Handling light disturbances in a Micro Motion Sensing System and investigation of the system performance
ABSTRACT The authors had previously developed a system to assess accuracy of micromanipulation tasks. The system includes an optical Micro Motion Sensing System (M2S2). The M2S2, consisting of a pair of orthogonally placed position sensitive detectors (PSD) and an infra-red (IR) diode, tracks 3D displacement of the tip of a microsurgical instrument in real-time. The IR diode is used to illuminate the workspace. A ball is attached to the tip of an intraocular shaft to reflect IR rays onto the PSDs. Instrument tip position is then calculated from the centroid position of the light falling on the PSDs. The system did not account for the effect of different ambient and environment light conditions. The system required that ambient light and environment light had to be maintained the same as those existing during calibration of the system. In some situations, they cannot be maintained the same and hence system accuracy is affected. This paper presents a method to make the system accuracy invariant to different ambient light and environment light conditions. The accuracies of the system at different orientations of the instrument are also reported.
SourceAvailable from: U-Xuan Tan[Show abstract] [Hide abstract]
ABSTRACT: High sensing resolution is required in sensing of surgical instrument motion in micromanipulation tasks. Accelerometers can be employed to sense physiological motion of the instrument during micromanipulation. Various configurations of accelerometer placement had been introduced in the past to sense motion of a rigid-body such as a surgical instrument. Placement (location and orientation) of accelerometers fixed in the instrument plays a significant role in achieving high sensing resolution. However, there is no literature or work on the effect of placement of accelerometers on sensing resolution. In this paper, an approach of placement of accelerometers within an available space to obtain highest possible sensing resolution in sensing of rigid-body motion in micromanipulation tasks is proposed. Superiority of the proposed placement approach is shown in sensing of a microsurgical instrument angular motion by comparing sensing resolutions achieved as a result of employing the configuration following the proposed approach and the existing configurations. Apart from achieving high sensing resolution, and design simplicity, the proposed placement approach also provides flexibility in placing accelerometers; hence it is especially useful in applications with limited available space to mount accelerometers.Sensors and Actuators A Physical 06/2011; 167(2):304-316. DOI:10.1016/j.sna.2011.03.001 · 1.94 Impact Factor
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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.IEEE Sensors Journal 01/2010; DOI:10.1109/JSEN.2009.2030980 · 1.85 Impact Factor
Conference Paper: A Compact Hand-held Active Physiological Tremor Compensation Instrument[Show abstract] [Hide abstract]
ABSTRACT: This paper presents research, design, and development of a compact version of a hand-held active physiological tremor compensation instrument called ldquoITremrdquo. The instrument comprises three main portions: sensing, filtering, and manipulation. Accelerometers are employed to sense three degrees-of-freedom motion of the instrument tool tip. Minimal-phase filtering is performed to extract tremulous motion of the tip from its total motion. As for manipulation, piezoelectric actuators and flexure based mechanism are employed to move the tool tip to an opposite direction but an equal in magnitude of the tremulous motion. The performance of the instrument was evaluated using a micro motion sensing system (M<sup>2</sup>S<sup>2</sup>). The preliminary results of bench tests as well as hand-held tests are shown.Advanced Intelligent Mechatronics, 2009. AIM 2009. IEEE/ASME International Conference on; 08/2009