Mushroom robot: picks and trims button mushrooms

The button mushroom — Agaricus bisporus — is an important agricultural commodity. Approximately 404 million kg of button mushrooms valued at $1.13 billion were consumed in the US within one year (2017–18).

Because 91% of the mushrooms consumed come from the fresh market, labour costs for harvesting mushrooms account for around 15% to 30% of the production value. Therefore, mechanical or robotic picking could help to alleviate the associated labour shortage issues and costs, so researchers looked for a solution.

Researchers at Penn State’s College of Agricultural Sciences have now developed a robotic mechanism for automated harvesting of button mushrooms. The prototype uses a pneumatic system that has been designed to be integrated with a machine vision system. It has been shown to be capable of both picking and trimming mushrooms growing in a shelf system.

Developing a device to effectively harvest mushrooms was a complex endeavour, explained the lead author of this study, Long He, assistant professor of agricultural and biological engineering. In 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. A robotic mechanism had to achieve an equivalent picking process.

The prototype, which is designed to be integrated with a machine vision system, showed that it is capable of both picking mushrooms with a pneumatic system (top photo) and trimming them (bottom photo). Image credit: Penn State

The researchers designed a robotic mushroom-picking mechanism that included a picking ‘end-effector’ based on a bending motion, 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. They fabricated a laboratory-scale prototype to validate the performance of the mechanism.

The research team used a suction cup mechanism to latch onto mushrooms and conducted bruise tests on the mushroom caps to analyse the influence of air pressure and acting time of the suction cup.

To determine forces that needed to be programmed into the robotic picker, researchers took mushroom-picking-dynamics measurements using force sensors and an inertial measurement unit. Image credit: Penn State

The test results, recently published in Transactions of the American Society of Agricultural and Biological Engineers, showed that the picking end-effector was successfully positioned to the target locations and its success rate was 90% at first pick, increasing to 94.2% after second pick.

The trimming end-effector achieved a success rate of 97% overall. The bruise tests indicated that the air pressure was the main factor affecting the bruise level, compared to the suction-cup acting time, and an optimised suction cup may help to alleviate the bruise damage, the researchers noted.

The laboratory test results indicated that the developed picking mechanism has potential to be implemented in automatic mushroom harvesting.

Top image credit: ©stock.adobe.com/au/Vantsura