When actuating motion, you should specify position, velocity, and acceleration (not or). When nothing is attached to an input, it sees that as being 0. Effectively what has happened is that you have commanded it to keep the position at 0 for the entire simulation.
If you know the desired acceleration, you can integrate it once for velocity and again for position. However, it is not recommended to use a numerical derivative directly when going from position to acceleration. Numerical derivatives are notoriously messy, and numerical second derivatives are a recipe for trouble.
I would recommend you take a look at the documentation here regarding stabilizing numerical derivatives.
