If I were you I'd look at getting a stepper motor driver module. They can usually run off an unregulated supply of any voltage from 12 to 30V, are fairly universal so will be able to run pretty much any bipolar motor in series or parallel, and take simple logic inputs for step, direction, hold signals etc. I used them and two stepper motors to automate a telescope and they were great. Take care of all the PWM, current limiting correct phases of the coils and so on...
