Research On Active Vibration Isolation Method Based On Robust Control Theory

Vibration isolation technology is a common core technology in the field of high-precision manufacturing,processing and measurement.In the field of semiconductor manufacturing represented by lithography machines,ultra-precision processing represented by diamond lathes,ultra-precision measurement represented by super-resolution fluorescence microscopy and gravitational wave detection,it is necessary to provide a stable and reliable environmental protection by the precision vibration isolation system.Active vibration isolation system combines base vibration with direct disturbance to provide wide-band vibration isolation.This paper proposes a vibration isolation experimental unit using a composite actuator,and designs an H_? controller to actively control it.The main research work is as follows.Firstly,based on the analysis of the principle of dynamic vibration absorbing the mechanical structure of the vibration isolation experimental unit is designed.This paper put forward the voice coil motor and piezoelectric actuator series as active actuator,using support spring and piezoelectric ceramic series stiffness,combined with the mass of the voice coil motor and piezoelectric ceramic,realize the dynamic vibration absorbing properties.Secondly,the dynamics modeling of the vibration isolation experimental unit is carried out.The relationship between the output force of the piezoelectric actuator and its control voltage and the output force of the voice coil motor and its control current is analyzed.The dynamic model of the vibration isolation experimental unit is established.The transfer function of the ground vibration displacement of the open-loop system to the load displacement and the load directly disturbing the power to the load displacement is derived.The frequency characteristics of the open loop system are analyzed.Then,the H_? controller was designed and simulated.Based on the open-loop frequency characteristics of the vibration isolation experimental unit,it is necessary to actively control the ground vibration and the load direct disturbance whose frequency is near to the two natural frequencies.H_? control can be used to select the appropriate weighting function for frequency characteristic shaping design and control and the control input can be limited.The designed controller was simulated by Matlab/Simulink to verify the vibration isolation effect.Finally,the establishment of the experimental system is completed.The designed piezoelectric actuator is tested,and the displacement range of the designed piezoelectric actuator is 0-55 ?m.The filter and low frequency compensation network are designed for the velocity sensor.Experiments are carried out on the active control effect and vibration isolation performance of the vibration isolation experimental unit.The experimental results show that: the anti-resonance frequency of the vibration isolation experiment unit is 11.6Hz when there is no control,and the vibration attenuation near the anti-resonance frequency is obvious;with active control,the formant is eliminated and the transmissibility is less than 0dB in the full frequency band;when the maximum speed of base is 7mm/s,the maximum speed of load with and without control is 1.3mm/s and 4mm/s respectively;when the same direct disturbance force is applied to the load,the maximum speed of the load with and without control is 2.66mm/s and 5.36mm/s,respectively.