• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.355-360
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• 2002

To calibrate a non-redundantly actuated parallel mechanism, one can find actual kinematic parameters by means of geometrical constraint of the mechanism's kinematic structure and measurement values. However, the calibration algorithm for a non-redundant case does not apply fur a redundantly actuated parallel mechanism, because the angle error of the actuating joint varies with position and the geometrical constraint fails to be consistent. Such change of joint angle error comes from constraint torque variation with each kinematic pose (meaning position and orientation). To calibrate a redundant parallel mechanism, one therefore has to consider constraint torque equilibrium and the relationship of constraint torque to torsional deflection, in addition to geometric constraint. In this paper, we develop the calibration algorithm fir a redundantly actuated parallel mechanism using these three relationships, and formulate cost functions for an optimization algorithm. As a case study, we executed the calibration of a 2-DOF parallel mechanism using the developed algorithm. Coordinate values of tool plate were measured using a laser ball bar and the actual kinematic parameters were identified with a new cost function of the optimization algorithm. Experimental results showed that the accuracy of the tool plate improved by 82% after kinematic calibration in a redundant actuation case.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.4
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• pp.309-316
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• 2016

In this study, we described the design of a three-axis force/torque sensor for measuring the force and torque in a lower-limb rehabilitation robot. The three-axis force/torque sensor is composed of Fx force sensor, Fz force sensor and Tz torque sensor. The sensing element for Fx force sensor and Tz torque sensor is used in a two-step parallel plate beam, and that of Fz force sensor is used in a parallel plate beam. The rated loads of Fx force sensor, Tz torque sensor and Fz force sensor are 300 N, 15 N m and 100 N, respectively. The three-axis force/torque sensor was designed using the finite element method, and manufactured using strain-gauges. The three-axis force sensor was further characterized. As a result, the interference error of the three-axis force/torque sensor was < 1.24%, the repeatability error of each sensor was < 0.03%, and the non-linearity was < 0.02%.

• International Journal of Control, Automation, and Systems
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• v.3 no.3
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• pp.453-460
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• 2005

In this paper, a prototype Cartesian Parallel Manipulator (CPM) is demonstrated, in which a moving platform is connected to a fixed frame by three PRRR limbs. Due to the orthogonal arrangement of the three prismatic joints, it behaves like a conventional X-Y-Z Cartesian robot. However, because all the linear actuators are mounted at the fixed frame, the manipulator may be suitable for applications requiring high speed and accuracy. Using a geometric method and the practical assumption that three revolute joint axes in each limb are parallel to one another, a simple forward kinematics for an actual model is derived, which is expressed in terms of a set of linear equations. Based on the error model, two calibration methods using full position and length measurements are developed. It is shown that for a full position measurement, the solution for the calibration can be obtained analytically. However, since a ball-bar is less expensive and sufficiently accurate for calibration, the kinematic calibration experiment on the prototype machine is performed by using a ball-bar. The effectiveness of the kinematic calibration method with a ball-bar is verified through the well­known circular test.

• Journal of Communications and Networks
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• v.1 no.2
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• pp.118-133
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• 1999

In this paper we compare linear and non-linear inter-ference cancellation for systems employing code division multi-ple access (CDMA) techniques. Specifically, we examine linear and non-linear parallel interference cancellation(also called multi-stage cancellation) in relationship to other multiuser detection al-gorithms. We show the explicit relationship between parallel inter-ference cancellation and the decorrelator (or direct matrix inver-sion). This comparison gives insight into the performance of paral-lel interference cancellation (PIC) and leads to vetter approaches. We also show that non-linear PIC approaches with explicit chan-nel setimation can provide performance improvement over linear PIC, especially when using soft non-linear symbol estimates. The application of interference cancellation to non-linear modulation techniques is also presented along with a discussion on minimum mean-squared error(MMSE) symbol estimation techniques. These are shown to further improve the performance of parallel cancella-tion.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.378-380
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• 2006

A high speed Analog parallel processing-based Viterbi decoder with a circularly connected 2D analog processing cell array is proposed. It has a 2D parallel processing structure in which an analog processing cell is placed at each node of trellis diagram is connected circulary so that infinitively expanding trellis diagram is realized with the fixed size of circuits. The proposed Viterbi decoder has advantages in that it is operated with better performance of error corrections, has a shorter latency and requires no path memories. In this parer, the performance of error correction as a reference position with the Analog parallel processing-based Viterbi decoder is testd via the software simulation

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.492-495
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• 2001

In order to utilize a parallel machine tool for CAM system, the development of adequate interpolator is necessary. This paper presents a quintic B-spline interpolator with algorithm of limiting maximum interpolation error. The favored property of near arc-length parametrization in the curve representation is used in the implementation of the reference command generation. Then, this interpolator is applied to cubic parallel manipulator to show its validity.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.41-47
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• 2009

This research deals with evaluation of machining accuracy for Parallel Kinematic Machine Tool(PKMT) applied parallel type robot system with high precision and stiffness. For this purpose, machine simulation is carried out to foreknow collision and interference between workpiece and tool. Furthermore, on the basis of machine simulation data, PKMT is manufactured. Machining accuracy such as cylindricity straightness, squareness, parallelism circularity, concentricity pitch error and yaw error, is measured by using coordinate measuring machine. Test piece for evaluation of machining accuracy is designed and manufactured under the standard of ISO 10791-7.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.32-38
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• 2012

In this paper, to eliminate intersymbol interference of the received signal due to multipath propagation, a parallel equalization algorithm using two error estimation functions is proposed. In the proposed algorithm, multilevel two-dimensional signals are considered as equivalent binary signals, then error signals are estimated using the sigmoid nonlinearity effective at the initial phase equalization and threshold nonlinearity with high steady-state performance. The two errors are scaled by a weight depending on the relative accuracy of the two error estimations, then two filters are updated differentially. As a result, the combined output of two filters was to be the optimum value, fast convergence at initial stage of equalization and low steady-state error level were achieved at the same time thanks to the combining effect of two operation modes smoothly. Usefulness of the proposed algorithm was verified and compared with the conventional method through computer simulations.

• Honam Mathematical Journal
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• v.27 no.2
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• pp.317-332
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• 2005

In this paper we consider the hp-version to solve non-constant coefficients elliptic equations on a bounded, convex polygonal domain ${\Omega}$ in $R^2$. A family $G_p=\{I_m\}$ of numerical quadrature rules satisfying certain properties can be used for calculating the integrals. When the numerical quadrature rules $I_m{\in}G_p$ are used for computing the integrals in the stiffness matrix of the variational form we will give its variational form and derive an error estimate of ${\parallel}u-{\widetilde{u}}^h_p{\parallel}_{1,{\Omega}$.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.50-52
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• 2019

Dynamic resistance equalization is a viable technique to balance SOC of cells in a parallel-connected battery configuration due to high equalization performance, simplicity and low-cost. However, an inappropriate design of the equalization resistor can degrade the equalization performance and increase the power loss. This paper proposes an optimization process to design the equalization resistors to minimize power loss and equalization error. The simulation results show that the optimally designed resistor significantly enhance the performance in comparison with the conventional fixed-resistor equalization.