Increasing the accuracy with a rich sensor system for robotic laser osteotomy

In laser osteotomy bone is cut precisely with a laser. A robot is used to position an end-effector with a scanhead, which deflects the cutting laser. An optical tracking system (OTS) tracks the position of the bone, in our case a skull, and the end effector. The skull is registered to its model, based on a segmented CT data, as well as the robot to the OTS. With this a complete transformation chain between the model and the robot coordinate system is given. Using the transformation chain the positions, where the laser beam is emitted and where it has to incise the skull, can be computed for the robot coordinate system. The complete registration processes introduce different errors in every step. To achieve clean cuts the correct distance between scanhead and ablated bone segment is crucial. Therefore a distance sensor is attached to the end-effector, measuring the distance to the skull with an accuracy of 100 ¿m. The value is used to adjust the positioning to the correct distance.