Search results

(1 - 2 of 2)
MODELING, CONTROL, AND DESIGN OF HYBRID FUEL CELL VEHICLES
Title
MODELING, CONTROL, AND DESIGN OF HYBRID FUEL CELL VEHICLES
Creator
Ahmed, Syed
Date
2011-12, 2011-12
Description
The Polymer Electrolyte Membrane Fuel Cell (PEMFC) has been projected to be the fuel cell of choice for future automotive applications. Among...
Show moreThe Polymer Electrolyte Membrane Fuel Cell (PEMFC) has been projected to be the fuel cell of choice for future automotive applications. Among the challenging aspects of this application is maintaining highly efficient operation of the fuel cell. The key component of the PEMFC, the Nafion Membrane, can reach two critical states: drying and flooding. In drying, high resistance prevents normal operation of the fuel cell. In flooding, reactants are prevented from reaching reaction sites and there is a reduction of performance of the fuel cell. To address the first point, a spatially distributed along the plane membrane model was developed and tested with proportional-integral control of voltage and temperature. To analyze the occurrence of severe and frequent changes in power demand, a model aimed at mimicking the load expected in a fuel cell vehicle, including a DC motor, DC-DC converters and a rechargeable battery for peak-shaving and regenerative braking was developed. The model includes rotational and translational inertia as well as a simple wind resistance model for a vehicle. In contrast to simple lab-focused loads where load impendence is directly manipulated, the manipulated variable within this load is the DC-DC converter gain. Based on this model a control system architecture was developed consisting of a number of low level regulatory loops, a power distributor for peak-shaving and finally a high level loop for tracking vehicle speed. After understanding the load demands to a fuel cell vehicle with only a battery, the issue of multiple energy storage technologies is addressed. Designing a vehicle with these technologies poses an optimization problem. A high-level model of a fuel cell vehicle with two storage technologies, a battery and super-capacitor was developed. The model accounted for the constraints of each component and a drive cycle characterized the power demand. An economic-based optimization problem xv was posed whereas its objective was to minimize the capital cost of the system, while meeting power demand and keeping the technologies within their constraints. The result of the optimization provided a controller from which a high-level power coordination unit can be developed for the fuel cell vehicle.
Ph.D. in Chemical Engineering, December 2011
Show less
NETWORK SELECTION WITH LOAD MANAGEMENT IN HETEROGENEOUS WIRELESS NETWORKS
Title
NETWORK SELECTION WITH LOAD MANAGEMENT IN HETEROGENEOUS WIRELESS NETWORKS
Creator
Ahmed, Syed Qutubuddin
Date
2013, 2013-12
Description
With the growth of data-capable, multi-interface wireless and mobile devices, a lot of research work is being done on handover management and...
Show moreWith the growth of data-capable, multi-interface wireless and mobile devices, a lot of research work is being done on handover management and network selection in heterogeneous environment. Many researchers have proposed several strategies and policies for selecting the appropriate network. These policies di er among each other due to various reasons. The state and load of networks, number and types of wireless networks considered, and preferences of users are some of the reasons that attribute to di erences in those proposed policies. As a result, the applicability and e ciency of those policies depend upon certain situations and circumstances. We propose, in this research, a new concept that will help in utilizing these various policies in a manner that will give better results in a longer run and in various kinds of situations. We have a pool of policies available, and our proposed method will select the policy that is most appropriate according to the current state of user. We modeled this problem as a Markov Decision Process. Since the overall goal is that a user should be able to select an appropriate wireless network according to its service requirements and seamlessly handover to that network regardless of the underlying wireless technology being used. Since di erent sets of methodologies can exist to deal with this issue, we also propose an alternative mechanism that would facilitate a particular user to connect to the most appropriate network in a way that is bene cial to the overall network and its users as a whole. A trusted third party entity receives handover requests from a set of users along with their preferences, takes into consideration current network state of available service providers, and assigns each user to an appropriate network resource. We call this mechanism "Network Assisted Network Selection (NANS)" and it combines network-based, service-based and user-based criteria for network selection, and uses Generalized Assignment Problem (GAP) to assign the network resources to a set of users. ix Mobile Access Gateway (MAG) is a component of Proxy Mobile IPv6 (PMIPv6) which provides network-layer transparent mobility to mobile nodes (MN). MAG serves a local geographical area and mobile nodes in its vicinity may attach to it to get the mobility services from its controlling PMIPV6 domain. Since MAG is the point of attachment of mobile nodes, negotiated and guaranteed quality of service (QoS) is af- fected in case of service disruptions and overload of the MAG. To avoid and minimize the degradation of quality of service, we propose e ective mechanisms to share the load of a ected MAG with the MAG(s) that are working under normal conditions. We propose to handover certain mobile nodes to other MAGs depending upon their geographical serving area and current capacity. Furthermore, location of mobile node, its quality of service pro le, direction of motion and its multi-interface capability are major factors in selecting the mobile nodes for handover.
PH.D in Computer Engineering, December 2013
Show less