Error Mesh Research Articles

Floating Shaft Load Sharing Method for Face Gear Split Torque Transmission System

In this study, the equivalent gear meshing error principle was used to analysis face gear split torque dynamics modeling, the mathematical model includes stiffness of shaft supporting, position of gears, backlashes, time-varying stiffness, damping, manufacturing error, assembly error. The result shows the floating shaft can achieved load sharing, the support stiffness is an important factor, decreasing the input shaft support stiffness, load sharing performance becomes better and vibration decreases by increasing the displacement of shaft. To study effect of errors, every errors change separately while others’ ideal. Every errors affect load sharing in different way, gear 4 manufacturing error and shaft 2 assembly error affect load sharing most, load sharing cannot achieve by decreasing one error.

Analysis of Split Torque Transmission System Load Sharing

A calculative model for parallel shaft split torque transmission system is presented, the model includes stiffness of shaft supporting, time-varying stiffness, damping, gear eccentric error errors, bearing eccentric errors, gear tooth thickness error, assembly error. Dynamic analytic model is built using the theory of equivalent mesh error and Newton method. The model was solved by variable step size forth/fifth-order Runge-Kutta method. The result shown all error affect load sharing in different way, one error deduced sharply can not improve load sharing obviously.

The Gap Nonlinear Characteristics of Gear Transmission System under External Excitation

For the study of nonlinear dynamic characteristics of a pair of gears in an external torque under gear meshing error excitation, we will establish two degrees of freedom nonlinear torsional vibration model. The use of Matlab / Simulink for numerical simulation solves the nonlinear dynamic model of the gear gap. Study the dynamic characteristics of the system in a certain domain of parameters on external incentive conditions, as well as external motivation of gear transmission system dynamic characteristics influence. The results have important practical value for future engineering practice on gear transmission system's dynamic design, and have important theoretical significance for complex gear transmission system dynamics study.

Dihedral Angle Mesh Error: a fast perception correlated distortion measure for fixed connectivity triangle meshes

AbstractIn computer graphics, triangle meshes are ubiquitous as a representation of surface models. Processing of this kind of data, such as compression or watermarking, often involves an unwanted distortion of the surface geometry. Advanced processing algorithms are continuously being proposed, aiming at improving performance (compression ratio, watermark robustness and capacity), while minimizing the introduced distortion.In most cases, the final resulting mesh is intended to be viewed by a human observer, and it is therefore necessary to minimise the amount of distortion perceived by the human visual system. However, only recently there have been studies published on subjective experiments in this field, showing that previously used objective error measures exhibit rather poor correlation with the results of subjective experiments.In this paper, we present results of our own large subjective testing aimed at human perception of triangle mesh distortion. We provide an independent confirmation of the previous result by Lavoué et al. that most current metrics perform poorly, with the exception of the MSDM/MSDM2 metrics. We propose a novel metric based on measuring the distortion of dihedral angles, which provides even higher correlation with the results of our experiments and experiments performed by other researchers. Our metric is about two orders of magnitude faster than MSDM/MSDM2, which makes it much more suitable for usage in iterative optimisation algorithms.

Analysis of Nonlinear Dynamic Accuracy on RV Transmission System <sup></sup>

RV (Rotate Vector) transmission is a new precision transmission system. In order to improve its accuracy, we study the RV transmission system. It is researched in comprehensive factors including displacement errors, elastic deformation (static transmission error, design transmission error), gear meshing errors, backlash of gear, time-varying mesh stiffness, mesh damping, bearing stiffness, torsional stiffness of input shaft, etc. The mathematical and mechanical model of dynamic transmission accuracy is established by the concentrated mass method and the dynamic substructure method. Then, the meshing force of each part is analyzed in RV reducer. The motion differential equation of RV drive system is obtained, which lays the foundation for the calculation and analysis of the transmission error.

Dynamic Characteristics of Gear Transmission System for Wind Turbine Gearbox

A study is made on gear transmission system of 1.5MW Wind Turbine Gearbox. Using lumped parameter method, the dynamics model involving 6 degrees of freedom for every helical gear is established with taking the time-varying mesh stiffness and error into account. The dynamics characteristic of transmission under the effect of both external and internal excitation is calculated. The results show that under the rated speed, the transmission system is quasi-periodic, and the vibration directions of gears with large amplitude are obtained, which is consistent with testing results. This study can be referred to in engineering applications.

Asymptotic Domain Decomposition and a Posteriori Estimates for a Semi Linear Problem

Keywords: Method of asymptotic partial domain decomposition; a posteriori error estimates; Indicator of the error; semi linear elliptic equations. 2010 Mathematics Subject Classification: 35F40; 65 1 Introduction The method of asymptotic partial decomposition of a domain (MAPDD) originates with the works of G.Panasenko Panasenko (2005). The idea is to replace an original 3D or 2D problem by an hybrid one 3D − 1D; or 2D − 1D where the dimension of the problem decreases in part of the domain. The location of the junction between the heterogenous problems is asymptotically estimated in the works of G.Panasenko mainly for linear problems. Nevertheless for numerical simulations it is essential to detect with accuracy the location of the junction. Let us also mention the interest of locating with accuracy the position of the junction in blood flows simulations when different nonlinear mathematical models are used Quarteroni and Veneziani (2003), or in fluid/solid problems for which subproblems *Corresponding author: Tel:+91-9741148002, E-mail: jerome.pousin@insa-lyon.fr Research Article Coupling heterogeneous mathematical models is today commonly used, and effective solution methods for the resulting hybrid problem have recently become available for several systems. Even if in certain circumstances, asymptotic evaluations of the location of the interfaces are available, no strategy are proposed for locating the interfaces in numerical simulations. In this article, a semi- linear elliptic problem is considered. By reformulating the problem in a mixed formulation context and by using an a posteriori error estimate, we propose an indicator of the error due to a wrong position of the junction. Minimizing this indicator allows us to determine accurately the location of the junction. By comparing this indicator with a mesh error indicator, this allows to decide if it is better to refine the mesh or to move the interface. Some numerical results are presented showing the efficiency of the proposed indicator.

Algorithms for mesh repairing to represent automobile parts

In representing automobile parts with mesh in the field of reverse engineering or finite element generation, the mesh reconstruction and data exchanging between different CAD/CAM systems often introduce many invisible topological and geometrical errors into mesh. These artifacts can cause serious problems in subsequent operations such as finite element analysis, reverse engineering, animation, and simulation. In this study we propose a practical method for repairing topological and geometrical errors on mesh. First, coincident vertices during mesh input are removed, followed by the identification of non-manifold vertices and edges. The non-manifold vertices are modified, and the facets having non-manifold edges are removed. Finally, faces that have the wrong orientations in the mesh are re-oriented. Experiments show that our methods can eliminate most common mesh errors quickly and effectively. The refined mesh can be properly used in subsequent operations.

Study on the Dynamics Performance of the Drive Train of Flying Shear Machine

Flying shear machine is widely used in continuous rolling mill production line, and its performance is largely depended on the transmission system. Here a model is established with multiple backlashes, time-varying mesh stiffness and error excitation to investigate the dynamics performance of the transmission system during the process. Also, effects of parameters are discussed. It’s believed that it will be helpful for the design of the flying shear machine

The Research on Nonlinear Vibration Characteristic of Ravingneaux Compound Planetary Gear Sets

The nonlinear dynamic model of Ravingneaux compound planetary gear sets has been built. The model includes time-varying mesh stiffness of gears, backlash as well as comprehensive mesh errors nonlinearities. By introducing relative displacements of components as the new generalized coordinates, uniform nonlinear differential equations of compound planetary gear sets are built. Then the nondimensional dynamic differential equations are derived. The nonlinear differential equations have been solved utilizing ariable step size Gill method. By changing system nondimensional excitation frequency, monocycle anharmonic response, multiply periodic subharmonic response, quasi-periodic response and chaotic response are obtained. By means of time histories, phase-plane diagram, Poincare maps and power spectrum, various responses are compared and analyzed in detail.

Dynamic Analysis of Combined Gear Drive

Combined gear drive is a common transmission form for high power drive systems. In order to study its behaviors of redundant drive, which improve the system reliability but lead to a problem of inter-excitation of vibrations, dynamic analysis becomes very necessary. First, considering the influences of gear meshing errors, backlashes and time-varying meshing stiffness, a nonlinear dynamic model of sixteen degrees of freedom is developed by using lumped parameter method. Then a nonlinear differential equation set is derived for calculating the steady-state forced response to the internal sinusoidal excitation. After that, time history wave of displacement responses, phase graphs, Poincaré maps and FFT (Fast Fourier Transform) spectra are analyzed. Finally, some useful conclusions are obtained.

Analysis of Load Sharing Behavior in Herringbone Gears Power Branching Transmission System

Torque-spilt transmissions are promising alternatives to the common herringbone gears for power-branching. A method was developed to analyze the load-sharing in power-branching. With the theory of equivalent mesh error, in consideration of the manufacturing and assembly errors of every gear pair, the formula of uneven load coefficient are obtained by using the engineering calculation and simulation calculation two methods, and then the load-sharing behavior of system is studied under different operating conditions in power dual-branching and three-branching transmission. The calculated results confirmed that measures must be took to improve load-sharing, and it is helpful for the design of power-branching herringbone gears transmission system.

Static Load Sharing in Power-Split Planetary Gear Trains

Based on analyzing the mechanism of load sharing of power-split planetary gear trains, equivalent mesh errors are defined and introduced in this paper to take the deformations and manufacturing and assembling errors into account. The static equilibrium equation of planetary gear trains is established. Then the load sharing coefficients of a power-split planetary gear system are calculated. The results indicate that the load sharing of power input stage is worse than that of the power output stage in the power-split planetary gear system.

Analysis of Static Load Sharing in Star Gearing

In order to analyze the sharing mechanism of marine high-speed star gearing system, a static mechanical model is presented in the paper, in which manufacturing errors, assembly errors, bearing errors and tooth thickness error are all considered. In consideration of equivalent mesh error and static balance of floating components, the load sharing coefficient of the system in different kinds of errors was obtained. And the sensitivities of the load sharing coefficient on different types of errors are analyzed. The result shows that the effects of the eccentric error of sun and tooth thickness error of star gear upon load sharing coefficient are larger than those of the other errors. The influences on load sharing coefficient of each error have cumulative effects. The research has provided a useful reference for improving the load sharing capability of marine star gearing system.

Multi-Body Dynamics Simulation of A Tracked Vehicle Power Train in Consideration of Multi-Source Excitations

This study proposed a new efficient method to investigate tracked vehicle gear transmission system dynamics applying Finite element theory and multi-body dynamics. Torsional excitation was simulated based on an engine dynamic model by considering flexibility of crankshaft, maximum fire pressure and variable inertia. Gear mesh stiffness coefficient, mesh error excitation, bearing dynamic stiffness coefficient and damping coefficient were numerically calculated. The virtual prototype model of power train system including all aforementioned excitations was constructed. Dynamic responses of transmission shaft working with multi-source excitations were analyzed. The impact of each excitation source was discussed.

Stereoscopic image generation of background terrain scenes

AbstractThe reconstruction of 3D terrain geometry from images is essential for compositing CG objects into a live‐action background or for 2D to 3D conversion of terrain scenes. We present a novel mesh refinement algorithm for the creation of stereoscopic images of terrain scenes. Previous approaches emphasise the smoothness of the resulting terrain mesh over accuracy 1. Point cloud‐based methods cannot effectively recover the entire surface, leading to visual discrepancies after monocular sequences are converted into 3D stereo. As misalignment or inaccurate 3D terrain data over corresponding 2D background images can result in visual fatigue when stereo sequences are generated, ensuring accuracy of the reconstructed geometry is very important. To achieve the necessary accuracy, our method evaluates mesh errors utilising a texture projection onto the geometry and refines the mesh using Laplacian‐based editing. Our algorithm automatically generates stereoscopic images of terrain scenes. In addition, our method simplifies identification and compositing of foreground objects on the terrain geometry. Copyright © 2011 John Wiley & Sons, Ltd.

Nonlinear Dynamic Characteristics of Compound Planetary Gear Train Sets Based on Harmonic Balance Method

A purely rotational model of Ravigneaux compound planetary gear train sets including time-varying mesh stiffness,synthetic mesh errors and gear backlashes is developed to show the nonlinear dynamic behavior of the system with the action of multi-clearances.The gap function is expressed as describing function and harmonic balance method(HBM) is used to convert the differential equations to nonlinear algebraic equations,which is solved iteratively by single rank inverse Broyden method.The steady state response of fundamental frequency is obtained.The influences of gear backlashes,time-varying mesh stiffness and synthetic mesh errors are analyzed by changing the value of the parameter.It is showed from the research that multiple value and amplitude jump discontinuities are presented on the dynamic curves,there the impact phenomenon is reflected.Meanwhile the nonlinearity degree of the system is increased by the coupling of stiffness fluctuation,mesh errors and backlashes.The HBM based on describing function can be used for more complicated model to obtain the steady state response of fundamental frequency,which provides a method for deeply researching the dynamic behavior of compound planetary gear train sets.

Research on Torsional Vibration of Gear-Shafting System Based on an Extended Lumped Parameter Model

In this paper, gear-shafting system dynamics theory has been introduced into the torsional vibration calculation of the marine propulsion shaft and the vibration equations of a marine gear-shafting system were established using the lumped parameter model by taking the gear-shafting system in marine propulsion shaft as the research object. In order to solve the problem of vibration equation, dynamic simulation has been done in MATLAB software, in which the natural frequency of the system has been obtained from the simulation curve by changing the input frequency, meanwhile, the conclusion that the gears pair comprehensive meshing error is independent of the system natural frequency has been achieved. Thus, the analysis method presented in this work is available for the torsional vibration calculation of the marine gear-shafting system.

Transient Analysis of a Spring-Loaded Pressure Safety Valve Using Computational Fluid Dynamics (CFD)

A spring-loaded pressure safety valve (PSV) is a key device used to protect pressure vessels and systems. This paper developed a three-dimensional computational fluid dynamics (CFD) model in combination with a dynamics equation to study the fluid characteristics and dynamic behavior of a spring-loaded PSV. The CFD model, which includes unsteady analysis and a moving mesh technique, was developed to predict the flow field through the valve and calculate the flow force acting on the disk versus time. To overcome the limitation that the moving mesh technique in the commercial software program ANSYS CFX (Version 11.0, ANSYS, Inc., USA) cannot handle complex configurations in most applications, some novel techniques of mesh generation and modeling were used to ensure that the valve disk can move upward and downward successfully without negative mesh error. Subsequently, several constant inlet pressure loads were applied to the developed model. Response parameters, including the displacement of the disk, mass flow through the valve, and fluid force applied on the disk, were obtained and compared with the study of the behavior of the PSV under different overpressure conditions. In addition, the modeling approach could be useful for valve designers attempting to optimize spring-loaded PSVs.

Accuracy analysis of BN-600 power density calculations

Methodological program techniques for performing neutron-physical calculations of fast-reactor cores with a description of the main codes TRIGEX, JARFR, GEFEST, MMKKENO, and ModExSys are described. The results of verification and assessment of the methodological errors on the basis of a test model of BN-600 are presented. Transport effects and mesh errors in the reaction rate distributions in the core, lateral screen, and in-reactor storage area are evaluated. An integral assessment of the computational accuracy is performed by comparing with the experimental data obtained by γ-scans of BN-600 fuel assemblies. It is shown that calculations describe the experimental data over the core with an error no worse than 5%. In the lateral screen and the in-reactor storage area, the discrepancy between the calculations and experiment does not exceed 20–30%.