Force, Velocity, Other? - AI

I'm scripting AI, something new for me. I was going to use a RayCast to keep it grounded and then just use transform for movement, but was wondering if Force or Velocity would be good for this too? I have tested on a little hill and the toon get's stuck with too little force or velocity (too much is too fast), and lands slowly like with car physics when coming off the hill. So, what are your recommendations? I need a constant speed, and the toon to stay grounded. I'm thinking force and velocity are the wrong answer but wanted to be sure.