cows in field
NODPA Logo

Mower with a Mind of its Own: A Partnership between University of Minnesota Researchers and a Minnesota Company aims to Make Farming More Sustainable

By Gayla Marty, Minneapolis-based freelance writer and Joel Haskard, University of Minnesota

About 250 crossbred Holsteins graze on grasses and cover crops at the West Central Research and Outreach Center (WCROC) near Morris, Minnesota. The herd is part of the center’s ongoing research on dairy production. But the cows don’t eat everything, and the weeds left behind will spread unless cut. That’s when the cowbot goes to work. The little 25-horsepower tractor-like machine works something like a combination of a robotic vacuum cleaner and a lawn mower. Weighing in at nearly a ton, it has four-wheel drive and can “think” and navigate on its own. When power runs low, it returns to its charging station, a trailer with solar panels.

The mission of the cowbot is to explore a new way to reduce agriculture’s carbon footprint—a priority at donor-supported WCROC, which is committed to using renewable energy to reduce fossil-fuel consumption in agriculture. In addition, the cowbot aims to lessen the use of herbicides and save farmers’ time.

The cowbot is the result of collaboration between WCROC, part of the University of Minnesota (UM) College of Food, Agricultural, and Natural Resource Sciences; the College of Science and Engineering; and Bloomington-based Toro Co.

Toro was interested in converting its diesel-powered GM3280 mower to electric for testing as a quiet vehicle on parks and golf courses. When WCROC contacted the company about an earlier project, the mower project found a home. Toro contributed the original mower plus more than $124,000 for parts and engineering design, software, fabrication, and assembly labor to create the prototype. The company continues to provide engineering support through testing.

“Our overall mission is to take things that are available and see if they will work in new ways.” — Eric Buchanan

“Toro’s mower was designed for more formal turf, not pastures, but it works great here,” says WCROC lead researcher Eric Buchanan, who received a grant from Minnesota’s Environment and Natural Resources Trust Fund to study the use of autonomous vehicles for weed control.

The three-year project began in 2018 with a focus on pasture mowing. This summer, it branched into early weeding of row crops, specifically corn and soybeans. The final year will be devoted to fine-tuning hardware and software, and developing and testing safety protocols.

“Our goal is not to develop a new commercial vehicle. Our overall mission is to take things that are available and see if they will work in new ways,” Buchanan says.

Field tests resumed this summer. With different mowing patterns developed in 2019, the U of M robotics team is flying a drone to spot weeds, collecting images for a database that allows the cowbot to recognize them. Weed identification will become more important as testing moves into weeding row crops.

“The terrain is very bumpy so we’re mowing very slowly, less than two miles an hour,” says Jack Gust, a chief engineer in research and development for Toro. “But if you’re a robot, time is not that big of a deal.”

Gayla Marty lives in Minneapolis and works as a writer and editor with an interest in culture, agriculture, and natural history. She can be reached at gaylamarty@gmail.com.

------------------------------------------------------------------------------------------------------------------------------------------------------------

COWBOT! Coming to a field near you?

Q & A: Renewable energy scientist Eric Buchanan tells us a bit more about the Cowbot

By Joel Haskard, photos courtesy of Eric Buchanan

Leave it to the amazing team at the West Central Outreach & Research Center outside of Morris MN to be experimenting with a solar-powered Cowbot.

  • What is Cowbot and what does it do?

The Cowbot is an autonomous mower for weed control in cow pastures. It is a collaboration with researchers in the Computer Science and Engineering department (CSE) and The Toro Company. The Cowbot can come into a pasture after cows have grazed and cut down the weeds the cows didn't eat without cutting the grass. This is especially important in organic pastures where herbicides cannot be used. It uses a flail mower instead of a standard deck mower to better cut large weeds like thistles that are typical in pastures.

The Cowbot is driven around the area to be mowed while an operator logs the GPS coordinates. The onboard controller then calculates the most efficient path to mow that area and returns to a charging trailer when finished.

The Cowbot can come into a pasture after cows have grazed and cut down the weeds the cows didn't eat without cutting the grass. This is especially important in organic pastures where herbicides cannot be used.

Eric Buchanan, Renewable Energy Scientist

  • How is Cowbot powered?

The Cowbot started life as a diesel powered Toro fairway mower, but was converted to run with an electric motor and to be "drive by wire" which means it can be operated electronically including steering, throttle, and engaging the mower. The battery pack can hold 29 kWh of energy and can be recharged in the pasture with a custom built solar charging trailer. The Cowbot can mow for up to 4 hours before recharging.

  • Tell us about the trailer? Can you buy these somewhere or do you have to build them yourself?

I have not seen a commercial charging trailer, but I have seen several different versions of custom built trailers. We added 10 solar panels (just over 3 kW) to the roof of an enclosed 17 foot trailer large enough to haul the Cowbot. There are three levels of panels. The top level is fixed, but the bottom two levels slide out on heavy duty drawer slides to collect sunlight. Inside the trailer a charge controller manages the charging of a 48 volt battery pack. The batteries are deep-cycle, solar lead-acid batteries. DC power from the batteries is turned into AC power by a power inverter. The AC power then feeds a few outlets and a level 2 electric car charger which is used to charge the Cowbot, but can also charge electric cars.

So, for now, you will still have to build a charging trailer yourself. The Cowbot itself is still in the research phase so you will get strange looks if you ask your Toro dealer for one.

  • Finally... does the Cowbot moo?

The Cowbot has not yet learned to moo, but it has learned to moow!

Eric Buchanan, Scientist, Renewable Energy, can be reached at buch0123@morris.umn.edu, 320-589-1711, ext. 2111, WCROC 46352 State Hwy 329
Morris, MN 56267