A new robot path planning methodology, called obstacle accommodation, has been introduced for robots in cluttered environments. This methodology does not attempt to avoid physical contact between the robot and obstacles. Instead, it controls the contact to prevent damage to the robot. Obstacle accommodation represents a new robotic paradigm in which obstacles can contact robots at unspecified positions, i.e., a contact point can be at any point on any link. Obstacle accommodation requires analysis in kinematics, motion planning, dynamics, and control. This paper deals with the development of the kinematic constraints and with motion planning under these constraints. We begin by providing a general formulation of the motion constraints due to contact with obstacles. Next, a new inverse kinematics is presented that provides joint motion for robots under contact constraints. Finally, the new motion planning algorithm for robot motion in a cluttered environment is provided. The motion planning algorithm is verified by two examples, one on a linkage robot and the other on a mobile robot.>

Abstract-The paper presents the design and motion planning for a mechanical snake robot that was built at the University of Michigan. The structure of the robot enables it to move without wheels. It is constructed of a series of articulated links, each one with a motor and linear solenoid. Although each link has only one motor, this structure allows the body configuration to be easily controlled thereby enabling the robot to move in very cluttered environments. The motion planning system provides the robot with a basic motion pattern that can be easily modified for different tasks and environments. The mechanical snake does not avoid obstacles on its way, but rather “accommodates ” them by continuing its motion towards the target while in contact with the obstacles. With our design and motion planning, each link has a different number of degrees-of-freedom in each motion stage, providing the robot with great adaptability even during contact