• Current Optics and Photonics
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• v.5 no.4
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• pp.362-369
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• 2021

Absolute position sensors are widely used in machine tools and precision measuring instruments because measurement errors are not accumulated, and position measurements can be performed without initialization. The laser speckle-based absolute position sensor, in particular, has advantages in terms of simple system configuration and high measurement accuracy. Unlike traditional absolute position sensors, it does not require an expensive physical length scale; instead, it uses a laser speckle image database to measure a moving surface position. However, there is a problem that a huge database is required to store information in all positions on the surface. Conversely, reducing the size of the database also decreases the accuracy of position measurements. Therefore, in this paper, we propose a new method to measure the surface position with high precision while reducing the size of the database. We use image stitching and approximation methods to reduce database size and speed up measurements. The absolute position error of the proposed method was about 0.27 ± 0.18 ㎛, and the average measurement time was 25 ms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.363-364
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.358-362
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• 2002

The HDD unbalance, with higher rotational speed, is directly influenced by the mechanical assembly allowance between clamping disk and platter disk. The low frequency structural vibration induced by the unbalance force finally gives rise to the structure borne noise of the personal computer. To meet the noise and vibration requirements, the absolute unbalance mass of HDD needs to be measured and adjusted in the disk assembling stage. This study introduces the measurement methods of the absolute magnitude and position of the unbalance mass of HDD based on the mobility and acceleration orbit. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass ran be obtained by the rotation acceleration orbit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.340.1-340
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• 2002

The unbalance exciting force induced by HDD of lately getting higher speed is directly influenced by the rotational speed and the mechanical assembly allowance between disk and spindle motor, and which gives rise to the structure borne noise of the personal computer. The absolute unbalance mass of HDD needs to be measured and adjusted by the counter mass to control the unbalance exciting force effectively in the stage of assembling the disk and spindle motor. This study introduces the measurement methods of the magnitude of the absolute unbalance mass and the position of HDD by 2 accelerometers. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass can e obtained by the rotation acceleration orbit.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.163-170
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• 2004

Since 1960s, a container shipping volume has increased dramatically and continuous on a trend of rapid growth, and so the number of containers handled at the port increases. The position measurement of the yard crane is very important for improving the operating efficiency of the port. This paper describes the method to measure the absolute position of yard crane accurately and rapidly, using both the output pulse of an encoder and infrared sensors. The crane position is calculated by counting the output pulse of an incremental encoder, which is mounted on the wheel in the crane. By the way, the wheel slippage on rail may cause some errors in the crane position information obtained from encoder pulse, and the infrared sensor is used to compensate for errors in the crane position information. The performance of proposed method is verified on experimental results with the simulator of yard crane, the size of which is about 1/10 with the real crane.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.25-26
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• 2006

The method measuring the absolute position of a point diffraction source emitting a spherical wavefront in three-dimension is proposed. Two-dimensional interference of spherical wavefronts is used to overcome ambiguity of phase order. The spherical wavefront is explicated by Taylor series expansion, from which a radius of curvature of a spherical wavefront and its center position in three-dimension are obtainable. The spherical wavefront is reconstructed by a modified lateral shearing interferometer, which uses single-mode fiber as a point diffraction source.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.45-54
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• 2007

In the context of auto-landing containers from a container ship to a truck or automatic guided vehicle and vice versa, this research investigates three schemes, one in Part I and two in Part II, for measuring the absolute position of a container. Coordinate transformations between the reference-coordinate, sensor-coordinate, and body-coordinate systems are briefly discussed. The scheme explored in Part I aims the use of three laser-slit sensors, which are relatively inexpensive. In this case, nine nonlinear equations are formulated for six unknown variables (three for orientation and three for position), so a closed-form solution is not available. Instead, an approximate solution through linearization was derived. An advantage of the method in Part I is its ability to measure an absolute position in 3D space, while a disadvantage is the computation time required to obtain pseudo-inverses and the approximate nature of the obtained solution. Numerical examples are provided.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.775-781
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• 2011

For the measurement of absolute position of mobile robot in indoor environments, the ultrasonic positioning systems using ultrasound have been researched for several years. Most of these ultrasonic positioning systems to avoid interference between the ultrasound are used for sequential transmitting. However, due to the use of sequential transmitting, the positions of transmitter to receive an ultrasound will change when the mobile robot moves. Therefore the accuracy of positioning is reduced. In this paper, the new position estimation algorithm with weighting factor according to the time of receipt is proposed. By applying the proposed algorithm to existing Ultrasonic Satellite System(USAT), the improved USAT is configured. The positioning performance of the improved USAT with the proposed position estimation algorithm are verified by experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.9
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• pp.856-860
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• 2006

A CCD camera is used to determine the position of the point sources that influence the measurement accuracy in the absolute interferometer. The principle of determination method is based on the GPS in which the position is determined by more than 3 distance information from the known positions. Two-dimensional array of photo-detectors in the CCD camera is used as known positions. Performing optimization of the cost function constructed with phase values measured at each pixel on the CCD camera, the position coordinates of each source is precisely determined.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1343-1348
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• 1990

The architecture and functions of a prototype free ranging AGV system are described in this paper. The system has single tricycle configuration - the front wheel is driven and steered simultaneously. The primary position measurement device of this system is the redundant encoder system - an absolute encoder for the steering angle measurement of the front wheel, two incremental encoders for the measurement of the rear wheel rotations. The secondary position measurement device is implemented to reduce the accumulatad error in encoder measurements. The extended Kalman filter is suggested to combine the conflict measurement data for the proper position estimation.