| With the increasing degree of precision demand of intelligent mechanical institutions,the requirements for vibration control are also increasing,not only requiring high efficiency of vibration energy absorption,but also the need to achieve adaptive and intelligent demand in a wider frequency band.Therefore,the development of intelligent adjustable vibration damping devices is imperative.As an important means of vibration damping,vibration energy can be absorbed by resonating with the controlled device.Traditional absorbers are simple in structure and low in cost,and can achieve good results for specific frequency excitation,and are widely used.However,such vibration absorbers for multi-frequency excitation of the vibration absorption effect will be due to detuning and sharp deterioration.The adaptive frequency tunable vibration absorber is an intelligent vibration absorption device that can overcome the shortage of traditional vibration absorbers.This vibration absorber can adjust the parameter range in real time based on the feedback data to achieve the adaptive vibration absorption characteristics in a wide frequency range.In this thesis,a new adaptive tunable vibration absorber structure is designed to further improve the vibration absorption capability of the adaptive vibration absorber structure in a wide range of low frequencies and is used for low frequency vibration control of a manipulator.The main research of the thesis is as follows.(1)In the theoretical analysis section,a semi-active variable stiffness absorber based on a leaf spring as the spring element was designed.Firstly,the mechanical modeling analysis of the leaf spring was carried out to obtain the variable stiffness mode of the absorber,and the linear variation of the first-order intrinsic frequency of the absorber in a certain range was realized by designing the structural parameters of the leaf spring.Then,the dynamic characteristics of the absorber were studied,and the optimal damping parameters of the absorber were analyzed based on the fixed-point theory to select the range.Using a commonly used manipulator structure as the controlled object,the dynamics equations of the manipulator specimen were established,and the inherent frequency of the designed manipulator structure was located within the range of frequencies available to the absorber.(2)In the experimental design part,the structure of the absorber was drawn by software,and the experimental model of the absorber was made by 3D printing,and the frequency shift range of the inverter absorber was 16-32 Hz by sweeping experiment.The manipulator structure which can rotate in the axial direction was taken as the controlled object,and the experimental platform was designed.The new adaptive tuned absorber was tested in the frequency range of 16-32 Hz to achieve a 90% absorption effect on the main structure.(3)In the intelligent control part,an adaptive stepwise optimization-seeking control algorithm based on short-time Fourier variation was proposed.By identifying the main frequency of the main system and manipulating the motor to change the inherent frequency of the absorber in real time to achieve the same purpose as the main frequency of the coupling system,thus realizing the purpose of adjusting the inherent frequency of the absorber in real time with the change of the external excitation frequency.The adaptive control effect of the absorber was verified by using simulation combined with experiment.(4)In the structural performance optimization section,the mass of the designed adaptive absorber structure was optimized,and the mass block of the absorber was changed to particle damping,and a variable stiffness particle damped absorber model was designed.Through the theoretical analysis and experimental study,a comparative study with a single variable stiffness absorber was conducted to verify that the particle damped absorber achieves the same effect of broadening the vibration absorption band and improving the vibration absorption capacity with a smaller mass. |
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