Study On Multi-limit Cycle Shimmy Mechanism Of Dual-front Axle Heavy Trucks Steering System

The dual-front axle steering system is widely used in heavy truck due to low manufacturing cost and convenient operation.However,self-excited shimmy can be found in practical engineering application,which seriously affects the control stability and driving safety of heavy truck.Self-excited shimmy problem is one of the tough problems that have always been puzzling in the automotive industry.At present,many scholars devote themselves to the study of self-excited shimmy of vehicles,but research on self-excited shimmy of heavy truck dual-front axle steering system is still rare currently.Therefore,on the basis of previous studies,the paper further researches the mechanism of multi-limit cycle vibration of dual-front axle steering system.In this paper,a 9 degree of freedom dynamics model including two nonlinear factors of tire friction and dry friction is established.MATLAB software is used to do numerical simulation and analysis to reproduce the multi-limit cycle shimmy phenomenon of dual-front axle steering system.Secondly,the paper studies on the influence of the kingpin caster angle,its matching and dry friction torque,the results show that the influence of the first kingpin caster angle is greater than the second bridge,and increasing dry friction torque appropriate can effectively restrain system multi-limit cycle shimmy.Finally,through simulating and analysis the influence of the function expression of the dry friction model on the multi-limit cycle shimmy.It is found that the multi-limit cycle shimmy of the system has nothing to do with the expression of the function of the dry friction model.It is also found that the friction parameters of the whole dry friction model have the same effect on the system multi-limit cycle shimmy,in other words the system multi-limit cycle shimmy corresponding to the range of the speed range can be reduced by reducing the attenuation coefficient or the difference of the dynamic and static friction coefficients.The influence of the random friction coefficient range on the system multi-limit cycle shimmy is also investigated.It is found that the multi-limit cycle shimmy is not affected by the friction coefficient range.