Research On Accuracy Characteristics Of RV Reducer For Robot

RV reducer has a highly compact and rigid structure that is robust against shock-load and overloading,d ue to such mechanisms incorporate numerous cycloid-pin teeth that are engaged concurrently.Furthermore,a minimal backlash and inertia assure a rapid acceleration and extremely accurate positioning.RV reducers are widely used in precision transmission applications such as industrial robots,machine tools and medical equipment.Accurate calculation of meshing force of cycloid-pin in RV reducer is particularly important for its accuracy characteristics analysis.In this dissertation,a new theoretical analysis model of RV reducer is proposed to impro ve the reliability and accuracy of the results.To verify the theoretical model,the finite element simulation model was established to obtain the variation rule of mechanical characteristics and fatigue life of RV reducer.To study the influencing factors and changing rules of accuracy characteristics of RV reducer,the transmission performance test and fatigue life experiment of RV reducer prototypes were carried out respectively.The test results provide an important reference for studying the accuracy attenuation process of RV reducer and improving its service life.The main research contents of this dissertation are as follows:(1)The meshing area of cycloid-pin was discretized into multiple differential elements using Gaussian quadrature,and the transmission accuracy model of RV reducer was established based on Lankarani-N ikravesh contact force model and Ambrósio friction model.Compared with the traditional contact force model of cycloid drive,the calculated results are more accurate and reliable,a nd the proposed model is verified by finite element method.Based on this new model,the influence of cycloid tooth profile modification(TPM)and load on the transmission performance of RV reducer is studied in detail.Compared with combined modification methods,the proposed inverse tooth profile can keep good transmission performance as the load and the modification coefficients increasing.By substituting crank eccentricity error into the theoretical model,the relationship between crank eccentricity error and transmission error of RV reducer can be obtained.Based on the mechanics equations of RV reducer,the bearing force can be calculated.The torsional stiffness model and fatigue life model of bearing system are established by theoretical method.(2)Based on the finite element simulation analysis,the dynamics model,thermodynamic model and fatigue life analysis model of RV reducer were established.The dynamic characteristics,thermodynamic characteristics and fatigue life of RV reducer were studied.The stress distribution and its change process are obtained by dynamic analysis.On this basis,the stress results are brought into the fatigue life model to analyze the fatigue life performance of RV reducer.Through thermodynamic analysis,the temperature distribution and heat flux distribution of the nodes on the surface of cycloid-pin were obtained during the meshing process.The results show that the highest temperature of contact area is mainly around the inflection point of the cycloid tooth profile.Therefore,when the temperature is high,this area is most likely to be scuffed.Through the fatigue life simulation analysis,the most vulnerable parts and damage areas of RV reducer are obtained.The influence of load on the fatigue life of RV reducer is also studied.The results show that the fatigue life of RV reducer decreases rapidly with the increase of stress level in the lower stress range,while the increase of stress level has little effect on the fatigue life of RV reducer when it is subjected to a large load.(3)On the high-precision RV reducer transmission performance tester developed by our research team,four RV reducer prototypes running under different working conditions were tested,and the main components of RV reducer transmission e rror(TE)were studied.The tooth precision and surface roughness of the input gears were tested.An integrated device for RV reducer transmission test and fatigue life experiment is developed.O n this basis,the fatigue life experiment of RV reducer prototype is carried out.The change process of TEs and hysteresis curves is studied.The weakness of fatigue life of RV reducer was determined,which further verified the correctness of theoretical calculation and simulation results.The radial loading device for the fatigue life test of RV reducer is designed,and the method of eliminating eccentricity error in the transmission error test of reducer is proposed.By comparing the testing methods of hysteresis curve in the production enterprises,research institutions and national standards,the testing method of hysteresis curve of RV reducer prototype is determined.