Mathematical modeling for the vertical damping analysis of sonobuoy lumped suspension system

摘要

Sonobuoy is employed in sea with the purpose of detecting unwanted targets. In order to achieve accurate detections of surrounding targets in sea, it is imperative that the sensor should remain stable at that desired position. However, there are various sea forces (sea surface waves, underwater currents etc.) which cause its movement from the equilibrium position creating various unwanted noise and vibration signals. These cause false detections and reduced SNR for the whole system. To reduce this unwanted signal a suspension assembly is provided which comprises of a specialized suspension cable (also called as vibration isolation module) made of rubbers. This acts like a spring to damp the vertical vibrations/movements of the sensor. This paper covers mathematical modelling of Sonobuoy suspension system considering it as two degrees of freedom system with base excitation. Major aim is to prevent vertical oscillations that come from the floating buoy at the sea surface from reaching to the sensor. For this purpose an energy dissipation device between the buoy and sensor is required to damp these oscillations. This purpose can be achieved by employing such a material as suspension wire whose stiffness and damping values agree with the required ones. This study includes a coupled dynamic analysis theory with numerical approach being limited to small elastic elongation. The different values of damping ratio (ζ) between 0.04 to 0.44 were used in steps of 0.1 to control vertical motion of sensor.