Analysis of Friction Induced Stability, Bifurcation, Chaos, Stick-slip Vibration and their Impacts on Wiping Effect of Automotive Wiper System

摘要

A 2 DOF nonlinear dynamic model of the automotive wiper system is established. Complex eigenvalues are calculated based on the complex modal theory, and the system stability as well as its dependence on wiping velocity is analyzed. Bifurcation characteristics of frictional self-excited vibration and stick-slip vibration relative to wiping velocity are studied through numerical analysis. Research of nonlinear vibration characteristics under various wiping velocities is conducted by means of phase trajectories, Poincare map and frequency spectrum. The pervasive stick-slip vibration during wiping is confirmed, and its temporal and spatial distributions are analyzed by way of time history and contour map. Duty ratio of stick vibration and statistics of scraping residual are introduced as quantitative indexes for wiping effect evaluation. Results indicate that the negative slop of frictional-velocity characteristic is the root cause of system instability. As the wiping velocity decreases, the vibration state transforms from periodic to quasi-periodic and then to chaos in both high and low velocity ranges. The wiping process is accompanied with prominent stick-slip vibration except when the nominal wiping velocity exceeds 0.725m/s. To increase the wiping velocity can improve system stability, restrain stick-slip vibration and reduce adverse impacts on wiping effect caused by the uneven distribution of scrapings.