• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.339-341
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• 2006

This paper presents a new method on controller design of brushless dc motors. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. To suppress the current ripples the current controller is generally used. To minimize the size and the cost of the drives it is desirable to control motors without the current controller and the current sensing circuits. To estimate the motor current it is modeled by a neural network that is configured as an output-error dynamic system. The identified model is essentially a one step ahead prediction structure in which fast inputs and outputs are used to calculate the current output. Using the model, effective estimator to compensate the effects of disturbance has been designed. The effectiveness of the proposed current estimator is verified through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.93.5-93
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• 2001

In chaos control proposed until today, the target system is known in many cases. However, since the generating mechanism of chaos is not strange in few case, it is required to control only by the time series data observed from the system. Then, as the method of stabilizing the state of the unknown system, we propose the technique made combining PFC and DFC using a parameter which indicates the balance of both methods. The prediction values at the PFC input portion are determined from the known output using RNN. The input is impressed only near UPO calculated from the output using the concept of UPR.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.16-20
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• 2002

This paper describes the resistive FET mixer with low IF for the 4-Ch DBF(Digital Beam Forming) receiver with LNA(Low Noise Amplifier). This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(IF) considered in this research are 2.09 ㎓, 2.08 ㎓ and 10㎒, respectively. The RF input power, LO input power and Vgs are used -10㏈m, 6㏈m and -0.4 V, respectively. In the 4-Ch resistive FET mixer with LNA, the measured IF and harmonic components of 10㎒, 20㎒, 2.09㎓ and 4.17㎓ are about -12.5 ㏈m, -57㏈m, -40㏈m and -54㏈m, respectively. The IF output power observed at each channel of 10㎒ is about -12.5㏈m and it is higher 27.5 ㏈m than the maximum harmonic component of 2.09㎓. Each IF output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.15-26
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• 1998

Full car model is needed for investigating as a entire dynamics of vehicle. In this study, 7DOF of full car model's dynamics is selected. This paper proposes the output feedback controller based on optimal control theory. Input data and output data from the optimal controller are used for neural network system identification of the suspension system. To do system identification, neural network which has robustness against nonlinearities and disturbances is adapted. This study uses back-propagation algorithm to train a multil-layer neural network. After obtaining a neural network model of a suspension system, a neuro-controller is designed. Neuro-controller controls suspension system with off-line learning method and multistep ahead prediction model based on the neural network model and a neuro-controller. The optimal controller and the neuro-controller are designed and then, both performances are compared through. For simulation, sinusoidal and rectangular virtual bumps are selected.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.4
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• pp.30-42
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• 1986

On the analysis of cutting mechanics in orthogonal cutting, each cutting force component can be predicted. By adding the flank face wear term to the prediction equation for cutting force components, complete equations are obtained. Using these equations, it is shown that cutting force components are increased linearly as flank face wear land is developed, in theory and experiment. By making non-dimensional term ie. Fv/Fc, the width of variation of output signal Fv/Fc is greately decreased compared with each cutting force component as cutting condition is varied. Among these conditions, the variation of chip width in the range of more than 1mm and that of cutting velocity have little effect on the output signal Fv/Fc, that of Flank face werr land can be detected without difficulty.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.5
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• pp.812-820
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• 1995

This paper proposes an approach of identifying nonlinear mappings from input/output data. The approach is based on the universal approximation by the fuzzy integration of local affine mappings. A connectionist model realizing the universal approximator is suggested by using a processing unit based on both the radial basis function and the weighted sum scheme. In addition, a learning method with self-organizing capability is proposed for the identifying of nonlinear mapping relationships with the given input/output data. To show the effectiveness of our approach, the proposed model is applied to the function approximation and the prediction of Mackey-Glass chaotic time series, and the performances are compared with other approaches.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.344-349
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• 1990

Under the assumption that process input/output data are sufficiently rich to allow reasonable plant identification, a long-range predictive control method for SISO bilinear plant is derived. In order to ensure offset-free behaviour of the control method, a new bilinear CARIMA model with variable dead-time is introduced. Furthermore, to extend the maximum output prediction horizon, the future predicted outputs in the bilinear term are assumed to be equal to the known future set-points. With a classical recursive adaptation algorithm, the proposed control scheme is capable of stable control of bilinear plants with variable parameters, with variable dead-time, and with a model order which changes instantaneously. Several simulation results demonstrate the characteristics of the proposed bilinear model predictive control method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1200-1209
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• 2010

The main subject of this paper is to develop analytic method with which output power or sensitivity variations of a magnetostrictive ultrasonic transducer can be estimated with no aid of experiments. After the bias magnetic field deployed over the patch is calculated using finite element analysis for magnetostatics, the representative value is extracted by averaging these field values. The operating point on the characteristic curve for magnetostriction is identified by this value and then the output performance is calculated from it. It is verified that the results from this simple model match well with those of its experimental version and some limits of this modeling technique are also considered.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.243-249
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• 2005

To improve the ride comfort and handling characteristics of a vehicle, an active suspension which is controlled by external actuators can be used. An active suspension can control the vertical acceleration of a vehicle and the tire deflection to achieve the desired suspension goal. For this purpose, Model Predictive Control (MPC) scheme is applied with the assumption that the preview information of the oncoming road disturbance is available. The predictive control approach uses the output prediction to forecast the output over a time horizon and determines the future control over the horizon by minimizing the performance index. The developed method is applied to a half car model of four degrees-of-freedom and numerical simulations show that the MPC controller improves noticeably the ride qualities and handling performance of a vehicle.

• ETRI Journal
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• v.29 no.1
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• pp.89-94
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• 2007

A mathematical model for the input-output characteristic of an amplifier exhibiting gain expansion and weak and strong nonlinearities is presented. The model, basically a Fourier-series function, can yield closed-form series expressions for the amplitudes of the output components resulting from multisinusoidal input signals to the amplifier. The special case of an equal-amplitude two-tone input signal is considered in detail. The results show that unless the input signal can drive the amplifier into its nonlinear region, no gain expansion or minimum intermodulation performance can be achieved. For sufficiently large input amplitudes that can drive the amplifier into its nonlinear region, gain expansion and minimum intermodulation performance can be achieved. The input amplitudes at which these phenomena are observed are strongly dependent on the amplifier characteristics.