Robotic Blossom Thinning System for Tree Fruit Crops

Tree fruit production industry around the world heavily relies on semi-skilled seasonal workforce for critical field operations such as training, pruning, blossom and fruitlet thinning, and harvesting. Blossom thinning is an essential crop-load management technique that relies heavily on laborious and labor-intensive manual operation to achieve the desired thinning result. While large-scale thinning approaches such as chemical and mechanical thinning are available, chemical thinning results can be unpredictable, and mechanical thinning may damage a significant part of the tree canopy while also offering no-to-limited selectivity. Therefore, developing an efficient system that can perform precise blossom thinning in the target canopy regions with high accuracy, effectiveness, and robustness is crucial.This study focused on the design, development, and field evaluation of a robotic blossom thinning system that employed a machine vision system, and a mechatronic system consisting of a robotic manipulator and end-effector for targeted, selective blossom thinning in tree fruit crops. Robust machine vision systems were investigated for the identification, segmentation, density estimation, localization, and counting of apple flowers. Furthermore, a miniature, electrically-actuated end-effector was designed, fabricated, and tested for blossom thinning in space-constrained locations in tree canopies. All these components were integrated to develop a robotic thinning system and evaluated in a commercial orchard. Two thinning methods, boundary and center thinning, were investigated to assess the integrated system performance in selectively thinning flower clusters in target canopy regions. Boundary thinning was used to thin flowers along the flower cluster boundary, whereas center thinning was used to thin flowers by actuating the thinning end-effector at the center of the target cluster. The field evaluation results demonstrated that the integrated system could selectively thin blossoms from targeted clusters based on the chosen thinning strategy. The boundary thinning approach achieved a 67.2% thinning with a cycle time of 9.0 seconds, whereas the center thinning approach thinned 59.4% of flowers with a cycle time of 7.2 seconds per cluster. When implemented at a wider scale with additional improvements, the proposed system could address the problems associated with current hand, chemical, and mechanical blossom thinning approaches. Furthermore, the proposed system could aid in the commercial viability and practical adoption of the robotic systems intended for operation in tree fruit crops

The Use of Agricultural Robots in Orchard Management

Book chapter that summarizes recent research on agricultural robotics in orchard management, including Robotic pruning, Robotic thinning, Robotic spraying, Robotic harvesting, Robotic fruit transportation, and future trends.Comment: 22 page

Design, Integration, and Field Evaluation of a Robotic Blossom Thinning System for Tree Fruit Crops

The US apple industry relies heavily on semi-skilled manual labor force for essential field operations such as training, pruning, blossom and green fruit thinning, and harvesting. Blossom thinning is one of the crucial crop load management practices to achieve desired crop load, fruit quality, and return bloom. While several techniques such as chemical, and mechanical thinning are available for large-scale blossom thinning such approaches often yield unpredictable thinning results and may cause damage the canopy, spurs, and leaf tissue. Hence, growers still depend on laborious, labor intensive and expensive manual hand blossom thinning for desired thinning outcomes. This research presents a robotic solution for blossom thinning in apple orchards using a computer vision system with artificial intelligence, a six degrees of freedom robotic manipulator, and an electrically actuated miniature end-effector for robotic blossom thinning. The integrated robotic system was evaluated in a commercial apple orchard which showed promising results for targeted and selective blossom thinning. Two thinning approaches, center and boundary thinning, were investigated to evaluate the system ability to remove varying proportion of flowers from apple flower clusters. During boundary thinning the end effector was actuated around the cluster boundary while center thinning involved end-effector actuation only at the cluster centroid for a fixed duration of 2 seconds. The boundary thinning approach thinned 67.2% of flowers from the targeted clusters with a cycle time of 9.0 seconds per cluster, whereas center thinning approach thinned 59.4% of flowers with a cycle time of 7.2 seconds per cluster. When commercially adopted, the proposed system could help address problems faced by apple growers with current hand, chemical, and mechanical blossom thinning approaches

OptiThin – Implementation of Precision Horticulture by Tree-Specific Mechanical Thinning

Apples show biennial fluctuations in yields (alternate bearing). The alternate bearing cycle can be broken by reducing excessive flowers using either chemical or mechanical means. Currently, automatic thinning systems are treating the trees uniformly despite the fact that neighbouring trees can have a very different numbers of flowers resulting in different thinning requirements. In order to solve this problem the joint project OptiThin has been started. The aim of OptiThin was to develop a system that adapts thinning intensity individually to each tree by reducing the flowers efficiently and eco-friendly. In the result, OptiThin comprises a set of new technologies including: a) a stereo camera with software for real-time determination of flower density per tree; b) a shock absorbing camera platform; c) a mobile geographic information system; d) a decision support tool to calculated optimum thinning intensity based on current flower density and ancillary data (e.g. yield, soil); e) a mechanical thinning unit which is controlled in real-time. It was shown that adaptive management of excessive flowers could improve yield of marketable fruits and that environmental friendly mechanical thinning – without chemicals – is feasible