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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics VIRTUAL MODELING OF A LAPAROSCOPIC SURGICAL RO...

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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics

VIRTUAL MODELING OF A LAPAROSCOPIC SURGICAL ROBOT WITH HYBRID KINEMATICS Mihai Mărgăritescu National Institute of Research and Development in Mechatronics and Measurement Technique Bucharest, Șos. Pantelimon 6-8, Romania [email protected] Ana Maria Eulampia Rolea National Institute of Research and Development in Mechatronics and Measurement Technique Bucharest, Șos. Pantelimon 6-8, Romania [email protected] Vlad Văduva National Institute of Research and Development in Mechatronics and Measurement Technique Bucharest, Șos. Pantelimon 6-8, Romania [email protected] Abstract - Although surgical robots are already functional, however it is considered that they are now in incipient stage. Currently, the surgical robot can not perform independent actions, but serves as a direct extension of the surgeon hand. These devices accurately replicate the action of a surgeon, but have no artificial intelligence or automated subroutines. They are complex and very expensive and there is a concern to produce models more accessible, while keeping the performance. A first step in developing and testing a new robot is to create a virtual model that allows identification of the design deficiencies in an early stage, thus saving time and other resources. This article describes such a virtual model with hybrid kinematics, as alternative to existent laparoscopic surgical robots with serial or parallel structure. Keywords: Surgical Robot, Laparoscopic, Hybrid Kinematics, Virtual Modeling.

1. Introduction Before 1980, surgical procedures were performed through large incisions through which the surgeon directly accessed the area of interest. In the late 80s, image capture technologies have led to the development of laparoscopy, which uses one or more small incisions to insert instruments and a camera. It is characterized by reducing morbidity, patient trauma and hospitalization period. At the same time, increase the complexity of the task surgery - reduce visibility and can not be manually palpate the tissue. It also decreases the possibility of to orientate the surgical instrument. The next step was to create remote controlled robots to assist the surgeon, in order to increase he's performances. Zeus robot [1], [2] - figure 1, produced by Computer Motion's AESOP was the first commercial robot for laparoscopic interventions - 2001. The arms of the robot are remotely controlled via joysticks or master arms. Zeus filters the hand-shake and can scale the movement, reducing its amplitude. It was used in Lindbergh Operation, the first operation where the surgeon and the patient were separated by a distance of several thousand kilometers.

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Figure 1. Zeus robot. DaVinci robot [1], [2], [3] - fig. 2, the most popular surgical robot, manufactured by Intuitive Surgical Inc. is remotely controlled by surgeon from a console, the robot's arms following the doctor's hand movements, scaling movement and reducing tremor. The console is a 3D video display that takes 3D images from an endoscope.

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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics 2. Necessity of at least two arms: One arm is required for grasping / gripping and the other for cutting or sewing - figure 3. 3. Ensure a stereoscopic vision 4. Improving surgical gesture by scaling of motion and its stabilization to reduce tremor 5. Ensure operation patients in an ergonomic position that will reduce fatigue and hence it will improve the quality of surgery.

Figure 2. DaVinci robot. The da Vinci robot has three arms. One is able to manipulate the visualization system, which provides a three-dimensional image to the surgeon. The other two arms, using specific tools are able to move with 7 degrees of freedom, simulating the movements of the arm, shoulder and wrist. 2. Kinematic needs for the Robotized Laparoscopic Surgery

Figure 3. Vesico-urethral anastomosis performed with the daVinci robot.

In [3], Târcoveanu makes a concise and informed analysis on surgical approaches mentioned above: "Currently, robots provide surgeons the ability to perform gestures that they can not run with the instruments used in minimally invasive surgery. In terms of engineering, particularly interested in the mobility required for robotic arms: "Trocars in laparoscopic surgery instruments movements limited to 4 degrees of freedom. Robotic instruments through multiple joints, increase to 6 degrees of freedom (normal threedimensional movement)." The study conducted in a hospital in Naples / Italy [4] evaluates the advantages and limitations of robotic-assisted laparoscopy: "The main advantages of robotic-assisted laparoscopic surgery are threedimensional and easier manipulation tools than standard laparoscopy. The main limitations of the tool are large diameter (8 mm) and number of robotic arms (3). This led to the passage from classical surgery because bleeding is difficult to manage with only two instruments. The benefit to the patient should be carefully evaluated before the technology is widely used." A similar study was conducted by a team from the Department of Surgery of the College of Medicine and King Khalid University Hospital in Riyadh, Saudi Arabia [5]: "Robotic-assisted minimally invasive surgery is feasible, safe and may become the surgical procedure of the future." The above considerations, together with other documented sources [6], [7], [8], [9] lead to the next requirements: 1. Recovery of degrees of freedom of the joints within the abdomen or chest using special tools type Endowrist

Based on these goals, the remote controlled robot configuration was sketched; it should have at least three arms: - An arm carrying the vision system type endoscope with a diameter of 8 mm - Two arms carrying the surgical instruments inserted through trocars of 8-12 mm. This concept is still supported by some examples given below: 1. Robot for cardiovascular surgery [10], developed and tested by a joint team of engineers and surgeons at Fakultät für Informatik, Robotics and Embedded Systems, Technische Universität München, Germania, respectiv German Heart Center Munich, Clinic for Cardiovascular Surgery. In the Figure 4 it can be observed the 3 arms:

Figure 4. Surgical Remote controlled System: two instruments and a 3D video camera.

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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics 2. Zeus robot, mentioned above, has also three arms, remote controlled by joysticks or master arms. 3. The da Vinci robot has three arms too. One is able to manipulate the visualization system, which provides a adjustable magnification and three-dimensional image that is controlled by the surgeon. Two arms, using specific daVinci tools are able to move with 7 degrees of freedom, simulating the movements of the arm, shoulder and wrist. Another idea is that each carrier arm of surgical instrument requires at least six independent degrees of freedom, which provide three rotations and three translations also independent; this can be achieved with conventional serial structures or parallel structures Gough platforms - Stewart or hexapods. Figure 5 shows the use of a hexapod which provides the six independent degrees of freedom. It is a guided robotic system for surgical applications [11], developed at the School of Mechanical & Aerospace Engineering, Nanyang Technological University Singapore.

Actual operating capacity also depends on the size of trocars and the number of degrees of freedom of the surgical instruments. Changing the characteristic point coordinates, it is obtained the extended operating space - corresponding to the surgical instrument tip. In figure 6 is presented the operation mode of the proposed virtual surgical robot, named HyKiVi robot. Scissors trocar is designed to cut tissue and forceps / clamp trocar for manipulating tissue. The two arms carrying these trocars are placed on lateral sides, while the central arm is intended for the vision trocar.

Figure 6. Operation mode of the HyKi robot 4. Motion Simulation

Figure 5. HIFU effector mounted on a Neurobot 3. Hybrid Kinematics Approach For reasons of accuracy and stability, parallel kinematic structures of hexapod type are preferred. However, they have a drawback: small operating space. To eliminate this disadvantage, each arm will consist of two identical overlapping hexapods, resulting in a robotic system with hybrid kinematics, serialparallel. Furthermore, in order to simplify the control of a system with 12 actuators, it requires that the two hexapods will always have identical configurations, which reduces the number of degrees of freedom at 6, as well as the number of control parameters. To determine the operating space, there were considered two physical constraints: length legs, lower and upper limits and maximum allowed angles of the universal joints. In the application software used for simulation, these parameters can be easily modified in accordance with the actual mechanical components. A specific problem is that a point within the given space can be reached not only by one configuration of the robot, but with an infinite number of configurations, depending on the orientation of the upper platform. Orientation is considered a geometric constraint and can also be modified by the user.

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First tests were performed on a single hexapod in order to facilitate testing in the SolidWorks environment, because it runs easier if the virtual model has fewer components. In order to obtain the acting values for the 6 linear actuators, it was developed a LabVIEW application containing both the geometrical information regarding hexapod and the inverse kinematics [12]. The controls placed in the left side of the user interface - Figure 7 - allow modifying the sizes of the hexapod, to set the limits for the linear actuators displacements and to set the desired pose (3 translations and 3 rotations). If the green led is bright, the leg lengths do not exceed the actuators strokes.

Figure 7. LabVIEW application to compute the acting values

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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics Taken into account the motor stroke of 20 mm, the limit values for leg lengths introduced were: upper limit = 169.25 mm and lower limit = 149.25 mm. The leg lengths LP1, LP2, LP3, LP4, LP5, LP6 are the results provided by the program (for a better identify -

cation, they were colored distinctly on the chart). To move the virtual hexapod, the values obtained in LV application were used in Motion Study section from SolidWorks, as is shown in Figure 8:

Figure 8. Motion Study section used for one hexapod A tilt motion with 150 can be seen in Figure 8:

5. Control Device In the previous section it was described how input data are manually introduced in the simulation software. Actually, the surgical robot is a remote controlled one, thus it is necessary a device for the intuitive control of each arm. Because the terminal elements of the surgical robot have six degrees of freedom, it was designed a control device with six d.o.f. too, in fact a 6D joystick - Figure 11:

Figure 9. Upper platform tilt The next step was testing of the movement of a double hexapod, as described in the previous stages Figure 10. As it was already specified, this construction serves to increase the working space:

Figure 11. Motion study for a double hexapod

Figure 10. Motion study for a double hexapod

It is based on a hexapod structure too, with displacement sensors of LVDT type, which convert the motion of the surgeon hand in signals used to act the motors. By construction, the device assures the scaling of motion to improve the motion accuracy; the signals filtering is also possible, in order to reduce the tremor of surgeon hand.

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Virtual Modeling of a Laparoscopic Surgical Robot with Hybrid Kinematics 6. Conclusions The virtual model serves to create an image on the functionality of the robot, allows collision detection, workspace limits visualization since the design stage. After performing successive corrections, the improved model can be launched in execution, saving time and money in the case of possible design errors. This research was possible due to funding by NUCLEU National Research Program, Ctr. 5N/2009, project no. 09.05.04.01. 7. References [1]. Ryan A. Beasley - Medical Robots: Current Systems and Research Directions - Hindawi Publishing Corporation, Journal of Robotics, Volume 2012, Article ID 401613, 14 pages, doi:10.1155/2012/401613 [2]. S. Luncă, G. Bouras - Chirurgia robotică - Jurnalul de Chirurgie, Iasi, 2005, Vol. 1, Nr. 2 [ISSN 1584 – 9341] [3]. E. Târcoveanu - Chirurgia robotică [4]. Corcione F, Esposito C, Cuccurullo D, Settembre A, Miranda N, Amato F, Pirozzi F, Caiazzo P. Advantages and limits of robot-assisted laparoscopic surgery: preliminary experience - Department of Surgery and Laparoscopy, AORN Monadi Hospital, Via Monaldi 234, Naples, 80100, Italy.

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Abdulkarim A., Al[5] Khairy G. A., Fouda M., Saigh A., Al-Kattan K. - A new era in laparoscopic surgery: Evaluation of robot-assisted laparoscopic procedures - Department of Surgery, College of Medicine and King Khalid University Hospital, Riyadh, ARABIE SAOUDITE [6] A. Lobontiu, D. Loisance - Chirurgia Robotica : Viitor la prezent - 04.12.2006 / eMedic http://www.emedic.ro/Articole/15.htm [7] E. Târcoveanu, R. Moldovanu, C. Bradea Splenectomia laparoscopică – tehnică chirurgicală Jurnalul de Chirurgie, Iasi, 2007, Vol. 3, Nr. 3 [ISSN 1584 – 9341]. [8] Medical Robotic - Edited by Vanja Bozovic - 2008 [9] L. Eichel, R. Clayman - Fundamentals of Laparoscopic and Robotic Urologic Surgery [10] E. Braun, H. Mayer, A. Knoll, R. Lange, R. Bauernschmitt - "The Must-Have in Robotic Heart Surgery: Haptic Feedback" - Technische Universität München - Medical Robotics edited by Vanja Bozovic © 2008 I-Tech Education and Publishing www.itechonline.com [11] S. Chauhan - "Image Guided Robotic Systems for Focal Ultrasound Based Surgical Applications" - School of Mechanical & Aerospace Engineering, Nanyang Technological University Singapore [12] M. Mărgăritescu, A.M.E. Ivan, V. Văduva, C. Brişan - “Extended Mobility carried out with a Double Hexapod Robot” - „ROBOTICS 2010”, Cluj-Napoca, 23-25 septembrie 2010/ Solid State Phenomena Vols. 166-167 (2010) pp 271-276© (2010) Trans Tech Publications, Switzerland, ISSN: 1662-9779.

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