| With the outstanding advantages of convenient operation and high efficiency,folding arm type Building Maintenance Unit is suitable for the cleaning of buildings with very high parapet.But in the process of folding,pitching and lifting,the anti overturning of the BMU is a difficult problem.As a new type of BMU,the structure is easy to be designed unreasonable for lacking of design experience,resulting in wasting of materials and increasing production costs.Nowadays,the actual engineering requirements for reducing the quality of the BMU and improving the anti overturning performance of the machine are getting higher and higher,so it is necessary to carry out more accurate analysis and optimization of the dynamic and static characteristics of the BMU,aiming at improving the working performance of the BMU.The CWGD250 folding arm luffing BMU was selected as the research object in this thesis.Analyzing and optimizing of the whole and part of the BMU were carried out from the point of statics,dynamics and kinematics.The main contents of this thesis are as follows:(1)The research status of the BMU at home and abroad were summarized,including the types of the BMU,the main research contents about structure statics,dynamics and kinematics of the BMU,and the optimization method of structure.Afterward,the research idea was put forward.(2)A set of research scheme for the BMU was put forward in this thesis,including discussing the functions of each component of the BMU,and putting forward the technical route of the research.According to the requirements for the BMU and crane technology,the BMU working state of load calculation,the BMU working state and anchor anti overturning coefficient S calculation,analysis and calculation of chassis structure and calculation of safety coefficient of fixed pin for rotary disc,one or two boom stress and deflection calculation and three arm hinge point force calculation were studied respectively.Finally,the general requirements for the research of the BMU were put forward.(3)The static analysis method,structure control equation,and model notice of the BMU were put forward,and the whole model of the BMU was established in this thesis.Based on Workbench,the strength and rigidity of the BMU under dangerous conditions were checked,and the life of three stage arms with more variable amplitude were checked.Based on Solidworks and finite element method,the thickness,size and optimization of components were designed to obtain the weight of the optimal jib,slewing disk and chassis,through which realizing the optimization of whole machine weight.The structure of the three stage arm system was optimized to solve the stress concentration problem of the three stage arm system.(4)Transient dynamics analysis theory of the BMU was summarized,and the modal analysis of the whole machine was carried out to obtain the natural frequency of the BMU.The transient dynamic theoretical calculation model of the three stage jib system was established,and the transient dynamics analysis of the local BMU was carried out,including the transient dynamics analysis of the three stage jib system and the transient dynamics analysis of the slewing gear box.Finally,the model was extended to the whole machine in order to further study the impact of transient effect on the whole machine.(5)The problems of the ascending and falling process of the BMU cylinder were put forward,and the advantages of the selection of the luffing mechanism of the hydraulic transmission were analyzed.Based on Adams software,a virtual model of folding arm luffing BMU was established.By comparing the different folding luffing schemes,the optimal folding luffing scheme was selected,and the folding process of the BMU was optimized from the kinematic angle.In this thesis,the optimization of folding arm variable width BMU was done by the finite element and motion simulation technology,and a relatively accurate analysis result was got.This provides a theoretical basis for the design of the BMU. |
