Process adjustment strategy is an important part of the process improvement
methods, which is also called engineering process control (EPC), and it is often
integrated with statistical process control (SPC) to improve the process control
performance. While feedback control is used to compensate for the output deviation,
feedforward control is a proactive control strategy based on a direct measurement of the
disturbance, and it acts before the disturbance affects the system. Feedforward control is
usually combined with feedback control for variation reduction. In this article, rationales for feedforward control are explained, and a new philosophy on its application is given.The feasibility condition for feedforward control application illustrated from a new disturbance decomposition viewpoint, and the validity of some disturbance models
which work well for feedforward control is investigated. Some relevant issues on
process monitoring, feedback control and feedforward control are discussed and
addressed