How to Build a Robotic Arm to Cut Weeds

We use, like we call them robotic arm. They're not your typical 15 degrees of freedom type of robotic arm. Each blade can essentially move left and right. And then the entire thing can move up and down to follow the bumps of the field. So these three degrees of freedom are essentially enough for the precision that we need. We want the blades to follow a path which is almost in a 2D plane, but not exactly.