Glossary · Control theory and process control
Multivariable control
Also known as: MIMO control, Multi-input multi-output control
German: Mehrgrößenregelung
In control engineering, multivariable control is the control of a process with several interacting manipulated and controlled variables, designed as one controller that takes the interactions into account instead of as independent single loops.
- Control theory
- Process industry
In one sentence
Multivariable control handles processes with several interacting inputs and outputs in one coordinated controller.
Example
In a distillation column, reflux and reboiler duty both affect top and bottom purity, so a multivariable controller adjusts them together.
How it applies
- Engineering: Interacting loops tuned independently can fight each other. Multivariable approaches include decoupling networks, state feedback based on a State-space model and Model predictive control (MPC). An interaction analysis, comparable to a Coupling analysis in systems engineering, shows whether single loops are sufficient.
- Commissioning: Identification requires step tests on each manipulated variable, which takes time on slow processes. Plan the test program with operations.
- Documentation: Show which variables the controller manipulates and which it controls, with their priorities and limits. Operators need to know that changing one target can move several valves.
Multivariable control vs. single-loop control
Single-loop control pairs one measurement with one actuator. Multivariable control treats the process as a whole, which pays off when interactions are strong.