Design and Verification of Parallelogram Mechanism With Geared Unit Rolling Joints for Reliable Wiring

The structure of 1-DOF joints used in existing robots is generally a revolute or a prismatic joint. However, recently, attempts have been made to apply rolling joints to reduce the size and weight of surgical and humanoid robots. In this study, to take advantages of wire routing through robot joints, a new method for applying geared rolling units to a parallelogram mechanism is proposed. First, a kinematic analysis of the proposed gear-based mechanism is explained in comparison with the existing pivot-based mechanism. In addition, the importance of the radii of the gears is verified through force analysis to prevent damage to the applied gears, as well as through the analysis of actuation torque and singular positions, in which the parallelogram can convert into an anti-parallelogram. The effect of stable wiring was verified through an experiment using a cable-driven prototype. Consequently, the proposed parallelogram mechanism composed of rolling units is expected to be applied to various robot configurations owing to its advantages.