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Applied research of the multi-stage torsional vibration damper on controlling the gear rattle
Get PDFThe gear rattle noise of automobile transmission, which belongs to broadband noise, tends to attract the driver’s increasing attention. This paper performs a test on the noise, vibration and harshness (NVH) performance of power train in a passenger car. The results of the test show that the angular acceleration of the input shaft in the transmission increases with the increase of the angular acceleration of the flywheel, and excessive fluctuations of angular acceleration lead to the generation of the gear rattle in transmission. In this paper, a mathematic model of torsional vibration under the working conditions of acceleration, constant speed and deceleration has been established by taking a pair of helical gears as an example. The solving model of the mathematic model is set up by Matlab/Simulink and numerical solution has been solved. The theoretical analyses show that the ability of the traditional single-stage torsional vibration damper to attenuate fluctuations of angular acceleration is limited, while the multi-stage torsional vibration damper can attenuate larger fluctuations of angular acceleration, and the power train can provide good comfort and low fuel consumption. The experimental results in this paper are in accordance with above theories. Dynamic model of torsional direction of helical gears built in this paper is of great significance to the analysis of dynamic characteristics of gears. The multi-stage torsional vibration damper proposed in this paper can attenuate larger fluctuations of angular acceleration effectively, which plays an important role in controlling gear rattles, meanwhile it can enhance the riding comfort of a vehicle and reduce fuel consumption
Research on vibration and interface simulation technology of aero-engine
Get PDFExcessive vibration can cause engine fault, so the engine vibration monitoring and control is particularly important to flight safety. With the simulation platform of hardware in loop of the engine control system, the ability to handle the vibration of the engine controller can be verified. It can effectively reduce the development cost and shorten the development cycle. This paper is a result of extensive research on the vibration signal modeling and the interface simulation technology of engine, in the vibration control experiment of hardware in loop; and a universal interface simulator has been designed. The interface simulator can receive multi-channeled signal in a wide-range of values, and can also simulate different kinds of signals, simplify the signal acquisition and conditioning circuit of the electronic controller. This simulation provides a good platform for the research of engine vibration control
Vehicle steering wheel angle identification research based on dynamic program method
Get PDFIn order to improve the safety of vehicle manipulation as well as to provide a theoretical basis for the study of vehicle steering system and intelligent parking systems, a new method of vehicle steering wheel angle identification is presented – the dynamic program method. First, three freedom degrees of vehicle model is established. Then Bellman’s principle of optimality is used for minimizing the objective function. The dynamic optimization model of the load identification that the yawing angular velocity, lateral acceleration and vehicle body roll angle identified the steering wheel angle and angle velocity. The result shows that the dynamic program method for the steering wheel angle identification problem containing the measurement noise has strong adaptability, high accuracy and good anti-jamming capability
Investigation on a collapse accident of guyed portal towers caused by strong wind
Get PDFA collapse of 3 guyed portal towers in a 220 kV transmission power system were caused by short period of strong wind. In order to unmask accident, various methods are used, such as scene investigation, material test and FE method. The reasons caused the collapse accident are obtained in this paper, and some improvement measures are recommended for sake of continuing maintenance
A weak solution for free vibration of multi-span beams with general elastic boundary and coupling conditions
Get PDFA weak solution of free vibration is developed for multi-span beams, which can adapt general elastic boundary and coupling conditions. Firstly, create the energy functional of the multi-span beam system based on the small deformation theory. Then, adopt the modified Fourier series method to rewrite the displacement functions. Compared with the traditional Fourier series method, the present series representations provide a solution for general elastic restrains. Lastly, combined with the Rayleigh-Ritz technique, all the series expansion coefficients can be obtained as the generalized coordinates. Numerical results demonstrate that the current weak solution has good convergence and high accuracy compared with the existing results in literature and FEM results
Generalized gap function in the dynamic interaction problems of elements of vibrational technological machines with “not holding” ties
Get PDFIssues of formation of rational modes of dynamic interaction of contacting elements of vibrating machines in problems of increase in quality of technological vibrohardening processes are considered. Mathematical models and criteria of an estimation of forms of movement with “not holding” ties are developed. For analytical research of “not holding” ties the concept of the generalized gap function is entered. The model of dynamic interaction of a solid with a vibrating surface is developed at introduction of additional external forces and elastic interactions. On the basis of a method of gap function criteria of a separation are formulated and forms of movement of a material particle in dynamic interaction with a vibrating surface are proved. The generalized approach for problems of dynamic synthesis of the vibrating technologies realized in modes continuous tossing is offered. Conditions of realization of multiple modes continuous tossing when the period of free flight of a material particle makes an integer of the periods of a basic vibrating surface are formulated. Generalization of considered models on a compound solid, interaction between which elements has “not holding” character is offered. The problem of definition of gapless conditions of movements at vibrating influence on a compound solid by a surface is posed. Conditions of formation of reaction in the oscillatory system formed by several solid elements with “not holding” ties, connected among themselves by means of elastic interaction and power factors are defined. In respect of practical appendices, the problem of development and experimental approbation of the measuring devices fixing modes of continuous tossing is posed
The effect of dry friction forces on the process of dielectric wafer grinding
Get PDFWe have investigated possible motions of the holder on top of the polishing pad during the process of dielectric plate grinding taking into account the forces of dry friction about its axis. A mathematical model of the mechanical device has been elaborated to describe the process of dielectric wafer grinding. The model is in the form of a non-autonomous nonlinear system with a variable structure. The structure of the phase space of the dynamical system was investigated, the qualitative studies of the possible motion modes were carried out. The values of the geometrical and dynamic parameters that qualitatively and quantitatively influence the modes of the holder motion were obtained. It was found that the inclusion of dry friction forces on the axis of the free holder result in a periodic motion of the mechanism with long stops. We present the calculations of the parameters for the type 3PD-320 machine
Vibration suppression of rotating nonlinear beam by nonlinear energy sink
Get PDFIn this paper, vibration suppression of a rotating nonlinear beam under the action of an external harmonic force is studied by a Nonlinear Energy Sink (NES). Dynamic model of the rotating nonlinear beam coupled with a NES is obtained by using quasi-Hamilton’s principle and Galerkin method. Then, harmonic balance method is used to acquire the analytic solution of the vibration amplitude of beam. In addition, the influences of rotating speed and NES parameters (mass, damping, nonlinear stiffness, and position of NES) are investigated in details
Research on the vibration characteristics of the commercial-vehicle cabin based on experimental design and genetic algorithm
Get PDFMost of the published researches on the vibration isolation performance of the commercial vehicle focus on the suspension system and the power-train system, and few of them focus on the cabin. Moreover, the researches on the cabin mostly focus on how to reduce the interior noise, and the interior vibration characteristics have not received adequate attention. Therefore, this paper tries to research the vibration characteristics of the commercial-vehicle cabin in order to improve ride comfort. Firstly, the vibration characteristic of the cabin was tested on the actual road. Then, the rigid-flexible coupling dynamic model of the commercial vehicle was built, and the computational results were compared with the experimental results. It was found that the results were consistent with each other, which showed that the computational model was reliable. Finally, based on the verified computation model, some parameters that influenced the vibration characteristic of the cabin were explored. As a result, the influencing tendency of each parameter to the cabin vibration under each working condition was obtained, but influencing levels of each parameter cannot be analyzed quantitatively. In order to research the contribution degree of each parameter to the vibration in cabin, DOE (Design of Experiment) method was used for the analysis to provide references for the optimal matching of a cabin suspension system. Then, the vibration in the cabin was optimized based on genetic algorithm to obtain the optimal performance. This research can provide a reference for the other researches on the reduction vibration for the cabin
Rapid early damage detection using transmissibility with distance measure analysis under unknown excitation in long-term health monitoring
Get PDFAccurate and efficient damage detection in long-term health monitoring for structures still encounters many difficulties due to the effect of environment. Furthermore, recorded big data requires efficient damage detection algorithm. In this study, an efficient and effective damage detection algorithm is proposed using transmissibility along with Mahalanobis distance and Hotelling T-square. A numerically simulated beam and an experimentally tested laboratory structure are used to validate the proposed algorithm. Results demonstrate good performance of the proposed technique in damage detection