Development and Control of an Anthropomorphic Telerobotic System

Abstract

This work presents and summarizes the research work carried out during the development and experimental evaluation of a dual arm anthropomorphic manipulator designed for teleoperation purposes. The results are generalizable to other types of manipulators, especially for robots acting in human environments and/or physically interacting with humans. Such applications pose specific requirements that are in general different from those of traditional robot design. To assure safety and stable operation, ``soft'' robotic manipulators are absolutely essential. For this reason, in this work, compliance control methods were extensively studied and evaluated experimentally. As a result, an impedance control strategy with underlying stiffness controller in motion control loop is proposed. To achieve proper workspace matching between the human arm and the developed manipulator, an adequate singularity handling strategy must be applied. Experimental comparison of such solutions is performed and an innovative damped inverse kinematics method is introduced. This method allows for traversing through singularities with simultaneous weighing of the task space tracking error. Because the kinematic structures of the master/slave manipulators in a teleoperation system are in general dissimilar, there is a need for a universal kinematic interface, independent of the device structure. The classical approaches using Euler or Cardanian angles fail due to algebraic singularities introduced by the representation. To avoid this problem, the unit quaternion was used for describing orientation and corresponding rotational displacement. In order to avoid the collisions between the arms and the workspace limits a virtual forces concept was introduced. This application forms a basis for local optimization strategies and an intuitive force display for the human operator. Finally, the force - position teleoperation control architecture was analyzed and a tele-assembly experiment in 6 DoF was successfully performed. The experimental results confirm the high performance of the developed hardware and control strategies.