Control theory check: compared with an open-loop system, which attribute is generally improved when feedback is added to form a closed-loop control system?

Introduction / Context:
Open-loop systems act without measuring the result; closed-loop systems measure output and compare it to a setpoint, adjusting inputs to reduce error. Adding feedback typically improves accuracy and disturbance rejection, but also introduces design trade-offs such as increased complexity and potential stability issues if the loop is not tuned correctly.

Given Data / Assumptions:

• We compare general attributes: accuracy, complexity, stability.
• Closed-loop implies sensor feedback and a controller adjusting actuation.
• “Generally improved” means the typical, intended benefit of closing the loop.

Concept / Approach:
Feedback reduces sensitivity to disturbances and to changes in plant parameters. Classical results show that, within bandwidth limits, closed-loop control diminishes steady-state error (for appropriate controller design) and compensates for certain uncertainties. However, feedback adds components (sensors, controller, filters), increasing complexity. Stability is not automatically improved; poorly tuned loops can oscillate or become unstable.

Step-by-Step Solution:

Verification / Alternative check:
Bode sensitivity relations and standard control texts confirm that feedback reduces sensitivity and steady-state error but must be tuned to maintain stability margins.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming feedback always improves stability; ignoring bandwidth and phase margin considerations that can lead to oscillations.

Final Answer:
Accuracy with respect to disturbances and parameter variations.