Design and Principle Analysis for Electromagnetic Brake

Clamping Mechanism of a Novel Slave Manipulator

Linshuai Zhang*1,*4 Shuxiang Guo*2,*3, Huadong Yu*4, Yu Song*1

*1Graduate School of Engineering, Kagawa University,

Takamatsu, Kagawa, Japan

*2 Key Laboratory of Convergence Medical Engineering

System and Healthcare Technology, The Ministry of Industry

and Information Technology, School of Life Science and

Technology, Beijing Institute of Technology, Haidian District,

Beijing 100081, China

*3Department of Intelligent Mechanical Systems Engineering,

Kagawa University, Takamatsu, Kagawa 761-0396, Japan

*4 School of Mechatronical Engineering,

Changchun University of Science and Technology,

Changchun, Jilin, China

s16d502@stu.kagawa-u.ac.jp guo@eng.kagawa-u.ac.jp

yuhuadong@cust.edu.cn

Abstract - Robotically assisted catheterization has attracted significant interest in recent years. However, few designs have taken the reasonable control of the clamping force into consideration. Additionally, limited research has been conducted in the damage of the clamping mechanism to the catheter. This paper presents a novel clamping mechanism for a slave manipulator that can be used in the minimally invasive surgery training system. The clamping mechanism utilizes the electromagnetic force which generated by the electrified coil to balance the pressure provided by the compression spring. Also the clamping force can be adjusted by the input current to prevent excessive clamping or inadequate clamping for the catheter. In addition, the modal analysis of the designed clamping structure is carried out. The results show that the modal frequency of the clamping structure is very small, so it does not resonate with the external excitation when the catheter is pushed forward. This clamping mechanism provides important insights into the design of compact and ergonomic robotic catheter manipulators incorporating effective and lossless clamping for intraoperative navigation. Index Terms - Electromagnetic force, Lossless clamping mechanism, Slave manipulator, Clamping force，Modal analysis

I. INTRODUCTION

Cardiovascular and cerebrovascular diseases have become one of the three major causes of death in human beings, which is a serious threat to human health. Even in the developed countries, cardiovascular disease remains the major cause of mortality, accounting for 34% of deaths each year [1]. Vascular diseases are mainly vascular tumor, thrombosis, vascular malformations, vascular contraction, vascular sclerosis, etc. And vascular interventional surgery (VIS) is the most effective treatment for cardiovascular and cerebrovascular diseases [2]. However, compared with the

"open" operation, VIS has small incisions, high safety, quicker recovery, less complications and other advantages. So it has been widely adopted all over the world [3,4].However, there are some problems in traditional vascular interventional surgery. First, the vascular intervention surgery needs to be carried out under the guidance of medical imaging equipment, surgeons have long been affected by the radiation of X light, causing damage to the surgeon's body [5,6].Followed is the lack of the surgeon, long training time and high cost[7]. Because of the high risk of surgery, the requirements of operation skill for a surgeon must be a high level of specialized one to perform. Once again, the security of the surgery will be reduced due to the surgeon’s fatigue, physiological tremors and misoperation during fatigue. In order to solve these problems, an efficiency tele-surgery system should be adopted, which can assist the surgeon to operate the catheter interventional from a safe space[8].The physiological tremor of surgeon and misoperation can be filtered out through the system, increasing the safety of surgery [9].

In recent years, the medical and surgical robot system has become a hot study topic, and most of the systems contain master and slave manipulator currently used in medical surgery. Among these medical robots, vascular interventional robot has become a promising technology [10-13]. Many research teams around the world focus on the study of robotic catheter operation systems for vascular interventional surgery. Yogesh Thakur et al. [14] developed a novel remote catheter navigation system to reduce physical stress and irradiation to the interventionalist during fluoroscopic X-ray guided catheter intervention. And the results of two experiments showed that the system had the ability to sense and replicate motion to within 1 mm and 1° in the axial and radial directions, respectively. A teleoperation master-slave minimally invasive

vascular interventional surgical robot was designed. It has good maneuverability and can transmit the surgeon’s skill to insert and rotate the catheter under the teleoperation [15]. Also the dynamic and static performance of the system and synchronization between master and slave side were evaluated [16]. Moreover, the clamping force evaluation for the robotic catheter navigation system was conducted [17]. Guo et al. [18,19] designed a novel master-slave robotic catheter system with true force feedback to the surgeon’s hands. Fu et al. [20] proposed a master-slave catheterization system which including a steerable catheter with positioning function and an insertion mechanism with force feedback. The design concept of human operator-centered haptic interface was firstly introduced. A semi-active haptic interface was designed and fabricated through taking full advantage of MR fluids [21-23]. A new compact and sterilizable telerobotic system with three degrees of freedom was proposed, which allowed the interventionalist to use conventional steerable catheters [24]. In order to simulate the vascular deformation more vividly, Wang et al. introduced standard linear solid model to formulate its physical model and determine this model’s parameters based on vascular wall elasticity analysis [25,26]. Zhou et al. [27] described the cardiovascular interventional surgery (CIS) virtual training platform which was composed of a mechanical manipulation unit, a simulation platform and a user interface. The tests of translation and rotation showed that the accuracies improved by 50% and 32.5%. Compared to traditional catheter interventional method, these systems can provide advantages such as improving stability and comfort, reducing radiation exposure to the surgeon and eliminating physiological tremor. However, these systems generally have such disadvantage that the clamping force of the slave side is not adjustable. When the clamping force is insufficient, catheter and clamping structure will slide in relative position so that catheter cannot quickly reach the designated position. When the clamping force is too large, it will cause the catheter variant or even damage so as to hinder the guide wire insertion.

In this paper, a novel design about the clamping structure of the slave manipulator is proposed. The clamping structure of three jaws is designed to realize the clamping and relaxation of the catheter based on electromagnetic brake clamping mechanism. The design is a lossless clamping mechanism which uses the conical clamping principle to complete clamping. It has big clamping contact area and reliable clamping which can reduce the clamping injury of catheter. It can control the clamping force by adjusting the input current. And the clamping mechanism has the advantages of fast response and reliable performance. What's more, the designed clamping structure has carried on the modal analysis which is of great significance to increase the stability of the clamping structure and the safety of the surgery.

II. DESIGN REQUIREMENTS OF A NOVEL SLAVE MANIPULATOR

A conceptual diagram of the master-slave robotic catheter system is shown in Fig.1. It describes the design

Fig.1 A conceptual diagram of the master-slave robotic catheter system

requirements of a novel slave manipulator. To protect the surgeon from the radiation of X-ray, the surgeon can tele-operate the VIS in a secure area on master side. The operating information is acquired and transmitted to the slave side. Once receiving the operating information, the slave manipulator drives the catheter to insert into blood vessel. Motions of the catheter on the slave side follow the motions of the catheter on the master side. Of course, it is necessary to make the information of rotating position signal, moving position signal and contract force signal feedback to the master manipulator from the slave manipulator. However, a slave manipulator wants to be good to carry out the action commands from master manipulator, such as clamping, relaxation, forward, backward and rotation, which is necessary to based on a good design of clamping mechanism. And in the next section, the good design of clamping mechanism will be described in details.

III. STRUCTURE DESIGN OF CATHETER CLAMPING MECHANISM

For the clamping of catheter, the clamping force of existing clamping mechanism is easy insufficient or excessive clamping, and cause the catheter cannot be fully clamped or be damaged because of excessive clamping force. Base on such defects to design a lossless clamping mechanism which uses the conical clamping principle to complete clamping. Also the clamping force can be controlled by electromagnetic force. In this section, the designed clamping device will be introduced in details.

A. Composition of Clamping Mechanism The composition of the electromagnetic break clamping

mechanism is shown in Fig.2. It describes the coordination between the various parts in the electromagnetic brake clamping mechanism. The specific coordination relations are as follows: the compression spring will be fitted on the collet rod, and then they will be nested inside the sleeve, so that the

collet can be pressed by the compression spring inside the sleeve to clamp catheter. The bracket with coil will be sited outside the sleeve, which is used to generate electromagnetic force. The iron corn will be used to press the spring and wrap the coil with coil case. The design is a lossless clamping mechanism which has large clamping contact area and reliable clamping, so that it can reduce the clamping injury of catheter.

Fig.2 Structure diagram of the electromagnetic break clamping mechanism

B. Principle Analysis for Clamping Structure The principle diagram of electromagnetic brake clamping

mechanism is shown as Fig.3. It is a normally closed mechanism. When the coil is not energized, the compression spring will press the collet into the taper hole of the sleeve, so that the collet will be tightened up to clamp the catheter. Then the catheter can do the movement of forward, backward and rotation with the slave manipulator. However, when the coil is energized, the coil will generate the electromagnetic force, so that the collet will overcome the pressing force of the compression spring to move in the direction of iron corn, thus the collet will be relaxed to make the catheter release. After that, we can carry out the compensation of the catheter when the slave manipulator goes back at the same time.

In addition, we can design a lock switching mechanism which will cooperate with the electromagnetic clamping mechanism to complete the feed compensation of the catheter. The diagram is shown in Fig.4. When catheter is clamped, the whole structure will do the forward movement, and then the

Fig.3 The schematic diagram of clamping principle

Fig.4 The diagram of the catheter feed compensation

grasper of the lock switching mechanism will clamp the catheter, meanwhile, the collet of the electromagnetic clamping mechanism will release the catheter. After that, the body of the slave manipulator does the backward movement, then the collet clamps the catheter and the grasper of the lock switching mechanism releases the catheter. Afterwards, the whole structure can do the prior feed motion repeatedly.

C. Relationship between electromagnetic force and current The electromagnetic brake clamping mechanism adopts

the electromagnet of screw pipe type to drive [28]. According to the requirements of collet moving distance and electromagnetic force, we select the electromagnet structure of flat check seat shell type as the design model. The basic principle of the structure is shown in Fig.5. When taking l=z=0.4h, according to the electromagnetic force formula presented by Zhang et al. [28],

( )6

2

2222 10

74.0

5.231.0 ×

++=

δδ

d

ddBF (1)

Where F is the electromagnetic force, and B is the magnetic flux density, and d, δ, l and z are the diameter of iron core, the stroke of iron core, and the diameter of coil outer, the length of the iron core inside the coil, respectively. According to Ampere's law, Zhang et al. [28] put forward the magnetic potential formula as follows,

61074.0

×+

=δ

δd

dBIN (2)

Where I is the current through the coil, and N is turn number of the coil. By transformation we can get,

6-1074.0 ×+=

δδ

d

dINB (3)

We take the formula (3) into the formula (1). Then the relationship between the electromagnetic force and the current can be obtained as follows,

6-2

2222 10

5.231.0 ×+=

δδd

NIF (4)

When N, d and δ are fixed, the electromagnetic force F will change with the change of the current I through the coil. And then the clamping force of the catheter can be adjusted by the current through the coil so as to ensure the stability and security of the clamping.

Fig.5 The schematic diagram of electromagnet structure compensation

IV. ELECTROMAGNETIC BRAKE CLAMPING MECHANISM

A. Modal Analysis of Clamping Structure The ANSYS software is used to carry out the modal analysis for the clamping structure. The frequency of the first six mode-shapes is shown in Table I. The first six order mode-shapes of the clamping structure are shown in Fig.7. From the frequency in Table I and the first six order mode-shapes in Fig.7 we can know that the first and second order modal frequencies are small, and the mode-shapes are all transverse tensile deformation of the clamping structure. The frequency of the third order mode-shape is 28.176 Hz, and the mode-shape is the upward bending deformation of the rear end of the catheter. The frequency of the forth order mode-shape is 28.314 Hz, and the mode-shape is the downward bending deformation of the rear end of the catheter. The frequency of the fifth order mode-shape is 84.125 Hz, and the mode-shape is the upward bending deformation of the front end of the catheter. The frequency of the sixth order mode-shape is 85.259 Hz, and the mode-shape is the downward bending deformation of the front end of the catheter. Because the modal frequency of the clamping structure is very small, the drive motor will inevitably resonate with the clamping structure in a very short period of time only when it has just started. The frequency of the driving motor is much greater than the modal frequency of the clamping structure when the catheter is pushed forward. Therefore, the clamping structure and the external excitation can't be caused to resonate.

TABLE I THE FREQUENCY OF THE FIRST SIX MODE-SHAPES Vibration

type 1 2 3 4 5 6

Frequency/Hz 0.56388 0.56549 28.176 28.314 84.125 85.259

(a) The first order mode-shape

(b) The second order mode-shape

(c) The third order mode-shape

(d) The forth order mode-shape

(e) The fifth order mode-shape

(f) The sixth order mode-shape

Fig.6 The first six order mode-shapes of the clamping structure

B. Application of Clamping Device As shown in Fig.7, graph (a) and graph (b) describe the

front view and the isometric view of the slave manipulator with the application of the electromagnetic break clamping mechanism, respectively. The body of the slave manipulator is composed of three parts. One part is the rotation driving mechanism, which is used to make the catheter rotate under being clamped. And the torque also will be measured by the torque sensor which is installed in the rotation driving mechanism. One another part is electromagnetic clamping mechanism. It is used for clamping the catheter and then the catheter will do the movement of forward, backward and rotation with the slave manipulator. The other part is the force feedback mechanism, which is adopted to measure the haptic force between the catheter and the blood vessel.

The application of the electromagnetic brake clamping mechanism in the slave manipulator can improve the response and stability of clamping. Because it adopts the cooperation of electromagnetic force and spring to control the clamping of the catheter, and the response of electromagnetic force is very fast. Also the clamping mechanism uses a collet which has big clamping contact area to clamp the catheter, and then the clamping of the catheter will be stable, so that the clamping injury of catheter can be reduced.

(a) The front view of slave manipulator

(b) The isometric view of slave manipulator

Fig.7 The application of the clamping device in slave manipulator

V. CONCLUSION AND FUTURE WORK In this paper, an electromagnetic brake clamping

mechanism for a novel slave manipulator of robot-assisted catheterization system is proposed. It offers a fast response and lossless clamping mechanism which has big clamping contact area and reliable clamping to reduce the clamping injury of catheter. And the clamping force can be controlled by adjusting the input current. Also the modal analysis of the clamping structure is carried out, and the modal frequency of the clamping structure is much smaller than the frequency of the driving motor when the catheter is pushed forward. Therefore, the electromagnetic brake clamping mechanism presented is of great significance for improving the safety of the surgery.

In the future work, some experimental tests for the whole system will be conducted for contributing to development of high intelligence and high precision robot-assisted catheterization system.

ACKNOWLEDGMENT

This research is partly supported by National Natural Science Foundation of China (61375094), Key Project of Scientific and Technological Support of Tianjin(15ZCZDSY00910), National High Tech. Research and Development Program of China (No.2015AA043202), and SPS KAKENHI Grant Number 15K2120.

REFERENCES

[1] D. Lloyd-Jones, R. Adams, T. Brown, et al. “Executive summary: heart disease and stroke statistics-2010 update: a report from the American Heart Association,” Circulation, vol.121, pp.948-954, 2010.

[2] J. Guo, L. Shao, S. Guo, Y. Yu, Q. Gao. “A Multidimensional Information Monitoring Method for a Novel Robotic Vascular Interventional System.” Proceedings of the 2015 IEEE International Conference on Information and Automation, pp.32-37, Lijiang, China, August 2015.

[3] Y. Fu, A. Gao, H. Liu K. Li, Z. Liang. “Development of a novel robotic catheter system for endovascular minimally invasive surgery.” Proceedings of IEEE/ICME international conference on complex medical engineering, pp. 400-405, Harbin, China, May 2011.

[4] J. Guo, S. Guo, T. Tamiya, H. Hirata, H. Ishihara. “A virtual reality-based method of decreasing transmission time of visual feedback for a teleoperative robotic catheter operating system,” The International of Medical Robotics and Computer Assisted Surgery, vol.12, no.1, pp.32-45, March 2016.

[5] K. Kim, D. Miller, G. Berrington, S. Balter, R. Kleinerman, E. Ostroumova, S. Simon, M. Linet. “Occupational radiation doess to operators performing fluoroscopically-guided procedures,” Health Physics, vol.103, no.1, pp.80-99, 2012.

[6] A. Mohapatra, R. Greenberg, T. Mastracci, M. Eagleton, B. Thornsberry.“Radiation exposure to operating room personnel and patients during endovascular procedures,” Journal of Vascular Surgery, vol.58, no.3, pp.702-709, 2013.

[7] P. Zhang, S. Yu, Y. Hu, X. Ma, J. Zhang. “Design of a novel master-slaverobotic system for minimally intravascular invasive surgery,” Proceedings of the 2011 IEEE International Conference on Mechatronics and Automation, pp. 259-264, August 7-10, Beijing, China, 2011.

[8] J. Guo, S. Guo, T. Tamiya, H. Hirata, H. Ishihara. “Design and performance evaluation of a master controller for endovascular catheterization, ” International Journal of Computer Assisted Radiology and Surgery, in press.

[9] B. Liu, X. Bai, C. Meng, S. Lv, F. Zhou. “Image-guided navigation system for robot-based vessel intervention surgery based on conventional single

plane C-arm,” Procedia Environmental Sciences, vol.8, pp.276-283, 2011. [10] W. Lu, D. Wang, D. Liu, Z. Tian, B. Gao, L. Zhang. “Regarding

application of robotic telemanipulation system in vascular interventional surgery,” Journal of Vascular Surgery, vol.57, no.5, pp.1452-1453, 2013.

[11] Y. Wang, S. Guo, X. Yin. “Laser Mouse-based Master-Slave Catheter Operating System for Minimally Invasive Surgery, ” Proceedings of the 2015 IEEE Internaional Conference on Mechatronics and Automation, pp.871-875, August 2-5, Beijing, China, 2015.

[12] N. Xiao, J. Guo, S. Guo, T. Tamiya. “A robotic catheter system with real-time force feedback and monitor, ” Journal of Australasian Physical and Engineering Sciences in Medicine, vol.35, no.3, pp.283-289, 2012.

[13] S. Guo, P. Wang, J. Guo, W. Wei, Y. Ji, Y. Wang. “A Novel Master-slave Robotic Catheter System for Vascular Interventional Surgery, ” Proceedings of the 2013 IEEE International Conference on Mechatronics and Automation, pp.951-956, August 4-7, Takamatsu, Japan, 2013.

[14] T. Yogesh, S. Jeffrey, W. David, D. Maria. “Design and Performance Evaluation of a Remote Catheter Navigation System,” IEEE transactions on biomedical engineering,vol.56, no.7, pp.1901-1908, July 2009.

[15] J. Guo, S. Guo, N. Xiao, X. Ma, S. Yoshida, T. Tamiya, M. Kawanishi. “A novel robotic catheter system with force and visual feedback for vascular interventional surgery,” International Journal of Mechatronics and Automation, vol.2,no.1,pp. 15-24,2012.

[16] X. Ma, S. Guo, N. Xiao, S. Yoshida, T. Tamiya. “Evaluating performance of a novel developed robotic catheter manipulating system,” Journal of Micro-Bio Robotics, vol.8, no.3, pp.133-143, 2013.

[17] N. Xiao, L. Shi, B. Gao, S. Guo, T. Tamiya. “Clamping Force Evaluation For A Robotic Catheter Navigation System,” Neuroscience and Biomedical Engineering, vol.1, no.2, pp.141-145, 2013.

[18] J. Guo, S. Guo, L. Shao, P. Wang, Q. Gao. “Design and performance evaluation of a novel robotic catheter system for vascular interventional surgery,” Microsystem Technologies, in press.

[19] J. Guo, P. Wang, S. Guo, L. Shao, Y. Wang. “Feedback Force Evaluation for a Novel Robotic Catheter Navigation System, ” Proceedings of the 2014 IEEE International Conference on Mechatronics and Automation, pp.303-308, August 3-6, Tianjin, China, 2014.

[20] Y. Fu, A. Gao, H. Liu, S. Guo. “The master-slave catheterization system for positioning the steerable catheter,” International Journal of Mechatronics and Automation, vol.1, no. 3-4, pp.143-152, 2011.

[21] X. Yin, S. Guo, H. Hirata, H. Ishihara. “Design and experimental evaluation of teleoperated haptic robot-assisted catheter operating system,” Journal of Intelligent Material Systems and Structures, vol.27, no.1, pp.3–16, 2014.

[22] X. Yin, S. Guo, N. Xiao, T. Tamiya. “Safety Operation Consciousness Realization of a MR Fluids-based Novel Haptic Interface for Teleoperated Catheter Minimally Invasive Neuro Surgery,” IEEE/ASME Transactions on Mechatronics, vol.21, no.2, pp.1043-1054, 2015.

[23] X. Yin, S. Guo, Y. Wang. “Force Model-based Haptic Master Console Design for Teleoperated Minimally Invasive Surgery Application, ” Proceedings of the 2015 IEEE International Conference on Mechatronics and Automation, pp.749-754, August 2-5, Beijing, China, 2015.

[24] M. Tavallaei, D. Gelman, M. Lavdas, A. Skanes, D. Jones, J. Bax, M. Drangova. “Design, development and evaluation of a compact telerobotic catheter navigation system,” The International Journal of Medical Robotics and Computer Assisted Surgery,vol.3, pp.1-11, 2015.

[25] Y. Wang, S. Guo, T. Tamiya, H. Hirata, H. Ishihara. “A Blood Vessel Deformation Model Based Virtual-reality Simulator for the Robotic Catheter Operating System,” Neuroscience and Biomedical Engineering, vol. 2, no.3, pp.126-131, 2015.

[26] Y. Wang, S. Guo, B. Gao. “Vascular elasticity determined mass-spring model for virtual reality simulators,” International Journal of Mechatronics and Automation, vol.5, no.1, pp.1-10, 2015.

[27] C. Zhou, L. Xie, X. Shen, M. Luo, Z. Wu, L. Gu. “Cardiovascular-interventional-surgery virtual training platform and its preliminary evaluation,” The International Journal of Medical Robotics and Computer Assisted Surgery, vol.11, pp.375-387, 2015.

[28] G. Zhang, J. Lu. “Electromagnet and automatic electromagnetic element,” Beijing: Machinery Industry Press,1982.