[Jared Russell]

A feedforward gain is useful if you are doing velocity control, motion profiling, or compensating for some known external force (e.g. gravity). The latter two applications are applicable to an arm or elevator system.

While a constant velocity test is the simplest way to calculate this gain, it isn't the only way. The first step is an initial guess. This is usually pretty easy...All you need to do is figure out the free speed of your mechanism by looking at your motor specs and effective gear ratio (and compensating for efficiency losses if you want). Kf = Full power / free speed. Once you have this guess, come up with a couple reference motion profiles to test and use a controller to follow them using *only* feedforward gain. This won't be precise or robust of course, but it should give you a way to figure out if you require more or less. Iteratively tune your feedforward gain until you are tracking various profiles closely. Remember, it doesn't have to be perfect...That's why we use feedback.