Selection and experimental evaluation of shaking rods of canopy shaker to reduce tree damage for citrus mechanical harvesting

Abstract

Canopy shaking system is one of the research hotspots for large-scale mechanized fruits harvesting. Shaking rods considered as one of the essential components of canopy shaker are responsible for transferring mechanical energy from shaking mechanism to different regions of tree canopy. This transfer depends on the characteristics of the shaking rods that directly strike the tree canopy. In order to evaluate the effects of the shaking rods on tree damage level and fruit removal percentage, three kinds of shaking rods with different materials or shapes were selected. Based on the results of bending deformation tests, it was proven that the rigid shaking rod (R 1 ) with the material of Polyvinyl Chloride (PVC) did more resistance against producing bending deformation in comparison with the other two types of shaking rods with the material of Polyamide Nylon 12 (PA). By contrast, the position close to the free end of the flexible shaking rod was easier to be deformed by less external force. In addition, dynamic analysis and vibration performance tests indicated that the rigid shaking rod could produce stronger vibration with higher shaking frequency of 4.8 Hz and maximum acceleration of 31.4 m/s 2 . Finally, the results of field trials indicated that the flexible bow-shaped shaking rod (R 3 ) has a better widespread performance to achieve comparative higher fruit removal percentage up to 82.6% while producing lower tree damage rate of 5.36%. This study demonstrates that the materials or shapes of the shaking rod could significantly influence the fruit detachment rate and tree damage level. This study would provide an essential reference for the application of shaking rods for canopy shaker.

Design and evaluation of a two-section canopy shaker with variable frequency for mechanical harvesting of citrus

“…The motion frequency of the shaking rod was defined as an inherent frequency depending on the certain hydraulic motor speed. The shaking displacement was mainly determined by the designed structure, but it was also affected by the elastic deformation of the flexible shaking rod [36] , which was difficult to accurately measure in this study. Figure 6 Acceleration test of the shaking rod…”

“…Based on previous studies on sectionalized vibration, this canopy shaker had a top and a bottom shaking system which could be operated separately. To provide the requisite functions of frequency adjustment and positioning operation, the shaking system consisted of the following eight main components: (1) a flywheel; (2) a hydraulic motor with a displacement of 80 cm 3 [36] . The maximum depth of the shaking rod inserting in the tree canopy reached to 1.1 m when the shaking rod was moving to the extreme position.…”

“…The algorithm was developed for processing data, including resultant acceleration calculation, acceleration peak counting, data points, frequency counter, fitting and statistical data analysis expounded by Pu et al [36] . Finally, the mean values and standard deviations (SD) of the frequency and acceleration amplitude were obtained by statistical analysis.…”

“…Also, all the fruits that had not been detached on the tree were manually picked and weighed. The fruit removal percentage (FRP) was calculated by the following methodology (Equation (4)) reported by previous studies [36,38] . The tree damage rate (TDR) during the mechanical harvesting process was defined as the percentage of the collected fresh debris including the leaves, branches and limbs based on the total weight of dropped oranges and debris [36] , as given by Equation (5): where, FRP is the fruit removal percentage, %; TDR is the proportion of debris load, %; M do is the mass of the detached oranges, kg; M uo is the mass of the un-detached oranges on the tree, kg; M dd is the mass of the dropped debris, kg.…”

“…Compared to the motion frequency, the variation of the shaking frequency was most likely caused by the elastic deformation of the flexible shaking rod. The shaking rod deformation characteristics are not within the scope of this study, but its shaking response could potentially relate to the variable frequency and amplitude [36] . Due to ineffective shaking for fruits harvesting under a low shaking frequency, which has been observed by Ortiz and Torregrosa [41] , all of the subsequent field trials for harvesting efficiency and tree damage assessment were performed with the shaking frequency range from 3.3 Hz to 6.8 Hz, which has been recommended for canopy shakers [45] .…”