Motion Planning With Uncertainty For Highly Redundant Kinematic Structures I. "Free Snake" Motion

Abstract

A strategy is described for on-line motion ]planning with incomplete information for a special type of highly redundant planar robot kinematics, called a snake. The snake consists of many simple serially connected links and has on-line sensing which provides information about its immediate surroundings. The task is to move the snake head point from its starting position to a known target position while generating collision-free motion for the rest of the snake body, in an environment filled with unknown obstacles of arbitrary shape. Computationally, the procedure is linear in the number of the snake Links; it is highly efficient and can be easily realized in real time. The procedure makes use of a unit motion far a single link based on the tractriz curve. This choice results in automatically achieving a “natural” motion distributed continulously and asymmetrically along the snake body - the joint displacements tend to ‘“die out” in the direction from the head to the tail. The generated path possessies an optimality property - the instantaneous total displacement of all the links/joints is minimum.