Model-based Signal Processing Methods Research Articles

Signal processing techniques for rolling element bearing spall size estimation

Abstract This paper proposes signal processing techniques to extract entry and exit points from the bearing vibration signal for spall size estimation. The entry point is the start point of a low frequency response when a rolling element enters a localized defect on the raceway, which is contaminated with background noises and difficult to identify. An empirical model based signal processing method is proposed to effectively identify the entry point. The Variational Mode Decomposition (VMD) is applied to the bearing entry signal for more accurate estimation. Differentiation technique is used to identify the high frequency exit point with more reliable threshold values for automatic diagnostics. Then, based on defect size estimation models for both inner and outer race defects, the spall size can be estimated. The proposed methodology is validated on a machine tool spindle’s bearing system. Experimental results show that the proposed signal processing techniques provide less biased results with respect to spindle speed and more precise estimation.

Inversion of Internal Wave-Perturbed Sound-Speed Field Via Acoustic Data Assimilation

Model-based signal processing methods, such as matched-field processing, are concerned with exploiting the combination of the sound propagation physics in an ocean waveguide and the observation data. As such, they require accurate knowledge of the ocean acoustic environment. This paper presents an approach of environmental inversion via acoustic data assimilation (ADA), intended specifically to reconstruct the sound-speed field perturbed by linear internal waves. It exploits a variety of information sources, including direct local sound-speed measurements, an internal wave model, a full field acoustic propagation model, and acoustic pressure measurements. Compared to the previous work on ADA, four important improvements have been made: 1) a linear internal wave model is included; 2) a more realistic shallow-water environment from the Shelf Break PRIMER 1996 experiment is considered in the numerical simulations; and 3) effect of the sediment on acoustic propagation is considered in the inversion algorithm. The results further demonstrate the validity of the ADA approach.

Particle sizing by photon correlation laser Doppler anemometer in the submicron/nanometer size range

A particle sizing algorithm is developed for nanoparticle sizing with laser Doppler anemometry/velocimetry systems. A model-based signal processing method is used to estimate the particle size from the autocorrelation curve corresponding to a single particle transit. Two kinds of figures of merit functions are combined to improve the sensitivity. The optimal setup parameters (refractive index, wavelength, and observation direction) and trajectory error are investigated in independent simulation studies. At 514-nm illumination wavelength, the most sensitive size region is found below 300 nm down to the sizing limit (20 photons on average from a single particle transit). The required laser power is searched for by the lower sizing limit based on the calibration measurement. The size estimation of a polystyrene sphere particle of 50 nm diameter requires at least 123-kW/cm2 laser power density at 350 nm, while 587 kW/cm2 at 514 nm is used in the studied system.

A reduced model of pulsatile flow in an arterial compartment

In this article we propose a reduced model of the input–output behaviour of an arterial compartment, including the short systolic phase where wave phenomena are predominant. The objective is to provide basis for model-based signal processing methods for the estimation from non-invasive measurements and the interpretation of the characteristics of these waves. Due to phenomena such that peaking and steepening, the considered pressure pulse waves behave more like solitons generated by a Korteweg–de Vries (KdV) model than like linear waves. So we start with a quasi-1D Navier–Stokes equation taking into account radial acceleration of the wall: the radial acceleration term being supposed small, a 2scale singular perturbation technique is used to separate the fast wave propagation phenomena taking place in a boundary layer in time and space described by a KdV equation from the slow phenomena represented by a parabolic equation leading to two-elements windkessel models. Some particular solutions of the KdV equation, the 2 and 3-soliton solutions, seems to be good candidates to match the observed pressure pulse waves. Some very promising preliminary comparisons of numerical results obtained along this line with real pressure data are shown.