• Journal of Institute of Control, Robotics and Systems
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• v.17 no.6
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• pp.573-578
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• 2011

We propose a switching-based adaptive state feedback controller for a class of nonlinear systems that have uncertain nonlinearity. The base of the proposed conditions on the nonlinearity is the feedforward form, then it is extended via a nonlinear function containing all the states and the control input. As a result, more generalized systems containing feedforward and nonfeedforward terms are allowed as long as the ratio condition of the nonlinear function is satisfied. Moreover, the information on the growth rate of nonlinearity is not required a priori in our control scheme.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.108-112
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• 2003

A feedforward amplifier, which is composed of several components, is an open loop system. Therefore, feedforward amplifiers are apt to deteriorate the performance according to the environmental changes even though the cancellation performance and the linearization bandwidth of feedforward systems are superior to other linearization methods. A control method is needed for maintaining the original performance of feedforward amplifiers or to keep the performance within a little error bounds. In this paper, an adaptive control method, which has a good convergence characteristic and is easy to implement, is suggested. The characteristics of the suggested control method compare with the characteristics of other control methods and the simulation results are presented.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1176-1185
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• 2005

A linear power amplifier is particularly emphasized on the system using a linear modulations, such as 16QAM and QPSK with pulse shaping, because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance, a phase imbalance and a delay mismatch, are briefly analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for IMT-2000 frequency band. The center frequency of the feedforward amplifier is 2140 MHz with 60 MHz bandwidth. When the average output power of feedforward amplifier is 20 Watt, the intermodulation cancellation performance is more than 21 dB. In this case, the output power of feedforward amplifier reduced 3.5 dB because of extra delay line loss and coupling loss. The feedforward amplifier efficiency is more than 7.2 % for multicarrier signals, 59 dBc for ACPR.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.864-867
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• 2003

In this study, a controller which has a feedforward controller and two additional PI integrators was designed. But if a controller is used by only the integration of a feedforward controller and two additional PI integrators, the capability of a controller will decrease because the decoupling terms of current is feedback as the disturbance. Therefore the feedforward method with the decoupling compensation was proposed. The two additional PI integrators were replaced by two decoupling terms to simplify the calculation. The simulation and experimental using SynRM driving system were performed to verify the design of a improved decoupling feedforward controller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.725-731
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• 2006

A novel design of frequency multiplier using a feedforward technique and a defected ground structure(DGS) is proposed. The feedforward loop in the proposed frequency multiplier suppresses the fundamental component $(f_0)$, the dumb-bell or spiral shaped DGS diminish unwanted harmonics such as second, third and fourth. Due to the combination of the feedforward structure and the DGS, only the multiplied frequency component$(2f_0,\;3f_0,\;4f_0)$ appears at the output port and the other unwanted components are suppressed excellently. The frequency multiplier is designed at 1 GHz $(f_0)$, by the proposed technique and measured. The measured output power of $2f_0,\;3f_0$ and $4f_0$ is -2.59 dBm, -5.36dBm and -4.57dBm, respectively, when the input power is 0dBm.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.345-348
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• 2000

In this paper, A Feedforward Linear Power Amplifier for IMT-2000 which IMD characteristics was improved was designed and fabricated. To improve the main power amplifier IMD characteristics, the Feedback loop was added to basic Feedforward Power Amplifier structure. Therefore, the output power of error amplifier can be reduced, and it is easy to control the linearization circuit to cancel total IMD. The designed power amplifier represented the 40㏈m(l0W) output power and -55㏈C 3rd IMD at Center frequency 2.14㎓ (@5㎒).

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.715-717
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• 1999

본 논문에서는 feedforward 선형 증폭기에서의 지연 불일치에 의한 효과를 최소화하기 위한 등화기의 차수 결정에 관하여 수학적 접근과 모의실험을 하였다. 현재 feedforward 선형 증폭기에서 주로 사용하는 vector modulator는 지연 불일치에 확실한 개선을 이루지 못하고 있다. 이것을 극복하고자 vector modulator를 등화기로 대체하고 증폭기와 시지연선의 최대시간불일치와 sampling frequency와의 관계로 등화기의 차수를 결정하여 지연 불일치에 의한 오류 제거능력을 향상시켰다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.4
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• pp.355-361
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• 1992

In this paper, some rules for auto- tuning of feedback-feedforward controller in variable load and disturbance are presented. The parameters of feedback PID controller are determined by heuristic rules based on input regulation experiment, and the parameters of feedforward controller are determined by result rules based on spectral factorization, minimum variance, and polynomial equation. These heuristic and result rules are used as an element of the feedback loop in an auto-tuning feedback-feedforward controller. The robust and accurate control performance is demonstrated by computer simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.399.2-399
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• 2002

This paper concerns on a non-rotating single-DOF beam-active magnetic bearing(AMB) system subject to arbitrary shaped base motion. In such a system, it is desirable to retain the beam within the predetermined air-gap under foundation excitation. Motivated form this, an adaptive acceleration feedforward control is proposed to reduce the base motion response without deteriorating other feedback control performances. Experimental results demonstrate the effectiveness of the acceleration feedforward control.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.24-24
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• 2000

This paper proposes a design method of sliding mode observer for SISO linear systems with a disturbance input. We first construct an observer with a constant gain matrix, a feedforward injection map and an external feedforward compensation signal input. Using the second Lyapunov method, we present a sufficient condition for the existence of sliding mode observer. The proposed observer guarantees that the state error trajectories enter a certain region in finite time and remain inside thereafter.