Comparison of a Lightweight Experimental Shaker and an Orchard Tractor Mounted Trunk Shaker for Fresh Market Citrus Harvesting

A designed lightweight experimental shaker successfully used to collect ornamental oranges has been tested to harvest fresh market citrus. The aim of this study was to evaluate the removal efficiency and operational times of this experimental device compared to an orchard trunk shaker. Three different collecting systems were studied. ‘Caracara’ citrus trees were tested. Removal efficiency, vibration parameters, fruit and tree damages, and fruit quality were measured. A high-speed camera was used to record operational times and determine cumulative removal percentage over vibration time. The canvases on the ground reduced the severe fruit damages but were not useful to protect against light damages. The experimental shaker produced a higher percentage of slightly damaged oranges. No significant differences in removal efficiency were found between the two harvesting systems. However, removal efficiency using the experimental device could be reduced by 40 percent and working time increase by more than 50 percent when access to the main branches was difficult. In agreement with previous results, the curve representing the branch cumulative removal percentage in time followed a sigmoidal pattern. A model was built showing that during the first 5 s more than 50 percent of the fruits were detached.

Pre-employment costs associated with H-2A agricultural workers and the effects of the ‘60-minute rule’

Agricultural employers increasingly are turning to the foreign guest worker program, known as H-2A, as a means to secure a legal workforce. This paper outlines the procedural aspects and costs of recruiting and hiring H-2A workers. Cost data is from a 2014 survey of citrus harvesters and defines pre-employment costs as filing fees, advertising, surety bonds, travel, and housing. The pre-employment costs associated with guest workers are estimated to be nearly $ 2,000 per worker. The survey was motivated by the ‘60-minute rule’ imposed by the U.S. Department of Labor prior to the 2012-13 citrus harvesting season. Cost data were collected across two crop season, 2012-13 and 2013-14, to analyze the cost implications of the rule. We found that the 60-minute rule significantly increased filing fees. These fees, however, represent a very small share of total costs and overall pre-employment costs associated with the H-2A program did not significantly change.

Task Assignment and Trajectory Planning Algorithm for a Class of Cooperative Agricultural Robots

Agricultural field operations, such as harvesting for fruits and scouting for disease, are labor intensive and time consuming. With the recent push toward autonomous farming, a method to rapidly generate trajectories for a group of cooperative agricultural robots becomes necessary. The challenging aspect of solving this problem is to satisfy realistic constraints such as changing environments, actuation limitations, nonlinear heterogeneous dynamics, conflict resolution, and formation reconfigurations. In this paper, a hierarchical decision making and trajectory planning method is studied for a group of agricultural robots cooperatively conducting certain farming task such as citrus harvesting. Within the algorithm framework, there are two main parts (cooperative level and individual level): (1) in the cooperative level, once a discrete reconfiguration event is confirmed and replanning is triggered, all the possible formation configurations and associated robot locations for specific farming tasks will be evaluated and ranked according to the feasibility condition and the cooperative level performance index; and (2) in the individual level, a local pursuit (LP) strategy based cooperative trajectory planning algorithm is designed to generate local optimal cooperative trajectories for agricultural robots to achieve and maintain their desired operation formation in a decentralized manner. The capabilities of the proposed method are demonstrated in a citrus harvesting problem.