1,412 research outputs found
The application of parameter sensitivity analysis methods to inverse simulation models
Knowledge of the sensitivity of inverse solutions to variation of parameters of a model can be very useful in making engineering design decisions. This paper describes how parameter sensitivity analysis can be carried out for
inverse simulations generated through approximate transfer function inversion methods and also by the use of feedback principles. Emphasis is placed on the use of sensitivity models and the paper includes examples and a case study involving a model of an underwater vehicle. It is shown that the use of sensitivity models can provide physical understanding of inverse simulation solutions that is not directly available using parameter sensitivity analysis methods that involve parameter perturbations and response
differencing
Spectrograms of ship wakes: identifying linear and nonlinear wave signals
A spectrogram is a useful way of using short-time discrete Fourier transforms
to visualise surface height measurements taken of ship wakes in real world
conditions. For a steadily moving ship that leaves behind small-amplitude
waves, the spectrogram is known to have two clear linear components, a
sliding-frequency mode caused by the divergent waves and a constant-frequency
mode for the transverse waves. However, recent observations of high speed ferry
data have identified additional components of the spectrograms that are not yet
explained. We use computer simulations of linear and nonlinear ship wave
patterns and apply time-frequency analysis to generate spectrograms for an
idealised ship. We clarify the role of the linear dispersion relation and ship
speed on the two linear components. We use a simple weakly nonlinear theory to
identify higher order effects in a spectrogram and, while the high speed ferry
data is very noisy, we propose that certain additional features in the
experimental data are caused by nonlinearity. Finally, we provide a possible
explanation for a further discrepancy between the high speed ferry spectrograms
and linear theory by accounting for ship acceleration.Comment: 21 pages, 10 figures, submitte
Identification of the dynamic characteristics of nonlinear structures
Imperial Users onl
Multicriteria fuzzy-polynomial observer design for a 3DoF nonlinear electromechanical platform
This paper proposes local fuzzy-polynomial observer discrete-time designs for state estimation of a nonlinear 3DoF electromechanical platform (fixed quadrotor). A trade-off between H∞ norm bounds and speed of convergence performance is taken into account in the design process. Actual experimental data are used to compare performance of the fuzzy polynomial design with classical ones based on the Takagi–Sugeno and linearized models, both using the same optimization criteria and design parameters.The authors are grateful to the financial support of the Spanish government under research project DPI2011-27845-C02-01 and FPI Grant BES-2009-013882, as well as to Generalitat Valenciana grant PROMETEOII/2013/004. The authors are also grateful to Ph.D. students A. Berna, J. Guzman and associate professor P.J. Garcia for their laboratory data acquisition work.Pitarch Pérez, JL.; Sala Piqueras, A. (2014). Multicriteria fuzzy-polynomial observer design for a 3DoF nonlinear electromechanical platform. Engineering Applications of Artificial Intelligence. 30:96-106. https://doi.org/10.1016/j.engappai.2013.11.006S961063
Experimental application of Takagi-Sugeno observers and controllers in a nonlinear electromechanical system
[EN] In this paper, a systematic methodology to design fuzzy Takagi-Sugeno observers and controllers will be used to estimate the angular positions and speeds, as well as to stabilise an experimental mechanical system with 3 degrees of freedom (fixed quadrotor). Takagi-Sugeno observers and controllers are compared to observers and controllers based on the linearized model, both designed with the same optimization criteria and design parameters. Experimental results confirm that Takagi-Sugeno models and observers behave similarly to linear ones around the linearization point, but have a better performance over a larger operating range, as intuitively expected.The work of Zs. Lendek was supported by a grant of the Romanian National Authority for Scientific Research, CNCS UEFISCDI, project number PN-II-RU-TE-2011-3-0043, contract number 74/05.10.2011. Spanish authors are grateful to grants DPI2011-27845-C02-01 (A. Sala), DPI2011-27845-C02-02 (R. Sanchis), DPI2011-28507-C02-01 (P. Garcia) from Spanish Government, and PROMETEOII/2013/004 (A. Sala, P. Garcia) from Generalitat Valenciana.Lendek, Z.; Sala, A.; García Gil, PJ.; Sanchis Llopis, R. (2013). Experimental application of Takagi-Sugeno observers and controllers in a nonlinear electromechanical system. Control Engineering and Applied Informatics. 15(4):3-14. http://hdl.handle.net/10251/150453S31415
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