Glossary · Control theory and process control
Overshoot
Also known as: Maximum overshoot, Percent overshoot
German: Überschwingen
In control engineering, overshoot is the amount by which the controlled variable exceeds its final steady-state value after a step change, usually expressed as a percentage of the step size.
- Control theory
In one sentence
Overshoot is how far the controlled variable exceeds its final value after a step, usually given as a percentage of the step.
Example
After a setpoint step from 20 to 60 °C, the temperature peaks at 64 °C, an overshoot of 10 percent.
How it applies
- Engineering: Overshoot relates to damping: small Phase margin usually means large overshoot. Some processes must not overshoot at all, for example temperature near a material's decomposition limit or a positioning axis near an end stop.
- Commissioning: Measure overshoot for the specified step size; saturation and windup can make large steps overshoot much more than small ones.
- Documentation: Where overshoot is a requirement, state the step size, the operating point and the tolerance. In operating manuals, warn about situations in which overshoot is expected, such as startup from cold.
Overshoot vs. settling time
Overshoot measures the peak; Settling time measures how long it takes to stay within a tolerance band. Reducing overshoot by detuning often increases rise time, so both are specified together.