The velocity of a standard DC motor is controlled by the voltage applied. For stepper and BLDC motors, the current for different motor windings needs to be controlled. During acceleration, velocity increases continuously - otherwise known as ramping.
The simplest way is to drive a stepper motor in full-step mode or a synchronous AC motor in block commutation. With sinusodial waveforms the motor runs much smoother and often more precise.
Motion control without feedback assumes that the motor always behaves as expected. Under common conditions, the motor's position is deterministic and predictable. To handle uncommon conditions, motors need to be operated with safety margins. This can lead to reduced efficiency and performance.