Experimental Study On Vibration Isolation Characteristics Of Two-dimensional Complex Pendulum

Gravitational waves are an entirely new way of looking at the universe.Instead of some discrete,detectable quantum particle interacting with another to produce a detectable signal in some electronic device,gravitational waves act as ripples in the fabric of space.At present,the laser interferometric gravitational wave detector has become the mainstream of all kinds of gravitational wave detectors for its advantages of wide band and high sensitivity.In order to capture gravitational waves in a wide band(from a few Hertz to a few thousand Hertz),various noise interference needs to be suppressed.Therefore,low frequency vibration isolation technology has become one of the important problems in gravitational wave detection experiments.This paper mainly analyzes and designs a feedback compound pendulum tilting vibration isolation device for gravitational wave detection device.As the gravitational wave detection device is a very precise experimental device,in order to better improve the effect of inclined vibration isolation,the experimental research on the characteristics of two-dimensional complex pendulum tilt vibration isolation,respectively from the design and theoretical analysis of complex pendulum,finite element software simulation and the original mechanical device to add hardware circuit feedback control and other parts of the analysis,research and experiment.The main research content of this paper is divided into the following aspects:Aiming at the problem of vibration isolation in the process of gravitational wave detection,the detailed theoretical analysis and the whole model establishment of complex pendulum are completed.In order to understand the vibration isolation characteristics of complex pendulum in more detail,the whole complex pendulum is divided into three parts for theoretical analysis,and the transfer function of the inclined vibration of complex pendulum is obtained,and the amplitude-frequency characteristic curve of the system can be obtained from the transfer function.In order to test the accuracy and feasibility of the theoretical analysis of complex pendulum,the finite element software simulation experiment is carried out after the theoretical analysis,and on this basis,the overall scheme of the feedback part of the hardware circuit is given.Capacitance detection and piezoelectric ceramic driving part analysis were performed.Based on the displacement sensing device,a capacitor sensing circuit is designed to convert the capacitance change of the displacement sensing device into the variable observed voltage change.Then,the acquisition card is selected and the function of the acquisition card USB3151 is introduced in detail,and the piezoelectric ceramic drive circuit chip is selected.Some problems existing in the application of piezoelectric ceramics are also introduced.On the basis of the above need to introduce PID control module,and the PID control module application Lab VIEW software to write.Finally,the open-loop and closed-loop experiments of the compound pendulum are carried out.After the completion of all the above work,the open-loop experiment and closed-loop experiment of the compound pendulum overall inclined vibration isolation device were compared.Under the PID control,the amplitude attenuated about 20 d B in the Y-axis direction near the frequency 3.17 Hz,the natural frequency decreased,and the resonance peak decreased.In the X-axis direction,the amplitude attenuates about 30 d B near the frequency3.28 Hz,and the natural frequency also decreases,as well as the resonance peak.Through the comparative analysis of the experimental results,it is found that the active vibration isolation with PID control can achieve good tilting vibration isolation effect.