Instantaneous Angular Speed (IAS) has recently appeared as an original and promising tool for monitoring mechanical parts of rotating machines. Mechanisms running under non stationary conditions, such as wind turbine, are especially suited for this method since the issued signal is intrinsically sampled in the angular domain. Although processing tools are developed to enhance its use in the industry, this method is lacking a proper identification of its limitations and this paper aims at precisely understanding two of its main shortcomings: the aliasing and the quantization phenomena. After having presented the measurement method, both the aliasing and the quantization error are theoretically dissected. Formula are proposed to estimate their influence in the spectral observation of the IAS, and a good Signal-to-Noise ratio appraisal for this measurement technique is finally obtained. It can eventually be used as a first guide to conveniently design an IAS based control / monitoring system.

This paper, the first of two companion papers, proposes a general methodology for accurate modeling of the nonlinear behavior of ball and roller bearings. The models give stiffness matrices which can be introduced into standard finite element models of complex mechanical systems, with the aim of predicting mechanical behavior and load and strain distributions. In the case of an “isolated” ball bearing, the results obtained with the proposed approach are compared to results from the literature. Applications are implemented to evaluate the influence of external loadings on the stiffness matrices of tapered roller bearings mounted in a rigid mechanical environment.

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