• 전력전자학회논문지
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• 제10권5호
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• pp.468-480
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• 2005

서보 시스템의 전체 제어 성능은 기계적 상수의 변화와 부하 토크의 영향을 크게 받는다. 그러므로 서보 시스템의 성능을 향상시키기 위해서는 기계적 상수와 부하 토크를 정확히 알 필요가 있다. 본 논문에서는 Support Vector Regression(SVR)을 이용한 기계적 상수와 부하 토크 추정 알고리즘을 제안한다. 실험 결과는 제안된 SVR 알고리즘이 서보 시스템의 기계적 상수와 부하 토크를 정확하게 추정하고 있음을 보여준다.

• Wind and Structures
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• 제21권3호
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• pp.311-329
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• 2015

A method for analyzing the coupled wind-vehicle-bridge system is proposed that also considers the shielding effect of the bridge tower with triangular wind barriers. The static wind load and the buffeting wind load for both the bridge and the vehicle are included. The shielding effects of the bridge tower and the triangular wind barriers are incorporated by taking the surface integral of the wind load. The inter-history iteration is adopted to solve the vehicle-bridge dynamic equations with time-varying external loads. The results show that after installing the triangular wind barriers in the area of the bridge tower, the bridge response and the vehicle safety factors change slightly. The peak value of the train car body acceleration is significantly reduced when the wind barrier size is increased.

• 대한임베디드공학회논문지
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• 제19권3호
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• pp.123-130
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• 2024

This paper proposes an EMPC (Explicit Model Predictive Controller) for temperature tracking control based on heat load prediction by an ESO (Extended State Observer) for a variable cooling circulation system with multiple indoor units connected to one outdoor unit. In this system, heat transfer and heat loss relative to the input temperature are modeled using system dynamics. Using this model, we design an EMPC based on an ESO that is robust to temperature changes and depends on airflow. To determine the stability of both the controller and the observer, asymptotic stability is verified through Lyapunov stability analysis. Finally, to validate the performance of the proposed controller, simulations are conducted under three scenarios with varying airflow, set temperature, and heat load.

• Smart Structures and Systems
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• 제11권4호
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• pp.349-364
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• 2013

Recently, researchers in the field of structural health monitoring (SHM) have been rigorously striving to replace the conventional NDE techniques with the smart material based SHM techniques, employing smart materials such as piezoelectric materials. For instance, the electromechanical impedance (EMI) technique employing piezo-impedance (lead zirconate titanate, PZT) transducer is known for its sensitivity in detecting local damage. For practical applications, various external factors such as fluctuations of temperature and loading, affecting the effectiveness of the EMI technique ought to be understood and compensated. This paper aims at investigating the damage monitoring capability of EMI technique in the presence of axial stress with fixed boundary condition. A compensation technique using effective frequency shift (EFS) by cross-correlation analysis was incorporated to compensate the effect of loading and boundary stiffening. Experimental tests were conducted by inducing damages on lab-sized aluminium beams in the presence of tensile and compressive forces. Two types of damages, crack propagation and bolts loosening were simulated. With EFS for compensation, both cross-correlation coefficient (CC) index and reduction in peak frequency were found to be efficient in characterizing damages in the presence of varying axial loading.

• 한국생산제조학회지
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• 제25권4호
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• pp.245-252
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• 2016

Girth gears are applied in the mining, cement, and mineral processing industries and used in various types of horizontal mills, rotary dryers and kilns, and other heavy-gear ring applications. The large ring gears are normally fitted outside mills or kilns to provide the primary rotational drive. Recently, an external pinwheel gear set (e-PGS) was introduced to overcome manufacturing problems associated with girth gears. e-PGS is also suitable for low-speed, heavy-duty mechanical transmission and dusty and poor-lubrication conditions. This paper first presents a new profile modification of root relief for the e-PGS cam pinion. We then investigate load-stress factors to estimate the surface fatigue life by varying the shape design parameters. The results show that the contact fatigue life of an e-PGS can be extended significantly by increasing the profile shift coefficient. However, support bearing life of the pinwheel depends more on the contact force distribution than the profile shift coefficient.

• Computers and Concrete
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• 제27권3호
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• pp.199-210
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• 2021

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.134-144
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• 2017

This paper presents an adaptive control strategy for the speed control of a four-phase switched reluctance motor (SRM) in automotive applications. The main objective is to minimize the torque ripples, despite the unstructured uncertainties, time-varying parameters and external load disturbances. The bound of perturbations is not required to be known in the developing of the proposed adaptive-based control method. In order to achieve a smooth control effort, some properties are incorporated and the proposed control algorithm is constructed using the Lyapunov theorem where the closed-loop stability and robust tracking are ensured. The effectiveness of the proposed controller in rejecting high perturbed load torque with smooth control effort is verified with comparing of an adaptive sliding mode control (ASMC) and validated with experimental results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.109-116
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• 2000

This paper presents the results of investigation on the effects of surface loading on the performance of soil-reinforced segmental retaining walls using the finite element method of analysis. A parametric study was performed by varying location of surface loading. The results of the analyses indicate that the increment of the reinforcement tensile load due to the presence of surface load may be significantly over-estimated when using the conventional approach. Furthermore, the external stability should be carefully examined when a surface loading is present just outside the reinforced soil zone. The implications of the findings from this study to current design approaches are discussed in detail.

• 한국기계가공학회지
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• 제2권3호
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• pp.41-47
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• 2003

In this study an elevator plant model is made with an electro-hydraulic servo valve and a single rod cylinder. A PID controller, a velocity feedback PID controller and a MRAC controller ate designed. Experimental apparatus including an elevator plant model and these controllers are constructed. In case of experiment, external load which is made with a hydraulic cylinder and a pressure control valve burdens varying load to the elevator plant model being driven. With experiment, the control performances of three proposed control methods are compared.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.197-200
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• 2006

The portion of thin plate is expected to increases as to the development of design and fabrication technology. The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates, and in addition internal and external constraints much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to fillet weld of thin plates to reduce the weld-induced deformation. For this, fillet welding test have been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present study, it has been found that the tenssoning method is effective on reduction of weld-induced deformation.