Andreas Köpfle

EFFICIENT INVERSE DYNAMICS OF A PARALLEL ROBOT WITH TWO MOVABLE PLATFORMS

Abstract An efficient algorithm for the calculation of the inverse kinematics and dynamics considering a parallel robot with two movable platforms is proposed. The approach is based on the Newton-Euler formalism, the virtual work principle, and the usage of the instantaneously coincident coordinate frame of the robot base. Corresponding to a hand-held surgical robot application, the derived inverse dynamics solution is capable to describe the forces which are required (1) to generate the desired motion of the tool and (2) to decouple the tool from disturbances induced at the base.

A Modular Scalable Approach to Occlusion-Robust Low-Latency Optical Tracking

An advanced optical tracking system for computer assisted surgery (CAS) is presented. The system supports an arbitrary number of cameras that may be placed at suitable positions e.g. fixed cameras at the ceiling of the operating theater or movable cameras on the operating lamps. The modular scalable system architecture reduces occlusion problems and allows adaptation to tracking scenarios of different complexity. The camera modules each integrate hardware-based image processing to allow for low latency of 10ms required in demanding applications like robot control. As a first application tracking of a handheld robotic manipulator has been implemented.

Control of a Handheld Robot for Orthopaedic Surgery

Abstract The controller design and implementation of a handheld surgical robot is presented. During the treatment of human bones the robot is able to compensate un-voluntary movements of the surgeon and of the patient and to find automatically the target position of the tool. The robot system is based on a Stewart-platform actuated by linear motors and on an optical tracking system. A cascade controller provides a local position and velocity control of the motor axes and an absolute position control in the world frame. To show the feasibility of the concept, cavities are milled into polystyrene-foam, while the robot is decoupled from the test bed. For clinical demands the robot has to be improved in the static and dynamic accuracy.