Terminology: the response of a linear control system to a change in set point is called what?

Introduction / Context:
Control problems are often classified by the source of the change driving the system away from its current operating point. Changes in the set point (reference) constitute one class, and external disturbances constitute another. Knowing the correct terminology clarifies tuning goals and performance metrics.

Given Data / Assumptions:

• Linear time-invariant system context.
• We are comparing standard terms: servo vs. regulator.
• Focus is on the type of input change that triggers the response.

Concept / Approach:
When the reference (set point) changes and the loop must track the new target, the task is a servo problem. When the set point is held constant but disturbances enter (e.g., load changes), the controller’s job is regulation. Frequency response is a frequency-domain characterization method, not a time-domain classification of the cause of change.

Step-by-Step Solution:

Verification / Alternative check:
Standard texts define servo tests as step/ramps in the reference, evaluating rise time, overshoot, and steady-state error; regulator tests apply disturbances at the plant input/output with set point held constant.

Why Other Options Are Wrong:

Common Pitfalls:
Mixing “transient response” (a property) with “servo/regulator” (a scenario classification). Both can be discussed simultaneously but refer to different aspects.

Final Answer:
servo problem