Dynamic Behavior Of Bellow-type Fluid Viscous Damper Under Medium And High Frequency Exciation

The development of space technology demands higher requirements for future spacecraft.As an actuator in the satellite,CMG(control moment gyro)plays a very important role.It outputs moment which can be used to keep stabilization of satellite.Because of mass eccentricity during manufacturing process,when CMG is working,it produces micro vibration which has worse influence on image equipment in the satellite.In order to provide a good mechanical environment,isolating this micro vibration is very important.As a passive isolator,bellow-type fluid viscous damper has been used in micro vibration isolation successfully.At present,the existing models cannot describe the dynamic stiffness and damping under medium and high frequency excitation.Therefore,these models cannot be used to design this bellow-type fluid viscous damper.For this reason,it is necessary to establish an accurate dynamic model to describe the dynamic behavior of this bellow-type isolator under medium and high frequency excitation,also the influence of main design parameters of this bellow-type fluid viscous damper to the isolation performance need to be analyzed.Because the model which based on fluid mechanics theory cannot describe dynamic stiffness and damping of bellow-type fluid viscous damper under medium and high frequency.Based on hydraulic fluid mechanics theory,take a single tube fluid viscous damper as research object,based on small displacement condition,with consideration of silicone oil’s bulk modulus,by using approximate analytical method,dynamic model of fluid viscous damper under medium and high frequency excitation is proposed with and without consideration of entrance effect.Based on this model,dynamic model of bellow-type fluid viscous damper is established.In order to verify the accuracy of model,a fluid-structure interaction model is established.The results show that when silicone oil’s viscosity is low,the model without consideration of entrance effect cannot describe the dynamic behavior accurately,but the model with consideration of entrance effect can overcome this problem.Based on the dynamic model of fluid viscous damper under medium and high frequency excitation,relationship between main design parameters(viscosity,orifice diameter,orifice length)and dynamic stiffness,damping is derived.After that,influence of main design parameters on the dynamic stiffness and damping is analyzed.The results show that the compressed fluid in the damper produces dynamic stiffness.In the high frequency domain,when damping orifice has small diameter,the dynamic stiffness exists stable value which is larger than main stiffness.Besides,the damping reduces very quickly in the high frequency domain.Based on the dynamic model of bellow-type fluid viscous damper under medium and high frequency excitation,relationship between main design parameters(viscosity,orifice diameter,orifice length)and dynamic stiffness,damping is derived.After that,influence of main design parameters on the isolation performance is analyzed.The results show that the resonance peak has been suppressed effectively,but isolation performance in the high frequency is poor because of huge dynamic stiffness.For this reason,an improved design is proposed,in order to improve isolation performance in the high frequency domain,a compensator needs to be added to the bellow-type fluid viscous damper.Finally,bellow-type fluid viscous damper which contain and not contain compensator are manufactured.Isolation performances of these two dampers are tested,the main isolation performance index is resonance peak and attenuation rate.For the isolator which not contains compensator,a comparison is made between the dynamic model and test in order to verify the accuracy of analytical model.A payload is used to test isolation performance of bellow-type fluid viscous damper which contains compensator.The results show that isolation performance of bellow-type fluid viscous damper which not contains is poor in the high frequency,but the isolation performance of the isolator which contains compensator has been obviously improved,the minimum resonance peak is 3.33 and the attenuation rate above 100 Hz is better than-30 d B.In order to improve isolation performance in the high frequency domain,it is necessary to add compensator to the bellow-type fluid viscous damper.