Structural analysis and characterization of radial flux PM generators for direct-drive wind turbines

Wind turbine direct-drive generator structures are analysed in order to optimise and reduce mass. A method for modelling key stiffness parameters including a magnetic air-gap stiffness is outlined. Different approaches are used to parametrically calculate structural stiffness and mass. Finite element and analytical techniques are used to model mode 0 and mode 1 deflections and these can be used along with parametric models of electromagnetically active material

A comparative study of methods for modelling the structural stiffness of generator components

Direct-drive generators are low speed electrical machines requiring robust and large supporting structures designed to resist the significant loads present during assembly and operation. Generator structures have to be stiff, especially in the radial direction for radial-flux machines. This paper presents three different structural modelling approaches: finite element, analytical and hybrid (a combination of the results obtained from dimensional studies and finite element analyses). These are used along with models of electromagnetic active material, to parametrically calculate the minimum structural stiffness and mass of the components forming the machine

A lightweight approach for airborne wind turbine drivetrains

Buoyant airborne wind turbines are devices capable of harnessing stronger winds at higher altitudes and with their automated and rapidly deployable system they are suited to niche applications such as emergency power generation. Although much of the wind turbine technology for these systems is common with their ‘grounded’ cousins, an additional design limitation is the requirement for the wind turbine equipment to be lightweight. This paper concentrates on the drivetrain of the wind turbine and the different potential ways of reducing its mass. A buoyant airborne wind turbine with different types of drivetrains, going from gearless to geared systems with distinct gear ratios, has been analysed. Special attention was paid to the mass of the supporting structure of the permanent magnet electrical generator and this was minimized by utilising low density materials, such as composites, in its design. The model showed that a significant reduction in the mass of the drivetrain can be achieved in the gearless case by using materials with a higher ratio of Young’s Modulus to density for the electrical machine supporting structure. For the geared systems, mass decrease was less significant as the gearbox mass had also to be considered. Keywords: Airborne, lightweight, generator structure, composite material

TangiWheel: A widget for manipulating collections on tabletop displays supporting hybrid Input modality

In this paper we present TangiWheel, a collection manipulation widget for tabletop displays. Our implementation is flexible, allowing either multi-touch or interaction, or even a hybrid scheme to better suit user choice and convenience. Different TangiWheel aspects and features are compared with other existing widgets for collection manipulation. The study reveals that TangiWheel is the first proposal to support a hybrid input modality with large resemblance levels between touch and tangible interaction styles. Several experiments were conducted to evaluate the techniques used in each input scheme for a better understanding of tangible surface interfaces in complex tasks performed by a single user (e.g., involving a typical master-slave exploration pattern). The results show that tangibles perform significantly better than fingers, despite dealing with a greater number of interactions, in situations that require a large number of acquisitions and basic manipulation tasks such as establishing location and orientation. However, when users have to perform multiple exploration and selection operations that do not require previous basic manipulation tasks, for instance when collections are fixed in the interface layout, touch input is significantly better in terms of required time and number of actions. Finally, when a more elastic collection layout or more complex additional insertion or displacement operations are needed, the hybrid and tangible approaches clearly outperform finger-based interactions.. ©2012 Springer Science+Business Media, LLC & Science Press, ChinaThe work is supported by the Ministry of Education of Spain under Grant No. TSI2010-20488. Alejandro Catala is supported by an FPU fellowship for pre-doctoral research staff training granted by the Ministry of Education of Spain with reference AP2006-00181.Catalá Bolós, A.; García Sanjuan, F.; Jaén Martínez, FJ.; Mocholi Agües, JA. (2012). TangiWheel: A widget for manipulating collections on tabletop displays supporting hybrid Input modality. Journal of Computer Science and Technology. 27(4):811-829. doi:10.1007/s11390-012-1266-4S811829274Jordà S, Geiger G, Alonso M, Kaltenbrunner M. The reacTable: Exploring the synergy between live music performance and tabletop tangible interfaces. In Proc. TEI 2007, Baton Rouge, LA, USA, Feb. 15-17, 2007, pp.139–146.Vandoren P, van Laerhoven T, Claesen L, Taelman J, Raymaekers C, van Reeth F. IntuPaint: Bridging the gap between physical and digital painting. In Proc. TABLETOP2008, Amterdam, the Netherlands, Oct. 1-3, 2008, pp.65–72.Schöning J, Hecht B, Raubal M, Krüger A, Marsh M, Rohs M. Improving interaction with virtual globes through spatial thinking: Helping users ask “why?”. In Proc. IUI 2008, Canary Islans, Spain, Jan. 13-16, 2008, pp.129–138.Fitzmaurice GW, BuxtonW. An empirical evaluation of graspable user interfaces: Towards specialized, space-multiplexed input. In Proc. CHI 1997, Atlanta, USA, March 22-27, 1997, pp.43–50.Tuddenham P, Kirk D, Izadi S. Graspables revisited: Multitouch vs. tangible input for tabletop displays in acquisition and manipulation tasks. In Proc. CHI 2010, Atlanta, USA, April 10-15, 2010, pp.2223–2232.Lucchi A, Jermann P, Zufferey G, Dillenbourg P. An empirical evaluation of touch and tangible interfaces for tabletop displays. In Proc. TEI 2010, Cambridge, USA, Jan. 25-27, 2010, pp.177–184.Fitzmaurice G W, Ishii H, Buxton W. Bricks: Laying the foundations for graspable user interfaces. In Proc. CHI 1995, Denver, USA, May 7-11, 1995, pp.442–449.Ishii H, Ullmer B. Tangible bits: Towards seamless interfaces between people, bits and atoms. In Proc. CHI 1997, Atlanta, USA, March 22-27, 1997, pp.234–241.Ullmer B, Ishii H, Glas D. mediaBlocks: Physical containers, transports, and controls for online media. In Proc. SIGGRAPH1998, Orlando, USA, July 19-24, 1998, pp.379–386.Shen C, Hancock M S, Forlines C, Vernier F D. CoR2Ds: Context-rooted rotatable draggables for tabletop interaction. In Proc. CHI 2005, Portland, USA, April 2-7, 2005, pp.1781–1784.Lepinski G J, Grossman T, Fitzmaurice G. The design and evaluation of multitouch marking menus. In Proc. CHI 2010, Atlanta, USA, April 10-15, 2010, pp.2233–2242.Accot J, Zhai S. Beyond Fitts’ law: Models for trajectorybased HCI tasks. In Proc. CHI 1997, Atlanta, USA, March 22-27, 1997, pp.295–302.Song H, Kim B, Lee B, Seo J. A comparative evaluation on tree visualization methods for hierarchical structures with large fan-outs. In Proc. CHI 2010, Atlanta, USA, April 10-15, 2010, pp.223–232.Bailly G, Lecolinet E, Nigay L. Wave menus: Improving the novice mode of hierarchical marking menus. In Proc. INTERACT2007, Río de Janeiro, Brazil, Sept. 10-14, 2007, pp.475–488.Zhao S, Agrawala M, Hinckley K. Zone and polygon menus: Using relative position to increase the breadth of multi-stroke marking menus. In Proc. CHI 2006, Montreal, Canada, April 24-27, 2006, pp.1077–1086.Patten J, Recht B, Ishii H. Interaction techniques for musical performance with tabletop tangible interfaces. In Proc. ACE2006, Hollywood, USA, Jun. 14-16, 2006, Article No.27.Weiss M, Wagner J, Jansen Y, Jennings R, Khoshabeh R, Hollan J D, Borchers J. SLAP widgets: Bridging the gap between virtual and physical controls on tabletops. In Proc. CHI 2009, Boston, USA, April 4-9, 2009, pp.481–490.Hancock M, Hilliges O, Collins C, Baur D, Carpendale S. Exploring tangible and direct touch interfaces for manipulating 2D and 3D information on a digital table. In Proc. ITS 2009, Banff, Canada, Nov. 23-25, pp.77–84.Hilliges O, Baur D, Butz A. Photohelix: Browsing, sorting and sharing digital photo collections. In Proc. Horizontal Interactive Human-Computer Systems (TABLETOP2007), Newport, Rhode Island, USA, Oct. 10-12, 2007, pp.87–94.Hesselmann T, Flöring S, Schmidt M. Stacked half-Pie menus: Navigating nested menus on interactive tabletops. In Proc. ITS 2009, Banff, Canada, Nov. 23-25, 2009, pp.173–180.Gallardo D, Jordà S. Tangible jukebox: Back to palpable music. In Proc. TEI 2010, Boston, USA, Jan. 25-27, 2010, pp.199–202.Fishkin K. A taxonomy for and analysis of tangible interfaces. Personal and Ubiquitous Computing, 2004, 8(5): 347–358.Catala A, Jaen J, Martinez-Villaronga A A, Mocholi J A. AGORAS: Exploring creative learning on tangible user interfaces. In Proc. COMPSAC 2011, Munich, Germany, July 18-22, 2011, pp.326–335.Catala A, Garcia-Sanjuan F, Azorin J, Jaen J, Mocholi J A. Exploring direct communication and manipulation on interactive surfaces to foster novelty in a creative learning environment. IJCSRA, 2012, 2(1): 15–24.Catala A, Jaen J, van Dijk B, Jord`a S. Exploring tabletops as an effective tool to foster creativity traits. In Proc. TEI 2012, Kingston, Canada, Feb. 19-22, 2012, pp.143–150.Hopkins D. Directional selection is easy as pie menus. In: The Usenix Association Newsletter, 1987, 12(5): 103.Microsoft Surface User Experience Guidelines. http://msdn.microsoft.com/en-us/library/ff318692.aspx , May 2011.Maydak M, Stromer R, Mackay H A, Stoddard L T. Stimulus classes in matching to sample and sequence production: The emergence of numeric relations. Research in Developmental Disabilities, 1995, 16(3): 179–204

Equivalent electrical circuit derivation of a 7MW offshore wind turbine gearbox

A thermal model of the main mechanical components of the Levenmouth Development Turbine powertrain has been developed in Matlab/Simulink in order to predict their efficiency curve as a function of torque and speed and their electrical analogues of current and frequency. A parametric loss estimation method has been adapted to the turbine gearbox architecture, its oil type and temperature and used to calculate the load and non-load dependent losses due to bearing, mesh, seal, churning and windage and pump losses. The gearbox losses have been expressed as notional equivalent electrical circuit parameters

Long-term trends of midlatitude horizontal mesosphere/lower thermosphere winds over four decades

We analyse 43 years of mesosphere/lower thermosphere (MLT) horizontal winds obtained from a joint analysis of low frequency (LF) spaced receiver lower ionospheric drift measurements from late 1978 through 2008 and VHF meteor radar wind observations since summer 2004 at Collm (51.3∘ N, 13.0∘ E). Due to limitations of the earlier LF measurements, we restrict ourselves to the analysis of monthly mean winds near 90 km, which represents the meteor peak height as well as mean LF reflection heights in the MLT. We observe mainly positive trends of the zonal prevailing wind throughout the year, while the meridional winds tend to decrease in magnitude in both summer and winter. Furthermore, there is a change in long-term trends around the late 1990s, which is most clearly visible in summer MLT winds. We compare these measurements with long-term partial reflection radar observations of winds at 81–85 km over Juliusruh (54.6∘ N, 13.4∘ E) since 1990, and find general qualitative agreement of trends except for summer. The latter can be explained by the different altitudes considered, and by the latitude dependence of the summer mesospheric jet.</p

Design of direct-drive wind turbine electrical generator structures using topology optimization techniques

Reducing the structural mass of low speed multi-MW electrical machines for renewable energy purposes have become an important object of study as with the drop in mass a substantial decrease in the machine capital cost can be achieved. Direct-drive wind turbine electrical generators need very robust and heavy supporting structures able to cope with the demanding requirements imposed by the environment and the forces and moments transmitted by the wind turbine rotor in order to maintain the air-gap clearance open and stable. It is estimated that at least 2/3 of the total machine mass corresponds to the supporting structure. The main aim of this investigation is to minimize the structural mass of a 3 MW direct-drive wind turbine permanent magnet electrical generator, which dimensions have been previously optimized, making use of topology optimization techniques. Easy to manufacture structures made of cast iron capable of complying with the requirements were generated for both rotor and stator