Dynamic reliability of gears in a wind turbine gearbox under the conditions of variable wind speed and small samples

Proceedings of the Institution of Mechanical Engineers, Part C:

Wei-min

Qin

et al. 2020

As one of the most influential factors leading to gear vibrations, transmission errors of the engaging gears must be controlled to achieve a desirable dynamic performance for a power transmission system. It is well known that tooth modification is an effective way to reduce the fluctuations of the transmission error of a gear pair. The challenge is determining how to establish a quantitative relationship between the tooth modification parameters and the transmission error fluctuations of a gear pair. The present study aims to reveal the sensitivity of the tooth modification parameters on the transmission error fluctuations of a helical planetary gear train in a wind turbine gearbox. For this purpose, a sophisticated parametric three-dimensional contact model that included the micro-geometries of the tooth modification is developed in the ROMAX® environment. Based on this model, a loaded tooth contact analysis is carried out to compute the meshing characteristics, such as the contact pressure and transmission error of each gear pair in the planetary gear train. With the obtained meshing characteristics, the tooth modification amounts of the engaging gears were determined using empirical formulas. These modification amounts are designated as the mean values of the samples generated by the central composite method. After repeating the loaded tooth contact analysis process for each generated sample, a quadratic polynomial function is derived using the response surface method to describe the quantitative relationship between the tooth modification parameters and the dynamic transmission error fluctuations. A large number of random samples are generated using a Monte Carlo method, and the corresponding dynamic transmission error fluctuations are determined with the aforementioned quadratic polynomial function. Based on these samples, a reliability sensitivity analysis is carried out to demonstrate the effects of the tooth modification parameters on the dynamic transmission error fluctuations of the helical planetary gear train.

Section: Introductionmentioning

confidence: 99%

Reliability sensitivity analysis of tooth modification on dynamic transmission error of helical planetary gears

Proceedings of the Institution of Mechanical Engineers, Part C:

Wei-min

Qin

et al. 2020

“…Therefore, it is very important to design a wind gearbox reasonably. And thus many researchers have investigated the wind turbine gearbox transmission system for optimum design of gearbox [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Research on the Optimal Design and Gear Modification of Gearbox of a Wind Turbine Based on the Virtual Prototype

Yang

et al. 2014

AMR

This article describes a new mixed transmission system about the wind power gearbox. It is composed of one NGW planetary gear stage and two parallel gear stages. The modeling and optimization analysis of gearbox have been performed using Romax designer software. The load case of gear, gear modification, transmission error and Fast Fourier Transform Harmonics of wind gearbox have been carried out to investigate various performances of gearbox system. Results of the investigation show the maximum load per unit length of gear reduces about 7.2%, Transmission Error of gear reduces 74.3% and Fast Fourier Transform Harmonics decreases 77.4% after gear modification. This kind of design method has a remarkable effect on smooth running. And it provides a new research method for gear box of wind turbine.

“…Existing strength degradation models include deterministic and stochastic strength degradation models (Zhang et al, 2018a(Zhang et al, , 2018b, power function degradation model (Sun et al, 2012), exponential degradation model (Lv et al, 2009) and gamma process degradation model (Li et al, 2015a(Li et al, , 2015b. Degradation parameters in these models are generally determined by empirical parameters, which could affect the accuracy of prediction; therefore, we decide to estimate the degradation parameter by life test.…”

mentioning

confidence: 99%

Time-dependent reliability analysis of harmonic drive based on transient FEA and accelerated life test

Jiang

et al. 2020

Purpose The purpose of this paper is to analyze the time-dependent reliability of harmonic drive. Design/methodology/approach The transient finite element analysis (FEA) of harmonic drive is established to calculate the stress under different loads. Combined with the residual strength model and random variables, the time-dependent reliability model of harmonic drive is deduced by the stochastic perturbation method and Edgeworth series. Based on accelerated life tests, the degradation parameters are estimated by maximizing likelihood function. Under variable load, the key stress from transient FEA is transformed into probability density function by kernel density estimation, and the residual strength model is modified by adding adjustment factors to deal with strength degradation under different loads. Findings The critical position of stress concentration from transient FEA is consistent with the fatigue fracture position at the accelerated life test sample. Compared with the time-dependent reliability method with equivalent circular-shell static stress or empirical degradation parameters, the proposed method has the smallest prediction error of failure life. Under variable load, the state function should be expanded to second-order series for avoiding error items relevant to variance. The failure life expectation under random variable load is smaller than that under constant load. Originality/value The time-dependent reliability method of harmonic drive is firstly proposed under constant and variable load. The transient FEA of harmonic drive is established to calculate the stress for strength analysis. The accelerated life test of harmonic drive is conducted for degradation parameters estimation. The adjustment factor is added to the residual strength model for strength degradation under different loads.