• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.4
• /
• pp.1-6
• /
• 2009

In this paper, we design a dynamic state feedback smooth stabilizer for a nonlinear system whose Jacobian linearization may have uncontrollable mode because its eigenvalues are on the right half-plane. After designing an augmented system, a dynamic exponent scaling and backstepping enable one to explicitly design a smooth stabilizer and a continuously differentiable Lyapunov function which is positive definite and proper. The convergence of the designed controller is proved by the new notion 'degree indicator'.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.6
• /
• pp.402-408
• /
• 2004

This paper proposes the novel V/f control method to improve the stability of a V/f controlled induction motor drive system. The conventional V/f control method used in the proposed V/f control method is a vector-based method that is slightly different from the existing conventional V/f control method. The proposed control method uses a dynamic current compensator to improve the stability of a V/f controlled induction motor drive system. This proposed method is easy to implement and completely eliminates the motor oscillation phenomenon causing the instability of a V/f controlled induction motor drive system, especially when the system is driven near the resonant frequency in steady-state with light load. Additionally, this paper analyzes theoretically the instability of a V/f controlled induction motor drive system and shows the validity of the Proposed V/f control method through simulation and experimental results.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.2
• /
• pp.7-14
• /
• 2009

In this paper we consider the problem of global finite-time stabilization for a class of uncertain nonlinear systems which include uncertainties. The uncertainties are time-varying disturbances or parameters belong to a known compact set. The proposed design method is based on backstepping and dynamic exponent scaling using an augmented dynamics, from which, a dynamic smooth feedback controller is derived. The finite-time stability of the closed-loop system and boundedness of the controller are preyed by the finite-time Lyapunov stability theory and a new notion 'degree indicator'.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.125-126
• /
• 2007

이 논문에서는 제어 가능한 선형시스템에 대한 다이나믹 터미널 슬라이딩 모드 제어기를 설계하고자 한다. 제안된 터미널 슬라이딩 모드구조와 제어기는 추가된 다이나믹스의 스캐일링을 통해 설계되며, 추가된 다이나믹스는 모든 상태변수들이 원점에 도달한 후에야 원점에 도달하므로 특이점을 가지지 않게 된다. 그리고 전체시스템의 유한시간 안정화는 유한시간 안정에 관한 리아프노프 함수를 이용하여 증명할 수 있다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.5
• /
• pp.391-399
• /
• 2005

Laser-generated ultrasonic inspection system is a non-contact scanning inspection device with high spatial resolution and wide bandwidth. The amplitude of laser-generated ultrasound is varied according to the energy of pulse laser and the surface conditions of an object where the CW measuring laser beam is pointing. In this paper, we correct the generating errors by measuring the energy of pulse laser beam and correct the measuring errors by extracting the gain information of laser interferometer at each time. h dynamic stabilizer is developed to stably scan on the surface of an object for an laser-generated ultrasonic inspection system. The developed system generates ultrasound after adaptively finding the maximum gain time of an laser interferometer and processes the signal in real time after digitization with high speed. In this paper, we describe hardware configuration and control algorithm to build a stable laser-generated ultrasonic inspection system. Also, we confirmed through experiments that the proposed correction method for the generating errors and measuring errors is effective to improve the performance of a system.

• Journal of the Institute of Convergence Signal Processing
• /
• v.6 no.3
• /
• pp.157-162
• /
• 2005

This paper presents an adaptive compensator using the fuzzy systems for robot manipulator with unknown frictions. In general, frictions are neglected or dynamic frictions are only considered in robot control theories. The proposed control method considers viscous frictions as well as dynamic frictions. Using the property that the frictions of joints are decoupled, SISO-fuzzy systems are utilized to approximate each friction. The stability of overall control system is proven and the adaptive laws are derived based on Lyapunov stability theorey. To verify the validity of the proposed control strategy, the results of computer simulations are shown for 2-link robot manipulator. The ability of approximating of the fuzzy system is also shown.

• Tribology and Lubricants
• /
• v.30 no.1
• /
• pp.9-14
• /
• 2014

In this Part II study, rotordynamic stability analyses were carried out to confirm improvements to the stability of a process high-speed lightweight centrifugal compressor, depending on the effects of tilting pad journal bearing designs. The bearing design variables considered were the clearances, LBPs, LOPs, and preloads. The results showed that the rotordynamic stability of the subject compressor rotor-bearing system improves exactly in accordance with the effects of the bearing design variables, which were determined in the preceding Part I study, owing to reduced bearing stiffnesses. Specifically, it was confirmed that the stability of the rotor system can be greatly improved by increasing both the machined and assembled bearing clearances, but there were no stability improvements by simply changing from an LBP to an LOP design. In addition, it was confirmed that for given fixed machined bearing clearances, the stability can be additionally improved by decreasing the preloads, i.e., by increasing the assembled clearances. In conclusion, it may be necessary to improve the designs of the original tilting pad bearings to obtain a sufficient margin of rotordynamic stability against a possible aerodynamic cross-coupled stiffness in a process high-speed centrifugal compressor. Thus, increasing the machined and assembled bearing clearances and decreasing the preload could be effective solutions.

• Tribology and Lubricants
• /
• v.29 no.6
• /
• pp.386-391
• /
• 2013

Part I of this study analyzed the effects of tilting pad bearing designs to reduce the stiffness of the bearings used in a process high-speed lightweight centrifugal compressor intended for a domestic refinery use. This was done in an attempt to enhance the robustness of its rotordynamic stability against possible aerodynamic cross-coupled stiffness. The bearing design variables reviewed were the clearances, LBPs, LOPs, and preloads. The results showed that there was practically no difference between the LBP and LOP designs in terms of the bearing stiffness, because the compressor rotor was lightweight and the bearings had relatively high preloads. Increasing both the machined and assembled clearances in bearing designs has resulted in the bearing stiffness being greatly reduced. In addition, it has been confirmed that an additional reduction in the bearing stiffness can be obtained for given fixed machined clearances by decreasing the preloads, i.e., by increasing the assembled clearances.

• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.110-112
• /
• 2006

본 논문에서는 전동기의 경부하진동으로부터 자유로운 새로운 범용인버터를 제안된다. 제안된 범용인버터의 V/f 제어 기법은 벡터방식에 근거하며 전통적인 V/f 제어 기법과는 약간 다른 방식의 제어 기법이다. 제안된 범용인버터의 V/f 제어 기법은 V/f 제어 유도전동기 드라이브 시스템의 안정도를 향상시키기 위하여 다이나믹 전류보상기를 이용한다. 제안된 시스템이 이론적으로 설명되며 그 성능은 실험결과를 통하여 보인다.

• Proceedings of the Korea Contents Association Conference
• /
• 2012.05a
• /
• pp.365-366
• /
• 2012

본 연구는 교각운동시 불안정한 지지면과 안정적인 지지면을 제공하여 체간 및 하지의 근 활성도의 변화를 알아보고자 하였다. 이 연구의 대상자는 20대 남, 여 14명이었다. 실험방법은 일반적 교각자세와 다이나믹 에어쿠션을 이용한 교각자세를 실시한 후에 무선 8채널 표면근전도 검사기를 이용하여 체간부의 척추기립근, 복직근, 대퇴의 대퇴직근, 외측 슬괵근, 하퇴부의 전경골근, 비복근 외측두에서 근활성 정도를 측정하였다. 체간부의 척추 기립근, 대퇴이두근, 가자미근은 불안정한 지지면에서 근활성도가 높게 나타났다(p<.05). 따라서, 교각운동에서 불안정한 지지면의 제공은 신체의 배측에 위치한 근육의 활성화를 나타내어, 교각운동시 지지면의 안정성의 변화만으로도근육활성도의 변화가 가능함을 알 수 있었다.