| This project comes from the research of "Research on Innovative Design and Compliance Control Method of Bidirectional Actuated Joint for Cooperative Robot",a subproject of National Natural Science Foundation of China(No.92048201).As energy conservation has become one of the themes of the era development,it makes improving the efficiency of energy conversion equipment become a research hotspot in recent years.Therefore,the robot drive system is developing in the direction of high speed and efficiency.The gear transmission is widely used in transmission systems due to its compact structure and large speed ratio,however,some features,such as the large vibration and noise characteristics during high-speed transmission,limit its application scope in the field of high-speed transmission.At the same time,traction drive has a better transmission performance in high-speed transmission for its transmission characteristics.In addition,during the transmission,the vibration and noise are small for the reason of lubricating oil film.Thus,traction drive has a greater research value and application prospect in the field of robot drive system.Based on the principle of traction drive,the adaptive loading ball traction reducer is designed and studied from the theoretical level in this paper,which provides a theoretical basis for the later design and research in the field of traction drive.This thesis focuses on the following topics:This thesis focuses on the following topics:(1)Based on the principle of traction drive,a new type of planetary closed differential adaptive loading ball traction reducer is designed,and its theoretical speed ratio model is established according to its structural characteristics and geometric relations.In addition,considering the traction drive characteristics(big stress and sliding),the elastic deformation coordination equations of the adaptive loading ball traction drive have been deduced based on the theory of elastic deformation at first.Meanwhile,the performance of spin in the contact area is analyzed,and the actual equivalent transmission radius equation is also deduced with elastic deformation and spin considered.Then,the graphic method is adopted to analyze the power flow direction of the adaptive loading ball traction drive reducer,and the actual speed ratio model considering the influence of elastic deformation and spin is established.At last,the overall efficiency model under different power flow direction is also deduced based on the power flow direction of traction drive reducer and the actual speed ratio model.(2)Combining the mathematical models of the actual speed ratio as well as the overall transmission efficiency and the bearing design experience,the geometric dimensions of the traction drive are obtained by the random solution method with the speed ratio and transmission efficiency as the targets.Then,the three-dimensional virtual prototype model of the ball traction reducer is also established based on the geometric dimensions.(3)Two disks were used to simulate the point contact situation,and the lubrication state in the contact area was estimated according to the empirical formula of Hamrock-Dowson point contact elastohydrodynamic lubrication minimum oil film and the film thickness ratio.In addition,the characteristics of traction drive are also analyzed based on the elastoplastic deformation theory.The results show that the traction oil film exhibits the characteristics of Newtonian fluid at the stage of low slip ratio,and non-Newtonian fluid characteristics at high slip ratio.On the one hand,the slope of the linear segment of the traction coefficient curve decreases with the increase of the loading force between the specimens.On the other hand,the slope of the linear segment decreases with spin,which increases the loss in the contact area and reduces the traction transmission efficiency.(4)Combined with the elastic deformation coordination equation,the models of actual speed ratio and the overall efficiency,the transmission characteristics of the adaptive loading ball traction drive reducer under steady state are studied.The relations between the output torque and some actions such as the elastic approach of components,axial displacement,carrying capacity,global sliding(the error of speed ratio)and the overall efficiency,are analyzed in the process.The results show that the maximum capacity of the adaptive loading ball traction reducer is about 45 Nm.In addition,the maximum overall efficiency can reach 91% and the total slip rate is up to 1.8% within the capacity. |
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