Analytical and experimental investigations of dynamic response and parametric instability in flexible cam-follower systems
Abstract
A method to study parametric instability of flexible cam-follower systems, based on Floquet theory, and a closed-form numerical solution algorithm to compute the periodic response of these systems, has been developed to date. These have been applied to an automotive valve train modeled as a single-degree-of-freedom vibration system. Stability of the system has been investigated for three types of follower motion events and four different cam profiles. The results have not only been very interesting but also revealing. This work presents analytical and experimental investigations of a particular flexible cam-follower mechanism. The effects of pressure angle variation on the parametric stability and vibration response of the flexible cam-follower mechanism are investigated. An experimental flexible cam-follower mechanism has been constructed to help validate the earlier analytical findings, and an analytical model similar to that used in previous works, and more truly reflective of the experimental mechanism, is developed. The camshaft speed variation due to the varying moment about the camshaft axis is predicted by use of a rigid-body model, and a method developed to evaluate the parametric steady-state rigid-body response of a cam-follower mechanism. This rigid-body camshaft speed variation is helpful in performing dynamic analysis of the flexible cam-follower mechanism. The effects of the flywheel mass moment of inertia and camshaft torsional vibration are included in a three-degree-of-freedom model. The stability determination method, based on Floquet theory, and the closed-form numerical solution algorithm for computing the periodic response of the multi-degree-of-freedom vibration system are validated with the help of direct integration results. Results from analytical and experimental investigations are compared, for the RDRD and RRR follower motion event types using simple harmonic and 3-4-5 polynomial cam profiles, these comparisons are limited to the follower mass response and camshaft speed variation. Parametric stability investigation results are also presented.
Degree
Ph.D.
Advisors
Bajaj, Purdue University.
Subject Area
Mechanical engineering
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