Intelligent manufacturing is developing rapidly nowadays, promoting the efficiency of manufacturing. In comparison, the design process has become a bottleneck in the product life cycle. In order to address this problem, this research develops an intelligent design method based on the automobile transmission system. Firstly, a mathematical model of the coupled vibration between the drive shaft and the main reducer was developed, and the vibration responses of the transmission system were simulated based on this mathematical model. Then, a test rig was developed to measure the vibration responses of the system; the measured results correlated well with the simulation results, indicating that the mathematical model can be used to investigate the coupled vibration between the drive shaft and the main reducer. Furthermore, the multiple parameters of the transmission system were optimized based on the mathematical model using the intelligent optimization algorithm. In particular, software was developed based on the intelligent optimization algorithm for the convenience of analysis, and the optimized results were acquired. The analysis results show that the vibration responses can be reduced when the optimized parameters are applied, indicating that the intelligent design method developed in this research is effective for the intelligent design of transmission system.
Some phenomena of friction induced vibration can be illustrated using negative damping theory, basing on the assumption that the frictional damping of friction induced vibration is constant. The frictional damping of friction induced vibration, however, has not been investigated in details yet. In order to address this problem, a test rig is developed in this research to provide a constant sliding velocity underneath the block. In order to acquire the frictional damping of friction induced vibration, force and vibration should be measured simultaneously. As Fibre Bragg Grating sensing technology can measure distributed systems simultaneously, it is applied to develop the force sensor and acceleration sensor. The natural frequencies of these two sensors designed by finite element method are much higher than the vibration frequency of the test rig acquired with analytical method, ensuring the accuracy of measurement. The force and vibration are measured by the force sensor and acceleration sensor that connected together via one fibre, and the results show that measured dominant frequencies of force and vibration are consistent at various sliding velocities when the block vibrates steadily. In comparison, the dominant vibration frequencies of the test rig acquired by experimental method are slightly lower than the vibration frequency acquired by analytical method due to the existence of frictional damping at the contact interface. A mathematical method for the frictional damping at various sliding velocities is developed, and the results show that the frictional damping is constant when sliding velocity is beyond a certain value, which can verify the assumption that the frictional damping of friction induced vibration is constant, thus complementing negative damping theory.
Wheel squeal is generally attributed to the lateral wheel vibration induced by lateral creepage. It should be noted, however, longitudinal creepage also exists at wheel/rail interface. Given the significance of longitudinal creepage in vehicle dynamics, a test rig that can introduce various longitudinal creepages by changing the teeth number of synchronous pulley is developed in this research, and measurement results show that squeal spectrum has three dominant peaks, whose sound pressure levels decrease with longitudinal creepage. In order to investigate the reason why longitudinal creepage can mitigate wheel squeal, a model of a wheel/rail system is developed in this research to analyse this phenomenon using complex eigenvalue method, and the results show the inner wheel tends to generate unstable vibration at three different vibration modes, correlating well with the dominant peaks of sound spectrum. Further analyses can illustrate the reason why longitudinal creepage can mitigate wheel squeal: the absolute value of effective damping ratio of each mode decreases with longitudinal creepage, so structural damping and frictional damping are less likely to be overcome by negative damping.
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