Multiple Design Points in slTuner Interface
For tuning a gain-scheduled control system, you must make your Simulink model linearize
to an array of LTI models corresponding to the various operating conditions that are your
design points. Thus, after you obtain a family of linear plant models as described in “Plant
Models for Gain-Scheduled Controller Tuning” on page 11-18, you must associate it with
the slTuner interface to your Simulink model. To do so, you use block substitution to
cause slTuner replace the plant subsystem of the model with the array of linear models.
This process builds a family of tunable closed-loop models within the slTuner interface.Block Substitution for Plant
Suppose that you have an array of linear plant models obtained at each operating point in
your design grid. In the most straightforward case, the following conditions are met:- The linear models in the array correspond exactly to the plant subsystem in your
model. - Other than the elements you want to tune, nothing else in the model varies with the
scheduling variables.
For a Simulink model mdl containing plant subsystem G, and a linear model array Garr
that represents the plant at a grid of design points, the following commands create an
slTuner interface:BlockSubs = struct('Name','mdl/G','Value',Garr);
st0 = slTuner('mdl',{'Kp','Ki'},BlockSubs);st0 contains a family of closed-loop linear models, each linearized at a design point, and
each with the corresponding linear plant inserted for G. If 'Kp'and 'Ki' are the gain
schedules you want to tune (such as lookup tables), you can parameterize them with
tunable gain surfaces, as described in “Parameterize Gain Schedules” on page 11-32,
and tune them.Multiple Block Substitutions
In other cases, the linearized array of plant models you have might not correspond exactly
to the plant subsystem in your Simulink model. Or, you might need to replace other parts
of the model that vary with operating condition. In such cases, more care is needed in
constructing the correct block substitution. The following sections highlight several such
cases.11 Gain-Scheduled Controllers