Glossary · Control theory and process control
Selective control
Also known as: Auctioneering control, Selector control
German: Auswahlregelung
In process control, selective control is a structure that uses high or low selectors to choose between several signals, either several measurements (for example the highest of several temperatures) or several controller outputs that compete for one actuator.
- Control theory
- Process industry
In one sentence
Selective control uses high or low selectors to choose among measurements or controller outputs that compete for one actuator.
Example
A reactor with five temperature sensors along its length controls the coolant with the highest measured temperature, selected by a high selector.
How it applies
- Engineering: Selecting between measurements (auctioneering) protects against hot spots; selecting between controller outputs builds Override control. Inactive controllers need output tracking and anti-windup so switching is smooth.
- Operation: The HMI should show which signal or controller is currently selected. Without this indication, operators may misinterpret the process response.
- Documentation: Describe the selector type (high or low), the signals and the reason for the selection. When measurements are selected, the failure behavior of a single sensor needs a Plausibility check: a failed sensor reading high can take over the loop.
Selective control vs. redundancy voting
Selective control picks the most critical value for control. Redundancy voting such as 2oo3 picks a validated value from redundant sensors to tolerate faults. The logic looks similar, but the purpose differs.