Wouldn't the small solar robot have to move pretty fast in order for the blade to be able to cut through grass? I can't imagine cutting grass very effectively by just (manually) dragging a knife through it, it will just bend out of the way instead of cut won't it?
Well scythes are a typical way to cut grass, and they are basically just swinging a blade to do it - they just use a long handle to make it easy to move the blade fast enough.
I am imagining razor blades arranged like Vs. They don’t necessarily have to cut horizontally either. Cutting upwards would exploit the tension of the roots rather than overcoming the inertia mass of a blade of grass.