| In this paper,a study on vibration characteristics of a John Deal type 1204 tractor is carried out.The Fourier transform analysis and wavelet analysis of tractor seat are carried out respectively.The wavelet analysis of the tractor body is finished.The wavelet analysis and chaotic identification of the tractor axle are done.Based on the analysis of each part of the tractor as a whole,the vibration characteristics of the whole engine are analyzed comprehensively.This paper provides a theoretical support for study of tractor vibration research and tractor vibration damping.Conclusions drawn from this paper are as follows:(1)Research on vibration of tractor seat.Seat vibration is analyzed by fast Fourier transform.Factors that influence vibration of tractor seat include terrain condition,running speed and vehicle condition.Variation of amplitude of tractor seat with increase of speed is:1,first increase and then decrease,and then continue to increase as speed increases.2,when tractor speed is within speed range of resonance frequency,vibration intensity in empty car condition is smaller than that under load condition.When speed is greater than resonance frequency,vibration speed increases slowly under condition of empty.In order to achieve purpose of reducing vibration of tractor,we can not only adopt method of reducing speed to make tractor speed close to 1.40 m/s as much as possible,but also increase weight of tractor appropriately.Seat vibration is low frequency,natural frequency range is 2.48Hz-3.144 Hz,vibrative frequency is 1.25Hz-1.65 Hz at this time,so tractor vibration at low speed will produce resonance phenomenon.When designing tractor seat,you should avoid sensitive frequency range of tractor driver so that you can improve comfort.Experimental results provide theoretical support for seat design.(2)Research on vibration signal of tractor.Excitation signal of tractor axle,tractor body and seat is detected by wavelet transform.Signal strength is attenuated about 212 times when road excitation signal is transmitted from the axle to the seat.Signal strength is attenuated about 12 times during the empty vehicle when road excitation signal is transmitted from the axle to the seat.Increasing counterweight properly for tractor can improve performance of suspension damper,and make suspension damper more effectively block vibration caused by the ground excitation signal.(3)Research on side overturning of tractor due to severe vibration when tractor passes through barrier.When tractor meets a obstacle on one side of tractor,it should be driven as low as possible to reduce tractor vibration caused by road surface obstruction.Tractor encountered obstacles in one side when tractor under load at rear axle vibration acceleration is about 46 g,empty case at rear axle vibration acceleration 44 g,shows that by increasing weight change of tractor vibration intensity is not obvious,increasing weight can’t achieve purpose of damping.At this point,tractor speed can’t exceed v=5.14m/s,otherwise,tractor may occur rollover.(4)Research on singularity of tractor vibration signal.Detailed vibration signal of tractor under 2 frequency wavelet resolutions is analyzed by wavelet decomposition.Singularity of vibration signal is detected in detail signal of 2 level wavelet decomposition.Singularity of detail signals of wavelet decomposition at two stage of axle is mainly due to transmission system inside axle.In order to reduce vibration caused by tractor transmission system,on one hand need regular maintenance of transmission system,on other hand,it is necessary to study stability of transmission system,including study of axle differential,gearbox,transmission shaft and other properties.(5)Nonlinear study of tractor vibration.By means of chaos analysis,we know that correlation dimension D is between 1.9534 and 2.0800,not integer.It is proved that vibration signal of bridge has chaotic characteristics;When Lyapunov exponent is between 1.4395 and 1.5128,and is greater than zero,vibration of back of tractor is in chaos.Vibration of rear axle of tractor is in chaos,and vibration signal of tractor is in a state of chaos.Results of this chapter can be applied to tractor when tractor safety alert,after a bumpy road,chaotic analysis method combining computer hardware system can be predicted in advance to the tractor jump,warning tractor driver safe driving,avoid danger of tractor out of the ground. |
PDF Full Text Request