• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.170-178
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• 2005

The purpose of this study is to develop a gait-event detection system, which is necessary for the cycle-to-cycle FES control of locomotion. Proposed gait event detection system consists of a signal measurement part and gait event detection part. The signal measurement was composed of the sensors and the LabVIEW program for the data acquisition and synchronization of the sensor signals. We also used a video camera and a motion capture system to get the reference gait events. Machine learning technique with ANN (artificial neural network) was adopted for automatic detection of gait events. 2 cycles of reference gait events were used as the teacher signals for ANN training and the remnants ($2\sim5$ cycles) were used fur the evaluation of the performance in gait-event detection. 14 combinations of sensor signals were used in the training and evaluation of ANN to examine the relationship between the number of sensors and the gait-event detection performance. The best combinations with minimum errors of event-detection time were 1) goniometer, foot-switch and 2) goniometer, foot-switch, accelerometer x(anterior-posterior) component. It is expected that the result of this study will be useful in the design of cycle-to-cycle FES controller.

• International Journal of Fluid Machinery and Systems
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• v.8 no.4
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• pp.264-273
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• 2015

This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and two Francis model test turbines all at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that two to three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.

• Journal of the Korea Society of Computer and Information
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• v.23 no.8
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• pp.1-7
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• 2018

Previous test equipment was bulky, took a long time to check, and was somewhat less economical. Since most of the checks were about analog signals, we preferred to check them using reference equipments. In this paper, a digital circuit design based on AITS is used to implement signals that can not utilize commercial measurement resources, and also designed and manufactured equipment that can inspect SRU. These test equipments were tested and evaluated by development, operation, and field evaluation, and they were installed to the Korean Field Force. This contributed to the improvement of operability by shortening the inspection time from 83.2 minutes to 7.8 minutes on average In addition, it did not utilize the reference equipment, so it could play a big role in lowering the mass production cost.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1111-1118
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• 2003

We present one-color nonlinear wavepacket interferometry (WPI) signal calculations for a system of two electronic levels and one vibrational degree of freedom. We consider two cases, a displaced harmonic oscillator system, which can be treated analytically, and a model photodissociative system, whose WPI signal must be calculated by numerical wavepacket propagation. We show how signals obtained with different combinations of intrapulse-pair phase shifts can be combined to isolate the complex-valued overlap between a given onepulse target wavepacket and a variable three-pulse reference wavepacket. We demonstrate that with a range of inter- and intrapulse-pair delays the complex overlaps and variable reference states can be used to reconstruct the target wavepacket. We compare our results with previous methods for vibronic state reconstruction based on linear WPI and discuss further generalizations of our method.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.138-146
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• 2001

The guided missile carries its own tracking radar to detect its target under noisy environments. The enemy warship uses the anti-missile electric-countermeasure(ECM) technique, such as chaff or decoy, so that the approaching guided missile could not destroy it. In this paper we propose the identification algorithm of a target signal when the enemy warship uses the chaff and decoy to deceive the guided missile. In the proposed scheme the mean square errors(MSE) between the received signals and the reference decoy signal, and between the received signals and the reference chaff signal are calculated. Then, the received signal which results in the maximum MSE is regarded as a warship signal. The performance of the proposed algorithm is verified through the computer simulation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.93-97
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• 2005

This paper proposes a design of stepper motor control in microstep driven mode using FPGA (Field Programmable Gate Array) for hardware implementation. The methods to drive stepper motor in microstep excitation mode are to control of the controlling currents in each phase windings of stepper motor with reference signals. These reference signals are used for controlling the current levels, the required variation of current levels with rotor position can be obtained from the ideal linear or sinusoidal approximations to the static torque-displacement ($T-{\theta}$) characteristic curve. In addition, the hardware implementation of stepper motor controller can be designed uses VHDL (Very high speed integrated circuits Hardware Description Language) and synthesis using an Altera FPGA, FLEX10K family, EPF10K20RC240-4 device as target technology and use MAX+PlusII program for overall development. A multi-stack variable-reluctance stepper motor of Sanyo Denki is used in the experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1038-1040
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• 2016

This paper introduces a fine timing synchronization based on reference signals. The proposed method first estimates a channel impulse response (CIR), and acquires the timing offset based on the change point of statistics of the estimated CIR. It is confirmed that the proposed estimator can significantly improve the fine timing synchronization performance compared to conventional schemes over diverse channel environments.

• Steel and Composite Structures
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• v.19 no.1
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• pp.131-152
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• 2015

Easy detection and evaluation of defect in the tube structure is a continuous problem and remains a significant demand in tube inspection technologies. This study is aimed to automate defect detection using the pattern recognition approach based on the classification of high frequency stress wave signals. The stress wave signals from vibrational impact excitation on several tube conditions were captured to identify the defect in ASTM A179 seamless steel tubes. The variation in stress wave propagation was captured by a high frequency sensor. Stress wave signals from four tubes with artificial defects of different depths and one reference tube were classified using the autoregressive (AR) algorithm. The results were demonstrated using a dendrogram. The preliminary research revealed the natural arrangement of stress wave signals were grouped into two clusters. The stress wave signals from the healthy tube were grouped together in one cluster and the signals from the defective tubes were classified in another cluster. This approach was effective in separating different stress wave signals and allowed quicker and easier defect identification and interpretation in steel tubes.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.686-692
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• 2016

A Crimp Force Monitor (CFM) is equipment for detecting crimp errors by analyzing crimp signals obtained from force and strain sensors. The analysis is commonly performed by aligning a measured crimp signal with a reference signal and comparing their difference. Current analysis methods often suffer from wrong alignments that result in false negative detections. This paper presents a new crimp signal analysis method in CFM. First, a falling edge alignment is proposed that matches falling edges of the measured and the reference signals by minimizing the absolute difference summation. Second, a signal parameter error is introduced to evaluate the crimp quality difference between the measured signal and the reference. For calculating the signal parameter error, part of a signal is identified and divided into several regions to maximize the signal parameter errors. Experiments showed that the proposed method can improve the signal alignment and accurately detect bad crimps especially with the strain sensor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.431-436
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• 2000

Adaptive feed forward control algorithms based largely upon LMS approach have developed in recent two decades, and they have been widely applied to practical sound and vibration control problems in the case of the reference signal is available. Feedforward control can be applied only when reference signals can be measured or regenerated, while feedback controllers are used to reduce; sound and vibration when reference signals are not available. In recent years, hybrid control schemes in which adaptive feed forward controllers are combined with feedback ones have been studied based on simulations and experiments. The results have shown that the hybrid control may have better control performances in convergence speed and steady state error than the single control schemes. Hybrid control has the advantages of improving stability and performance as well as the disturbance rejection property. However, little effort has been made to the analysis or interpretation of hybrid control systems. In this study, we discussed the feedback controller effects on the stability of feed forward control algorithm in the presence of uncertain error path and a simple example showed that a stable feedback controller could make the feedforward controller unstable. A design criterion of feedback controllers is proposed in order to guarantee the stability of feedforward algorithms in the presence of error paths with uncertainties.