ABSTRACT
The purpose of Computer-Assisted Surgery (CAS) is to help physicians or surgeons to plan and to execute optimal strategies from multi-modal data. The execu tion of such planned strategies may be assisted by guid ing systems. Passive systems based on 6D localizers give information to the operator such that he can com pare the planned task to the real one he executes. Active systems are robots that realize part of the intervention autonomously. Semi-active systems, more generally called synergistic systems, are based on the cooperation of a robotic device with a human operator. We have developped such a synergistic device : PADyC (Passive Arm with Dynamic Constraints). The basic principle of PADyC is to have a manually actuated arm that con strains the authorized motions of the surgical tool held by the human operator in function of a planned task. For instance, if the task is to stay inside a given 3D cartesian region, the motions of the tool will be free in side the region whilst some of them will be forbidden on the borders of this region. These constraints are realized by a patented mechanical system.
