Just keep rolling a lawn ION's autonomous mowers: you might not know it from your own backyard performance, but mowing a lawn accurately and precisely constitutes a difficult systems problem, requiring centimeter-level accuracy and precision control for straight lines and smooth turns. Three student teams answered the Institute of Navigation's call to produce a smarter-than-the-average lawnmower

GPS World, Sept, 2004 by Mikel Miller, John Raquet, Jade Morton, Frank Van Graas, Boris Pervan, Laura O'Rear

As industry and society continue to make GPS navigation systems part of daily life, some frontiers remain unexplored. Take lawn mowing, for example. Who has not, while sweating behind a lumbering mower on a hot day, wished that a robot would do the job, while we sat in the shade sipping lemonade? The Institute of Navigation's (ION) Dayton Section, located in southern Ohio--well known for large lawns and hot, humid summer days--did something about this by hosting the First Annual Autonomous Lawnmower Competition. Sponsored by ION's Satellite Division, the event sought to inspire college students to pursue navigation-related research projects and a career in this field.

The competition took place June 4-5, 2004, at Rotary Park in Beavercreek, Ohio, prior to ION's 60th Annual Meeting in Dayton. The top three teams received cash awards for mowing the most lawn in the shortest time. Teams also submitted detailed reports on mower and navigation system designs, prototype cost, and projected production cost. Judges evaluated mower production costs for reasonableness, and added penalty seconds to the total time score for high-cost designs.

The teams displayed their labor-saving devices during the Annual Meeting and made 20-minute presentations, and ION publications and announcements provided international recognition. Organizers plan to feature all three mowers at ION GNSS 2004 in Long Beach, California, in September.

The Illinois Institute of Technology (IIT), Miami University--Ohio, and Ohio University participated in the inaugural competition. Student teams worked closely with faculty advisors to design and build "smart" lawnmowers that could self-navigate and cut rectangular areas of approximately 150 square meters.

The teams received world coordinates for their respective fields' corners. The lawnmowers were to mow assigned areas without going outside a three-meter safety zone. The team that cut the most grass in the shortest time, after taking into account time penalties, was crowned the winner. Any time spent outside the mowing field but within the safety zone was converted to a time penalty.

Each team had a unique design (see following sections), and all mowers cut some portion of the playing field. Ohio University's mower was the fastest and cut approximately 13 square meters of grass in less than a minute before the mower stopped near the center of the field. After observing the mower in this position for more than a minute, the Ohio University team remotely stopped its mower and informed the judges that the team's final attempt was over.

Miami University's mower actually mowed more grass than Ohio University--approximately 18 square meters--before it left the designated safety buffer area and had to be remotely stopped. Since approximately 5 square meters of the cut grass lay outside the designated mowing area, time penalties were assessed, negatively affecting its final score.

The entrant from Illinois was attributed a symbolic 0.5-square meter for passing the qualifying tests and showing the robust functioning of its system; last-minute difficulties, explained later, prevented the team from demonstrating full vehicle performance.

Based on these scores, Ohio University took first place and a check for $2,500, Miami University received $1,500 for its efforts, and Illinois Institute of Technology won $1,000.

In addition to the mowing competition, each team's technical reports and production plans were judged for technical content, clarity, and format. BearingPoint, a business consulting and systems integration firms and event sponsor, awarded Miami University's team a $1,500 check for first place in the Best Report portion of the competition.

With increasing interest from the navigation community, we expect this event to grow rapidly. The next competition will take place in June 2005, prior to ION's 61st Annual Meeting in Cambridge, Massachusetts, over a slightly more difficult course, with obstacles added to the playing field. Each subsequent year will bring further challenges to the competition with the goal of developing mowers that can navigate any lawn autonomously and safely.

Besides the benefit to all of us in Ohio with lawns, the Dayton Section and the Satellite Division hope that this competition will inspire college students to pursue navigation-related research projects and careers in this field. We look forward to next year's competition, and invite anyone interested to participate or come and watch the festivities.

The lemonade is on us!

The following accounts were drawn from the student reports from each competing team.

Ohio University

Ohio University's team designed a custom chassis utilizing a 3D computer drafting program. The chassis, constructed of aluminum tubing and plating, optimizes flexibility, space utilization, weight distribution, and the ability to turn at any desired radius. The battery-powered drive system controls both rear wheels independently and can provide up to 1.5 horsepower to each drive motor, more than enough to reach and maintain the 10 kilometer/hour speed limit. A third 0.4 horsepower electric motor turns a 19-inch cutting blade. Two 24VDC batteries keep the mower going for up to 2 hours after charging.