Motion analysis and stability optimization for metamorphic robot reconfiguration

Abstract

Metamorphic robots are a new type of unmanned vehicle that can reconfigure and morph between a car mode and a biped walking machine mode. Such a vehicle is superior in trafficability because it can drive at high speeds on its wheels on structured pavement and walk on its legs on unstructured pavement. An engineering prototype of a metamorphic robot was proposed and designed based on the characteristics of wheeled–legged hybrid motion, and reconfiguration planning of the robot was conducted. A kinematics model of the reconfiguration process was established using the screw theory for metamorphic robots. To avoid component impact during the rapid global reconfiguration and achieve smoothness of the reconfiguration process, a rotation rule for each rotating joint was designed and the kinematics model was used to simulate and validate the motion of the system’s end mechanism (front frame) and the entire robot system. Based on the kinematics model and the rotation rules of the rotating joints, a zero-moment point (ZMP) calculation model of the entire robot mechanism in the reconfiguration process was established, and the stability of the reconfiguration motions was evaluated based on the ZMP motion trajectory. The foot landing position was optimized to improve the robot’s stability during the reconfiguration. Finally, the smoothness and stability of the reconfiguration motion were further validated by testing the prototype of the metamorphic robot.