On the Design of Parallel and Hybrid Anthropomorphic Robot Arms: Type Synthesis and Alternative Hybrid Architectures

Abstract This article presents an attempt at a type synthesis of four-degree-of-freedom parallel mechanisms that produce an SR-equivalent motion pattern in order to replicate the movement of the human arm, as well as a potential hybrid alternative for anthropomorphic robot arms. First, the virtual chain approach used throughout the article is recalled. The wrench system reciprocal to the desired twist system of the kinematic chain is then determined. Afterwards, the potential legs that could be used for SR-equivalent parallel mechanisms are found. Next, the legs are assembled in order to produce potential architectures. Valid sets of actuated joints for the various architectures are found, which leads to the findings that SR-equivalent architectures are either serial or hybrid mechanisms. The validity of the architectures is thus assessed. Then, alternative motion patterns and hybrid architectures are proposed. A promising spherical robot shoulder is introduced. Finally, the kinematic analysis of a specific arrangement of said shoulder is performed.