Optimal gear ratio selection of linear primary permanent magnet vernier machines for wave energy applications

© 2023 The Authors. IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Linear permanent magnet vernier generators offer a high capability of force density, making them appealing configurations for wave energy harvesting systems. In absolute terms, the performance of these machines is significantly influenced by the selection of slot/pole combinations based on the magnetic gearing effect. For the first time, this paper aims to investigate the impact of different gear ratios on a wide array of linear primary permanent magnet vernier machines (LPPMVMs) with different slot/pole combinations based on fair criteria to offer a more comprehensive understanding of gear ratio selection. To find the optimal number of slots and poles, the response surface methodology is adopted to obtain a robust design and make a fair comparison among LPPMVMs with optimum design characteristics using a cost‐effective approach for the fast and reliable optimisation process. The higher gear ratios result in higher thrust force capability. This will help establishing a new route toward faster develpment of advanced LPPMVMs. The power loss models of LPPMVMs are studied to predict their steady‐state and transient thermal behaviours, verifying their stability and safety, while a simple external forced convection method can be utilised. To verify the model, finite element analysis is exploited to confirm the electromagnetic and thermal analysis results and provide a more exhaustive investigation.Peer reviewe

Optimal gear ratio selection of linear primary permanent magnet vernier machines for wave energy applications

Linear permanent magnet vernier generators offer a high capability of force density, making them appealing configurations for wave energy harvesting systems. In absolute terms, the performance of these machines is significantly influenced by the selection of slot/pole combinations based on the magnetic gearing effect. For the first time, this paper aims to investigate the impact of different gear ratios on a wide array of linear primary permanent magnet vernier machines (LPPMVMs) with different slot/pole combinations based on fair criteria to offer a more comprehensive understanding of gear ratio selection. To find the optimal number of slots and poles, the response surface methodology is adopted to obtain a robust design and make a fair comparison among LPPMVMs with optimum design characteristics using a cost-effective approach for the fast and reliable optimisation process. The higher gear ratios result in higher thrust force capability. This will help establishing a new route toward faster develpment of advanced LPPMVMs. The power loss models of LPPMVMs are studied to predict their steady-state and transient thermal behaviours, verifying their stability and safety, while a simple external forced convection method can be utilised. To verify the model, finite element analysis is exploited to confirm the electromagnetic and thermal analysis results and provide a more exhaustive investigation

Design and Characterization for Regenerative Shock Absorbers

L'abstract è presente nell'allegato / the abstract is in the attachmen

A High Thrust Force Spoke-Type Linear Permanent Magnet Vernier Machine with Reduced Thrust Force Ripple

Linear permanent magnet vernier machines (LP-MVMs) have become prevalent in direct-drive applications, such as wave energy harvesting systems and traction applications, owing to their distinctive merit of providing high thrust force at low speeds. In this paper, a novel structure of a double-sided spoke-type LPMVM is proposed, which takes advantage of the magnetic gearing effect. The proposed double-sided linear machine exploits spoke-type permanent magnets (PMs) and one of the stators is displaced as half of the stator tooth pitch to obtain the flux-focusing effect. The thrust force ripple of the proposed spoke-type LPMVM can be decreased by adjusting the stator end-teeth and mitigating the detrimental impact of the longitudinal effect. The proposed LPMVM with adjusted end-teeth offers a noteworthy potential in terms of high thrust force density, increased power factor, and reduced thrust force ripple, which makes it a suitable candidate for various direct-drive applications. The proposed LPMVM is compared with a conventional surface-mounted LPMVM and a spoke-type LP-MVM without adjusting end-teeth to verify the superiority of the new structure. Also, transient and steady-state thermal analyses of the proposed LPMVM are conducted to confirm its thermal stability. A two-dimensional finite element analysis (2D-FEA) is adopted to prove the outstanding characteristics of the proposed double-sided spoke-type linear vernier structure

Development of a single beam SERF magnetometer using caesium atoms for medical applications

This thesis describes the design and implementation of a compact zero-field optically pumped magnetometer for human biomagetic measurements. This project aimed to achieve lower operating temperatures and a higher sensor bandwidth than current commercial rubidium-based equivalent sensors. Through careful selection of the sensing alkali, caesium, and all constituent components of the sensor package design, both of these aims are achieved. All of the required systems and components for a single-beam zero-field magnetometer are discussed, including a high efficiency cell heating and monitoring system, multi-axis field control and the optical detection scheme. Through full understanding and development of these systems, miniaturised and microfabricated versions are developed that facilitate the construction of a sensor package with external dimensions of 25 × 25 × 50 mm3. A number of machine learning tools are developed and applied to directly optimise the sensor’s sensitivity through control of the appropriate operational parameters, yielding a factor of five improvement. These techniques also enabled the investigation of the effect of nitrogen buffer gas pressure on the sensor’s measured sensitivity, demonstrating a linear increase in sensitivity with increasing pressure. The prototype sensor demonstrated a significant advancement in terms of bandwidth achieving a linear frequency response up to ' 900 Hz. The external package temperature of the sensor for prolonged timescales (> 1 hour) maintained a skin-safe temperature (< 41 ◦C), with a biomagnetic field level sensitivity, 90 fT/√ Hz, and compact package footprint, less than a square inch. A practical measurement of the magnetic field of a cardiac signal successfully demonstrates the sensor as a suitable biomagnetic measurement tool.This thesis describes the design and implementation of a compact zero-field optically pumped magnetometer for human biomagetic measurements. This project aimed to achieve lower operating temperatures and a higher sensor bandwidth than current commercial rubidium-based equivalent sensors. Through careful selection of the sensing alkali, caesium, and all constituent components of the sensor package design, both of these aims are achieved. All of the required systems and components for a single-beam zero-field magnetometer are discussed, including a high efficiency cell heating and monitoring system, multi-axis field control and the optical detection scheme. Through full understanding and development of these systems, miniaturised and microfabricated versions are developed that facilitate the construction of a sensor package with external dimensions of 25 × 25 × 50 mm3. A number of machine learning tools are developed and applied to directly optimise the sensor’s sensitivity through control of the appropriate operational parameters, yielding a factor of five improvement. These techniques also enabled the investigation of the effect of nitrogen buffer gas pressure on the sensor’s measured sensitivity, demonstrating a linear increase in sensitivity with increasing pressure. The prototype sensor demonstrated a significant advancement in terms of bandwidth achieving a linear frequency response up to ' 900 Hz. The external package temperature of the sensor for prolonged timescales (> 1 hour) maintained a skin-safe temperature (< 41 ◦C), with a biomagnetic field level sensitivity, 90 fT/√ Hz, and compact package footprint, less than a square inch. A practical measurement of the magnetic field of a cardiac signal successfully demonstrates the sensor as a suitable biomagnetic measurement tool

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

NASA SBIR abstracts of 1990 phase 1 projects

The research objectives of the 280 projects placed under contract in the National Aeronautics and Space Administration (NASA) 1990 Small Business Innovation Research (SBIR) Phase 1 program are described. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses in response to NASA's 1990 SBIR Phase 1 Program Solicitation. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 280, in order of its appearance in the body of the report. The document also includes Appendixes to provide additional information about the SBIR program and permit cross-reference in the 1990 Phase 1 projects by company name, location by state, principal investigator, NASA field center responsible for management of each project, and NASA contract number

Concept study of 20 MW high-speed permanent magnet synchronous motor for marine propulsion

High-speed permanent magnet synchronous machines are of great interest in the applications where high utilization factor and efficiency are required. Depending on application, power requirements change from kilowatts to megawatts. To investigate power limits of high-speed machines, the present feasibility study focuses on a 20 megawatt (MW) electric drive for marine propulsion. However, in addition alternative propulsion systems, ranging 100 kW to 20 MW, have been considered in an attempt to highlight some of the scaling rules that are apparent to high-speed machine considering their specific power level. In marine propulsion, the electric drive has to provide high torque at low speed to the propeller, however at different levels due to pole towing or open water operation. For electric drives, this tends to require high frequencies (large number of poles) as well as high currents. In general, ocean-going ships exist to provide affordable transport for cargo or passengers. In this respect, there exists a range of speeds within which virtually all ocean-going ships have operated and still operate. Within this range of speeds, roughly 10-30 knots, ship propulsion speed, in revolutions-per-minute (rpm), lie within a certain range, up to a couple of hundred rpm. The horsepower range coupled with propulsion rpm makes ship propulsion motor applications a high-torque, slow-speed electric drive. To deliver 20 MW propulsion power at a rotational speed of 150 rpm requires almost 1,300,000 newton meter (Nm) of torque. Emerging ship designs that employ different propulsion, e.g. water jets, may change this. However, in the following decades, ship propulsion motors will remain to be dominated by high torque, slow-speed motors, which are likely to remain for quite some time yet. In this respect, state-of-the-art ship propulsion motors are almost entirely alternating current (AC) synchronous wound field water cooled motors, or AC asynchronous induction motors. This report aims to give a general introduction to the concept of electrically-propelled vessels and presents specifically a feasibility study to a 20 MW high-speed permanent magnet synchronous motor (PMSM) to be used for ship propulsion. Although that also an initial attempt is documented to provide scaling laws for high-speed PM motor ranging from 100 kW to 20 MW. The purpose of this report constitutes a concept study and not an in-depth system analysis that would be required when implementing this technology for an electrical drive in future propulsion systems, such as ships or large vehicles. However, special attention is given to the apparent design challenges for these large high speed electric drives and their possible solutions

A critical survey of power take-off systems based wave energy converters: Summaries, advances, and perspectives

Being one of the most promising renewable energy sources, ocean wave energy (OWE) demonstrates considerable development and application potential. Consequently, various related technologies have rapidly advanced in recent decades, particularly in the field of wave energy converters (WEC). Power take-off (PTO) stands as a vital element within WEC systems. During the planning and implementation of WEC systems, diverse types of PTO systems and control strategies emerge as crucial factors that impact overall power output and stability. To comprehensively review PTO systems, this paper offers a comprehensive overview and discussion of state-of-the-art development status of PTO, including of based structures, working principles and control strategies. In contrast to prior reviews, a more thorough classification and comparison of different PTO systems have been undertaken in this review with the consideration of seven types of PTO systems in total and detailed control strategies for various PTO types. Besides, the proposed framework includes an evaluation and comparison of advantages/disadvantages, application, complexity, and costs for each controller. Lastly, seven invaluable perspectives are proposed for future research