A Study of Operator Performance for a Mechanical Sweet Cherry Harvester: Comparison between Manual and Remote-Controlled Operation.

Abstract

An experimental mechanical sweet cherry harvester was upgraded by changing its rapid impact mechanism to a continuous impact mechanism, in which an end effector (impactor) is positioned on fruit-loaded branches to transfer vibrational energy for fruit removal, and by adding remote control capability. Before the upgrade, the operator was seated at the rear of the harvester to manually control its operation. Adding remote control capability allowed operator mobility while operating the machine. This mobility was aimed at improving operator performance in harvesting cherries. In this study, the performances of the manual and remote operator were compared in terms of the field of view for perceiving target branches, the accuracy of hitting a target branch, and the ease of maneuvering between tree rows. Several sets of photographs totaling 140 individual photos were taken to assess how easy perceiving target branches was in light and dense foliage from the viewpoint of a manual operator and from multiple viewpoints of a remote operator. The percentages of successful hits on the target branch on the first trial (measure of accuracy in positioning the impactor) and the time taken for each successful hit for the manual and remote operator were recorded. The time to travel approximately 126 m long tree rows was also recorded for the manual and remote operators. On average, the remote operator (rank = 6.5) had better perception of the target branch than the manual operator (rank = 3.7) and was more accurate in positioning the impactor on a target branch (93.3% success rate) than the manual operator (84.4% success rate). Similarly, the remote operator spent 19.9 s of positioning time per branch, which was significantly less than the 23.6 s spent by the manual operator. However, the manual operator had better focus and was numerically faster (1.4 km h(-1)) than the remote operator (1.1 km h(-1)), even though the difference was not statistically significant. Overall, the results suggest that remote operation of the harvester may have a potential advantage over manual operation for achieving higher harvesting rates of sweet cherries.