Dynamic Modeling And Dynamic Simulation Method Of Flexible Telescopic Boom Mechanism Of Aerial Work Vehicle

Aerial working equipment(including vehicle mounted working platform,mobile lifting working platform and fixed lifting working platform,etc.)is a kind of special engineering machinery that lifts operators,tools,materials,etc.to the designated position in the air through the working platform to carry out various installation,maintenance and repair operations.Due to the manned high altitude operation,the platform should have high stability and absolute security.Therefore,it is necessary to carry out further research on dynamic modeling,simulation and calculation methods,in order to obtain accurate dynamic simulation results of the aerial working platform boom system,and the foundation for the mechanism optimization and trajectory planning which will further improve the performance indicators of the working mechanism,in particular,suppress the adverse effects and injuries of vibration on high-altitude operators can be lied.In this dissertation,from the view of flexible multi-body dynamics,the modeling and solution methods of the three section telescopic booms mechanism of GTZZ21 aerial working platform were carried out by applying the method of Absolute Node Coordinate Formula(ANCF).The three booms of the telescopic boom system were considered as multinode beams with shear deformations independently,and the boundary conditions of the telescopic boom system under different working conditions were established.The static equilibrium equations and dynamic equations of the typical motions such as lifting,extending and retracting,rotating and their composite motions of the telescopic booms mechanism had been solved,and the displacement,velocity and acceleration curves of each boom head node changing with time were given.The contents of this dissertation mainly include the following aspects.(1)According to the actual structure of the research object,a boundary condition considering the tail offset of the beam was proposed.The results such as interpolation matrices,mass matrices and stiffness matrices of two node beams in ANCF method were extended to multinode beams.Aiming at the problem that there were many generalized coordinates in ANCF method,which made it difficult to solve the static equilibrium equations and dynamic equations of the beam,based on the assumption of small deformation and the master-slave degrees of freedom method,the split iteration method was proposed to solve the static equilibrium equations and dynamic equations of the beam under the boundary conditions of the overhanging beam and the boundary conditions including the tail offset.The results showed that the method was effective.(2)The static equilibrium equations for the telescopic mechanism under the fully extended state were established.The boundary conditions were determined based on the telescopic mechanism actual structure,and the method of selecting master degrees of freedom and slave degrees of freedom for solving the static equilibrium equations was proposed.The split iteration method described above was improved and generalized.Compared with the initial version,the improved split iteration method could be used to solve the respective Euler angles of each telescopic boom in the static equilibrium equations of the telescopic mechanism,and the accuracy and efficiency of the solution were improved.(3)The improved split iteration method and generalized α method were combined to solve the dynamic equation of pitching motion of the telescopic mechanism.The calculation results were compared with the experimental results.The comparison results showed that the results obtained by the method proposed in this paper were in good agreement with the experimental results.(4)Telescopic motion with load was a typical working condition of aerial work platforms.In the telescopic motion,the interpolation intervals of the head node and the tail node of each telescopic boom changed with time,and the boundary conditions also changed with time.In this dissertation,the dynamic boundary conditions and dynamic equations of each boom in the telescopic process were established.The methods of selecting the master degrees of freedom and slave degrees of freedom under the telescopic motion boundary condition were proposed to solve the dynamic equations of the telescopic motion.Therefore,the problems of variable structure vibration analysis under the small deformation condition were solved.(5)The boundary conditions of the telescopic boom mechanism were extended from two-dimensional conditions to three-dimensional conditions,the methods of selecting the master degrees of freedom and slave degrees of freedom under the boundary conditions of the rotary motion were given and the dynamic equations of the telescopic boom mechanism rotary motion were established and solved.(6)The boundary conditions and dynamic equations of the composite motion of the three basic motion of the aerial working platform flexible telescopic boom mechanism were established.Based on the small deformation hypothesis and the ANCF method,the improved split iterative method was utilized to solve the dynamic equations and the corresponding results were analyzed.