Application Research Of Active And Passive Hybrid Vibration Isolation Technology For Marine Diesel Generator Set

Vibration and noise,especially the low frequency vibration and noise,generated by marine power machinery affect acoustic stealth performance of a war ship and detection ability of its own sonar seriously.Active vibration control is an effective method to reduce the low frequency vibration of marine machine.It is necessary to investigate how to put the active vibration control technique in marine application since the urge nt demands of reducing low frequency vibration.Based on the active two-stage vibration isolation researches of ANVC(Active Noise and Vibration Control)Group in HEU,a sensing-actuating integrated and passive-active hybrid isolator is developed in this thesis for the purpose of practical engineering application.Active actuators,power amplifiers,high and low pass filters,acceleration error sensors and its power supply and conditioning circuits are integrated into a traditional two-stage passive isolation structure.A marine 6135 diesel generator is chosen as a vibration source,a sensing-actuating integrated and passive-active hybrid isolator is developed and some issues concerning practical applications of active vibration control are investigated and discussed.The details of this thesis are as follow:1)A new sensing-actuating integrated and passive-active hybrid isolator is proposed and developed based on a passive two-stage vibration isolation structure.The actuator,power amplifier,low pass and high pass filters,sensor and its power apply,its amplifier and filters are designed as independent module units.Then all these modules are integrated on a passive two-stage vibration isolation structure and a sensing-actuating integrated and passive-active hybrid isolator comes into being.The dynamic model of the hybrid isolator is established firstly.Then the comparison of optimal active control forces with different actuating position and actuating way is made.The intermediate mass of the two-stage isolation structure is designed and analyzed to install all the modules.The actuator,as the most important unit in the hybrid isolator,is paid more attentions.Investigations on structure design,dynamic behavior analysis and test are made for the electromagnetic inertial actuator used in the hybrid isolator.2)Aim at putting active vibration control in practical marine application,an active and passive hybrid control system based on the sensing-actuating integrated and passive-active hybrid isolator is developed for a marine 6135 diesel generator.The generator is installed on a flexible steel plate,which simulates a ship structure,through 4such kind of hybrid isolators.An offline operation DSP system is adopted as the controller.So the active vibration isolation system is simplified only with a vibration source,passive-active hybrid isolators and a controller.Then the active and passive hybrid vibration control test rig is modelled by FEM and modal test is made.The dynamic behaviors of the rig are investigated and made clear by the analysis and forced vibration responses by the diesel generator,to support the following researches.3)A multi-channel coupling feedforward control strategy based on classical filtered-x LMS algorithm is chosen with the shaft rotating signal as reference signal and offline modeling for error paths.The shaft rotating signal is the best choice as a reference signal in active vibration control system for such kind of rotating and reciprocating machines.By investigating the mathematical relationship between the duty cycle number of rotating pulse signal,sampling frequency and maximum frequency range to be controlled,a criterion of setting the duty cycle will be derived to conduct the active vibration control system design for rotating and reciprocating machines in marine application.4)The experimental investigations of active vibration control are conducted for different running speed of the diesel generator to verify the active vibration control system based on the sensing-actuating integrated and passive-active hybrid isolators.The diesel generator is running from 800 r/min to 1500 r/min with an interval of 50 r/min to verify the performances of the whole active and passive hybrid vibration isolation system.The acceleration responses with and without active control on machine sides upon the four hybrid isolator and plate sides which the hybrid isolator located are measured.The results of active vibration control are analyzed systematically,the active vibration mean reductions are 9.3 d B～19.7 d B within 0～200 Hz,the hybrid vibration mean reductions are 40.4 d B～54.3 d B,and the hybrid vibration mean reductions are 46.0 d B～57.9 d B within 0～800 Hz.Then the reasons of no reduction or amplifying for some harmonics with active control are discussed by considering the modal analysis and test results.The effects on the diesel generator vibration responses with active control,and on the flexible foundation vibration responses outside the active controlled frequency range are analyzed at last.