Compact design of a novel precise cable drive mechanism with high precision and large torque-to-weight ratio

Abstract

Precise cable drive is an elegant transmission mode and has many advantages of high efficiency, flexible layout, besides being lightweight. Since the common layout, Single-Input Single-Output (SISO) spur gear configuration, suffers from low torque-to-weight ratio and loose structure, this paper proposes a novel transmission configuration with large torque-to-weight and compact size. It combines the advantages of Multiple-Input Single-Output (MISO) configuration and bevel gear configuration. The design methods and transmission kinematics of the novel configuration are studied. An analytical model is developed for characterizing the transmission backlash of the proposed configuration, which is derived by simultaneous satisfying system's constitutive relation, equilibrium, and geometric constraints. Parametric sensitivities are carried out to investigate the influence of the major design parameter on the transmission characteristics. At last, a prototype of MISO with bevel gear configuration cable drive mechanism (MBCDM) is built, with which a series of experiments are carried out. This mechanism could achieve maximum output torque of 3.3 Nm with considerable toque-to-weight ratio of 9.649 Nm kg-1. The experimental results show that the transmission backlash and ripple torque are dominant nonlinear effects in the MBCDM system. It shows that the ripple torque is connected with the rotational displacement, with the highest peak at 694.3 cycle rad-1 and the amplitude of 24.67 μrad. The transmission backlash experimental results are in good agreement with simulation ones, with the error level of 4.14%.