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. 2009 Dec 1;9(12):1864-1871.
doi: 10.1109/JSEN.2009.2030980.

Compact Sensing Design of a Handheld Active Tremor Compensation Instrument

Win Tun Latt  1 , U-Xuan Tan, Cheng Yap Shee, Cameron N Riviere, Wei Tech Ang
Affiliations

Compact Sensing Design of a Handheld Active Tremor Compensation Instrument

Win Tun Latt et al. IEEE Sens J. .

Abstract

Active physiological tremor compensation instruments have been under research and development recently. The sensing unit of the instruments provides information on three degrees-of-freedom (DOF) motion of the instrument tip using accelerations provided by accelerometers placed inside the instruments. A complete vector of angular acceleration of the instrument needs to be known to obtain information on three DOF motions of the tip. Sensing resolution of angular acceleration about the instrument axis is directly proportional to the width of the proximal-end sensing unit. To keep the sensing resolution high enough, the width of the unit has to be made large. As a result, the proximal-end sensing unit of the instruments is bulky. In this paper, placement of accelerometers is proposed such that the angular acceleration about the instrument axis need not be known to obtain information on the three DOF motions of the tip. With the proposed placement, the instrument is no longer bulky and fewer number of accelerometers is required, thereby making the instrument compact and better in terms of ergonomics and reliability. Experiments were conducted to show that the proposed design of placement works properly.

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Figures

Fig. 1
Fig. 1
Micron instrument sensing unit: (a) a photo and (b) a schematic diagram of placement of accelerometers and a frame {B} attached to the instrument.
Fig. 2
Fig. 2
Illustration of the locations which have the same acceleration component in a particular axis direction (assuming angular velocity is small enough to be neglected).
Fig. 3
Fig. 3
Theoretical placement of accelerometers to get a complete acceleration vector at the top without requiring angular motion information.
Fig. 4
Fig. 4
Placement of an accelerometer to sense acceleration component at the tip along ZB axis direction.
Fig. 5
Fig. 5
Placement of two accelerometers which require only two angular motion information to (αy and αy) obtain acceleration components in XB axis and YB axis directions.
Fig. 6
Fig. 6
Placement of accelerometers to get a complete acceleration vector at the tip.
Fig. 7
Fig. 7
Illustration of error in positioning of accelerometers.
Fig. 8
Fig. 8
Photo of the accelerometers inside the ITrem instrument without the actuators and mechanism at the distal end.
Fig. 9
Fig. 9
Comparison of the sizes of the instruments.
Fig. 10
Fig. 10
A photo of (a) the ITrem instrument attached to the rotating arm and (b) close-up view of the instrument tip placed near to the workspace of M2S2.
Fig. 11
Fig. 11
Comparison of ground truth angular acceleration about YB axis and calculated angular acceleration about YB axis using acceleration outputs from accelerometers inside the instrument.
Fig. 12
Fig. 12
A photo taken while tremor motion of the ball was being measured using M2S2, as well as accelerometers inside the ITrem to evaluate the ITrem sensing.
Fig. 13
Fig. 13
Plots of comparison of position calculated from ITrem and that measured from M2S2.
See this image and copyright information in PMC

References

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