This paper describes a new compact bending and disposable (to avoid nosocomial contaminations) plastic wrist for minimally invasive surgery with a large free space for several connections such as electrical wires, fiberoptics and fluidic tubes, etc. It uses small partially locked ball joints to increase the dexterity of surgical tools in all directions contrary to other wrists using several successive orthogonal joints. This compact wrist is a generic concept comprises at least two vertebrae composed of non-attached contacts: plastic plates and balls. Six metal wires drive the position of each vertebra and several other free wires allow the locking of wrist axial rotations. Analytic and finite element simulations allow an evaluation of the mechanical rigidity of the wrist by several parameters: the wire number, diameter, position, mechanical properties and the general geometry of the wrist. The wrist is fabricated with 6 mm biocompatible plastic vertebrae micromachined by low cost water jet cutting. It uses 0.3 mm NiTi super-elastic wires for its mechanical structure which enable two degrees of freedom (DOF) in any directions between -85 degrees and 85 degrees. The two DOFs of the wrist and the DOF of the forceps are driven by a handled basic system using pulleys, 0.5mm Topline/spl reg/ ropes connected to NiTi wires and four RC-servomotors. In the first prototype 6 electrical wires, 2 micro-light emitters and 4 fiberoptics were successfully integrated. We are convinced of the effectiveness of this compact disposable plastic wrist, to be used with a usual or a motorised handled surgical instrument and integrating new functionalities such as electrical/optical/fluidics connections for smart surgical embedded micro-systems like micro-sensors and micro-actuators.

In this paper is presented an architecture permitting the specification and resolution of complex motion and calibration tasks. The description of such tasks leads to nonlinear functions optimization under equality and/or inequality constraints. The latter appears very commonly during robotics tasks execution. For example, while moving in a cluttered environment, it might be useful to keep some objects away from obstacles. The proposed method is based on a task description in terms of contact relationships to establish or maintain between parts of the modeled system. Some typical examples of tasks have been specified and performed to demonstrate the presented concepts. This architecture has been designed with the intention to integrating it into a remote manipulator teleprogramming system.

The authors present an assembly motion planner for two polyhedral objects. The retraction subspace is defined by the configuration of these objects where they are in a particular contact such that the motion has zero or one degree of freedom. The planner gives assembly trajectories defined by a set of contacts. Each portion of the generated path is associated to a contact state with constant qualitative properties. A contact graph is associated to the boundary structure of the configuration space. The planner includes an incremental method to build the graph and to find a path. Some heuristics are defined to select locally the best arcs to compute. A first version of the planner has been implemented. Simulation results of an assembly trajectory planned by the system are presented.>