With their sweet taste, strawberries stand out as one of the world's most popular fruits. Around five million metric tons are harvested every year, and this figure continues to rise. Pepperl+Fuchs industrial sensors contribute to helping a single harvest worker pick the fruits of an entire strawberry field: They are part of the first fully automated strawberry harvester and support its navigation and control.
Strawberries are delicate in several ways. Unlike apples and bananas, there is no after-ripening with those little red fruits, meaning they can only be picked at full maturity. At this point, however, even the smallest amount of squeezing will induce a decaying process that destroys the berry before it arrives on the supermarket shelf.
For this reason, strawberry harvesting remained exclusively a manual process until very recently. Then along came AGROBOT S.L., a manufacturer of innovative agricultural robots based in the Andalusian town of Huelva.
Since southern Spain is a hub of large-scale strawberry farming, AGROBOT's engineers had the problem right in front of them, and they devised the solution to it by developing the automatic harvester AGROBOT SW 6010.
With the AGROBOT, everything, apart from the selecting and packing, is done automatically. In order to protect the berries from squeezing or falls, they are cut from their stems by two thin, razor-sharp blades. They are immediately caught in a tiny basket lined with rubber rolls, which places the fruit on a conveyor belt leading to the packaging area. Operators can directly select and pack the fruit into trays.
There is space for two farm workers on the machine, although it can be operated by just one person. Robotic arms control the interactions of blades and baskets with the berries. A camera-based vision system analyses each fruit individually, checking form and color, and then orders the precise cutting movements when a ripe berry is found.
A set of Pepperl+Fuchs devices control the robotic arms and the machine itself. Each arm is equipped with two inductive sensors to stop at end positions. Since they suffer no mechanical attrition at all, they were the ideal solution for AGROBOT's engineers.
The collision control system has to cope with dirt and dust, changing temperatures, vibration, and shock. Therefore, a robust ultrasonic sensor series UB400-12GM prevents the arm from touching the ground.
Additional ultrasonic sensors are exposed to the same external impacts while helping steer the harvesting machine automatically. Each wheel is equipped with the ultrasonic sensor which continually detects the distance between the wheel and the strawberry field row, keeping the vehicle on track and avoiding damage to the fruits.
Signals are sent to the automatic steering system from the sensors to continuously and precisely regulate the steering position of the wheels.
The steering shaft position is controlled by the inductive angular measuring system PMI360DV-F130 series. This enables perfect end-of-row maneuvers, whether the ride is bumpy or smooth.