• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.117-126
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• 1994

This paper describes an application step of a $R^{-{\theta}}$ method which measures circular movements in machining centers. The detection of composite errors of circular movements and a high precision cutting method in machining centers were investigated by the analysis of data measured by $R^{\theta }$method which can detect the rotating angle and is applicable to variable measuring radius. When the error by squareness error and unbalance of position-loop-gain were mixed, the detection method of each error was proposed. Although the errors by squarenss error and backlash compensation were mixed, the errors by squareness error be detected. If the errors by unbalance of position-loop-gain and backlash compensation were mixed, the errors by unbalance of position-loop-gain could not detected. A high precision cutting mehod, which uses the NC program compensated by using feed-back data from error measured by the $R^{\theta }$method, was proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1828-1831
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• 2003

There are various sources causing a position error in a linear motor. This paper focuses on error sources from rotational motions of a table and friction. Rotational errors occur due to imperfections during manufacturing and/or assembly of guide ways, and cause a position error at locations of interest. Friction is another factor deteriorating the position error due to its highly nonlinear behavior. The position error of the linear motor was about 20∼30$\mu\textrm{m}$. After compensating the position errors due to rotational error motions and friction. the remaining errors become about 6～8$\mu\textrm{m}$ and 2～3$\mu\textrm{m}$, respectively. It is shown that the positional accuracy of a linear can be greatly improved by compensating the two error sources.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.270-273
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• 2003

The strain measurement of the panel in the sheet metal forming is essential work which provides experimental data needed to die design, process design, and product inspection. To measure efficiently the complex geometry strain, the 3-dimensional automative strain measurement system, which has high accuracy in theory, but has some 3∼5% errors in practice, is often used. The object of this study is to develop the error compensation technology to eliminate the strain, errors resulted when formed panels are measured using an automated strain measurement system. To achieve the study object, the position error calibration method correcting coordinates of the grid node recognized by a camera using error functions is suggested. Then the position errors were found by calculating the difference in the position of the cube node between real coordinates and measured coordinates in toms of node coordinates and the error calibration equations were derived by regressing the position errors. In order to show the validation of the suggested position error calibration method, finite element analysis and current calibration method was performed for the initial-blankformed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.672-675
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• 2000

There are many sources of errors in the parallel device. This study investigates the effect of a clearance error at a U-joint on the position and orientation errors of the platform of a new parallel device, cubic parallel manipulator. In this study, the limits of errors can be estimated for given conditions.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.64-71
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• 1997

Objective of calibration is to find out the accurate kinematic relationships between robot joint angles and the position of the end-effector by estimating accurate model parameters defining the kinematic function. Estimating the model parameters requires measurement of the end-effector position at a number of different robot configurations. This paper studies the implication of measurement configurations in robot calibration. For selecting appropriate measurement configurations in robot calibration, an index is defined to measure the observability of the model parameters with respect to a set of robot configurations. It is found that, as the observability index of the selected measurement configurations increase the attribution of the position errors to the parameter errors becomes dominant while the effects of the measurement and unmodeled errors are less significant; consequently better estimation of parameter errors is expected. To demonstrate the implication of the observability measure in robot calibration, computer simulations are performed and their results are discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.1010-1018
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• 2009

An inertial navigation system for pedestrian position tracking is proposed, where the position is computed using inertial sensors mounted on shoes. Inertial navigation system(INS) errors increase with time due to inertial sensor errors, and therefore it needs to reset errors frequently. During normal walking, there is an almost periodic zero velocity instance when a foot touches the floor. Using this fact, estimation errors are reduced and this method is called the zero velocity updating algorithm. When implementing this zero velocity updating algorithm, it is important to know when is the zero velocity interval. The gait states are modeled as a Markov process and each state is estimated using the hidden Markov model smoother. With this gait estimation, the zero or nearly zero velocity interval is more accurately estimated, which helps to reduce the position estimation error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.235-240
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• 1995

In order to eliminate position errors existing at the steady state in the motion control of robotic manipulators, a new fuzzy control algorithm is proposed using three variables, position error, velocity error and integral of position errors as input variables of the fuzzy controller. Three dimensional look-up table is used toreduce the computational time in real-time control, and a technique reducing the amount of necessary memory is introduced. Simulation and experimental studies show that the position errors at the steady state are decreased more than 90% compared to those of existing fuzzy controller when the proposed fuzzy controller is applied to the 2 axis direct drive SCARA robot manipulator.

• Journal of applied mathematics & informatics
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• v.11 no.1_2
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• pp.327-340
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• 2003

For motion analysis electromagnetic sensors are often used to measure positions and orientations of human subjects. It is observed from several experiments of the Ergonomics Research group that there exist systematic errors and unexpected serious distortions due to some metal masses in the test area. A calibration process is necessary to fix these errors. In this article three models are proposed to correct position measurement errors based on observations from calibration experiments.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1155-1160
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• 2007

This paper presents position error for the robot localization system using the ultrasonic wave. The distance between the receiver and a beacon can be computed by using the difference between times of flight. The distance information measured by ultrasonic wave has errors. The position is calculated by distances, and this error is caused by distance errors. The position error is different from receiver¡s position. And the position is also calculated by beacon location. This paper calculates worst case position error within measuring area, and finds beacons location to reduce the position error.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.17 no.2
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• pp.1-9
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• 2011

Background: Injury or pain in the neck can affect proprioception. People who have a reduced proprioception are easily exposed to induce injury or pain. The aim of this study was to examine the reduced proprioception among people who had lateral flexion postural habit of neck in a sitting position. Methods: Twenty subjects with lateral flexion postural habit were compared with a matched control group. Relocation errors in 30 degree rotation to the right were measured three times with and without visual information randomly. Results: Relocation errors were higher in the lateral flexion postural group than the control group with (p<.01) and without (p<.005) the visual information. Visual information didn't affect the cervical relocation errors in the abnormal and control groups. Repetition is increased the relocation errors with (p<.01) and without (p<.001) visual information. Conclusions: The results support the hypothesis that subjects with lateral flexion postural habit have incorrect perception of their head position. It is necessary to realize the possibility of injury or pain found among people with lateral flexion postural habit.