Multi-Fingered Haptic Interface Robot Handling Plural Tool Devices
Haruhisa KAWASAKI * Tetsuya MOURI * Sho IKENOHATA *
Yoshio OHTSUKA * Takahiro ENDO *
(*)Gifu University, Japan
E-mail: h_kawasa@gifu-u.ac.jp, mouri@gifu-u.ac.jp
Abstract
Tool-type haptic interfaces such as scissors are used to present force feeling for surgical training in virtual reality environment. Presentation of force feelings of plural tools needs to prepare many single tool-type haptic interfaces. This paper proposes newly conceptual idea for plural tool-type haptic interfaces. The proposed system consists of single tool-type haptic devices and a multi-fingered haptic interface. The system has a greater potential for the force feelings of plural tool devices than does a single tool-type interface in the view of work space, removable equipment, force control, small dimensions, and simple tool-type device. Tool-type devices, which are scissors, injector, and knife, are developed to present reactive feeling. Experimental results of cutting simulation are shown to demonstrate the effectiveness of proposed system.
1. Introduction
Haptic interfaces that present force and tactile feeling have been utilized in the area of medical training and evaluation. In case of application for surgical training, medical doctor needs many surgical
tools. Many researchers have been developed single tool-type haptic interfaces, which are scissors, surgical knife, injector, and so on, to use some objective task [1-6]. However, presentation of force feelings of multi surgical tools requires many single tool-type haptic interfaces. Providing many single tool-type haptic interfaces requires installation location and costs a great deal. Moreover, bulk of single tool-type haptic devices is not at liberty to displace because of fixing on a base.
A multi-fingered haptic interface has greater potential for various applications than a single point haptic interface. Several multi-fingered haptic interfaces [7-15] have so far been developed. Our developed haptic interface consisting of an arm and fingers can be used in wide area. Work space of the haptic interface is close to that of human at the table. Therefore, the multi-fingered haptic interface is applied to presentation of force feeling of plural surgical devices.
This paper presents newly conceptual idea for incorporating multi-fingered haptic interface in presentation of force feelings of plural tool devices. Surgical tool devices, which are scissors, injector, and knife, are developed for virtual operation training. Experimental results of cutting sheet using developed
scissors device are shown.
Fig. 1. Concept of plural surgical tool devices presentation
2. Handling plural tool devices
2.1 Conceptual idea
Plural tool-type devices require: each tool-type devices to be easy to put on and take off, dimensions are small and they are operated in widely work space.
These requirements are fulfilled by equipping the multi-fingered haptic interface called HIRO II with tool-type devices. Figure 1 shows the concept for presenting force feelings of plural tools. Multi-fingered haptic interface are equipped with exchangeable surgical tool-type devices. The proposed haptic system has advantages as follows. (1) Each of tool-type devices is very simple because they are improved on actual devices. (2) It is easy to exchange the plural tool-type devices using permanent magnet at fingertips.
(3) It saves occupied space for the haptic system. (4) Tool-type devices can be translated in wide area. (5) Force and position can be measured and controlled by multi-fingered haptic interface.
The proposed system has greater potential for the force feelings of plural tool devices than does a single tool-type interface.
2.2 Multi-fingered haptic interface robot HIRO II
The authors developed five-fingered haptic interface consisting of an arm and fingertips haptic display shown in Fig. 2, which is called HIRO II. The HIRO II is placed opposite to the human hand, which brings safety and no oppressive feeling and makes a wide workspace. Details of the haptic interface have been shown in [15]. The outline of its mechanism is described briefly for better understanding the proposed system.
The HIRO II can present force and tactile feeling at the five fingertips of the human hand. It is designed to be completely safe and similar to the human upper limb both in shape and motion ability. Its mechanism consists of a 6 DOF interface arm and a 15 DOF haptic hand with 5 fingers. The motion ranges from the 1st to the 6th joints of the interface arm are -180 ~ 180, 0 ~ 180, -90 ~ 55, -180 ~ 180, -55 ~ 55, and -90 ~ 90 [deg], respectively. In the fingers, the motion ranges from the 1st to the 3rd joints of fingers are -30 ~ 30, -25 ~ 94, and -10 ~ 114 [deg], respectively. The motion ranges from the 1st to the 2nd joints of the thumb are -40 ~ 40 and -25 ~ 103 [deg]. In order to read the finger loading, a 6-axes force sensor in the second link of each finger is installed. To manipulate the haptic interface, the user has to wear a finger holder on his/her fingertips. Finger holder has a sphere, which attached to the permanent magnet at the force sensor tip, forms a passive spherical joint. Its role is the adjustment of differences between the human and haptic fingers orientations.
2.3 Prototype tool devices
In operative treatment, elementary operations are amputating, pinching, chopping, injecting and so on. Scissors, injector, and knife tool-type devices are developed in Fig. 3. The figure shows the tool-type devices equipping the HIRO II. The developed devices are refined upon commercially available surgical tools. Spherical joints are attached at the supporting point and working point. A fictional resistance is reduced to become smaller as much as possible. The devices are equipped with the HIRO II in consideration of
Fig. 2. Multi-fingered haptic interface robot
HIRO II (a) Scissors
(b) Injector
(c) Knife
Fig. 3. Developed tool-type devices
alignment of the spherical joints and posture of haptic fingers
3. Cutting simulation
This paper focuses on the scissors tool-type devices, which are many variations as surgical tools. Using the scissors devices it is easy to express various surgical scissors by changing knife blade of scissors in virtual reality (VR) space. This section introduces the scissors tool-type device, control method and cutting simulation system.
3.1 Scissors device
Developed scissors tool-type device is shown in Fig. 4. Weight is 0.0070 kg. Three spherical joints are attached at one supporting point and two working points. As a result of analyzing the work space of the devices, it is attached fingers, which are thumb, index finger, and ring finger, shown in Fig. 5.
3.2 Calculation of reactive feeling on cutting sheet
A method for cutting sheets has been proposed in Ref. [4]. This paper uses the method as follows.
()(){}()s s s T T E d K E d R ψσωγσ2211+??=,
()tan θ=S T , r n S E E E =
(1) where R T is resistance stress, σ is the distance from
supporting point to working point, ψ is the distance from supporting point to grip of scissors, K is coefficient of stiffness, θ is opening and closing angle, d is spacing between blades, γ is coefficient of viscosity, ω is angular velocity of rotational motion around supporting point, E n is limited extension ratio, and E r is extension ratio.
Figure 6 shows the feature of the VR simulation. The operator cuts on the virtual sheet by virtual scissors with reactive feeling. However, this paper excludes presenting force feeling cutting by translational motion.
3.3 Control method for tool devices
Authors propose the control methods for the HIRO
II [14, 15]. The control methods are classified broadly into two categories for haptic arm. One is based on the position control in which a position and orientation of the robot hand is determined so as to maximize a manipulability of the robot hand. The other is based on the force control. Note that five fingers are controlled by the force control. This paper selects the force control based on torque control for haptic arm and
fingers, because the position of haptic fingers is constrained by scissors devices.
A control input of the haptic interface by the redundant force control is given by
()∫
+??+?=q q
F F J K F F J K τg K dt d T d T &321)()(, (2) where 15),(R T T hand T arm ∈=τττ
is a joint torque vector whose sub vectors are an arm joint torque vector
6R arm ∈τ
and a hand joint torque vector T
T
ring T
index T
thumb hand ),,(ττττ= 9R ∈, 915×∈R J is the
kinematic Jacobian, 9),,(R T T ring T index T thumb ∈=F F F F is a
force vector whose sub vectors are a force vector at finger tip, F d is a desired force vector, K 1 is a force feedback gain matrix, and K 2 is a force integral feedback gain matrix. Each finger joints is controlled to follow the desired force independently. The arm joint is controlled practically to follow desired force and moment at hand bases, which are generated by the desired finger forces. In this control, a finger that
Scissors device
HIRO II
Supporting point
Working point
Fig. 5. HIRO equipping scissors device
578873
47
11
5
°
67.°45Fig. 4. Parameters for scissors tool
VR scissors
sheet
Fig. 6. VR simulation
reaches the limit of the movable range is switched to a position control to keep the joint angle in the movable range, and the rest of fingers are controlled by the redundant force control. After reaching the limit of the movable range, the finger that has been switched to the position control is switched back again to the redundant control when the direction of the joint torque input is the same direction of that of the joint angle apart from the limit of the movable angle.
Humans stabilize the orientation of the scissors attaching the finger to the supporting point. Therefore, the desired force of the supporting point, which is equipped with ring finger, is set at zero. To simplify discussions, we assume that same forces act on both blades. The desired forces of thumb and index finger are calculated by R T and the principle of leverage.
4. Experiment
This section demonstrates an effectiveness of the developed haptic system. The experimental system of plural surgical tool devices is shown in Fig. 7. The system consists of PC-based real-time control system and VR simulation system. Both control system and VR Simulation system operate with a 1 ms sampling time. VR simulation system is connected to HIRO II control system with Giga-bit Ethernet [16]. Control system sends fingertip positions and forces to VR simulation system. VR simulation system sends desired forces to the control system. VR simulation system calculates the reactive feeling using fingertip positions.
4.1 Resistance force for translation motion
When the operator uses HIRO II equipped with the scissors device, the mechanical friction of HIRO II is a resistance force for translation motion. Therefore, the resistance force for straight motion along x, y, z axis, and opening and closing motion are examined. Figure 8 shows the result of developed scissors device. The average of the resistance force along x, y, and z axis are 0.22 N, 0.20 N, and 0.22 N, respectively. The resistance force increases 2 times compared to using fingers stand-alone. However, the resistance force is less than weight of scissors device. Operation feeling is not artificial but rather natural.
4.2 Cutting sheets
Equipping HIRO II with scissors tool-type device displays the force felling for the cutting sheet. Figure 9 shows the desired and actual torque at the fingertip point and opening and closing angle. The figure illustrates several examples of changing stiffness and viscosity parameters. Reactive filling increases gradually with decreasing of opening and closing angle. An average of error between desired and actual torques is 0.03 Nm.
Experimental results successfully show presenting force feeling depending on characteristic of sheets as mentioned above. However, the error of the force is large to use surgical trainings. The control method will be improved in the future.
5. Conclusion
This paper has proposed newly conceptual idea for surgical training. Plural tool devices have been attached to the multi-fingered haptic interface. The proposed system has had a greater potential for the force feelings of plural tool devices than a single tool-type interface. The scissors, injector, and knife tool-type devices have been developed. Specification of the scissors tool-type device has been shown. Simulations of cutting sheet with the developed scissors device have been demonstrated for the effectiveness of the proposed system.
HIRO II
The future works will improve the precision of force feeling and apply the proposed system to surgical training, evaluation and so on. The developed injector and knife tool-type devices will be evaluated. Acknowledgment
The authors would like to express their thanks to the members of haptic interface research project of the Gifu University.
References
[1] A. M. Okamura, R. J. Webster III, J. T. Nolin, K. W.
Johnson, and H. Jafry, “The Haptic Scissors: Cutting in Virtual Environments”, Proceedings of the 2003 IEEE
International Conference on Robotics and Automation,
pp828-833, 2003
[2]S. Greenish, V. Hayward, V. Chial, A. Okamura, and T.
Steffen, “Measurement, Analysis, and Display of Haptic
Signals During Surgical Cutting”, Presence, Vol.11,
No.6, pp.626–651, 2002
[3]H. Wakamatsu and S. Honma, “Teleoperational Force
Display System in Manipulation of Virtual Object Using
Various Types of Cutting Devices”, Sixth International
Conference on Methods and Models in Automation and
Robotics, pp. 631-636, 2000
[4]S. Honma and H. Wakamatsu, “Cutting Moment
Analysis of Materials by the Saw for Force Display
System”, Transaction of the Virtual Reality Society of
Japan, Vol.9, No.3, pp.319-326, 2004 (in Japanese)
[5]R. J. Webster III, J. Memisevic, and A. M. Okamura,
“Design Considerations for Robotic Needle Steering”,
Proceedings of the 2005 IEEE International Conference
on Robotics and Automation, pp. 3599-3605, 2005
[6] C. S. Tzafestas, D. Christopoulos, and K. Birbas,
“Haptic display improves training and skill assessment
performance in a virtual paracentesis simulator: A pilot
evaluation study,” Proceedings of Euro Haptics, 2006 [7]H. Kawasaki and T. Hayashi, “Force feedback glove
for manipulation of Virtual Objects,” Journal of
Robotics and Mechatronics, vol. 5, no.1, pp. 79-84,
1993
[8]Y. Ueda and T. Maeno, “Development of a mouse-
shaped haptic device with multiple finger inputs,”
Proceedings of International Conference on Intelligent
Robots and Systems, pp. 2886-2891, 2004
[9]S. Walairacht, M. Ishii, Y. Koike, and M. Sato, “Two-
handed multi-fingers string-based haptic interface
device,” IEICE Transaction on Information and Systems,
vol. E84D, No. 3, pp. 365-373, 2001
[10]M. Bouzit, G. Burdea, G. Popescu, and R. Boian, “ The
rutgers master II – new design force-feed back glove,”
IEEE/ASME Transaction on Mechatronics, vol. 7, no. 2,
pp.256-263, 2002
[11]Y. Adachi, T. Kumano, A. Ikemoto, A. Hattori and N.
Suzuki, “Development of a haptic device for multi
fingers by Macro-Micro Structure,” Journal of the
Robotics Society of Japan, vol. 20, no. 7, pp. 725-733,
2002 (in Japanese)
[12]T. Yoshikawa and A. Nagara, “Development and control
of touch and force display devices for haptic interface,”
Proceedings of SYROCO’00, pp. 427-432, 2000
[13]Immersion Corporation, “CyberForce,” url:
https://www.doczj.com/doc/0316380829.html,/3d/products/cyber_force.ph
p
[14]H. Kawasaki, J. Takai, Y. Tanaka, C. Mrad, and T.
Mouri, “Control of multi-fingered haptic interface
(a) Straight motion along x axis
(b) Straight motion along y axis
(c) Straight motion along z axis
(d) Opening and closing motion
Fig. 8. Resistance force of translation in free
motion
opposite to human hand,” Proceedings of the 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems , Las Vegas, pp. 2707-2712, 2003 [15] H. Kawasaki, T. Mouri, M. Osama Alhalabi, Y.
Sugihashi, Y. Ohtuka, S. Ikenohata, K. Kigaku, V. Daniulaitis, K. Hamada and T. Suzuki, “Development of Five-Fingered Haptic Intereface: HIRO II”, Proceedings of ICAT 2005, pp. 209-214, 2005
[16] M. O. Alhalabi, V. Daniulaitis, H. Kawasaki, T. Mouri,
Y. Ohtuka, and K. Ishida, “Future Haptic Science Encyclopedia: An Experimental Implementation of Networked Multi-Threaded Haptic Visual Environment,” 14th Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems , pp. 507-513, 2006
5560
0.0
0.10.2
T o r q u e [N m ]
Time [sec]
(1) Torque
0.8
1.01.21.4
A n g l e [r a d ]
Time [sec]
(2) Opening and closing angle
(a) K =8.0x104, E s =3.5
50
5560
0.00.1
0.2
T o r q u e [N m ]
Time [sec]
(1) Torque
50
5560
0.81.01.2
1.4
A n g l e [r a d ]
Time [sec]
(2) Opening and closing angle
(b) K =8.0x104, E s =4.0
45
5055
0.00.1
0.2
T o r q u e [N m ]
Time [sec]
(1) Torque
45
5055
0.81.01.21.4
A n g l e [r a d ]
Time [sec]
(2) Opening and closing angle
(c) K =8.0x104, E s =5.0
0.00.1
0.2
T o r q u e [N m ]
Time [sec]
(1) Torque
0.81.01.2
1.4
A n g l e [r a d ]
Time [sec]
(2) Opening and closing angle
(d) K =4.0x104
, E s =4.0
0.00.1
0.2
T o r q u e [N m ]
Time [sec]
(1) Torque
0.81.01.21.4
A n g l e [r a d ]
Time [sec]
(2) Opening and closing angle (e) K =16.0x104, E s =4.0
Fig. 9. Presenting torque and angle of scissors