• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.213-230
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• 2014

A novel real-time actuator failure detection algorithm is developed in this paper. Actuator fails when the input to the structure is different from the commanded one. Previous research has shown that one error function can be formulated for each actuator through interaction matrix method. For output without noise, non-zero values in the actuator functions indicate the instant failure of the actuator regardless the working status of other actuators. In this paper, it is further demonstrated that the actuator's error function coefficients will be directly calculated from the healthy input of the examined actuator and all outputs. Hence, the need for structural information is no longer needed. This approach is termed as direct method. Experimental results from a NASA eight bay truss show the successful application of the direct method for isolating and identifying the real-time actuator failure. Further, it is shown that the developed method can be used for real-time sensor failure detection.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.83.4-83
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• 2001

The paper presents a new closed-form, not a polynomial-form, solution of the direct kinematics of the 3-6 (Stewart-Gough) Platform. Many research works have presented a single high-order polynomial equation of the direct kinematics. However the polynomial equation causes potential problems such as complicated formulation procedures and discrimination of the actual solution from all roots, which results in time-consuming task and heavy computational burden. Thus, to overcome these problems, we use a new formulation approach, based on the Tetrahedron Approach, to derive easily a closed-form nonlinear equation of the direct kinematics and use not the Newton-Raphson method, but the Secant method to obtain quickly the solution from ...

• 로봇학회논문지
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• 제14권4호
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• pp.311-317
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• 2019

Direct teaching is an essential function for collaborative robots for easy use by non-experts. For most robots, direct teaching is implemented only in joint space because the realization of Cartesian space direct teaching, in which the orientation of the end-effector is fixed while teaching, requires a measurement of the end-effector force. Thus, it is limited to the robots that are equipped with an expensive force/torque sensor. This study presents a Cartesian space direct teaching method for torque-controlled collaborative robots without either a force/torque sensor or joint torque sensors. The force exerted to the end-effector is obtained from the external torque which is estimated by the disturbance observer-based approach with the friction model. The friction model and the estimated end-effector force were experimentally verified using the robot equipped with joint torque sensors in order to compare the proposed sensorless approach with the method using torque sensors.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.793-807
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• 2015

Constructing the influence lines of forces of statically indeterminate structures is a traditional issue in structural engineering and mechanics. However, the existing kinematic method for establishing these force influence lines is an indirect or mixed approach by combining the force method with the theorem of reciprocal displacements, which is yet inconsistent with the kinematic method for statically determinate structure. This paper proposes the direct kinematic method in conjunction with the load-displacement differential relation for exactly constructing influence lines of reaction and internal forces of indeterminate structures. Firstly, through applying the principle of virtual displacement, the formula for influence lines of reaction and internal forces of indeterminate structure via direct kinematic method is derived based on the released structure. Then, a computational approach with a clear concept and unified procedure as well as wide applicability based on the load-displacement differential relation of beam is suggested to achieve conveniently the closed-form expression of force influence lines, and exactly draw them. Finally, three representative examples for constructing force influence lines of statically indeterminate beams and frame illustrate the superiority of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.543-547
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• 1994

In this paper, the new approach and technique are introduced and derived from the original Lyapunov direct method which is used to decide the stability of system conveniently. This proposed technique modifies the formal concepts of the sufficient conditions of Lyapunov stability and is able to generate the methods for the robust design of control systems. Also, it applies to the dynamic systems with bounded perturbations and the results of the computer program using the new concept are compared with those of previous research papers and conventional Lyapunov direct method. It is possible to recognize the practical improvements of the estimation of robustness bounds of the systems.

• Journal of Power Electronics
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• 제16권3호
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• pp.994-1003
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• 2016

Two major obstacles in the utilization of electrical vehicles are their price and range. The collaboration of direct torque control (DTC) with induction motor (IM) is preferred for its low cost, easy implementation, and parameter independency. However, in terms of edges, the method has drawbacks, such as variable switching frequency and undesired current harmonic distortion. These drawbacks result in acoustic noise, reduced efficiency, and electromagnetic interference. A feed-forward approach for stator-flux-oriented DTC with space vector pulse-width modulation is presented in in this paper. The outcome of the proposed method is low current harmonic distortion with fixed switching frequency while preserving the torque performance and simple application feature of basic DTC. The method is applicable to existing and forthcoming IM drive systems via software adaptation. The validity of the proposed method is confirmed by simulation and experimental results.

• 한국멀티미디어학회논문지
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• 제24권2호
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• pp.167-177
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• 2021

In the field of augmented reality, edge-based methods have been popularly used in tracking textureless 3D objects. However, edge-based methods are inherently vulnerable to cluttered backgrounds. Another way to track textureless or poorly-textured 3D objects is to directly align image intensity of 3D object between consecutive frames. Although the direct methods enable more reliable and stable tracking compared to using local features such as edges, they are more sensitive to occlusion and less accurate than the edge-based methods. Therefore, we propose a method that combines an edge-based method and a direct method to leverage the advantages from each approach. Experimental results show that the proposed method is much robust to both fast camera (or object) movements and occlusion while still working in real time at a frame rate of 18 Hz. The tracking success rate and tracking accuracy were improved by up to 84% and 1.4 pixels, respectively, compared to using the edge-based method or the direct method solely.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권1호
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• pp.72-82
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• 2008

Various surgical approaches in the mandibular condyle fracture have been reported and many advantages of intraoral reduction were also introduced. But there are still controversies about surgical method of condylar fractures up to date. To establish the surgical approach protocol of condylar fracture, from May 2001 to December 2004, total 65 patients with 74 fractures of the mandibular condyle were reviewed during 2 years, retrospectively. All cases were classified according to the treatment considering factors, such as the level of fracture, degree and direction of displacement of fractured segment, patient’s age and gender, surgical approach methods, and their complications. Especially, advantages and surgical limitations of extraoral surgical approach, such as direct reduction and fixation via submandibular approach, Nam’s method, and endaural approach, were compared with those of intraoral surgical approach, such as direct intraoral reduction with transbuccal fixation or right angle driver system, and intraoral reinsertional approach after extraoral fixation of fractured fragment. The guidelines of surgical approach of condylar fracture based on our clilnical retrospective experiences and literature reviews can be suggested.

• ETRI Journal
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• 제46권3호
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• pp.421-431
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• 2024

In this study, a direct position tracking method for non-circular (NC) signals using distributed passive arrays is proposed. First, we calculate the initial positions of sources using a direct position determination (DPD) approach; next, we transform the tracking into a compensation problem. The offsets of the adjacent time positions are calculated using a first-order Taylor expansion. The fusion calculation of the noise subspace is performed according to the NC characteristics. Because the proposed method uses the signal information from the previous iteration, it can realize automatic data associations. Compared with traditional DPD and two-step localization methods, our novel process has lower computational complexity and provides higher accuracy. Moreover, its performance is better than that of the traditional tracking methods. Numerous simulation results support the superiority of our proposed method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.93-96
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• 2001

Design sensitivity is calculated in the sheet metal forming process with an elasto-plastic finite element analysis and a direct differentiation method The sensitivity analysis is concerned with the time integration the constitutive relation considering planar anisotropy, shell elements and the contact scheme. The present result is compared with the result obtained with the finite difference approach in deep drawing processes. The obtained sensitivity information is applied to the simple optimization process for the sheet metal forming process.