• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.129-133
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• 1994

Presented are closed-form expressions of the steady-state solution for the three-state exponentially correlated acceleration(ECA) target-tracking filter. The steady-state solution is derived based on Vaughan's approach for the case that the measurements of target position and velocity are available at discrete points in time. The solution for the ECA filter using only position measurements is obtained as a special case of the presented results.

• Smart Structures and Systems
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• v.17 no.6
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• pp.903-915
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• 2016

The classical Kalman filter (KF) provides a practical and efficient state estimation approach for structural identification and vibration control. However, the classical KF approach is applicable only when external inputs are assumed known. Over the years, some approaches based on Kalman filter with unknown inputs (KF-UI) have been presented. However, these approaches based solely on acceleration measurements are inherently unstable which leads poor tracking and so-called drifts in the estimated unknown inputs and structural displacement in the presence of measurement noises. Either on-line regularization schemes or post signal processing is required to treat the drifts in the identification results, which prohibits the real-time identification of joint structural state and unknown inputs. In this paper, it is aimed to extend the classical KF approach to circumvent the above limitation for real time joint estimation of structural states and the unknown inputs. Based on the scheme of the classical KF, analytical recursive solutions of an improved Kalman filter with unknown excitations (KF-UI) are derived and presented. Moreover, data fusion of partially measured displacement and acceleration responses is used to prevent in real time the so-called drifts in the estimated structural state vector and unknown external inputs. The effectiveness and performance of the proposed approach are demonstrated by some numerical examples.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.629-636
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• 2003

This paper introduces the developed geometry PIG (Pipeline Inspection Gauge), one of several ILI (In-Line Inspection) tools, which provide a full picture of the pipeline from only single pass, and has compact size of the electronic device with not only low power consumption but also rapid response of sensors such as calipers, IMU and odometer. This tool is equipped with the several sensor systems. Caliper sensors measure the pipeline internal diameter, ovality and dent size and shape with high accuracy. The IMU (Inertial Measurement Unit) measures the precise trajectory of the PIG during its traverse of the pipeline. The IMU also provide three-dimensional coordination in space from measurement of inertial acceleration and angular rate. Three odometers mounted on the PIG body provide the distance moved along the line and instantaneous velocity during the PIG run. The datum measured by the sensor systems are stored in on-board solid state memory and magnetic tape devices. There is an electromagnetic transmitter at the back end of the tool, the transmitter enables the inspection operators to keep tracking the tool while it travels through the pipeline. An experiment was fulfilled in pull-rig facility and was adopted from Incheon LT (LNG Terminal) to Namdong GS (Governor Station) line, 13 km length.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.806-811
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• 2007

The derailment is defined as phenomena in which the wheels run off the rail due to inordinate lateral force generated when wheel flange contacts with the rail. Derailment coefficient is typical standard assessing running safety and derailment. The traditional method measuring by strain gage adhered to wheels is very complicated and easy to fail. It also requires too much cost and higher measurement technique. Therefore it can hardly ensure safety because we can't confirm at which time we need to identify safety. In this paper, we principally researched the method measuring easily wheel load generated by contacts between wheel flange and the rail, and lateral force. Correlation of vibration and displacement which was related physical amounts of wheel load and lateral force, was investigated and analyzed through analysis, experiment and measurement. And it is presents new measurement method of derailment coefficient which can estimate derailment possibility only by movement of vibration and displacement, by which we understand the rate for acceleration and displacement to contribute wheel load and lateral force and compare actual data of wheel load and lateral force measured from wheel.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1046-1048
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• 2003

Recently, various researches in respect of the positioning technologies using satellites and the other sensors have made location-based services (LBS) more common and accurate. Consequently, concern about position information has been increasing. However, since these positioning systems only focus on user's position, it is difficult to know the user's attitude or detailed behaviors at the specific position. It is worthy to study on how to acquire such human attitude or behavior, because those information is useful to know the context of the user. In this paper, the sensor unit consisting of three dimensional accelerometer was attached to human body, and autonomously measured the perpendicular acceleration of ordinary human behaviors including activity modes such as walking, running, and transportation mode using transportation such as a train, a bus, and an elevator. Subsequently, using the classified measurement results, the method to identify the human activity modes was proposed.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.303-310
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• 2011

This paper is focused on development of models for measuring lateral and vertical track irregularities from corresponding accelerometers of an in-service high-speed train. Generally, the track irregularity was measured by a special railway inspection vehicle or system with contact or non-contact sensors. However, the sensors are very expensive and vulnerable to a harsh environment. Displacement estimation from an inertial measurement unit and its wave-band filtering was already developed in the previous study, and it was found that their results included not only the track irregularities but also other information such as phase delay of the applied filters, and suspension and conicity of the wheel. To identify the track irregularities from those results, a compensation filtering method was proposed. Each directional compensation filter was derived by using a system identification method with the estimated directional displacement as input and the corresponding track irregularities as output. In this paper, they are integrated into a model for each direction and applied to the measured lateral and vertical acceleration data from the axle-box and bogie of an in-service high-speed train. Their results are compared with the data from the track geometry measurement system. From the comparison, the proposed models are a useful tool for the measurement of the track irregularities using accelerometers of in-service high-speed trains.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8516-8524
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• 2015

Track irregularities can be evaluated not only directly by track inspection but also indirectly by measurement of carbody accelerations and many researches are being conducted. Carbody accelerations were measured on the Kyeongbu high speed railway and France high speed line to investigate the situation of the track maintenance at Korea high speed line by using indirect method. Digital signal processing for the measured acceleration data were conducted according to UIC518 code. Since the vehicle speed affects the car body acceleration, the lateral and vertical acceleration of the car body were classified according to the vehicle speed and the distribution characteristics of these acceleration were investigated and evaluated by UIC518 criteria. Finally, the running behavior of KTX on Korea high speed railway were compared with that on France. Distribution characteristics of these acceleration were evaluated and discussed in terms of the track maintenance in Korea high speed line.

• Smart Structures and Systems
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• v.4 no.3
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• pp.319-342
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• 2008

Identification of the nonlinear hysteretic behavior of a reinforced concrete (RC) bridge pier subjected to earthquake loads is carried out based on acceleration measurements of the earthquake motion and bridge responses. The modified Takeda model is used to describe the hysteretic behavior of the RC pier with a small number of parameters, in which the nonlinear behavior is described in logical forms rather than analytical expressions. Hence, the modified extended Kalman filter is employed to construct the state transition matrix using a finite difference scheme. The sequential modified extended Kalman filter algorithm is proposed to identify the unknown parameters and the state vector separately in two steps, so that the size of the problem for each identification procedure may be reduced and possible numerical problems may be avoided. Mode superposition with a modal sorting technique is also proposed to reduce the size of the identification problem for the nonlinear dynamic system with multi-degrees of freedom. Example analysis is carried out for a continuous bridge with a RC pier subjected to earthquake loads in the longitudinal and transverse directions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.129-138
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• 2007

In this paper, a modified sensitivity control for the semi-active suspension system with a magneto-rheological (MR) damper is investigated. A 2-d.o.f quarter-car model together with a 6th order polynomial model for the MR damper is considered. For the purpose of suppressing the vertical acceleration of the sprung mass, the square of the vertical acceleration is defined as a cost function and a modified sensitivity control that updates the current input in the negative gradient of the cost function is proposed. The implementation of the proposed algorithm requires only the measurement of the relative displacement of the suspension deflection. The local stability of equilibria of the closed loop nonlinear system is proved by investigating the eigenvalues of the linearized ones. Through simulations, the passive suspension, the skyhook control, and the proposed modified sensitivity control are compared.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.185-195
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• 1998

This experiment carried out in order to investigate the effect of the chemical activators for acceleration of hydration the system of Fly ash-Cao The paste was consisted of 80wt% Fly ash and 20wt% CaO with 1. 3. 5wt% of 4 activators(N{{{{ alpha _2 }}S{{{{ OMICRON _4 }}, CaC{{{{ {l }_{2 } }}, NaOH, Ca(N{{{{ OMICRON _3 {)}_{2 } }} and W/S ratio of 0.42 After curing for 1, 3, 7, 14, 28 days the paste hydration was characterized by the measurement of compressive strength XRD analysis SEM observation the combined water and the reaction amount of Ca(OH)2 determination. As a result of this ex-periment all of the system which involved Na2SO4 or NaOH had a god compressive strength. In the case of 7 days curing a system which added CaCl2 showed the highest compressive strength among all especially NaOH system showed a high increase in strength as a dosage of it increased. Hydration products were different according to activatores added. Only C-S-H was observed in NaOH system. As the reaction amount of Ca(OH)2 and combined water were increased the compressive strength increased. There were few differences in the comparision of strength between ignited loss 3.1% and loss 9.3% of fly ash.