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Research Paper

High Sensitive Force Sensing Based on the Optical Fiber Coupling Loss

[+] Author and Article Information
Muthukumaran Packirisamy

e-mail: pmuthu@alcor.concordia.ca

Javad Dargahi

Optical-Bio Microsystems Laboratory,
Department of Mechanical and Industrial Engineering,
Concordia University,
Montreal, QC, H3G 2W1, Canada

1Corresponding author.

Manuscript received October 27, 2011; final manuscript received November 20, 2012; published online February 4, 2013. Assoc. Editor: Just L. Herder.

J. Med. Devices 7(1), 011001 (Feb 04, 2013) (8 pages) Paper No: MED-11-1096; doi: 10.1115/1.4023264 History: Received October 27, 2011; Revised November 20, 2012

In the present paper, an innovative miniaturized optical force sensor is introduced for use in medical devices such as minimally invasive robotic-surgery instruments. The sensing principle of the sensor relies on light transmission in optical fibers. Although the sensor is designed for use in surgical systems, it can be used in various other applications due to its novel features. The novelty of the sensor lies in offering four features in a single miniaturized package using a simple optical-based sensing principle. These four features are the high accuracy/resolution, the magnetic resonance compatibility, the electrical passivity, and the absence of drift in the measurement of continuous static force. The proposed sensor was micromachined using microsystems technology and tested. The sensor measures 18 mm, 4 mm, and 1 mm in length, width, and thickness, respectively. The sensor was calibrated and its performance under both static and dynamic loading conditions was investigated. The experimental test results demonstrate a 0.00–2.00 N force range with an rms error of approximately 2% of the force range. Its resolution is 0.02 N. The characteristics of the sensor such as its size, its measurement range, and its sensitivity are also easily tunable.

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References

Figures

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Fig. 1

The structure of the force sensor in different views: (a) front view; (b) top view in which the beam is transparent for better visualization; (c) 3D view in which the beam is translucent for better visualization. The sensor consists of a silicon beam with fixed-fixed boundary conditions, four supports, and a substrate. The supports are fixed on the substrate of the sensor. The sensor substrate provides a rigid base.

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Fig. 2

The photograph of the sensor: (a) the lower surface of the sensor beam, which includes two integrated optical fibers leading into the v-groove; (b) the whole structure of the assembled sensor

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Fig. 3

The SEM image of the integrated optical fibers into the micromachined v-grooves: (a) the top view of the lower surface of the sensor beam; (b) the flat and cleaved surface of one of the fibers inside the v-groove

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Fig. 4

The sensor during the tests with (a) concentrated force, and (b) the artificial tissue

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Fig. 5

The diagram of the experimental setup

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Fig. 6

The alternative design in which the optical fibers are introduced to the sensor from one direction using micro-mirrors in the sensor beam

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Fig. 7

The photograph of the experimental setup. The light source pumps light into sensor's optical fiber. Using WinTest software, the test instrument applies controlled force/displacement to the sensor. This force alters the light intensity on the sensor's fiber. The photodetector converts the light intensity to the voltage. The output voltage of the photodetector is processed on LabVIEW.

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Fig. 8

The ratio between the output voltage of the sensor and the input force before applying the calibration algorithm to the output signal. The solid line shows the sensor output for a loading/unloading cycle. The dashed line depicts the fitted trend-line.

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Fig. 9

The dynamic response of the sensor: comparing the input force and the measured force for a linear chirp force from 0 to 5 Hz

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Fig. 10

The performance of the sensor to measure static loads: comparing the input force and the measured force for a square function between 0.1 N to 1.0 N with the frequency of 0.02 Hz

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Fig. 11

Input force versus measured force for a square function with linear amplitude increments

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Fig. 12

(a) Input force versus measured force to evaluate the resolution of the sensor. (b) The magnified graph, which shows that the noise level of the prototyped sensor is lower than the reference commercial force sensor.

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Fig. 13

Input force against measured force for a triangle force with 1 Hz frequency

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