Tune Gain Schedules in Simulink
Typically, gain-scheduled controllers are fixed single-loop or multiloop control structures
in which controller gains vary with operating condition. A gain schedule converts the
scheduling variables that describe the current operating condition into appropriate
controller gains. In Simulink, you can implement gain schedules using lookup tables or
MATLAB functions. (See “Model Gain-Scheduled Control Systems in Simulink” on page
11-4.)You can use systune to tune these gain schedules so that the full nonlinear system meets
your design requirements. Tuning gain schedules amounts to identifying appropriate
values for lookup-table data or finding the right function to embed in a MATLAB Function
block. For systune, you parameterize the gain schedules as functions of the scheduling
variables with tunable coefficients.Workflow for Tuning Gain Schedules
The general workflow for tuning gain-scheduled control systems is:(^1) Select a set of design points that adequately covers the operating range over which
you are tuning. A design point is a set of scheduling-variable values that describe a
particular operating condition. The set of design points can be a regular grid of
values or a scattered set. Typically, you start with a few design points. If the
performance that your tuned system achieves at the design points is not maintained
between design points, add more design points and retune.
(^2) Obtain a collection of linear models describing the linearized plant dynamics at the
selected design points. Ways to obtain the array of linear models include:
- Linearize a Simulink model at each operating condition represented in the grid of
design points. For example, if each design point corresponds to a steady-state
operating condition, you can trim the plant at each design point and linearize at
the resulting operating point. Or, if your scheduling variable is time, you can
linearize at a series of simulation snapshots. - Sample an LPV model of the plant at the design points.
For more information, see “Plant Models for Gain-Scheduled Controller Tuning” on
page 11-18.(^3) Create an slTuner interface for tuning the Simulink. When you do so, you substitute
the array of linear models for the plant, so that the slTuner interface contains a set
Tune Gain Schedules in Simulink