Journal of Vibroengineering
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A dynamic modeling method for helical gear systems
Get PDFDynamic modeling for gear systems is very important for accurately predicting the dynamic responses during the gear engagements. During the modeling, meshing force must be determined, and it is usually calculated by the product of the relative displacement along the line of action (LOA) and the meshing stiffness. At present, the relative displacement calculation for helical gear systems is very complicated by several existing methods because the complicated geometric relationships need to be derived for determining the spatial positions of two meshing points along LOA. In this study, a simple method for calculating the relative displacement along LOA is presented based on ANSYS software. And on this basis, a new finite element modeling method for a helical gear transmission system with multiple shafts is developed, where the influences of shafts and bearing flexibilities are considered. Moreover, the proposed method is validated by comparing the dynamic characteristics, such as natural characteristics and vibration responses, with those obtained from Kubur’s method and Zhang’s method
Pattern recognition of rigid hoisting guides based on vibration characteristics
Get PDFA test rig is built to simulate the typical fault patterns of rigid hoisting guides and to collect vibration and inclination signals. In this work, we use these signals to perform data mining for fault-pattern recognition. Parameters are initially defined by analyzing collected signals. Then, the importance of each parameter is calculated using the boosting-tree method. Some valuable parameters are retained. To establish a data-mining algorithm that works remarkably for the fault recognition of rigid hoisting guides, six different algorithms including the boosting tree, K-nearest neighbor, MARSpline, neural network, random forest, and support vector machine are compared. Results show that the best performance is that of the boosting-tree algorithm, whose mechanism is then presented in detail
Comparative vibration study of EN 8 and EN 47 cracked cantilever beam
Get PDFSince earlier days, most of the failures encountered by the structures or machines are mainly due to material fatigue. The dynamic behaviour of the beam may change when cracks begin to appear in it. Knowledge of these changes in the dynamic individualism is important in crack detection as well as in structure or in machine design. This paper deals with systematic study on the free vibration of Euler-Bernoulli beam containing open edge transverse cracks. In this study, two springs steel materials (EN 8 and EN 47) are considered. The effect of the top side cracks and bottom side cracks on the natural frequency of a cantilever beam is discussed. The natural frequency of a cracked case cantilever beam is investigated numerically using FE analysis software ANSYS. Experimental work is done by using DeweFRF to investigate the natural frequency of cracked beams for strong validation of the numerical results. The results of this study suggest that the average value of natural frequencies for all top side cracked beams are identical to the average value of natural frequency for all bottom side cracked beams. This is true for both EN 47 and EN 8. Hence, it is clear that the dynamic characteristic (natural frequency) is not changing, when same configuration of cracks is either on top or bottom side of the beam. The natural frequencies for EN 8 material are comparatively on higher side than EN 47 material for the same crack configurations. In most of the cracked cases, the damping effect of EN 47 is greater than EN 8. It is also found that as crack location increases at constant crack depth, then natural frequency increases. At the last location, as crack depth increases, natural frequencies almost remain same. It is observed that, the presence of top side crack and bottom side crack of the same configuration in the cantilever beam is not a function of natural frequency, when cantilever beam is of a square cross section
Vibration and aeroelastic control of wind turbine blade based on B-L aerodynamic model and LQR controller
Get PDFVibration and aeroelastic control of anisotropic composite wind turbine blade modeled as symmetric layup beam analysis have been investigated based on Beddoes-Leishman (B-L) dynamic stall aerodynamic model and linear quadratic controller. The blade is modeled as single-cell thin-walled beam structure, exhibiting flap bending-lag bending-twist coupling deformation, with constant pitch angle set. The stall flutter and aeroelastic control of composite blade are investigated based on some structural and dynamic parameters, with structural damping computed. The aeroelastic partial differential equations are reduced by Galerkin method, with the nonlinear aerodynamic forces computed by the method of fitting static elastic coefficients. Linear quadratic controller is applied to enhance the vibrational behavior in stall situation under divergent conditions and stabilize displacements that might be unstable in the absence of control
Chaos control of a multi-dimensional chaotic mapping system by modified stability transformation method
Get PDFFor the multi-dimensional chaotic mapping system with various forms of bifurcations, it is found that the spectral radius around the static bifurcation point is approximately equal to one and the convergence speed for traditional stability transformation method (STM) which is used to stabilize the unstable fixed points is fairly slow. In this paper, a modified STM is proposed to efficiently stabilize a 3D chaotic mapping system to stable fixed points. Firstly, according to the information of the fixed point, the stability matrix C is derived, demonstrating that it is unnecessarily an involutory matrix for STM that can also stabilize chaotic system to the fixed point. Then, the critical parameter qcrit that satisfies convergence condition and the optimal parameter qopt corresponding to best performance for STM are determined respectively. Moreover, STM is combined with Newton method (NT) to overcome the disadvantage of slow convergence around the static bifurcation point without requiring a priori information of fixed point. It is indicated that the number of iterations, the absolute and relative errors between the convergent value and analytical fixed point for combined STM-NT decrease enormously comparing with that of traditional STM. Finally, numerical analysis verifies the high efficiency of modified STM proposed in this paper
Adaptive backstepping sliding mode control for heavy-weight airdrop operations
Get PDFThis paper proposes an adaptive backstepping sliding mode flight control method that is compatible with heavyweight cargo airdrop. The goal is to maintain the plane states during cargo extraction process, in the presence of uncertainties of both constant and time-varying types, as well as matched and unmatched types. A backstepping sliding mode flight control law with parameter adaptation is presented based on the plane-cargo dynamics in strict-feedback form. The control approach consists in having an adaptation law that approximates the disturbance and uncertain aerodynamic function, which is separated from the complex nonlinearities. Also, the adaptation algorithm with projection can bound the estimated function. This ensures the robustness of the controller against time-varying disturbance and uncertainty. The convergence performance and robustness property of the control law are proved by the Lyapunov theory. The control effect is evaluated on a transport plane performing a maximum load airdrop task in a number of simulation scenarios
Optimization of vibration reduction of the rubber floating-slab tracks
Get PDFThe floating-slab track is one of the best methods to reduce the vibration from the underground railway. In this paper, the rubber floating-slab track was studied. The train-track model coupled with the track-tunnel-surrounding soil model was built, which was verified by the results of the in-site test. Through this model, the quality of the rubber floating-slab track was optimized by the multi-island genetic algorithm. The optimized Z vibration level was reduced by 4.92 dB with the density of the floating slab 2306 kg/m3, the Young’s modulus of the floating slab 3.21×1010 N/m2, the density of the rubber bearing 730 kg/m3 and the Young’s modulus of the rubber bearing 9.55×108 N/m2
Research on ride comfort and safety of vehicle under limited conditions based on dynamical tire model
Get PDFDuring driving of a vehicle on road, the tires are undertaking load conversion of the vehicle under various driving conditions and various road conditions within contact patches. As for the contact condition between tire and road, it is often deemed as composed by spring and damping element. The contact with road is always simplified as point contact. Besides, static friction model is adopted, which has ignored physical property of friction and dynamic process of establishment of friction force. It is far from sufficient for current vehicle and road safety design. In this paper, ADAMS software is applied to establish a multi-body dynamics model of heavy vehicle, actual vehicle data was adopted to check virtual sample vehicle, and the Strikbeck dynamical friction property is introduced to tire model during rolling contact between tire and payment, interface of Simulink with ADAMS is applied to put forward a complete vehicle dynamic model truly reflecting the process of dynamic contact between tire and road, and furthermore the correctness and availability of dynamic tire model are verified through comparison with classic Pac2002 tire model. As for dynamic behaviors of heavy vehicle in special sections, finite element method (FEM) is applied to put forward a new 3D complicated road model construction method to construct roads of different classes and long-downhill paths of different S-curves. Simulated analysis of the influence of different speeds, different classes of random roads, different slopes and different adhesion road models on ride comfort of vehicle driving was implemented through utilization of event editor and drive control file, and speed limit standards under different conditions are put forward, so as to provide theoretical basis for road alignment design and reasonable driving speed. Finally, the influence and changing rules of different speeds, different classes of random roads and different slopes on driving safety are discussed from the perspectives of each radial force of tire, alignment torque, sideslip angle and roll angle
Levitation chassis dynamic analysis and robust position control for maglev vehicles under nonlinear periodic disturbance
Get PDFIn this paper, an experiment for decoupling the dynamic behavior of the levitation chassis of maglev vehicle with four electromagnetic suspension (EMS) modules is implemented, which validated that the stable suspension of maglev vehicle can be achieved by controlling individual EMS modules. Then, a dynamic model for single EMS module is established. A PD controller is designed to control the vertical position of the maglev vehicle. Simulations illustrate that the robustness of the controller is weak against the periodic disturbance. To improve the robustness of the controller, a nonlinear control law for disturbance rejection is applied by combining with a periodic disturbance estimator with an adaptive notch filter, which is capable of compensating exogenous nonlinear periodic disturbance. Different from using the existing control laws, the structure, parameters and period of the disturbance is not required. Moreover, the controller designed in this work satisfies the requirement of unidirectional force input. Simulation results are presented to demonstrate the excellent dynamic performance with the proposed robust controller
Numerical analysis of evaluation methods and influencing factors for dynamic stability of bedding rock slope
Get PDFAs the inclination of a bedding surface is consistent with the inclination of a slope, the stability of a bedding rock slope is relatively poor, especially under dynamic loads such as earthquake and blasting. In the dynamic stability analysis of slope, the evaluation methods and influence factors of slope stability are two important concerns. Therefore, two typical bedding rock slopes are respectively established by FLAC3D to study the above concerns. The pseudo-static method, dynamic time-history method and dynamic strength reduction method is used to evaluate the dynamic stability of the model slope, and the applicability of the three methods is compared. The influence of five parameters including dynamic load frequency, slope angle, slope height, strata inclination and strata thickness on the dynamic stability is considered in the model slope with a set of bedding planes. The results show that the dynamic strength reduction method has good suitability for the stability evaluation of a bedding rock slope due to its good solution in the instability judgment and evaluation index. The dynamic stability of a slope becomes worse when the load frequency is close to the natural frequency of the slope. Due to the “elevation effect” and “bedding surface effect” in the dynamic slope response, the slope stability decreases with the increase of slope height and the reduction of strata thickness. The slope stability decreases with the increase of strata inclination and slope angle, and the strata inclination is the most sensitive parameter influencing the slope stability. When the slope angle and height increase to a certain value, the downward trend of slope stability gradually become gentle. For the model slope in this paper, when the slope angle reaches 55° and the slope height reaches 200 m, the reduction of slope stability will be no longer obvious with the increase of a slope angle and slope height