• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.1
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• pp.108-118
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• 2017

In this paper, the path tracking controller for a surface vessel based on the sliding mode control (SMC) with the switching law is proposed. In order to have no restriction on movement and improved tracking performance, the proposed control system is developed as follows: First, the kinematic and dynamic models in Cartesian coordinates are considered to solve the singularity problem at the origin. Second, the new multiple sliding surfaces are designed with the SMC and approach angle concept to solve the under-actuated property. Third, the switching control system is designed to improve tracking performance. To prove the stability of the proposed switching system under the arbitrary switching, the Lyapunov stability analysis method with the common Lyapunov function is used. Finally, the computer simulations are performed to demonstrate the performance, effectiveness and stability of the proposed tracking controller of a surface vessel.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.212-219
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• 1999

This paper describes the NANDO VDC (Vehicle Dynamics Control) system for the vehicle stability enhancement and consists of the control strategies , computer simulation and tests on the various road surface. This VDC system controls the dynamic vehicle motion in the emergency situation such as the final oversteer/understeer andallows the vehicle to follow the course as desired by the driver. The system is based on an active yaw control and its performance verified by the test is shown. Also the comparison between the MANDO VDC System and a competitor is carried out.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1112-1120
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• 1994

This paper presents a servo control scheme for the surface-mounted permanent-magnet synchronous motor(SPMSM) which essentially uses vector control algorithm. The control system is composed of the PI controller for speed control and the current controller using space voltage vector PWM technique. The high-speed calculation and processing for vector control is carried out by TMS320C31 digital signal processor and IGBT module. The proposed scheme is verified through digital simulations and experiments for 2.2kW SPMSM and shows good dynamic performance.

• Journal of Power Electronics
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• v.10 no.1
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• pp.58-64
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• 2010

In this paper, the dynamic performance of oscillating linear motors, which are used in household refrigerators, is improved by means of efficient parameter identification. Oscillating linear motor parameters are identified as a function of the piston position and the motor current. They are stored in a ROM table and used later for an accurate estimation of piston position. The identified motor parameters are also approximated to the $2^{nd}$-order surface functions, which are divided into 2 or 4 subsections in order to decrease identification errors. Experimental results are given to show that the proposed control scheme can provide oscillating linear motors with high dynamic performance.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.112-124
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• 2004

A neural network based adaptive reconfigurable flight controller is presented for a class of discrete-time nonlinear flight systems in the presence of variations of aerodynamic coefficients and control effectiveness decrease caused by control surface damage. The proposed adaptive nonlinear controller is developed making use of the backstepping technique for the angle of attack, sideslip angle, and bank angle command following without two time separation assumption. Feedforward multilayer neural networks are implemented to guarantee reconfigurability for control surface damage as well as robustness to the aerodynamic uncertainties. The main feature of the proposed controller is that the adaptive controller is developed under the assumption that all of the nonlinear functions of the discrete-time flight system are not known accurately, whereas most previous works on flight system applications even in continuous time assume that only the nonlinear functions of fast dynamics are unknown. Neural networks learn through the recursive weight update rules that are derived from the discrete-time version of Lyapunov control theory. The boundness of the error states and neural networks weight estimation errors is also investigated by the discrete-time Lyapunov derivatives analysis. To show the effectiveness of the proposed control law, the approach is i]lustrated by applying to the nonlinear dynamic model of the high performance aircraft.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1951-1962
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• 1993

The creation process of a typical machined surface is treated here as a dynamic system. An investigation is carried out to establish a relationship between the characteristics of cutting force fluctuations that cause vibration response of the tool-workpiece system and the formation of surface in face cutting by sintered carbide cutting tool. Cutting force is measured and analyzed in frequency domain. The power spectral densities of cutting force give a useful information in surface generation and it can be used to find out the control factor of surface roughness. The terms, PSD ratio & Normalized spindle frequency PSD, are defined and when the value of power in spindle frequency is absolutely little but relatively large, it is obtained high accuracy surface roughness. The aim of this research is to find surface profile by measured and analyzed cutting force signals. The simulation of surface generation gives the comprechension of its mechanism and help to predict and control the surface quality. In this study, it is suggested what informations about surface generation can be acquired from the cuttuing force signal and an way of generating a better surface.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.2
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• pp.61-70
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• 2023

PURPOSE: This study evaluated an intrinsic foot strengthening exercise method for flat feet by comparing the effects of intrinsic exercises on a stable surface and intrinsic exercises on an unstable surface. METHODS: Twenty-four people with flat feet were divided into two groups. The control group performed short foot exercises and toe towel curl exercises on the stable support surface. The experimental group performed short foot exercises and toe towel curl exercises on an unstable support surface using Aerostep. The navicular drop test, and the static and dynamic balance were measured before and after the intervention. RESULTS: In the experimental and control groups, there was a significant difference in the navicular drop test and static balance before and after the intervention (p < .05). On the other hand, there was no significant difference between the two groups (p > .05). In the dynamic balance, the experimental group showed significant differences in all directions after the intervention (p < .05). The control group showed significant differences in the postero-lateral direction and posteromedial direction (p < .05). In particular, in the forward direction, the experimental group had a more significant change than the control group (p < .05). CONCLUSION: Intrinsic foot muscle strengthening exercises performed on unstable surfaces can be an effective clinical exercise method to improve the dynamic balance ability of people with flat feet.

• PNF and Movement
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• v.17 no.2
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• pp.245-252
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• 2019

Purpose: The purpose of this study was to determine the effects of action observation training on lower limb muscle activity and dynamic balance in chronic stroke patients. Methods: This study evaluated 20 chronic stroke patients who were divided randomly into a control and an experimental group comprising 10 patients each. Both the experimental group and the control group performed the general exercise therapy provided by the hospital, but the experimental group also performed action observation training. Lower limb muscle activity was measured with a surface electromyograph, and dynamic balance was measured with the Timed Up and Go test and the 10-meter walk test. The paired t-test was used to compare the groups before and after the experiment. Furthermore, the independent t-test was used to assess differences in the degree of change between the two groups before and after the experiment. Results: The within-group comparisons for both the experimental group and the control group showed significant differences in muscle activity and dynamic balance (p<0.05). In a comparison between the groups, the differences in the muscle activity and dynamic balance of the experimental group appeared significant compared with those of the control group (p<0.05). Conclusion: The study results indicate that action observation training is effective in improving the muscle activity and dynamic balance of chronic stroke patients.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1171-1179
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• 2012

In this study, we consider a dynamic positioning system (DPS) design problem that can be extended to many application fields. Toward this end, tracking and positioning control problems are discussed. In particular, we design a tracking control system that incorporates an observer based on the 2-DOF servo system design approach in order to obtain the desired state information. In the case of observer design, a weighted $H_{\infty}$ error bound approach for a state estimator is considered. Based on an algebraic Riccati equation (inequality) approach, a necessary and sufficient condition for the existence of a full-order estimator that satisfies the weighted $H_{\infty}$ error bound is introduced. The condition for the existence of the estimator is denoted by a linear matrix inequality (LMI) that yields an optimized solution and the observer gain.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.783-792
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• 2011

The control of rail surface irregularity is very important for the high speed train service in the high speed rail. In order to manage it, initial, preventative, and maintainable rail grinding have been performed and among them, preventative rail grinding conducts in every each year. This study carried out the field test for dynamic track response according to rail surface irregularity comparing before and after rail grinding. In addition, the change of dynamic track responses according to rail grinding was analyzed and the fatigue life was estimated though Rainflow Counting Method and RMC Equivalence Stress. Therefore, it suggested that rail fatigue life should be increased by rail grinding, because amount of impact occurred on track is decreased by getting rid of rail surface irregularity.