Study On The Nonlinear Vibration Characteristics Caused By Dry Friction Of Auto Braking System

Automobile braking system is the most important safety component of auto. Dry friction effect may appear between the disc and caliper of the disc braking system because of their relative movement during braking, and it also between the drum and the shoes of the drum braking system. The generation mechanism of brake noise is thought to have an important relationship with the dry friction. Stick-slip vibration generates during braking and the Stick-slip vibration will present different vibration characteristics along with the changes of parameters. The work of the braking system is not independent, it coupling with the transmission system and the tires. Thus, it could provide theoretical reference for the determination of design parameters to study on the dynamic characteristics caused by dry friction of auto braking system. It also could provide methods to reduce or eliminate vibration and noise. It takes on certain theoretic meaning and application value.In order to investigate the vibration characteristics of braking system during braking, in this paper, a torsional model of single degree of freedom disc brake system, a torsional model of four degree of freedom disc brake system considering half shaft and tires, a model of three degree of freedom drum brake system considering cam actuation mechanism were established respectively. The three model were investigated by numerical simulation through Matlab and nonlinear theory. Though analysis, the influence rules of parameters on the vibration characteristics was obtained. This paper’s main research contents are as follows:(1)A SDOF torsional vibration model of disc was established. Using the friction model with Stribeck characteristics, the influence rules of the inertias of disc and the differential value of static and kinetic friction coefficient and stiffness and dry friction model slope adjustment parameters and braking pressure on Hopf bifurcation.(2) A pure brake condition4-DOF differential equations of torsional vibration are established in this paper. Base on this model, the low speed bifurcation characteristics of the brake disc and brake sub-system angular velocity difference relative to vehicle speed and the effect of system parameters changing on the bifurcation characteristics are calculated with numerical method.(3) A4-DOF differential equations of torsional vibration are established based on a disc brake system with a new type of brake pad, study the system’s stick-slip vibration characteristics under the action of dry friction, the low speed bifurcation characteristics of the brake disc and brake sub-system angular velocity difference relative to vehicle speed and the effect of stiffness between the each layer of the new brake pad are calculated, find the stiffness matching stable range, provide theoretical basis for optimal design of the brake pad.(4) Comprehensive consideration cam actuating mechanism movement characteristics in the process of heavy truck braking, a3-DOF differential equations of drum brake system are established by considering the torsional vibration of the cam. Based on this model, the limit cycle vibration characteristics of the cam actuating mechanism and the brake shoes are studied with numerical method. The effects of the dry friction coefficient parameters and vehicle speed changing on the limit cycle vibration characteristics.(5)The main work in the paper is summarized, and the further research on the subject is proposed.