Study On Some Problems Of Floating Raft Based On Air-Magnet Active-Passive Hybrid Vibration Isolation

Submarines in the construction of national defense have a very important strategic position.The mute stealth capability is essential to improve operational performance.Mechanical noise,especially the low-frequency vibration generated by the operation of power equipment,has a great influence on submarine underwater acoustic stealth performance under certain circumstances.Vibration isolation technology can effectively reduce the transmission of vibration energy.It is the key to vibration and noise reduction of marine power machinery.Because of its better impact resistance and system stability,better vibration isolation effect,floating raft vibration isolation system is currently widely used in submarines of the main and auxiliary power equipment vibration isolation.However,there are some restriction factors to improve the vibration isolation performance of the conventional floating raft.First,the structure of the raft frame mostly adopts the frame structure composed of the slab beam.The form of the raft frame is relatively simple,which lacks the new structure form of the vibration energy absorption and dissipation.Secondly,most of the frames are made of high-stiffness and high-intensity metal materials,resulting in a great additional quality of the vibration isolation structure and unsatisfactory effect of medium and low frequency vibration and noise transmission generated by the power equipment.Thirdly,the conventional floating raft is used as a special double-layer passive vibration isolation system,the vibration isolation frequency by its own natural frequency limit,can not achieve more broadband vibration isolation,but also resonance occurs at the natural frequency.In view of the above restraining factors of conventional raft vibration isolation performance,it is necessary to explore a new type of raft frame structure,it is necessary to seek better vibration absorbing material to replace the metal raft frame material,it is more necessary to introduce active vibration isolation to achieve full frequency vibration suppression of the field.To this end,this paper combined the active unit electromagnetic actuator with good dynamic performance and the passive spring unit air-spring with strong bearing capacity to form the air-magnet active-passive hybrid vibration isolation system and to realize the active vibration control.This paper also researched on the raft frame from the truss-type structure and the application of carbon fiber reinforced plastic(CFRP)instead of metal materials.The main research results are:(1)An air-magnet active-passive hybrid vibration isolation experiment platform was established,and a mechanical model of active-passive air-magnet hybrid vibration isolation was established.The structural design method based on the matching of the active and passive vibration isolation units based on the air-magnet active-passive hybrid vibration isolation was proposed.(2)Based on the system identification,a mathematical model of air-magnet active-passive hybrid vibration isolation was established and H? robust control algorithm for active-passive hybrid vibration isolation was developed.On the experimental platform of air-magnet active-passive hybrid vibration isolation,the effectiveness of this method in active vibration isolation under single-frequency interference,dual-frequency interference and narrow-band interference conditions was investigated.(3)The design method of the raft frame based on the truss form was put forward,and the truss floating raft system was constructed.Through the vibration transmission characteristics of the raft frame under different working conditions,the vibration isolation mechanism of the truss structure was revealed.(4)A CFRP raft frame experimental platform was constructed and compared with the vibration isolation performance of the steel raft frame of the same structure and dimensions,which shows that the CFRP is a suitable material for raft frame.The CFRP raft can reduce the additional mass of floating raft vibration isolation system and provides a reference for the future design of multi-material rafts.This paper expects to improve the vibration isolation and noise reduction performance of the floating raft vibration isolation system and improve the mute capability of the ship through the above related research.