Method For Assembly Variation Control Of Aircraft Compliant Parts Based On Locating Compensation Of Fixture

Aircraft as extremely complex mechanical products,its aerodynamic shape and structure strength need to be strict design argued.The requirements of manufacture and assembly accuracy are extremely strict.Aircraft structure contains a large number of weak rigid flexible parts.Due to the existence of parts manufacturing error,fixture locating error,etc,it’s inevitable to cause assembly deformation and deviation in compliant parts assembly process.In the area of compliant parts assembling deviation analysis,the existing research methods mainly focus on reducing manufacturing and fixture locating variation to improve assembly quality.However,little consideration of active fixture locating adjustment has been included to control assembly deviation.With the support of National Natural Science Foundation of China(51275236),the conception of active fixture locating compensation is introduced in this thesis.The optimization method of assembly deviation is proposed based on normal locating compensation of fixture.And the main research contents are as follows:Establishing dimensional variation model of aircraft compliant assembly based on normal locating compensation of fixture.A dimensional variation model which incorporating the clamping force change in assembly is proposed based on the method of influence coefficients and the theory of super-element stiffness matrix.Then,the fixture locating compensation is introduced to set up the compliant parts assembly deviation model based on the hypothesis of linear elasticity and small deformation,which is the theoretical basis for subsequent fixture locating compensation optimization.Fixture locating compensation optimization algorithm is analyzed.The objective function is minimum assembly deviation or locating compensation of fixture.Optimization variables are locating compensation of fixtures while constrains are the adjustment range of fixture in normal direction.The fixture locating compensation optimization model is developed.Next,on the basis of the relationship between the amount of over-constrained locating points and key measurement points,the solving methods of fixture locating compensation are discussed.Then,MATLAB optimization toolbox is used when constraints of fixture compensation range is considered.To verify the correctness and accuracy of the fixture locating compensation method,a case of sheet metal assembly are conducted by finite element analysis and experiment,respectively.And the assembly deviation is compared with and without proposed active fixture locating compensation to verify the validity and accuracy of the fixture locating compensation optimization algorithm.The case of assembly deviation of aircraft fuselage panel is analyzed.Fuselage panel is a typical aluminum sheet structure,which is assembled with multiple complicated flexibly sheet metal parts,such as skin,stringer,and clip.Combination of a certain aircraft fuselage panel,the structure and assembly process are introduced in detail.According to the proposal of fixture board with adjustable locating blocks,a simplified aircraft fuselage panel model is developed.Fixture locating compensation is realized by adjusting the normal position of locating blocks.The normal assembly deviation of skin is analyzed to verify the effectiveness of fixture locating compensation for aircraft panel.These studies provide a new research direction and theoretical basis for aircraft fuselage panel.