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

Due to friction characteristics of clutch, the driveline is prone to cause a judder during vehicle starting, and then to cause the vehicle body to vibrate, which affects driving quality. In order to analyze the judder phenomenon, a nonlinear numerical friction model based on the Gaussian friction model is established in this paper. For the driveline of a front-wheel-drive vehicle, a five-degree-of-freedom (5DOF) lumped parameter model including a nonlinear friction element is established. The complex mode of the driveline during the clutch in slip condition is calculated. The key parameters affecting the driveline stability are analyzed. The self-excited judder and pressure-induced judder of the driveline are numerically simulated, and the corresponding causes are analyzed. The nonlinear friction torque of the clutch is also calculated. Furthermore, the effects of the key parameters such as the torsional stiffness and damping of the clutch and drive shaft suppressing the self-excited judder and pressure-induced judder are numerically studied respectively. Compared with the widely used Karnopp friction model, the nonlinear numerical friction model established in this paper comprehensively includes the stribeck effect in slip and the friction torque characteristics in stick. The phenomena of the judder and stick-slip of the driveline during vehicle starting are more accurately simulated. The simulation results are in good agreement with the experimental results, which verify the accuracy and effectiveness of the dynamic model including the nonlinear friction element established in this paper.

Nonlinear Friction and Resistance, Generating Sources of Optimal Points in the Energy Field of Agricultural Aggregates Working Process

The paper presents a point of view on the main sources that can generate some optimal points in the energy field of the agricultural machines working processes. It looks like a possible source of the existence of optimal points in the energetic field of work processes of agricultural machinery and equipment, are the coefficients of friction and specific resistance to deformation of soil. In the news models these coefficients became nonlinear functions. Similar forms are given for all three coefficients and is shown the existence of optimal points. They make some considerations about this method and include results obtained using it.

Micro feed characteristic analysis of a new crawler guide rail dual drive servo system

This paper presents a new type of crawler guide rail dual drive micro feed servo system based on “crawler type” guide rail. Through the innovative design of the crawler guide rail and the change of the working mode, the table, and the crawler type movable rail are relatively static, and the influence of nonlinear friction in low-speed micro feed is eliminated, so that the system can have a lower stable speed limit and realize accurate micro feed control. The Euler-Bernoulli beam element with axial and torsional degrees of freedom is used to describe the axial and torsional vibrations of the ball screw, and the lumped parameter method is used to analyze other parts of the feed system, and the electromechanical coupling dynamic model considering the nonlinear friction is established. The transfer function block diagram is used to characterize the motion relationship of the crawler guide rail dual drive servo feed system. The response difference between the screw single drive system and the new crawler guide rail dual drive system is analyzed by simulation when feeding at constant or variable speed, and the influence of different feed speed on the dynamic performance of the system. The results show that the low speed micro feed performance of the new crawler guide rail dual drive servo system is obviously better than that of the screw single drive system under the condition of constant speed or variable speed.