Vibration-Suppresed Mechanism With Time Delay And The Applications In Vehicle Engineering

The core ideology of the time delay damper theory is to achieve better vibration suppression with the active use of delay. While the traditional research about time delay mainly regards it as the adverse factor and focuses on the elimination of the negative effects, the time delay damper theory strives to discover and utilize its advantages. Time delay damper theory is a significant innovation and is an important breakthrough in time delay phenomenon in epistemology. In this thesis, the time delay damper theory was adopted to investigate the utilization of delay items in the vehicle engineering.First, the Lyapunov stability theory was employed to analyze the stability of vehicle dynamics models, the stable region for arbitrary time delay was given and the critical time delay was obtained with delayed active control forces equipped. The weighted objective function was confirmed through the use of Fourier Transform, and with the optimization methods, the optimum feedback gains and the corresponding time delays were obtained associated with the frequency of the external excitation, which provided a universal solution for the control parameters.Secondly, using the quarter-car model, idling model and half-car model, the single delay and dual delays systems were investigated in contrast to analyze the difference in the stability and the vibration reduction caused by the different choice of the feedback state. In addition, the "bandwidth" problem and the influences on the tires were explored. Two significant conclusions were drawn that an arbitrary time delay can lead to instability in a certain feedback loop of a certain dynamic system; in addition, it came up with a qualitative conclusion that a feedback state from a lighter item frequently brings about a better performance in the multi-degree of freedom systems.Finally, the time delay damper theory was applied to a dynamic system excited by the random road spectrum, through the use of the Pade approximation, optimization method and the linear quadratic optimum control method. This work presented a universal solution to handle the multi-frequency problems, achieved ideal vibration suppression and eliminated the increase in the tire vibration in contrast to the optimum control without time delay.The exploration in this thesis showed that time delay damper theory can possess preferable application value in the vehicle engineering. Time delay phenomenon has duplicity also; the reasonable handling process can transform its adverse effects into beneficial effects which prove an advance in methodology.