| The hemispherical resonator is one of the key components of HRG,whose machining quality directly determines the performance of the hemispherical resonator gyro.The machining quality of hemispherical resonator can only reach submicron level at present in our country.In order to improve the machining quality of hemispherical resonator,it is very necessary to polish the hemispherical resonator after ultra-precision grinding.As the structure of the hemispherical resonator is more complex,the traditional polishing technology can?t be achieved.Therefore,the special machine tool for MRF of the hemispherical resonator is designed based on the theory of magnetorheological finishing(MRF)in this paper.And the research on the properties of the magnetorheological fluid and the process parameters of MRF are completed.The magnetorheological finishing process of hemispherical resonator is designed according to the structure characteristics of hemispherical resonator and the machining quality requirements in this paper.And the magnetorheological polishing of hemispherical resonator is studied by using small diameter permanent magnetic ball head.And the overall scheme of the magnetorheological finishing machine for hemispherical resonator is designed.According to the function,the machine tool is divided into corresponding modules,and the corresponding structural design of the module is carried out.Finally,the design and construction of the machine tool are finished.The removal properties of magnetorheological fluid in the process of hemispherical resonator polishing are studied.By analyzing the performance requirements of the magnetorheological fluid,the components of the magnetorheological fluid are selected as follows: carbonyl iron powder,cerium oxide and hydroxypropyl methyl cellulose.And the effect of the components of magnetorheological fluid on the removal rate of the material is studied by single factor experiment.The influence of different composition combinations on the removal rate of the materials are studied through the orthogonal experimental design.The influence degree of the different content of components in the magnetorheological fluid on the removal rate of the fused silica glass is analyzed.Finally,and the magnetic flux with the highest material removal rate is obtained which is the carbonyl iron 36%,cerium oxide 3%,additives 1.1%,water 59.9%.Based on the analysis of the processing form of the hemispherical harmonic oscillator,the removal function of the hemispherical harmonic oscillator is deduced according to the Preston equation.In order to acquire the optimal polishing process parameters,the magnetorheological finishing experiments of the melting quartz glass is conducted through the response surface method.And the mathematical model of the melting quartz glass removal rate of the polishing process parameters(polishing head spindle speed,workpiece spindle speed,C axis rotation,polishing gap)is made according to the experimental results.The influence of the polishing parameters on the material removal rate are analyzed.Besides,the parameters of the polishing process are optimized by the particle swarm optimization.According to the optimization results,the polishing test is carried out,and the error between the actual value and the theoretical value is 5.6%.Finally the experiment of HRG ultra precision is conducted with the optimized polishing parameters and the experimental results show that the surface roughness Ra of the hemispherical resonator is improved from 78.3nm to 14.3nm and the surface accuracy PV is increased from 0.5457μm to 0.3320μm. |
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