An axle is a rod or bar that turns. It usually connects two wheels. If a truck has six wheels, then it has three axles. English doesn't usually count axles, we say six-wheeled or six-wheeler. Although six-axled could be a word.
An axis is mostly used in math or to define a Drehachse--an axis of rotation. There are three axes (the plural is axEs) x, y, z. So, left-right, front-back, and top-bottom. Something that spins on an axis can usually be described in terms of the three different directions. The shoulder for example, is a called multiaxial. You can rotate it in several differnt planes. And "axial" could refer to either axle or axis I guess.
So to answer your question, i don't know. If the robot has six wheels and three axles call it six-wheeled or a six-wheeler or six-axled if you want. If you want to say it can rotate in many different directions, maybe call it multiaxial or just say something like "capable of fluid motion" but like I said, I'm unfortunately not up to speed on robotics terminology. Hope that helps.
If you want to describe exactly what you want to say, or give more context I can probably help you.