Overconstrained Coaxial Design of Robotic Legs with Omni-Directional Locomotion

Abstract

Overconstrained linkages are a class of spatial mechanisms with specifically designed geometrical conditions. While extensively researched, their engineering potential is yet to be explored. This paper investigates the design of overconstrained linkages as robotic legs with coaxial actuation, starting with the simplest case, Bennett linkage, to establish the theoretical foundations and engineering advantages towards a class of overconstrained robots. We proposed an alternative form design of spatial link and joint so that overconstrained linkages can be rapidly fabricated and conveniently fixed coaxially on a pair of servo actuators as a reconfigurable leg module. We adopted multi-objective optimization to refine the design parameters by analyzing its manipulability metric and force transmission, enabling omni-directional ground locomotion projected from a three-dimensional surface workspace. We further explored the kinematics and design potentials to generalize the proposed method for all overconstrained 5 R and 6 R linkages, paving the path for a future direction in overconstrained robotics.

Keywords: Kinematic analysis, Overconstrained linkage, Robotic leg, Overconstrained robotics