Coupled bending inwards motion and control strategy analysis of a cable-driven underactuated finger

Abstract

Motion strategy analysis at the pre-bending stage is a fundamental component of underactuated finger grasp research. This study presents the pre-bending motion strategy and corresponding analysis of cable driving forces a 3-DOF underactuated finger comprising cable truss units. The structure and four motion strategies at the pre-bending stage are illustrated. The equivalent joint-driven and quasi-static motion models are established in the case where one or two cable driving forces drive the finger. Quasi-static motion model is established, and four typical quasi-static coupled motion space and distributions of corresponding cable driving forces are analysed. In accordance with the kinetic energy theorem and Lagrange's dynamical method, a sampled and general dynamic model is established. Through matrix transformation, a hypothetical 'PPA' type dynamic model is obtained. On the basis of the 'PPA' dynamic model, three grasping control strategies at pre-bending stage are carried out. Valid simulations and experiments are conducted to verify the accuracy of the coupled bend inwards motion and control strategy.