Identification of slip load, friction force and external force using unscented kalman filter for frictionally damped turbine blades

An Unscented Kalman Filter (UKF) based technique has been developed for parameter estimation of turbine blades with friction dampers. The technique is based on integration of Newmark method, an iterative numerical integration method for structural dynamics, with UKF. The technique has been implemented on a single mode model of a turbine blade with a friction damper. Two approaches are developed. First, both steady state vibration and known forcing data are used to estimate parameters such as friction force and slip load. These parameters are treated as additional states of the system and the augmented state space model is used with UKF to estimate parameters. In the second approach, transient vibration response of the system is used to estimate slip load, friction force and unknown sinusoidal forcing function as well. The frequency of sinusoidal external excitation is assumed to be known. The unknown magnitude and phase of the external excitation are represented as a solution of a second order differential equation, which leads to two additional states in the model. Numerical results are presented for both the cases of known and unknown forcing functions in the presence of modeling and measurement errors. A discussion of these results is presented and the validity of the new approach is corroborated.