Research On Vibration Control Of Conveying Fluid Pipe Based On Energy Disturbance Analysis Theory

As an indispensable basic structure in the substance and energy transmission and exchange system,the conveying fluid pipe is widely used in the modern industrial field.The complex application environment and usage requirements in engineering practice make the conveying fluid pipe system inevitably produce excessive vibration.To solve this problem,a large number of vibration control methods based on the dynamic model of conveying fluid pipe systems have emerged.As far as the existing methods are concerned,the passive vibration controller based on a nonlinear energy sink has achieved wide attention and research due to its wide frequency,adaptive,high reliability and good vibration control performance.However,the nonlinear characteristics of the nonlinear energy sink and the complex coupling with the fluid conveying pipe system make the verification of its vibration control effectiveness dependent on numerical methods and lack of necessary theoretical support.For this reason,based on the energy disturbance analysis theory,a global stability analysis method is proposed to study the vibration control performance of nonlinear energy sink.This method has important theoretical value and guiding significance for analyzing the stability of similar systems such as axially moving beams.In addition,the problems of larger structural mass and the oscillation of free end have limited the application of nonlinear energy sink controller in engineering practice and seriously affect its vibration control performance.Therefore,reducing the structural mass of the nonlinear energy sink,eliminating its free end,and improving its vibration control performance has strong research significance and application value.The main work of this thesis is summarized as follows:For the nonlinear system such as conveying fluid pipe-nonlinear energy sink system,the partial differential system model is approximated to an ordinary differential model containing gradient information through the Galerkin approach and a potential energy function of this model.Based on the ordinary differential model and the energy disturbance analysis theory,the global exponential stability of the conveying fluid pipe-nonlinear energy sink system is analyzed under Lyapunov meaning.Finally,a conveying fluid pipe displacement experimental platform is designed and built to verify the proposed method.In view of the limitation of the structural mass and the usage space of the controller in engineering practice,two different solutions are given: parallel nonlinear energy sinks and inerter enhanced nonlinear energy sink.The former is used to reduce the structural mass of the controller,improve the control performance at higher flow velocity and enhance the robustness of the controller.The purpose of the latter is to eliminate the free end of the nonlinear energy sink,control the vibration of conveying fluid pipe at high subcritical flow velocity and further reduce the structural mass of the controller.Based on the proposed stability analysis method,the effectiveness and advantages of the two controllers are analyzed and discussed,and the structural mass and nonlinear stiffness of the proposed controllers are optimized according to the convexity characteristics of the established energy functional.For the influence of parameters on the characteristics of the conveying fluid pipe system and the essential characteristics of modal frequency and modal amplitude of the dynamic system,a parameter sensitivity analysis method for the conveying fluid pipe system based on the amplitude-frequency curve is proposed in this thesis.The method consists of the following steps: Firstly,Galerkin method is used to approximate the high-order partial differential model of the conveying fluid pipe system under harmonic load to an ordinary differential model,and then the amplitude-frequency curve of the system is obtained by harmonic balance method and matrix analysis technique.Finally,the amplitude-frequency characteristics of the conveying fluid pipe system under different parameter values are analyzed by using the analytical solution of the amplitude-frequency curve,and the parameter sensitivity of the system is obtained.The results show that the modal frequency of the conveying fluid pipe system can be significantly changed by the change of the dimensionless fluid velocity,thus affecting the performance of the controller.