Cartesian control issues for minimally invasive robot surgery

Telepresence in minimally invasive surgery (MIS) is a promising application for robotics because the robot enhances the manipulation and sensation capabilities of the surgeon. Many of these surgical robots are equipped with passive joints that guarantee that no forces are exerted to the entry point. Due to these passive joints, which are dependent on the entry point´s position, new algorithms for cartesian control have to be developed. After introducing the kinematics of the robot, used in the DLR minimally invasive robot surgery scenario, we show how the entry point (trocar) can be estimated, followed by the calculation of the inverse kinematics. To allow cartesian velocity control of the robot system we build an observer that is used to close the velocity control loop. Experiments show the performance of the chosen algorithms