In the last two decades there has been an increasing interest in the field of haptics science. Real-time simulation of haptic interaction with non-rigid deformable object/tissue is computationally demanding. The computational bottleneck in finite- element (FE) modeling of deformable objects is in solving a large but sparse linear system of equations at each time step of the simulation. Depending on the mechanical properties of the object, high-fidelity stable haptic simulations require an update rate in the order of 100 − 1000 Hz. Direct software-based implementations that use conventional computers are fairly limited in the size of the model that they can process at such high rates. In this thesis, a new hardware-based parallel implementation of the iterative Conjugate Gradient (CG) algorithm for solving linear systems of equations is pro- posed. Sparse matrix-vector multiplication (SpMxV) is the main computational kernel in iterative solution methods such as the CG algorithm. Modern micro- processors exhibit poor performance in executing memory-bound tasks such as SpMxV. In the proposed hardware architecture, a novel organization of on-chip memory resources enables concurrent utilization of a large number of fixed-point computing units on a FPGA device for performing the calculations. The result is a powerful parallel computing platform that can iteratively solve the system of equations arising from the FE models of object deformation within the timing constraint of real-time haptics applications. Numerical accuracy of the fixed-point implementation, the hardware architecture design, and issues pertaining to the degree of parallelism and scalability of the solution are discussed in details. The proposed computing platform in this thesis is successfully employed in a set of haptic interaction experiments using static and dynamic linear FE-based models. / Master of Applied Science (MASc)

<p> The simulation of soft tissue deformations has many practical uses in the medical field such as diagnosing medical conditions, training medical professionals and surgical planning. While there are many good computational models that are used in these simulations, carrying out the simulations is time consuming especially for large systems. This is because most simulators are based on software, which are run on general-purpose computers (GPC) that are not optimized to carry out the operations needed for simulation. In order to improve the performance of these simulators, field-programmable-gate-arrays (FPGA) based accelerators for carrying out Matrix-by-Vector multiplications (MVM) have been implemented by Ramachandran in 1998 and Zhuo et. al. in 2005. Zhuo et. al. also looked at the best ways to store a matrix in memory, and how this is affected by certain properties of the matrix.</p> <p> A better approach is to implement an accelerator for carrying out all operations required for simulation on hardware. In this study we propose a hardware accelerator for simulating soft-tissue deformation using finite-difference approximation of elastodynamics equations based on conjugate-gradient inversion of sparse matrices. We designed and implemented the accelerator, which is optimized for use with sparse matrices, on FPGA. We also conducted performance and resource requirements analysis for the accelerator. Our results show this approach is capable of achieving sufficiently high computational rate for carrying out real-time simulation; even with large grids or meshes. Finally, we developed computational models for carrying out real-time simulation of tissue deformation.</p> / Thesis / Master of Applied Science (MASc)

The transition from fossil fuel-based energy sources involves exploring different sources of energy that can be reliably integrated into the power grid. One such existing resource is the CHPs, which are distributed throughout the US electric grid. The integration of the CHPs into the grid requires technological innovations. One idea is to design an F-CHP converter that would facilitate the CHPs to interconnect seamlessly with the electrical grid. This thesis presents the development and testing of different components of a testbed that would facilitate the testing of the F-CHP converter. It also presents the integration of a PMU and a communication interface for the F-CHP converter. The phasor estimation of the F-CHP PMU has been compared with a commercial PMU and its performance has been validated. / Master of Science / The transition from fossil fuel based energy sources involves exploring different sources of energy that can reliably integrated into the power grid. One such existing resource is the CHPs, that are distributed throughout the US electric grid. The integration of the CHPs into the grid required technological innovations. One idea is to design a power electronics converter that would facilitate the CHPs to connect with the electrical grid. This thesis presents the development and testing of different components of a testbed that would facilitate the testing of the converter. This work also integrates a technology for estimating the voltage and current at the point of interconnection between the converter and the electrical grid.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / This thesis documents the research, design and implementation of a virtual hysteroscopy simulator. A hysteroscopy is a medical procedure used in the field of obstetrics and gynaecology. The system consists of a mechanically modelled hysteroscope connecting to any personal computer using USB, and is plug and play compatible on any modernWindows operating system. The scope interfaces with custom-designed software, which simulates a patient’s anatomy and thus creates a virtual operating environment. The software incorporates features like simulated soft tissue and an ablation algorithm. This system is developed with the aim to aid the young or inexperienced surgeon with hands-on training, developing his hand-eye coordination and visual and surgical skills used in this procedure.

L’intégration des méthodes numériques dans les procédés industriels à son origine à l’apparition des ordinateurs, et est de plus en plus intégré parallèlement au développement de la technologie. Dans le cadre des procédés industriels où interviennent des structures en mouvement, il est intéressant d’avoir de méthodes de calcul rapide pour de problèmes non linéaires, comme par exemple, la manipulation de matériaux souples par robots. La résolution de ce type de problème reste encore comme un défi pour l’ingénierie. Malgré l’existence de nombreuses méthodes pour résoudre les problèmes dynamiques, aucun n’est adaptée à la simulation en temps réel. Pour la façon de résolution, nous avons divisé le problème dynamique en deux sous-problèmes : le problème direct, qui consiste à calculer les déplacements en fonction de la force appliqué, et le problème inverse, dans lequel on calcule la force en fonction des déplacements appliqués. / Integration of numeric methodes in industrial procedures starts with the development of the computers, and its being integrated as its grows the technology. In the industrial procedures where moving structrues are involved, its necessary the hability of fast computing in non lineare problems, for example, material manipulation by soft robots. The solution of this kind of problems is still a challenge for the engineering. Despite the existance of numerous methodes to solve the dynamic problem, non of them is adapted to real time simulation. By the way of facing the problem, we have divised the dynamic problem in two subproblems: the direct problem, where displacements are computed when an external force is applied, and the inverse problem, where the external force is computed from the displacements.

The purpose of this thesis is to use automation to create appropriate models in PSS/E with the data from Hardware-in-Loop real-time simulations. With the increase in technology of power electronics, the use of High Voltage Direct Current Technology and Flexible Alternating Current Transmission System devices in the electrical power system have increased tremendously. Static Var Compensators are widely used and it is important to have accurate and reliable models for studies relating to power systems planning and interaction. An automation method is proposed to find the parameters of an SVC model in PSS/E with the data from the Hardware-in- loop real-time simulation of the SVC physical controller using Hypersim. The effect of the SVC on the system under steady state and fault conditions are analyzed with HIL simulation of an SVC physical controller in Hypersim and its corresponding model in PSS/E in the IEEE 14 bus system. The parameters of the SVC model in PSS/E can be effectively varied to bring its response closer to that of the response from HIL simulations in Hypersim. An error function is used as a measure to understand the extent of difference between the model and the physical controller.

The present work introduces a methodology to obtain a discrete time state space representation of an electrical network using the nodal [G] matrix of the Electromagnetic Transients Program (EMTP) solution. This is the first time the connection between the EMTP nodal analysis solution and a corresponding state-space formulation is presented. Compared to conventional state space solutions, the nodal EMTP solution is computationally much more efficient. Compared to the phasor solutions used in transient stability analysis, the proposed approach captures a much wider range of eigenvalues and system operating states. A fundamental advantage of extracting the system eigenvalues directly from the EMTP solution is the ability of the EMTP to follow the characteristics of nonlinearities. The system's trajectory can be accurately traced and the calculated eigenvalues and eigenvectors correctly represent the system's instantaneous dynamics. In addition, the algorithm can be used as a tool to identify network partitioning subsystems suitable for real-time hybrid power system simulator environments, including the implementation of multi-time scale solutions. The proposed technique can be implemented as an extension to any EMTP-based simulator. Within our UBC research group, it is aimed at extending the capabilities of our real-time PC-cluster Object Virtual Network Integrator (OVNI) simulator.

A generalized dynamic programming based algorithm and a local search heuristic are used to solve the Two Runway Departure Scheduling Problem that arises at an airport. The objective of this work is to assign the departing aircraft to one of the runways and find a departing time for each aircraft so that the overall delay is minimized subject to the timing, safety, and the ordering constraints. A reduction in the overall delay of the departing aircraft at an airport can improve the airport surface operations and aircraft scheduling. The generalized dynamic programming algorithm is an exact algorithm, and it finds the optimal solution for the two runway scheduling problem. The performance of the generalized dynamic programming algorithm is assessed by comparing its running time with a published dynamic programming algorithm for the two runway scheduling problem. The results from the generalized dynamic programming algorithm show that this algorithm runs much faster than the dynamic programming algorithm. The local search heuristic with k − exchange neighborhoods has a short running time in the order of seconds, and it finds an approximate solution. The performance of this heuristic is assessed based on the quality of the solution found by the heuristic and its running time. The results show that the solution found by the heuristic for a 25 aircraft problem has an average savings of approximately 15 percent in delays with respect to a first come-first served solution. Also, the solutions produced by a 3-opt heuristic for a 25 aircraft scheduling problem has an average quality of 8 percent with respect to the optimal solution found by the generalized dynamic programming algorithm. The heuristic can be used for both real-time and fast-time simulations of airport surface operations, and it can also provide an upper limit for an exact algorithm. Aircraft arrival scheduling problems may also be addressed using the generalized dynamic programming algorithm and the local search heuristic with slight modification to the constraints.

Traffic congestion is a one hundred billion dollar problem in the US. The cost of congestion has been trending upward over the last few decades, but has experienced slight decreases in recent years partly due to the impact of congestion reduction strategies. The impact of these strategies is however largely experienced on freeways and not arterials. This discrepancy in impact is partially linked to the lack of real-time, arterial traffic information. Toward this end, this research effort seeks to address the lack of arterial traffic information. To address this dearth of information, this effort developed a methodology to provide accurate estimates of arterial performance measures to transportation facility managers and travelers in real-time. This methodology employs transmitted point sensor data to drive an online, microscopic traffic simulation model. The feasibility of this methodology was examined through a series of experiments that were built upon the successes of the previous, while addressing the necessary limitations. The results from each experiment were encouraging. They successfully demonstrated the method's likely feasibility, and the accuracy with which field estimates of performance measures may be obtained. In addition, the method's results support the viability of a "real-world" implementation of the method. An advanced calibration process was also developed as a means of improving the method's accuracy. This process will in turn serve to inform future calibration efforts as the need for more robust and accurate traffic simulation models are needed. The success of this method provides a template for real-time traffic simulation modeling which is capable of adequately addressing the lack of available arterial traffic information. In providing such information, it is hoped that transportation facility managers and travelers will make more informed decisions regarding more efficient management and usage of the nation's transportation network.

The present work introduces a methodology to obtain a discrete time state space representation of an electrical network using the nodal [G] matrix of the Electromagnetic Transients Program (EMTP) solution. This is the first time the connection between the EMTP nodal analysis solution and a corresponding state-space formulation is presented. Compared to conventional state space solutions, the nodal EMTP solution is computationally much more efficient. Compared to the phasor solutions used in transient stability analysis, the proposed approach captures a much wider range of eigenvalues and system operating states. A fundamental advantage of extracting the system eigenvalues directly from the EMTP solution is the ability of the EMTP to follow the characteristics of nonlinearities. The system's trajectory can be accurately traced and the calculated eigenvalues and eigenvectors correctly represent the system's instantaneous dynamics. In addition, the algorithm can be used as a tool to identify network partitioning subsystems suitable for real-time hybrid power system simulator environments, including the implementation of multi-time scale solutions. The proposed technique can be implemented as an extension to any EMTP-based simulator. Within our UBC research group, it is aimed at extending the capabilities of our real-time PC-cluster Object Virtual Network Integrator (OVNI) simulator.