Fuzzy Control Optimized By Genetic Algorithm For The Floating Raft Active Vibration Isolation System

The vibrations generated by the operation of power equipment are the main mechanical noise source of naval vessels,which seriously affect the stealth combat capability of naval vessels.The vibration isolation technology is an important means of vibration and noise reduction for naval vessels,which can inhibit the energy transferred to the ship structure.Especially,the floating raft active vibration isolation technology inherits the characteristic of "Mass Effect" passive,"Tuning Effect" and“Mixed Neutralized Effect'' from the passive floating raft and the advantages of good adaptability,good effect at low frequency from the active vibration isolation system,which is got extensive research.Active control strategy is one of the key technologies for floating raft active vibration isolation.The controller designed with effective control strategy can adjust the output of the actuator,so that the active force generated by the actuator can cancel the vibration force generated by the interference source,thereby achieving the purpose of vibration isolation.It's difficult to build mathematical model and to control for the floating raft active vibration isolation system due to its complex structure,strong coupling.The feedback control method can control the variation of the controlled object caused by various disturbances,and effectively restrain the periodic disturbances generated by the marine power equipment.The traditional control methods depend highly on the linear model of the controlled object,so their applications to the floating raft active vibration isolation system are greatly restricted.As an intelligent feedback control method,the fuzzy logic control derived from the operator experience or expert knowledge doesn't need to establish the precise mathematical model of the controlled object,and can provide the intelligent path for the active control of the complex floating raft system.Firstly,in the case of the characteristics of the floating raft active vibration isolation system,the system identification method of least square is adopted to gainthe two-inputs and two-outputs discrete transfer function models of the floating raft system,and the frequency-domain fitness and the zero-pole distribution of the models are tested.The frequency-domain fitness of the models are more than 90% and the poles are located in the unit circle,which means the model can accurately describe the dynamic characteristics of the floating raft active vibration isolation system in the range of 0 ~ 80 Hz.Secondly,the basic theory of the fuzzy logic control for the floating raft active vibration isolation system is introduced,which lays a theoretical foundation for the fuzzy control simulation system and the experimental system of the floating raft active vibration isolation system.Then,the conventional fuzzy logic controller is designed,the control simulations of single-frequency interference,dual-frequency interference and narrowband interference are carried out.Then,the genetic algorithm is introduced in the case of the partial defects of the fuzzy logic controller,while real integer mixed coding method is adopted to optimize the quantization factors,scale factors and control rules of the controller simultaneously.The results show that the fuzzy controller based on the genetic algorithm is superior to the conventional fuzzy controller in vibration suppression.Finally,fuzzy control experiments based on genetic algorithm parameters optimization are conducted on the floating raft vibration isolation platform,including the single-input single-output and two-input two-output control experiments.The experimental results show that the fuzzy controller can effectively suppress disturbance signals generated by one vibration motor and two vibration motors and narrowband disturbance.The amplitudes of the acceleration at the main frequency reduce mostly above 30%.