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Research Papers

Design and Prototyping of a Force-Reflecting Hand-Controller for Ultrasound Imaging

[+] Author and Article Information
Farshid Najafi

School of Engineering, Laurentian University, Sudbury, ON, P3E-2C6, Canadafnajafi@laurentian.ca

Nariman Sepehri1

Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, MB, R3T-5V6, Canadanariman@cc.umanitoba.ca

1

Corresponding author.

J. Mechanisms Robotics 3(2), 021002 (Mar 10, 2011) (11 pages) doi:10.1115/1.4003446 History: Received May 05, 2010; Revised January 06, 2011; Published March 10, 2011; Online March 10, 2011

This paper presents detailed design, analysis, prototyping, and testing of a novel force-reflecting hand-controller allowing physicians to control a robotic wrist and perform ultrasound examinations on patients in remote locations. The proposed device is a four degree-of-freedom mechanism with a fixed center-of-motion and uses symmetric parallel mechanisms. All movements of the device are kinematically decoupled, i.e., the hand-controller has independent drive systems for each standard ultrasound motion. A technique has been adapted to statically balance the weight of the device over its entire workspace using a single tension spring. The prototype of the device has been constructed and evaluated for ultrasound imaging of kidney and spleen. Maximum and accuracy of the output force are analytically determined and performance of the device in terms of static balancing, static-friction break-away force, and maximum achievable impedances are experimentally evaluated.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Free-hand ultrasound examination: (a) pitch scanning, (b) yaw scanning, and (c) rotational scanning

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Figure 2

Required movements of hand-controller for ultrasound imaging

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Figure 3

4DOF force-reflecting hand-controller: (a) general view of device and (b) power train of the third and fourth movements producing sliding and rotational motions of hand-grip. Each encoder can be replaced with an actuator-encoder if force feedback needed.

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Figure 4

Spherical 3DOF single-body mechanism balanced with one spring (27)

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Figure 5

Implementation of a zero-free-length tension spring using cable and spherical guide in close-up view

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Figure 6

Static balancing of mechanism: (a) four six-bar mechanisms located on two perpendicular planes with center of gravity moving on a sphere for all configurations and (b) center of gravity moves on a circle at different orientation of mechanism

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Figure 7

Static balancing of hand-controller with zero-free-length tension spring

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Figure 8

Possible configurations of 4DOF hand-controller: (a) four six-bar pantograph mechanisms, (b) asymmetric two six-bar pantograph mechanisms, (c) symmetric double-parallelograms, (d) asymmetric parallelograms, and (e) symmetric mechanism with no linkage

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Figure 9

Power train of third motion showing torques and angular positions

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Figure 10

Isovalue output force per unit motor torque (N/N mm) on user’s hand input torque

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Figure 11

Relative output force error of the hand-grip over the entire workspace

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Figure 12

Prototype of hand-controller with force-reflecting hand-grip

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Figure 13

Demonstration of static balancing of prototype device; device is moved arbitrarily and then released at about −18 deg and 20 deg orientation

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Figure 14

Experimental relation between control signal and measured output static force along axis of hand-grip

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Figure 15

Block diagram of bilateral servo system used for position control of wrist and force control of proposed device

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Figure 16

Static-friction break-away force along the axis of hand-grip

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Figure 17

Virtual wall simulation without inducing sustained oscillations: (a) for maximum achievable wall stiffness without damping 5 N/mm, (b) for maximum achievable wall damping without stiffness 0.1 N s/m, and (c) for maximum achievable wall stiffness and damping 5.6 N/mm and 0.06 N s/mm

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Figure 18

Remote ultrasound examination of kidney and spleen: (a) clinician manipulating hand-controller to capture ultrasound images, (b) remote robotic wrist is holding and moving the probe on a volunteer at remote side, and (c) ultrasound images of spleen and short axis view of kidney. The clinician brings the entire robotic wrist over the area of interest by a joystick (on the left). The proposed haptic device (on the right) is then used to manipulate the probe on the wrist.

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Figure 19

Universal joint kinematics

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