Novel Tripedal Mobile Robot and Considerations for Gait Planning Strategies Based on Kinematics

This paper presents a novel tripedal mobile robot STriDER (Self-excited Tripedal Dynamic Experimental Robot) and considerations for gait planning strategies based on kinematics. To initiate a step, two of the robot’s legs are oriented to push the center of gravity outside the support triangle formed by the three foot contact points, utilizing a unique abductor joint mechanism. As the robot begins to fall forward, the middle leg or swing leg, swings in between the two stance legs and catches the fall. Simultaneously, the body rotates 180 degrees around a body pivot line preventing the legs from tangling up. In the first version of STriDER the concept of passive dynamic locomotion was emphasized; however for the new version, STriDER 2.0, all joints are actively controlled for robustness. Several kinematic constraints are discussed as the robot takes a step including; stability, dynamics, body height, body twisting motion, and the swing leg’s path. These guidelines will lay the foundation for future gait generation developments utilizing both the kinematics and dynamics of the system.