Study On Torsional Stiffness And Dynamic Problems In Harmonic Reducer With Dual Rigid Gear

Harmonic reducer with dual rigid gears is a basic mechanical component of high precision transmission.In the dissertation,the theoretical and experimental research are carried out from the perspective of dynamics around the problem of torsional stiffness,which can provide a theoretical basis for the design,manufacture and quality assurance of high performance harmonic reducer.The main contents of the dissertation are summarized as follows:Based on the theoretical modeling and torsional stiffness test,through the investigation of correlation analysis between torsional stiffness hysteresis characteristics and contact pair assembly accuracy,the influence of some factors,such as radial clearance of bearing,the bearing outer ring fitted with flexspline,the meshing backlash of gear,the friction action,the contact elastic deformation and the gear manufacturing error,on the backlash and stiffness in the harmonic reducer with dual rigid gear have been determined.The research results provide the technical basis for optimizing the tolerance design of the transmission parts of the harmonic reducer with dual rigid gears.Based on the meshing analysis of gears with manufacturing error and the experimental data of torsional stiffness,the dual periodic time-varying law of torsional stiffness of harmonic reducer with dual rigid gears has been given,and a model of dual parameter torsional vibration has been established.The Lindsedt method is used to analyze the vibration unstable boundary,and the simulation method is used to observe the change of vibration unstable response intensity caused by the coupling of dual periodic parameters.It is pointed out that the dual periodic time-varying torsional stiffness is quite harmful to the smooth transmission of the harmonic reducer.The trigonometric series approximation of parametric torsional vibration response with dual periods is given by using the modulation feedback method.According to the transmission chain form,the vibration characteristic frequency of harmonic reducer with dual rigid gears has been determined.Based on the analysis of twinning spectrum,high order twinning spectrum and combination spectrum,the dominant vibration sources of the reducer can be identified and the defects from machining and assembly can be successfully diagnosed.By improving the assembly process or replacing the machining defective components,the vibration resonance peak can be restrained,and the overall torsional vibration level of harmonic reducer with dual rigid gears can be greatly reduced.The nonlinear dynamic behavior of torsional vibration with dual parameters has been studied.The phenomenon of bi-stable limit cycle and chaos caused by the coupling action of time-varying stiffness and cubic non-linearity has been discovered.Meanwhile,the mechanism of chaos is analyzed.In the experimental data,it is further verified that the vibration limit cycle and chaos phenomenon exist in some dual rigid gears harmonic reducers with poor manufacturing quality.The critical curve of vibration limit cycle has been drawn by numerical simulation.It is of engineering significance to quality assurance in the manufacturing process of the harmonic reducer with dual rigid gears.The problems of buckling strength of harmonic reducer with different structures have been studied by modeling and FEA.The torsion test bench is set up to carry out torsion test on the harmonic reducer,and the corresponding critical load and failure process are observed,which provides theoretical basis for determining the rated load of harmonic reducer.