Min-Max Probe Placement and Extended Relaxation Estimation Method for Processing Blade Tip Timing Signals

• Measuring blade displacement using blade tip timing (BTT) enables nonintrusive monitoring of rotating blades and their vibration frequencies. The average sampling frequency of BTT is the product of the number of measurement probes and rotational frequency, which is usually far less than the blade natural frequency due to the limited number of probes. The pattern of the aliasing that arises from under-sampling is rather complex under uneven probe placement. In this article, we consider a probe placement design that is based on minimizing the maximum sidelobe level of the spectral window to suppress the aliasing frequencies in the spectrum. Based on a signal model containing both asynchronous and synchronous sinusoids, we then develop an extended version of the RELAX method (ERELAX) to estimate their parameters simultaneously. Model order selection rules are also used to determine the number of asynchronous sinusoids. The frequency ambiguity that arises from periodic nonuniform sampling (PNS) is also discussed based on the convolution in the frequency domain. Numerical simulations and results of a curved-blade experiment show that the proposed method has a mean squared estimation error less than 25% of that of two state-of-the-art methods (Block-OMP and MUSIC), requires 40% of the data length needed by the latter methods to achieve the same estimation accuracy, and has the smallest standard deviation of the reconstruction errors. Simulation codes are available at https://github.com/superjdg/RELAX_BTT.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Signalbehandling (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Signal Processing (hsv//eng)

Keyword

Probes

Blades

Vibrations

Vibration measurement

Frequency synchronization

Time-frequency analysis

Frequency estimation

Blade tip timing (BTT)

frequency ambiguity

min-max placement

model order selection

relax

Publication and Content Type

ref (subject category)

art (subject category)