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Research Paper

Design of an Experimental Set-Up to Study the Behavior of a Flexible Surgical Instrument Inside an Endoscope

[+] Author and Article Information
Jitendra P. Khatait

Mechanical Automation and Mechatronics,
Faculty of Engineering Technology,
University of Twente,
7500 AE Enschede, The Netherlands
e-mail: j.p.khatait@utwente.nl

Dannis M. Brouwer

Mechanical Automation and Mechatronics,
Faculty of Engineering Technology,
University of Twente,
7500 AE Enschede, The Netherlands;
Demcon Advanced Mechatronics,
7521 PH Enschede, The Netherlands

Herman M. J. R. Soemers

Philips Innovation Services,
5656 AE Eindhoven, The Netherlands

Just L. Herder

Mechanical Automation and Mechatronics,
Faculty of Engineering Technology,
University of Twente,
7500 AE Enschede, The Netherlands

1Corresponding author.

Manuscript received May 29, 2012; final manuscript received April 11, 2013; published online July 3, 2013. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 7(3), 031004 (Jul 03, 2013) (12 pages) Paper No: MED-12-1076; doi: 10.1115/1.4024660 History: Received May 29, 2012; Revised April 11, 2013

The success of flexible instruments in surgery requires high motion and force fidelity and controllability of the tip. However, the friction and the limited stiffness of such instruments limit the motion and force transmission of the instrument. In a previous study, we developed a flexible multibody model of a surgical instrument inside an endoscope in order to study the effect of the friction, bending and rotational stiffness of the instrument and clearance on the motion hysteresis and the force transmission. In this paper, we present the design and evaluation of an experimental setup for the validation of the flexible multibody model and the characterization of the instruments. A modular design was conceived based on three key functionalities: the actuation from the proximal end, the displacement measurement of the distal end, and the measurement of the interaction force. The exactly constrained actuation module achieves independent translation and rotation of the proximal end. The axial displacement and the rotation of the distal end are measured contactless via a specifically designed air bearing guided cam through laser displacement sensors. The errors in the static measurement are 15 μm in translation and 0.15 deg in rotation. Six 1-DOF load cell modules using flexures measure the interaction forces and moments with an error of 0.8% and 2.5%, respectively. The achieved specifications allow for the measurement of the characteristic behavior of the instrument inside a curved rigid tube and the validation of the flexible multibody model.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Endoscope with surgical instrument [6]

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Fig. 2

Schematic drawing of the experimental setup

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Fig. 3

Conceptual design of the coupling for the ball screw and slide guide using a folded sheet flexure and a bellow flexure. The stiff directions are shown by the dashed arrows. The compliant directions are shown by the solid arrows.

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Fig. 4

Conceptual design of the AM. The translation and rotation axis is connected via a flexure coupling. The two actuated DOFs are shown by the arrows.

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Fig. 5

Conceptual design of an exactly constrained configuration of the FSM using six wire flexures

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Fig. 6

Conceptual design of a 1-DOF load cell module consisting of a wire flexure, a 1-DOF load cell, and a preloading mechanism for overload protection

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Fig. 7

Conceptual design of the FSM with six 1-DOF load cell modules. The six load cell modules are attached to the base fixed plate. The top floating plate will be attached to the ends of six wire flexures.

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Fig. 8

Conceptual design of the cam. The angular displacement of the cam can be measured from the displacement measurement of the LDS.

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Fig. 9

CAD drawing of the cam

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Fig. 10

Conceptual design of the T3M

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Fig. 11

Experimental setup

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Fig. 12

The AM and the T3M were directly connected for the design evaluation

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Fig. 13

Static error measurement of the LDS1 and LDS2

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Fig. 14

Output voltage from the LDS1 for the translation measurement of the cam

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Fig. 15

Output voltage from the LDS2 for continuous rotation of the cam

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Fig. 16

Residual plot of the LDS measurement for rotation after a linear fit

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Fig. 17

Residual plot of the LDS measurement for rotation after subtracting the filtered data corresponding to the cam profile

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Fig. 18

Output displacement measured by the LDS1 compared with the input displacement measured from the encoder, showing the gear backlash in translation

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Fig. 19

Output displacement measured by the LDS2 compared with the input displacement measured from the encoder, showing the gear backlash in rotation

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Fig. 20

Loading configuration showing the external load applied on the top floating plate of the FSM at point P; Fext includes the external forces and moments

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Fig. 21

Output voltage of the load cells for the forces acting along the load cells

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Fig. 22

Relative error in the force and moment measurement

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