Pee Dee Precision, a local advanced agricultural robotics team, won 2nd place in the international Agbot competition. The award was for their work towards building a semi-automated watermelon harvester. The advantage the harvester had over its competitors was a unique way of combining a test for ripeness into the design of the harvest mechanism.
The design of the agbot started in November as soon as the contest criteria were released. The team assembled to take on the challenge was Robby Jowers, a Francis Marion graduate skilled in agriculture research; Smith Gaddy, a Citadel Graduate skilled in node.js development; and Jerry Martin, a Clemson and NC State graduate with 12 years of experience in agriculture engineering research. Prior to development an ATV donated by Yamaha Ventures in Silicon Valley, CA, was outfitted with basic teleoperation capability. The modified ATV was showcased along with its image processing capability at the SC Agribiz Expo. While at the expo over 20 full time watermelon producers were consulted about the basics of watermelon growing operations, as well as tricks of the trade to determine ripeness. All the ideas were collected then the watermelon harvester was designed.

On competition day each team presented. The part of Pee Dee’s presentation of particular interest to the crowd was the talk given on watermelon ripeness detection. The ripeness detection story led off with a retelling of a retelling of a pivotal moment in agricultural history which took place in South Carolina in the 1860’s. In the wake of the civil war a northerner from the federal government came to South Carolina earning the respect of the locals. He was then guided to the great halls in Charleston. Afterwards he sailed through the port at Georgetown up the Pee Dee River. (In his journal he spelled the river Peedee of which is the inspiration behind the Pee Dee Precision name. The name at least one northern newspaper was spelled Peedee Precision. Both spellings have been adopted by the team as correct.) As a result of Kelly’s trip an organization ignited the progressive agrarian reforms of the late 1800’s, as well as a series of technological advancements of that era including glass greenhouses, use of fertilizer, early tractors, and early selective hybridization techniques. In this century the story was retold in conjunction with a watermelon seed spitting competition. Prior to the competition a series of melons was selected from the Pee Dee State Farmers Market by thumping the melons. Thumping a melon is similar to thumping a wine glass. A wine glass resonates at a very specific frequency as determined by the contents of the glass.
The content of a watermelon resonates at a specific frequency when the melon is nearing ripeness.
As opposed to thumping the melon, ripeness was detected by sweeping harmonics through a speaker near the melon. A microphone was used to detect the frequency of oscillation. The oscillation of a ripe melon could be felt, and based on the sound and image was created. The created image was run through an image detection algorithm to determine ripeness.
The team from Virginia Tech placed first in the competition. Their guidance equipment and speed control was very good making for much more accurate navigation. Pee Dee Precision may compete again as another competition is scheduled for next year.