Oscillation, Orientation, and Locomotion of Underactuated Multilink Mechanical Systems

We consider a class of multilink mechanical systems arising from undulatory locomotion of multisegmental slender animals. All the body joints are assumed to have actuators, but the system is underactuated because of the lack of direct control over the position and orientation within the inertial frame. Yet, the system is controllable through interactive forces from the environment, just like in animal locomotion. It is systematically revealed that the motion behavior is composed of three fundamental actions: 1) oscillation; 2) orientation; and 3) locomotion. Through rigorous theoretical analyses and numerical simulations, feedback laws are developed to achieve effective control for the aforementioned three actions, exploiting the natural dynamics of body-environment interactions.