Abstract: Upper limb exoskeletal rehabilitation robots are required to assist patients’ arms to perform activities of daily living according to their motion intentions. In this paper, we address two questions: how to design an exoskeletal robot which can mechanically reconstruct func-tional movements using only a few actuators and how to establish wrench-based assistive control. We first show that the mechanism replicating the synergic feature of the human upper limb can be designed in a recursive manner, meaning that the entire robot can be constructed from two basic mechanical units. Next, we illustrate that the assistive control for the synergetic exoskeletal robot can be transformed into an optimization problem and a Riemannian metric is proposed to generate anthropomorphic reaching movements ac-cording to contact forces and torques. Finally, experiments are carried out to verify the functionality of the proposed theory.

Key words: upper limb exoskeletal robot, postural synergy, wrench based assistive control