Simulation And Experimental Study On Dynamic Characteristics Of The Coaxial Indexing Mechanism

Aiming at the engineering requirements for the higher indexing rates,a novel indexing mechanism,named by coaxial cam-linkage indexing mechanism(CCIM),is developed.It has the advantages of compact structure,more indexing times compared with the current indexing mechanisms,which has important theoretical and engineering application value.The investigations on the transmission principle,dynamic simulation and experiment of CCIM are carried out in detail in this thesis.The outcomes lay theoretical foundation for the optimization design and performance improvement of the indexing mechanism.The main contents are listed as follows:Firstly,the composition and transmission principle of CCIM are analyzed,and the duty parameters and dimension parameters of CCIM are defined.The pitch curve equations are established,and its influence factors are also analyzed.Explicit formulae of curvature radius,pressure angle and meshing angle are derived.The static model is established and the collision force analysis is implemented between rollers and cams.Secondly,the prototype dimensional parameters and structural parameters are determined on the basis of static analysis,and the strength of relevant component is checked due to the working conditions.The finite element model(FEM)is established.The first-four mode shapes and corresponding frequencies during a period are analyzed by the modal analysis with the consideration of cam-roller contact status,The results indicate that the first-four mode shapes are the output wheel torsional vibration,the output wheel translational vibration and the quadrilateral linkages torsional vibration.Then,the rigid-flexible coupling dynamic model is established in ADAMS by considering the elastic factors,such as shafts and linkages,bearings,the contact between cams and rollers.The influence of the linkage coefficient on the dynamic response is investigated.During the dwell period,the torsional vibration of the output wheel firstly decreases and then increases with the increase of the linkage coefficient.At the same time,the influence of different motion laws on dynamic response of the output wheel is analyzed.The results indicate that CCIM following the modified sinusoidal(MS)motion law has the best dynamic precision.Finally,the dynamic test platform is built with the physical prototype.The single input/multi-output method is adopted to measure the natural frequencies at different positions during a period.The test points are arranged at the tangential position of the output wheel in the response experiment.The angular acceleration of the output wheel is picked up,and spectrum analysis is performed by Fast-Fourier-Transform(FFT).The results indicate that the angular acceleration responses tendency of the output wheel is consistent with theoretical motion law and its spectrum is close to the simulation results.The relative errors between the experiment and finite element analysis(FEA)is less than 10%.The validity of the dynamic model is confirmed by the mentioned results.