Glossary · Control theory and process control
Bumpless transfer
Also known as: Bumpless switchover
German: Stoßfreie Umschaltung
In control engineering, bumpless transfer is the switching between operating modes of a controller, such as manual and automatic, or between two controllers, without a sudden jump in the controller output.
- Control theory
In one sentence
Bumpless transfer switches a controller between manual and automatic, or between controllers, without a jump in the output.
Example
When the operator switches a flow loop from manual to automatic, the controller initializes its integral term to the current valve position so the valve does not move abruptly.
How it applies
- Engineering: Typical techniques are output tracking (the inactive controller follows the active output), setpoint tracking in manual mode and initialization of the integral term at switchover. In Cascade control, the secondary loop must be in automatic before the primary loop can be switched without a bump.
- Operation: The Faceplate should show the current mode and whether setpoint tracking is active, so operators know what will happen when they switch.
- Documentation: Operator instructions should say in which order to switch loops (inner before outer) and what the controller does with the setpoint at switchover. Control narratives should list the tracking behavior for each mode change.
Bumpless transfer vs. anti-windup
Bumpless transfer concerns the moment of switching. Anti-windup concerns saturation during automatic operation. Both are usually configured in the same PID function block.