The objective of this article is to present the dimensional synthesis of serial or parallel spherical wrists, an important step in the design process of medical robots. This step is carried out to obtain optimal dimensions of tool-guidance medical robots. In this goal, we have first studied the specifications of two robots with different medical applications: one for minimally invasive surgery and one for tele-echography examination. Then, we have established that the medical needs expressed by the doctor were very different but the specifications in robotic terms have a lot of common points (kinematics, workspace, bulkiness). Both types of robots need a mobility of three rotations around a fixed point (trocar incision or probe contact point on patient’s skin). So a spherical wrist structure is adapted to their needs. An important constraint related to medical applications is that the robot must be compact to not obstruct the robot environment (medical personnel or patient). We perform dimensional synthesis allowing determination of dimensions of the mechanism for a spherical wrist, serial and parallel for a tele-echography robot, and serial for the minimally invasive surgery robot. We used multi-criteria optimization methods minimising a cost function to obtain both good kinematic performance and compactness for the structure. The difficulty and the difference between the presented studies are in the choice of design criteria describing the performance and the constraints of the robot. These parameters must faithfully represent the specifications of the robot so that its performance can respond to the medical requirements. We show, here, the different methods used for the chosen kinematic structure and the medical application. These studies lead to prototypes which are validated by medical experiments. This process of dimensional synthesis will be applied to other medical applications with different sets of specified constraints.
展开▼
