• Title/Summary/Keyword: Nonlinearity Parameter

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Force Control of Electro-Hydraulic Servo System using Direct Drive Valve for Pressure Control (압력제어용 직동 밸브를 이용한 전기.유압 서보시스템의 힘 제어)

  • Lee C.D.;Lee J.K.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.1 no.3
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    • pp.14-19
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    • 2004
  • The Direct Drive Valve used in this study contains a pressure-feedback-loop in itself, then it can eliminate nonlinearity such as the square-root-term in flow rate calculation and the change of bulk modulus of hydraulic oil. In this study, assuming that the dynamic characteristic of the DDV is modelled as a first order lag system, an parameter identification method using the input data and the output data is applied to obtain DDV's mathematical model. Then, a state feedback controller was designed to implement the force control of hydraulic system, and the control performance was evaluated.

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Comparative Study of Linear and Nonlinear Ultrasonic Techniques for Evaluation Thermal Damage of Tube-Like Structures

  • Li, Weibin;Cho, Younho;Li, Xianqiang
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.1
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    • pp.1-6
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    • 2013
  • Ultrasonic guided wave techniques have been widely used for long range nondestructive detection in tube-like structures. The present paper investigates the ultrasonic linear and nonlinear parameters for evaluating the thermal damage in aluminum pipe. Specimens were subjected to thermal loading. Flexible polyvinylidene fluoride (PVDF) comb transducers were used to generate and receive the ultrasonic waves. The second harmonic wave generation technique was used to check the material nonlinearity change after different heat loadings. The conventional linear ultrasonic approach based on attenuation was also used to evaluate the thermal damages in specimens. The results show that the proposed experimental setup is viable to assess the thermal damage in an aluminum pipe. The ultrasonic nonlinear parameter is a promising candidate for the prediction of micro-damages in a tube-like structure.

Analysis of Nonlinear Control Characteristic for the Parameter Variation of AC Motors (교류전동기의 파라미터 변동에 대한 비선형 제어특성의 해석)

  • Shon, Jin-Geun;Park, Jong-Chan;Lee, Bok-Yong;Jeon, Hee-Jong
    • Proceedings of the KIEE Conference
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    • 2001.07e
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    • pp.108-112
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    • 2001
  • Vector control schemes are used in inverter-fed induction motor drives to obtain high performance. Crucial to the success of the vector control scheme is the knowledge of the instantaneous position of the rotor flux. However, the position of the rotor flux change with temperature and magnetic saturation of the motor. This variation cause deterioration of both steady state and dynamic operation of the motor drives. Performance degradation is in the form of input-output torque nonlinearity and saturation of the motor. Analytic expressions are derived to evaluate the effects due to parameter sensitivity.

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Nonlinear Parameter Estimation of Suspension System (현가장치의 비선형 설계변수 추정)

  • 박주표;최연선
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.281-286
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    • 2003
  • A Suspension system of a car is composed of dampers and springs. The dampers and springs usually have nonlinear characteristics. However, the nonlinear characteristics of the springs and dampers through analytical model cannot agree with the experimental results. Therefore, the nonlinearity of the suing and damper should be known from the experimental results. In this study, the methods of system identification for nonlinear dynamic system in time domain are discussed and the nonlinear parameter estimation lot experimental data of an EF-SONATA car was done. The results show that a cubic and a coupled term should be considered to model the suspension system.

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A Study on Coagulant Feeding Control of the Water Treatment Plant Using Intelligent Algorithms (지능알고리즘에 의한 정수장 약품주입제어에 관한 연구)

  • 김용열;강이석
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.1
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    • pp.57-62
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    • 2003
  • It is difficult to determine the feeding rate of coagulant in the water treatment plant, due to nonlinearity, multivariables and slow response characteristics etc. To deal with this difficulty, the genetic-fuzzy system genetic-equation system and the neural network system were used in determining the feeding rate of the coagulant. Fuzzy system and neural network system are excellently robust in multivariables and nonlinear problems. but fuzzy system is difficult to construct the fuzzy parameter such as the rule table and the membership function. Therefore we made the genetic-fuzzy system by the fusion of genetic algorithms and fuzzy system, and also made the feeding rate equation by genetic algorithms. To train fuzzy system, equation parameter and neural network system, the actual operation data of the water treatment plant was used. We determined optimized feeding rates of coagulant by the fuzzy system, the equation and the neural network and also compared them with the feeding rates of the actual operation data.

A Development of New Vehicle Model for Yaw Rate Estimation (요각속도 추정을 위한 새로운 차량 모델의 개발)

  • Bae, Sang-Woo;Shin, Moo-Hyun;Kim, Dae-Kyun;Lee, Jang-Moo;Lee, Jae-Hyung;Tak, Tae-Oh
    • Proceedings of the KSME Conference
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    • 2001.06b
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    • pp.565-570
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    • 2001
  • Vehicle dynamics control (VDC) system requires more information on driving conditions compared with ABS and/or TCS. In order to develop the VDC system, tire slip angles, vehicle side-slip angle, and vehicle lateral velocity as well as road friction coefficient are needed. Since there are not any cheap and reliable sensors, recent researches on parameter estimation have given rise to a number of parameter estimation techniques. This paper presents new vehicle model to estimate vehicle's yaw rate. This model is improved from the conventional 2 degrees of freedom vehicle model, so-called bicycle model, taking nonlinear effects into account. These nonlinear effects are: (i) tyre nonlinearity; (ii) lateral load transfer during cornering; (iii) variable gear ratio with respect to vehicle velocity. Estimation results are validated with the experimental results.

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Euler Parameters Method for Large Deformation Analysis of Marine Slender Structures (오일러 매개변수를 이용한 해양 세장체 대변위 거동 해석)

  • Hong, Sup
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2003.05a
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    • pp.163-167
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    • 2003
  • A novel method for 3-dimensional dynamic analysis of marine slender structure gas been developed by using Euler parameters. The Euler parameter rotation, which is being widely used in aerospace vehicle dynamics and multi-body dynamics, has been applied to elastic structure analysis. Large deformation of flexible slender structures is described by means of Euler parameters. Euler parameter method is implemented effectively in incremental-iterative algorithm for 3D dynamic analysis. The normalization constraint of Euler parameters is efficiently satisfied by means of a sequential updating method.

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Equivalent Circuit Analysis of Single Phase Induction Motor Considering Magnetic Saturation Characteristics (자기포화 특성을 고려한 단상유도전동기의 등가회로 해석)

  • Kim, Young Sun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.2
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    • pp.270-277
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    • 2013
  • Single phase induction motor(SPIM) is used widely because it is driven by single phase source. However, the efficiency of the motor is not good due to saturation of magnetic material. To analyze the motor accurately, the magnetic saturation characteristics should be considered in analysis of equivalent circuit. In this paper, lumped parameter of circuit are derived from multi phase induction motor using method of symmetrical coordinates. Also, we presents a method for the equivalent circuit analysis of SPIM using magnetic saturation rate. The magnetic nonlinearity is considered deriving magnetizing reactance from voltage-current saturation curve. As a results, current characteristic, torque, output and efficiency are shown through analysis of equivalent circuit. A simulation results of SPIM will be used to improve the characteristics and efficiency of motor.

A Study on the Effects of Process Parameters on Dynamic Behavior Changes of Turning System (선반에서 공정변수가 가공물의 동적 거동 변화에 미치는 영향에 관한 연구)

  • Kim, Kiho;Oh, Chaeyoun
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.8
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    • pp.21-28
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    • 1997
  • This paper presents the influence of the process parameters on the change in dynamic behavior of a lathe turning system. With variation of feed rate, depth of cut, direction of tool motion, cutting speed and tool location along the workpiece, the dynamic characteristics of stable cutting, chatter transition and fully developed chatter regions are demonstrated. The workpiece vibration during machining is continuously measured at different tool locations along the workpiece and quantitatively analyzed. Complex linear behavior due to change of process parameter values as well as fundamental wystem nonlinearity due to change of process configuration indicated by a tool path dependence of the locations of chatter onset and disappearance are described. Finally, the structural characteristics of the turning system which can have large and nonlinear effects on system behavior are presented.

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Nonlinear resonances of nonlocal strain gradient nanoplates made of functionally graded materials considering geometric imperfection

  • Jia-Qin Xu;Gui-Lin She;Yin-Ping Li;Lei-Lei Gan
    • Steel and Composite Structures
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    • v.47 no.6
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    • pp.795-811
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    • 2023
  • When studying the resonance problem of nanoplates, the existing papers do not consider the influences of geometric nonlinearity and initial geometric imperfection, so this paper is to fill this gap. In this paper, based on the nonlocal strain gradient theory (NSGT), the nonlinear resonances of functionally graded (FG) nanoplates with initial geometric imperfection under different boundary conditions are established. In order to consider the small size effect of plates, nonlocal parameters and strain gradient parameters are introduced to expand the assumptions of the first-order shear deformation theory. Subsequently, the equations of motion are derived using the Euler-Lagrange principle and solved with the help of perturbation method. In addition, the effects of initial geometrical imperfection, functionally graded index, strain gradient parameter, nonlocal parameter and porosity on the nonlinear forced vibration behavior of nanoplates under different boundary conditions are discussed.