If you see what looks like a hamster ball rolling around a cornfield, it doesn’t mean that someone’s pet is incredibly lost. It may be an experimental robot developed by the Robotics and Cybernetics Research Group at the Universidad Politécnica de Madrid (UPM) called Rosphere. The spherical robot can propel itself over uneven ground and may one day be rolling up for work in fields to monitor and tend crops.
Spherical robots aren't new. There have been a number built over the years for use in military operations, security, and experiments in space exploration. Rosphere’s approach is to take the simplicity of the sphere to make a robot that is low cost and a bit more general purpose. Its spherical shape gives the robot the ability to handle rough terrain, yet is safe to use around humans and delicate crops.
Mechanically, the Rosphere prototype is remarkably simple. The researchers compare the robot’s “mechatronics” to a hamster ball, which it strongly resembles except for the rubber ridges on the outside and the mechanical workings inside. Like a hamster making a ball roll by running up the sides to shift the center of gravity, the Rosphere uses an eccentric pendulum rotating on an axle to roll and steer itself.
The pendulum consists of ballast hanging by an arm from the ball’s axle. This ballast incorporates the robot’s battery and the axle carries Rosphere’s Wi-Fi antennas and electronics package. The pendulum has two rotational degrees of freedom along the transverse and longitudinal axes. By controlling the pendulum’s swing, the robot can roll forward and backward and steer.
UPM sees the main application for Rosphere being in precision agriculture. That is, instead of tending crops by broadcasting pesticides and fertilizers and dealing with a field as a whole, small robots can tend the individual plants like a gardener. Robots like Rosphere would be able to move about crops without damaging them, making close-up examinations of local conditions and precisely applying pesticides and fertilizers.
Tests of Rosphere were conducted on a farm where it was put up against rough terrain and different soils while testing for moisture and other environmental variables. Afterwards, it was tested at the Parque del Retiro of Madrid to see if it could operate safely with people. According to UPM, the results have so far been satisfactory.
The project results were published in Industrial Robot.
The video below shows Rosphere in action.