Engineering (Faculty of)

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Now showing 1 - 20 of 7565

0.42 THz Transmitter with Dielectric Resonator Array Antenna
(University of Waterloo, 2019-07-23) Holisaz, Hamed; Safavi-Naeini, Safieddin
Off chip antennas do not occupy the expensive die area, as there is no limitation on their building material, and can be built in any size and shape to match the system requirements, which are all in contrast to on-chip antenna solutions. However, integration of off-chip antennas with Monolithic-Microwave-Integrated Chips (MMIC) and designing a low loss signal transmission from the signal source inside the MMIC to the antenna module is a major challenge and trade off. High resistivity silicon (HRS), is a low cost and extremely low loss material at sub-THz. It has become a prevailing material in fabrication of passive components for THz applications. This work makes use of HRS to build an off-chip Dielectric Resonator Antenna Array Module (DRAAM) to realize a highly efficient transmitter at 420 GHz. This work proposes novel techniques and solutions for design and integration of DRRAM with MMIC as the signal source. A proposed scalable 4×4 antenna structure aligns DRRAM on top of MMIC within 2 μm accuracy through an effortless assembly procedure. DRAAM shows 15.8 dB broadside gain and 0.85 efficiency. DRAs in the DRAAM are differentially excited through aperture coupling. Differential excitation not only inherently provides a mechanism to deliver more power to the antenna, it also removes the additional loss of extra balluns when outputs are differential inside MMIC. In addition, this work proposes a technique to double the radiation power from each DRA. Same radiating mode at 0.42 THz inside every DRA is excited through two separate differential sources. This approach provides an almost loss-less power combining mechanism inside DRA. Two 140_GHz oscillators followed by triplers drive each DRA in the demonstrated 4×4 antenna array. Each oscillator generates 7.2 dBm output power at 140 GHz with -83 dBc/Hz phase noise at 100 KHz and consumes 25 mW of power. An oscillator is followed by a tripler that generates -8 dBm output power at 420 GHz. Oscillator and tripler circuits use a smart layer stack up arrangement for their passive elements where the top metal layer of the die is grounded to comply with the planned integration arrangement. This work shows a novel circuit topology for exciting the antenna element which creates the feed element part of the tuned load for the tripler circuit, therefore eliminates the loss of the transition component, and maximizes the output power delivered to the antenna. The final structure is composed of 32 injection locked oscillators and drives a 4×4 DRAAM achieves 22.8 dBm EIRP.
17-21 GHz Low-Noise Amplifier with Embedded Interference Rejection
(University of Waterloo, 2023-01-06) Jodhka, Tejasvi; Boumaiza, Slim; Nezhad-Ahmadi, Mohammad-Reza
The ever-growing demand for high performance wireless connectivity has led to the development of fifth-generation (5G) wireless communication standards as well as satellite communication (Satcom). Both 5G wireless communications and Satcom use higher carrier frequencies than traditional standards such as 4G and WiFi. While the higher carrier frequencies allow for larger bandwidths and faster data rates, they come with the cost of high free-space path loss. This high loss necessitates the use of active phased array antennas, which can require hundreds of integrated circuits (ICs) designed in Complimentary Metal-Oxide Semiconductor (CMOS) processes. Furthermore, in a future world with ubiquitous 5G wireless base stations and Satcom users, it is conceivable that Satcom receivers can be jammed by high-power Satcom transmitters and 5G signals. Therefore, Satcom phased arrays must be designed for resilience against these sources of interference while supporting high data rates. One of the key components in a Satcom receiver is the low-noise amplifier (LNA). It is responsible for amplifying the weak, noisy signal received from the satellite into a signal with sufficiently high signal-to-noise ratio for demodulation. One possible solution for making the phased array resilient to sources of interference is to embed filtering in the LNA. This thesis presents two LNA designs that employ embedded filtering for resiliency to interference from 5G wireless signals and Satcom transmitters. First, the circuit-level specifications of a 17.7 - 21.2 GHz (K-band) LNA for satellite communication phased array beamformers are derived from the system requirements. Next, the LNA designs are presented. The first LNA is designed to have out-of-band filtering at 24-30 GHz, which corresponds to the bands containing both 5G and Satcom transmitter interferers. The second LNA is designed to have out-of-band filtering at 27-30 GHz, which addresses a different scenario where the Satcom transmitter is the sole source of interference. Both LNAs are implemented in the Global Foundries 130nm 8XP Silicon-Germanium Bipolar CMOS (SiGe BiCMOS) process. A novel transformer feedback notch is introduced that enhances the filtering capabilities of the amplifier. The full electromagnetic simulation of the first LNA shows a peak gain of 28.8 dB, a minimum noise figure of 1.85 dB, and and input 1 dB compression point (IP1dB) greater than -17 dBm between 24 and 30 GHz. The second LNA shows a peak gain of 27.9 dB, a minimum noise figure of 1.78 dB, and an IP1dB greater than -15 dBm between 27 and 30 GHz. Both LNAs meet specifications sufficient for a Satcom receiver at the same time as having resiliency to out-of-band interference sources.
22-32 GHz Low-Noise Amplifier Design in 22-nm CMOS-SOI Technology
(University of Waterloo, 2019-01-29) Cui, Bolun; Long, John
This thesis explores the use of a 22-nm CMOS-SOI technology in the design of a two-stage amplifier which targets wide bandwidth, low noise and modest linearity in the 28 GHz band. A design methodology with a transformer-coupled, noise-matching interstage is presented for minimizing the noise factor of the two-stage amplifier. Furthermore, benefits of interstage noise matching are discussed. Next, a transistor layout for minimizing noise and maintaining sufficient electromigration reliability is described. It is followed by an analysis of transformer configurations and a transformer layout example is depicted. To verify the design methodology, two amplifier prototypes with noise-matching interstage were fabricated. Measurement shows that the first design achieves a peak gain of 20.7 dB and better-than-10-dB input and output return losses within a frequency range of 22.5 to 32.2 GHz. The lowest noise figure of 1.81 dB is achieved within the frequency range. Input IP3 of -13.4 dBm is achieved with the cost of 17.3 mW DC power consumption. When the bias at the back-gate is lowered from 2 V to 0.62 V, the power consumption is decreased to 5.6 mW and the peak gain drops down to 17.9 dB. Minimum noise figure increases from 1.81 to 2.13 dB and input IP3 drops to -14.4 dBm. The folded output stage in the second design improves the input IP3 to -6.7 dBm at the cost of 35 mW total power consumption. The peak gain of the second design is 20.1 dB, and the lowest noise figure of 1.73 dB within a frequency range of 23.8 to 32.4 GHz. Both designs occupy about 0.05 mm2 active area.
27 Stories
(University of Waterloo, 2010-05-20T16:30:35Z) Smith, Laura
Invisible Cities is Italo Calvino’s description, in fifty-five stories of fifty-five cities, of the travels of Marco Polo. Each city is fictitious, but collectively they make up Marco Polo’s Venice. A city is distinct; we know Venice (or Manhattan or London) by its buildings, its landmarks, the nature of the city`s fabric, and by the lives of the citizens who gather, work, and live there. As much as the fabric itself, those citizens are unique to the city’s character. The suburbs that developed around major urban centers are not cultural artifacts, built over centuries from traditions and local practices, but products: predictable, marketable en masse, and relatively interchangeable. Conceived of as the ideal blend of city and country, the suburbs are homogeneous, universally accessible, and familiar; so it is with suburban stories. The Stories here are true. The people, places, and events are all real. Isolated, they would be anecdotes, gossip, or reports; in this case, they may be considered postcards – snapshots of everyday life. As a whole they begin to portray the home of millions of people across North America. The twenty-seven stories of this thesis create a window into lives lived in the edge condition called Suburbia.
2D Digital Filter Implementation on a FPGA
(University of Waterloo, 2011-08-31T18:27:59Z) Tsuei, Danny Teng-Hsiang
The use of two dimensional (2D) digital filters for real-time 2D data processing has found important practical applications in many areas, such as aerial surveillance, satellite imaging and pattern recognition. In the case of military operations, real-time image pro-cessing is extensively used in target acquisition and tracking, automatic target recognition and identi cation, and guidance of autonomous robots. Furthermore, equal opportunities exist in civil industries such as vacuum cleaner path recognition and mapping and car collision detection and avoidance. Many of these applications require dedicated hardware for signal processing. It is not efficient to implement 2D digital filters using a single processor for real-time applications due to the large amount of data. A multiprocessor implementation can be used in order to reduce processing time. Previous work explored several realizations of 2D denominator separable digital filters with minimal throughput delay by utilizing parallel processors. It was shown that regardless of the order of the filter, a throughput delay of one adder and one multiplier can be achieved. The proposed realizations have high regularity due to the nature of the processors. In this thesis, all four realizations are implemented in a Field Programming Gate Array (FPGA) with floating point adders, multipliers and shift registers. The implementation details and design trade-offs are discussed. Simulation results in terms of performance, area and power are compared. From the experimental results, realization four is the ideal candidate for implementation on an Application Specific Integrated Circuit (ASIC) since it has the best performance, dissipates the lowest power, and uses the least amount of logic when compared to other realizations of the same filter size. For a filter size of 5 by 5, realization four can produce a throughput of 16.3 million pixels per second, which is comparable to realization one and about 34% increase in performance compared to realization one and two. For the given filter size, realization four dissipates the same amount of dynamic power as realization one, and roughly 54% less than realization three and 140% less than realization two. Furthermore, area reduction can be applied by converting floating point algorithms to fixed point algorithms. Alternatively, the denormalization and normalization stage of the floating point pipeline can be eliminated and fused together in order to save hardware resources.
2D Material Based PTE Detectors with Room Temperature Operations
(University of Waterloo, 2023-12-21) Xie, Zhemiao; Yeow, John
Real-time, room-temperature operation and self-powered photothermoelectric (PTE) detection emeries are advanced and versatile solutions for various applications. These detectors offer the advantage of not requiring external power sources, making them portable and suitable for remote or low-power environments. Additionally, their ability to operate at room temperature eliminates the need for costly and complex cooling systems, making them more accessible and cost-effective for various industries and research fields. However, issues of massive fabrication, complicated manipulations, long-term stability, and flexibility are concerned with engaging new exploration on PTE detectors with low-dimensional materials. Two-dimensional (2D) materials are emerging as leading ones due to their broadband detection from Terahertz (THz) to ultraviolet (UV), electrical conductivity with a small band gap, and strong polymer affinity for thermoelectrical conversion. This thesis aims at using 2D nanomaterials of graphene and molybdenum carbide (Mo₂C) MXene for exploring new PTE detectors, guiding 2D materials methodology, leading the investigation of polymer composites, and providing insights into various industrial, imaging, and health monitor applications. This thesis introduces three types of room operation and self-powered PTE architectures with 2D nanomaterials. First, we developed a new doped polyaniline (PANI) as the composite material with a few layers of sheets of graphene. Semi-transparent, broadband infrared (IR) detection and robust flexibility features are presented. Second, a vertical graphene/polyethylenimine (PEI) composite multi-element H-shaped detector with the spray-coating method is presented. High response time, detectivity, and a broadly responsive range are achieved with PEI concentration adjustment, lowering the thermal conductivity and enhancing compacity, focusing the realistic situations with low incident power. Finally, we propose a low-noise PTE device that operates at room temperature by Mo₂C and Poly(3,4-ethylene-dioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) nanomaterials with a flexible PET substrate. Superior energy conversion and long-term stability of the material and sustainability from surroundings are achieved through material optimizations. Based on such PTE detectors, two promising systems—the motion tracking system and the non-destructive testing (NDT) imaging system—demonstrate the time-tracking of human radiation and high-resolution imaging applications.
36 Stratagems Towards a People's Modernity
(University of Waterloo, 2009-09-17T14:56:40Z) Chau, Tammy Sau-Lyn
The design thesis is sited along the Shanghai Bund in China. It pursues an alternative modernity that is quintessentially Chinese by developing a design approach specific to the local imperatives and the contextual condition. The argument is set upon the premise of an accommodative nature of Chinese modernity towards foreign influences since the 1850’s. The Bund, being the original site of Chinese modernity, is characterized by hybrid structures that combine the local and the foreign. Imported building materials, techniques, and proportional ideals have predominately influenced the architecture. Against this backdrop, the thesis problematizes Shanghai’s building practice that pertains to the adoption of foreign forms. Is it possible to create an alternative modernity that is quintessentially Chinese? The thesis first examines the development of the city’s modernity, traditional construction principles, and narratives inherent to the site. Program components are then reorganized for tactical design applications. It concludes with a time-based and event-driven collective space that seeds participation towards a local modernity.
A 37-40 GHz Dual-Polarized 16-Element Phased-Array Antenna with Near-Field Probes
(University of Waterloo, 2022-09-21) He, Ziran; Boumaiza, Slim
With the development of fifth-generation (5G) communication networks, in order to meet the growing demand for high-speed and low-latency wireless communication services, channel capacity has become the main driving force for choosing millimeter wave (mm-wave) over over-crowded sub-6 GHz frequency bands. Recently, beamforming phased array attracts significant research efforts as it is a promising solution and unique in its ability to overcome the high path-loss at high frequency, provide fast beam steering and deliver better user-ends experience. However, to alleviate the issues that associated with beamforming phased array, such as imbalance between array elements and non-linearity caused by power-amplifiers (PAs) in beamforming channels, far-field (FF) based array calibration and digital pre-distortion (DPD) need to be performed, which is not practical in real world scenario. This thesis presents a low-cost 16-element dual-polarized mm-wave antenna-on-printed circuit board (PCB) transmitter RF beamforming array with embedded near-field probes (NFPs) at 37-40 GHz. The elements are orthogonal, proximity-coupled feed dual-polarized patch antenna with a spacing of 0.5λ within 2x2 subarray and 0.6λ between 2x2 subarray at 38.5 GHz, resulting in maximum 17.7 dB gain with a scan angle of +/-50◦, +/-20◦ in azimuth and +/-20◦, +/-50◦ in elevation for vertical polarization and horizontal polarization, respectively. Without affecting phased array performance, the NFPs achieve flat and comparable coupling magnitude and group delay to the closet RF chain for both polarizations, across operating frequency range. This ensures the quality of received output signal from phased array to implement array calibration and DPD. The configuration of embedded NFPs maintains the scalability of phased array and eliminate the needs of impractical FF reference probe for array calibration and DPD.
The 38th Parallel: Penetrating the Line
(University of Waterloo, 2007-09-20T21:37:23Z) Oh, Juhee
In July 1953, the armistice ended the Korean War that lasted for three years and established the Demilitarized Zone on either side of the demarcation line as a buffer between the two countries to prevent further military confrontation. However, the two sides remain at odds for half a century, and, despite the armistice, a state of war still exists between the two Koreas. As Koreans have dreamed of a united nation, the division has been described as a ‘temporary’ term to Koreans, yet the process of it has been much more obscure. Half a century has passed by, and South Korea has become a nation in which all facets of economic, political, and cultural identity are delineated in opposition to North Korea. What the future was supposed to present to Koreans has shifted relentlessly creating a disparity between the individual and national dreams. With repetitive see-saw events of national tension and reconciliation, individuals find themselves in an ambivalent position between series of oppositions: people and state, real and unreal, unification and national division. Multiple narratives crossover, creating confusion of whether the ultimate dream of Korea is even appropriate. The thesis examines the two opposing conditions: the idealized dream of homogeneity, and the factual reality of heterogeneity. Four series of investigations are presented in this thesis: the condition, the cause, the response, and the location of the individual. First, the disparity between the two Koreas illustrates the external conditions of the situation. Then an investigation of the Korean identity is presented to analyze the cause of the condition. The indigenous identity of Korea and the desire to preserve it are presented as the creative forces behind the dichotomy of Korea. The ambivalence of the individual is understood as a response such conditions. The concept of ‘Han’ is employed as a possible vehicle of understanding Korean cultural despondency. Finally the design exploration of a very significant archaeological site in the Demilitarized Zone is undertaken in order to mediate the disparity between the Korean dream and reality for the individual. The design is intended to locate the individual within the Korean pathology. Playing on the previously studied Korean conditions, the design is an amplified display of the opposing conditions which will enable the individual to face the ambivalence of today’s Korea. The thesis does not suggest the solution or envision the end but aims to meditate and negotiate the present moment. It is not my intention to force either fantasy or reality as an absolute answer, but to create an understanding of both conditions in hopes that Koreans can start to break their ambivalence regarding their national reunification.
A 39GHz Balanced Power Amplifier with Enhanced Linearity in 45 nm SOI CMOS
(University of Waterloo, 2022-09-20) Ma, Haien; Boumaiza, Slim
With the high data rate communication systems that come with fifth-generation (5G) mobile networks, the shift of operation to millimeter-wave frequency becomes inevitable. The expected data rate in 5G is significantly improved over 4G by utilizing the large available channel bandwidth at millimeter wave frequencies and complex data modulation schemes. With this increase in operation frequency, many new challenges arise and research efforts are made to tackle them. Among them, the phased array system is one of the hottest topics as it can be made use of to improve the link budget and overcome the path loss challenge at these frequencies. As the last circuit component in the transmitter's front-end right before the antenna, the power amplifier (PA) is one of the most crucial components with significant effects on overall system performance. Many of the traditional challenges of CMOS PA design such as output power and efficiency, are now compounded with the additional challenges that are imposed on complementary metal-oxide semiconductor (CMOS) PAs in millimeter wave phased array systems. This thesis presents a balanced power amplifier design with enhanced linearity in GlobalFoundries' 45nm silicon-on-insulator (SOI) CMOS technology. By using the balanced topology with each stage terminating with a differential 2-stacked architecture, the PA achieves saturated output power of over 21 dBm. Each of the two identical sub-PAs in the balanced topology uses 2-stage topology with driver and PA co-design method. The linearity is enhanced through careful choice of biasing point and a strategic inter-stage matching network design methodology, resulting in amplitude-to-phase distortion below 1 degree up to the output 1dB compression level of over 19 dBm. The balanced amplifier topology significantly reduces the PA performance variation over mismatched load impedance at the output, thus improving the PA performance over different antenna active impedance caused by varying phased array beam-steering angles. In addition to this, the balanced topology also optimizes the PA input and output return loss, giving a better matching than -20 dB at both input and output, and minimizing the risk of potential issues and performance degradation in the system integration phase. Lastly, the compact transformer based matching networks and quadrature hybrids reduce the chip area occupation of this PA, resulting in a compact design with competitive performance.
3D bioprinting of liver-mimetic construct with alginate/cellulose nanocrystal hybrid bioink
(Elsevier, 2018-03-01) Wu, Yun; Lin, Zhi Yuan (William); Wenger, Andrew; Tam, Kam C.; Tang, Xiaowu (Shirley)
3D bioprinting is a novel platform for engineering complex, three-dimensional (3D) tissues that mimic real ones. The development of hybrid bioinks is a viable strategy that integrates the desirable properties of the constituents. In this work, we present a hybrid bioink composed of alginate and cellulose nanocrystals (CNCs) and explore its suitability for extrusion-based bioprinting. This bioink possesses excellent shear-thinning property, can be easily extruded through the nozzle, and provides good initial shape fidelity. It has been demonstrated that the viscosities during extrusion were at least two orders of magnitude lower than those at small shear rates, enabling the bioinks to be extruded through the nozzle (100µm inner diameter) readily without clogging. This bioink was then used to print a liver-mimetic honeycomb 3D structure containing fibroblast and hepatoma cells. The structures were crosslinked with CaCl2 and incubated and cultured for 3 days. It was found that the bioprinting process resulted in minimal cell damage making the alginate/CNC hybrid bioink an attractive bioprinting material.
A 3D ellipsoidal volumetric foot–ground contact model for forward dynamics
(Springer, 2018-04-01) Brown, Peter; McPhee, John
Foot–ground contact models are an important part of forward dynamic biomechanic models, particularly those used to model gait, and have many challenges associated with them. Contact models can dramatically increase the complexity of the multibody system equations, especially if the contact surface is relatively large or conforming. Since foot–ground contact has a large potential contact area, creating a computationally efficient model is challenging. This is particularly problematic in predictive simulations, which may determine optimal performance by running a model simulation thousands of times. An ideal contact model must find a balance between accuracy for large, conforming surfaces, and computational efficiency.Volumetric contact modelling is explored as a computationally efficient model for foot–ground contact. Previous foot models have used volumetric contact before, but were limited to 2D motion and approximated the surfaces as spheres or 2D shapes. The model presented here improves on current work by using ellipsoid contact geometry and considering 3D motion and geometry. A gait experiment was used to parametrise and validate the model. The model ran over 100 times faster than real-time (in an inverse simulation at 128 fps) and matched experimental normal force and centre of pressure location with less than 7% root-mean-square error.In most gait studies, only the net reaction forces, centre of pressure, and body motions are recorded and used to identify parameters. In this study, contact pressure was also recorded and used as a part of the identification, which was found to increase parameter optimisation time from 10 to 164 s (due to the additional time needed to calculate the pressure distribution) but helped the results converge to a more realistic model. The model matched experimental pressures with 33–45% root-mean-square error, though some of this was due to measurement errors.The same parametrisation was done with friction included in the foot model. It was determined that the velocity-based friction model that was used was inappropriate for use in an inverse-dynamics simulation. Attempting to optimise the model to match experimental friction resulted in a poor match to the experimental friction forces, inaccurate values for the coefficient of friction, and a poorer match to the experimental normal force.
3D Ground Truth Generation Using Pre-Trained Deep Neural Networks
(University of Waterloo, 2019-05-24) Lee, Jungwook; Waslander, Steven
Training 3D object detectors on publicly available data has been limited to small datasets due to the large amount of effort required to generate annotations. The difficulty of labeling in 3D using 2.5D sensors, such as LIDAR, is attributed to the high spatial reasoning skills required to deal with occlusion and partial viewpoints. Additionally, the current methods to label 3D objects are cognitively demanding due to frequent task switching. Reducing both task complexity and the amount of task switching done by annotators is key to reducing the effort and time required to generate 3D bounding box annotations. We therefore seek to reduce the burden on the annotators by leveraging existing 3D object detectors using deep neural networks. This work introduces a novel ground truth generation method that combines human supervision with pre-trained neural networks to generate per-instance 3D point cloud seg- mentation, 3D bounding boxes, and class annotations. The annotators provide object anchor clicks which behave as a seed to generate instance segmentation results in 3D. The points belonging to each instance are then used to regress object centroids, bounding box dimensions, and object orientation. The deep neural network model used to generate the segmentation masks and bounding box parameters is based on the PointNet architecture. We develop our approach with reliance on the KITTI dataset to analyze the quality of the generated ground truth. The neural network model is trained on KITTI training split and the 3D bounding box outputs are generated using annotation clicks collected from the validation split. The validation split of KITTI detection dataset contains 3712 frames of pointcloud and image scenes and it took 16.35 hours to label with the following method. Based on these results, our approach is 19 times faster than the latest published 3D object annotation scheme. Additionally, it is found that the annotators spent less time per object as the number of objects in the scenes increase, making it a very efficient for multi-object labeling. Furthermore, the quality of the generated 3D bounding boxes, using the labeling method, is compared against the KITTI ground truth. It is shown that the model performs on par with the current state-of-the-art 3D detectors and the labeling procedure does not negatively impact the output quality of the bounding boxes. Lastly, the proposed scheme is applied to previously unseen data from the Autonomoose self-driving vehicle to demonstrate generalization capabilities of the network.
3D MEMS Microassembly
(University of Waterloo, 2008-09-03T17:52:49Z) Do, Chau
Due to the potential uses and advantages of 3D microelectromechanical systems (MEMS), research has been ongoing to advance the field. The intention of my reasearch is to explore different gripper designs and their interaction with corresponding components to establish a 3D microassembly system. In order to meet these goals, two grippers were designed using different mechanisms for grasping. At the same time, corresponding parts capable of being constructed into a 3D microstructure were designed to interact with the grippers. The microcomponents were fabricated using PolyMUMPS, a part of the Multi-User MEMS Processes (MUMPS), and experimentation was conducted with the goal of constructing a 3D microstructure. The results were partially successful in that both grippers were able to pick up corresonponding parts and bring them out of plane in order to make them stand up. However, a final 3D microstructure was unfortunately not achieved due to time constraints. This will be left to future researchers who continue the project. On the equpiment side a microassembly system was fully integrated using cameras for vision and motors with micro-resolution for movement. A computer program was used to control each part of the system. The cameras provided feedback from various views, allowing the operator to observe what was happening to the microcomponents. The grippers were attached to one of the motors and manipulated to pick up the parts. The final overall system proved sufficient for microassembly, but had some areas that could be improved upon.
3D Mesh and Pose Recovery of a Foot from Single Image
(University of Waterloo, 2022-01-18) Boismenu-Quenneville, Frédéric; Zelek, John
The pandemic and the major shift to online shopping has highlighted the current difficulties in getting proper sizing for clothing and shoes. Being able to accurately measure shoes using readily available smartphones would help in minimizing returns and trying to get a better fit. Being able to reconstruct the 3D geometry of a foot irregardless of the foot pose using a smartphone would help for the online shoe shopping experience. Usually, systems reconstructing a 3D foot require the foot to be in a canonical pose or require multiple perspectives. There is no system to our knowledge that allows capturing the precise pose of the foot without expensive equipment. In many situations, the canonical pose or the multiple views are not feasible. Therefore, we propose a system that can infer the 3D reconstruction and the pose estimation of the foot from any pose in only one image. Our kinematic model, based on popular biomechanical models, is made of 18 rotating joints. To obtain the 3D reconstruction, we extract the silhouette of the foot and its joint landmarks from the image space. From the silhouette and the relation between each joint landmark, we can define the shape of the 3D mesh. Most 3D reconstruction algorithms work with up-convolutions which do not preserve the global information of the reconstructed object. Using a template mesh model of the foot and a spatial convolution network designed to learn from sparse data, we are able to recover the local features without losing sight of the global information. To develop the template mesh, we deformed the meshes of a dataset of 3D feet so they can be used to design a PCA model. The template mesh is the PCA model with no variance added to its components. To obtain the 3D pose, we have labelled the vertices of the template mesh according to the joints of our kinematic model. Those labels can be used to estimate the 3D pose from the 3D reconstruction by corresponding the two meshes. To be able to train the system, we needed a good dataset. Since, there was no viable one available, we decided to create our own dataset by using the previously described PCA model of the foot to generate random 3D meshes of feet. We used mesh deformation and inverse kinematics to capture the feet in different poses. Our system showed a good ability to generate detailed feet. However, we could not predict a reliable length and width for each foot since our virtual dataset does not support scaling indications of any kind, other than the ground truths. Our experiments led to an average error of 13.65 mm on the length and 5.72 mm on the width, which is too high to recommend footwear. To ameliorate the performance of our system, the 2D joints detection method could be modified to use the structure of the foot described by our kinematic foot model as a guide to detect more accurately the position of the joints. The loss functions used for 3D reconstruction should also be revisited to generate more reliable reconstructions.
3D Motion Planning using Kinodynamically Feasible Motion Primitives in Unknown Environments
(University of Waterloo, 2011-09-01T14:31:18Z) Chen, Peiyi
Autonomous vehicles are a great asset to society by helping perform many dangerous or tedious tasks. They have already been successfully employed for many practical applications, such as search and rescue, automated surveillance, exploration and mapping, sample collection, and remote inspection. In order to perform most tasks autonomously, the vehicle must be able to safely and efficiently navigate through its environment. The algorithms and techniques that allow an autonomous vehicle to find traversable paths to its destination defines the set of problems in robotics known as motion planning. This thesis presents a new motion planner that is capable of finding collision-free paths through an unknown environment while satisfying the kinodynamic constraints of the vehicle. This is done using a two step process. In the first step, a collision-free path is generated using a modified Probabilistic Roadmap (PRM) based planner by assuming unexplored areas are obstacle-free. As obstacles are detected, the planner will replan the path as necessary to ensure that it remains collision-free. In complex environments, it is often necessary to increase the size of the PRM graph during the replanning step so that the graph remains connected. However, this causes the algorithm to slow down significantly over time. To mitigate these issues, the novel local sampling and PRM regeneration techniques are used to increase the computational efficiency of the replanning step. The local sampling technique biases the search towards the neighborhood of the obstacle blocking the path. This encourages the planner to generate small detours around the obstacle instead of rerouting the whole path. The PRM regeneration technique is used to remove all non-critical nodes from the PRM graph. This is used to bound the size of the PRM graph so that it does not grow increasingly large over time. In the second step, the collision-free path is transformed into a series of kinodynamically feasible motion primitives using two novel algorithms: the heuristic re-sampling algorithm and the transformation algorithm. The heuristic re-sampling algorithm is a greedy heuristic algorithm that increases the clearance around the path while removing redundant segments. This algorithm can be applied to any piece-wise linear path, and is guaranteed to produce a solution that is at least as good as the initial path. The transformation algorithm is a method to convert a path into a series of kinodynamically feasible motion primitives. It is extremely efficient computationally, and can be applied to any piece-wise linear path. To achieve good computational performance with PRM based planners, it is necessary to use sampling strategies that can efficiently form connected graphs through narrow and complex regions of the configuration space. Many proposed sampling methods attempt to bias the sample density in favor of these difficult to connect areas. However, these methods do not distinguish between samples that lie inside narrow passages and those that lie along convex borders. The orthogonal bridge test is a novel sampling technique that can identify and reject samples that lie along convex borders. This allows connected PRM graphs to be constructed with fewer nodes, which leads to less collision checking and reduced runtimes. The presented algorithms are experimentally verified using an AR.Drone quadrotor unmanned aerial vehicle (UAV) and a custom built skid-steer unmanned ground vehicle (UGV). Using a simple kinematic model and a basic position controller, the AR.Drone is able to traverse a series of motion primitives with less than 0.3 m of crosstrack error. The skid-steer UGV is able to navigate through unknown environments filled with obstacles to reach a desired destination. Furthermore, the observed runtimes of the proposed motion planner suggest that it is fully capable of computing solution paths online. This is an important result, because online computation is necessary for efficient autonomous operations and it can not be achieved with many existing kinodynamic motion planners.
3D N-doped hybrid architectures assembled from 0D T-Nb2O5 embedded in carbon microtubes toward high-rate Li-ion capacitors
(Elsevier, 2019-02) Tolami Hemmati, Sahar; Li, Ge; Wang, Xiaolei; Ding, Yuanli; Pei, Yu; Yu, Aiping; Chen, Zhongwei
Herein, a unique nitrogen-doped T-Nb2O5/tubular carbon hybrid structure in which T-Nb2O5 nanoparticles are homogeneously embedded in an in-situ formed nitrogen-doped microtubular carbon is synthesized, utilizing a facile and innovative synthesis strategy. This structure addresses the poor electron conductivity and rate capability that hinder T-Nb2O5's promise as an anode for Li-ion devices. Such a distinctive structure possesses a robust framework that has ultrasmall active nanocomponents encapsulated in highly conductive carbon scaffold with hollow interior and abundant voids, enabling fast electron/ion transport and electrolyte penetration. Moreover, nitrogen-doping not only ameliorates the electronic conductivity of the heterostructure, but also induces pseudocapacitance mechanism. When evaluated in a half-cell, the as-prepared material delivers a specific capacitance of 370 F g−1 at 0.1 A g−1 within 1–3 V vs. Li/Li+ and excellent cyclability over 1100 cycles. A high energy density of 86.6 W h kg−1 and high power density of 6.09 kW kg−1 are realized. Additionally, a capacitance retention as high as 81% after 3500 cycles is achieved in an Li-ion Capacitor (LIC) with activated carbon as the cathode and nitrogen-doped T-Nb2O5/tubular carbon as the anode.
3D optical metrology by digital moiré: Pixel-wise calibration refinement, grid removal, and temporal phase unwrapping
(University of Waterloo, 2017-01-24) Mohammadi, Fatemeh; Kofman, Jonathan
Fast, accurate three dimensional (3D) optical metrology has diverse applications in object and environment modelling. Structured-lighting techniques allow non-contacting 3D surface-shape measurement by projecting patterns of light onto an object surface, capturing images of the deformed patterns, and computing the 3D surface geometry from the captured 2D images. However, motion artifacts can still be a problem with high-speed surface-motion especially with increasing demand for higher measurement resolution and accuracy. To avoid motion artifacts, fast 2D image acquisition of projected patterns is required. Fast multi-pattern projection and minimization of the number of projected patterns are two approaches for dynamic object measurement. To achieve a higher rate of switching frames, fast multi-pattern projection techniques require costly projector hardware modification or new designs of projection systems to increase the projection rate beyond the capabilities of off-the-shelf projectors. Even if these disadvantages were acceptable (higher cost, complex hardware), and even if the rate of acquisition achievable with current systems were fast enough to avoid errors, minimization of the number of captured frames required will still contribute to reduce further the effect of object motion on measurement accuracy and to enable capture of higher object dynamics. Development of an optical 3D metrology method that minimizes the number of projected patterns while maintaining accurate 3D surface-shape measurement of objects with continuous and discontinuous surface geometry has remained a challenge. Capture of a single image-frame instead of multiple frames would be advantageous for measuring moving or deforming objects. Since accurate measurement generally requires multiple phase-shifted images, imbedding multiple patterns into a single projected composite pattern is one approach to achieve accurate single-frame 3D surface-shape measurement. The main limitations of existing single-frame methods based on composite patterns are poor resolution, small range of gray-level intensity due to collection of multiple patterns in one image, and degradation of the extracted patterns because of modulation and demodulation processes on the captured composite pattern image. To benefit from the advantages of multi-pattern projection of phase-shifted fringes and single-frame techniques, without combining phase-shifted patterns into one frame, digital moiré was used. Moiré patterns are generated by projecting a grid pattern onto the object, capturing a single frame, and in a post-process, superimposing a synthetic grid of the same frequency as in the captured image. Phase-shifting is carried out as a post-process by digitally shifting the synthetic grid across the captured image. The useful moiré patterns, which contain object shape information, are contaminated with a high-frequency grid lines that must be removed. After performing grid removal, computation of a phase map, and phase-to-height mapping, 3D object shape can be computed. The advantage of digital moiré provides an opportunity to decrease the number of projected patterns. However, in previous attempts to apply digital phase-shifting moiré to perform 3D surface-shape measurement, there have been significant limitations. To address the limitation of previous system-calibration techniques based on direct measurement of optical-setup parameters, a moiré-wavelength based phase-to-height mapping system-calibration method was developed. The moiré-wavelength refinement performs pixel-wise computation of the moiré wavelength based on the measured height (depth). In measurement of a flat plate at different depths, the range of root-mean-square (RMS) error was reduced from 0.334 to 0.828 mm using a single global wavelength across all pixels, to 0.204 to 0.261 mm using the new pixel-wise moiré-wavelength refinement. To address the limitations of previous grid removal techniques (precise mechanical grid translation, multiple-frame capture, moiré-pattern blurring, and measurement artifacts), a new grid removal technique was developed for single-frame digital moiré using combined stationary wavelet and Fourier transforms (SWT-FFT). This approach removes high frequency grid both straight and curved lines, without moiré-pattern artifacts, blurring, and degradation, and was an improvement compared to previous techniques. To address the limitations of the high number of projected patterns and captured images of temporal phase unwrapping (TPU) in fringe projection, and the low signal-to-noise ratio of the extended phase map of TPU in digital moiré, improved methods using two-image and three-image TPU in digital phase-shifting moiré were developed. For measurement of a pair of hemispherical objects with true radii 50.80 mm by two-image TPU digital moiré, least-squares fitted spheres to the measured 3D point clouds had errors of 0.03 mm and 0.06 mm, respectively (sphere fitting standard deviations 0.15 mm and 0.14 mm), and the centre-to-centre distance measurement between hemispheres had an error of 0.19 mm. The number of captured images required by this new method is one third that for three-wavelength heterodyne temporal phase unwrapping by fringe projection techniques, which would be advantageous in measuring dynamic objects, either moving or deforming.
3D Shape Reconstruction of Knee Bones from Low Radiation X-ray Images Using Deep Learning
(University of Waterloo, 2021-06-02) Hampali, Shamanth; Chandrashekar, Naveen
Understanding the bone kinematics of the human knee during dynamic motions is necessary to evaluate the pathological conditions, design knee prosthesis, orthosis and surgical treatments such as knee arthroplasty. Also, knee bone kinematics is essential to assess the biofidelity of the computational models. Kinematics of the human knee has been reported in the literature either using in vitro or in vivo methodologies. In vivo methodology is widely preferred due to biomechanical accuracies. However, it is challenging to obtain the kinematic data in vivo due to limitations in existing methods. One of the several existing methods used in such application is using X-ray fluoroscopy imaging, which allows for the non-invasive quantification of bone kinematics. In the fluoroscopy imaging method, due to procedural simplicity and low radiation exposure, single-plane fluoroscopy (SF) is the preferred tool to study the in vivo kinematics of the knee joint. Evaluation of the three-dimensional (3D) kinematics from the SF imagery is possible only if prior knowledge of the shape of the knee bones is available. The standard technique for acquiring the knee shape is to either segment Magnetic Resonance (MR) images, which is expensive to procure, or Computed Tomography (CT) images, which exposes the subjects to a heavy dose of ionizing radiation. Additionally, both the segmentation procedures are time-consuming and labour-intensive. An alternative technique that is rarely used is to reconstruct the knee shape from the SF images. It is less expensive than MR imaging, exposes the subjects to relatively lower radiation than CT imaging, and since the kinematic study and the shape reconstruction could be carried out using the same device, it could save a considerable amount of time for the researchers and the subjects. However, due to low exposure levels, SF images are often characterized by a low signal-to-noise ratio, making it difficult to extract the required information to reconstruct the shape accurately. In comparison to conventional X-ray images, SF images are of lower quality and have less detail. Additionally, existing methods for reconstructing the shape of the knee remain generally inconvenient since they need a highly controlled system: images must be captured from a calibrated device, care must be taken while positioning the subject's knee in the X-ray field to ensure image consistency, and user intervention and expert knowledge is required for 3D reconstruction. In an attempt to simplify the existing process, this thesis proposes a new methodology to reconstruct the 3D shape of the knee bones from multiple uncalibrated SF images using deep learning. During the image acquisition using the SF, the subjects in this approach can freely rotate their leg (in a fully extended, knee-locked position), resulting in several images captured in arbitrary poses. Relevant features are extracted from these images using a novel feature extraction technique before feeding it to a custom-built Convolutional Neural Network (CNN). The network, without further optimization, directly outputs a meshed 3D surface model of the subject's knee joint. The whole procedure could be completed in a few minutes. The robust feature extraction technique can effectively extract relevant information from a range of image qualities. When tested on eight unseen sets of SF images with known true geometry, the network reconstructed knee shape models with a shape error (RMSE) of 1.91± 0.30 mm for the femur, 2.3± 0.36 mm for the tibia and 3.3± 0.53 mm for the patella. The error was calculated after rigidly aligning (scale, rotation, and translation) each of the reconstructed shape models with the corresponding known true geometry (obtained through MRI segmentation). Based on a previous study that examined the influence of reconstructed shape accuracy on the precision of the evaluation of tibiofemoral kinematics, the shape accuracy of the proposed methodology might be adequate to precisely track the bone kinematics, although further investigation is required.
3D Silicone Whipping Additive Manufacturing (SWAM): Technology, Applications, and Research Needs.
(University of Waterloo, 2022-01-20) Saggu, Gurkamal; Simon, Leonardo; Rech, Rosane
Additive manufacturing has become increasingly popular and is developing in many technologies. This thesis focusses on the additive manufacturing with paste technology, more specifically the goal is to further develop a technology for SWAM (Silicone Whipping Additive Manufacturing). SWAM uses a device similar to a traditional filament 3D printer, but it deploys a paste supplied by a pump instead of feeding a thermoplastic filament through a heated nozzle. There are many parameters that are common to both technologies, but the role of several variables is still not described or discussed in the literature. This is relevant because there are limited technologies capable of exploring the advantage of additive manufacturing with soft or elastomeric materials. A successful SWAM technology be used for developing prototypes that require soft materials, like seat cushion for automotive applications and used in tissue for soft robotics. One of the key parameters controlling the properties of a part manufacture by SWAM is the whipping mechanism of the paste. In this thesis, experiments are presented based on the relationship of SWAM parameters and “Line Printing” characteristics. Line Printing is an experimental method developed here to obtain further insight on the mechanism of SWAM and to enable correlation between SWAM parameters and properties of printed parts. The whipping extrusion techniques has successfully elucidated the liquid rope coiling effect. The SWAM parameters were selected as: Print speed of the nozzle, Diameter of the nozzle, Flow rate of the silicone feed, and Deposition height of the falling silicone paste. Whereas the Line Printing characteristics such as Filament deposition height, Filament line width and Filament loops have been determined. Filament loops are further subdivided into Single loops and Multiple loops. As a result, Line Printing may be defined as the novel free forming techniques for reproducing a single segment of the desired feed onto the printed bed using various forms of fabricating methods. It may also be called filament printing, filament fabrication, or line prototyping. It would be an aim to study the behavior of the material deposition as well as its transformed deposition ranging from straight-line printing to multiple or mixed-looped line printing. Hence, novel empirical relationships can be generated based on two boundaries elementary parametric conditions that are print speed and the other is flow rate. A novel parameter named GL ratio was introduced here to describe the transformation of the filament through filament characteristics. It would thoroughly define the feed flow dropping criterion. It is the ratio of the change in the feed flow rate to the change in the print speed of the nozzle while the other parameters are held constant. Five transformations of the line filament have occurred which are named as straight line, zig- zag/wavy loop filament, single loops filament, mix loops filament and multiple loops filament. Out of the 5, there are two unstable states, and the rest are stable states. Instability of filament is relatively high at the transition state because of the changing patterns of the silicone rope coiling effect, where GL is equal to unity. Line printing can be formed into multiple layers thus producing the bulk form which would be a porous structure, thus giving rise to a 3D shape due to controlled deposition of the filament due to the X-Y-Z location of the nozzle. In automotive applications, this technique can be used to create prototypes for an in-seat car cushion as a substitute for polyurethane (PUR) seat cushions. Herein, silicone has been used because of its versatile applications. The in-seat silicone cushions have been produced to perform force-deflection test to identify the mechanical feature. Viscoelastic properties of silicone concluded that novel SWAM can print lower density in-seat cushion along with variable firmness. The printed cushion showed that they can withstand the applied force for a longer time-period without decreasing with time. This feature would reveal that silicone can be a good material for seat cushioning. Hard-skinned robots can be modified to humanoid robots which would be ideal in the education system, especially for the autistic children. Soft tissue mimicking materials have been obtained through the line printing technique of the novel SWAM. Parts can be printed to resemble the firmness of fat and muscle tissues due to the displayed similar properties to that of real tissues through mechanical experiments. This could be applied in robots assisting autistic children for example, so they would learn response to external stimuli through humanoid robots in a more natural interactive environment

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