Design Of A Novel Pneumatic Vibration Isolator Parallel With Magnetic Negative Stiffness

With the development of modern precision manufacturing and metrology equipments,the demand for a higher machining and measuring accuracy is becoming more and moreurgent. How to violate the external vibrations has become a major factor concerning thefulfillment of the equipments’ formal functions. This thesis, based on the National KeyScientific Research Project, develops a novel precision pneumatic vibration isolator withcompact structure, small volume, large violation bandwidth and load bearing capacity.The developed novel isolator can be applied in the precision vibration isolation systemsand meet the practical demands of modern engineering.Firstly, this thesis adopts the method of combing the positive stiffness parallel withthe negative stiffness to expand the isolation bandwidth of the pneumatic vibrationisolator and guarantee its stability simultaneously. This can solve the contradictionbetween the system stability and the violation of lower-frequency vibrations. Then themain principle and advantages of using this method are analyzed. Based on the analyticalmodels of the magnetic force and stiffness, characteristics of the negative stiffness areanalyzed under different magnet configurations.Secondly, overall design of the novel isolator is conducted, and the specific methodof combining the pneumatic spring with the magnetic negative stiffness structure isstudied. Then a diaphragm pneumatic spring is designed based on its analytical modeling.According to the structure of the pneumatic spring, a couple of ridaly magnetizedmagnetic rings is designed in detail to provide the needed negative stiffness. Thedesigned magnetic structure can be fixed in the chamber of the pneumatic spring andautomatically guide the inner magnetic ring along the axial direction.Finally, transmissibility tests on the novel designed isolator with/without thedeveloped magnetic rings are conducted under the same payload of55.4kg. Theexperimental results show that the natural frequency of the pneumatic vibration isolator isdeduced from3.61Hz to2.34Hz, which therefore certifies the advantages of the noveldesigned isolator and the effectiveness of the design magnetic negative stiffness structure.