Glossary · Control theory and process control
Controlled system
Also known as: Plant (control theory), Process (control theory)
German: Regelstrecke
In control engineering, the controlled system is the part of a control loop that is influenced by the manipulated variable and whose output is the controlled variable, such as a tank, a heat exchanger or a drive axis.
- Control theory
In one sentence
The controlled system is the part of a loop acted on by the manipulated variable and producing the controlled variable, such as a tank or an axis.
Example
For a furnace temperature loop, the controlled system includes the burner, the furnace chamber and the load, from the fuel valve position to the measured temperature.
How it applies
- Engineering: Controller design starts with a model of the controlled system: gain, time constants, dead time or a State-space model. The model determines which controller type and tuning are suitable.
- Commissioning: Step tests on the controlled system provide the data for tuning. Record the operating point, because many systems behave differently at low and high load.
- Documentation: Where the boundary of the controlled system lies (does it include the valve? the sensor?) should be stated explicitly, in the same way as a System boundary in systems engineering.
Controlled system vs. control system
The controlled system is what is being controlled (the plant or process). The Control system is what does the controlling. In English the word "plant" is used in control theory for the controlled system, which can be confused with a production plant.