Mechatronics Systems Engineering - Theses, Dissertations, and other Required Graduate Degree Essays

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Design and development of a wearable inductive textile sensor to monitor back movements

Date created: 
2020-11-18
Abstract: 

This thesis focuses on the design and development of a wireless and wearable platform that employs an inductive sensor to track trunk movements when the user bends forward. The inductive textile sensor was designed based on the anthropometrical dimensions of the trunk’s lumbar area of a healthy female. The chosen shape of the sensor was a rectangular flat coil. The inductance behavior was investigated using theoretical calculations and simulations. Formulas developed by Grover and Terman were used to calculate the inductance to validate the inductive textile design. The simulations were used to analyze the change of the inductance when the area, perimeter, height, and width of the rectangle was modified, as well as the effect of the number of turns of the rectangular flat coil. Results from the theoretical calculations and simulations were compared. The inductive textile sensor was integrated at the lumbar section of a sleeveless garment to create a smart wearable platform. The performance of the smart garment was evaluated experimentally on a healthy participant, and it was shown that the designed sensor can detect forward bending movements. The evaluation scenario was further extended to also include twisting and lateral bending of the trunk, and it was observed that the proposed design can successfully discriminate such movements from forward bending of the trunk. An interference test showed that, although moving a cellphone towards the unworn prototype affected the sensor readings, manipulating the cellphone when wearing the prototype, did not compromise the capability of the sensor to detect forward bends. The proposed platform is a promising step towards developing wearable systems to monitor back posture to prevent or treat low back pain associated with poor posture.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Carlo Menon
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

Design of a bidirectional energy buffer using a switched-capacitor converter and supercapacitors for an auxiliary EIS converter for fuel cell stacks

Author: 
Date created: 
2020-10-21
Abstract: 

Fuel cell as an attractive clean energy source has gained a great deal of interest. To increase the durability and reliability of fuel cells, diagnostics systems that can detect degradation and faults inside fuel cell stacks in end applications are highly in need. Electrochemical impedance spectroscopy (EIS), among other methods, is a promising characterizing tool for diagnostics and condition monitoring of fuel cells. It was traditionally only applied to single-cell or short stacks at low-power levels and required special laboratory equipment, but was recently brought to high-power stacks too which was made possible by many technological advancements. This is mainly owing to a growing interest in performing in situ EIS as a non-destructive method without the need for dismantling the stack. Unlike traditional approaches which relied on extra equipment, converter-based EIS provides attractive solutions for this purpose. In this thesis, the design and utilization of a bidirectional energy buffer module composed of a switched-capacitor converter (SCC) and a supercapacitor string for a new auxiliary EIS converter solution is presented. The module is designed towards having a more compact auxiliary converter unit. The design of the proposed energy buffer module is investigated in detail and a guideline is provided considering the application-specific optimal conversion ratio, supercapacitor string capacitance, and the probable limitations imposed by high EIS frequencies on certain situations. In a nutshell, the proposed switched-capacitor converter module (SCCM) consists of a bidirectional high voltage-gain SCC connected with supercapacitor string helps with the compactness and miniaturization of the entire auxiliary EIS converter and eliminating the potential problems of electrolytic capacitors such as bulkiness and limited lifetime due to the impact of ripples. The SCCM energy buffer with a high voltage gain offers a high buffering ratio for utilizing supercapacitors as the energy storage device.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Jiacheng (Jason) Wang
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

PEMFC performance improvement through oxygen starvation prevention, modeling, and diagnosis of hydrogen leakage

Author: 
Date created: 
2020-10-13
Abstract: 

Catalyst degradation results in emerging pinholes in Proton Exchange Membrane Fuel Cells (PEMFCs) and subsequently hydrogen leakage. Oxygen starvation resulting from hydrogen leaks is one of the primary life-limiting factors in PEMFCs. Voltage reduces as a result of oxygen starvation, and the cell performance deteriorates. Starved PEMFCs also work as a hydrogen pump, increasing the amount of hydrogen on the cathode side, resulting in hydrogen emissions. Therefore, it is important to delay the occurrence of oxygen starvation within the Membrane Electrode Assembly (MEA) while simultaneously be able to diagnose the hydrogen crossover through the pinholes. In this work, first, we focus on catalyst configuration as a novel method to prevent oxygen starvation and catalyst degradation. It is hypothesized that the redistribution of the platinum catalyst can increase the maximum current density and prevent oxygen starvation and catalyst degradation. Therefore, a multi-objective optimization problem is defined to maximize fuel cell efficiency and to prevent oxygen starvation in the PEMFC. Results indicate that the maximum current density rises about eight percent, while the maximum PEMFC power density increases by twelve percent. In the next step, a previously developed pseudo two-dimensional model is used to simulate fuel cell behavior in the normal and the starvation mode. This model is developed further to capture the effect of the hydrogen pumping phenomenon and to measure the amount of hydrogen in the outlet of the cathode channel. The results obtained from the model are compared with the experimental data, and validation shows that the proposed model is fast and precise. Next, Machine Learning (ML) estimators are used to first detect whether there is a hydrogen crossover in the fuel cell and second to capture the amount of hydrogen cross over. K Nearest Neighbour (KNN) and Artificial Neural Network (ANN) estimators are chosen for leakage detection and classification. Eventually, a pair of ANN classifier-regressor is chosen to first isolate leaky PEMFCs and then quantify the amount of leakage. The classifier and regressor are both trained on the datasets that are generated by the pseudo two-dimensional model. Different performance indexes are evaluated to assure that the model is not underfitting/overfitting. This ML diagnosis algorithm can be employed as an onboard diagnosis system that can be used to detect and possibly prevent cell reversal failures.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Krishna Vijayaraghavan
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

Development of novel sorber bed heat and mass exchangers for sorption cooling systems

Date created: 
2020-09-09
Abstract: 

The current cooling systems mainly employ vapor compression refrigeration technology, which increases the electricity peak load significantly and has a high carbon footprint. One alternative solution is sorption systems, run by low-grade thermal energy, i.e. heat sources with temperature less than 100 ºC, such as waste heat, which is non-payable. Also, sorption systems have negligible carbon footprint. Despite all the promising features and benefits, current sorption systems are not ready for wide market adoption. A revolutionary approach to their design and development is needed to overcome their technical limitations such as low specific cooling power (SCP) and low coefficient of performance (COP). Graphite flakes were added to the sorbent to increase the sorbent thermal diffusivity; however, it reduces the active sorbent. The counteracting effect of graphite flake additives in the sorbent was studied using a custom-built gravimetric large pressure jump test bed. It was found that graphite flake additives can increase or decrease the sorption performance depending on the cycle time. Furthermore, 2-D analytical models were developed that consider the spatial and temporal variation of water uptake and temperature in sorber bed heat and mass exchangers (S-HMXs). Two designs of plate fin (P-HMX) and finned-tube (F-HMX) were considered because of the high SCP and COP. Using the analytical models, it was shown that the entire S-HMX components should be optimized simultaneously, and the objective functions of SCP and COP should be optimized together. Thus, an analysis of variance and simultaneous multi-objective optimization of the S-HMX components were performed using the developed analytical models. Based on the optimization study, the P-HMX and the F-HMX were specifically designed and built for sorption cooling systems. The experimental results showed that the present P-HMX achieved an SCP of 1,005 W/kg sorbent, and a COP of 0.60 for Tdes=90 °C, Tsorp= Tcond=30 °C and Tevap=15 °C. Furthermore, the F-HMX yielded an SCP of 766 W/kg and COP of 0.55. It was shown that the P-HMX provided 4.3 times higher SCP, and 3 times higher COP compared to an off-the-shelf heat exchanger coated with a similar composite sorbent consisting of CaCl2, silica gel B150 and PVA.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Majid Bahrami
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

4D in situ visualization of chemo-mechanical membrane degradation in fuel cells: Understanding and mitigating edge failures

Author: 
Date created: 
2020-08-17
Abstract: 

Fuel cell is a zero-emission energy conversion device using hydrogen and oxygen to generate power with water as the only by-product. Membrane electrode assembly (MEA) edges are sensitive regions that could influence the overall durability of fuel cells, where membrane degradation at poorly designed edges may lead to premature cell failures. In this work, two MEA edge designs were implemented to study their robustness during combined chemical and mechanical accelerated stress testing. Four-dimensional in situ visualization, enabled by X-ray computed tomography, was performed to understand and mitigate the edge failure issue. Interaction of adhesive-containing polyimide gasket with catalyst coated membrane (CCM) was identified as the key contributor to premature edge failures, which was mitigated by using a non-adhesive inert frame at the CCM interface, thus enabling a robust MEA edge wherein the failures were shifted into the active area. Overall, findings of this research may contribute to robust fuel cell manufacturing and enhanced membrane durability.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Erik Kjeang
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

Towards the vision of a social robot in every home: A navigation strategy via enhanced subsumption architecture

Author: 
Date created: 
2020-06-29
Abstract: 

In this thesis, we report the studies undertaken in the design and implementation of a behavioristic navigation system for social robots with limited sensors to be deployed in family homes. The project was completed in four phases. Each phase of the project was independently evaluated in virtual or real-time implementation on the NAO humanoid robot. In the first phase of this research study, we address the problem of indoor room classification via several convolutional neural network (CNN) architectures. The main objective was to recognize different rooms in a family home. We also propose and examine a combination model of CNN and a multi-binary classifier referred to as Error Correcting Output Code (ECOC). In the second phase, we propose a new dataset referred to as SRIN, which stands for Social Robot Indoor Navigation. This dataset consists of 2D colored images for room classification (termed SRIN-Room) and doorway detection (termed SRIN-Doorway). The main feature of the SRIN dataset is that its images have been purposefully captured for short robots (around 0.5-meter tall). The methodology of collecting SRIN was designed in a way that facilitated generating more samples in the future regardless of where the samples have come from. In phase three, we propose a novel algorithm to detect a door and its orientation in indoor settings from the view of a social robot equipped with only a monocular camera. The proposed system is designed through the integration of several modules, each of which serves a special purpose. Finally, we report an end-to-end navigation system for social robots in family homes. The system combines a reactive-based system and a knowledge-based system with learning capabilities in a meaningful manner for social robot applications.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Ahmad Rad
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

Natural graphite sheet heat sinks for power electronics

Author: 
Date created: 
2020-06-04
Abstract: 

In this thesis, a multi-disciplinary investigation of using natural graphite sheet (NGS) for heat sink applications is presented with focus on thermal performance, electromagnetic performance, reliability, cost, energy efficiency, and environmental impact. NGS heat sinks are a promising alternative for weight-sensitive applications in which the heat sink is protected by a case. Contrary to the conventional metals, NGS is also predicted to be feasible at high temperatures or in corrosive environments. To provide the basis for the heat sink design, the thermal conductivity, thermal diffusivity, electrical conductivity, thermal emissivity, coefficient of thermal expansion, and compression behavior are measured and reported in an easy-to-use form. It is shown experimentally that the the thermal contact resistance at metal-NGS interfaces is comparable to metal-metal ones with thermal interface materials, and that the poor through--plane thermal conductivity can be mitigated by embedding heat pipes in NGS heat sinks. The conducted common-mode electromagnetic emissions cannot be reduced by using NGS heat sinks, but potential to reduce the radiated emission by 12 to 97 % was identified. Complex implications on reliability arising from replacing conventional metal heat sinks with NGS ones are discussed. The cost of NGS heat sinks produced in high volumes is predicted to be a double that of mass-produced conventional aluminum ones. The environmental impact of production, manufacturing, and end-of-life management of NGS is reviewed and compared to the conventional heat sink materials. A case-specific approach to evaluating the feasibility of using NGS heat sinks is recommended and the major steps are outlined. The technology is considered to be ready for a transfer to the industrial research and development stage. An audiovisual summary of the work is available at https://www.youtube.com/playlist?list=PLaX55SIXaD20NQQ2JLP-7abmET7l-6LS4.

Document type: 
Thesis
File(s): 
Video summary: 01 - Introduction
Video summary: 02 - Cooling systems, research motivation and goal
Video summary: 03 - Material properties of natural graphite sheet
Video summary: 04 - Thermal performance of NGS heat sinks
Video Summary: 05 - Electromagnetic performance of NGS heat sinks
Video Summary: 06 - Energy efficiency and environmnental impact
Video summary: 07 - Feasibility of NGS heat sinks
Video summary: 08 - Conclusions
Supervisor(s): 
Majid Bahrami
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) Ph.D.

Design and testing of a novel power-assisted wheelchair system

Author: 
Date created: 
2020-05-25
Abstract: 

A power-assisted wheelchair is a hybrid between a manual and power wheelchair that consists of an electric-assist system that can be easily mounted on a manual wheelchair. These devices have a demonstrated benefit on the health and mobility of wheelchair users. However, current power-assisted wheelchairs are not addressing all user needs, and as a result there is room for improvement. In this thesis, a novel power-assisted wheelchair system was developed using Stanford Design Thinking. Design requirements were developed using ISO 13485. Concept designs were iterated and a prototype was fabricated. The result is the NeuwDrive, a lightweight power-assist system. The NeuwDrive demonstrates novelty through the use of a right-angled geared motor and a hub design that maintains the overall wheelchair width and allows for easy removal of the drive system. The functionality of the NeuwDrive was verified in two ways. First, the performance was tested using an absorption dynamometer to measure torque and speed. The test results were within the specifications of class-leading devices on the market. The weight of the NeuwDrive is 10.2 kg, below any currently available hub-motor products. Second, a focus group with power-assist wheelchair users was conducted to collected end-user feedback. The results were favourable, with participants favouring the low device weight, removable batteries and narrow width of the NeuwDrive. The results of the testing indicate that the NeuwDrive is a novel power-assist system with potential for future development.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Carolyn Sparrey
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

Human gait monitoring using wearable fabric-based strain sensors and deep supervised learning

Author: 
Date created: 
2019-12-05
Abstract: 

Continuous lower body monitoring is an important step for real-time feedback training of runners and in-home rehabilitation assessment. Optical motion capture systems are the gold standards for gait analysis, but they are spatially limited to laboratories. Recently, wearable sensors have gained attention as unobtrusive methods to analyze gait metrics and health conditions. In this study, a wearable system capable of estimating lower body joint angles in sagittal, frontal, and transverse planes during gait was developed. A prototype with fiber strain sensors was fabricated. The positions of the sensors on the pelvis were optimized using a genetic algorithm. A cohort of ten people completed 15 minutes of running at 5 different speeds for gait analysis by our prototype device. The joint angles were estimated by a deep convolutional neural network in inter- and intra-participant scenarios. In intra-participant tests, root mean squared error (RMSE) and normalized root mean squared error (NRMSE) of less than 2.2° and 5.3 %, respectively, were obtained for hip, knee, and ankle joints in sagittal, frontal, and transverse planes. The RMSE and NRMSE in inter-participant tests were less than 6.4° and 10%, respectively, in the sagittal plane. The accuracy of this device and methodology could yield potential applications as a soft wearable device for gait monitoring.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Carlo Menon
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.

Thermal performance of heat and water recovery systems: Role of condensing heat exchanger material

Date created: 
2019-09-11
Abstract: 

There is enormous potential for recovering a significant amount of latent heat at temperatures below 100°C from flue gas of combustion-based heating systems due to the presence of water vapor in their exhaust streams. However, condensation of acids along with water vapor in heat and water recovery systems makes a highly corrosive environment, which is a major challenge and a determining factor in selecting suitable materials for condensing heat exchangers. Despite the low cost and great corrosion-resistant properties of plastics, their relatively low thermal conductivities are not ideal for thermal management systems. it is still uncertain how significantly increasing thermal conductivity of the heat exchanger’s material affects thermal performance of the heat recovery systems. The present study aims to shed light on the effect of the thermal conductivity of a condensing heat exchanger’s material on the thermal performance of the unit. For this purpose, an analytical model is developed to predict the thermal performance of condensing heat exchangers, designed for recovering heat and water from wet flue gas. Further, to validate the model, a custom-designed condensing heat exchanger with replaceable tubes is designed in our lab and tested with 304 stainless-steel tubes and FEP plastic tubes under different inlet conditions. For the range of inlet conditions considered in this study, results show that there is a threshold for the thermal conductivity of the material, at which increasing the conductivity any further does not affect the condensation efficiency notably. It is worthy of note that this threshold, with respect to thermal conductivity of commonly used materials for such heat exchangers, has relatively low magnitude (e.g.~10-15 W"∙" m-1"∙" K-1 for stainless steel). This finding is significantly important as it unlocks the potential of using materials such as plastics and polymers with thermally conductive additives for latent heat recovery from flue gas.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Majid Bahrami
Department: 
Applied Sciences: School of Mechatronic Systems Engineering
Thesis type: 
(Thesis) M.A.Sc.