A robotic mechanism for mushroom picking and trimming recently was developed by researchers at Pennsylvania State University. The researchers demonstrated the robot’s effectiveness for automated harvesting of button mushrooms.
The research is important because the mushroom industry has been facing labor shortages and increasing labor costs. Mechanical picking can help alleviate such problems, said Long He, an assistant professor of agricultural and biological engineering at Penn State.
The button mushroom – Agaricus bisporus – is an important agricultural product. More than 890 million pounds of button mushrooms valued at $1.13 billion were consumed in the United States from 2017 to 2018. About 91 percent of those mushrooms were sold for the fresh market. They were hand-picked to ensure product quality, shelf life and appearance. Labor costs for mushroom harvesting account for 15 percent to 30 percent of the production value, He said.
During hand-picking a picker first locates a mature mushroom and detaches it with one hand, typically using three fingers. A knife in the picker’s other hand is then used to remove the stipe end. Sometimes the picker waits until there are two or three mushrooms in hand and cuts them one by one. Finally the mushroom is placed in a collection box. The researchers’ robotic mechanism had to achieve an equivalent picking process.
They designed a robotic mechanism, which is to be integrated with a machine-vision system. The mechanism features a picking “end-effector” based on a bending motion. The researchers also designed a “4-degree-of-freedom positioning” end-effector for moving the picking end-effector, a mushroom stipe-trimming end-effector, and an electro-pneumatic control system.
The research team used a suction-cup mechanism to latch onto mushrooms. The team conducted bruise tests on mushroom caps to analyze the influence of air pressure and acting time of the suction cup.
The picking end-effector was positioned to the target locations. Its success rate was 90 percent at first pick, increasing to 94.2 percent after the second pick.
The trimming end-effector achieved a success rate of 97 percent overall. Bruise tests indicated that air pressure was the main factor affecting bruise level compared to the suction-cup acting time. The optimized suction cup may help to alleviate bruise damage, the researchers observed.
