Maximum Loop Gain Goal
Purpose
Suppress gain of feedback loops at high frequency when using Control System Tuner.Description
Maximum Loop Gain Goal enforces a maximum loop gain in a particular frequency band.
This tuning goal is useful, for example, for increasing system robustness to unmodeled
dynamics.Maximum Loop Gain Goal imposes a maximum gain on the open-loop frequency response
(L) at a specified location in your control system. You specify the maximum open-loop gain
as a function of frequency (a maximum gain profile). For MIMO feedback loops, the
specified gain profile is interpreted as an upper bound on the largest singular value of L.When you tune a control system, the maximum gain profile is converted to a maximum
gain constraint on the complementary sensitivity function, T = L/(I + L).The following figure shows a typical specified maximum gain profile (dashed line) and a
resulting tuned loop gain, L (blue line). The shaded region represents gain profile values
that are forbidden by this requirement. The figure shows that when L is much smaller
than 1, imposing a maximum gain on T is a good proxy for a maximum open-loop gain.10 Control System Tuning