Online First

Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Event-Based State Estimation of Complex-Value Neural Networks With Mixed Delays
LIU Feiyang, LI Bing
, Available online  , doi: 10.21656/1000-0887.420359
Abstract(44) HTML (34) PDF(11)
The event-based state estimation problem is investigated for a class of complex valued neural networks with mixed delays. By utilizing the measurement output, a novel event-triggering scheme is introduced to reduce the frequency of updating while ensuring estimation performance. A waiting time is first employed to avoid the Zeno phenomenon. By using the Lyapunov direct method and some properties of complex-valued matrix, a sufficient criterion is established to guarantee the globally asymptotic stability for the error system. The weighted parameters and gain matrices are designed by resorting to the feasible solution of matrices inequalities. Finally, a numerical example and its simulations are presented to illustrate the effectiveness of proposed approach.
Dynamic Modeling of Spatial Cooperation of Dual Mobile Manipulators
DONG Fangfang, YU Bin, ZHAO Xiaomin, CHEN Shan
, Available online  , doi: 10.21656/1000-0887.420223
Abstract(46) HTML (31) PDF(3)
The complex non-linear coupling generated in spatial cooperation process of mobile manipulators, makes it extremely tedious to model directly for spatial cooperative systems with Lagrange equation or Newton-Euler method. A dynamic modeling method, combining Udwadia-Kalaba (U-K) method with Lagrange equation, for spatial cooperation of dual mobile manipulators is explored. The load was simplified as a connecting link while modeling. The center of load was selected to be disconnected for decomposition, so that the lack of constraint information between the end joint angle and the end link angle caused by disconnecting the end joint of the manipulator is avoided; the segmented two subsystems were modeled with Lagrange equation, thus, the dynamic model of subsystems was obtained. The inherent geometric relationships of cooperative system were introduced in the form of constraints, and the U-K method was applied to obtain the dynamic model of cooperative system. The computation for modeling is reduced. Finally, the accuracy of the model was verified by numerical simulation.
Dynamic Analyses of the Assembling Process of Ultra-Large Structures by a Space Robot
WANG Qisheng, JIANG Jianping, LI Qingjun, JIANG Guoqi, DENG Zichen
, Available online  , doi: 10.21656/1000-0887.420244
Abstract(37) HTML (28) PDF(4)
Structural vibrations of the ultra-large structures during on-orbit assembly should be prevented to the maximum extent, because of the extreme flexibility and low natural frequencies. The assembling process is divided into four stages: grasping stage, position-attitude adjusting and stabilizing stage, mounting stage, and crawling stage. This paper focuses on the mounting stage, and a collinear assembly trajectory planning method is proposed to prevent structural vibrations. First, a dynamic model of the on-orbit assembly system (including the main structure, the space robot, and the assembling structure) is established based on natural coordinate formulation and absolute node coordinate formulation. Second, the requirements of collinear assembly are transformed into a trajectory planning problem of the space robot. The distance from the center of mass of the space robot to the main structure should remain unaltered, which is main idea of the proposed collinear assembly method. Numerical simulation results show that the proposed assembly method can effectively prevent the transverse motions of the ultra-large structure and reduce the required grasping moment. Finally, the influences of the system parameters on the dynamic response of the assembly process are studied, which provides a theoretical basis for the on-orbit assembly of ultra-large spacecraft.
Effects of Cone Angle on Nonlinear Vibration Response of Functionally Graded Shells
ZHANG Yuhang, LIU Wenguang, LIU Chao, LÜ Zhipeng
, Available online  , doi: 10.21656/1000-0887.420273
Abstract(33) HTML (22) PDF(5)
The nonlinear vibration responses of functionally graded shells with different cone angles under external load are studied in this paper. Firstly, the Voigt model was employed to describe the physical properties along the thickness direction of FGMs conical shells. Then, the motion equations were derived based on the first shear deformation theory, von Kármán geometric nonlinearity and Hamilton’s principle. Next, the Galerkin method was applied to discretize the motion equations and the governing equations was simplified into a single degree of freedom nonlinear vibration differential equation based on the Volmir’s assumption. Finally, the nonlinear motion equation was solved by the harmonic balance method and Runge-Kutta method, and the amplitude frequency response characteristic curves of FGMs conical shell were obtained. The effects of different material distribution function and the ceramic volume fraction exponents on the amplitude frequency response curve of conical shell were discussed. The bifurcation diagrams of conical shells with different cone angles and time process diagrams and phase diagrams with different excitation amplitudes were described. The motion characteristic was characterized by Poincaré map. The results show that FGMs conical shell presents the nonlinear characteristics of "hardening" spring. The chaotic motion of FGMs conical shell is restrained and FGMs conical shell is not prone to produce motion instability with the increase of cone angle. The motion of FGMs conical shell presents a process from periodic motion to multi-periodic motion and then to chaos with the increase of excitation amplitude.
Magneto-Thermoelastic Coupling Dynamic Response of Narrow Long Thin Plate Considering Memory Effect and Size Effect
MA Yongbin, LI Dongsheng
, Available online  , doi: 10.21656/1000-0887.420200
Abstract(48) HTML (30) PDF(5)
The dual-phase-lag thermoelasticity theory with memory-dependent derivative can perfectly describe the phenomenon of non-Fourier heat conduction, nevertheless, it has not been comprehensively considered: the mechanical response of materials aroused by the size-dependent effects and the influence of multiple coupling effects such as magnetic, thermal and elastic fields. A dual-phase-lag thermoelasticity theory considering memory dependent effect and non-local effect is established. Based upon the revised theory, the magneto-thermoelastic coupling problem of a thin plate subjected to a cyclical heat source is investigated. First the governing equations of the problem are formulated. Then combining the boundary conditions and initial conditions, the solution of the problem is obtained by using Laplace transform and inverse transform techniques. Last, the effects of magnetic field, phase lag, time-delay, kernel function, non-local effect and time on the dimensionless quantities were investigated respectively, which provided a powerful reference for the dynamic response of micro-scale materials.
Interface Model and Interphase Model for Predicting the Effective Elastic Properties of Nano-Fiber Composites
CUI Chunli, XU Yaoling
, Available online  , doi: 10.21656/1000-0887.420231
Abstract(39) HTML (22) PDF(2)
The effective bulk modulus and the effective in-plane shear modulus of nano-fiber composites are investigated using interface model and interphase model based on the generalized self-consistent method, the closed-form analytical solutions of effective bulk modulus and all equations for predicting effective in-plane shear modulus by numerical method based on the two models are presented. Using the interface model, interface effects of the effective bulk modulus and the effective in-plane shear modulus are discussed by use of numerical examples. Further research demonstrates that the analytical formula of the effective bulk modulus and the numerical results of the effective in-plane shear modulus derived from the interface model can be obtained again from the interphase model. An example of aluminium containing nano voids shows that the effective bulk modulus and the effective in-plane shear modulus predicted by the interface model have large deviations from that of the interphase model when the void radius is small, however for larger void radius, the difference is small.
A Double Projection Algorithm for Solving Non-Monotone Variational Inequalities
WANG Xiaoting, LONG Xianjun, PENG Zaiyun
, Available online  , doi: 10.21656/1000-0887.420414
Abstract(35) HTML (25) PDF(10)
The projection algorithm is one of the main methods to solve variational inequality problems. At present, the research on projection algorithms usually requires the assumption that the mapping is monotone and Lipschitz continuous, but in practical problems, these assumptions are often unsatisfied. In this paper, a new double projection algorithm for solving non-monotone variational inequality problems is proposed by using the line search method. Under the assumption that the mapping is uniformly continuous, it is proved that the sequence generated by the algorithm strongly converges to a solution of variational inequalities. The numerical experiments illustrate effectiveness and superiority of the proposed algorithm.
Structural Instantaneous Frequency Identification Based on Fractional Fourier Transform
LU Lian, REN Weixin, WANG Shidong
, Available online  , doi: 10.21656/1000-0887.420241
Abstract(40) HTML (37) PDF(5)
In order to identify the instantaneous frequency of time-varying signals, this paper derives the theoretical relationship between the frequency in a signal and rotational angle α in a fractional Fourier transform. It is demonstrated that the fractional Fourier transform is actually an algorithm of ordinary Fourier transform combined with telescopic translation window. A general expression of signal instantaneous frequency in the fractional Fourier domain is thereafter formulated so that structural instantaneous frequency can be extracted accordingly. The feasibility and reliability of proposed method is verified by a simulated nonlinear frequency modulation signal and a numerical example of a three-degree-of-freedom damped time-varying structure system. The results show that the proposed method is in good agreement with the theoretical values and the method has a certain degree of anti-noise capability. Subsequently, the proposed method is capable of identifying the instantaneous frequency of time-varying structures.
State Feedback Generalized H2 Control for Continuous Integrated Control System
SUN Fengqi
, Available online  , doi: 10.21656/1000-0887.420169
Abstract(40) HTML (21) PDF(8)
Based on Lyapunov stability theory, matrix analysis method, linear matrix inequality methods, etc, the generalized H2 control of singularly perturbed uncertain control systems with time-varying delay and control input and disturbance input is studied. A memory state H2 generalized controller is designed, the decision theorem of the specific design method given. Quoting new lemma for delay dependent and delay independent cases, the relatively less conservative stability criterion is derived. The obtained results are linearized, the selected numerical examples are used to verify the effectiveness and feasibility to the derived conclusions. It is pointed out that the closed-loop system is asymptotically stable in the whole range from zero to singular perturbation upper bound, which expands the generalized H2 stability space and reduces the L2-L performance index. By comparing the stability state parameter index with the related literatures, it is shown that the proposed method has certain advantages and less conservatism, and is suitable for standard and non-standard cases.
Explicit Solutions for Wave Equation of Nonlinear Elastic Rod
GUO Peng, TANG Rongan, SUN Xiaowei, HONG Xueren, SHI Yuren
, Available online  , doi: 10.21656/1000-0887.420245
Abstract(46) HTML (40) PDF(6)
The sine-cosine method is applied to the wave equation of nonlinear elastic rod, and some new periodic and soliton solutions of the equation is obtained (material constant n is a constant different from 1). The graphs of some solutions are given through math software. The results are helpful to further research on existence of solitary waves in the nonlinear elastic rod.