Can a Continuum Manipulator Fetch an Object in an Unknown Cluttered Space?

Continuum manipulators are particularly suitable for performing tasks in cluttered environments with limited space for maneuvering. While there is progress on continuum grasping of an object in a cluttered space, if the environment is unknown where the target object is occluded and only partially visible, such as in a search and rescue scenario, an open problem is how to determine if it is possible to fetch the object. In this letter, we address this problem of online determining whether a partially occluded object nested in an unknown cluttered space can be fetched by a continuum manipulator based on sensing the surrounding obstacles progressively with a distance sensor attached to its tip, and if so, how to fetch the object autonomously. Our method formulates constraints that can be quickly checked from sensed information to decide if a solution exists for a multisection spatial continuum manipulator to access and grasp an object in a cluttered space. Examples using point clouds of unknown obstacles from RGB-D sensing illustrate the effectiveness of our approach.