Analysis And Control For Assembly Deviation Of Hydrogen And Oxygen Pumps Of Rocket Engine

The assembly quality and precision of rocket engine directly affect the service performance of rocket as the engine is the key part of rocket.When the hydrogen and oxygen pumps of the engine are assembled,the end face is assembled to the rocket body and shall meet the requirements of height and deflection.The flanges’ position and orientation involve the assembly of a large number of pipelines.So higher accuracy of assembly is required.In practice,due to the lack of optimal design of tolerance and assembly process,the assembly deviation is unknown and fluctuates in a large range.It mainly relies on tooling and workers’ experience to adjust repeatedly to meet the assembly requirements,resulting in low assembly accuracy and efficiency.Moreover,multi-source and stack up tolerance and bilateral multi-point connection exist in assembly.The traditional dimension chain model is not applicable to accurately describe the relationship of deviations,and thus can not obtain effective analysis and control of deviations.Therefore,it is necessary to establish an accurate multi-point connection assembly deviation model of the hydrogen and oxygen pumps of rocket engine,to analyze the distribution of assembly deviation and optimize tolerance allocation,so as to guide the actual production assembly process and improve the assembly accuracy and efficiency.In this paper,an assembly deviation model of the hydrogen and oxygen pumps is proposed based on the improved Jacobian-Torsor method considering the multi-point connection characteristics,to reveal the relationship between the deviation sources and the assembly deviation.Based on the Monte Carlo method,the distribution of assembly deviation under random deviations is studied.And the algorithm of deviation sources’ contributions is presented.Based on the deviation model,the optimal tolerance allocation model is established and solved by genetic algorithm.And the influence of different index on tolerance allocation results is studied.Finally,a software system for the analysis and control of 3D assembly deviation is designed.The main research contents are as follows:(1)Assembly deviation model of multi point connection of hydrogen and oxygen pumps based on Jacobian-Torsor modelSmall displacement torsor is applied to define and characterize deviations and stack up tolerance according to the assembly connection relationships of hydrogen and oxygen pumps of rocket engine.Combined with the flexible deformation of the structure calculated by finite element method,the variation range and constraint equation of deviation torsor are obtained.According to the actual position of assembly parts and assembly sequences,multi-point connection assembly constraint is introduced and the Jacobian-Torsor model is improved to establish the assembly deviation model of hydrogen and oxygen pumps.It provides the basis for deviation analysis and control.(2)Assembly deviation analysis of hydrogen and oxygen pumps under random deviationMonte Carlo simulation is conducted to fit the actual distribution of deviation sources.Based on the assembly deviation model,the assembly deviation of the target characteristics of two types of hydrogen and oxygen pumps is calculated to reveal the quantitative relationship between the deviation sources and the assembly deviation under random deviation.The distribution characteristics of deviation of the upper face and flanges are analyzed,which provides references for standardized manufacturing of pipelines.The algorithm of deviation sources’ contributions under Monte Carlo method is developed,and the key deviation sources are determined to provide reference for tolerance design.(3)Optimal tolerance allocation and deviation compensation of hydrogen and oxygen pumpsAn optimal tolerance allocation model is established for hydrogen and oxygen pumps.And the model is solved by improved genetic algorithm.The influence of the fluctuation of precision index on the tolerance allocation results is explored.The optimal tolerance allocation scheme is selected to improve the assembly accuracy and efficiency as well as to reduce the production cost.A deviation compensation model is established for assembly process.The optimal adjustments at the joints are calculated according to the actual position and orientation of pipeline flanges to guide the assembly process.Based on the above model,a software for assembly deviation analysis and control is developed to achieve the process optimization in site product.To sum up,this paper establishes the assembly deviation model and optimal tolerance allocation model for hydrogen and oxygen pumps of rocket engine.Analysis and optimization control of deviation for the two types of engines are carried out.It provides conditions for consistent control and automatic assembly.