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1.
In this paper we propose a new method to estimate parameters of a dynamical system from observation data on the basis of a neural network collocation method. We construct an object function consisting of squared residuals of dynamical model equations at collocation points and squared deviations of the observations from their corresponding computed values. The neural network is then trained by optimizing the object function.The proposed method is demonstrated by performing several numerical experiments for the optimal estimates of parameters for two different nonlinear systems. Firstly, we consider the weakly and highly nonlinear cases of the Lorenz model and apply the method to estimate the optimum values of parameters for the two cases under various conditions. Then we apply it to estimate the parameters of one-dimensional oscillator with nonlinear damping and restoring terms representing the nonlinear ship roll motion under various conditions. Satisfactory results have been obtained for both the problems.  相似文献   

2.
The common effect of waves and the slippage of internal heavy loads will cause a ro-ro ship to roll seriously. This is one of the important reasons when ro-ro ships capsize. The multibody system with a floating base is composed of a ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacements of the heavy loads on deck as degrees of freedom. The equations of motion of the system are derived, including the influence of the nonlinear restoring and damping moments due to the influence of the waves. Taking a certain channel ferry as an example, a set of numerical calculations have been carried out for the synchronous effect of slipping heavy loads on a rolling ro-ro ship, the nonlinear rolling response of the ship and the displacement response of the slipping heavy load under the common effect of synchro-slipping heavy loads and wave. The conclusions are that the motion of the numerous freely slipping vehicles synchronize in most cases and the nonlinear rolling angle of the ro-ro ship will increase when considering the nonlinear characteristics.  相似文献   

3.
针对仅位置和艏向可测量的动力定位船舶非线性输出反馈轨迹跟踪问题,在大地坐标系中,建立同时包含科里奥力向心力和非线性阻尼的非线性船舶操纵性模型.基于一种具有半全局一致指数稳定性的非线性观测器,提出船舶轨迹跟踪非线性 Backstepping 观测控制器,并应用 Lyapunov 方法证明该观测控制器具有半全局一致指数稳定性.理论分析和仿真结果均表明,通过调整控制器增益,系统误差指数收敛到零.  相似文献   

4.
Generalization to the previous oscillators is done by introducing the nonlinear elastic and damping forces. The mathematical model of the system is a second order differential equation with nonlinear elastic and damping terms whose order is integer and/or noninteger. Cveticanin’s solving procedure is extended for solving such a strong nonlinear differential equation. The approximate solution obtained is a function of initial amplitude and initial phase. A damping coefficient and order of damping interaction with an elastic coefficient and order of elasticity for the generalized oscillators are also determined. Special attention is paid to obtain the relation between initial amplitude and phase, on the one hand, and initial displacement and velocity on the other hand. Correction to the frequency of vibration for the linear oscillators with nonlinear damping and for the pure nonlinear oscillators with linear damping is obtained and analyzed. Analytical results given in this paper are compared with numerically obtained ones and show a good agreement.  相似文献   

5.
A methodology is proposed to design a controller that forces position and orientation of underactuated ships to globally track a reference trajectory. The ships under consideration are not actuated in the sway direction, and the mass and damping matrices are not assumed to be diagonal, as often required in the literature. It is not required that the reference trajectory be generated by a ship model. The paper also addresses the tracking problem with constant bias of environmental disturbances. The new result is facilitated by the introduction of change to the ship position, several nonlinear coordinate changes, the backstepping technique, and utilizing the ship dynamic structure.  相似文献   

6.
This paper is to suggest a novel design for ship tracking control of the benchmark Norrbin nonlinear ship model under relaxed conditions. The challenges of the problem under investigation include the uncertain or absent information of the model time constant, the uncertain reference course, and the intrinsic environmental disturbances. We formulate the ship tracking control problem in terms of a nonlinear output regulation problem with unknown control direction and uncertain exosystems. To solve the problem, we first adopt a novel internal model candidate to convert the output regulation problem into a stabilization problem for an augmented system. Then, a Nussbaum‐gain‐based stabilizer is developed for the augmented system to complete the design. Simulation results are presented to show the effectiveness of the proposed controller.  相似文献   

7.
针对扰动不确定非线性船舶动力定位问题,提出了一种带观测器的不确定扰动非线性船舶动力定位自适应输出反馈控制.设计了一个非线性观测器,从附有噪声的输出中估计出船舶位置以及运动速度.用滤波后的位置信号,针对扰动不确定非线性船舶设计带观测器的自适应反步控制器,该控制在Backstepping设计方法的基础上引入积分环节,对存在未知参数和动态不确定扰动的船舶能有效的改善系统性能.根据Lyapunov稳定性理论证明所设计的控制器是全局渐近稳定的,仿真结果验证了该方法的有效性.  相似文献   

8.
An analytical method of computing the frequency response of single degree of freedom (DOF) oscillators with nonlinear damping is described. The author proposes an energy-type nonlinear damping model and the corresponding stationary probability density with white noise input can be obtained explicitly. A theorem is presented which gives an interesting result, in terms of the Krylov-Bogoliubov approximation, concerning the modeling and identification of nonlinear internal damping in flexible structures. This analysis also serves as a contribution to random vibration theory by providing a method of computing the first- and second-order statistics (steady-state probability density, correlation function, and spectral density) of nonlinearity damped oscillators with white noise input  相似文献   

9.
In this paper, a new approach to stability analysis of nonlinear dynamics of an underactuated autonomous underwater vehicle (AUV) is presented. AUV is a highly nonlinear robotic system whose dynamic model includes coupled terms due to the hydrodynamic damping factors. It is difficult to analyze the stability of a nonlinear dynamical system through Routh’s stability approach because it contains nonlinear dynamic parameters owing to hydrodynamic damping coefficients. It is also difficult to analyze the stability of AUVs using Lyapunov’s criterion and LaSalle’s invariance principle. In this paper, we proposed the extended-Routh’s stability approach to verify the stability of such nonlinear dynamic systems. This extended-Routh’s stability approach is much easier as compared to the other existing methods. Numerical simulations are presented to demonstrate the efficacy of the proposed stability verification of the nonlinear dynamic systems, e.g., an AUV system dynamics.  相似文献   

10.
一类非线性隔振器振动传递特性分析   总被引:4,自引:2,他引:4  
非线性输出频率响应函数是由Volterra级数发展而来的一个新概念.对一类具有反对称阻尼特性的隔振器,通过该概念推导出了振动传递性与系统非线性参数之间的显式解析关系;进而系统地研究了非线性阻尼参数对隔振器的力传递性能和位移传递性能的影响.研究结果表明,虽然非线性隔振器在受正弦信号激励下会出现高次倍频分量,但对于其传递性...  相似文献   

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