A wearable robotic arm with high force-reflection capability

Many exoskeletal robotic arms have been developed for teleoperation having force reflection. They can measure an operator´s arm motion and apply reactive force to the operator as well. Previous research has emphasized control performance of motion tracking and force reflection mainly but ignored how comfortable an operator feels, that is, issues of human wearability. Most robotic arms are heavy and give an operator excess fatigue during the teleoperation. We propose a robotic arm that satisfies high wearability and high force-reflection simultaneously. In order to accomplish these two objectives, the proposed arm has a parallel mechanism, one for a forearm and the other for a brachium. The parallel mechanism has an analogy to human muscular structure in which many extensors and flexors interact with each other and generate torque. The prismatic joints in the parallel mechanism act as virtual human muscles and determine joint torque by contraction and relaxation. The configuration of the prismatic joints enhances human wearability because all the joints are placed on the circumference of cylinders. Consequently, this circular configuration distributes internal force over an arm and thus contributes to reduce human fatigue during operation. In addition, the robotic arm does not make any singularity in its kinematics. The kinematic parameters in the robotic arm are selected to maximize the operator´s workspace while considering performance of force reflection