Orchards are among the most species-rich biotopes in Central Europe. But many stands are acutely threatened since their management is hardly worthwhile from an economic point of view, the vast majority of orchards are not or only poorly maintained. As a result, the trees become sick or die. A basic requirement for long-lasting, healthy trees that also produce a significant yield is regular and professional pruning. A project by the University of Hohenheim in Stuttgart wants to provide support with the help of artificial intelligence. Dr David Reiser from the Institute for Agricultural Engineering is working on the development of an autonomous robot that will largely take over tree pruning independently in the future. For further information see the IDTechEx report on Mobile Robots, Autonomous Vehicles, and Drones in Logistics, Warehousing, and Delivery 2020-2040.
Orchard meadows not only shape the landscape in many regions of Germany, but are also valuable habitats with numerous functions. They also serve to protect wildlife, soil and water, act as a climate compensation and as a gene reservoir for around 3,000 types of fruit in Germany alone. With over 5,000 animal and plant species, they are among the most biodiverse biotopes in Central Europe: In addition to green woodpeckers, wrynecks and treecreepers, bats and dormice, wild bees and hornets, countless species of beetles and other insects as well as lichens and mosses find a habitat here.
But orchards, mainly in processed form, also have an economic importance: For the most important branch of production, apple juice production, the orchards in Germany deliver between 500,000 and a little over a million tons of apples, depending on the harvest year. Nevertheless, the orchards have been declining for decades. In addition to economic reasons, one of the reasons is the lack of care of the stands, which significantly shortens the life of the fruit trees.
Regular pruning keeps trees healthy and alive for a long time
Healthy, stable and long-lasting crowns can only be formed with a regular, professionally executed cut. It makes a decisive contribution to the lifespan and productivity of the trees and therefore also to the continued existence of the orchards. But it is precisely here that there are often major deficits: Around 80% of trees are not cut at all. While today various agricultural machines, such as tree shakers and harvesting machines, can be of great service to fruit growers when harvesting and picking up the fruit, the pruning of the trees, which is so important for maintaining the trees, still has to be done by hand.
Robot prototype learns to recognize tree structures
An autonomous robot, which the Hohenheim agricultural technician Dr Reiser developed together with the PhD student Jonas Straub and the research assistant Jonas Boysen in the field of process engineering in plant production, may help.
"With the help of the robot, we want to help ensure that the trees stay healthy and alive for as long as possible," says Dr Reiser. The development work was made possible, among other things, by a grant of 113,000 euros from the elite program for postdocs of the Baden-Württemberg Foundation.
The three scientists have mounted an additional robotic arm on an existing mobile prototype, as is also used in industrial production lines. This articulated arm robot can move freely in all directions so that any point within its range can be controlled.
The arm is also equipped with special sensors that help navigate and recognize the trees and their structures: "While the robot drives around the tree, we record its three-dimensional structure using a so-called LiDAR scanner. Similar to radar, a laser scans the environment and measures the distance to the objects. From many individual distance measurements, a point cloud is then created in the computer that depicts the three-dimensional structure of the tree " explains Dr.Reiser.
With the help of the articulated arm, the pole pruner, a small chainsaw mounted on a telescopic rod, is moved into the correct cutting position. "We are currently working on teaching the computer where the robot should place the saw," says Dr. Reiser. "Tree pruning is a science in itself, you could almost speak of philosophy."
Depending on the type of tree and the desired destination, there are very different ways of cutting. Sometimes, for example, a continuous main trunk should be left where the branches then have to be shortened. In other cases, the main stem has to be shortened to get a light crown with many branches. The user should later be able to choose between different options.
The robot still has to be controlled manually for the individual trees and interfaces. The long-term goal, however, is to let the robot work completely autonomously on an orchard and to cut branches up to a height of seven meters.
"A particular challenge lies in the high variability of the orchards," explains Dr. Reiser. "In order to be able to use autonomously working robots there, a lot of innovative development work is required."
Source and top image: University of Hohenheim