• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1995.10b
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• pp.211-217
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• 1995

Conventional linear control fails to provide precise positioning of a control object under the influence of friction, deadzone, saturation, etc. This paper proposes a high-precision control scheme for a precise point-to-point positioning system, called an X-Y table, even under the same influences above. The proposed scheme is composed of a fuzzy precompensator and a PD controller. The fuzzy precompensator is employed to improve the performance of the PD controller. Its fuzzy rules are obtained from experimental evolutionary programming (EP), not from an expert. The effectiveness of the scheme is demonstrated by experiments on the X-Y table. with a positioning error of within 1$\mu\textrm{m}$.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.285-290
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• 2006

This paper presents an adaptive neural network based controller and its application to Dynamic Positioning (DP) control system of ship. The proposed neural network based controller is developed for station-keeping and low-speed maneuvering control of ship. At first, the DP system configuration is described. And then, to validate the proposed DP system, computer simulations of station-keeping and low-speed maneuvering performance of a multi-purpose supply ship are presented under the influence of measurement noise, external disturbances such as sea current, wave, and wind. The simulations have shown the feasibility of the DP system in various maneuvering situations.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1045-1049
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• 1996

For the precision positioning and tracking control, the proper friction compensation is essential. The friction causes steady state error. The friction compensation based on the velocity and the controlling input or the desired velocity provides limited performance if the compensation value is fixed. In this paper, a friction compensation scheme using a fuzzy logic is proposed. The friction compensation amount is adjusted depending on the velocity and controlling input. The proposed fuzzy friction compensator with a pole-assignment controller is implemented in a linear positioning system. To illustrate the effectiveness of this scheme, computer simulations and experiments are carried out for the cases of no friction compensation, the proposed fuzzy friction compensation, and another friction compensation scheme based on velocity and control input, and the results are compared with each other.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.375-378
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• 2005

Voice Coil Motor is used linear motion actuator system that require precision positioning control. In order to control precision positioning of voice coil motor, Mathematical model of voice coil motor is needed. Mathematical model is obtained by combining voice coil motor's equation of motion with the equation of circuit and characteristic of voice coil motor. The induced model can predict output displacement according to duty ratio and amplitude. The model is verified by experimental test. Simulated results have tracking errors of less than 10 percent of experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.348-352
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• 2002

a basis such as IT(Information Technology), NT(Nano Technology) and BT(Bio Technology). Recently, NT is applied to various fields that are composed of science, industry, media and semiconductor-micro technology. It has need of IT that is ultra-precision positioning technology with strokes of many hundreds mm and maintenance of nm precision in fields of ultra micro process, ultra precision measurement, photo communication part and photo magnetic memory. This thesis represents optimal design on ultra-precision positioning with single plane X-Y stage and development of artificial control system for adequacy of industrial demand. Also, dynamic simulation on global stage is performed by using ADAMS (Automated Dynamic Analysis of Mechanical System) for the purpose of grasping dynamic characteristic on user designed X-Y global stage. The error between displacements from micro stage and from FEM(Finite Element Method) is 3.53% by verifications of stability on micro stage and control performance. As maximum Von-mises stress on hinge of micro stage is 5.981kg/mm$^2$ that is 1.5% of yield stress, stability on hinge is secured. Preparing previous results, optimal design of micro stage can be possible, and reliance of results with FEM can be secured.

• Journal of the Semiconductor & Display Technology
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• v.5 no.4 s.17
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• pp.1-4
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• 2006

Recently, with rapid development of digital media like semiconductor and large flat panel display, the manufacturing equipment is required to have high precision over large travel range. Moreover it should have high product throughput. To achieve high product throughput, a controller should perform fast point-to-point motion and high precision positioning after settling in spite of external disturbances or residual vibrations. We proposed a new mode switching control algorithm with an application to dual stage for long range and high precision positioning. The proposed algorithm uses a proximate time-optimal servomechanism for the fast settling and a time-delay controller for the high precision positioning. Experimental results show that the proposed method enables smooth mode switching and improves the settling time and the precision accuracy after settling by over than 33% and 45%, respectively.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.12 no.3
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• pp.317-324
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• 2005

Purpose: The study was done to investigate whether positioning relieves the back pain and enhances comfort during bed rest after transhepatic arterial chemoembolization(TACE). Methods: A quasi-experimental design with non-equivalent control group non-synchronized design was used. The experimental group was placed semi Fowler's position for the first 2 hours. The following 4 hours the position was rotated hourly between 30 degrees laterally inclined position and a semi Fowler's position. The control group was maintained in a supine position for the 6 hours. Data were analyzed using t-test, $x^2$-test, Fisher's exact test and repeated measures ANOVA. Results: 1) Back pain intensity significantly decreased in the experimental group compared to the control group. 2) Comfort level significantly decreased in both groups, but there was no significant difference between the two groups. 3) There were no hematoma and bleeding complication in either group. In addition, there was no significant difference in urinary retention between the two groups. 4) Analgesics were less frequently taken by the experimental group. Conclusion: These results suggest that positioning relieves back pain without causing an increased incidence of hematoma and bleeding formation after TACE and this nursing intervention might help patients be more comfortable during the treatment of TACE.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.62-71
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• 2009

In this paper, an improved drive method of piezoelectric PZT stack actuator for micro-positioning system is proposed and the performances are evaluated. This type of amplifier is based on switching technology efficiently handling the arbitrary regenerative energy from the piezoelectric actuator. The conventional voltage-feedback control method has the THD of -32dB (${\approx}2.5%$) with 100mHz sinusoidal reference, which means that the positioning performance in linearity degrades due to the hysteretic relationship between actuator voltage and the displacement. This paper proposed an improved charge-controlling method, which utilizes differential information of charge reference instead of integrating the actuator's current. The current waveform has THD under -40dBV (=1%) and the displacement waveform nearly -52dB (${\approx}0.25%$), which means that the positioning performance is very excellent. Finally, another method of the displacement feedback control has better performance than the voltage method, however there exists a limitation in performance of the system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.6
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• pp.599-606
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• 2014

Since the accuracy of Global Positioning System (GPS)-based vehicle positioning system is significantly degraded or does not work appropriately in the urban canyon, the integration techniques of GPS with Inertial Navigation System (INS) have intensively been developed to improve the continuity and reliability of positioning. However, its accuracy is degraded as INS errors are not properly corrected due to the GPS signal blockage. Recently, the image-based positioning techniques have been started to apply for the vehicle positioning for the advanced in processing techniques as well as the increased the number of cars installing the camera. In this study, Single Photo Resection (SPR), which calculates the camera exterior orientation parameters using the Ground Control Points (GCPs,) has been integrated with the INS/GPS for continuous and stable positioning. The INS/GPS/SPR integration was implemented in both of a loosely and a tightly coupled modes, based on the Extended Kalman Filter (EKF). In order to analyze the performance of INS/SPR integration during the GPS outage, the simulation tests were conducted with a consideration of factors affecting SPR performance. The results demonstrate that the accuracy of INS/SPR integration is depended on magnitudes of the GCP errors and SPR processing intervals. Additionally, the simulation results suggest some required conditions to achieve accurate and continuous positioning, used the INS/SPR integration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.997-1005
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• 2008

Linear motor stage is a useful device in precision engineering field because of its simple power transmission mechanism and accurate positioning. Even though linear motor stage shows fine positioning accuracy along travel axis, geometric dependent errors which relay on machining and assembling accuracy should be addressed to increase total positioning performances. In this paper, we suggests a cost effective yaw error compensation servo-system which is mounted on platform of the stage and nullify travel position dependent yaw error. This paper also provides a method of designing a sliding mode control which is robust to existing friction disturbance and model uncertainties. The reachability condition of slinding mode control for the yaw error compensating servo-system has been established. From some experimental results by using an experimental set-up, the sliding mode control showed its effective in disturbance rejection and its performance was superior to conventional linear controls.