Study Of Vibration Control And Optimization To A Low-speed Truck Cab

With the rapid development of society,more and more people pay attention to the riding comfort of vehicles.In Guangxi,a company’s low-speed truck with strong carrying capacity,power and other characteristics are widely used.But because of in the normal work of the cab vibration is relatively large,which seriously affected the cab staff working environment.In order to improve the competitiveness of the market,this paper uses a combination of CAE analysis and experimental test analysis method,to study the vibration of the cab,the main contents of this paper are as follows。Firstly,the vibration test and analysis of the cab of the test prototype.Useing LMS and PCB acceleration sensors to collect vibration signals at the mount of the cab and the seat rails,the data were analyzed by frequency spectrum in the LMS.Test.Lab software.A relatively large frequency was found in the vibration signal data of the seat rail.And through the coherence analysis of the signal between the seat rail and the mounting point of the cab,it can be seen that the coherence coefficient of the vibration signal of them is more than 0.8 at the relatively large vibration frequency,indicating that the energy of the excitation signal at this frequency is not well attenuated.Secondly,the static stiffness and mode of the cab are studied and analyzed.The finite element model of the white body of the cab is established,the free-mode simulation and experimental tests were carried out,the results of comparison are basically consistent,the model can be used for subsequent dynamic and static studies.The analysis of static bending and torsional stiffness of the white body was carried out,the results showed that the stiffness was relatively low.In order to accurately analyze the cab Trimmed body modal,the free and constrained modal simulation analysis is carried out,the results show that the first order torsional modal frequency is within the excitation frequency range of idling.To verify this result,Operational Modal test was carried out under idling conditions,It can be seen that the first order mode in the range of the engine idling excitation frequency is indeed the torsional mode,this is consistent with the results of the simulation analysis.So,The main reason for the vibration at the idle speed of the cab is that the first-order torsional frequency resonates with the frequency of the engine idling.Then,the characteristics of the transmission structure of the cab are studied and analyzed.The excitation signal at the measured mount is used as the excitation of the finite element simulation,and the transfer function theory is used to calculate the transfer function of the excitation point from the excitation point to the seat installation point.The transfer function curve is very unsmooth near the frequency of its seat rail vibration and there is a large peak,indicating that its structural transfer characteristics do exist problems.And the dynamic test and simulation analysis of the mount point of the cab are carried out,by analyzing the results of them can be seen at the mount point of the cab of the dynamic stiffness is relatively low.Through the above analysis,the transmission characteristics of the cab is indeed poor,which is caused by the cab vibration is too large one of the reasons.Finally,the structure of the cab is optimized and validated.To improve the structural characteristics of the cab vibration,Choosing two options for optimization:1.In order to improve the first mode frequency of the free mode of the cab,the topology optimization technique is used to optimize the white body of the cab;2.To enhance the static stiffness of the cab as the goal,the application of topology optimization technology to optimize t the white body of the cab.Then refer to the topological results of the two schemes and reinforce the cab structure accordingly,to verify the feasibility of the enhanced program,the dynamic and static analysis of the model is carried out.The simulation results before and after optimization are compared,the results of the comparison show : t the first order modal of the white body of the cab increased by 22%,the bending stiffness of the white body of the cab increased by 23.6%,the torsional stiffness of the white body of the cab increased by 22.6%,the first order modal of the trimmed body modal increased by 20%,and the transfer function curve and the dynamic stiffness curve are smoother,the optimization program has achieved good results,in order to improve the driver’s working environment provides an optimized direction.