• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1228-1230
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• 1992

The permanent magnet synchronous motor(PMSM) is receiving Increased attention for servo drive applications in recent years because of its high torque to inertia ratio, superior power density and high efficiency. By vector-controll method, PMSM has the same operating characterics as seperately excited dc motor. The drive system of servo motor is requested to have an accurate response for the reference input and a quick recovery for the disturbance such as load torque. However, when the unknown disturbances and parameter variations are imposed on the permanent magnet synchronous motor(PMSM), the drive system is significantly effected by them. As a result, the drive system with both a fast compensation and a robustness to a parameter variations is requested. This paper investigates the possibility of applying the fuzzy logic controller(FLC) using Multi-Rule Base In a servo motor control system. In this paper, The five Rule Bases(1 to 5) are selected to recover the state error caused by the disturbance in steady state. In the initial operating mode. Rule Base 0 is used. To show the validity of the proposed fuzzy logic controll system, the computer simulation results are provided.

• Smart Structures and Systems
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• v.6 no.2
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• pp.115-133
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• 2010

A modal filter is a tool used to extract the modal coordinates of each individual mode from a system's output. This is achieved by mapping the response vector from the physical space to the modal space. It decomposes the system's responses into modal coordinates, and thus, on the output of the filter, the frequency response with only one peak corresponding to the natural frequency to which the filter was tuned can be obtained. As was shown in the paper (Deraemecker and Preumont 2006), structural modification (e.g. a drop in stiffness or mass due to damage) causes the appearance of spurious peaks on the output of the modal filter. A modal filter is, therefore, a great indicator of damage detection, with such advantages as low computational effort due to data reduction, ease of automation and lack of sensitivity to environmental changes. This paper presents the application of modal filters for the detection of stiffness changes. Two experiments were conducted: the first one using the simulation data obtained from the numerical 7DOF model, and the second one on the experimental data from a laboratory stand in 4 states of damage.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1199-1205
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• 1993

It has been well known that the assumption of full state availability is one of the most important restrictions to the practical realization of VSCS. And several attempts to alleviate the assumption had been made. However, it is not easy to find a positive scheme among them. Recently, an output feedback variable structure control system(OFVSCS) was proposed and the effectiveness of the scheme was validated for the disturbance free systems. The purpose of this study is to propose a robust OFVSCS that have the robust properties against process parameter variations and external distrubances by extending the basic OFVSCS and to evaluate its control performances through power system stabilizer design example. The ROFVSCS is composed of dynamic switching function and output feedback switching control inputs that are constructed by the use of the unknown vector modeling technique. With the proposed scheme, existence of sliding mode is guaranteed and any nonzero bias can be suppressed in the face of disturbances and process parameter variations as far as well-known matching condition is satisfied. Due to the fact that the ROFVSCS is driven by small number of measured informations, the practical application of VSCS for the systems with unmeasurable states and for high order systems that conventional schemes cannot be applied, is possible with the proposed scheme. It is noticeable that the implementation cost of VSCS can be considerably reduced without sacrifice of control performances by adopting ROFVSCS since there is no need measure the states with high measurement cost.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.71-80
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• 1996

Sattering problem of electromagnetic waves by periodic strip grating with two dielectrics over a ground plane in case of oblique incidence and arbitrary polarization is analyzed by the vector floquet mode expansion method and the moment mehtod from the viewpoint of soft and hard boundary value problem. To confirm proposed analysis methods, we examine the solution convergence for the scattering problem. And some numerical results of artificially soft and hard surfaces using the structure filled with single dielectric slab between periodic strip grating and gorund plane is compared with previous results. Some interesting results for soft and hard surfaces using periodic strips loaded with two layered dielectric slabs over a ground plane are given.

• Journal of Power Electronics
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• v.17 no.1
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• pp.67-75
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• 2017

Due to the excessive zero-sequence voltage in dual three-level inverter fed open-end winding induction motor systems, zero-sequence circumfluence which is harmful to switching devices and insulation is then formed when operating in a single DC voltage source supplying mode. Traditionally, it is the mean value instead of instantaneous value of the zero-sequence voltage that is eliminated, through adjusting the durations of the operating vectors. A new strategy is proposed for zero-sequence voltage elimination, which utilizes unified voltage modulation and a decoupled SVPWM strategy to achieve two same-sized equivalent vectors for an angle of $120^{\circ}$, generated by two inverters independently. Both simulation and experimental results have verified its efficiency in the instantaneous value elimination of zero-sequence voltage.

• Journal of Korean Association for Spatial Structures
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• v.4 no.3 s.13
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• pp.103-109
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• 2004

The lowest load when the equilibrium condition becomes to be unstable is defined as the buckling load. The primary objective of this paper is to be analyse stability boundaries for star dome under combined loads and is to investigate the iteration diagram under the independent loading parameter. In numerical procedure of the geometrically nonlinear problems, Arc Length Method and Newton-Raphson iteration method is used to find accurate critical point(bifurcation point and limit point). In this paper independent loading vector is combined as proportional value and star dome was used as numerical analysis model to find stability boundary among load parameters and many other models as multi-star dome and arch were studied. Through this study we can find the type of buckling mode and the value of buckling load.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.454-457
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• 1997

The purpose of this study is to develop an optimal model, using existing models, that is able to estimate the amount of spatter utilizing artificial neural network in the short circuit transfer mode of gas metal arc (GMA) welding. The amount of spatter generated during welding can become a barometer which represents the process stability of metal transfer in GMA welding, and it depends on some factors which constitute a periodic waveforms of welding current and arc voltage in short circuit GMA welding. So, the 12 factors, which could express the characteristics for the waveforms, and the amount of spatter are used as input and output variables of the neural network, respectively. Two neural network models to estimate the amount of spatter are proposed: A neural network model, where arc extinction is not considered, and a combined neural network model where it is considered. In order to reduce the calculation time it take to produce an output, the input vector and hidden layers for each model are optimized using the correlation coefficients between each factor and the amount of spattcr. The est~mation performance of each optimized model to the amount of spatter IS assessed and compared to the est~mation performance of the model proposed by Kang. Also, through the evaluation for the estimation performance of each optimized model, it is shown that the combined neural network model can almost perfectly predict the amount of spatter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1332-1340
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• 2009

The front end wheel loader is widely used for the loading of materials in mining and construction fields. It has repetitive digging, loading and dumping procedures. The bucket is subjected to large resistance force from the soil during scooping. We considered the soil reaction force characteristics from scooping procedure, the protection by overload and automatic scooping mode algorithm. The main topic of this paper is the analysis of the soil reaction force characteristics. The analysis of soil mechanics is carried out and the developed soil model is verified by experimental results from the simplified experimental equipment. A simplified model of the soil shape and bucket trajectory is used to determine the scooping direction based on an estimation of the resistance force applied on the bucket during the scooping motion. In the future, this model will be used for the generation of an appropriate path for the wheel loader automation.

• The Journal of the Acoustical Society of Korea
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• v.13 no.1E
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• pp.89-95
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• 1994

This paper describes development of a real-time voice dialing system which can recognize around one hundred word vocabularies in speaker independent mode. The voice recognition algorithm in this system is implemented on a DSP board with a telephone interface plugged in an IBM PC AT/486. In the DSP board, procedures for feature extraction, vector quantization(VQ), and end-point detection are performed simultaneously in every 10 msec frame interval to satisfy real-time constraints after detecting the word starting point. In addition, we optimize the VQ codebook size and the end-point detection procedure to reduce recognition time and memory requirement. The demonstration system has been displayed in MOBILAB of the Korean Mobile Telecom at the Taejon EXPO'93.