Composite spectrum (CS) is a data-fusion technique that reduces the number of spectra to be analyzed, simplifying the analysis process for machine monitoring and fault detection. In this work, vibration signals from five components of a combine harvester (thresher, chopper, straw walkers, sieve box, and engine) are obtained by placing four accelerometers along the combine-harvester chassis in non-optimal locations. Four individual spectra (one from each accelerometer) and three CS (non-coherent, coherent and poly-coherent spectra) from 18 cases are analyzed. The different cases result from the combination of three working conditions of the components—deactivated (off), balanced (healthy), and unbalanced (faulty)—and two speeds—idle and maximum revolutions per minute (RPM). The results showed that (i) the peaks can be identified in the four individual spectra that correspond to the rotational speeds of the five components in the analysis; (ii) the three formulations of the CS retain the relevant information from the individual spectra, thereby reducing the number of spectra required for monitoring and detecting rotating unbalances within a combine harvester; and, (iii) data noise reduction is observed in coherent and poly-coherent CS with respect to the non-coherent CS and the individual spectra. This study demonstrates that the rotating unbalances of various components within agricultural machines, can be detected with a reduced number of accelerometers located in non-optimal positions, and that it is feasible to simplify the monitoring with CS. Overall, the coherent CS may be the best composite spectra formulation in order to monitor and detect rotating unbalances in agricultural machines.

中文翻译：

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复合谱在农业机械中的应用

复合频谱（CS）是一种数据融合技术，可减少要分析的频谱数量，从而简化了用于机器监视和故障检测的分析过程。在这项工作中，通过在联合收割机机架上的四个非最佳位置放置四个加速度计，可以从联合收割机的五个组件（脱粒机，切碎机，秸秆助行器，筛箱和发动机）获得振动信号。分析了来自18个案例的四个单独的光谱（每个加速度计一个）和三个CS（非相干，相干和多相干光谱）。不同的情况是由组件的三种工作状态（停用（关闭），平衡（健康）和不平衡（故障））以及两种速度（空转和最大每分钟转数（RPM））共同导致的。结果表明：（i）可以在与分析中五种组分的旋转速度相对应的四个单独的光谱中识别出峰；（ii）CS的三种配方保留了来自各个光谱的相关信息，从而减少了监视和检测联合收割机内旋转不平衡所需的光谱数量；（iii）在相干和多相干CS中，相对于非相干CS和单个频谱，数据噪声降低了。这项研究表明，可以通过减少位于非最佳位置的加速计来检测农业机械中各个组件的旋转不平衡，并且简化CS监控是可行的。总体，