Overconstrained coaxial design of robotic legs with omni-directional locomotion

Abstract

While being extensively researched in literature, overconstrained linkages’ engineering potential is yet to be explored. This study 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 of a class of overconstrained robots. We proposed a parametric design of the spatial links and joints in alternative forms so that one can fabricate these overconstrained limbs via 3D printing and then attach the linkage coaxially to 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. The proposed prototype quadruped was capable of omni-directional locomotion and had a minimal turning radius (0.2 Body Length) using the fewest actuators. We further explored the kinematics and design potentials to generalize the proposed method for all overconstrained 5R and 6R linkages, paving the path for a future direction in overconstrained robotics.