Day: October 1, 2012

Civil Engineering Graduate Seminar Series; Thursday, October 4, 4:05 PM; Dow 641

Antonio Velazquez, Michigan Tech Civil and Environmental Engineering, PhD candidate in structural engineering

Title: In-operation Output-Only Identification of Wind Turbines Gyroscopic Effects using Parametric-Non-Stationary Subspace System Identification Techniques.

Abstract:
Wind energy has been one of the most growing sectors of the nation’s renewable energy portfolio during the past decade and the same tendency is observed for the upcoming one; however safety and economical concerns have emerged as a result of the newly design tendencies for massive, complex shape, and slender scale wind turbine structures.

One of the most and poorly understood critical effects during the operation of this wind harvesting strcutures is the gyroscopic effect. Gyroscopic action occurs whenever the axis of the rotating body is made to change its direction. Adjusting itself to the current dominating wind direction occurs in an instant of time of critical aerodynamic importance for understanding peak levels of stress and strain imposed to the structure, but also to assure adequate and secure performance of the wind turbine during its operation.
As of today, there is no numerical eigensolution framework that could characterize gyroscopic effects in a unique and general way, and has been remained as an open mathematical problem yet to be solved.

A numerical method based on Arnoldi derivation via Schur decomposition is proposed here for the solution of modal frequencies and mode shapes of the wind turbine. In order to validate results, an in-operation system identification of wind turbine aerodynamics, special attention to gyroscopic effects, is reproduced using output-only vibration acceleration signals. An experiment has been mounted using a distributed wireless sensors network deployed on a Bergey BWC XL.1 wind turbine at UC Davis, CA. Parametric and non-parametric stationary identification analysis is revised in a first stage, followed by a non-stationary time-varying autoregressive model, which is based on a self-proposed modified eigensystem realization (ERA) model.
Advantages of non-stationary identifcation versus stationary counterparts are revealed and discussed, then compared with the analytical solution derived from complex-number modal analysis the gyroscopic mathematical model is composed of.

Tom Heberlein, an environmental sociologist, will give two presentations on Thursday, Oct. 18. Heberlein is professor emeritus in the Department of Community and Environmental Sociology and the Gaylord Nelson Institute of Environmental Studies at the University of Wisconsin-Madison, and currently a visiting professor in the Department of Wildlife, Fish and Environmental Studies in the College of Forestry in Umea, Sweden.

Here are the details:

A River Runs through it: Lessons from Rivers and Lakes
2 to 4 p.m., Great Lakes Research Center
Book signing, informal discussion with refreshments to follow. Open to the public.

Navigating Environmental Attitudes: Lessons from Wolves
7 p.m., Forestry G002
Book signing with refreshments to follow. Open to the public.

This event was sponsored by the Department of Social Sciences, the Environmental and Energy Policy Program, the Great Lakes Research Center, the Lake Superior Stewardship Initiative, the Keweenaw Land Trust, the Michigan Tech Center for Water and Society and the Keweenaw Unitarian Universalist Fellowship.

The Green Lecture Series program is partially funded with a grant from the League of Women Voters of the Copper Country, the Friends of the Land of Keweenaw and the UP Environmental Coalition.