• 한국생산제조학회지
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• 제23권1호
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• pp.1-6
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• 2014

This paper describes a method of estimating and evaluating the volumetric errors of multi-axis machine tools. The estimation method is based on a generic model that was developed from conventional kinematic error models for the geometric and thermal errors to help predict the volumetric error easily in various configurations. To demonstrate the advantages of the model, an application in the early stages of a five-axis machine tool design is presented as an example. The model was experimentally evaluated for a four-axis machine tool by using the data from ISO230-6 and R-test measurements to compare the estimated and measured volumetric errors.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.498-505
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• 2002

Reducing odometer errors caused by kinematic imperfections in wheeled mobile robots is imestigated. Wheel diameters and wheelbase are corrected by using encoders without landmarks. A new velocity trajectory is proposed that compensates for an orientation error due to acceleration- resolution constraints on motor controllers. Based on this velocity trajectory, the wheel velocity of one out of two driven wheels may be changed by the traveled distance of the mobile robot. It is shown that a wheeled mobile robot can't move along a straight line exactly, even if kinematic correction are achieved perfectly, and this phenomenon is attributable to acceleration-resolution constraints on motor controllers. We experiment on a wheeled mobile robot with 2 d.o.f. are used in the experiment to verify the proposed scheme.

• 한국농공학회지
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• 제35권2호
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• pp.57-64
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• 1993

A modified kinematic wave model of the overland flow in vegetated filter strips was developed. The model can predict both flow depth and hydraulic radius of the flow. Existing models can predict only mean flow depth. By using the hydraulic radius, erosion, deposition and flow's transport capacity can be more rationally computed. Spacing hydraulic radius was used to compute flow's hydraulic radius. Numerical solution of the model was accomplished by using both a second-order nonlinear scheme and a linear solution scheme. The nonlinear portion of the model ensures convergence and the linear portion of the model provides rapid computations. This second-order nonlinear scheme minimizes numerical computation errors that may be caused by linearization of a nonlinear model. This model can also be applied to golf courses, parks, no-till fields to route runoff and production and attenuation of many nonpoint source pollutants.

• ETRI Journal
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• 제38권2호
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• pp.337-346
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• 2016

We propose a data-driven kinematic control method for a robotic spatial augmented reality (RSAR) system. We assume a scenario where a robotic device and a projector-camera unit (PCU) are assembled in an ad hoc manner with loose kinematic specifications, which hinders the application of a conventional kinematic control method based on the exact link and joint specifications. In the proposed method, the kinematic relation between a PCU and joints is represented as a set of B-spline surfaces based on sample data rather than analytic or differential equations. The sampling process, which automatically records the values of joint angles and the corresponding external parameters of a PCU, is performed as an off-line process when an RSAR system is installed. In an on-line process, an external parameter of a PCU at a certain joint configuration, which is directly readable from motors, can be computed by evaluating the pre-built B-spline surfaces. We provide details of the proposed method and validate the model through a comparison with an analytic RSAR model with synthetic noises to simulate assembly errors.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.23-31
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• 2003

This paper introduces a constraint operator for the kinematic calibration of a parallel mechanism. By adopting the concept of a constraint operator, the movement between two poses is constrained. When the constrained movements are satisfied, the active joint displacements are taken and inputted into the kinematic model to compute the theoretical movements. A cost function is derived by the errors between the theoretical movement and the actual movement. The parameters that minimize the cost function are estimated and substituted into the kinematic model for a kinematic calibration. A single constraint plane is employed as a mechanical fixture to constrain the movement, and three digital indicators are used as the sensing devices to determine whether the constrained movement is satisfied. This calibration system represents an effective, low cost and feasible technique for a parallel mechanism. A calibration algorithm is developed with a constraint operator and implemented on a parallel manipulator constructed for a machining center tool.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.191-196
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• 2003

This paper presents a method to design an adaptive controller for the kinematic model of a two-wheeled welding mobile robot (WMR) with unknown parameters. We propose a nonlinear controller based on the Lyapunov function to enhance the tracking properties of the WMR. The WMR can track any smooth curved welding path at a constant velocity of the welding point. The system has three degrees of freedom including two wheels and one torch slider. Torch slider motion is used for fast tracking. To design the tracking performance, the errors from WMR to steel wall is defined, and the controller is designed to drive the errors to zero as fast as possible. The effectiveness of the proposed controller is shown through simulation results.

• 대한전자공학회논문지
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• 제25권4호
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• pp.379-385
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• 1988

A kinematic control for redundant manipulators is consisdered. An efficient computation method is proposed to determine the joint variable solutions for a given Cartesian path of the end effector. In the proposed method, the Jacobian matrix and its pseudoinverse matrix are calculated intermittently only when the errors exceed the prescribed tolerance. Thereby, the computational burdens are greatly reduced, and at the same time, the errors are maintained within a tolerable range. To show the effectiveness of the mehtod, the result of the simulation is provided in which the redundancy of the manipulator is resolved to avoid the singularity.

• Journal of Astronomy and Space Sciences
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• 제29권3호
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• pp.269-274
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• 2012

Kinematic global positioning system precise point positioning (GPS PPP) technology is widely used to the several area such as monitoring of crustal movement and precise orbit determination (POD) using the dual-frequency GPS observations. In this study we developed a kinematic PPP technology and applied 3-pass (forward/backward/forward) filter for the stabilization of the initial state of the parameters to be estimated. For verification of results, we obtained GPS data sets from six international GPS reference stations (ALGO, AMC2, BJFS, GRAZ, IENG and TSKB) and processed in daily basis by using the developed software. As a result, the mean position errors by kinematic PPP showed 0.51 cm in the east-west direction, 0.31 cm in the north-south direction and 1.02 cm in the up-down direction. The root mean square values produced from them were 1.59 cm for the east-west component, 1.26 cm for the south-west component and 2.95 cm for the up-down component.

• 한국정밀공학회지
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• 제31권4호
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• pp.319-326
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• 2014

Accurate estimation of the robot's position has an important role in autonomous navigation. Odometry is one of the most widely used techniques for mobile robot positioning. However, odometry has a well-known drawback that the position errors are accumulated when the travel distance increases. The UMBmark method is the conventional odometry calibration scheme for two wheel differential mobile robots. In the UMBmark method, the approximations for small angles are used in order to simplify the calculations. In this paper, we propose the new calibration scheme by using experimental orientation errors. Kinematic parameters can be calculated accurately without approximations by using experimental orientation errors. The numerical simulation and experimental results show that the odometry accuracy can be improved by the proposed method.

• 대한공간정보학회지
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• 제10권2호
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• pp.87-95
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• 2002

실시간 동적(Real Time Kinematic) GPS는 실시간으로 높은 정밀도의 위치결정을 가능케 해준다. 만약 미지정수를 구하기 위하여 정수해를 사용한다면 수 mm의 정확도를 얻을 수 있고, 실 수해를 얻는다면 수십 cm 의 정확도를 얻을수 있다. 본 연구에서는 통일 측점에 대해 기존의 재래식 측량기법(Total Station), 정적(Static) 상대측위 GPS기법과 현장 Calibration에 의한 실시간 동적(Real Time Kinematic) GPS기법에 의해 측량을 수행하여 각 기법별 측정의 정확도 등을 비교 분석하여 현장 Calibration에 의한 실시간 동적 (Real Time Kinematic) GPS기법의 정확도를 분석고자 한다. 국소지역에서 기존의 실시간 동적(Real Time Kinematic) GPS방식을 보완한 현장 Calibration에 의한 실시간 동적(Real Time Kinematic) GPS 측량을 수행한 결과, 미지정수해의 고정해를 얻지 못하는 경우를 제외하고는 모두 6cm 이하의 오차가 나타났고, Control Point의 측점수를 3개와 4개로 변화시켜 실시간 동적(Real Time Kinematic) GPS 측량을 수행한 결과 두 측정치의 차이는 최대 3cm로 나타났다. 최종적으로 국소지역에서도 현장 Calibration에 의한 실시간 동적(Real Time Kinematic) GPS기법이 사용가능함을 알 수 있었다.