Active Vibration Isolation Technology Based On Negative Stiffness Of Bistable Flexion Beam

Ultra-precision vibration isolation technology has been applied to many high-precision fields to achieve the isolation of micro-environmental vibration.In particular,for ultraprecision manufacturing equipment such as lithography and exposure machines,environmental micro-vibration isolation is the basis to ensure the high-precision and stable operation of the system.Environmental vibration generally exists in the form of low frequency and small amplitude.In order to effectively isolate the vibration in the environment,the vibration isolation system needs to have lower natural frequency,that is,lower system stiffness.At the same time,for lithography machine,exposure machine and other manufacturing equipment,there is a high acceleration reciprocating motion in the internal moving parts,which will introduce a specific frequency impact disturbance to the system,even if offset by balance mass,active damping and other structures.some energy will still be transferred to the system,affecting the accuracy of the system.Therefore,how to reduce the natural frequency of the vibration isolation system and how to effectively restrain the impact disturbance caused by the internal motion unit of the system has become a hot topic in the field of vibration isolation.In this paper,"Research on active Vibration isolation Technology based on negative stiffness of bistable buckling Beams",on the basis of comprehensive analysis of the development of negative stiffness adjustment technology and active vibration isolation technology,the performance of vibration isolation system was improved from the aspects of negative stiffness adjustment structure,specific frequency impact disturbance suppression.active control method and so on.The bistable buckling beam structure was used as the negative stiffness adjustment unit to effectively reduce the natural frequency of the vibration isolation system,and a compound actuator based on the dynamic vibration absorption principle was designed as the actuator of the vibration isolation system.Its unique anti-resonance frequency characteristics were used to effectively suppress the impact disturbance,and the vibration isolation performance of the system was improved by the expected compensation adaptive robust control method.The above method is verified by simulation and experiments.The main contents of this thesis were as follows:In order to reduce the natural frequency of the vibration isolation system and expand its vibration isolation frequency band,a negative stiffness element structure of double buckling beam and its stiffness adjustment method were proposed.Based on the determined boundary conditions and load conditions of the bistable buckling beam structure,the equilibrium equation of the buckling beam was derived,the analytical solution and characteristic equation of the equation were solved,and the steady state mode and jump mode of the buckling beam were further analyzed.Based on the analytical solution of beam microdecomposition and the law of conservation of energy,the stiffness expression of bistable buckling beam was obtained.On this basis,the influence of axial force and geometric parameters of buckling beam on the stiffness of buckling beam was analyzed,the dynamic model of quasi-zero stiffness isolation system of bistable buckling beam was established,and the transfer function of the system was obtained by energy method.the finite element simulation analysis of the buckling beam was carried out to verify that the double buckling beam element structure had negative stiffness characteristics in a specific position,which provided a theoretical basis for the stiffness adjustment of the follow-up vibration isolation system.Aiming at the problem of shock disturbance suppression at specific frequency,a microvibration isolation method based on the principle of dynamic vibration absorption was proposed.In this method,the composite actuator based on voice coil motor and piezoelectric ceramic stack was used as the active actuator of the vibration isolation system,and the additional stiffness of piezoelectric ceramic was effectively used to form a dynamic vibration absorption structure with the mass of Lorentz motor.its unique anti-resonance frequency was used to restrain the specific frequency band vibration caused by the inertia force in the system.The dynamic model of the vibration isolation unit was established,the influence of the parameters such as load and compound actuator on the anti-resonance frequency were analyzed,and the anti-resonance frequency characteristics of the vibration isolation unit were verified by simulation.it provided a solution to the problem of impact disturbance suppression with specific frequency.In order to make the vibration isolation system adaptive to uncertain parameters and improve the suppression ability of the system to environmental vibration and load direct disturbance,an adaptive robust control method with expected compensation was proposed.On the one hand,this method could well estimate the uncertain parameters of the system,on the other hand,it could improve the ability of the system to suppress the direct load disturbance.The control strategy also introduced expected compensation to reduce the influence of calculation time and measurement noise,it could effectively shorten the stability time of the system.The experimental system was built to verify the negative stiffness adjustment structure of double buckling beam,the vibration isolation method based on dynamic vibration absorption principle and the expected compensation adaptive robust control method were proposed in this paper.A platform for verifying the negative stiffness characteristics of bistable buckling beams was built,and it was verified that the structure had negative stiffness characteristics at a specific position.A compound actuator verification platform was built,and the vibration signals of the environment and load were measured by the speed sensor.In order to make the measurement bandwidth of velocity signal meet the requirements of vibration isolation system,the measurement frequency band of the sensor was extended by zero-pole compensation method.The external vibration was produced by the impact of the type pulse hammer on the base,and the transmission rate curve of the system was obtained.It was verified that the system had the anti-resonance frequency characteristic,and the suppression effect of the system on the frequency vibration signal was verified by applying the specific frequency sinusoidal excitation signal to the platform.The expected compensation adaptive robust control method was verified.Through the comparative experiments with deterministic robust control and adaptive control,it was proved that this method had a good suppression effect on environmental vibration and load direct disturbance,which had the advantages of short stabilization time and high position accuracy.