Glossary · Control theory and process control
Advanced process control (APC)
Also known as: APC, Advanced control
German: Advanced Process Control (APC)
In process automation, advanced process control (APC) is the collective term for control techniques that go beyond single PID loops, such as model predictive control, multivariable control, inferential measurements and optimization layers running above the basic regulatory control.
- Control theory
- Process industry
In one sentence
APC covers control techniques above single PID loops, such as model predictive and multivariable control, used to run a process closer to its limits.
Example
A refinery runs an APC application on the distillation column that writes setpoints to the basic PID loops to maximize product yield within quality and equipment constraints.
How it applies
- Engineering: APC normally sits on top of well-tuned basic regulatory control in the Distributed control system (DCS). It writes setpoints to PID controller loops rather than driving valves directly, so the plant can fall back to basic control if APC is switched off.
- Operation: Operators need clear indication of whether APC is on, which loops it currently manipulates and which constraints are active. A defined, Bumpless transfer back to basic control is essential.
- Maintenance: APC models degrade when the process or equipment changes. Plan periodic model reviews and treat model updates under Management of change (MOC).
- Documentation: Document the controlled, manipulated and disturbance variables, the constraint limits, the switch-off procedure and the owner of the application. Operator manuals should explain APC in terms of what the operator sees and can do, not in terms of the mathematics.
APC vs. AI-based control
APC traditionally relies on identified process models and optimization. Data-driven methods from Machine learning (ML) can supplement it, for example as soft sensors, but they don't replace validation of the control behavior.