• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.3
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• pp.375-382
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• 2004

This paper presents control designs using neural networks (NN) for a XY positioning table. The proposed neuro-controller is composed of an outer PD tracking loop for stabilization of the fast flexible-mode dynamics and an NN inner loop used to compensate for the system nonlinearities. A tuning algorithm is given for the NN weights, so that the NN compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded weight estimates. Formal nonlinear stability proofs are given to show that the tracking error is small. The proposed neuro-controller is implemented and tested on an IBM PC-based XY positioning table, and is applicable to many precision XY tables. The algorithm, simulation, and experimental results are described. The experimental results are shown to be superior to those of conventional control.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.170-173
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• 2001

To apply stereo vision system to obstacle recognition system of AGV, we constructed algorithm of stereo matching and distance measuring with stereo image for positioning of object in area. And using this system, we look into the error between real position and measured position, and studied relationship of compensation.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.307-309
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• 1993

Robot's kinematic equation is not perfect. In this paper, a method for reducing the positioning error which comes from the imperfect robot kinematics is introduced. This method compensates the parameter of the kinematic equation using real positioning error. And the trajectories using these compensated parameterare compared with uncompensated ones.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.889-897
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• 2016

This paper presents an improved approach for compensating rotor position signal displacement in brushless DC (BLDC) motors with misaligned hall-effect sensors. Typically, the hall-effect sensors in BLDC motors are located in each phase and positioned exactly 120 electrical degrees apart. However, limitations in mechanical tolerances make it difficult to place hall-effect sensors at the correct location. In this paper, a position error compensator to counteract the hall-effect sensor positioning error is proposed. The proposed position error compensator uses least squares error analysis to adjust the relative position error and back-EMF information to reduce the absolute offset error. The effectiveness of the proposed approach is verified through several experiments.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.288-291
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• 2001

This paper present effective odometry error compensation using multisensor fusion for the accurate positioning of mobile robot in navigation. During obstacle avoidance and wall following of mobile robot, position estimates obtained by odometry become unrealistic and useless because of its accumulated errors. To measure the position and heading direction of mobile robot accurately, odometry sensor a gyroscope and an azimuth sensor are mounted on mobile robot and Complementary-filter is designed and implemented in order to compensate complementary drawback of each sensor and fuse their information. The experimental results show that the multisensor fusion system is more accurate than odometry only in estimation of the position and direction of mobile robot.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.367-372
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• 2000

Accuracy of a machined component is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the accuracy of this relative motion is the geometric error of machine tools. In this study, geometric error is modeled using form shaping motion of machine tool, where a form shaping function is derived from the homogeneous transformation matrix. Geometric errors are measured by laser interferometer. After that, the local positioning error can be estimated from the form shaping model and geometric error data base. From this information, we can remodel the part by shifting the design surface to the amount of positional error. By generating tool path to the redesigned surface, we can reduce the machining error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.244-247
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• 2002

The performance of the precision micro-positioning 4-dof stage is presented. The compact design utilizes the monolithic mechanism to achieve the translation in the Z axis and rotation in the $\theta$ z, $\theta$ x and $\theta$ y axes with high stiffness and high damping. Hysteresis, nonlinearity, and drift of the piezoelectric effects are improved by incorporating the sensors in a feedback control. Experiments demonstrate that the micro-positioning stage is capable of 2nm resolution over the travel range of 25$\mu\textrm$ m in the Z axis, 0.0l7 $\mu\textrm$ rad resolution over the 170$\mu\textrm$ rad in the $\theta$ z and 0.011 $\mu\textrm$ rad resolution over the $\mu\textrm$ rad in the $\theta$ x and $\theta$ y axes. The cross-axis interferences among the axes are at a noise range. This stage is available for positioning error compensation of the XY stage with large stroke.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.670-691
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• 2013

In RSSI-based RFID(Radio Frequency IDentification) indoor localization system, the signal path loss model of each sub-region is different from others in the whole localization area due to the influence of the multi-path phenomenon and other environmental factors. Therefore, this paper divides the localization area into many sub-regions and constructs separately the signal path loss model of each sub-region. Then an improved LANDMARC method is proposed. Firstly, the deployment principle of RFID readers and tags is presented for constructing localization sub-region. Secondly, the virtual reference tags are introduced to create a virtual signal strength space with RFID readers and real reference tags in every sub-region. Lastly, k nearest neighbor (KNN) algorithm is used to locate the target object and an error compensating algorithm is proposed for correcting localization result. The results in real application show that the new method enhances the positioning accuracy to 18.2% and reduces the time cost to 30% of the original LANDMARC method without additional tags and readers.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.11-14
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• 2007

An additive servo-system is developed to improve straightness of linear motor stages. For linear motor stages used in the field of high-precision linear motion process, high straightness accuracy is necessary as well as positioning accuracy in the longitudinal axis. In such cases, machining and assembling cost increases to improve the straightness accuracy. An electro-magnetic actuator which is relatively cost effective than any other conventional servo-systems is suggested to compensate the fixed straightness error. To overcome the compensation error due to modeling error and friction disturbance, a sliding mode control is addressed. The effectiveness of the suggested mechanism and the control are illustrated along with some experimental results.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.4
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• pp.181-186
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• 2015

A High-degree Cubature Kalman Filter (CKF) is proposed to deal with the Strapdown Inertial Navigation System (SDINS) alignment problem. In-flight Alignment (IFA) is an effective method to compensate for attitude errors of the navigation system. While providing precise attitude error compensation, however, the external source aided alignment often creates a nonlinear filtering problem caused by a large misalignment angle. Introduced recently, Cubature Kalman Filter is a suitable technique for various nonlinear problems. In this paper, a higher degree CKF is applied to this accuracy-is-everything SDINS IFA problem. The simulation results show that the proposed technique outperformed a traditional nonlinear filter in terms of precision and alignment time.