• Current Issue
  • Archive
  • Most Downloaded
    Select AllDeselectExport
    Display Method:
    2025,23(5):1-8, DOI: 10.6052/1672-6553-2025-004
    Abstract:
    This paper presents a novel physics-constrained parallel network for nonlinear dynamical system identification. The fundamental concept is to employ implicit governing equations to guide neural network training, constraining the solution space and inducing interpretable models. Firstly, inspired by sparse regression methods, a sparse regression layer equipped with a function library is developed to characterize system nonlinearity. Secondly, a state-constrained parallel network architecture is constructed to enforce derivative relationships among state variables, constraining the outputs of three parallel subnetworks and reconstructing the full-state outputs under partially noisy state measurements. Finally, the sparse regression network layer is integrated with the state-constrained parallel network to form the physics-constrained parallel network, yielding full-state outputs and explicit closed-form dynamical formulations simultaneously. An alternate optimization method is developed to optimize the sparse regression network layer and the state-constrained parallel network sequentially, enhancing optimization efficiency. The term “physics-constrained” herein refers to the state dependency constraints and the residual loss derived from the learned governing equation via the sparse regression layer. Through this strategy, the proposed framework delivers a physically interpretable model for nonlinear dynamical systems from partial noisy measurements. Numerical simulations and experimental studies demonstrate the effectiveness, robustness, and applicability.
    2025,23(5):9-20, DOI: 10.6052/1672-6553-2024-102
    Abstract:
    System identification methods are primarily divided into two categories: one is based on first-principles modeling, and the other on data-driven modeling via machine learning. Although data-driven models provide higher accuracy, their lack of physical interpretability can lead to challenges in validating model reliability, thereby limiting their widespread application in engineering. As a novel data-driven modeling approach, the Elementary Mechanical Network (EMN) adheres to the existing mechanical theory framework, ensuring that the identified results can be interpreted from a mechanical perspective. However, due to the numerous constraints within the EMN structure, its modeling accuracy is inferior to other data-driven methods such as neural networks. Therefore, enhancing the network's fitting capability within the existing model architecture is key to further development and application of EMN. This paper first develops a set of differential-algebraic explicit solution frameworks for EMN from the perspective of numerical computation and designs numerical solving algorithms, including the Euler method, the second-order Runge-Kutta method, and the fourth-order Runge-Kutta method based on this framework. Next, numerical examples are provided to analyze the computational accuracy and initial sensitivity of EMN under the new framework, while comparing the three numerical methods in terms of solving capability, stability, and time complexity, offering a basis for subsequent method selection. Finally, simulation experiments are conducted to build an equivalent model of LuGre friction by training the EMN. The experimental results show that the trained EMN achieves a mean square error (MSE) of only 0.0018 and can effectively reproduce the internal state variables of the model, verifying the feasibility of EMN for both quantitative and qualitative feature approximation.
    2025,23(5):21-26, DOI: 10.6052/1672-6553-2025-033
    Abstract:
    This paper proposes a parameter identification method for single-degree-of-freedom nonlinear systems based on backbone and envelope curves. The method uses the system's backbone and envelope curves as observational data, combining them with their analytical expressions to obtain the posterior joint distribution of physical parameters through Bayesian estimation. Subsequently, the Markov Chain Monte Carlo method is employed to derive the marginal probability distributions of each physical parameter. The proposed approach avoids the need for complex time-domain numerical integration, significantly improving computational efficiency. Furthermore, the effect of noise is considered, and the results of the Hilbert transform and the zero-crossing method for estimating the backbone and envelope curves are compared. To validate the accuracy of the proposed method, it is applied to identify the Duffing oscillator with a discussion of the impact of noise at different levels. The results demonstrate that the proposed method is accurate in identifying the physical parameters of single-degree-of-freedom nonlinear systems under noisy environments.
    2025,23(5):27-35, DOI: 10.6052/1672-6553-2025-007
    Abstract:
    Breathing cracks are a common type of local nonlinear damage, such as fatigue cracks and delamination damage, whose “breathing” effect causes cyclic changes in the local structural stiffness, which increases the difficulty of damage characterization. Traditional damage identification methods based on nonlinear vibration characteristics are difficult to accurately locate and quantify local breathing cracks due to limited measurement information. With the development of full-field vibration displacement measurement technology, the vibration displacement field on the surface of plate structures can be readily obtained, which brings new opportunities for the accurate identification of breathing cracks. In this paper, a nonlinear pseudo-excitation based method is proposed to localize the “delamination-type” breathing crack in plate structures by combining the vibration displacement field information and the local dynamic equilibrium. The method firstly performs feature extraction and efficient nonlinear feature parameter identification of the vibration displacement field by constructing orthogonal basis functions, and then calculates the nonlinear pseudo-excitation by using the identified super-harmonic frequencies and their characteristic deflection shapes in order to realize the high-precision localization of breathing cracks. Finally, the correctness of the proposed method is verified by a thin plate structure with “delamination-type” breathing cracks.
    2025,23(5):36-43, DOI: 10.6052/1672-6553-2024-100
    Abstract:
    Delay differential equations are widely used to describe dynamic connections between system’s current states and its past states. They are particularly suited for modelling complex systems with delays, such as dynamic systems arisen from biology, engineering and physics. Since delay effects can significantly impact system dynamic behaviour, control performance and stability, accurate identification of delay parameters has become a core challenge. To improve both accuracy and efficiency, this study proposes a delay parameter identification algorithm based on adjoint equations and the gradient descent method. By leveraging the analytical properties of adjoint equations, this method solves the adjoint system backward in time, allowing for the precise calculation of the gradient of the system response with respect to the parameters, thus facilitating efficient parameter updates. This study details the mathematical derivation of the algorithm and develops a computational framework on the Python platform, incorporating automatic updates, dynamic interpolation, and a solver for delay differential equations with time-varying parameters. By simplifying the algorithm and utilizing parallel computing, the solution process is optimized to reduce computational complexity, enhancing its practical applicability. To validate the effectiveness of the algorithm, a numerical identification experiment is conducted for a two-degree-of-freedom nonlinear spring-mass system. The results demonstrate that the method accurately identifies the system delay parameters while maintaining a low error margin.
    2025,23(5):44-51, DOI: 10.6052/1672-6553-2025-005
    Abstract:
    This study utilizes the Sparse Identification of Nonlinear Dynamical Systems (SINDy) algorithm to optimize the nonlinear dynamic model of the economic system based on the generalized Lotka-Volterra model. The optimized model is applied to explore the complex dynamic relationships among four variables: industrial added value, financial added value, total exports, and total imports in China, including linear, interactive, and higher-order influence relationships. Compared to the traditional Lotka-Volterra model, the model optimized by the sparse identification algorithm demonstrates higher accuracy in fitting and short-term forecasting. Additionally, the model is able to identify key components within the system, offering stronger interpretability in economic terms.
    2025,23(5):52-58, DOI: 10.6052/1672-6553-2025-045
    Abstract:
    The importance of discovering significant variables from a large candidate pool is now widely recognized in many fields. There exist a number of algorithms for variable selection in the literature. Some are computationally efficient but only provide a necessary condition for, not a sufficient and necessary condition for, testing whether a variable contributes or not to the system output. The others are computationally expensive. The goal of the paper is to develop a directional variable selection algorithm that performs similar to or better than the leading algorithms for variable selection, but under weaker technical assumptions and with a much reduced computational complexity. It provides a necessary and sufficient condition for testing whether a variable contributes or not to the system. In addition, since indicators for redundant variables aren’t exact zeros, it is difficult to decide whether variables are redundant or not when the indicators are small.To solve this problem, a penalty optimization algorithm is proposed to ensure the convergence of the set. Simulation and experimental results verify the effectiveness of the directional variable selection method proposed in this paper.
    2025,23(5):59-68, DOI: 10.6052/1672-6553-2025-028
    Abstract:
    In the field of vibration control, bistable nonlinear energy sinks (BNES) represent a highly efficient vibration suppression structure where energy harvesting and vibration control performance depend on the optimization and design of nonlinear system parameters. This paper investigates parameter identification in systems containing bistable nonlinear energy sinks. Leveraging the properties of stable equilibrium points in bistable systems, we propose a reference point shifting method that integrates Gaussian kernel density peak estimation to enhance the time-domain nonlinear subspace approach. Numerical simulations and experimental validations were conducted to analyze the impacts of various noise levels on equilibrium point estimation accuracy and nonlinear parameter identification, as well as the sensitivity of parameter results to steady-state point estimation errors. The results demonstrate that under 20% noise intensity, the equilibrium point estimation error remains below 10%, while the nonlinear parameter estimation error is approximately 20%. This method effectively identifies cubic stiffness and Coulomb damping parameters in bistable nonlinear energy sink systems.
    2025,23(5):69-81, DOI: 10.6052/1672-6553-2024-101
    Abstract:
    The Naive Bayes classifier, with its solid foundation in probability theory, exhibits significant classification advantages when dealing with datasets containing uncertain features and noise interference. With the increasing complexity of social data, the method of measuring prior probability based on proportion has to some extent limited the performance of Naive Bayes classifiers. The construction of prior probabilities is an important issue in Bayesian classification research and a crucial factor in determining the accuracy of Naive Bayes classification. How to effectively estimate and construct the highest priority probability has gradually become a research topic of concern for scholars. Therefore, this article introduces t distribution variation and adaptive weights to improve the individual update formula of Hippopotamus Optimization Algorithm (HOA). Based on this improvement, an optimization approach is proposed, which integrates the optimized algorithm with the construction of Bayesian optimal priors using both training and testing samples. This method has achieved superior classification performance. The specific process is to collect system data and divide it into training set, validation set, and test set. The model parameters obtained from the training set are used as the initial input for the Bayesian classifier in the validation set. Then, with classification accuracy as the objective function, the improved Hippopotamus Optimization Algorithm is used to search for the Bayesian optimal prior in the validation set. Finally, the optimization result is used as the prior in the test set to obtain the classification accuracy. The proposed method was tested by switching circuit system simulations and compared with other mainstream classification algorithms. The results showed that the proposed method exhibited high classification accuracy.
    2025,23(5):82-90, DOI: 10.6052/1672-6553-2024-111
    Abstract:
    To address the issue of low accuracy in local damage identification of beam structures based on modal parameters, a combined damage identification method integrating the theory of flexural wave propagation and wave theory is proposed. Firstly, the motion equation governing the flexural deformation of slender beams under the Bernoulli-Euler beam model is derived, and theoretical analysis of flexural wave propagation in the beam is conducted to obtain the wave propagation solution. Secondly, flexural wave in the beam is identified using wave theory. Finally, a damage index based on the relationship between beam stiffness and flexural wave velocity is constructed to identify structural damage, including its location and degree. The method is validated through numerical models and laboratory experiments, demonstrating it has good noise immunity.
    2025,23(5):91-97, DOI: 10.6052/1672-6553-2024-095
    Abstract:
    Gait trajectory planning is a critical component in the control of powered lower limb prostheses. In order to achieve coordination between the prosthesis and the intact limb, existing gait trajectory planning methods generally employ data-driven modeling, which directly maps the movement of intact limbs as the reference trajectory of prostheses. However, these methods often suffer from high modeling complexity and poor perturbation resilience. To address this issue, we proposed a novel gait trajectory planning method driven by the delayed feedback reservoir. In this approach, we utilized the Mackey-Glass oscillator as the nonlinear node of the reservoir, with the hip angle of the amputatied side serving as the input. The output is the mapped knee angle of the prosthesis. Notably, the output of the reservoir is the linear superposition of the virtual node states, offering significant advantages in terms of high global convergence and fast convergence speed during training and computing. Furthermore, we deployed the delayed feedback reservoir on the FPGA hardware and utilized serial communication to achieve data interaction with the STM32 microcontroller, allowing for real-time wearability experiments on a powered lower limb prosthesis. The experimental results show that our model achieves a correlation coefficient of 0.8377 between intact limb and prosthesis under normal walking and 0.7436 under perturbation, demonstrating a strong correlation. The jerk value also reflects the model’s robust resistance to perturbations, with an average jerk of 47 979 deg/s3, which is approximately 31% lower than that of the intact limb. This demonstrates that DFR possesses significant perturbation resistance, offering a new solution for prosthesis control.
    Select AllDeselectExport
    Display Method:
    2014,12(3):269-273, DOI: 10.6052/1672-6553-2014-043
    [Abstract] (3483) [HTML] (0) [PDF 336.30 K] (21730)
    Abstract:
    Aiming at the problem that the longitudinal modes of structural system of rocket need to be identified from its integral modes in engineering, a method that automatically identifies the longitudinal modes of structural system of rocket was proposed according to the theory of modal effective mass. Taking the vibration characteristics of system with lumped mass as a computing example, applying the finite element software, the beam model of system with lumped mass was established, and the longitudinal modes of the system were automatically identified based on the method. Compared with the system modal information calculated by the method of modal analysis, this automatic identification method not only can accurately identify the longitudinal modes of vibrating system, but also has automatic and high efficiency identification feature. It provides a theoretical basis for the dynamic model of POGO vibrating system in liquid rockets and other model of engineering systems to be accurately and promptly established.
    2014,12(3):193-200, DOI: 10.6052/1672-6553-2014-046
    [Abstract] (3312) [HTML] (0) [PDF 748.46 K] (19168)
    Abstract:
    The spacecraft's ability to adapt to the harsh dynamics environment is critical for the whole space mission. Vibration test control technology is the key part of the dynamic environment test. The current progress, fundamental principles and key techniques development level of the spacecraft and vibration control algorithms overseas were analyzed. The basic ideas, effective ways and suggestions were given to domestic following research.
    2017,15(5):385-405, DOI: 10.6052/1672-6553-2017-039
    [Abstract] (2114) [HTML] (0) [PDF 1.91 M] (18986)
    Abstract:
    In this review article, the growth and related academic communications in the dynamics of multibody systems are firstly surveyed. Then, the recent advances in the numerical algorithms for solving the dynamic equations of flexible multibody systems, the contact/impact dynamics of flexible multibody systems and the deployment of flexible space structures are systematically reviewed, together with several open problems of concern. Finally, some suggestions are made for the prospective researches on the dynamics of flexible multibody systems.
    2014,12(1):18-23, DOI: 10.6052/1672-6553-2013-068
    [Abstract] (3209) [HTML] (0) [PDF 1.13 M] (18699)
    Abstract:
    The electromechanical coupling model of cantilevered piezoelectric harvester was developed by considering the nonlinearities of piezoelectric material, based on Hamilton theory, Rayleigh-Ritz method, Euler-Bernoulli beam theory and constant electrical field across the piezoelectric element. The response characteristics of the system were investigated numerically, and the influences of piezoelectric material nonlinear coefficient on the system response were analyzed. By exploring the nonlinear characteristics of the piezoelectric vibrator near the resonant frequency, the nature of the multi-solutions and jump phenomena in the resonance region was revealed. The results were verified experimentally. which provides a theoretical basis for the study of nonlinear mechanism of piezoelectric power generation system.
    2014,12(3):243-247, DOI: 10.6052/1672-6553-2014-054
    [Abstract] (2598) [HTML] (0) [PDF 1.07 M] (18263)
    Abstract:
    Random vibration test is very important to the aerospace equipment. The windage of ASD outside the frequency bandwidth was analyzed. The reason, premonition, affection and effective way were given. And the commonly used random vibration test and vibration test metrology standard for the ASD outside the frequency bandwidth were analyzed.
    2016,14(2):97-108, DOI: 10.6052/1672-6553-2015-009
    [Abstract] (2571) [HTML] (0) [PDF 1.87 M] (18107)
    Abstract:
    Based on the current research status of multi agents system control theory and technology, the paper makes a detailed overview for unmanned ground systems. From two aspects of behaviour and task cooperative control for multi agents, the relevant theory and application problem is discussed. Moreover, some existed open problems are presented and a possible future development is proposed. For unmanned ground systems, cooperative control will be of great importance in promoting social and military benefits and maximizing the executive function of ground mission.
    2015,13(5):361-366, DOI: 10.6052/1672-6553-2014-064
    [Abstract] (1359) [HTML] (0) [PDF 826.19 K] (17969)
    Abstract:
    Dynamic and control systems often contain uncertain parameters that may result in uncertain predictions. In the interest of quantifying the effects of parameter uncertainties on response variability, this paper develops a stochastic response surface based method for the sensitivity analysis of uncertain parameters. Stochastic response surfaces were firstly constructed to describe the explicit relationships between uncertain parameters and responses. Then partial derivations were performed on the mathematical expressions of stochastic response surfaces in order to obtain sensitivity indices that simultaneously embody the effects of parameter means and standard deviations. Lastly, the developed method has been verified against a numerical cantilever beam containing uncertain geometric and material parameters. The sensitivity analysis results were compared with those given by the analysis of variance method.
    2014,12(3):225-229, DOI: 10.6052/1672-6553-2014-051
    [Abstract] (2552) [HTML] (0) [PDF 1.38 M] (17862)
    Abstract:
    Based on the staggered solution procedure of ANSYS and CFX software, the fluid structure coupling response of projectile during tail slapping has been researched. Structural response was simulated by using FEM and flow field was simulated by using inhomogeneous model and SST turbulence model. Finally, the influences of fluid structure coupling effect have been analyzed and the change law of body stress has been given.
    2013,11(1):12-19, DOI: 10.6052/1672-6553-2013-003
    [Abstract] (2536) [HTML] (0) [PDF 530.95 K] (17726)
    Abstract:
    The dynamics of the whole aero-engine system has always been the important part that cannot be neglected in the research and design of the engine, as the framework of the engine, the vibration of the casing directly reflects the level of the whole aero engine vibration. In this paper, an analysis was made on the research of the problems and fault classification of aero-engine casing dynamics, and an overview was made on the research of present situation, development trend, problems and solutions of the domestic and foreign of casing dynamics, which expanded the present situation of the Inclusiveness problems of aero-engine casing dynamics. Finally, some proposals were put forward for the development of the casing dynamics suitable for our country aero-engine technology level.
    2008,6(4):301-306, DOI:
    [Abstract] (1348) [HTML] (0) [PDF 0.00 Byte] (17439)
    Abstract:
    The problem of P and PI feedback control to a time delay system was investigated,with the emphasis on the determination of the feedback gains that ensured the asymptotical stability of the delayed system. By means of Lambert W function,the feedback gain of P control can be expressed explicitly,so that the optimal feedback gain can be easily obtained. For the system under a PI control,the stable region of the feedback gains was determined on the basis of stability switches and D subdivision,and the optimal feedback gains that enabled the system to admit maximal stable margin were figured out numerically by using Lambert W function. From the viewpoint of computation,the present method is much simpler than the available methods.
    2012,10(1):21-26, DOI:
    [Abstract] (940) [HTML] (0) [PDF 567.09 K] (17415)
    Abstract:
    A discrete finite dimensional dynamical model was built to describe the space large overall motion of tethered satellite system with an infinite dimensional viscoelastic tether in a long time. The tethered satellite system is a complex nolinear dynamic system. Considering the tether’s viscoelasticity, distributed mass and space form, the established improved bead model can meticulously describe the tether’s vertical and horizontal vibration. According to tether’s characteristic of tensile and not compressive, the slack tether unit model was set up to accurately reflect real stress of tether. The determination of the number of degrees of freedom of the system was studied. Based on numerical integral calculation, the dynamic response was obtained via numerical simulation of the deployment, retrievement and retainment process of tethered satellite system in a long time. The result is convergent. The simulation proves the important role of the stable equilibrium position in the dynamics of tethered space system.
    2014,12(2):183-187, DOI: 10.6052/1672-6553-2014-025
    [Abstract] (1481) [HTML] (0) [PDF 811.52 K] (17133)
    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(3):205-209, DOI: 10.6052/1672-6553-2014-059
    [Abstract] (2189) [HTML] (0) [PDF 467.15 K] (14618)
    Abstract:
    This paper investigated the passive nonlinear vibration control method used for energy absorbing in structures of spacecrafts. The structure and the dynamic model of the nonlinear energy sink which could adapt to the space environment were proposed. As nonlinear spring could not be acquired easily in reality, we proposed a new design for the NES based on employing an asymmetric NES force which was generated by two pairs of aligned permanent magnets. Then, the dynamic model for a cantilever beam structure coupled with nonlinear energy sink had been built theoretically. In addition, the passive vibration suppression effect of the nonlinear energy sink on the cantilever beam structure under transient excitation had been analyzed through Galerkin method and numerical analysis method. The results showed that the NES acquired up to 92% dissipation of the system energy imposed by shock excitation, hence the NES could adapt to the space environment and improve the reliability of space system.
    2014,12(3):283-288, DOI: 10.6052/1672-6553-2014-061
    [Abstract] (3169) [HTML] (0) [PDF 479.50 K] (13909)
    Abstract:
    A method was presented to analyze the nonlinear flutter. Based on this method, the flutter characteristics of the high aspect wing were illustrated. The numerical results show that the flutter speed is decreased when the first horizontal bending mode involved. Secondly, this study discussed how the main direction of the composite influenced the character of the nonlinear vibration and flutter, and established the method of the flutter clipping to the high aspect wing. And the result shows that the stiffness of structure can be changed by changing the main direction of the composite. It mainly changes the horizontal bending mode, makes the main direction tend to the trailing edge, and then makes the section line move to the leading edge. Further analyzing the nonlinear flutter reveals that it is the changing of the horizontal bending mode that causes the flutter speed change obviously. And by the section line of this mode moves ahead, the flutter speed will become larger. In the study, two examples were illustrated to validate its truthiness.
    2013,11(4):357-362, DOI: 10.6052/1672-6553-2013-041
    [Abstract] (1518) [HTML] (0) [PDF 350.50 K] (12060)
    Abstract:
    At present, the main task of designing a mounting system of automotive engine powertrain is to select appropriate stiffness, position and angle of mounting components so that free-vibration modal frequency of the mounting system can avert from the exciting-force frequency at the idle speed of the engine and the natural frequency of vibration of the vehicle body and that the decoupling degree of each mode shape is increased as far as possible, so as to improve the vibration-isolation effect of the mounting system. The design of a mounting system based on strict decoupling at predetermined frequencies is to make the modal frequencies of the designed mounting system completely equal to the frequencies predetermined in accordance with the frequency planning of automotive design, and to enable strict decoupling of each mode shape of each mode, i.e., the decoupling degree of vibration energy in every direction equals to 1. Based on a free-vibration equation for a mounting system, this paper presents an equation system for designing a mounting system with strict decoupling at predetermined frequencies, provides a solving method for this equation system by using the theory of generalized inverse matrix or method of constructing function, so as to provide an optimal design method more efficient and simpler than the current modal optimization method of mounting system. Relevant example has validated the correctness of equations and solving method of the strict-decoupling design at predetermined frequencies.
    2016,14(3):247-252, DOI: 10.6052/1672-6553-2015-052
    [Abstract] (1957) [HTML] (0) [PDF 2.18 M] (9155)
    Abstract:
    Tires are the only carrier of the contact between the vehicle and road surface. Their mechanical property is important for analysis and control on the vehicle dynamic response. At present, the tire simulation mostly focuses on the steady state model. But it can not describe the dynamic characteristic of the tire accurately. Therefore, it plays a significant role to add the dynamic tire model in the vehicle dynamics simulation. The tire friction model in the multi body dynamical software ADAMS is static, where the friction is regarded as a static value. However, in actual, the friction between the tire and road surface is dynamic, and it should be a dynamic function of the relative velocity and displacement. To this end, in this paper, the dynamic tire LuGre model using the Matlab/Simulink software is constructed. Through connecting the interface with Adams/Car, co simulation between the vehicle model and the simulink tire model is carried out in order to achieve the dynamic contact between tire and road and improve the accuracy of vehicle system analysis.
    2014,12(1):36-43, DOI: 10.6052/1672-6553-2013-110
    [Abstract] (2273) [HTML] (0) [PDF 2.22 M] (7731)
    Abstract:
    The coupling nonlinear dynamic model of dual rotor system was established by using finite element method, and then the critical speed of revolution and mode shape were calculated by using the software MATLAB. In addition, the unbalance responses of dual rotor system were studied, and the vibration performances in different speeds of dual rotor casing systems were obtained. The research provides a theoretical basis for the design of the dual rotors system in engineering.
    2014,12(3):253-258, DOI: 10.6052/1672-6553-2014-056
    [Abstract] (2161) [HTML] (0) [PDF 1.00 M] (6101)
    Abstract:
    Taking account of the structural stiffness and the low order vibration frequencies, two schemes of multi-objective topology optimization were proposed to obtain the best aircraft lifting-surface structural design. Based on penalized density theory, the scheme one (named as constrain method) is to convert the multi-objective optimization to single-objective optimization by considering the minimum structural mass as the objective with constraints of reference points displacements and the low order vibration frequencies. The scheme two (named as the combination of constrain method and criterion function method) settles the multi-objective optimization by defining combined compliance index (CCI) as the objective, with the constraints of volume fraction and the low order vibration frequencies. The CCI is the function of structural compliance and low order vibration frequencies. Numerical results demonstrate the proposed schemes not only realize reducing the structural mass but also raise the first and second order frequencies.
    2014,12(3):201-204, DOI: 10.6052/1672-6553-2014-048
    [Abstract] (2265) [HTML] (0) [PDF 296.79 K] (5792)
    Abstract:
    Non-linear factors cannot be avoided in the design of aircraft structures. In this paper, a two-degree-of-freedom airfoil and cubic stiffness nonlinearities in pitching degree-of-freedom operating in supersonic flight speed regimes has been analyzed. The averaging method and the theory of flutter were used to analyze the nonlinear dynamic system of the dualistic airfoil in the supersonic flow. Then the correctness of the theoretical calculation was verified by numerical calculation, and the analysis result was given.
    2014,12(1):62-66, DOI: 10.6052/1672-6553-2013-097
    [Abstract] (1683) [HTML] (0) [PDF 832.87 K] (5312)
    Abstract:
    A spline finite point method was presented to study the natural frequency of arch. The displacement mode shape function of the arch free vibration was simulated with a linear combination of cubic B spline. The free vibration frequency equation of arch structures was derived according to Hamilton principle, in which the effect of the dead load was considered. Meanwhile, the effect of the dead load on the natural frequency of arch structures was analyzed. The results show that the natural frequency of arch is reduced. The effect of influence depends on the stiffness of the arch itself. When the arch stiffness is certain, the bigger the rise span ration and the radius to thickness ration, the higher the effect of the dead load on the natural frequency of arch structures.

External Links Links

WeChat

Mobile website