Research On Dimensional Synthesis Method Of Multi-bar Mechanism With Single Degree Of Freedom Based On Numerical Atlas Method

Mechanism theory is an important basic discipline in mechanical engineering.Dimensional synthesis has always been the research focus and difficulty of the mechanism theory.Researchers at home and abroad have carried out in-depth analysis on the study of periodic dimensional synthesis of linkage mechanisms.Nonperiodic dimensional synthesis is more common in practical engineering.However,there are few studies on the nonperiodic dimensional synthesis of multi-bar mechanisms.Therefore,based on the dynamic self-adaptive atlas method,the path synthesis of the planar five-bar mechanism and the motion generation of Stephenson III mechanism have been realized in this paper.First,according to the multidimensional search tree,a path synthesis method for a planar five-bar mechanism is proposed.The wavelet transform is used to extract the wavelet characteristic parameters of the output curve of the five-bar linkage.Based on the numerical atlas methods,a multidimensional search tree and an index keyword database are established.Through preprocessing and wavelet transform,the wavelet characteristic parameters of the open path curve are extracted.Furthermore,a dynamic self-adaptive atlas database is established.By comparing the similarity of the wavelet characteristic parameters between the prescribed curve and the basic dimensional types,the target mechanism with an approximately optimal output is found.On this basis,the mathematical model for calculating the actual sizes of the desired mechanism is given.The path synthesis of the open interval of the planar five-bar mechanism is realized.Through the theoretical example,the correctness of the proposed method is proved.By the compared example,the motion simulation test is carried out,which proves that the output curves of the planar five-bar mechanism are more abundant.Secondly,on the basis of realizing the open path synthesis of planar five-bar mechanism under multiple transmission ratios,the motion generation of Stephenson III mechanism is further studied.The mathematical model of the output path curve of Stephenson III mechanism is established.The output characteristics of Stephenson III mechanism are wavelet transformed.Combined multidimensional search tree,the dynamic self-adaptive atlas database of the Stephenson III mechanism is established.The actual sizes of Stephenson III mechanism are calculated.The steps of Stephenson III mechanism motion generation are given in detail.The nonperiodic path synthesis of Stephenson III mechanism is realized.Finally,dimensional synthesis and simulation analysis are carried out on multiple examples.The methods proposed in this paper are proved to be correct and effective in the single-degree-of-freedom multi-bar mechanism dimensional synthesis problem.