In-situ identification of shaking frequency for adaptive vibratory fruit harvesting

摘要

The improvement of the fruit removal efficiency is important in vibratory fruit harvesting. Most relevant research has focused on the detection of dynamic parameters of the tree system by conducting experiments or simulations. The present study proposes a method of identifying multiple natural frequencies of a fruit tree insitu during vibratory harvesting. An intelligent shaker system consisting of an eccentric shaker with adjustable speed and an acceleration signal acquisition analyzer is developed. A frequency sweeping experiment using the intelligent shaker system is carried out to measure natural frequencies by searching for extreme values of the acceleration signals. Additionally, a testing experiment for measuring acceleration responses at different shaking frequencies is performed to obtain the optimal shaking frequencies. The experiments show that the natural frequencies could be obtained effectively by the frequency sweeping experiment in-situ, and the identified natural frequencies of different branches are found to be different. All results indicate that the identified natural frequencies using the proposed method can be regarded as the optimal shaking frequencies for adaptive vibratory fruit harvesting, and that it is necessary to detect the natural frequency of each large branch of a tree during vibratory fruit harvesting.