• Speech Sciences
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• v.13 no.1
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• pp.117-128
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• 2006

The two-channel Generalized Sidelobe Canceller (GSC) scheme suffers from the presence of leakage signal in the reference channel. The leakage signal is caused by the dissimilar impulse responses between microphones, and different paths from speech source to microphones. Such leakage is detrimental to speech enhancement of the GSC since the desired reference signal becomes corrupted. In order to suppress the signal leakage, two matrix injection methods are proposed. In the first method, a simple gain compensation matrix is used. In the second, a projection matrix for reducing the error between the actual and the ideal primary and reference signals, is used. This paper describes the performance degradation resulting from leakage, and proposes effective methods to resolve the problem. Representative experiments were conducted to demonstrate the effectiveness of the proposed methods on recorded speech and noise in an actual automobile environment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1388-1394
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• 2018

In this paper, the improvement of the control response by using the error compensator to improve the stability of the control in the power conversion system is verified. Typically a closed loop control method is used to improve the control response characteristics in a traditional power conversion system and this is accomplished by generating a PWM waveform. In this paper, the newly constructed Type3 compensator to overcome the existing such as PI controller or Type2 compensator has been developed to improve the control stability of these closed loop control systems and the effectiveness of the use of error compensation devices was verified by presenting technique to improve stability and select its parameters by expanding the range of phase gains. Stability improvements are shown by the extension of the phase gain range and parameter selection techniques and the effects of using the error compensation device are verified accordingly.

• Journal of Ocean Engineering and Technology
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• v.13 no.3B
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• pp.99-105
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• 1999

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers a robust stability of this 2DOF servosystem with nonlinear type uncertainty in the system, and a robust stability condition for the servosystem is introduced. This result guarantees that if the plant uncertainty is in the permissible set defined by the condition, gain tuning can be carried out to suppress the influence of the plant uncertainties and disturbance inputs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.8
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• pp.857-864
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• 2010

In this paper, we analyse the effect of the path imbalances(gain and phase mismatches) in LINC(LInear amplification with Nonlinear Component) system, and propose a simple scheme using LUTs(Look Up Table) to compensate the path imbalances. The EVM(Error Vector Magnitude) and ACPR(Adjacent Channel Power Ratio) of the LINC system are degraded significantly by the path imbalances because it adopts an outphasing technique. The EVM and ACPR are theoretically extracted for two variables(gain and phase mismatch factors) and 2-D LUTs for those are generated based on the analysis. The efficient and simple compensation scheme for the path imbalances is proposed using the 2-D LUTs. A LINC system with the suggested compensation scheme is implemented, and the proposed method is verified with an experiment. A 16-QAM signal with 1.5 MHz bandwidth is used. Before the compensation, the path gain ratio was 95 % and phase error was $19.33^{\circ}$. The proposed scheme adjusts those values with 99 % and $0.5^{\circ}$, and improves ACPR about 18.1 dB.

• Journal of Power Electronics
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• v.5 no.2
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• pp.151-159
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• 2005

The errors generated from current measurement paths are inevitable, and they can be divided into two categories: offset error and scaling error. The current data including these errors cause periodic speed ripples which are one and two times the stator electrical frequency respectively. Since these undesirable ripples bring about harmful influences to motor driving systems, a compensation algorithm must be introduced to the control algorithm of the motor drive. In this paper, a new compensation algorithm is proposed. The signal of the integrator output of the d-axis current regulator is chosen and processed to compensate for the current measurement errors. Usually the d-axis current command is zero or constant to acquire the maximum torque or unity power factor in the ac drive system, and the output of the d-axis current regulator is nearly zero or constant as well. If the stator currents include the offset and scaling errors, the respective motor speed produces a ripple related to one and two times the stator electrical frequency, and the signal of the integrator output of the d-axis current regulator also produces the ripple as the motor speed does. The compensation of the current measurement errors is easily implemented to smooth the signal of the integrator output of the d-axis current regulator by subtracting the DC offset value or rescaling the gain of the hall sensor. Therefore, the proposed algorithm has several features: the robustness in the variation of the mechanical parameters, the application of the steady and transient state, the ease of implementation, and less computation time. The MATLAB simulation and experimental results are shown in order to verify the validity of the proposed current compensating algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1901-1905
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• 2004

A controller designed by CDM for a servo type system which is an augmented system constructed from a rotational inverted pendulum with an integrator added to its arm, is presented in this paper. In order to be able to apply the CDM concept, the augmented system must be linearized and converted into controllable canonical form. Then, the controller consisting of the state feedback gain matrix and an integral gain in the sense of CDM can be obtained. This shows that design procedure for the proposed controller is easy. The experimental results obtained from the rotational inverted pendulum controlled by the proposed controller show that the system response has no steady-state error, however, the oscillation amplitude of the arm angle is still significant. Therefore, in this paper, the friction compensation using Coulomb friction with stiction is also added to the controller. The oscillation amplitude of the arm angle that can be reduced remarkably is also shown in the experimental results.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.3
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• pp.289-297
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• 2014

This paper proposed a novel high performance sensorless control scheme for IPMSM based on an extended nonlinear state observer. The gain-matrix of the observer has been derived by using state linearization method. Steady state errors in estimated rotor position and speed due to parameter inaccuracy have been analyzed, and an equivalent flux error is defined to represent the overall effect of parameter errors contributing to the wrong convergence of the estimated rotor speed as well as rotor position. Then, an online compensation strategy was proposed to limit the estimation errors in rotor position and speed. The effectiveness of the extended nonlinear state observer is validated through simulation and experimental test.

• Journal of IKEEE
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• v.26 no.2
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• pp.299-305
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• 2022

Analog-digital converter (ADC) should be one of the most important blocks that convert various physical signals to digital ones for signal processing in the digital signal domain. As most operations of the analog circuit for sensor signal processing have been replaced by digital circuits, high-resolution performance is required for ADC. In addition, low-power must be the critical issue in order to extend the battery time of mobile system. The existing integrating sigma-delta ADCs has a characteristic of high resolution, but due to its low supply voltage condition and advanced technology, circuit error and corresponding resolution degradation of ADC result from the finite gain of the operational amplifier in the integrator. Buffer compensation technique can be applied to minimize gain errors, but there is a disadvantage of additional power dissipation due to the added buffer. In this paper, incremental signal-delta ADC is proposed with buffer switching scheme to minimize current and igh-pass bias circuit to improve the settling time.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.5
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• pp.470-477
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• 1990

Singh's multi-level method is extended to the optimal tracking control of a large interconnected dynamical system which has coupled states and coupled inputs. The steady-state tracking error and a convergence condition for the extended multi-level method are derived analytically and the results show that the steady-state tracking error and a convergence rate have to be compromised. Also, a new multi-level method which is advantageous over the Singh's method in steady-state tracking error and computational burden is proposed by introducing nominal inputs into the performance index. The resulting feedback gain matrix and the compensation vector are optimal for all initial conditions so that eventual on-line computation is minimal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1205-1213
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• 2006

In this paper, we analyze the IQ(In-phase/Quadrature) imbalance effects at both transmitter and receiver side of OFDM(Orthogonal Frequency Division Multiplexing) and show that IQ imbalance is the parameter to improve the performance using ML and OSIC scheme. Especially, we can archive the diversity gain due to the IQ imbalance in multipath fading environment. In addition, new preamble format is proposed, which enable estimation of the channel and IQ imbalance parameters to maximize the diversity gain. Significant performance improvement is achieved by using the ML(Maximum Likelihood)and OSIC(Ordered Successive Interference Cancellation) with compensation compared to a standard receiver with no compensation for IQ imbalance and proposed channel estimation scheme achieves the better performance improvement than conventional.