Nominal value of uncertain model
Create a model of a mass-spring-damper system in which the mass, spring constant, and damping constant are all uncertain.
m = ureal('m',3,'percent',40); k = ureal('k',2,'percent',30); c = ureal('c',1,'percent',20); G = tf(1,[m,c,k])
G =
Uncertain continuous-time state-space model with 1 outputs, 1 inputs, 2 states.
The model uncertainty consists of the following blocks:
c: Uncertain real, nominal = 1, variability = [-20,20]%, 1 occurrences
k: Uncertain real, nominal = 2, variability = [-30,30]%, 1 occurrences
m: Uncertain real, nominal = 3, variability = [-40,40]%, 1 occurrences
Type "G.NominalValue" to see the nominal value, "get(G)" to see all properties, and "G.Uncertainty" to interact with the uncertain elements.
G is a uss model. Extract its nominal value.
Gnom = getNominal(G);
Because G has only uncertain control design blocks, Gnom is a numeric state-space (ss) model.
Combine G with a tunable PID controller.
C = tunablePID('C','pid'); T = feedback(G*C,1)
T =
Generalized continuous-time state-space model with 1 outputs, 1 inputs, 3 states, and the following blocks:
C: Tunable PID controller, 1 occurrences.
c: Uncertain real, nominal = 1, variability = [-20,20]%, 1 occurrences
k: Uncertain real, nominal = 2, variability = [-30,30]%, 1 occurrences
m: Uncertain real, nominal = 3, variability = [-40,40]%, 1 occurrences
Type "ss(T)" to see the current value, "get(T)" to see all properties, and "T.Blocks" to interact with the blocks.
T is a generalized state-space (genss) model that has both tunable and uncertain blocks. Extract the nominal value of T.
Tnom = getNominal(T)
Tnom =
Generalized continuous-time state-space model with 1 outputs, 1 inputs, 3 states, and the following blocks:
C: Tunable PID controller, 1 occurrences.
Type "ss(Tnom)" to see the current value, "get(Tnom)" to see all properties, and "Tnom.Blocks" to interact with the blocks.
Extracting the nominal value of T preserves the tunable control design block, resulting in another genss model.
M — Uncertain model or matrixUncertain model or matrix, specified as a dynamic system model
or static model. Typically, M is a model that
contains uncertainty, such as a uss, uncertain genss,
or umat model.
Mnom — Nominal model or matrixNominal value of M, returned as a dynamic
system model or static model. Mnom has no uncertain
blocks.
The model type of Mnom depends on the type
of M. For example, if M is
a genss model with uncertain blocks and tunable
blocks, then Mnom is a genss model
with tunable blocks.
If M contains no control design blocks
other than uncertain blocks, then Mnom is a state-space
(ss) model, an frd model,
or a numeric array, depending on the type of M.
For example, if M is a uss model,
then Mnom is a ss model.
If M is a umat, then Mnom is
a numeric array.
If M has no uncertain blocks, then Mnom = M.
You have a modified version of this example. Do you want to open this example with your edits?