• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.511-514
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• 2005

This paper propose an advanced control strategy to improve vehicle handling and directional stability by integrating Active Front Steering(AFS) with Electronic Stability Program(ESP) . The effect of the integrated control system on the vehicle handling characteristics and directional stability is studied through a close loop computer simulation of and eight degree of freedom nonlinear vehicle model and driver model. Simulation results confirm the effectiveness of the proposed control system and the overall improvements in vehicle handling and directional stability

• 대한전기학회논문지:시스템및제어부문D
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• 제52권5호
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• pp.268-276
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• 2003

In this paper, we present a new control and monitoring technique for a power system using CAN(Controller Area Network). Feedback control systems having co'ntrol loops closed through a network(i.e. Ethernet, ControlNet, CAN) are called NCSs(Networked Control Systems). The major problem of NCSs is the variation of stability property according to time delay including network-induced delay and computation delay in nodes. We present a new stability analysis method of NCSs with time delay exploiting a state-space model of LTI(Linear Time Invariant) interconnected systems. The proposed method can determine a proper sampling period of NCSs that preserves stability performance even in NCSs with a dynamic controller. We design CAN nodes which can transmit control and monitoring data through CAN bus and apply these to NCSs for a power system. The results of the experiment validate effectiveness of our control and monitoring technique for a power system.

• 한국정밀공학회지
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• 제18권8호
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• pp.116-121
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• 2001

The paper presents the dynamic characteristics of a rotor-bearing system supported by an actively controlled hydrodynamic journal bearing. The proportional. derivative and integral controls are adopted for the control algorithm to control the hydrodynamic journal bearing with an axial groove. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis, which uses the Reynolds condition. The speed at onset of instability of a rotor-bearing system is increased by both proportional and derivative control of the bearing. The proportional control increases the stability threshold without affecting the whirl ratio. However, for the derivative control of the bearing, increase of stability threshold speed is accompanied by a parallel reduction of the whirl ratio. The integral control has no effect on stability characteristics of hydrodynamic journal bearing. The PD-control is more effective than proportional or derivative control. Results 7how the active control of bearing can be adopted for the stability improvement of a rotor-bearing system.

• 한국정밀공학회지
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• 제22권4호
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• pp.27-36
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• 2005

Some studies have shown that unstable factors are inherent in WEDM process, causing the instability of the discharging pulse to reach about 40∼60％ in normal machining. Transient stability is an important subject in WEDM process since there is a close relationship between stability and machining performance, such as the characteristics of a machined surface, machining speed and problem of instability like wire rupture phenomenon. Among the many machining parameters affecting WEDM machining state, three specific parameters (Vr, Ip, off time ) are major controllable variables that can be applied in transient stability control. And, this research investigates the implementation and analysis of real-time micro control of the discharging stability of WEDM (Wire Electric Discharge Machining) process.

• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.389-395
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• 2012

The problem of spacecraft attitude control is solved using an adaptive neuro-fuzzy inference system (ANFIS). An ANFIS produces a control signal for one of the three axes of a spacecraft's body frame, so in total three ANFISs are constructed for 3-axis attitude control. The fuzzy inference system of the ANFIS is initialized using a subtractive clustering method. The ANFIS is trained by a hybrid learning algorithm using the data obtained from attitude control simulations using state-dependent Riccati equation controller. The training data set for each axis is composed of state errors for 3 axes (roll, pitch, and yaw) and a control signal for one of the 3 axes. The stability region of the ANFIS controller is estimated numerically based on Lyapunov stability theory using a numerical method to calculate Jacobian matrix. To measure the performance of the ANFIS controller, root mean square error and correlation factor are used as performance indicators. The performance is tested on two ANFIS controllers trained in different conditions. The test results show that the performance indicators are proper in the sense that the ANFIS controller with the larger stability region provides better performance according to the performance indicators.

• 전력전자학회논문지
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• 제10권1호
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• pp.1-12
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• 2005

본 논문은 HVDC 시스템의 제어기나 제어형태에 따른 HVDC시스템의 안정도를 다루고 있다. HVDC시스템은 제어기 관점에서 PI 또는 PD 그리고 PID 제어기를 가지고 있으며, 각각의 경우는 시스템의 응답이나 안정도를 고려하여 설계되고 있다. 그리고 HVDC시스템은 다른 시스템과 다르게 전압제어기, 전류 제어기 그리고 Alpha 제어기와 같은 다-제어모드로 구성되어 있기 때문에 각각의 경우에 따른 안정도를 구해야한다. HVDC시스템의 안정도를 고려한 제어 게인 튜닝은 HVDC시스템의 제어기를 축약하여 AC계통을 고려한 형태로 구해야하며, PSS/E급에서 해석될 수 있게 하였다. 또한 본 논문에서 구한 제어 게인은 3상 순시해석이 가능한 PSCAD/EMTDC급에서도 안정도를 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.736-740
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• 2004

In order to overcome the problems of simulation methods, the power system transient stability assessment method using critical fault clearing time functions has been developed. Using the above method, this paper has developed the new method which can assess accurately and efficiently the effects of control and protection systems on transient stability which is the most important characteristic to assess in power systems. At first, critical fault clearing time functions CCT(W:load) are defined by taking notice of the fact that transient stability is mainly controlled by fault clearing time and load. Next, the method to be enable to assess accurately and efficiently the effects of control and protection systems on transient stability has been newly developed by using the above functions. Finally, it has been applied to the effect assessment in the occurrence of a three-phase fault in a model power system. Results of application have been clarified its effectiveness.

• 대한임베디드공학회논문지
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• 제4권2호
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• pp.97-102
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• 2009

In this paper, the problem of stability analysis for networked control systems with norm-bounded parameter uncertainties is investigated. By construction Lyapunov's functional, a new delay-dependent stability criterion for uncertain networked control system is established in terms of LMIs (linear matrix inequalities) which can be easily by various convex optimization algorithms. One numerical example is included to show the effectiveness of proposed criterion.

• PNF and Movement
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• 제13권4호
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• pp.203-213
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• 2015

Purpose: Deficits in lower-extremity function and trunk control ability have a negative impact on individuals with hemiplegia. This case report aimed to describe the effect of trunk stability exercises using proprioceptive neuromuscular facilitation (PNF) on trunk control ability, balance, and gait in a patient with hemiplegia. Methods: A 77-year-old man with hemiplegia and trunk and lower extremity impairment participated in this four-week training intervention. Results: The patient demonstrated improvements in trunk control ability, balance, and gait performance. Outcome measures (Fugl-Meyer Assessment Lower Extremity (FMA-LE), Trunk Control Test, Berg Balance Scale, Timed Up and Go test, 10 Meter Walk test) were measured before and after the training program. Conclusion: The results of this case suggest that a trunk stability exercise using a PNF program may improve trunk control ability, balance, and gait in a patient with hemiplegia.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.127-136
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• 2008

Vehicle stability is a very important subject in vehicle design and control, because vehicle safety is closely dependent upon its dynamic stability. The control logic for four-wheel steering(4WS) systems, in which maintaining at least the specified stability region is the control objective, was constructed using the simplified vehicle model of 3 degree-of-freedoms. The improvement of vehicle stability was verified through computer simulations for the slalom and the double lane change maneuver using the multi-body dynamic model in MSC.ADAMS.