• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.58-62
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• 1998

In the industrial motor drive systems, a torsional vibration is often generated because of the elastic elements in torque transmission. One of general methods for the system is H$\infty$ controller to suppress the torsional vibration and reject the torque disturbance. vibration and reject the torque disturbance. Moreover, the two-degrees-of-freedom controller, which includes the H$\infty$ controller, is designed in order to improve the command following property. In this paper, we propose a new H$\infty$ controller with partial state feedback. This method having simple structure satisfies with the fast command following property and the attenuation of disturbances and vibrations simultaneously, just like the complicated TDOF H$\infty$ controller

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.60-63
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• 2000

In this study, efficient force reflection algorithm is developed for the Haptic Display by using a proxy concept and friction model. When there are not any contacted obstacles the proxy is following human operator's command trajectory in the 3D virtual space. But when the operator's command trajectory is locating inside of the object, the proxy is constrained by the surface of the object. Here only with the information of the proxy position and operator's command trajectory at every time step, we can calculate the reflection force and its orientation. To display the friction force between two virtual stiff material which are sliding against each other, modified Karnopp's friction model is used. In the friction model, a damping term and a Stribeck effect term are included to display the relative velocity effect and stick-slip effect at the very low relative velocity region respectively.

• International Journal of Control, Automation, and Systems
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• v.6 no.3
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• pp.327-338
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• 2008

A fault tolerant control system design technique has been proposed and analyzed for managing performance degradation in the presence of multiple faults in actuators. The method is based on a control structure with a model reference reconfigurable control design in an inner loop and command input adjustment in an outer loop. The reduced dynamic performance requirements in the presence of different actuator faults are accounted for through different performance reduced (degraded) reference models. The degraded steady-state performances are governed by the reduced levels of command input. The reconfigurable controller is designed on-line automatically in an explicit model reference control framework so that the dynamics of the closed-loop system follow that of the performance reduced reference model under each fault condition. The reduced command input level is determined to prevent potential actuator saturation. The proposed method has been evaluated and analyzed using an aircraft example against actuator faults subject to constraints on the magnitude and slew-rate of actuators.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.19
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• pp.8331-8335
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• 2014

Background: Previous studies accessing the association of CYP2C19 with outcomes of patients using tamoxifen for breast cancer have yielded conflicting results. The aim of this meta-analysis is to obtain a more precise estimate of effects of CYP2C19 polymorphisms and to clarify their effects on survival of the breast cancer patients using tamoxifen. Materials and Methods: A systematic search of PubMed and Embase was performed, comparing patients with or without $CYP2C19^*2$ and $CYP2C19^*17$, relevant articles searched for. The following outcomes were included from the eligible studies: disease-free survival (DFS) and overall survival (OS), expressed by hazard ratios (HR) with corresponding 95% confidence interval (CI). Subgroup analysis by genotypes was also performed. Pooled estimates were calculated using random-effect model in accordance to the heterogeneity. Results: Six studies met the inclusion criteria. The integrated OR on the association between CYP2C19 and DFS, calculated by the random-effect model, was 0.54 (95%CI=0.34-0.84, p=0.013). Subgroup analysis showed that both $CYP2C19^*2$ and $CYP2C19^*17$ were associated with increased survival. The pooled results of two studies for OS were OR=0.46 (95%CI=0.21-1.01, p=0.233). Conclusions: This meta-analysis suggests that the $CYP2C19^*2$ and $CYP2C19^*17$ genotypes are associated with increased survival in breast cancer patients using tamoxifen.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.909-912
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• 2017

In implementing a computerized virtual training system, the auditory element is responsible for the human cognitive ability following visual elements. Especially, the improvement of hearing ability is closely related to the performance of the training, and it contributes to improvement of the training effect. In this paper, we propose a sound system that is necessary for constructing such a virtual training system as a test system that can use a sound source using a head related transfer function (HRTF). Functional and auditory tests were performed to evaluate system performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1412-1422
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• 2022

The importance of interoperability between weapon systems is continuously increasing. Usually it is implemented by data exchange. The existence of information heterogeneities between systems decreases the efficiency and quality of the implementations enterprise-widely. Many other developed countries increase the efficiency and quality of the implementations by using information exchange model commonly. However, Korean military is still not aware of the importance and necessity of the model. This study explains the necessity of development and adaptation of the Korea command and control information exchange model(KC2IEM), and presents the methodology for the development of the model, and verifies and improves it through a prototype model development. The completion of the information exchange model could not be possible by academic research, therefore this study contributes as a motivation and a stepping stone for the following developments.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2554-2566
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• 1994

Robot position/force control has been a difficult task owing to the interaction between a robot and an environment with a rather high stiffness. In addition to the dynamic instability, the interaction causes the following problem : 1) chattering at steady-state, 2) dynamic coupling effect of robot, and 3) performance degradation due to a titled environment. To solve the problem, the Time Delay Control(TDC), which has been known to be quiet robust to plant uncertainties and disturbances, has been applied. In conjunction to TDC, the following three ideas were also used : 1) To reduce the amplitude of the chattering at the steady state, a novel scheme was adopted to enhance the resolution type solution of A/D conversion for the force sensor. 2) To reduce the dynamic coupling, a trajectory type position command was tried on a comparative basis to the step command, as well as a more accurate mass matrix was used instead of the constant mass matrix. 3) And finally to improve the performance in the tilted environment, force derivatives instead of position derivatives were used in the TDC law. Computer simulations and experiments resulted in obvious improvements on the quality of the hybrid control, thereby clearly demonstrating the effectiveness of TDC with the proposed ideas.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1872-1875
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• 1998

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. Recently, there are new methods which estimate unknown state variables by using a reduced order observer and feedback these state variables by using a pole placement design method. But there is a trade-off between the fast command following property and the attenuation of disturbances and vibrations in these design methods. In this paper, the vibration suppression control of a two-mass system using a reference model is proposed. Because of using a reference model, the proposed control satisfy the fast command following property and the attenuation of disturbances and vibrations. Control parameter can be changed to maintain high system performance in control using a reference model. Experimental results show the validity of the proposed state feedback control using a reference model, and this controller is compared with the state feedback controller.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.1
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• pp.18-25
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• 2000

In the two-mass servo system driving a load through a flexible shaft, a shaft torsional vibration is often generated. PI controller has been generally used is speed control of such system because of the simplicity of structure and related theory. This paper presents the inertia ratio of the PI servo control system which can be designed by using optimal pole assignment method is fixed. Therefore, it's difficult to obtain the desired control characteristics for different systems only by PI control algorithm. To solve this problems the two-mass speed control system with PID controller is designed by using pole assignment method and an optimum PID parameters are derived by evaluating ITAE(Integral of time multiplied by the absolute error) performance index. But this design method has some problems due to a trade-off between the fast command following property and the attenuation of disturbances and vibrations. In this paper, 2-DOF PID control method which satisfies the command following property, the reduction of overshoot and the property of disturbance rejection at the same time is proposed. This is a practical speed controller using the desired value filter and the feedforward gain. From several simulations, it's clarified that the proposed 2-DOF PID controller is useful for the two-mass system, in comparison with the conventional PID controller.

• Nuclear Engineering and Technology
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• v.44 no.4
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• pp.369-378
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• 2012

A load-following operation in APR+ nuclear plants is necessary to reduce the need to adjust the boric acid concentration and to efficiently control the control rods for flexible operation. In particular, a disproportion in the axial flux distribution, which is normally caused by a load-following operation in a reactor core, causes xenon oscillation because the absorption cross-section of xenon is extremely large and its effects in a reactor are delayed by the iodine precursor. A model predictive control (MPC) method was used to design an automatic load-following controller for the integrated thermal power level and axial shape index (ASI) control for APR+ nuclear plants. Some tracking controllers employ the current tracking command only. On the other hand, the MPC can achieve better tracking performance because it considers future commands in addition to the current tracking command. The basic concept of the MPC is to solve an optimization problem for generating finite future control inputs at the current time and to implement as the current control input only the first control input among the solutions of the finite time steps. At the next time step, the procedure to solve the optimization problem is then repeated. The support vector regression (SVR) model that is used widely for function approximation problems is used to predict the future outputs based on previous inputs and outputs. In addition, a genetic algorithm is employed to minimize the objective function of a MPC control algorithm with multiple constraints. The power level and ASI are controlled by regulating the control banks and part-strength control banks together with an automatic adjustment of the boric acid concentration. The 3-dimensional MASTER code, which models APR+ nuclear plants, is interfaced to the proposed controller to confirm the performance of the controlling reactor power level and ASI. Numerical simulations showed that the proposed controller exhibits very fast tracking responses.