Automatic Synthesis of 1-DOF Transformable Wheel Mechanisms

The transformable wheel mechanism of a trifooted mobile service robot determines its driving performance. Currently, two independent actuators adjust the wheel's three feet adaptively, but we aim to develop novel single-actuator-operable 1-DOF transformable wheel mechanisms. Due to the unexplored nature of 1-DOF mechanisms, the trial-and-error approach may fail to find such mechanisms. Herein, we propose a fully automated gradient-based design approach that simultaneously determines the mechanism's topology, dimension, and joint type without a baseline mechanism. We take both fundamental kinematic and functional (such as torque–force transmission ratio) requirements into account. Our formulation employing a unified ground synthesis model is newly established to consider the trajectory and orientation of the mechanism end effector, control the number of synthesized prismatic joints, and satisfy the torque–force transmission ratio. Under various design constraints, we successfully synthesized novel mechanisms and their functionalities were validated via simulations and the motions of their prototypes.