Experimental Investigation on Dynamic Characteristics of a FEAD System: Affected by Serpentine Belt Length

Serpentine belt is widely used in the front end accessory drive (FEAD) system of automotive engine. Experimental setup and dynamic behaviors of a FEAD system are demonstrated in this paper. Some dynamic characteristics are investigated, subjected to multifrequency excitations and different crankshaft (CRK) loads. Experimental results show that the parametric instability of belt transverse vibration occurs mainly in the frequency regions of secondary resonance, and the instability regions are shifted to lower frequencies according to the increasing of CRK speed. With the same CRK load and speed, the rotational angle of tensioner arm, the hubload of tensioner pulley and the slip rate of ALT pulley in the short-belt system are smaller than that in the long-belt system. But with the increase of CRK loads, the parametric instability of belt transverse vibration in the short-belt system is stronger than that in the long-belt system, the higher CRK speed, the greater belt transverse displacement.

Parametric Instability of an Axially Moving Belt Subjected to Multifrequency Excitations: Experiments and Analytical Validation

This paper experimentally investigates the parametric instability of an industrial axially moving belt subjected to multifrequency excitation. Based on the equations of motion, an analytical perturbation analysis is achieved to identify instabilities. The second part deals with an experimental setup that subjects a moving belt to multifrequency parametric excitation. A data acquisition technique using optical encoders and based on the angular sampling method is used with success for the first time on a nonsynchronous belt transmission. Transmission error between pulleys, pulley/belt slip, and tension fluctuation are deduced from pulley rotation angle measurements. Experimental results validate the theoretical analysis. Of particular note is that the instability regions are shifted to lower frequencies than the classical ones due to the multifrequency excitation. This experiment also demonstrates nonuniform belt characteristics (longitudinal stiffness and friction coefficient) along the belt length that are unexpected sources of excitation. These variations are shown to be sources of parametric instability.