Mechanism analysis of vehicle start-up judder based on gradient characteristic of Stribeck effect

Abstract

This paper presents a profound mechanism investigation for vehicle start-up judder phenomenon using a combination of experiment and simulation. First, from the experimental analysis, the characteristic frequency of start-up judder is mainly concentrated at about 9 Hz. A 13-degree-of-freedom powertrain branched model is established to numerically reproduce experimental phenomenon. The validity and accuracy of simulation model in reflecting the characteristics of start-up judder are verified by the experimental results in time–frequency domain. Second, through analyzing clutch friction torque, it can be concluded that the closed-loop positive feedback mechanism caused by the negative gradient characteristic of Stribeck effect is the determining factor for the start-up judder. It promotes aggravated fluctuation in rotational speed of clutch driven plate. The introduction process of negative damping that makes powertrain system divergent is explained in detail. Finally, two theoretical measures are proposed to suppress the vehicle start-up judder. One of the measures is to diminish the absolute value of the negative gradient. It weakens the aggravation effect of the closed-loop positive feedback and hence attenuates the start-up judder. Another measure is to change to positive gradient. It forms a closed-loop negative feedback process that causes the almost disappearance of start-up judder. The effectiveness of the two suppression measures verifies the correctness of the start-up judder mechanism proposed in this paper.

Effects of vehicle driveline parameters and clutch judder on gearbox vibrations

“…Previous studies have shown that the natural frequencies of each side of the clutch are excited separately during slipping of the clutch. 9,13 The undamped natural frequencies of the system are calculated by setting the applied torques and damping coefficients to zero. If the damping and loads are eliminated, the equations of motion for the driven side of the driveline can be written as…”

“…The only input in this mechanical system is the torque, which is applied from the engine based on equation (13). It depends on the engine speed.…”

“…More complicated and detailed friction models have been recently applied to study the behavior of a dry clutch, although they do not provide significantly different results. 13,14 There has also been recent research on wet clutch modeling, such as the one in which Wang et al 15 used a simple torsional model to investigate the driveline vibrations caused by a wet clutch.…”

Mechanism-oriented control for suppressing start-up judder of vehicle with automatic dry clutch: Experiment and simulation analysis

“…Under the limitation of tire–road adhesion coefficient, the torque from the driving tires is transformed into the longitudinal tractive force acting on the vehicle body ( m v ), which overcomes the resistance and makes the vehicle accelerate forward. For establishing the motion differential equations of the vehicle powertrain branched model, the method in the literature 22 is cited, as well as transient engine torque. The meanings and values for the symbols in Figures 3 and 4 are listed in Table 1 in Appendix 1.…”

Investigation on friction-induced judder of vehicle driveline based on a nonlinear friction model

“…The uneven contact pressure distributions along the radial direction have a slight influence on clutch judder, while the uneven contact pressure distributions along the circumference contribute to the judder substantially. Yuan and Wu 26 studied the vehicle start-up judder phenomenon using a combination of experiment and simulation. The influence of the negative gradient characteristic of friction coefficient was mainly analyzed numerically through a powertrain branched model.…”