How to make a mob move in a constant direction at a certain speed

I'm trying to make an autominer mod, and to make the miner bots I'm using mobs. How could I program it so it goes in a certain direction at a certain speed? I tried using the "move" block in the onMobTickUpdate loop (so it runs once a tick) but that makes it go too fast and I don't know how to make it go slower.