• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.440-445
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• 2012

Contact-type Linear Encoder-like Capacitive Displacement Sensor (CLECDiS) is a novel displacement sensor which has wide measurable range with high resolution. The sensor, however, is very sensitive to relative rotational alignment between stator and mover of the sensor as well as its displacement. In addition to, there can be some disturbances in the relative rotational alignment, so some noises occur in the sensor's output signal by the disturbances. This negative effect of the high sensitivity may become larger as increasing sensitivity. Therefore, this negative effect of the high sensitivity has to be compensated and reduced to achieve nanometer resolution of the sensor. In this study, a new type capacitive linear encoder with a mechanical guide is presented to reduce the relative rotational alignment problem. The presented method is not only to reduce the alignment problem, but also to assemble the sensor to the stage conveniently. The method is based on a new type CLECDiS that has mechanical guide autonomously. In the presented sensor, when the device is fabricated by micro-machining, the guide-rail is also fabricated on the surface of the sensor. By the direct fabrication of the guide-rail with high precision micro-machining, errors of the guide-rail can be reduced significantly. In addition, a manual yaw alignment is not required to obtain large magnitude of the output signal after the assembly of the sensor and the stage. The sensor movement is going to follow the guide-rail automatically. The prototype sensor was fabricated using the presented method, and we verify the feasibility experimentally.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.330-338
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• 2011

Odometry is the critical factor to estimate the location of the robot. In the mobile robot with wheels, odometry can be performed using the information from the encoder. However, the information of location in the encoder is inaccurate because of the errors caused by the wheel's alignment or slip. In general, visual odometer has been used to compensate for the kinetic errors of robot. In case of using the visual odometry under some robot system, the kinetic analysis is required for compensation of errors, which means that the conventional visual odometry cannot be easily applied to the implementation of the other type of the robot system. In this paper, the novel visual odometry, which employs only the single camera toward the ground, is proposed. The camera is mounted at the center of the bottom of the mobile robot. Feature points of the ground image are extracted by using median filter and color contrast filter. In addition, the linear and angular vectors of the mobile robot are calculated with feature points matching, and the visual odometry is performed by using these linear and angular vectors. The proposed odometry is verified through the experimental results of driving tests using the encoder and the new visual odometry.

• Phonetics and Speech Sciences
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• v.13 no.1
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• pp.45-51
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• 2021

End-to-end (E2E) automatic speech recognition (ASR) has achieved promising performance gains with the introduced self-attention network, Transformer. However, due to training time and the number of hyperparameters, finding the optimal hyperparameter set is computationally expensive. This paper investigates the impact of hyperparameters in the Transformer network to answer two questions: which hyperparameter plays a critical role in the task performance and training speed. The Transformer network for training has two encoder and decoder networks combined with Connectionist Temporal Classification (CTC). We have trained the model with Wall Street Journal (WSJ) SI-284 and tested on devl93 and eval92. Seventeen hyperparameters were selected from the ESPnet training configuration, and varying ranges of values were used for experiments. The result shows that "num blocks" and "linear units" hyperparameters in the encoder and decoder networks reduce Word Error Rate (WER) significantly. However, performance gain is more prominent when they are altered in the encoder network. Training duration also linearly increased as "num blocks" and "linear units" hyperparameters' values grow. Based on the experimental results, we collected the optimal values from each hyperparameter and reduced the WER up to 2.9/1.9 from dev93 and eval93 respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.3
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• pp.111-119
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• 2006

The ultra-precision stage is demanded for some industrial fields such as semiconductor lithography, ultra-precision machining, and fabrication of nano structure. A new stage was developed for those applications in order to obtain nano meter resolution. This stage consists of symmetric double parallelogram mechanism using flexure hinges. The mechanical properties such as strength of the flexures and deformations along the applied force were analyzed using FEM. The stage is actuated by a piezoelectric actuator and its movement was measured by a ultra-precision linear encoder. In order to improve positioning performance, a PID controller was designed based on the identified second order transfer function. Experimental results showed that this stage could be positioned within below 5 nm resolution irrespective of hysteresis and creep by the controller.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.54-59
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• 2005

Recently, the ultra-precision stage is widely used in the fields of the nano-technology, specially in AFMs(Atomic Force Microscope) and STMs(Scanning Tunneling Microscope). In this paper, the ultra-precision stage which consists of flexure hinges, piezoelectric actuator, and ultra-precision linear encoder, is designed and developed. The guide mechanism which consisted of flexure hinges is analyzed by Finite Element Method. And we derived the transfer function of the system in 1st order system from step responses according to the magnitude. We performed simulation for the model to tune the control gain and applied the gains to the developed system. Experimental results found that the stage can be controlled in 5 nm resolution by PID controller.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.898-900
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• 2001

In general, the accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. But the region of high speed, switching angles are fluctuated back and forth from the preset values, which are cause by the sampling period of the microprocessor. Therefore, the low cost linear encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple analog type switching logic circuit is also presented in this paper.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.279-280
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• 2011

In order to convert the mechanical movement of a linear generator to electrical power, the amateur current of the generator is controlled in accordance to the mover position. A linear encoder, usually used for direct detection of the mover position, not only is vulnerable to mechanical vibration, but also imposes significant constraint on the mechanical design of the generator system. Thus, this study proposes a method for indirect estimation of the mover position with emfs induced in amateur coils. The estimation algorithm is validated with simulation study.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.315-317
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• 2003

This paper deals with the position control of an AC servo motor using linear hall-effect sensors. The price of these is very low, but it is possible to make position control of motor similar to a control using an encoder. This paper introduces the design of motor using linear hall-effect sensors and shows the results of control.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.33-41
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• 2022

In this article, we proposed to predict natural gas (NG) leakage levels through feature selection based on a factor analysis (FA) of the integrating the Korean Meteorological Agency data and natural gas leakage data for considering complex factors. The paper has been divided into three modules. First, we filled missing data based on the linear interpolation method on the integrated data set, and selected essential features using FA with OrdinalEncoder (OE)-based normalization. The dataset is labeled by K-means clustering. The final module uses four algorithms, K-nearest neighbors (KNN), decision tree (DT), random forest (RF), Naive Bayes (NB), to predict gas leakage levels. The proposed method is evaluated by the accuracy, area under the ROC curve (AUC), and mean standard error (MSE). The test results indicate that the OrdinalEncoder-Factor analysis (OE-F)-based classification method has improved successfully. Moreover, OE-F-based KNN (OE-F-KNN) showed the best performance by giving 95.20% accuracy, an AUC of 96.13%, and an MSE of 0.031.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.50-53
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• 2002

There are increasing needs to deliver the multimedia streaming over heterogeneous networks. When considering network environments and equipment accessed by user, delivery of video streaming must be scalable. There are many kinds of scalable video coding: spatial, temporal, SNR, and hybrid. The SNR scalable and spatial resolution, but different SNR quality with respect to layers. The 1-layer SNR scalable encoder produces SNR scalable video streams with ease. But, there is drift problem. Modified 1-layer approach does not have this problem but coding inefficiency, and is not MPEG-compliant. The present MPEG-compliant 2-layer encoder comes out to reduce coding rate. But it still use only base layer to encode whole layer. In this paper, we propose adaptive MPEG-compliant 2-layer encoder. Using linear combination algorithm, encoder use 1 motion vector to encode the sequences efficiently. By dong this, we can achieve the coding efficiency of SNR scalable coding.