Study of Vibratory Phenomena During Mechanical Grape Harvesting: Methodology of Signal Measurement And Analysis

The chapter presents a methodology for measuring vibrating stress during mechanical grape harvesting. The method involves the use of accelerometers positioned on the plants to measure the vibrating stress transmitted by the machine. The piezoelectric accelerometers (sensitivity: 0.316 pC/ m s-2; frequency range: 0.1 Hz to 16.5 kHz; measurement range: ± 50000 m s-2 ) are connected to a load amplifier and digital recorder. Each sequence of measurements provides the graph of the accelerations as a function of time. The graphs provide the values of the single accelerations, and spectrum analysis (computed with the Fast Fourier Transform) can be used to demonstrate any effects of interference and overlapping of the vibrations during the machine transit. In order to demonstrate the validity of the methodology, analyses of the data measured using five different types of grape harvesters with horizontal shaking are reported. In some cases comparisons were made in different vineyards, in other cases in the same vineyard. The positioning of the accelerometers in different points of the curtain of vegetation was analyzed to demonstrate the importance of this element on the interpretation of the data. The results show that the construction differences of the machines influence the measured functional parameters. The importance of the vineyard also emerges, especially in the propagation speed of the wave phenomenon because of the different behaviour of the structures constituted by the cordon and shoots.