Settling Time
Settling time is the time it takes, after a command change, for the system to stay permanently within a narrow band around the target; the band is usually defined as 2 to 5 percent of the target. It is the most concrete measure describing the speed of the control and it is assessed together with overshoot.
To measure it a command is given and the speed or position is followed over time. Two numbers are recorded: the peak deviation and the moment at which the value stays permanently inside the band. On the same system, increasing the gain shortens the settling time but increases the overshoot; lengthening the ramp time reduces the overshoot but delays the settling.
- On the engine side what determines the settling time is largely its inertia and the turbo response; the controller cannot speed this up however much it wants.
- On the actuator side it is cable friction and the ramp time that are decisive.
In practice, knowing this time lets you set expectations: on the GS740-3P, after the potentiometer is turned, the throttle lever reaching the target on its ramp and the engine settling at the new speed happen one after the other. In work such as drilling, waiting for the system to settle before taking a measurement after a speed change prevents you from making a wrong adjustment.
Context in which this term is used: Electronic speed and throttle control on a diesel engine