Study On Active Vibration Isolation System Based On Hydraulic Servo Actuator

The vibration of automobiles,helicopters,ships and other mechanical systems seriously affects the safety,reliability and comfort,which is an urgent problem to be solved.The traditional passive vibration isolation method does not require external energy input and has the advantages of simple structure.However,it generally has a small static stiffness,which is easy to produce large static displacement,especially for low-frequency vibration problems.In contrast,active vibration isolation method has the has a stronger adaptability and higher control accuracy,etc.,and it can better isolate low frequency and broadband vibration,which has become a hot research topic in the field of vibration control.In this thesis,to make full use of the characteristics of active and passive vibration isolation method,a active-passive hydraulic actuator was designed.Considering the problem of large displacement in passive vibration isolation method,a double-closed-loop of force transmission rate& displacement was proposed to control the relative displacement while reducing vibration level.Also,after the analysis of designed actuators,a controller for two-degree-of-freedom vibration system was designed and verified by experiments.Firstly,the thesis introduced the design ideas of active-passive hydraulic actuators.And the basic parameters of designed actuators were determined and the principle prototype and hydraulic power system were designed according to actual needs.Also,dynamic models of the open-loop and closed-loop of the vibration isolation system were established,and the system force transmission rate with different feedback parameters were calculated and analyzed.Then,the thesis established a double-closed-loop control system with force transmission rate &displacement and a robust controller based on H∞,and simulation analysis was also performed in Simulink.The results showed that the designed controller can effectively reduce the force transmission rate to achieve control goals.Finally,an experimental table for active vibration isolation system is established and experiments were carried out.The results show that the designed active vibration system can effectively reduce the force transmission rate.In the studied frequency range,the system can isolate about 60%-70% of vibration,and the relative displacement of the upper and lower layers was well controlled within the range of 0.2mm.While achieving the expected vibration isolation goals,the relative displacement remains unchanged and the effectiveness of the active vibration isolation system was verified.