In this paper we discuss the problem of achieving good performance in accuracy and promptness by a robot manipulator under the condition that safety is guaranteed throughout task execution. The particular but basic problem of single-joint actuation is considered in detail. Intuitively, while a rigid and powerful structure of the arm would favour its performance, lightweight compliant structures are more suitable to safe operation. The quantitative analysis of the resulting design trade-off between safety and performance is one of the objectives of our work. Such analysis has a strong impact on how robot mechanisms and controllers should be designed for human-interactive applications. We discuss few different possible concepts for safely actuating joints, and focus our attention on one, the Variable-Stiffness Transmission (VST) approach. Some aspects related to the implementation of the mechanics and control of VST joints are reported.
PUBLISHER'S NOTE: In this paper, there are three errors introduced during production. First, the correct title of the article is Fast and Soft Arm Tactics. Also, on formulae for GSI and HIC in page 23, the acceleration is measured in multiples of the acceleration of gravity (g) [not grams], while time is measured in seconds. Finally, within Figure 1, one should read Compliant Covering, and Mrob = Mrotor + Mlink [instead of Krob = Krotor + Klink]. Please visit http://www.ncsu.edu/IEEE-RAS/RAM/BicchiFigure1.pdf to see the original figure.