Civil Engineering Graduate Seminar Oct 4

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.

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.