The Dynamic Characteristics Research And Structure Optimization Of The Building Maintenance Unit Jib

Building Maintenance Unit(BMU),as a new type of mechanical and electrical integration of high altitude construction equipment,is full of high and new technology content.The frequent opening and stopping of the BMU has a strong impact on the structure of the jib with the increase of working range and load weight.As the main support part of the BMU,the jib has direct effects on the performance of the whole machine and the operation of the BMU.The dynamic characteristic of jib is the key to the design of BMU.Jib of the CWGS250 type roof rail type BMU is studied in this thesis.Mechanical analysis,vibration characteristic analysis,dynamic load analysis,transient dynamic response analysis and equal strength optimization are carried out for the jib structure,and the stability and vibration characteristics of the optimized jib structure are verified.This provides a certain theoretical basis for the development and use of BMU products.Firstly,according to the standards of BMU and its related standards,the load of BMU under different working conditions was analyzed,and the strength and stiffness of the jib are calculated,and the maximum stress and deflection of each section are obtained.Then the vibration characteristics of the jib were investigated by the flexibility method,Euler-Bernoulli beam theory and ANSYS mode respectively,the first four order natural frequencies and corresponding modes of vibration are obtained by the above three methods,and the advantages and disadvantages of the three methods are compared and analyzed.Secondly,the dynamic models of three kinds of working conditions of jib were established based on the safety operation rules of BMU.The damping coefficient of the wire rope was introduced to solve equations and obtain dynamic load on steel wire rope.After the natural frequency of the end of jib is obtained,ANSYS software was used to analyze the transient characteristics of the telescopic boom under the second and third working conditions,and the time history curves of the maximum displacement and maximum stress of the telescopic boom under different working conditions were obtained.Finally,the geometric dimension of the structure section of jib was chosen as design variables,allowable force and allowable deflection of jib as state variables,the maximum stress difference of each section jib as objective function,the structure size of jib was optimized.After optimizing the size of the jib,the stability and vibration characteristics of the jib are verified.In this thesis,BMU jib dynamic characteristic under different working conditions were analyzed based on the existing models,and structure optimization was conducted,which achieve the full use of capacity of the jib section.Such work provides a reference for similar BMU product design and optimization in the future.