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Publikacije (11)

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E. Silva, D. Viegas, A. Martins, J. Almeida, C. Almeida, B. Neves, P. Madureira, A. J. Wheeler et al.

By creating a dependable, transparent, and cost-effective system for forecasting and ongoing environmental impact monitoring of exploration and exploitation activities in the deep sea, TRIDENT seeks to contribute to the sustainable exploitation of seabed mineral resources. In order to operate autonomously in remote locations under harsh conditions and send real-time data to authorities in charge of granting licenses and providing oversight, this system will create and integrate new technology and innovative solutions. The efficient monitoring and inspection system that will be created will abide by national and international legal frameworks. At the sea surface, mid-water, and the bottom, TRIDENT will identify all pertinent physical, chemical, geological, and biological characteristics that must be monitored. It will also look for data gaps and suggest procedures for addressing them. These are crucial actions to take in order to produce accurate indicators of excellent environmental status, statistically robust environmental baselines, and thresholds for significant impact, allowing for the standardization of methods and tools. In order to monitor environmental parameters on mining and reference areas at representative spatial and temporal scales, the project consortium will thereafter develop and test an integrated system of stationary and mobile observatory platforms outfitted with the most recent automatic sensors and samplers. The system will incorporate high-capacity data processing pipelines able to gather, transmit, process, and display monitoring data in close to real-time to facilitate prompt actions for preventing major harm to the environment. Last but not least, it will offer systemic and technological solutions for predicting probable impacts of applying the developed monitoring and mitigation techniques.

E. Omerdic, J. Osmic, Cathal W. O’Donnell, E. Omerdic

A control algorithm for Parallel Connected Offshore Wind Turbines with permanent magnet synchronous Generators (PCOWTG) is presented in this paper. The algorithm estimates the optimal collective speed of turbines based on the estimated mechanical power of wind turbines without direct measurement of wind speed. In the proposed topology of the wind farm, direct-drive Wind Turbine Generators (WTG) is connected to variable low-frequency AC Collection Grids (ACCG) without the use of individual power converters. The ACCG is connected to a variable low-frequency offshore AC transmission grid using a step-up transformer. In order to achieve optimum wind power extraction, the collective speed of the WTGs is controlled by a single onshore Back to Back converter (B2B). The voltage control system of the B2B converter adjusts voltage by keeping a constant Volt/Hz ratio, ensuring constant magnetic flux of electromagnetic devices regardless of changing system frequency. With the use of PI pitch compensators, wind power extraction for each wind turbine is limited within rated WTG power limits. Lack of load damping in offshore wind parks can result in oscillatory instability of PCOWTG. In this paper, damping torque is increased using P pitch controllers at each WTG that work in parallel with PI pitch compensators.

E. Omerdic, J. Osmic, D. Toal, Cathal W. O’Donnell

A new control algorithm for Directly Interconnected offshore Wind Turbines with permanent magnet synchronous Generators (DIWTG) is presented. In the DΓWTG offshore wind park configuration, Wind Turbines with Permanent Magnet Synchronous Generators (WTPMSG) are directly connected to the offshore AC collection grid without using a power converter. The offshore AC collection grid is then connected, via a transformer, to the offshore AC transmission grid. In order to achieve maximum power point tracking, the (collective) speed of DΓWTGs is controlled by an onshore back to back converter. By measuring the active power and speed of the permanent magnet generators, wind speed at each turbine is estimated and used for calculation of the reference speed of WTPMSGs. Voltage control at the power converter side is performed in a way which allow the DΓWTGs to be operated at a constant V/f where the maximum resultant frequency at nominal wind speed is 16.67 Hz.

In this paper it is presented the real time monitoring system of water flow in hydro power plants which is designed with virtual instrumentation software. Water flow through penstock has been measured by using flow sensor. Volumetric flow of excess water, in the case of emergency evacuation of water, has been calculated from position of control gates and water level. Relationship between the volumetric flow of excess water, position of control gates and water level has been a prior experimentally established and saved into look up table. Signals from position and level sensors have been used as inputs into the look up table. Entries into the look up table are interpolated using bilinear interpolation method and they are used for calculation of excess water flow. By using integration method with fixed step time, the volume of transmitted water through all outlets has been calculated. All necessary real time calculation, data presentation and data logging have been performed using virtual instrumentation software. With a proper application software organization and by means of digital communication real time measurement and presentation of results are ensured.

Hijaz Ahmad, T. M. Young, D. Toal, E. Omerdic

Abstract This study applies the control allocation (CA) to several aircraft flight controls to produce the required body axis angular accelerations. The control law was designed using the linear quadratic regulator technique to produce the virtual control effort signals. This control law is effectively a multi-input multi-output proportional-integral controller. The virtual control efforts that are produced by the controller are then distributed by solving a multi-branch CA problem using the active set method. The solution of this CA problem is then distributed to the control surfaces. The solution is computed at a sampling frequency of 1 kHz. The designed control law and CA were then implemented in a non-linear B747-200 simulation model. The tracking performance in terms of the attitudes of the aircraft is presented.

E. Omerdic, D. Toal, E. Omerdic

This paper describes a novel vehicle designed for operation flexibility in high-resolution near seabed survey from shallow inshore waters out to the continental shelf edge. The vehicle can be operated in surface tow or as a thrusted pontoon. With buoyancy module release the vehicle becomes neutrally buoyant and is operated as a survey class remotely operated vehicle (ROV) depth rated to 1,000m. Special features of the system include: deployment interoperability for small inshore boats and larger research vessel; fault tolerant thruster control; novel high frequency short range sonar; onboard computer control enabling real-time disturbance reaction; topside augmented reality system support. The paper includes test results from the off shore sea trials with the ROVLATIS in March 2009.

Nwa Sowerby, E. Omerdic, G. Roberts

This paper describes the current state of the work done at The University of Wales College Newport under the ‘improve the performance of remotely operated vehicles’ programmme (IMPROVES). The work incorporates advances in two interrelated parts of the project: it presents a technique to extract velocity from a low-cost MEMS inertial measurement unit for system identification and development of a combined control allocation and fault detection technique. The paper presents theoretical developments and results obtained on experimental trials.

E. Omerdic, G. Roberts, Z. Vukic

In this paper a non-linear fuzzy autopilot for ship track-keeping is presented. The proposed autopilot has four inputs (actual and desired heading, rate of change of heading and offset from the desired path) and one output (command rudder angle). The track-keeping problem is decomposed into two subtasks: (i) follow the desired heading, and (ii) bring the ship onto the desired path and keep tracking. Internally, the autopilot consists of two autopilots that fulfil these tasks simultaneously. The proposed control scheme has been verified using a non-linear model of a Mariner-class vessel and steering mechanism under the influence of wave and current disturbances. Results presented show how such a control strategy enables improved tracking performance.

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