Combined image-based and depth visual servoing applied to robotized laparoscopic surgery

In this paper, we address the problem of controlling the motion of a surgical instrument close to an unknown organ surface by visual servoing in the context of robotized laparoscopic surgery. To achieve this goal, a visual servoing algorithm is developed that combines feature errors in the image and errors in depth measurements. The relationship between the velocity screw of the surgical instrument, the depth and the motion field is defined and a two-stage servoing scheme is proposed. In order to measure the orientation and the depth of the instrument with respect to the organ, a laser dot pattern is projected on the organ surface and optical markers are stuck on the instrument. Our work has been successfully validated with a surgical robot by performing experiments on living tissues in the surgical training room of IRCAD.