Separated magnet yoke for permanent magnet linear generator for marine wave energy converters

In this paper the performance of a longitudinal flux permanent magnet linear generator (PMLG) for wave energy converters (WEC) is investigated. The influence of the number of slots per pole, phase q and the number of stator's winding sections are analysed. The power output and the cogging forces in the PMLG are calculated and reviewed with respect to the above design parameters. In addition, an optimised PMLG model is designed and simulated. Three-dimensional Finite Element Method (FEM) is used for solving the combined field and circuit equations of the generator.The PRIMaRE project

Coffee Queue Project

In this paper, a computer vision system for counting people standing in line is presented. In this application, common techniques such as Adaptive Background Subtraction (ABS), blob tracking with Kalman filter, and occlusion resistive techniques are used to detect and track people. Additionally, a novel method using Dual Adaptive Background Subtractors (DABS) is implemented for dynamically determining the line region in a real-world crowded scene, and also as an alternative target acquisition to regular ABS. The DABS technique acts as a temporal bandpass filter for motion, helping identify people standing in line while in the presence of other moving people. This is achieved by using two ABS with different temporal adaptiveness. Unlike other computer vision papers which perform tests in highly controlled environments, the DABS technique is tested in a crowded Starbucks© at the Cal Poly student union. For any length of people standing in line, result shows that DABS has a lower mean error by one or more people when compared to ABS. Even in challenging crowded scenes where the line can reach 19 people in length, DABS achieves a Normalized RMS Error of 43%

Determinism and looping in combinatory PDL

AbstractIn this paper some propositional modal logics of programs are considered, based on the system CPDL (Combinatory PDL)—an extension of PDL with proper names for states. These proper names are atomic formulae which are satisfied at exactly one state, in each model. Among other things (e.g., decidability and finite-model property results) a version of Streett's conjecture that his axioms do axiomatize the infinite repeating construct repeat is established with respect to CPDL

Starbucks Line Monitoring

We have developed a computer vision application to count the number of people in line at the Starbucks in the UU. The count will soon be published live on the web, and statistics will be tracked. Also coming soon are iOS and Andriod applications. This project has to date yielded one senior project and one soon to be defended MS thesis. Other senior projects and/or thesis documents will be published in the future as well

Investigation of multi-phase tubular permanent magnet linear generator for wave energy converters

In this article, an investigation into different magnetization topologies for a long stator tubular permanent magnet linear generator is performed through a comparison based on the cogging force disturbance, the power output, and the cost of the raw materials of the machines. The results obtained from finite element analysis simulation are compared with an existing linear generator described in [1]. To ensure accurate results, the generator developed in [1] is built with 3D CAD and simulated using the finite-element method, and the obtained results are verified with the source.The PRIMaRE project

Permanent Magnet Linear Generators for Marine Wave Energy Converters

Abstract: Direct drive Permanent Magnet Linear Generators (PMLGs) are used in energy converters for energy harvesting from marine waves. Greater reliability and simplicity can be achieved for Wave Energy Converters (WECs), by using direct drive machines linked to the power take-off device, in comparison with WECs using rotational generators combined with hydraulic or mechanical interfaces to convert linear to rotational torque. However, owing to the relatively low velocities of marine waves and the desire for significant energy harvesting by each individual unit, direct drive PMLGs share large permanent magnet volumes and hence, high magnetic forces. Such forces can generate vibrations and reduce the lifetime of the bearings significantly, which is leading to an increase in maintenance costs of WECs. Additionally, a power electronics converter is required to integrate the generator‘s electrical output to meet the requirements for connection to the national grid. This thesis is concerned mainly with the fundamental investigation into the use PMLGs for direct drive WECs. Attention is focused on developing several new designs based on tubular long stator windings topologies and optimisation for flat PMLGs. The designs are simulated as air- and iron-cored machines by means of Finite Element Analysis (FEA). Furthermore, a new power electronics control system is proposed to convert the electrical output of the long stator generators. Various wave energy-harvesting technologies have been reviewed and it has been found that permanent magnet linear machines demonstrate great potential for integration in WECs. The main reason is the strong exaltation flux provided by the high number of permanent magnets. Such flux, combined with design simplicity, can deliver high induced voltage as well as structural integrity. In the thesis, a flat single and double structured iron-cored PMLG is studied and optimised. Several magnetic force mitigation techniques are investigated and an optimisation is conducted. The optimisation is concerned mainly with increasing electrical output power and reducing the magnetic forces in the generators. As a result, an optimal design introducing the idea of separated magnetic cores has been proposed. The FEA simulations reveal that magnetic separation in the yoke can increase significantly the energy-harvesting capability of PMLGs. Furthermore, the concept of the design of long stator windings for tubular PMLGs is studied. Two long stator generators having different magnetisation topologies and similar sizes to existing machine are modelled and compared to the existing machine. The similar-sized existing and proposed PMLGs are simulated by FEA. In this way, settings such as different boundary conditions, symmetry boundaries and material properties are used to gain confidence in the simulated results of the proposed machines. Moreover, the simulated results for the existing PMLG are verified against previously performed numerical simulations and practical tests delivered and published as part of other research. The outcome for the proposed PMLGs reveals several advantages for the long stator design, such as lower cogging forces and higher energy harvesting and a lower price of the raw structural materials. Additionally, the thesis proposes and simulates a new design for an air-cored PMLG. To boost the output power, the proposed design is based on a long stator topology adopting two sets of permanent magnet rings sandwiching copper windings in a tubular structure. The design is compared with a current machine in FEA and the results show significant reduction in radial forces and an increase in energy harvesting. Finally, a novel power electronics control system, bypassing inactive coils is suggested and simulated as part of the grid integration system for the long stator PMLGs. The new system achieves a reduction in the thermal losses in the power electronics switches in comparison with existing systems. The power electronics system and the generator have been simulated in Matlab coupled externally with FEA (JMAG Designer).PRIMaRE/University of Exete

A system of relational syllogistic incorporating full Boolean reasoning

We present a system of relational syllogistic, based on classical propositional logic, having primitives of the following form: Some A are R-related to some B; Some A are R-related to all B; All A are R-related to some B; All A are R-related to all B. Such primitives formalize sentences from natural language like `All students read some textbooks'. Here A and B denote arbitrary sets (of objects), and R denotes an arbitrary binary relation between objects. The language of the logic contains only variables denoting sets, determining the class of set terms, and variables denoting binary relations between objects, determining the class of relational terms. Both classes of terms are closed under the standard Boolean operations. The set of relational terms is also closed under taking the converse of a relation. The results of the paper are the completeness theorem with respect to the intended semantics and the computational complexity of the satisfiability problem.Comment: Available at http://link.springer.com/article/10.1007/s10849-012-9165-

Performance of industrial melting pots in the provision of dynamic frequency response in the Great Britain power system

As a result of the increasing integration of Renewable Energy Source (RES), maintenance of the balance between supply and demand in the power system is more challenging because of RES’s intermittency and uncontrollability. The smart control of demand is able to contribute to the balance by providing the grid frequency response. This paper uses the industrial Melting Pot (MP) loads as an example. A thermodynamic model depicting the physical characteristics of MPs was firstly developed based on field measurements carried out by Open Energi. A distributed control was applied to each MP which dynamically changes the aggregated power consumption of MPs in proportion to changes in grid frequency while maintaining the primary heating function of each MP. An aggregation of individual MP models equipped with the control was integrated with the Great Britain (GB) power system models. Case studies verified that the aggregated MPs are able to provide frequency response to the power system. The response from MPs is similar but faster than the conventional generators and therefore contributes to the reduction of carbon emissions by replacing the spinning reserve capacity of fossil-fuel generators. Through the reviews of the present balancing services in the GB power system, with the proposed frequency control strategy, the Firm Frequency Response service is most beneficial at present for demand aggregators to tender for. All studies have been conducted in partnership between Cardiff University, Open Energi London – Demand Aggregator, and National Grid – System Operator in GB to ensure the quality and compliance of results

Power system frequency response from the control of bitumen tanks

Bitumen tanks were tested to investigate the capability of industrial heating loads to provide frequency response to an electric power system. A decentralized control algorithm was developed enabling the tanks to alter their power consumption in proportion to the variations of grid frequency. The control maintains the normal operation of tanks and causes little impact on their primary function of storing hot bitumen. Field investigations were undertaken on 76 tanks with power ratings from 17 to 75 kW. A model of a population of controlled tanks was developed. The behavior of the tanks was compared between the simulations and the field tests. The model of controlled tanks was then integrated with a simplified Great Britain power system model. It was shown that the controlled tanks were able to contribute to the grid frequency control in a manner similar to and faster than that provided by frequency-sensitive generation