| closed-loop control, able to keep system properties within a prescribed area even if the properties of the controlled system or the properties of the controller deviate from those assumed for the design of the control system by not more than a predetermined amount.|
Note 1 to entry: Properties of the control system may be its stability, the damping ratio of its transfer function, or the overshoot of its unit-step response.
Note 2 to entry: Properties of the controlled system or the controller e.g. can deviate because disturbances, delays or dead times have not been taken into consideration, parameters are influenced by variable operating conditions, or the controller has been implemented in a non-ideal way.
Note 3 to entry: Phase margin or gain margin may be used to describe the robustness of a control loop.
Note 4 to entry: This entry was numbered 351-26-39 in IEC 60050-351:2006.