Feedforward gain calculator
Steady-state feedforward is one number: the gain that cancels a measured disturbance at the process variable. If you know how much the PV moves when you step the output, and how much it moves when the load steps, the feedforward gain is the negative ratio of those two.
This calculator does that ratio. It does not design the lead/lag on the feedforward path. Dynamics are a separate problem, and a static Kff on a load that arrives faster than the valve can answer will not hold the PV.
What to measure
Process gain Kp is ΔPV / ΔOP from a bump on the manipulated variable, in consistent units. Disturbance gain Kd is ΔPV / ΔD from a bump on the measured load — feed flow, inlet temperature, whatever you are compensating. Signs matter: a load that pushes the PV up and a valve that also pushes it up produce a negative Kff, which is the usual case.
What this will not fix
Feedforward does not replace the feedback loop. It takes the slow, repeatable part of a measured load off the PID. Unmeasured disturbances, a sticking valve, and a load path that is faster than the manipulated path still belong to the feedback controller — or to the mechanics.
Questions that come up
Why is the result negative?
Because the feedforward move has to oppose the disturbance. If both gains have the same sign, Kff is negative. If they have opposite signs, Kff is positive. Check the sign against which way the valve actually has to move when the load arrives.
Related
These tools assume a self-regulating loop and a bump you have not shown us. Photograph the trend and the faceplate if you want a check against the loop in front of you, not a formula.
Last reviewed 2026-09-10.