• 제목/요약/키워드: Limit cycle

검색결과 551건 처리시간 0.024초

비틀림 비선형성을 갖는 2차원 익형의 Critical Slowing Down 을 이용한 Limit Cycle Flutter 예측 인자 (Warning Signal for Limit Cycle Flutter of 2D Airfoil with Pitch Nonlinearity by Critical Slowing Down)

  • 임주섭;이상욱;김태욱
    • 한국항공운항학회지
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    • 제21권4호
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    • pp.47-52
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    • 2013
  • In this paper, limit cycle flutter induced by Hopf bifurcation is studied with nonlinear system analysis approach and observed for the critical slowing down phenomenon. Considering an attractor of the dynamics of a system, when a small perturbation is applied to the system, the dynamics converge toward the attractor at some rate. The critical slowing down means that this recovery rate approaches zero as a parameter of the system varies and the size of the basin of attraction shrinks to nil. Consequently, in the pre-bifurcation regime, the recovery rates decrease as the system approaches the bifurcation. This phenomenon is one of the features used to forecast bifurcation before they actually occur. Therefore, studying the critical slowing down for limit cycle flutter behavior would have potential applicability for forecasting those types of flutter. Herein, modeling and nonlinear system analysis of the 2D airfoil with torsional nonlinearity have been discussed, followed by observation of the critical slowing down phenomenon.

Limit-cycle 항법과 모서리 검출을 기반으로 하는 UGV를 위한 계획 경로 알고리즘 (Path Planning Algorithm for UGVs Based on the Edge Detecting and Limit-cycle Navigation Method)

  • 임윤원;정진수;안진웅;김동한
    • 제어로봇시스템학회논문지
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    • 제17권5호
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    • pp.471-478
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    • 2011
  • This UGV (Unmanned Ground Vehicle) is not only widely used in various practical applications but is also currently being researched in many disciplines. In particular, obstacle avoidance is considered one of the most important technologies in the navigation of an unmanned vehicle. In this paper, we introduce a simple algorithm for path planning in order to reach a destination while avoiding a polygonal-shaped static obstacle. To effectively avoid such an obstacle, a path planned near the obstacle is much shorter than a path planned far from the obstacle, on the condition that both paths guarantee that the robot will not collide with the obstacle. So, to generate a path near the obstacle, we have developed an algorithm that combines an edge detection method and a limit-cycle navigation method. The edge detection method, based on Hough Transform and IR sensors, finds an obstacle's edge, and the limit-cycle navigation method generates a path that is smooth enough to reach a detected obstacle's edge. And we proposed novel algorithm to solve local minima using the virtual wall in the local vision. Finally, we verify performances of the proposed algorithm through simulations and experiments.

State-Space Analysis on The Stability of Limit Cycle Predicted by Harmonic Balance

  • Lee, Byung-Jin;Yun, Suk-Chang;Kim, Chang-Joo;Park, Jung-Keun;Sung, Sang-Kyung
    • Journal of Electrical Engineering and Technology
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    • 제6권5호
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    • pp.697-705
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    • 2011
  • In this paper, a closed-loop system constructed with a linear plant and nonlinearity in the feedback connection is considered to argue against its planar orbital stability. Through a state space approach, a main result that presents a sufficient stability criterion of the limit cycle predicted by solving the harmonic balance equation is given. Preliminarily, the harmonic balance of the nonlinear feedback loop is assumed to have a solution that determines the characteristics of the limit cycle. Using a state-space approach, the nonlinear loop equation is reformulated into a linear perturbed model through the introduction of a residual operator. By considering a series of transformations, such as a modified eigenstructure decomposition, periodic averaging, change of variables, and coordinate transformation, the stability of the limit cycle can be simply tested via a scalar function and matrix. Finally, the stability criterion is addressed by constructing a composite Lyapunov function of the transformed system.

The effect of sweep angle on the limit cycle oscillations of aircraft wings

  • Eken, Seher;Kaya, Metin Orhan
    • Advances in aircraft and spacecraft science
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    • 제2권2호
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    • pp.199-215
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    • 2015
  • This study focuses on the limit cycle oscillations (LCOs) of cantilever swept-back wings containing a cubic nonlinearity in an incompressible flow. The governing aeroelastic equations of two degrees-of-freedom swept wings are derived through applying the strip theory and unsteady aerodynamics. In order to apply strip theory, mode shapes of the cantilever beam are used. The harmonic balance method is used to calculate the frequencies of LCOs. Linear flutter analysis is conducted for several values of sweep angles to obtain the flutter boundaries.

Anti-windup 보상기의 점프공진에 관한 연구 (Jump resonance in anti-windup compensator for systems with saturating actuators)

  • 박영진;장원욱
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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    • pp.1060-1066
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    • 1992
  • One of the undesirable nonlinear phenomenon called 'wind up' occours when the integrator in the controller and the saturated actuator interact. Large overshoot, slow response, instability, limit cycle and jump resonance are the characteristics of wind up phenomenon. Several 'anti-windup' compensators have been developed to prevent some of the aforementioned nonlinear characteristics such as instabilituy and limit cycle, but none has studied the effect of antiwindup compensator on the jump resonance. In this paper, we developed an analyitcal method to design the compensator to prevent not only limit cycle but also jump resonance. An illustrative example is included to show the compensator eliminates jump resonance of effectively.

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Cubic 비선형 저항에 의한 카오스 발진회로의 스펙트럼 (Spectrums of Chua's Oscillator Circuit with a Cubic Nonlinear Resistor)

  • 김남호
    • Journal of Advanced Marine Engineering and Technology
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    • 제22권6호
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    • pp.908-919
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    • 1998
  • This paper describes implementation and simulation of Chua's oscillator circuits with a cubic non-linear resistor. The two-terminal nonlinear resistor NR consists of one Op Amp two multipliers and five resistors. The Chua's oscillator circuit is implemented with analog electronic devices. Period-1 limit cycle period-2 limit cycle period-4 limit cycle and spiral attractor double-scroll attractor and 2-2 window are observed experimentally from the laboratory model and simulated by computer for the presented model. Comparing the result of experiments and simulations the spectrums are satisfied.

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이동로붓을 위한 Limit-cycle 항법 (Limit-cycle Navigation Method for Fast Mobile Robots)

  • 류근호;김동한
    • 제어로봇시스템학회논문지
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    • 제14권11호
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    • pp.1130-1138
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    • 2008
  • A mobile robot should be designed to navigate with collision avoidance capability in the real world, coping with the changing environment flexibly. In this paper, a novel navigation method is proposed for fast moving mobile robots using limit-cycle characteristics of the 2nd-order nonlinear function. It can be applied to robots in dynamically changing environment such as the robot soccer. By adjusting the radius of the motion circle and the direction of the obstacle avoidance, the mobile robot can avoid the collision with obstacles and move to the destination point. To demonstrate the effectiveness and applicability, it is applied to the robot soccer. Simulations and real experiments ascertain the merits of the proposed method.

Multiple input describing function analysis of non-classical aileron buzz

  • Zafar, Muhammad I.;Fusi, Francesca;Quaranta, Giuseppe
    • Advances in aircraft and spacecraft science
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    • 제4권2호
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    • pp.203-218
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    • 2017
  • This paper focuses on the computational study of nonlinear effects of unsteady aerodynamics for non-classical aileron buzz. It aims at a comprehensive investigation of the aileron buzz phenomenon under varying flow parameters using the describing function technique with multiple inputs. The limit cycle oscillatory behavior of an asymmetrical airfoil is studied initially using a CFD-based numerical model and direct time marching. Sharp increases in limit cycle amplitude for varying Mach numbers and angles of attack are investigated. An aerodynamic describing function is developed in order to estimate the variation of limit cycle amplitude and frequency with Mach number and angle of attack directly, without time marching. The describing function results are compared to the amplitudes and frequencies predicted by the CFD calculations for validation purposes. Furthermore, a limited sensitivity analysis is presented to demonstrate the potential of the approach for aeroelastic design.

TMCP 고장력강 용접부의 피로 특성에 관한 연구 (Fatigue properties of welded joints for TMCP steels)

  • 임채범;권영각;엄기원
    • Journal of Welding and Joining
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    • 제8권2호
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    • pp.40-52
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    • 1990
  • Fatigue behavior of the AH, DH and EH grade TMCP(Thermo-Mechanical Control Process) steels was studied. High cycle and low cycle fatigue tests were carried out for the weldment and base metal of each steel. The results showed that the fatigue limit at 2 * $10^6$ cycles was 33 to 37 kg/$mm^2$ for the base metal and 30 to 34 kg/$mm^2$ for the weldment. The ratio of fatigue limit to tensile strength for TMCP steels was 0.65 to 0.71, which was a value close to the upper limit for the ordinary steels. It was also found that the high cycle fatigue behavior of TMCP steels could be affected by the microstructures of base metal. It will be necessary to have fine structure for TMCP steels to increase the fatigue resistance. In low cycle fatigue test, the fatigue lifetime of AH and DH steels accorded well with the ASME best fit curve, while that of EH steel was considerably lower than the fatigue lifetime of the other steels. Fatigue resistance of the weldment made by high heat input(180kJ/cm) welding was not lower than that made by low heat input(80kJ/cm) welding in case of high cycle fatigue, but the high heat input welding decreased the fatigue resistance in case of low cycle fatigue.

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構造용高炭素鋼材 의 高溫 低 사이클 피勞擧動 에 關한 硏究 (A Study on Low-Cycle Fatigue Behavior at Elevated Temperature of High Carbon Steel Used For Structural Purpose)

  • 옹장우;김재훈
    • 대한기계학회논문집
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    • 제6권2호
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    • pp.101-106
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    • 1982
  • This study was undertaken to determine tensile properties and low-cycle fatigue behavior of 0.6%C high carbon steel used of structural purposes at temperatures up to 500.deg.C. In the low-cycle fatigue test the upper limit was decided by elongation(i.e. the total strain range), while the lower limit was defined by the load (i.e. zero load). The following results were obtained. Both, the ultimate tensile strength and low-cycle fatigue resistance attain the maximum values near 250.deg.C. Above this temperature the values decrease rapidly as the temperature increases. The low-cycle fatigue resistance decreases whenever there is an increase of the total strain range. Because the hardness of cycle fatigued specimen correlates cyclic hardening and cyclic softening, therefore the hardness of cycle fatigued specimen is smaller than that of the nonfatigued specimen at room temperature and 500.deg.C but much larger than the hardness of the nonfatigued specimen near 250.deg.C.