You can specify scalar weights or frequency-dependent weighting. To specify a frequency-
dependent weighting, use a numeric LTI model whose magnitude represents the desired
weighting as a function of frequency. For example, enter tf(1,[1 0.01]) to specify a
high weight at low frequencies that rolls off above 0.01 rad/s. To limit the response to a
nonuniform noise distribution, enter as WR an LTI model whose magnitude represents the
noise spectrum.
If the tuning goal constrains a MIMO transfer function, scalar or SISO weighting
functions automatically expand to any input or output dimension. You can specify different
weights for each channel by specifying MIMO weighting functions. The dimensions H(s)
must be commensurate with the dimensions of WL and WR. For example, if the
constrained transfer function has two inputs, you can specify diag([1 10]) as WR.
If you are tuning in discrete time, you can specify the weighting functions as discrete-time
models with the same sampling time as you use for tuning. If you specify the weighting
functions in continuous time, the tuning software discretizes them. Specifying the
weighting functions in discrete time gives you more control over the weighting functions
near the Nyquist frequency.
Options
Use this section of the dialog box to specify additional characteristics of the weighted
variance goal.
- Apply goal to
Use this option when tuning multiple models at once, such as an array of models
obtained by linearizing a Simulink model at different operating points or block-
parameter values. By default, active tuning goals are enforced for all models. To
enforce a tuning requirement for a subset of models in an array, select Only Models.
Then, enter the array indices of the models for which the goal is enforced. For
example, suppose you want to apply the tuning goal to the second, third, and fourth
models in a model array. To restrict enforcement of the requirement, enter 2:4 in the
Only Models text box.For more information about tuning for multiple models, see “Robust Tuning
Approaches” (Robust Control Toolbox).Weighted Variance Goal