共查询到20条相似文献,搜索用时 31 毫秒
1.
The problem of linear time-varying(LTV) system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ‘‘frozen-time' assumption are not able to determine the dynamic stability of LTV systems.Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system's stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam experimental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides a new way to determine the dynamic stability of LTV systems by using the estimated time-varying modes. 相似文献
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This paper presents the design of a quantitative feedback control system for a three-axis hydraulic road simulator. The road
simulator is a multiple input-output (MIMO) system with parameter uncertainties which should be compensated with a robust
control method. The objective of the present paper is to reproduce the random input signal or real road vibration signal by
three hydraulic cylinders. The replaced m
2 MISO equivalent control system is suggested, which satisfies the design specification of the original m×m MIMO control system by decoupling each of the three axes. Quantitative Feedback Theory (QFT) is used to control the simulator.
The QFT illustrates a tracking performance of the closed-loop controller with low order transfer function G (s) and pre-filter F (s) having the minimum bandwidth for the uncertain plant with parameter uncertainty. The efficacy of the designed controller
is verified through dynamic simulation, which is co-simulated with hydraulic models of Matlab and Adams multi-body. The simulation
and the experimental results show that the proposed control technique works well for uncertain hydraulic plant systems. 相似文献
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《Mechanical Systems and Signal Processing》2014,42(1-2):152-166
Many systems such as turbo-generators, wind turbines and helicopters show intrinsic time-periodic behaviors. Usually, these structures are considered to be faithfully modeled as linear time-invariant (LTI). In some cases where the rotor is anisotropic, this modeling does not hold and the equations of motion lead necessarily to a linear periodically time-varying (referred to as LPTV in the control and digital signal field or LTP in the mechanical and nonlinear dynamics world) model. Classical modal analysis methodologies based on the classical time-invariant eigenstructure (frequencies and damping ratios) of the system no more apply. This is the case in particular for subspace methods. For such time-periodic systems, the modal analysis can be described by characteristic exponents called Floquet multipliers. The aim of this paper is to suggest a new subspace-based algorithm that is able to extract these multipliers and the corresponding frequencies and damping ratios. The algorithm is then tested on a numerical model of a hinged-bladed helicopter on the ground. 相似文献
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In this note, we consider lightly damped uncertain linear systems with natural frequency variations. This type of uncertainty
has multiple uncertain parameters with multiple rank structure. It is well known that the conventional LQG or LQG/LTR methods
can not be applied to such system bccause of the instability and the design conservatism. To overcome such shortcomings, we
propose a systematic method to design robust LQG controllers. The proposed method requires only the LQG tuning parameters
and the structure information of uncertainty. It will be shown that our approach can be effectively applied to flexible structure
control design problems.
Center for Noise and Vibration Control (NoViC), Dept. of Mech Eng., Korea Advanced Institute of Science and Technology (KAIST) 相似文献
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Myung-Chul Han 《Journal of Mechanical Science and Technology》1995,9(2):177-186
The design of decentralized controllers for a class of uncertain interconnected nonlinear systems is considered. The uncertainty
considered here is time-varying and appears at each subsystem and interconnections. Two control techniques are explored. The
first one, namely, the feedback linearization control, involves a known and autonomous nonlinear system. The second one, namely,
the robust control, is especially suitable if any uncertainty and/or time-varying factors are involved in the nonlinear dynamics.
These two controllers are combined to stabilize a class of large-scale nonlinear uncertain systems. Two decentralized robust
controllers, nonadaptive and adaptive, are proposed and those results are proved. 相似文献
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定量反馈理论(QFT)是一种新颖的频率域鲁棒控制技术,在N ichols图上开展分析与设计。针对大包线范围内系统模型变化大的特点,可采用QFT设计横航向控制器。由于QFT主要针对单输入单输出(SISO)系统进行分析,因此首先应采用特征结构配置(EA)理论将无人机的横航向模态进行近似解耦,将多输入多输出(M IMO)系统转化为SISO系统,再采用QFT进行控制系统设计。本文将两种控制方法结合起来,构成综合优化飞行控制方法,针对某型无人机包线范围内选取的18个状态点组成的控制对象模板进行控制设计,并进行非线性仿真。仿真结果表明设计的控制器使得无人机在全包线范围内具有较好的性能和鲁棒稳定性。 相似文献
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The paper considers the tracking problem for a class of uncertain linear time invariant (LTI) systems with both uncertain parameters and external disturbances. The active disturbance rejection tracking controller is designed and the resulting closed-loop system׳s characteristics are comprehensively studied. In the time-domain, it is proven that the output of closed-loop system can approach its ideal trajectory in the transient process against different kinds of uncertainties by tuning the bandwidth of extended state observer (ESO). In the frequency-domain, different kinds of parameters׳ influences on the phase margin and the crossover frequency of the resulting control system are illuminated. Finally, the effectiveness and robustness of the controller are verified through the actuator position control system with uncertain parameters and load disturbances in the simulations. 相似文献
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Shinn-Horng Chen Jyh-Horng Chou Chien-Jyh Chen 《International Journal of Mechanical Sciences》2008,50(3):455-465
In this paper, a robust-optimal control approach is proposed to treat the active vibration control (or active vibration suppression) problem of flexible mechanical systems under mode truncation, linear time-varying parameter uncertainties in both the controlled and residual parts, feedback gain perturbations, estimator gain perturbations and partial actuator failures. A sufficient condition is proposed to ensure that the flexible mechanical systems with time-varying structured parameter uncertainties are asymptotically stable against partial actuator failures. Systems which have such a property of keeping stable under partial actuator failures are said to possess integrity, and this is an inherent property of MIMO systems. Based on the robust stability constraint and the minimization of a defined H2 performance, a hybrid Taguchi-genetic algorithm (HTGA) is applied to solve the optimal state feedback controller and observer design problem of uncertain flexible mechanical systems. A design example of a flexible rotor system is given to demonstrate the applicability of the proposed approach. It is shown that the proposed approach can obtain satisfactory results. 相似文献
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This paper presents an efficient method for identification of nonlinear Multi-Input Multi-Output (MIMO) systems in the presence of colored noises. The method studies the multivariable nonlinear Hammerstein and Wiener models, in which, the nonlinear memory-less block is approximated based on arbitrary vector-based basis functions. The linear time-invariant (LTI) block is modeled by an autoregressive moving average with exogenous (ARMAX) model which can effectively describe the moving average noises as well as the autoregressive and the exogenous dynamics. According to the multivariable nature of the system, a pseudo-linear-in-the-parameter model is obtained which includes two different kinds of unknown parameters, a vector and a matrix. Therefore, the standard least squares algorithm cannot be applied directly. To overcome this problem, a Hierarchical Least Squares Iterative (HLSI) algorithm is used to simultaneously estimate the vector and the matrix of unknown parameters as well as the noises. The efficiency of the proposed identification approaches are investigated through three nonlinear MIMO case studies. 相似文献
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Sliding mode control methods have been used widely since they provide robustness against parameter variations and disturbances. This paper focuses on the problem of a robust output-sliding control design for linear uncertain multi-input multi-output time-varying systems with norm-bounded uncertainty. Output signals are used for the definition of switching hypersurfaces. The formulation of a control law is emphasized. Output tracking can be achieved against a class of time varying parameter variations and external disturbances. The effectiveness of the proposed output-sliding control is confirmed by an application example. 相似文献
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Uncertainty modeling and predicting the probability of stability and performance in the manufacture of dynamic systems 总被引:2,自引:0,他引:2
Roger Fales 《ISA transactions》2010,49(4):528-534
In this work, a method for determining the reliability of dynamic systems is discussed. Using statistical information on system parameters, the goal is to determine the probability of a dynamic system achieving or not achieving frequency domain performance specifications such as low frequency tracking error, and bandwidth. An example system is considered with closed loop control. A performance specification is given and converted into a performance weight transfer function. The example system is found to have a 20% chance of not achieving the given performance specification. An example of a realistic higher order system model of an electro hydraulic valve with spring feedback and position measurement feedback is also considered. The spring rate and viscous friction are considered as random variables with normal distributions. It was found that nearly 6% of valve systems would not achieve the given frequency domain performance requirement. Uncertainty modeling is also considered. An uncertainty model for the hydraulic valve systems is presented with the same uncertain parameters as in the previous example. However, the uncertainty model was designed such that only 95% of plants would be covered by the uncertainty model. This uncertainty model was applied to the valve control system example in a robust performance test. 相似文献
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In this paper, we consider fuzzy identification of uncertain nonlinear systems in Takagi-Sugeno (T-S) form for the purpose of robust fuzzy control design. The uncertain nonlinear system is represented using a fuzzy function having constant matrices and time varying uncertain matrices that describe the nominal model and the uncertainty in the nonlinear system respectively. The suggested method is based on linear programming approach and it comprises the identification of the nominal model and the bounds of the uncertain matrices and then expressing the uncertain matrices into uncertain norm bounded matrices accompanied by constant matrices. It has been observed that our method yields less conservative results than the other existing method proposed by S?krjanc et al. (2005) [11] and [12]. With the obtained fuzzy model, we showed the robust stability condition which provides a basis for different robust fuzzy control design. Finally, different simulation examples are presented for identification and control of uncertain nonlinear systems to illustrate the utility of our proposed identification method for robust fuzzy control. 相似文献
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In this paper, we consider the problem of delay-interval-dependent robust stability and stabilization of a class of linear uncertain neutral-type systems with time-varying delay. By constructing a candidate Lyapunov–Krasovskii functional (LKF), that takes into account the delay-range information appropriately, less conservative robust stability criteria are proposed in terms of linear matrix inequalities (LMIs) to compute the maximum allowable upper bounds (MAUB) for the delay-interval within which the uncertain neutral-type system under consideration remains asymptotically stable. The verifiable stabilizability conditions and memoryless state feedback control design are stated. Finally, numerical examples are also designated to demonstrate the effectiveness and reduced conservatism of the developed results. 相似文献
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This paper aims to investigate the problem of resilient guaranteed cost control for uncertain Takagi–Sugeno fuzzy systems with Markov jump parameters and time-varying delay. A resilient mode-dependent fuzzy controller is designed and a weak sufficient condition is developed to ensure that the resulting closed-loop system is robust almost surely asymptotically stable with guaranteed cost index not exceeding the specified upper bound. Subsequently, the controller gain and upper bound of the guaranteed cost index can be obtained by solving a set of linear matrix inequalities. Finally, numerical and practical examples of the single-link robot arm system are provided to demonstrate the performance of the proposed approach. 相似文献
19.
Robust extended Kalman filter of discrete-time Markovian jump nonlinear system under uncertain noise
Jin Zhu Junhong Park Kwan-Soo Lee Maksym Spiryagin 《Journal of Mechanical Science and Technology》2008,22(6):1132-1139
This paper examines the problem of robust extended Kalman filter design for discrete-time Markovian jump nonlinear systems
with noise uncertainty. Because of the existence of stochastic Markovian switching, the state and measurement equations of
underlying system are subject to uncertain noise whose covariance matrices are time-varying or un-measurable instead of stationary.
First, based on the expression of filtering performance deviation, admissible uncertainty of noise covariance matrix is given.
Secondly, two forms of noise uncertainty are taken into account: Non-Structural and Structural. It is proved by applying game
theory that this filter design is a robust mini-max filter. A numerical example shows the validity of the method. 相似文献
20.
Xifan Yao Yi Zhang Bin Li Zheng Zhang Xiaoqin Shen 《The International Journal of Advanced Manufacturing Technology》2013,69(5-8):1701-1715
Force control is an effective means of improving the quality and efficiency of machining operations, so various approaches for force control have been proposed. However, due to the nonlinear, time-varying and uncertain characteristics of machining processes, it is difficult to develop force control systems that are stable and robust over the full range of operating conditions. This study proposed two control schemes to address such difficulties in the field of nonlinear force control by using a linear feedback proportional-derivate (PD) controller respectively with two different nonlinear intelligent compensators: fuzzy logic compensator (FLC) and neural network compensator (NNC). The PD controller is used to improve the transient response while maintaining the stability of the process system, and the FLC or NNC is employed to eliminate the steady-state error and compensate for the system nonlinearity (or uncertainty). The applications of the proposed schemes in machining processes show that the controllers adapt well to nonlinearity under time-varying cutting conditions in comparison to PID, PD, and FLC. The online updating of the NNC parameters through the Feedback-Error Learning can further improve the system performance. 相似文献