Design And Research Of EFPI Ground Acoustic Signal Sensor

At present,in the dynamic test of the landing point of missiles,artillery shells and other weapons,the vibration signal excited at the time of explosion is mainly detected.However,due to the fast attenuation and environmental interference in the transmission process of the vibration signal,the detection range and range are greatly limited.Moreover,the strong electromagnetic interference environment in the battlefield results in the limitation or even failure of communication facilities such as radar and satellites that work with electromagnetic signals.Ground acoustic signals can be used to solve the above problems effectively.Ground acoustic signals can be used for remote detection and anti-electromagnetic interference advantages,in signal sensing and local communication can play an irreplaceable role.Ground sound refers to the infrasound signal transmitted through the ground as the channel,which is generally composed of the remaining frequency and amplitude of the vibration signal after long-distance transmission and energy attenuation.Compared with the signal component transmitted in the air,the transmission rate is faster,the signal attenuation is slower,and the response time of detection is shorter.However,the ground acoustic signal is susceptible to the influence of geological structure changes and human activities,and its anti-noise ability is weak.Therefore,the high precision,high sensitivity and high stability of the ground acoustic sensor is an important support of the ground acoustic sensor system.In this paper,a pressure balanced geo-acoustic sensor based on Fabry-Perot interference cavity is designed.It has the advantages of high sensitivity,strong anti-interference,high temperature and corrosion resistance,and small transmission signal loss.In this paper,the following aspects are completed: the structure and working principle of EFPI geo-acoustic sensor are mainly studied,the sound pressure response characteristics and frequency response characteristics of the energy exchange film are analyzed,which provides a theoretical basis for the design of the sensor diaphragm;Then the structure of the pressure balance type ground acoustic sensor head is proposed.The influence of the thermo-pressure balance in the interference cavity on the detection results is preliminarily solved by the design of the ventilation groove.The ground acoustic sensor is encapsulated by the ultraviolet adhesive film as the energy exchange diaphragm,and the ground acoustic sensor system is built.Secondly,the linear working region of the geo-acoustic sensor and its demodulation mechanism are analyzed.Aiming at the problem that the cavity length of the sensor is difficult to be precisely controlled,a dual-wavelength single-channel orthogonal demodulation algorithm is proposed,and its feasibility is verified by simulation analysis.Finally,the acoustic response characteristics of the sensor are tested experimentally.The results show that the EFPI geo-acoustic sensor designed in this paper has good frequency response characteristics and stability in the frequency range below 20 Hz,and the sensitivity of sound pressure is up to 100 mV/Pa.