OSAKA, Jun. 12 – A floating spherical weeding robot with dents on its surface gathered attention at the 2025 Osaka-Kansai Expo. The idea is to control the growth of waterweed by turning the water cloudy with the robot rolling around afloat. A consortium formed by the Prefectural University of Kumamoto and the National Institute of Technology (KOSEN), Kumamoto College, demonstrated the robot as a means to help grow rice more easily in rice fields with some difficulties, such as stepped rice terraces. The robot was exhibited at the expo for three days, until June 11, as part of its weekly program, “Necessities of Life: Food, Clothing and Shelter.”
The robot is 28 centimeters in diameter and has 48 dents, each approximately 3 centimeters in diameter and surrounded by bumps. The ball-like shape makes it easier to access narrow corners of rice paddies. The consortium began developing it in 2019, and the one exhibited at the expo was an improved version capable of increasing rolling speed, allowing it to move around in rice paddies with varying heights. It can also change direction automatically when it detects an obstacle. With a three-hour charge, it operates for six hours.
A 51-year-old visitor to the expo from Takashima City, Shiga Prefecture, grows rice on his 15-hectare field. “I would like to have one, if it leads to less work and herbicide,” he said. “Protecting rice terraces that provide a diverse ecosystem is a universal challenge,” Naotaka Matsuzoe, the lead researcher from the university’s Faculty of Environmental & Symbiotic Sciences, said. “We could propose one way to solve this problem at the expo,” he stressed.
A spherical weeding robot, showcased at the 2025 Osaka-Kansai Expo, began rolling swiftly. Professor Junichiro Yuji of the Kumamoto National College of Technology (right) operated the robot as Professor Matsuzoe (left) observed. (In Osaka City, Osaka Prefecture).