A "command signal from an external operator".

Feedforward is the unknown genius cousin to feedback. It is a term that was coined originally in systems thinking which has now expanded into much broader use. Specifically, I am referring to the classroom.

not error-based. Instead it is based on knowledge about the process in the form of a mathematical model of the process and knowledge about or measurements of the process disturbances.[1]http://en.wikipedia.org/wiki/Feed_forward_%28control%29