A unified language for anthropomorphic arm motion

Abstract

When abundant humanoid robots are springing up in many application fields, the anthropomorphic arm, which is the most important part of the humanoid robot, is facing numerous complicated manipulation tasks. In order to address two diversity issues of anthropomorphic arm platforms and manipulation tasks, a unified "language", a novel task-motion planning method, for different anthropomorphic arms is developed to describe and plan their motion in this paper for the first time. Firstly, six principal rules of human arm motion are extracted from a lot of literature in Neurophysiology. According to these rules, a general library of movement primitives and a well-defined set of motion grammar rules are designed to form a complete motion language for anthropomorphic arms. The movement primitives in the library can be divided into two categories in terms of different spaces: movement primitives described in the operational space to control the position and orientation of the wrist and primitives described in the human arm triangle space to control the configuration of the whole anthropomorphic arm. Movement primitives are the fundamental motion elements of the motion language. Then, according to the motion grammar, goal tasks can be constituted by some movement primitives and movements in terms of a " movement primitive-movement-task" three-level structure. As the operational space and the human arm triangle space are independent of the structure and dimension of the anthropomorphic arm, the designed primitives in the two spaces exist in all anthropomorphic arms. An interface between the motion language and the anthropomorphic arm is developed to solve for joint trajectories of every movement primitive for a specific arm. Finally, by comparing with a traditional method, the proposed motion language is demonstrated to have several advantages including comprehensive control of motion process, replication of motion, and large range of motion planning.