A motion control and obstacle avoidance algorithm for hyper-redundant manipulators

To carry inspection or repair work in cluttered environments, such as a ship wreckage, conventional nonredundant or mildly redundant manipulators may suffer from unavoidable collision with obstacles. Inspired by the manipulation of "elephant trunks" and the motion of "snakes", the idea of hyper-redundancy is introduced to solve this problem. The term "hyper-redundancy" refers to redundant manipulators with a very large number of degrees of freedom. In addition to the degrees of freedom needed to achieve major tasks specified for the end-effector, the rest of the degrees of freedom, or hyper-redundancy, can be used to carry out secondary tasks or to meet constraints imposed by the environment. This paper presents a artificial conservative field method which integrates inverse kinematics with obstacle avoidance so that obstacle avoidance can be done online. It treats manipulators as elastic structures carrying electric charges, and obstacles as point charges or line charges. Potential energy flows between these systems will drive manipulators to a state of equilibrium which all manipulator links stay away from all obstacles as far as possible. Another by-product of this method is the repeatability of kinematics solutions if no singularities are met. A formulation is given with examples to illustrate this approach.