The 2 nd IFToMM Asian Conference on Mechanism and Machine Science November 7 -10, 2012, Tokyo, Japan A SPHERICAL ROBOTIC ARM FOR INSTRUMENTS POSITIONING IN MINIMALLY INVASIVE MEDICAL APPLICATIONS Calin VAIDA, Bogdan GHERMAN, Doina PISLA and Nicolae PLITEA 1 The development of robotic devices for the manipulation of minimally invasive instruments is focused on two major categories divided by their approach with regard to the insertion point in the patient body, each solution having both advantages and drawbacks. The paper presents a spherical positioning robotic arm which combines these two categories, summing the advantages and minimizing the drawbacks. The inverse and direct kinematic models are solved. The workspace analysis, precision mapping and singularities analysis are performed. Several configurations are proposed to suit different operating scenarios. Keywords: spherical mechanism, kinematics, modularity, minimally invasive surgery 1. Introduction “A wise man should consider that health is the greatest of human blessings, and learn how by his own thought to derive benefit from his illnesses.” (Hippocrates) In parallel with the continuous evolution and discovery of new minimally invasive surgical (MIS) procedures, the technology evolution enabled the introduction of robotic systems in the operating rooms. Taylor [1], published a study where a synoptic comparison between man and machine is achieved, pointing out the some of the potential benefits of robotic surgery. Since then, robotic surgery became a fast evolving field of research, with demanding challenges and outstanding achievements. Some of the direct benefits of robotic surgery with respect to classical MIS refer to: miniaturization, enhanced reachability for instruments, high precision, ambidexterity and elimination of the natural hand tremor. Referring to endoscopic surgery, the robotic structures can be divided into three major groups: the first one integrates the laparoscope holders, the second one integrates complex surgical systems and the third group contains solutions acting as assistants to the surgeons. Referring to the group of laparoscope holders, the first structure ever to be used in the operating room is AESOP [2]. FreeHand [3] from Prosurgics is a robotic arm that positions the laparoscopic camera following the head motions of the surgeon. Endocontrol developed ViKY, [4] a laparoscope holder with foot, hand and voice control for the camera positioning. In a study published in 2010, Taniguchi et al [5] make a roundup of all Endoscope Robots developed worldwide up to the 2009 SMIT congress summing up a number of 27 robotic structures, including the first Romanian laparoscope holder, PARAMIS [6]. In the second group of complex robotic systems for surgery, several solutions were achieved. HERMES [7] is used to control all the equipment in an operating room using voice commands. The platform of AESOP is later used to create a multiarm robotic system, named Zeus, able to manipulate 28 different instruments including scalpels, hooks to tie knots, scissors and dissector [7]. At the same time, Intuitive Surgical [8] launched the da Vinci robotic system, which slowly reached a worldwide spread, providing real benefits in numerous surgical procedures. Researchers have tried to define alternative robotic solutions for surgery, trying to eliminate the drawbacks reported by da Vinci while preserving its performance. Robin Heart is a Polish project [9] that develops a robotic system optimized for cardiac surgery. Perelli proposes a modular structure three arms, the Navi-Robot and an end-effector consisting of a double parallel 4 bar linkage mechanism [10] which can manipulate classical instruments. The MIRO robot arm is a part of an advanced research project of DLR consisting in a light-weight, kinematically redundant arm capable of working in a single or multiarm setup [11]. Attached to MIRO, MICA is 3 DOF compact instrument, which introduces force- feedback on all axes [12]. Referring to the third group of robots a great success has been achieved by Penelope [13], the robotic scrub nurse, designed to deliver the surgical tools at the surgeons’ request. All the robotic structures for MIS share a common characteristic, as they have to manipulate the end- effector through a fixed point in space, the MIS entry port. In [14] Beira et al present a synthesis of passive and mechanically constrained solutions for obtaining the remote center of motion (RCM) and propose an innovative parallel manipulator with 4 DOF and a fixed RCM. Arata et al develop in [15] a neurosurgical robotic system for brain tumor removal with a fixed 1 C. Vaida, B. Gherman, D. Pisla and N. Plitea are with the Dept. of Mechanical Systems Engineering, The Technical University of Cluj-Napoca, ROMANIA, calin.vaida@mep.utcluj.ro, bogdan.gherman@mep.utcluj.ro, doina.pisla@mep.utcluj.ro, nicolae.plitea@mep.utcluj.ro