Crawling Locomotion of Modular Climbing Caterpillar Robot with Changing Kinematic Chain

Based on the modular concept, this paper presents two caterpillar robot prototypes which are inspired by two typical caterpillars: inchworm and pine caterpillar. The inchworm robot prototype features simplest kinematics and open chain architecture. Due to the fact that there is only one attachment module supporting the inchworm robot during crawling, we apply an unsymmetrical phase method (UPM) to realize a stable crawling gait for it. A pine caterpillar robot is derived from combining two inchworm robots together. The crawling gait of it features a repetitive changing chain: open-closed-open. Besides the UPM in open chain states, a four-links kinematic model is applied to control the corresponding joints to transfer the crawling wave along the robot body in the closed chain state. These two prototypes are all constructed and, and their crawling locomotion abilities have been tested on vertical glasses respectively.