• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.672-674
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• 2004

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.1
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• pp.1-5
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• 2007

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.118-124
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• 1998

This paper describes a relationship of a space vector PWM and a sinusoidal PWM and presents that the space vector PWM can produce linearly the output voltage to the unity MI(modulation index). At first, reference angles and holding angles are derived from expanding a Fourier series of the reference voltage waveform and then the angles are used for the inverter switching to linearize transfer characteristics of the inverter. In addition, the harmonic components of the output voltage are analyzed and on-line control is shown to be feasible by approximating in piecewise-linearization the reference and holding angles versus the MI. In V/f control of the induction motor, it is verified by the experiment that the motor current is changed smoothly for the variation of the inverter input voltage and the change of the reference voltage.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.401-406
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• 2004

In this paper, a new time-domain adaptive predistortion scheme is proposed to compensate for the nonlinearity of high power amplifiers (HPA) in OFDM systems. A complex Wiener-Hammerstein model (WHM) is adopted to describe the input-output relationship of unknown HPA with linear dynamics, and a power series model with memory (PSMWM) is used to approximate the HPA expressed by WHM. By using the PSMWM, the compensation input to HPA is calculated in a real-time manner so that the linearization from the predistorter input to the HPA output can be attained even if the nonlinear input-output relation of HPA is uncertain and changeable. In numerical example, the effectiveness of the proposed method is confirmed and compared with the identification method based on PSMWM.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.58-62
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• 2002

This paper proposes a new nonlinear controller to swing-up an inverted pendulum system mounted on a car. This controller considers not only the pendulum but also the displacement of the cart. A single-input multi-output system is considered to control the inverted pendulum by using partial feedback linearization and nonlinear additional input. The asymptotic stability of the system is shown by using Lyapunov function. The simulation results show effectiveness of the proposed controller.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.123-128
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• 1998

This paper proposes design of LFT-based fuzzy controllers for model-following, which are better than the previous input-output linearization controllers, which are not able to follow the model system states and which do not guarantee the stability of all states. The method proposed in this paper provides a LFT-based Takagi-Sugeno(T-S) fuzzy controller with guaranteed stability and model-following via the following steps: First, using LFT(Linear Fractional Transformation) and T-S fuzzy model, controllers, are obtained. Next, error dynamics are obtained for model-following, and errors go to 0(zero). Finally, a T-s fuzzy controller that can stabilizxe the system with the requirement on the control input satisfied is obtained by solving the LMIs with the MATLAB LMI Control Toolbox and a model-following controller is obtained. Simulations are performed for the LFT-based T-S fuzzy controller designed by the proposed method, which show better performance than the results of input-out ut linearization controller.

• Journal of IKEEE
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• v.9 no.1 s.16
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• pp.72-78
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• 2005

This paper describes the design of a robust output-feedback controller for a single-input single-output nonlinear dynamical system with a full relative degree. While all the previous research works on the output-feedback control are based on dynamic observers, a new state estimator which uses the past values of the measurable system output is proposed. We name it backward-difference state estimator since the derivatives of the output are estimated simply by backward difference of the present and past values of the output. The disturbance generated due to the error between the estimated and real state variables is compensated using an additional robustifying control law whose gain is tuned adaptively. Overall control system guarantees that the tracking error is asymptotically convergent and that all signals involved are uniformly bounded. Theoretical results are illustrated through a simulation example of inverted pendulum.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.325-328
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• 2002

In this paper, we proposed that the problem of controlling induction motor with magnetic saturation is studied from an input-output feedback linearization with adaptive algorithm. The $\pi$-model of induction motor is considered. An adaptive input-output feedback linearizing controller is considered under the assumption of known motor parameters and unknown load torque. Simulation results are provided for illustration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.505-507
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• 2004

This paper attempts to compensate the nonlinearity between the input voltage and the output displacement of the piezoelectric stack in dynamic actuation by the following two ways. Firstly, the charge steering by circuit configuration reduces the hysteresis of piezoelectric actuator remarkably. However, it makes the ripple in positioning due to the phase lag and noise induced from the elements of the long closed loop. Secondly, the feedforward control by neural network compensates the hysteresis of the piezoelectric actuators effectively with the appropriate selection of the input variables for the training. The improvement of the dynamic performance of the piezoelectric actuators by the developed linearization technique is verified by experiments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.723-730
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• 2007

This paper shows how the ACLR of power amplifier can be reduced by using Anti-phase IMD linearization technique which generate anti-phase IMD in the driver stage compare to output stage's IMD. And design process proposed. From the experimental result of W-CDMA 4FA input signal, this amplifier has ACLR -55 dBc@5 MHz offset at 30 watts average power. Compare to optimum matching technique to get maximum power gain, this technique has been improved ACLR by 12 dBc. Also this amplifier meets 50 watts average output power amplifier specification in domestic market.