• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.23-28
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• 1998

We propose a nonlinear feedback controller that can control the induction motors with high dynamic performance by means of decoupling of motor speed and rotor flux. The nonlinear feedback controller needs the information on some motor parameters. Among them, rotor resistance varies greatly with machine temperature. A new recursive adaptation algorithm for rotor resistance which can be applied to our nonlinear feedback controller is also presented in this paper. The recursive adaptation algorithm makes the estimated value of rotor resistance track its real value. Some simulation results show that the adaptation algorithm for rotor resistance is robust against the variation of stator resistance and mutual inductance. In addition, it is computationally simple and has small estimation errors. To demonstrate the practical significance of our results, we present some experimental results.

• 한국생산제조학회지
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• 제25권6호
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• pp.452-457
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• 2016

Single screw compressors are widely used in the fields of air/gas compression, refrigeration, and chemical fluid transportation systems. A single-screw compressor is composed of a screw rotor and two gate rotors located at both sides. This simple construction enables low rotational speed of the rotor, efficient compression with low noise, low vibration, and long bearing life. Despite these merits, the design method of single-screw compressors is not well known. To accelerate the industrial application of single-screw compressors, a design method using coordinate transformation is presented in this paper, and a tool trajectory is established for machining. Finally, the screw rotor, which is machined using the proposed method, is presented.

• 한국항행학회논문지
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• 제20권6호
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• pp.574-579
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• 2016

쿼드로터는 일반 무인항공기와 달리 구조가 단순하고 그 활용 가치가 매우 높아 많은 사람들의 관심을 받고 있다. 하지만 드론에 대한 관심이 높아짐에 따라 항공 안전사고 또는 분실에 대비한 비행체의 안정성과 위치파악의 중요성이 대두되고 있다. 따라서 본 논문에서는 쿼드로터의 모델링을 수식적으로 유도하여 이를 선형화시켜 간단한 제어기로 모델을 안정화시키고 다양한 센서로부터 얻은 데이터를 필터를 거쳐 기울어진 정도를 파악하여 보다 안정한 호버링이 가능한 추적 시스템을 제안하였다. 개발된 추적시스템은 비행 중인 쿼드로터의 위치를 컴퓨터로 전송해 이를 경로로 나타내어 비행경로를 파악할 수 있고 비행속도, 고도 등의 다양한 정보를 동시에 확인할 수 있게 하였다. 그리고 실제 쿼드로터에 사용되는 센서는 외란과 진동에 의해 정확한 센서 값을 측정할 수 없기 때문에 칼만필터와 상보필터를 통한 센서 결합으로 이를 극복하여 쿼드로터 호버링의 안정성을 PID 제어를 통해 구현하였다. 이를 모의 실험을 통하여 쿼드로터의 속도, 위치, 고도 등의 다양한 정보를 실시간으로 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.979-984
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• 2005

In this study, we suggest a tilt rotor aircraft and attempt to apply a nonlinear model matching control method for its maneuver. The proposed method is very simple and useful to construct the control law for the complicated nonlinear system such as aircraft motion.

• Journal of Mechanical Science and Technology
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• 제20권2호
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• pp.205-211
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• 2006

Among other critical conditions in rotor systems the large non-linear vibration excited by bearing non-linearity causes the rotor failure. For reducing this catastrophic failure and predictive detection of this phenomenon the analysis of orthotropic bearing non-linearity in rotor system using higher order frequency response functions (HFRFs) is conducted and is shown to be theoretically feasible as that of non-rotating structures. The complex HFRFs based on the Volterra series are newly developed for the process and investigated their features by using the simple forms of the FRFs associated with the forward and the backward modes.

• 전력전자학회논문지
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• 제16권6호
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• pp.602-609
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• 2011

본 논문은 역기전력 기반 센서리스 제어 시 안정적인 기동성능 확보를 위한 간단한 초기 회전자 위치추정 방법을 제안하였다. 제안된 방법은 전동기의 고정자 권선 인덕턴스의 차이에 의한 전류응답특성을 이용하여 초기 회전자 위치를 추정한다. 이러한 초기 회전자 위치추정 방법은 알고리즘 구현이 간단하고 추가적인 외부회로가 불필요하며, 전동기 상수의 영향을 받지 않는다. 제안된 방법의 타당성은 실험결과를 통하여 검증하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.13-13
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• 1998

A simple model of the tip leakage flow models of the rotor downstream flow is developed, based on Lakshminarayana's theoretical concept on the tip clearance flow and the experimental data published in open literature. And new spanwise distribution models of deviation angle and pressure loss coefficient due to the tip leakage flow are formulated for use in association with the streamline curvature method as a through flow analysis. Combining these new models and previous deviation and loss models due to secondary flow, a robust streamline curvature method is established for flow analysis of single-stage, subsonic axial turbines with wide ranges of turning angle, aspect ratio and blading type. At the exit from rotor rows, the flow variables are mixed radially according to a spanwise transport equation. The proposed streamline curvature method is tested against a forced vortex type turbine as well as a free vortex type one. The results show that the spanwise variations of flow angle, axial velocity and loss coefficients at rotor exit are predicted with good accuracy, being comparable to a steady three-dimensional Navier-Stokes analysis. This simple and fast flow analysis is found to be very useful for the turbine design at the initial design phase.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1583-1593
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• 2002

This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller. The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.125-133
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.43-46
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• 2008

Quad-Rotor, which consists of four blades, performs a flight task by controling each rotation speed of the four blades. Quad-Rotor blade making no use of cyclic pitch or collective one is a type of fixed-wing as different from helicopter blade. Although, Quad-Rotor is simple and easy to control for those reasons, blade configuration of the fixed wing is one of the critical factors in determining the performance of Quad-Rotor. In the present study, coefficients for thrust and power of Quad-Rotor blade were derived from the data acquired by using 6-component balances. Firstly, Measurements for aerodynamic force were conducted at various pitch angles (i.e., from 0$^{\circ}$ to 90$^{\circ}$ with the interval of 10$^{\circ}$). The blade used in this experiment has aspect ratio of 6 and chord length of 35.5 mm. Secondly, assembled-blade, which was an integral blade but divided into many pieces, was used in order to test aerodynamic forces along twist angles. The curve of thrust coefficient along pitch angle indicates a parabola form. Stall which occurs during wind tunnel test to calculate lift coefficient of airfoil does not generate. When deciding the blade twist angle, structural stability of blade should be considered together with coefficients of thrust and power. Those aerodynamic force data based on experimental study will be provided as a firm basis for the design of brand-new Quad-Rotor blade.