Analysis And Optimization Of Vibration Characteristics Of A Type Of Chassis Dynamometer

As the carrier of vehicle dynamic performance,fuel economy and environmental testing,chassis dynamometer's vibration characteristics directly affect its own service life,vehicle testing accuracy and workshop noise level.In the actual process of vehicle detection,it is found that there exists the phenomenon of accelerated jitter shock by a certain type of chassis dynamometer used in the detection station.Based on this background problem,the vibration characteristics of the chassis dynamometer are analyzed and optimized from the perspective of rotor system dynamics.Based on the Solidworks software,3D modeling is carried out according to the actual proportion of the chassis dynamometer,the subtle features are equivalently simplified,the coupling relationship between components is equivalently replaced,and the 3D model of the multi-rotor system including the drums is extracted.Based on the idea of finite element analysis,the rotor system of chassis dynamometer is modeled by Abaqus software.Through the theoretical and empirical analysis,the equivalent stiffness of bearing support is numerically solved,and the equivalent stiffness is replaced by the spring-damping element in the finite element model.The natural characteristics of the system are analyzed,and the natural frequencies and corresponding modes are extracted.According to the theory of harmonic response analysis,the forced vibration of the rotor system is analyzed,and the frequency-domain characteristic curve of displacement is obtained.Based on the theory of gyro effect,the critical speeds of each order of the system with and without gyro moment are calculated by the Campbell diagram method.Considering the dynamic coupling relationship between the platform and the vehicle,the ADAMS dynamic model of chassis dynamometer and the vehicle under test is established.Based on the basic idea of ADAMS software modeling,a simplified coupling model between rotors and driving wheels is used for dynamic simulation,and the time-domain characteristic curve of vibration acceleration of a bearing housing is obtained.The vibration acceleration acquisition and speed(also drum speed)acquisition tests are designed,the results of finite element simulation and dynamic simulation are verified by real vehicle tests,the error between simulation data and real vehicle test data is analyzed,and the reasons for the error are summarized.Finally,based on the idea of vibration system frequency modulation,the vibration characteristics of the rotor system of chassis dynamometer are optimized,and the correctness of the optimization measures is verified by the frequency-domain and time-domain characteristic curves simulated by Abaqus and ADAMS,respectively.The results show that the problem of accelerated jitter shock in the working process of the chassis dynamometer is caused by the system resonance that the critical speeds corresponding to the low order natural frequencies of the system is within the operating speed range of the dynamometer.By increasing the bearing support stiffness to 109 order of magnitude,the critical speed of system can be moved out of the working speed range of the chassis dynamometer,so as to avoid system resonance and improve the vibration and noise level of the studied chassis dynamometer.