Agriculture 4.0: a grape harvesting solution

Agriculture is undoubtedly crucial to the livelihood of humans as a race, since it is and always has been a source of food and work for our ancestors and for the current generations. Automation in agriculture started, of course, with the automation of the industrial sector, as factories began using complex machines and steam power to operate. Such use of machines allowed the increase of the speed of manufacturing and to reduce the number of people needed. In the farming world, machines began to sow, row and harvest the crops, again reducing the number of people in the sector, which combined with the advancements in chemicals and bioengineering, also saw an increase in the yields. There is however a difference that we must keep in mind when talking about farming and industry: farming is not as much as precise and predictable as industrial processes are. Two plants do not grow the same, the weather this year is different from other years and in a broad sense, the setting of growing stock and crops can be a lot more variable and volatile than an industrial one. In this work, the focus is on vines. Even more specifically, on harvesting of grapes. There are different kinds of grapes: some are more suited to be sold as food, others are suited to be used for wine. Also, there must be a point made on the particular way we grow grapes. Unlike potatoes or wheat, they do not grow in the ground, and unlike other fruits, they do not grow on trees. Grapes grow in grapevines, that are arranged in lanes, something that is specific to this fruit alone. This action can be difficult because the grapes are delicate and there are many external factors that could hinder the correct actions. During the development of the robot these factors have been considered to develop a practical idea. The aim of this work is to design, assemble and test a robotic solution for grape harvesting, by maintaining the concept of “pick one by one” that is applied during manual harvests, especially for grapes used to produce high quality wine. The design is started from a simple prototype to understand necessary motion capabilities and torques; different solutions were developed to find the best one which could satisfy the constraints. After that the materials used to realize different parts were chosen. Carbon fiber is used for the arms of the robot, aluminum for other body parts and steel for two critical shafts. The final product is a robot with 4 degrees of freedom, actuated by 4 electric motors. They are all stepper motors, albeit with different sizes and capabilities. For two of these gears were used: one motor has a nut screw to have a linear actuation and one is connected to a pulley to increase the available torque. The motors are controlled and actuated by STM32 boards. The code is written in C language, and it was edited in the STM32 Cube environment. At the first some tests were performed on example motors to understand the working principles and effects of the algorithm. The end effector was the last part to be designed. It is like a caliper in shape, and it is made with 3D printing. In the upper side there are 2 blades to cut the grape cluster, while the lowest part is used to grip it. The plier is actuated by a latching solenoid actuator that closes the two “fingers” that cut and catch the fruit.