Study On Attitude Control Of Floating Raft Vibration-Isolation System With Air Spring

Floating raft equipped with air spring has a good low frequency performance in vibration-isolation, it has been widely used in marine plants. Attitude of floating raft will change if air spring affected by leaks or external disturbances, leading to a misalignment of propulsion shaft and twisting of pipes, floating raft's performance declines, it affects the safe operation of equipment. Therefore, it is necessary to take control strategy to keep the floating raft's attitude. This thesis focuses on floating raft, and proposed a research on control strategy about attitude adjustment.Firstly, the composition and principles of floating raft equipped with heavy-duty air spring was introduced briefly. The functions and overall scheme of control system was proposed, which is based on embedded PC and fieldbus. Design and layout about electrical control system were completed.Secondly, air spring's characteristic was analyzed and floating raft's model was built. Air spring's optimal pressure was calculated from its location and floating raft's weight by constraint of minimum variance. As system can't be exact decoupled, a coupling recognition method was presented based on air spring's characteristic and optimal pressure, the one should be charged or discharged can be exactly picked using this method.Thirdly, an control strategy is proposed based on air spring's height and pressure in order to speeding up the adjustment and reducing raft oscillating in the course of raft's attitude adjustment, which contains two stages: first, output shaft alignment is achieved using fuzzy control; then, using a strategy of ‘high-discharge or low-charge' to adjust the horizon attitude precisely. Then, a simulation was carried out to verify the feasibility of the control strategy.Finally, build physical main propulsion unit platform for a certain type warship, control software and human-machine interface have been compiled and debugged, tests were carried out using different control strategies. Test results indicate that the control strategy proposed in this paper was faster in adjusting, oscillating amplitude during adjustment was smaller and air spring's pressures were closer to the optimal distribution.