Experimental comparative evaluation of compliant control schemes for an anthropomorphic personal robot

This paper investigates the problem of controlling an anthropomorphic robot arm with autonomously variable compliance in order to ensure safety in the interaction with humans and, above all, to increase the robot functionality in tasks of physical interaction, performed in co-operation with humans. The research work aims at applications in service robotics where the robot arm is used as a 'personal robot', for assistance to humans in different aspects of their everyday life. In personal applications of robotics, human-robot interaction represents a critical factor for the design of the robot and introduces strict requirements on its behavior and control, which has to ensure safety and effectiveness. Two different compliant control schemes have been developed for the peculiar structure of the Dexter robot arm, an anthropomorphic 8 d.o.f. manipulator, and their performances have been comparatively evaluated through experimental trials. The comparative evaluation of the two control schemes, through the analysis of their different advantages and disadvantages, points out an overall better performance of the compliant control scheme in the joint space, relatively to the management of the mechanics of the robotic system. So, it emerges how the performances of the two control systems are inverted with respect to the theoretical considerations on their accuracy and effectiveness, that could be done on the basis of the classical control theory. After a brief description of the control models, the paper focuses on the experimental sessions aimed at verifying the level of accuracy, affordability, functionality and safety of the implemented control systems.