• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.643-650
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• 2017

The control of flexible joint robot is getting more attentions because its applications are more frequently used for robot systems in these days. This paper proposes a robust impedance controller for the flexible joint robot by using integral sliding mode control and backstepping control. The sliding mode control decouple disturbances completely but requires matching condition for disturbances. The dynamic model of flexible joint robot is divided into motor side and link side and the disturbance of the link side does not satisfy matching condition and cannot be decoupled directly by the actual input in the motor side. To overcome this difficulty, backstepping control technique is used with sliding mode control. The mismatched disturbance in the link side is changed into matched one in the respect to virtual control input which is the state controlled by actual input in the motor side. Integral sliding mode control is used to preserve the impedance control performance and the improved robustness at the same time.

• Journal of the Ergonomics Society of Korea
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• v.32 no.4
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• pp.333-340
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• 2013

Objective: The aim of this study is to provide a current knowledge of the multiple issues regarding motion effects on crew performance. Background: The motions of the ship may create motion sickness, nausea and vomit. Also, these motions also disturb the balance of crew members, increase the energy expenditure of crew for shipboard work, and result in increased levels of injury and fatigue. However, the motion effects of the ship on crew performance has not been thoroughly investigated. Method: Participants(N=10) were engaged in an experiment in 2 experimental environments(training ship and ship handling simulator) and 2 navigational conditions(day and night). The COP(Center of Pressure) data were recorded as an objective measure of postural balance control and the SSQ(Simulator Sickness Questionnaire) was used as a subjective measure of sickness. Results: The results showed that COP has a no significant difference based on experimental environments, but significant effect on SSQ. Conclusion: During the virtual simulator navigation, subjects showed significant SSQ level changes, which included decreased SSQ data. But, there is no significant difference of COP between training ship and ship handling simulator. Application: The results of this study could be applied to the next generation of ship design to decrease effect of motion at sea and to increase performance of ship crew.

• Publications of The Korean Astronomical Society
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• v.27 no.3
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• pp.95-103
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• 2012

We analyzed the current status of the telescope control system (TCS2) of the 1.8 m telescope in Bohyunsan Optical Astronomy Observatory (BOAO), and suggest a new TCS (TCS3) for the long term development of BOAO. The TCS2 was constructed in 1998 to replace the TCS1 which was installed with the telescope itself at the commencement of BOAO. One of the important parts of TCS is PMAC (Programmable Multi-Axis Controller), which is a general-purpose multi-axis motion controller. PMAC provides the direct interactive communication environment permitting users to command the controller directly with simple operations. This makes the setup, debugging, and diagnostics very easy. The TCS2 was operated stable for a long time, but the hardware and TCS computers have been deteriorated and are out of date now. The new TCS3 needs to be constructed based on a modern computer system. And functions such as pre-calculations of telescope limiting position, interworking with virtual observatory tools, and using GUI, etc should be added. Construction of the TCS3 will be a step creating a better observation environment for the Korean astronomical society.

• Journal of Korea Society of Industrial Information Systems
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• v.28 no.6
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• pp.1-10
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• 2023

The nuclear power plant(NPP)'s Instrumentation and Control(I&C) system periodically conducts integrity checks for the maintenance of self-diagnostic function during normal operation. Additionally, it performs functionality and performance checks during planned preventive maintenance periods. However, there is a need for technological development to diagnose failures and prevent accidents in advance. In this paper, we studied methods for estimating the reliability function by utilizing environmental data and self-diagnostic data of the I&C equipment. To obtain failure data, we assumed probability distributions for component features of the I&C equipment and generated virtual failure data. Using this failure data, we estimated the reliability function using representative artificial intelligence(AI) models used in survival analysis(DeepSurve, DeepHit). And we also estimated the reliability function through the Cox regression model of the traditional semi-parametric method. We confirmed the feasibility through the residual lifetime calculations based on environmental and diagnostic data.

• Information Systems Review
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• v.26 no.2
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• pp.83-93
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• 2024

This study proposes a preprocessing methodology based on Dynamic Time Warping (DTW) and k-Nearest Neighbors (kNN) to effectively represent time series data for predicting the completion quality of electroplating baths. The proposed DTW-based kNN preprocessing approach was applied to various regression models and compared. The results demonstrated a performance improvement of up to 43% in maximum RMSE and 24% in MAE compared to traditional decision tree models. Notably, when integrated with neural network-based regression models, the performance improvements were pronounced. The combined structure of the proposed preprocessing method and regression models appears suitable for situations with long time series data and limited data samples, reducing the risk of overfitting and enabling reasonable predictions even with scarce data. However, as the number of data samples increases, the computational load of the DTW and kNN algorithms also increases, indicating a need for future research to improve computational efficiency.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.94-105
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• 2008

Numerous platforms have been developed for ZigBee-based network embedded systems. Also, operating systems like TinyOS have been installed to facilitate efficient implementation of wireless sensor network applications which collect data, and/or execute commands. First of all, porting an operating system on a new platform may need invention of a substitute for a required but unsupported hardware component. This paper presents a multiplexed virtual system timer for a platform without a counter comparator which we have contrived to emulate by using an extra counter. Such porting also injects unexpected faults which cause a variety of painful failures. Unfortunately, TinyOS requires to handle a lot of asynchronous hardware interrupts which are hard to trace during debugging. Besides, simulators are not available for a new platform since the models of hardware on the platform are not usually developed, yet. We propose novel instrumentation techniques which can be used to effectively trace the bugs in such lack of debugging environment. These techniques are used to identify and fix a great deal of nasty issues in porting TinyOS 2.0 on MG2400 and MG2455 platforms made by RadioPulse Inc.