Abstract: Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment, just like natural living beings. And the smart design could efficiently improve the performance of a robotic leg. Inspired by the simplified human leg structure, we present a 3-DOF robotic leg—OmniLeg, that is capable of making omnidirectional legged locomotion while keeping constant posture of the foot. Additionally, the concentrated drive mode, in which all the motor actuators are installed in the torso and do not move with the leg, minimizes the inertia of the robotic leg. In this paper, the modular design, the kinematics model, the structural analysis, the workspace, and the performance evaluation of the OmniLeg are discussed. Furthermore, we build a prototype based on the proposed design, and the precision of it is verified by the error calibration experiment which is conducted by tracking the trajectory of the prototype’s endpoint. Then, we present an OmniLeg-based single legged mobile robot. The capability of omnidirectional legged locomotion of the OmniLeg is demonstrated by the experiments.

Key words: Human leg , · Robotic leg , · Omnidirectional legged locomotion , · Spatial dual-parallelogram-linkages , · Spatial closed-loop four-bar