Obstacle-free Control of the Hyper-redundant Nasa Inspection Manipulator

This paper presents a follow-the-leader algorithm for serpentine control of hyper-redundant manipulators. Given an obstacle-free trajectory for the manipulator tip generated by a path planner or teleoperation, the follow-the-leader algorithm ensures whole-arm collision avoidance by forcing ensuing links to follow the same trajectory. The algorithm requires two steps to place the tip on each trajectory point: first, fit the manipulator to the trajectory, tip to base; and second, solve inverse position kinematics, base to tip. The general method is presented and can be used off-line or on-line. It is then applied in a modular manner to a specific serpentine manipulator system, the Payload Inspection and Processing System (PIPS) at NASA Kennedy Space Center. PIPS is designed for inspection of Space Shuttle payloads after integration and prior to launch. The follow-the-leader algorithm completely constrains the kinematic redundancy and limits the manipulator workspace. This limitation is justified in sensitive, cluttered environments such as the Shuttle payload bay. The method has been successfully implemented on prototype hardware at NASA.