H. Yamashita, A. Iimura, E. Aoki, T. Suzuki, T. Nakazawa, E. Kobayashi, M. Hashizume, I. Sakuma, T. Dohi: DEVELOPMENT OF ENDOSCOPIC FORCEPS MANIPULATOR USING MULTI-SLIDER LINKAGE MECHANISMS, In Proceeding of The 1st Asian Symposium on Computer Aided Surgery - Robotic and Image guided Surgery - (Ibaraki, Japan, April 28, 2005), PO14, April 2005.
DEVELOPMENT OF ENDOSCOPIC FORCEPS MANIPULATOR USING MULTI-SLIDER LINKAGE MECHANISMS H. Yamashita 1, A. Iimura 2, E. Aoki 3, T. Suzuki 3, T. Nakazawa 2, E. Kobayashi 3, M. Hashizume 4, I. Sakuma 3 and T. Dohi 1 1
Graduate School of Information Science and Technology, The University of Tokyo, Tokyo, Japan 2 THK Co. LTD., Tokyo, Japan 3 Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan 4 Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
[email protected]
Abstract: This paper proposes an endoscopic forceps manipulator with 2-DOFs bending mechanism by multi-slider linkage mechanisms and 1-DOF wire-driven grasping mechanism. Careful design of the linkage channels and restoring springs enabled unique, independent and stable bending procedure from −90 to 90 degrees on the horizontal and vertical plane to secure large working space. The manipulator consisted of a multi-DOFs end-effector, three linear-drive units and a computer-based control unit. For the interface, various systems were available according to the application, such as a handheld-type and a master-slave-type. In mechanical performance analyses, 2-DOFs bending mechanism enabled high accuracy of less 1.0 degree manipulation and stable bending power of up to 0.85 kgf. In vivo experiments, this manipulator performed some laparoscopic surgical tasks, such as raising the liver and the stomach, suturing and ligation the cystic duct. In master-slave control evaluation, we confirmed a possibility of sophisticated operation for telesurgery. In conclusion we are sure of a usefulness of an endoscopic forceps manipulator for speedy and dexterous surgery.
rukawa Techno Materials, Furukawa NT Alloys) for rotational restoring springs was installed between frame2 and frame3. Harmonic driving procedure of linkages for drive and restraint enabled independent bending motion (Figure 1). 2-DOFs bending mechanism consisted of linearly connected two 1-DOF bending mechanisms with a phase difference of 90 degrees, one was for vertical bending and another is for horizontal bending (Figure 2). In order to merge two 1-DOF bending mechanisms for two directional independent manipulation, two-axes joint connected the linkage for drive in tip-side bending mechanism and three links toward the actuator, enabling two-axes rotation responding to the base-side bending angle (Figure 3). Constituent materials of 2-DOFs bending mechanism were all stainless steel, in which outer frames and joint-pin were SUS304, and two sets of linkages were SUS316 for less friction driving.
1 Introduction Endoscopic surgery enables minimal invasive surgery, however, inflexibility of surgical approaches and instruments manipulations cause surgeons' mental and physical stress. To overcome these issue on limited maneuverability, several robotized devices have been developed[1]-[4]. Our original solution in this paper is a new endoscopic forceps manipulator using multi-slider linkage mechanisms with high accuracy, stable power and large working space for effective clinical applications. 2 Materials and Methods 2.1 Multi-Slider Linkage Mechanism 1-DOF bending mechanism consisted of three cylindrical outer frames and two joints as a finger-like multi-joint structure. A set of linkages passed through careful designed channels and a super-elastic shaft (Fu-
Figure 1: 1-DOF bending mechanism with multi-slider linkage mechanism transforms linear motion of the linkage for drive rotation of frames. A super-elastic shaft in frames prevents frame1 from starting rotation before frame2 and frame3 in the bending procedure.
H. Yamashita, A. Iimura, E. Aoki, T. Suzuki, T. Nakazawa, E. Kobayashi, M. Hashizume, I. Sakuma, T. Dohi: DEVELOPMENT OF ENDOSCOPIC FORCEPS MANIPULATOR USING MULTI-SLIDER LINKAGE MECHANISMS, In Proceeding of The 1st Asian Symposium on Computer Aided Surgery - Robotic and Image guided Surgery - (Ibaraki, Japan, April 28, 2005), PO14, April 2005.
Figure 2: 2-DOFs bending mechanism that consists of five frames, two sets of linkages for drive and restraint. Each linkage slides through inner channels shown in sections (A), (B) and (C).
Figure 4: System configuration of a laparoscopic forceps manipulator.
Figure 5: Details of the linear-drive unit to drive 2-DOFs bending mechanism and 1-DOF grasping mechanism.
Figure 3: Effective action of the two-axes rotational joint enables various 2-DOFs bending approach with independent bending motions. 2.2 System Configuration The system configuration of the endoscopic forceps manipulator consisted of mainly four parts (Figure 4). First part was the multi-DOFs end-effector with 2-DOFs bending mechanism and 1-DOF grasping mechanism. Second part was the linear-drive unit consisted of three sets of brushless DC-servomotors (FAULHABER, 1628 024 B), linear sensors detecting linkage displacements (ALPS, RDC1014A09), linear-guides (THK, RSR3WNUU+36L +) and ball-screws (NSK, M3×0.5) (Figure 5). Third part was the dial-type interface with three spindle operated potentiometers (Meggitt Electronic Components, TYPE 51 SERIES) consisted of two dials for the horizontal and vertical bending, a trigger for grasping and a button for straightening the bending frames in getting through a trocar. Fourth part was the computer-based position feedback control unit consisted of a computer (CPU: Intel Pentium4 2.0 GHz., RAM: 512 MB, OS: Red Hat Linux 7.3) and three servo amplifiers (FAULHABER, BLD 3502) calculating displacements of sliding two linkages and one stainless-steel wire by inputted target angles (Figure 6, Table 1).
Figure 6: Position Feedback loop to control 3-DOFs of the manipulator. Table 1: Variables in feedback loop. θr θc xr xc ∆x V F(θr) G(∆x )
Input angle from dial-type interface 2-DOFs bending angle and 1-DOF grasping angle Target displacement of linkage Current displacement of linkage Difference displacement of linkage Output voltage to servo amplifier Function from Input angle to target displacement of linkage Function from difference displacement to output voltage
2.3 Linkage Connector Linkage connector enabled easy connection between the multi-DOFs end-effector and the linear-drive unit with minimum procedure (Figure 7). This mechanism was useful for cleaning and sterilization before, in and after surgical operation.
H. Yamashita, A. Iimura, E. Aoki, T. Suzuki, T. Nakazawa, E. Kobayashi, M. Hashizume, I. Sakuma, T. Dohi: DEVELOPMENT OF ENDOSCOPIC FORCEPS MANIPULATOR USING MULTI-SLIDER LINKAGE MECHANISMS, In Proceeding of The 1st Asian Symposium on Computer Aided Surgery - Robotic and Image guided Surgery - (Ibaraki, Japan, April 28, 2005), PO14, April 2005.
(B)
(C)
(D)
Figure 7: Connection procedure of the multi-DOFs end-effector and linear-drive unit. (A) Insertion of three attachment-pins on multi-DOFs end-effector side into three attachment-slots on linear-drive unit-case with a grip-base in one hand. (B) Twist and fit both parts along attachment-slots to end points. (C) Slide three locate-bases in the grip-base into three joint-arms in the linear-drive unit. (D) Locate-pins on locate-bases fit in holes of leaf-springs on joint-arms to complete the linkage connection. Table 2: Result of repeatability measurements. DOF Horizontal Horizontal Vertical Vertical Grasp
Direction Power [kgf] Torque [mNm] 0 to +90° 0.70 118.6 0 to –90° 0.85 144.1 0.40 165.7 0 to +90° 0 to –90° 0.50 207.1 Close 0.85 60.8
Table 3: Generated power and torque. Item Horizontal bending Vertical bending Repeatability ±0.87° ±0.91° Bending range from −84° to 77° from −85° to 80° Hysteresis error less 9.0° less 5.5° Error over the less 13.3° less 10.1° theoretical value 3 Results 3.1 Mechanical Performance We examined repeatability and response characteristics of 2-DOFs bending mechanism using digital video camera (Sony, DCR-PC110), and generated power at the tip of Multi-DOFs end-effector. Repeatability measurements were done unloaded with five trials, measuring actual bending angles against target angles (Table 2). Generated powers and torques around the rotational axes are shown in Table 3. Each power fulfilled 0.40 kgf of requested specification. As response characteristics we examined actual bending angle against target angle from the dial-type interface to evaluate delay times of 2-DOFs bending manipulation (Figure 8).
Delay Time [ms]
Delay Time [ms]
(A)
550 500 450 400 350 300 250 200 150 -100 700 600 500 400 300 200 100 0
–50 0 50 Input Bending Speed [deg/sec] (A)
100
-100
–50 0 50 100 Input Bending Speed [deg/sec] (B) Figure 8: Response characteristics of (A) the tip-side horizontal bending mechanism and (B) the base-side vertical bending mechanism. 200ms is an index value of delay in human perception [5].
(A)
(B)
(C) (D) Figure 9: (A) Circumventing and raising the liver tissue without transformation of elements of bending mechanism. (B) Grasping and exfoliating the surface tissue by the reverse side of internal organs is performed effectively. (C) Passing the manipulator's tip part through ablated cystic duct with horizontal swing motion to grasp and pull a thread. (D) Ligation of the cystic duct taking 26.9 ± 7.11 seconds on an average of seven times. 3.2 In vivo Experiments We did usability analyses of the forceps manipulator in near-clinical setting, having surgeons approach to around the liver on animals (swine, 42.5 kgf and 43 kgf, female) and do some surgical tasks (Figure 9).
H. Yamashita, A. Iimura, E. Aoki, T. Suzuki, T. Nakazawa, E. Kobayashi, M. Hashizume, I. Sakuma, T. Dohi: DEVELOPMENT OF ENDOSCOPIC FORCEPS MANIPULATOR USING MULTI-SLIDER LINKAGE MECHANISMS, In Proceeding of The 1st Asian Symposium on Computer Aided Surgery - Robotic and Image guided Surgery - (Ibaraki, Japan, April 28, 2005), PO14, April 2005.
Suspending device Control Computer Passive arms for positioning Forceps manipulator Laparoscope
Master-Controller
3D real-time positioning sensor
Figure 10: Overview of the master-slave manipulator system.
face, however, surgeons evaluated that they didn't feel noticeable delay in operation of the manipulator. For future works we feel the need to add some DOFs such as rotation and swing to the end-effector, and to minimize diameter of the manipulator for more precise and finer operation in various clinical applications. 5 Conclusions We are sure of the usefulness of newly developed endoscopic forceps manipulator with large working space, high repeatability and sufficient power for speedy and dexterous surgery. Acknowledgements A part of this work is supported by Research for the Future Program “Development of Surgical Robot”, administered by Japan Society for the Promotion of Science, Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists. References [1] DARIO P., et al. (2000): ‘A Novel Mechatronic Tool for Computer-Assisted Arthroscopy’, IEEE Trans. Inform. Technol. Biomed., 4(1) pp. 15-28
(A) (B) Figure 11: (A) Passive arms with forceps manipulators. (B) Mounted forceps manipulators on the master-slave system. 3.3 Master-Slave Control Evaluation The operating interface of the forceps manipulator was selectable from local system such as a handheld-type to remote system such as a master-slave-type. We evaluated the manipulator mounted in the master-slave manipulator system developed by BMPE Lab. and NML Lab., The University of Tokyo [6][7] (Figure 10, Figure 11). Intuitive manipulation for sophisticated endoscopic surgery needed some trainings, however, we confirmed our manipulator was effective on master-slave system for telesurgery. 4 Discussion Bending powers up to 0.85 kgf were sufficient for raising and holding the liver and the stomach. High repeatability of less 1.0 degree and high grasping power up to 0.85 kgf was effective to grasp a thin thread and a needle in suturing and ligation in animal experiments. Response characteristics varied through bending DOFs, directions and input bending speed from dial-type inter-
[2] NAKAMURA R., et al. (2000): ‘Multi-DOF Forceps Manipulator System for Laparoscopic Surgery Mechanism miniaturized & Evaluation of New Interface -’, Proc. 4th International Conference on Medical Image Computing and Computer-Assisted Intervention. 2000, pp. 606-613 [3] PEIRS J., et al. (2001): ‘A miniature manipulator for integration in a self-propelling endoscope’, Sensors and Actuators A, pp. 343-349 [4] IKUTA K., et al. (2002): ‘Remote Microsurgery System for Deep and Narrow Space - Development of New Surgical Procedure and Miciro-robotic Tool’, Proc. 5th International Conference on Medical Image Computing and Computer-Assisted Intervention. 2002, pp. 163-172 [5] BATE L., et al. (2001): ‘The Feasibility of Force Control Over the Internet’, Proc. the 2001 Australian Conference on Robotics and Automation. 2001, pp. 146-151 [6] SUZUKI T., et al. (2004): ‘Development of master-slave robotic system for laparoscopic surgery’, Proc. of ICMA2004, 2004, pp. 35-40 [7] MITSUISHI M., et al. (2003): ‘Development of Remote Minimally-Invasive Surgical System with Operational Environment Transmission Capability’, Proc. of IEEE/ICRA2003, 2003, pp. 2663-2670
