A passive arm with dynamic constraints: a solution to safety problems in medical robotics

In Latombe (1991) one can read: “One of the ultimate goals in robotics is to create autonomous robots. Such robots will accept high-level descriptions of tasks and will execute them without further human intervention. The input descriptions will specify what the users wants rather than how to do it. The robots will be any kind of versatile mechanical device equipped with actuators and sensors under the control of a computing system.” In the last two decades, a major part of the efforts of the research in robotics and automation has been devoted to the realization of such autonomous systems. Their application to medicine or surgery turns out to be very difficult since they have not been thought for such a drastically different use. Indeed, in that field, the robot has to cooperate with a man (a surgeon or a physician) to assist, rather than to replace, him in the realization of complex, precise and/or dangerous tasks. Since the surgeon is primarily working with his hands, the most suitable help for him is the one that makes possible the physical guiding of these hands. The robot can be seen as a very well-suited man-machine interface that allows for a more quantitative use of medical images. Because it has to be used in a human environment, it cannot be “any kind of versatile mechanical device” as suggested before but if must be a safe, accurate and user-friendly system. The authors are interested in designing such a system, intended to increase human capabilities. In this paper, the authors present a new type of mechanical guiding system, named “passive arm with dynamic constraints”, that they are designing. Such a system is intended to combine some advantages of both passive and active systems: the complexity of tasks potentially achieved by an active system with the limited risk involved by a passive one