The transformable wheel mechanism of a tri-footed 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.

A new lizard-inspired robot is presented in this paper, which enables to maintain its moving direction by lateral body motions even during high-speed bipedal running. First, a dynamic model for lizard-inspired robot is derived to simulate the lateral body motion of real lizard. Based upon the simulation using dynamic model, the lizard-inspired robot is tactfully built so that its hind leg is optimally designed on a 4-bar mechanism and its body is simplified to consist of two body links and a tail connected by two revolute joints. The experiments verify that the proposed robot can maintain its moving direction via proper lateral motions during high-speed bipedal running similar to that of real lizard.

This paper presents a new mobile robotic platform (R-Mo) which can reduce unexpected variations in height as well as pitch angle of its main body while traversing rough terrains. As a measure for the smooth movement of mobile platform, the variations in height and pitch angle are chosen in this study. Then, the kinematic analysis on the Rocker-Bogie mechanism is carried out to investigate its variations in height and pitch angle on rough terrains. Based on this result, a new mobile platform is systematically designed by combining the Rocker-Bogie with the inverse four bar linkage. The extensive experiments are carried out by using the Rocker-Bogie mechanism and the proposed R-Mo against rough terrain, which validate that in comparison with the Rocker-Bogie mechanism, the average and maximum variations in height of proposed R-Mo are reduced by 12.72% and 5.96%, respectively, and the average and maximum variations in pitch angle of proposed R-Mo are considerably reduced by 65.87 % and 60.53 %, respectively.