Studies On Parameter Identification Of Nonlinear Parameter-Excited Vibration System

In the past, when scholars researched the dynamical characteristic of one material structure, they always started with the control equation. And then used some methods both in property and quantity to determine the dynamical characteristic. However, for some new materials, such as the nanometer composite, it is not enough to only use the theoretical methods to constitute dynamical equation of the system. Because the material parameters and the relationship between stress and strain is unknown. Combining theory with experiment is one of the means to constitute dynamical equation of the system. This paper is just under such background and directions, researching the parameter identification method of the nonlinear systems and the constitution of the dynamic equation by combining theory with experiment. The contents of this paper are:In chapter 1, we introduce the current research progress of the nonlinear parametrically excited systems. Then give a summarization of parameter vibration in engineering project and the current situation of the experiment research. Finally, the identification procedure of Harmonic Balance Nonlinearity Identification (HBNID) is given.In chapter 2, Harmonic Balance Nonlinearity Identification (HBNID) is extended to multi-degree-of-freedom free vibration systems. We have researched the identification result under different measuring signal. Have considered that the noise is impossible to avoid during the experiment, we have put White Gaussian Noise into the response, and see what will happened to the identification outcomes. In order to test the accuracy of HBNID, the methodology is used to identify a theoretical two-degree-of-freedom model. Finally, we compare the identification result between the two different measuring, signals, and have verified the effectiveness of this method.In chapter 3, the Harmonic Balance Nonlinearity Identification (HBNID) is extended to multi-degree-of-freedom parameter-excited vibration systems. At this chapter, we only consider to measure the displacement for identifying parameters. In order to test the accuracy of HBNID, the methodology is used to identify a theoretical two-DOF system with cubic non-linearity to a parametric excitation. We can conclude from the simulation that when we only identify one parameter, the result is very accurate but when we identify more parameters the result's accuracy come down.In chapter 4, we use the nonlinear system identification methodology based on the principle of harmonic balance and combine theory with experiment to constitute dynamical equation of the nanometer composite beam. For the sake of verifying the reliable of this dynamical equation, the theoretical result and the experimental result have been compared. The contrast shows that the dynamical equation is closed to the real system.Finally the concluding remarks are employed to close this paper.