[Kevin Sevcik]

A feedforward term in a control loop is a term that adds to the control output based directly off of the command input or some feature thereof. It doesn't depend on any feedback, it purely feeds the command signal forward through the control loop.

For instance, in the case of controlling a shooter wheel, there's a theoretical minimum voltage necessary to run the wheel at the correct speed. Based off this, you could create a feedforward term in your control loop. Take a CIM with no reduction. 12V free speed is 5400RPM. So, if you want to run it at 2700RPM, you know you need atleast 6V output. You create a feed forward term with a gain of (12V/5400RPM). Then, your output is PID output + RPMs * (12V/5400RPM). That way, when you command 2700 RPM, you're already outputting the necessary 6V to run at that speed. Your PID loop now only has to compensate for the difference between free speed and your loaded speed. Plus, you're instantly outputting 6V without waiting for an I term to build up enough error to put out 6V for you. Basically, feedforward terms improve the response of your control loop based off features you already know about your system.