modified per- determined motion time systems ( PMTS ) to increase the opportunities for physically disabled population to work in industry
http://dl.lib.uom.lk/handle/123/16863
A framework developed using ergonomic principles and modified per- determined motion time systems ( PMTS ) to increase the opportunities for physically disabled population to work in industry
Abeykoon KMW
One billion of the world population are estimated to have some form of disability, and governments spend huge amounts of money to provide welfare facilities to protect their rights and make them inclusive. The literature reveals that people with disabilities (PWDs) are willing to work if they are provided with necessary job support. People with only mobility impairments are commonly named as people with physical disabilities (PPDs). It is a subset of PWDs. PPDs can effectively contribute towards economic growth if their residual physical capabilities are correctly identified. However, employers as well as PPDs themselves find it difficult to identify their residual physical capabilities. Work norms explained in Pre-Determined Motion Time Systems (PMTS) such as Method Time Measurement (MTM) is present for the normal people. These work norms assume that the people have normal capabilities and that they do not have any physical disability. However, there are no such work norms developed to cater for the PPDs. Therefore, the aim of the research was to develop a framework to increase the ability of PPDs to work in industry. The objectives were to explore typical manual work-activities (WAs) similar to those prescribed in PMTS that could potentially be carried out by PPDs, with their residual physical capabilities, explore essential range of movement (RM) of each of the body regions/joints required to perform the identified WAs, formulate a framework mapping RMs of each body regions/joints required to perform typical manual WAs and finally to evaluate and validate it for its purpose, user-friendliness and functionality.
In this pursuit, research was carried out in five distinct phases. In the first phase, typical manual WAs were identified that can be performed by upper and lower extremities using industrial engineering experts (n=3). Then, essential RM of each body region/joint required to perform the identified WAs were determined using relevant medical experts (n=9). Orthopaedic surgeons (n=4) then mapped the RMs that are needed to carry out the WAs to form a framework. These three phases used a modified delphi approach for data collection. In the fourth phase, the framework was evaluated for its purpose and user-friendliness by the intended users of the framework (n=22) in different industries. In the fifth and final study, the functionality of the framework was evaluated with PPDs (n=92) and mapped the work capability of a randomly selected sample of PPDs (n=6) using the framework. The results were compared against the WAs that they were engaged in at the time of the study. The developed guide was named as the WARM mapping tool. Ethical clearance was granted from the Medical Research Institute (MRI), Sri Lanka to carry out the study.
This research proposes a novel philosophical work-related capability and limitations analysis tool to help employ PPDs by identifying suitable WAs based on the degree of disability of the body regions/joints in terms of the corresponding RMs. It is a step towards extending the work norms for PPDs. WARM mapping tool has been developed to guide the employers to recruit PPDs to carryout physical work tasks. All that participated in the usability study proved that it is a convenient and simple tool to use. All 22 practitioners also said that it can also be used as a self-assessment tool by the PPDs. The usability was rated over 60% by all the participants. This tool may be used as a platform to decide on the equipment, facilities, procedures and training that the PPDs will need for effective performance in industry.
2020-01-01T00:00:00ZOptimizing energy performance and indoor environmental quality of buildings using energy simulation, generic optimization and computational fluid dynamics
http://dl.lib.uom.lk/handle/123/13674
Optimizing energy performance and indoor environmental quality of buildings using energy simulation, generic optimization and computational fluid dynamics
Bandara, RMPS
A building is a complex system with multiple interacting physical processes taking place simultaneously. Various aspects influence the performance of buildings and the building envelope is one of the major contributors in this regard. Building orientation, Aspect ratio, Window to wall ratio, Location and types of fenestration, Envelope materials and their characteristics etc. can have a major impact on the energy consumption and life cycle cost of buildings. However, the best combination of the said envelope elements for optimizing the performance of buildings is difficult to determine and is not known. Whole building simulation tools are often used in making building performance predictions. Building energy simulation is generally used on a scenario-by-scenario basis, with the designer generating a solution and subsequently having the computer evaluating it. This is however, a slow and a tedious process and only a few cases are evaluated in a large range of scenarios, possibly leading to sub-optimal envelope designs. By coupling a generic optimization tool with a whole building energy simulation tool, it is possible to optimize the performance of buildings by determining the best combination of envelope elements, subject to predefined constraints. First part of the thesis explains optimization of energy performance and life cycle cost of buildings through this methodology. Secondly, drawbacks of whole building simulation tools that lead to issues in energy performance predictions of buildings are discussed in detail. The issues have been addressed by coupling the whole building simulation tool with a computational fluid dynamics tool on a complementary data exchange platform. It is observed that with this approach more reliable building performance predictions can be made. Final section of the thesis discusses on optimizing indoor environmental quality using computational fluid dynamics with respect to identified mechanical ventilation configurations. Model predictions have been validated using a detailed experimental design where computational model predictions closely agree with the actual measurements.