Bulb ramping usually refers to transitioning between different shutter speeds you specify. Arsenal takes a different approach that we believe is both easier and better. 

We have an auto-exposure algorithm similar to the ones that cameras use to set exposure. Instead of setting exposure based on a short grab from the sensor, Arsenal's timelapse mode sets the exposure based on the auto-exposure values from the previous shots. (We added a smoothing factor to make the transitions in exposure more natural.)

The benefit of this approach is you don't have to guess on shutter speeds. You can set your preferred ranges for shutter, ISO, and aperture, instructing Arsenal to stay within those ranges when adjusting exposure.