Energy Consumption of Tree Shakers as a Function of Frequency

摘要

In the last decade considerable progress was achieved in the theory of tree shakers used for fruit harvesting. New calculation methods were developed including the vibrating soil mass which enabled the calculation of effective soil masses on a strictly physical basis. However, these earlier investigations did not treat with the effect of stroke frequency. In these investigations, first of all, the friction behavior of the soil mass is discussed as a function of stroke frequency. It turned out that the decrease and shifting of the soil deformation waves as a function of distance measured from the tree trunk are the main sources of an intensive friction between the neighbouring soil layers. As a consequence, the logarithmic decrement (and not the damping coefficient) of the soil will be more or less constant as a function of stroke frequency, at least in the investigated frequency range. At lower attachment heights the soil friction losses dominate independently on stroke frequency. The virtual spring constant of the soil body is also frequency dependent. Due to the presence of combined frictional and viscous losses, the energy method seems to be the best one to analyze the effect of stroke frequency on the various operational parameters.