• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1796-1803
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• 2006

This Paper describes a systematic method for designing the $H_{\infty}$ controller for the inverted pendulum which is a nonlinear and single-input double-outputs system. In particular, the open-loop system is conbined with a pre-filter to shape the open-loop transfer function for the sensitivity function ind the complementary sensitivity function to be kept the desirable frequency characteristics. Consequently, the loop shaping technique of the open-loop transfer function reduces the impacts of the model uncertainties, measurement noises and exogenous disterbances on the dynamic characteristics of the inverted pendulum. The results of simulation and experiment show the efficiency of the proposed control method comparing with conventional PID control method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.207-213
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• 2006

In our previous research, we proposed a robust saturation controller which involves both control input saturation and structured real parameter uncertainties. This controller can analytically prescribed the upper and lower bounds of parameter uncertainties, and guarantee the closed-loop robust stability of the system in the presence of actuator's saturation. And the availability and the effectiveness of the proposed robust saturation controller were verified through numerical simulations. In this paper, we verify the robust stability of this controller through experimental tests. Expecially, we show unstable cases of other controllers in comparison with this controller. Experimental tests are carried out in the laboratory using a two-story test structure with a hydraulic-type active mass damper.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1767-1768
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• 2008

본 논문의 목적은 선회구동장치의 최단시간으로 외란 및 시스템 불확실성에 강인한 구동을 위한 최단시간 강인제어기를 설계하는 것이다. 먼저 선회구동장치의 시스템 식별을 통해 플랜트의 전달함수를 유도하고 얻어진 전달함수를 이용하여 High-gain PDC와 RNTOC의 스위칭 함수를 정의한다. 그리고 각각의 제어 법칙을 적용하여 제어기를 설계한다. 두 제어기의 제어 성능을 시뮬레이션 및 실험으로 입증한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.63-71
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• 2003

This paper presents a robust slewing control of a flexible space structure based on sliding surface design. A sliding surface is designed for a single-axis rest-to-rest slewing in view of target angle, target angular velocity, and root monent of the flexible appendage. In comparison with the Lypunov control law, both controllers guarantee the stability and command tracking capabilities for nominal system. It is also shown that the designed control law provides further robustness to internal/external uncertainties. Extending the results of a single-axis maneuver, a sliding mode control law was sought for an arbitrary three-axis maneuver. Quaternion was used to determine the attitude of a space structure and sliding surfaces were designed for each axis, thereby a robust control law was derived considering the coupling effects between each rotational axis during the maneuver. Several numerical examples were demonstrated to show the effectiveness of the designed control law.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1950-1951
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• 2011

본 논문에서는 요구되는 성능을 만족시키는 최적 Fuzzy PI 제어의 정압제어로의 효율적인 적용 및 성능 향상을 위하여 유전자 알고리즘(GA: Genetic Algorithm)을 이용한 제어 설계 방법을 제시 한다. PID제어기는 이해가 쉽고 구조가 간단하여, 실제 구현이 용이하여 공정 산업분야에서 가장 널리 사용되고 있는 제어기 이다. 따라서 단일 입 출력 선형 시스템 에서는 우수한 성능을 보이나 동적 시스템, 고차 시스템 및 수학적 모델 선정이 어려운 시스템에서는 비효율 적이다. 반면, Fuzzy 제어기는 인간의 지식과 경험을 이용한 지적 제어방식으로 IF-THEN형식의 규칙으로부터 제어 입력을 결정하는 병렬형 제어기이다. 이는 과도상태에서 큰 오버슈트 없이 설정치에 도달하게 하는 속응성과 강인성이 좋은 제어기법으로 비선형성이 강하고 불확실하며 복잡한 시스템을 쉽게 제어 할 수 있다는 장점을 지닌다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.805-814
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• 2013

A hydraulic dipod platform is used for tracking and stabilizing an antenna system to designate a satellite on a moving vehicle. The 2-DOF controller is very well suited to this controller design object because it is more flexible than the 1-DOF controller when the design object is not only the consideration between stabilizing and tracking but also the trade-off between performance and robustness. The 2-DOF controller synthesis based on the $H_{\infty}$ framework is divided into two design procedures. In this hydraulic dipod platform example, the single-step method shows better performance whereas the two-step method shows better robustness. The difference between these two synthesis results is compared using the structural property of the interconnection system matrix.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.8-15
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• 2010

This paper proposes a robust high-gain observer design scheme for nonlinear systems and its stability is analyzed based on Lyapunov theory. It is assumed that their states are unmeasurable. The proposed high-gain observer has the integrator of the estimation error in dynamics. It improves the performance of high-gain observers and makes the proposed observer robust to noisy measurements, uncertainties and peaking phenomenon as well. Its stability is analyzed by the Lyapunov approach. In order to verify the effectiveness of the proposed scheme, it is applied to output feedback controllers and some comparative simulation result with the existed observer based output feedback controllers and state feedback controllers is given.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.183-190
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• 2007

In this paper, a robust controller for PWM converter is proposed. The proposde converter controller consists of a PI controller for DC output voltage and a current controller using error-space approach for maintaining the sinusoidal current waveform and unity power factor. Conventionally, the try and error method has been used to design the current controller considering the switching frequency of the devices and sampling frequency of the digital controller. But this proposed method is based on characteristic ratio assignment(CRA) method which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. First, the CRA based current controller algorithm is explained. Then the validity of proposed controller is verified through the PSiM simulation and experience results.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.73-74
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• 2008

이 논문은 두 개의 질량을 가진 미소 감쇄 시스템에 대해 외란 관측기 기반 추종 제어기의 강인성을 증가시키는 새로운 감쇄 주입법(damping injection)을 제시한다. '미소 감쇄'란 감쇄 계수가 다른 파라미터들과 비교해서 매우 작다는 것을 의미한다. 파라미터에 불확실성을 가진 미소 감쇄 시스템에 대한 외란 관측기의 적용은 전체 시스템을 불안정성하게 할 수 있다는 것을 관측할 수 있기에, 외란 관측기의 구조 중 공칭 (Nominal) 모델에 인위적으로 더 많은 감쇄를 추가함으로써 강인성을 강화시키는 방법을 제안한다. 또한 강인 제어 이론의 제로 익스클루젼(zero exclusion) 정리를 이용하여 감쇄 주입법의 안정성을 증명하고 시뮬레이션과 실험을 수행하였다.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.12
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• pp.1231-1237
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• 2014

This paper proposes a reduced-order disturbance observer based coordinated tracking controller for uncertain heterogeneous multi-agent systems. To this end, first the control problem is converted as a robust control problem. Then, a dynamic coordinated controller is designed based on the recently proposed reduced-order disturbance observer. Simulation results are given to show the effectiveness of the proposed control scheme.