拖拉机动力输出轴（power take-off, PTO）的作业载荷中无损伤或小损伤载荷占据大量比例，在耐久性试验中会导致试验时间过长，经济性变差，将这些载荷剔除可以得到加速载荷谱。以40马力拖拉机为研究对象，采用Daubechies小波对拖拉机PTO实测载荷信号分解并重构高频小波系数得高频小波分量，在总伪损伤保持基本一致的前提下，选取合适的阈值并结合包络线损伤判别方法，从原始载荷信号中提取损伤较大的载荷片段并拼接成加速载荷谱，分别得到压缩比为42.0%、49.8%、61.7%、62.4%、81.9%的加速载荷谱。基于频域、幅值域、统计参数和疲劳损伤等理论验证所编制加速载荷谱的正确性，以及与原始载荷谱的相似度。结果表明，加速载荷谱与原始载荷谱在伪损伤基本一致的前提下，频域、幅值域分布曲线保持相似，最值、均方根值、峰度系数等参数误差均在5%以内，对零部件造成的损伤效果也基本一致。证明该加速方法适用于拖拉机零部件加速载荷谱编制，并为农机领域加速载荷谱的编制提供参考依据。
Abstract
In operating load of tractor power take-off (PTO), no damage or small damage load occupies a large proportion to cause long test time and poor economy in durability tests. Eliminating these loads can obtain the acceleration load spectrum. Here, taking a 40 HP tractor as the study object, Daubechies wavelet was used to decompose the measured load signal of the tractor PTO, reconstruct high frequency wavelet coefficients and get high frequency wavelet components. On the premise of the total pseudo damage remaining basically the same, the appropriate threshold was selected and combined with the envelope damage identification method, load segments with larger damage were extracted from the original load signal and spliced into the acceleration load spectrum. Acceleration load spectra with compression ratios of 42.0%, 49.8%, 61.7%, 62.4% and 81.9% were obtained, respectively. Based on theories of frequency domain, amplitude domain, statistical parameters and fatigue damage, the correctness of the obtained acceleration load spectrum and its similarity to the original load spectrum were verified. The results showed that frequency domain and amplitude domain distribution curves of the acceleration load spectrum and the original load spectrum are similar on the premise of the pseudo damage being basically the same; errors of its maximum value, root mean square value, kurtosis coefficient and other parameters all are less than 5%; the damage effect of components is basically the same; the proposed load acceleration editing method is suitable for making acceleration load spectrum of tractor components, and can provide a reference for making acceleration load spectrum in agricultural machinery field.
关键词
小波变换 （WT） /
拖拉机PTO /
包络线 /
载荷加速
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Key words
wavelet transform （WT） /
tractor PTO (power take-off) /
envelope /
load acceleration
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