2014, 12(2):97-104. DOI: 10.6052/1672-6553-2014-006
Abstract:The application background of dynamic force estimation technique in engineering was presented. Recent advances in the inverse problem of dynamic force estimation techniques were systematically reviewed in terms of analytical theory and application in real engineering, and the key scientific issues in the study of dynamic force estimation problems were explored. Finally, the key topics for further study of the application of dynamic force estimation techniques were pointed out.
2014, 12(2):105-110. DOI: 10.6052/1672-6553-2013-074
Abstract:In this paper are study the symmetry of Lagrangians and the conserved quantities for a nonholonomic relativistic system. The Criterion of the symmetry for a nonholonomic relativistic system is given. Then the conditions under which there exist a conserved quantity and the form of the conserved quantity are obtained. And finally there is an example to illustrate the application of the results.
2014, 12(2):111-114. DOI: 10.6052/1672-6553-2013-092
Abstract:Symmetry classifications and reductions for generalized Burgers equation were discussed specifically by using Lie group method, where is the smooth function of . And we obtained eight categories classified symmetry and the corresponding reduced equation of . The results provide reference for the exact solutions of the generalized Burgers equation study.
2014, 12(2):115-118. DOI: 10.6052/1672-6553-2013-076
Abstract:This paper studied the KdV equation with timedependent coefficients and forcing term and the coupled KdV equations with timedependent coefficients by using soliton ansaze. Firstly, the equation was converted to homogeneous equation by using a variable transformation. Then, by assuming the soliton solutions to be the form of sech function, and with the help of Maple software, the complicated and tedious calculations were performed, and the conditions of existence of solitons and soliton solutions were obtained. The results show that the calculation of soliton ansaze is simple and can obtain bright soliton solutions.
2014, 12(2):119-126. DOI: 10.6052/1672-6553-2013-065
Abstract:In this paper, the complete synchronization and antiphase synchronization between the 3dimensional chaotic system and 4dimensional hyperchaotic system with different dimension and fractional order are researched in which the fractionalorder Lü chaotic system and the fractionalorder Chen hyperchaotic system are as an example. First, Based on the fractional theory of stability and nonlinear dynamic theory. the nonlinear controller is designed, and by the nonlinear controller the complete synchronization and antiphase synchronization between different the 3D fractionalorder chaotic system and 4D fractionalorder hyperchaotic system with different dimension and fractional order are realized. Second, based on the fractionalorder theory of stability the two kind of synchronization are respectively proved strictly in mathematics. Finally, by the PredictorCorrector scheme numerical simulation, the validity of the method presented in this paper is verified.
2014, 12(2):127-131. DOI: 10.6052/1672-6553-2013-108
Abstract:Based on the invariance principle of differential equation, a simple adaptive control method was proposed to synchronize the dynamical networks with the general coupling functions. Compared with other previous adaptive control methods, only one node’s states were used as target orbit to design the controller. This improvement can reduce the dimension of the system and amount of information transmitted among the nodes. To show the effectiveness of the proposed method, some numerical simulations were performed.
2014, 12(2):132-138. DOI: 10.6052/1672-6553-2013-066
Abstract:This paper mainly studied the dynamic behaviors of bevelgeared rotor system under nonlinear oil film forces. In the bevelgeared rotor system supported on the journal bearings or squeeze film damper, oil film force is an important source of nonlinearity, which is influenced by the structural parameters of bearings, speed of rotor and the acting forces. Under the assumptions such as the rigid rotor, the gear meshing, etc. the dynamic model of bevelgeared rotor system under nonlinear oil film forces was established after considering the bevelgear relationship of the generalized displacement constraints. Because the oil film force is of strong nonlinear characteristics, its dynamic behaviors of the system, such as steadystate responses, Poincaré maps and bifurcation diagrams, were analyzed by using the numerical method. The conclusions are summarized as follows: for the unbalanced bevelgear rotor system, the rotor motions are synchronized with rotational speed at low speeds; with the increase of speed, the complicated phenomena such as the 2periodic motions in the displacement responses occur. These vibration characteristics can provide the theoretical basis for the dynamic design, structural optimization and condition monitoring.
2014, 12(2):139-146. DOI: 10.6052/1672-6553-2014-009
Abstract:The nonlinear dynamics of a fouredge simply supported rectangular thin plate under the combination of the parametrical and external excitations were investigated. Based on the von Karman theory, the formulas of motion for the fouredge simply supported rectangular thin plate under the combination of the parametrical and external excitations were derived. The partial differential equations were discretized to the ordinary differential equations with threedegreeoffreedom using the Galerkin approach. Considering the resonant cases of 1:2:4 internal resonance and principal parametric resonance1/2 subharmonic resonance, the method of multiple scales was utilized to obtain the sixdimensional averaged equations. Furthermore, numerical method was carried out to investigate the periodic and chaotic motions of the thin plate. The results show that the chaotic responses of the thin plate are sensitive to the external excitation.
2014, 12(2):147-152. DOI: 10.6052/1672-6553-2013-072
Abstract:This paper investigated the nonlinear dynamic behavior of seven degreeoffreedom automobile with suspension system of sigmoid magnetorheological damper stimulated by speed control hump(SCH). Based on the Lagrange equations, the twoorder differential equations were developed to describe the motion of automobile, and the fourthorder RungeKutta method was used for the numerical simulation. The bifurcation was analyzed by taking the height of SCH as bifurcation parameter, and the movements of the automobile at some values of height were analyzed by using time series, phase portrait, Poincaré map. The height ranges of SCH were obtained when the chaos vibration appeared, and the route to chaos was analyzed.
2014, 12(2):153-159. DOI: 10.6052/1672-6553-2013-078
Abstract:Based on the threedimensional unsteady incompressible NavierStokes equation and the turbulent model of ktwo equations, and by using the CDF software FLUENT, this paper simulated numerically the aerodynamic characteristics of sound barriers on embankment when the train passes, and studied the changes of pressure fluctuation on sound barrier. The numerical calculation model of a highspeed train passing by the sound barrier on embankment was established, and the aerodynamic pressures on sound barrier were simulated by using the sliding mesh technology in FLUENT, considering the speeds of train 200km/h, 250km/h, 300km/h and 350km/h, respectively. The magnitude and variation of aerodynamic forces on sound barrier were obtained, and the characteristics of aerodynamic pressure along the vertical and longitude directions of the sound barrier were analyzed. The relationship between the amplitude of the sound barrier pressure and train’s speed was fitted. The structural analysis model of sound barrier was established by ANSYS Workbench, and then the aerodynamic pressure was loaded to the sound barrier and the modal analysis and transient dynamic response were researched.
2014, 12(2):160-164. DOI: 10.6052/1672-6553-2014-029
Abstract:Stochastic resonance is a kind of nonlinear phenomenon, which can enhance the weak input signal through the nonlinear system. This paper investigated the phenomenon of stochastic resonance for duffing oscillator. Following experiments were studied: the relation between the output SNR with the noise strength, the relation between the output SNR of the Duffing system with the frequency of the sine signal, and the relation between the output SNR with the damping ratio. The experimental results show that the damping ratio parameter has an important role in the stochastic resonance and there exist a complex nonlinear relationship between the damping ratio parameter with the output SNR.
2014, 12(2):165-169. DOI: 10.6052/1672-6553-2014-017
Abstract:Dynamics analysis and the attitude prediction of the spacecraft were realized by using the knowledge of dynamics and virtual prototyping technology, and the results of theoretical calculations and ADAMS emulation were compared to verify the correctness of the model. At the same time, the factors and fault influencing the attitude of a spacecraft were considered to get the results of separation. Using the ADAMS software for spacecraft ground simulation can avoid the complex dynamics calculation, and has the widespread application prospect.
2014, 12(2):170-177. DOI: 10.6052/1672-6553-2014-027
Abstract:Taking the structural characteristics and the complexity operating environment of the whole aeroengine system as the research background, the Lagrange approach was employed to establish the flexuraltorsional dynamic model for a doubledisk rotor subjected to the influence of imbalance exciting force and axial movement caused by the thermal expansion. Due to the axial movement of the shaft caused by the nonuniform distribution of temperature and thermal expansion properties, the analytical expressions of the surface rubbing force and moment were derived respectively. Finally the fourthorder RungeKutta method was adopted to solve the dynamic model. Numerical analysis on the dynamical response of the system shows that the temperature stress accumulated by thermal expansion, axial movement of the shaft, and surface rubbing moment, are all the key factors, which would change the inherent physical properties and cause flexuraltorsional vibration of the doubledisk rotor.
2014, 12(2):178-182. DOI: 10.6052/1672-6553-2014-022
Abstract:Based on meshless natural neighbour petrovGalerkin method, a novel meshless method was developed to solve transient heat conduction problems with a source parameter. The essential boundary conditions cannot be enforced directly when the noninterpolative moving least squares (MLS) approximation is used. In order to overcome this difficulty, the natural neighbour interpolation was employed instead of the moving least squares approximation to construct trial functions. The local weak forms of the transient heat conduction problems were satisfied locally in a series of polygonal subdomains, which can be constructed easily with Delaunay tessellations. The traditional twopoint difference technique was selected for the time discretization scheme. A numerical example demonstrates the validity and effectiveness of the presented method.
2014, 12(2):183-187. DOI: 10.6052/1672-6553-2014-025
Abstract:PMSM due to little harmonic, high precision torque, commonly is used in the servo system and the high performance speed control system. In this paper,the physical model of PMSM is simplified and the mathematical model of the motor is established in order to facilitate research.Thispaper uses id=0 control manner which is the simplest manner is vector control methods,motor electromagnetic torque equation is established based on rotor field oriented vector control.The system model, speed and current control block are build and simulated with MATLAB/Simulink.Simulation results shows that the waveform is consistent with thoretical analysis,the model has fast response and small overshoot.The system runs stably with good dynamic and static characteristics. The simulation makes full use of modularization design. All the parameters and their influence on the system can be changed and observed.It also can easily validate the control strategies and select the most suitable one. So this kind of simulation is good for system design and adjusting and validating.
2014, 12(2):188-192. DOI: 10.6052/1672-6553-2014-014
Abstract:In the paper, two nonlinear estimation methods based on nonlinear chaotic theory, surrogate data method and Lyapunov exponents, are used to distinguish the difference of nonstationary signals. After brief introduction of the corresponding algorithms, two typical different nonstationary signals measured from a thinplate structure with different nonlinear constraining boundaries are taken to compare by using the above two methods respectively. The obtained results demonstrate that the apparently similar signals are distinguished effectively in quantitative way with applying above nonlinear chaotic analyses.