Glossary · Automation fundamentals, platforms and components
Feedforward (control)
Also known as: Feedforward control, Disturbance feedforward
German: Vorsteuerung
In control engineering, feedforward is a control action calculated from the setpoint or a measured disturbance and applied directly to the manipulated variable, before the effect shows up in the controlled variable.
- Automation components
In one sentence
Feedforward applies a control action calculated from the setpoint or a measured disturbance before the controlled variable deviates.
Example
A servo axis uses velocity feedforward, so the drive already outputs the required speed while the position controller only corrects small deviations.
How it applies
- Engineering: Feedforward requires a model of how the process reacts. It is usually combined with feedback, which corrects model errors.
- Commissioning: Feedforward gains are tuned separately from the feedback controller; wrong gains cause overshoot.
- Documentation: Control descriptions should state which feedforward terms exist and which signals they use, so maintenance staff know that a faulty disturbance sensor also affects control quality.
- Operation: When a feedforward sensor fails, some systems switch to pure feedback control; operators should know that control quality then drops.
Feedforward vs. feedback
Feedback (control engineering) reacts to deviations after they occur. Feedforward acts in advance based on known inputs but cannot correct what it does not know. The German "Vorsteuerung" is commonly used for feedforward on setpoints in drive technology, and "Störgrößenaufschaltung" for feedforward on disturbances.