Evaluating Control Modes for Hand-Held Robotic Surgical Instrument Using Virtual Reality Simulator Ali Hassan Zahraee, Jerome Szewczyk and Guillaume Morel Universite Pierre et Marie Curie - Paris 6 Institut des Systemes Intelligents et de Robotique 4, Place Jussieu, 75005 Paris, France {zahraee, sz, morel}@robot.jussieu.fr Abstract— This paper discusses 3 different control modes for a hand-held surgical robot. A virtual reality simulator for evaluating control modes is developed. Different control modes are evaluated and compared in a suturing task. Results show a better control and more precise sutures with a semi-coupled inverse control mode in frontal and sagittal suturing. I. INTRODUCTION Minimally invasive surgery (MIS) is a type of surgical operation in which surgeon inserts surgical instruments inside patient’s body through small incisions. Each instrument passes through a trocar, a cylinder with a sharply pointed end, inserted in the patient’s body to make an incision. It is common to insert 2 instruments and an endoscope at a time, through 3 incisions made on the vertices of a triangle. In single-port MIS, the instruments and the endoscope are inserted through a single incision. Conventional instruments used in MIS are hand-held instruments with long shafts, an effector (a grasper, a cutter etc.) at one end and a handle at the other. In these instruments, the effector is rigidly connected to the shaft. Certain gestures are very difficult or impossible to make using conventional instruments, especially in single-port surgery. Because the instrument passes through a port and is effectively constrained by a pivot point. So it’s motion is constrained to 4 degrees of freedom (DOF) [1]. The 4 DOF are: (1) translation along the shaft of the instrument, (2) rotation around the translational axis and (3) and (4) limited inclination of the shaft pivoted trough the incision [2]. A robotic instrument with a jointed effector can facilitate difficult gestures. The joint adds 1 or more degrees of freedom (DOF) to the effector. Thanks to these additional DOF, the surgeon can make sutures or cuts which are either hard or impossible to do with a conventional instrument. How the surgeon controls the effector and how his hand’s DOF are mapped to the effector’s DOF is a major issue in the design of a hand-held robotic instrument [3]. One approach is to control the effector using buttons, dials or joysticks integrated in the handle as in [4], [5] and [6]. Another approach is to joint the handle to the shaft and map the DOF added to the handle to the DOF of the effector as in [7] (Fig. 1), [8], [9] and [10]. Although these last 2 examples are not mechatronic, but pure mechanical instruments, we are dealing with the same problem of controlling the effector in Fig. 1. RealHand TM , a mechanical instrument with a jointed effector their design. The way the DOF of the handle are mapped to the DOF of the effector is called the control mode [2]. A non- intuitive control mode leads to long learning curves, longer operation times and more importantly, additional burden on the surgeon. The surgeon has to do a cognitive remapping to resolve the incompatibility of the viewpoint presented by the endoscope and his spatio-motor expectations [2]. A non- intuitive control makes this remapping more complicated. All instruments with articulated effectors previously men- tioned, those with articulated handles as well as those with joystick handles, claim to have intuitive controls. There has been some studies to compare a few of them. But an extensive study of control modes in hand-held surgical robots is missing in the literature. However, making robots with different control modes, interfaces and effector kinematics to compare and choose the best one is not a good idea as many configurations are imaginable. That’s why we made a simulator in which we can easily change the control mode, the interface and the effector’s kinematics to compare and evaluate them. This paper presents our preliminary results from a rather limited test campaign. More results will be published in our future publications. II. THE SIMULATOR Using the second approach to the control of the effector, i.e. by mapping the DOF of a jointed handle to the DOF of a jointed effector, we developed a virtual reality (VR) simulator to evaluate different control modes. The Simulator is a platform allowing an operator to perform certain surgical tasks in a VR environment, using an instrument with a 6 DOF handle and a 6 DOF virtual effector. The simulator is composed of a laparoscopic training box, a Polaris tracking system, a surgical instrument with Polaris targets installed on its shaft and handle, a monitor and a PC 2009 IEEE/ASME International Conference on Advanced Intelligent Mechatronics Suntec Convention and Exhibition Center Singapore, July 14-17, 2009 978-1-4244-2853-3/09/$25.00 ©2009 IEEE 1946