In this second video of the Robust Control series, we analyze how a closed-loop system behaves under small and large process variations — a core concept in robust control design.
Topics covered:
1. Transfer function T(s) and its sensitivity to plant variations ΔGs
2. Small variations: when the sensitivity S is small → plant variations are attenuated; when S is large → variations are amplified
3. Two important notes: only the magnitude of S matters (not the phase), and G_R is fixed while G_s is uncertain
4. Large variations: stability condition using |G_R·ΔGs| and the Nyquist plot
5. Conservative estimation: bounding |ΔGs| using the maximum of |T(jω)|
6. If T is small → the system is robust to plant changes
