Abstract
This paper presents the development of a condition monitoring method for wet friction clutches which might be useful for automatic transmission applications. The method is developedbased on quantifying the change of the relative rotational velocity signal measured between the input and output shaft of a clutch. Prior to quantifying the change, the raw velocity signal is preprocessed to capture the relative velocity signal of interest. Three dimensionless parameters, namely the normalized engagement duration, the normalized Euclidean distance and the spectral angle mapper distance, that can be easily extracted from the signal of interest are proposed in this paper to quantify the change. In order to experimentally evaluate and verify the potential of the proposed method, clutches’ life data obtained by conducting accelerated life tests on some commercial clutches with different lining friction materials using a fully instrumented SAE#2 test setup, are utilized for this purpose. The aforementioned parameters extracted from the experimental data clearly exhibit progressive changes during the clutch service life and are well correlated with the evolution of the mean coefficient of friction (COF), which can be seen as a reference feature. Hence, the quantities proposed in this paper can therefore be seen as principle features that may enable us to monitor and assess the condition of wet friction clutches.
Highlights
Vehicles equipped with automatic transmissions have gained popularity in recent years
Due to these two mechanisms, the surface pores of the friction material are blocked by the deposition of debris particles and/or the deposition of the automatic transmission fluid (ATF) products
Three dimensionless parameters which are easy to compute, namely the normalized engagement duration, the normalized Euclidean distance and the Spectral Angle Mapper (SAM) distance are proposed in this paper as features for monitoring the condition of wet friction clutches
Summary
Vehicles equipped with automatic transmissions have gained popularity in recent years. As is obvious from its name, an automatic transmission is a transmission which shifts power or speed by itself In this kind of transmissions, wet friction. Wet friction clutches are machine elements enabling the power transmission from an input shaft (driving side) to an output shaft (driven side) during the operation, based on the friction occurring on lubricated contacting surfaces. The clutch is lubricated by an automatic transmission fluid (ATF) having a main function as a cooling lubricant cleaning the contacting surfaces and giving smoother performance and longer life. A change of the frictional characteristics during the clutches’ service life is exposed by a decreasing coefficient of friction (COF) (Ost et al, 2001; Fei et al, 2008). Besides a COF reduction, another aspect which is often associated with the change of the clutch frictional characteristics is the loss of anti-shudder property. It is commonly accepted that the loss of anti-shudder property in a clutch can lead to the occurrence of the stick-slip or/and self excited vibration in the driveline
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