• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.939-950
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• 1992

The performance of common spreading code scheme employing multiple-capture receiver is compared to that of transmitter-oriented (T/O) code division multiple access (CDMA) scheme in view of the possibility of collision-free transmissions and the effect of secondary multiple-access interference. For performance comparisons, secondary multiple-access interference is characterized for the common code scheme and the T/O CDMA scheme that assures perfectly collision-free transmissions. Throughput performance is then evaluated for these two schemes with direct-sequence spread-spectrum/differential-phase-shift-keying (DS-SS/DPSK) data modulation and forward-error-control coding (BCH codes) in the presence of an additive white Gaussian noise (AWGN). It is shown that when the number of radios is relatively large, the maximum normalized throughput is greater for the common code scheme than for the T/O CDMA scheme at a moderate signal-to-noise ration(SNR).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.37-43
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• 2009

Reliability should be assured to support the stable ubiquitous sensor network services in wireless sensor networks. Data transmission reliability is the most important one in the reliability factors in USN. When we consider the wireless communication environment of sensor networks, data transmission reliability requires the performance improvement. For this, this paper introduces the method that can handle the reliability and the performance together. The proposed scheme uses the self relay signal between sensor nodes to deliver the ACK and the next data is scheduled to be sent on acceptance of this self relay signal. For the evaluation of the performance improvement, the analysis and the simulation have been done.

• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.367-373
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• 1994

It is necessary to adopt a simple signal validation for avoiding the complexity of algorithm and verification in the design process of the instrumentation and control system in nuclear plants. This paper suggests a signal validation method developed on the basis of consistency checking for the multi-channel measurement system without any analytic process model. It includes a simplified algorithm for estimating the fixed bias error of each channel and a weighted averaging method. The weighting factor of each channel is updated according to its calculated bias error. The developed method has been tested to verify its performance through several input scenarios.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1090-1100
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• 2017

This paper presents the comparison of starting current characteristics of a three-phase induction motor fed by two types of soft starters. The first soft starter under investigation is a conventional AC voltage controller on the basis of a phase-control technique. The other is the proposed asynchronous PWM AC chopper which is developed from the conventional synchronous PWM AC chopper. In this paper, the proposed asynchronous PWM AC chopper control scheme is developed by generating only two asynchronous PWM signals for a three-phase main power circuit (6 switching devices) from a single voltage control signal which is compared with a single sawtooth carrier signal. By this approach, the PWM signals are independent and easy to implement since the PWM signals do not need to be synchronized with a three-phase voltage source. Details of both soft starters are discussed. The experimental and simulation results of the starting currents are shown. It is found that the asynchronous PWM AC chopper efficiently works as a suitable soft starter for the three-phase induction motor due to that the starting currents are reduced and are sinusoidal with less harmonic contents, when being compared with the starting current waveforms using the conventional phase-control starting technique. Also the proposed soft starter offers low starting electromagnetic torque pulsation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.187-192
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• 2004

In this paper, it is presented a new technique to the design and real-time implementation of fuzzy control system based-on digital signal processors in order to improve the precision and robustness for system of industrial robot. Fuzzy control has emerged as one of the most active and fruitful areas for research in the applications of fuzzy set theory, especially in the real of industrial processes. In this thesis, a self-organizing fuzzy controller for the industrial robot manipulator with a actuator located at the base is studied. A fuzzy logic composed of linguistic conditional statements is employed by defining the relations of input-output variable of the controller, In the synthesis of a FLC, one of the most difficult problems is the determination of linguistic control rules from the human operators. To overcome this difficult, SOFC is proposed for a hierarchical control structure consisting of basic level and high level that modify control rules. The proposed SOFC scheme is simple in structure, fast in computation, and suitable for implementation of real-time control. Performance of the SOFC is illustrated by simulation and experimental results for robot with eight joints.

• Journal of Power Electronics
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• v.7 no.3
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• pp.213-221
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• 2007

A digital state feedback control method for the current mode control of DC-DC converters is proposed in this paper. This approach can precisely achieve interleaved current sharing among the converter modules. As the controller design and system analysis are performed in the time domain, the proposed method can easily satisfy the required converter specification by using the pole placement technique. The digital state feedback controller in the continuous and discrete time domain is derived for the robust tracking control. For the verification of the proposed control scheme, a parallel module bi-directional converter in a prototype 42V/14V hybrid automotive power system, which is a design example in the continuous time domain, and a parallel module buck converter, which is a design example in the discrete time domain, are implemented using a TMS320F2812 digital signal processor (DSP).

• The Journal of Korea Robotics Society
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• v.19 no.2
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• pp.139-148
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• 2024

In this paper, we propose a two-degree-of-freedom snake robot head system and an I-PID (Intelligent Proportional-Integral-Derivative)-based controller utilizing RBF (Radial Basis Function) neural network and adaptive robust terms as a control strategy to reduce rotation occurring in the snake robot head. This study proposes a two-degree-of-freedom snake robot head system to avoid complex snake robot dynamics. This system has a control system independent of the snake robot. Subsequently, it utilizes an I-PID controller to implement a control system that can effectively manage rotation at the snake robot head, the robot's nonlinearity, and disturbances. To compensate for the time delay estimation errors occurring in the I-PID control system, an RBF neural network is integrated. Additionally, an adaptive robust term is designed and integrated into the control system to enhance robustness and generate control inputs responsive to signal changes. The proposed controller satisfies stability according to Lyapunov's theory. The proposed control strategy was tested using a 9-degreeof-freedom snake robot. It demonstrates the capability to reduce rotation in Lateral undulation, Rectilinear, and Sidewinding locomotion.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.6
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• pp.84-90
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• 1982

In this paper we exploit the use of the intermittent property of speech to reduce the transmission rate or to increase signal-to-quantization noise ratio (SQNR) in coding speech by hybrid companding data modulation (HCDM). In this scheme we detect silence in speech by a speech/silence discriminator. HCDM coding is done only for speech portion. For silence that is detected in evert block of 5 ms, only the information indicating that the Since the HCDM coder transmits bina교 signal synchronously at a fixed rate, the use of a buffer and its efficient control is essential. By using the HCDM with silence detection in coding speech, we could improve SONR by as much as 6 dB over the conventional HCDM or reduce the transmission rate by one third of the HCDM rate.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.603-605
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• 1996

The SLIM used in the conveyance system has been generally developed the controller based on the slip frequency control and the VVVF method to obtain the quick response for the position control signal. This paper deals with the trust control of the SLIM by vector control with Bang-Bang condition. Also, the control system is composed of the PI controller for soft start of the SLIM and the q-axis current controller for correction in phase with Space Vector for reducing the harmonic pulsation in low speed. The processing for vector control and robust dynamic breaking control is carried out by MC80196KC micro processor and IGBT module. The proposed scheme is verified through the computer simulation and experiments for the 10KW SLIM.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.201-206
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• 2003

In this paper, it is presented a new technique to the design and real-time implementation of fuzzy control system based-on digital signal processors in order to improve the precision and robustness for system of industrial robot. Fuzzy control has emerged as one of the most active and fruitful areas for research in the applications of fuzzy set theory, especially in the real of industrial processes. In this thesis, a self-organizing fuzzy controller for the industrial robot manipulator with a actuator located at the base is studied. A fuzzy logic composed of linguistic conditional statements is employed by defining the relations of input-output variable of the controller, In the synthesis of a FLC, one of the most difficult problems is the determination of linguistic control rules from the human operators. To overcome this difficult, SOFC is proposed fir a hierarchical control structure consisting of basic level and high level that modify control rules. The proposed SOFC scheme is simple in structure, fast in computation and suitable for implementation of real-time control. Performance of the SOFC is illustrated by simulation and experimental results for robot with eight joints.