Development of a yield monitoring system for citrus mechanical harvesting machines

A load cell based yield monitoring system was developed for the Oxbo citrus mechanical harvesting machines. The yield monitoring system consisted of a GPS receiver, a mass flow sensor and data processing and storage units. The mass flow sensor consisted of four load cells attached to a carbon-fiber plate which sensed the impact force created by the oranges hitting the plate. A mathematical model was developed to relate the impact force to fruit mass. Laboratory tests were conducted on a test rig that replicated the flow of oranges to measure the accuracy of the system under a controlled environment. The system performed very well under laboratory conditions (R (2) = 0.99 and an average error of 3.3%). In addition, a field test was conducted in a citrus orchard in Florida to evaluate the performance of the system under field conditions. Of the 72 rows used in the field test, the first 10 rows were used to calibrate the computed weight. A correlation of R (2) = 0.97 between the actual weight and the computed weight was found from the field data with an average error of 7.81%.