"The BeachBot is an autonomous robot that can create large-scale sand art. The robot will be used at a public beach to amaze beachgoers who pass by. Not only the final picture is important, but the whole drawing process will also provide an extraordinary, magical show. The BeachBot is not just a lifeless, mechanical being; it is a friendly looking creature. The BeachBot is 60 cm in length and 40 cm in both width and height. To provide maximal mobility and enough robustness a three wheel arrangement with a differential drive back wheels and a steered wheel in the front are used. The BeachBot carves pictures into the sand with a rake consisting of seven individual movable elements actuated by servo motors. They attached to the tail of the robot. This solution leads to an excellent visibility of the drawn lines and a large variety in line width, from minimal 5 cm up to the width of the robot."
Take a look at a video explaining more about Beachbot, and a time-lapse video of it creating art.