In a feedforward control loop, how does the controller respond to a measured disturbance?

In a feedforward control loop, how does the controller respond to a measured disturbance?

• A. It reacts after the PV change.
• B. It ignores disturbances.
• C. It uses the derivative term.
• D. It adjusts the manipulated variable before the PV is affected.

Answer: (D)

Anticipating disturbances and acting before the process variable changes is what feedforward control is all about. When a disturbance is measured, the controller uses that information to adjust the manipulated variable in advance, countering the disturbance so the process variable stays near its setpoint even as the disturbance would push it away. That preemptive adjustment is why the correct choice is to modify the manipulated variable before the PV is affected. If the system only reacted after the PV changed, that would describe feedback control, not feedforward. Ignoring disturbances isn’t a viable control strategy, and relying on a derivative term is not what defines feedforward action—derivative action can be part of other control schemes, but feedforward’s unique benefit is the preemptive response based on measured disturbances.

Anticipating disturbances and acting before the process variable changes is what feedforward control is all about. When a disturbance is measured, the controller uses that information to adjust the manipulated variable in advance, countering the disturbance so the process variable stays near its setpoint even as the disturbance would push it away. That preemptive adjustment is why the correct choice is to modify the manipulated variable before the PV is affected.

If the system only reacted after the PV changed, that would describe feedback control, not feedforward. Ignoring disturbances isn’t a viable control strategy, and relying on a derivative term is not what defines feedforward action—derivative action can be part of other control schemes, but feedforward’s unique benefit is the preemptive response based on measured disturbances.