Research On Transmission Error Modeling And Synchronism Prediction Of Single-Sided Cable-Driven Sheaves

Cable-driven sheaves are a device wrapped by cable in a single-sided pattern, which transmitt motion through the front sheave pulling rear sheave. The connection between their cable and sheaves determines the skid phenomenon occurs difficultly when a large torque is transfered. Thus, they can transmitt higher motion precision. However, since the rotation error of single-sided cable-driven sheaves is not zero in motion, the transmission error is inevitably produced between sheaves, which affects their transmission precision.The lock system of docking mechanism is a closed-loop transmission device composed by serial single-sided cable-driven sheaves. The movement synchronism of lock system is one of the key technology for spacecraft successful docking, which is guaranteed by assembly quality of serial single-sided cable-driven sheaves. For lack of in-depth theoritical research in this aspect, the assembly of docking mechanism faces the technical bottleneck of lower efficiency and poorer quality. For this, based on serial single-sided cable-driven sheaves, both the transmission error modeling and synchronism prediction are carried out.Cable deformation is a main factor influencing on movement synchronism of serial single-sided cable-driven sheaves, which is controlled by its preload adjustment. To predict the cable deformation under the preload, a prediction model for transmission error is built according to the way of preload exerted on cable-driven sheaves, which can be used to describe the cable deformation. Through analysis of the transmission error influenced by dominating factors and of the parameter sensitivities to transmission error control, this lays the foundation for futher research on movement synchronism of serial single-sided cable-driven sheaves.A creep modified model of the cable is built based on the working conditions of single-sided cable-driven sheaves. Cable creep is an unavoidable significant problem in precision transmission study of cable-driven sheaves. For the higher movement synchronism requirements of serial single-sided cable-driven sheaves, the cable creep cumulative effects of the single one can significantly affect their transmission accuracy and even lead to their transmission failure. To predict the cable creep under the preload, considering the working conditions of single-sided cable-driven sheaves, a creep modified model of the cable is built based on the Norton-Bailey creep constitutive model and three factors of the sheave angle, preload and friction coefficient effects are analyzed.A prediction model for transmission error of single-sided cable-driven sheaves is established according to their driving order, which can describe the cable motion deformation. The slip and no-slip cable arcs of sheave angle effects on modeling precision are analyzed. The corresponding angles of above two arcs are determined by experimental transmission error laws and the prediction model for transmission error is modified. Then, a movement synchronism prediction model of serial single-sided cable-driven sheaves is established and its influencing factors are analyzed. Both the change laws of their rope tension and the compensation of their movement synchronism are studied in driving process.Research on synchronous accuracy prediction of serial single-sided cable-driven sheaves is carried out. Since the factors affecting synchronous accuracy of serial single-sided cable-driven sheaves are extremely complicated in assembly, it is difficult to build a precise mathematical model to describe the relationships between the cable tension and deformation(transmission error). For this, based on the cable rigid transmission conditions and the preload exerted way, a symmetric distributing data method is put forward, in which the transmission error of single-sided cable-driven sheaves is converted into its corresponding angle values and distributed symmetrically on sheaves of serial ones to increase data samples. Then a assembly synchronism prediction system of serial single-sided cable-driven sheaves is developed. By this system guiding field assembly of lock system, its assembly efficiency can be improved.