getOffsetsForLPV
Extract LPV offsets from linearization results
Description
extracts
linearization offsets from offsets
= getOffsetsForLPV(info
)info
and converts
them to the array format supported by the LPV
System block.
Examples
Extract LPV Offsets from Linearization Results
Open the Simulink® model.
model = 'watertank';
open_system(model)
Specify linearization I/Os.
io(1) = linio('watertank/Desired Water Level',1,'input'); io(2) = linio('watertank/Water-Tank System',1,'output');
Vary plant parameters A
and b
, and create a 3-by-4 parameter grid.
[A_grid,b_grid] = ndgrid(linspace(0.9*A,1.1*A,3),linspace(0.9*b,1.1*b,4)); params(1).Name = 'A'; params(1).Value = A_grid; params(2).Name = 'b'; params(2).Value = b_grid;
Create a linearization option set, setting the StoreOffsets
option to true
.
opt = linearizeOptions('StoreOffsets',true);
Linearize the model using the specified parameter grid, and return the linearization offsets in the info
structure.
[sys,op,info] = linearize('watertank',io,params,opt);
Extract the linearization offsets.
offsets = getOffsetsForLPV(info)
offsets = struct with fields: x: [2x1x3x4 double] y: [1x1x3x4 double] u: [1x1x3x4 double] dx: [2x1x3x4 double]
To configure an LPV System block, use the fields from offsets
directly.
Input Arguments
info
— Linearization information
structure
Linearization information returned by exact linearization commands,
specified as a structure. This structure has an Offsets
field
that contains an N1-by-...
-by-Nm array
of structures, where N1 to Nm are
the dimensions of the operating point array or parameter grid used
for linearization. Each structure in info.Offsets
contains
offset information that corresponds to a specific operating point.
You can store and obtain linearization offsets when you linearize your model using one of the following commands:
For example:
opt = linearizeOptions('StoreOffsets',true);
[sys,op,info] = linearize(mdl,io,params,opt);
You can then extract the offset information using getOffsetsForLPV
.
offsets = getOffsetsForLPV(info);
Output Arguments
offsets
— Linearization offsets
structure
Linearization offsets corresponding to the operating points at which the model was linearized, returned as a structure with the following fields:
Field | Description |
---|---|
x | State offsets used for linearization, returned as an nx-by-1-by-N1-by-... -by-Nm array,
where nx is the number of
states in the linearized system. |
y | Output offsets used for linearization, returned as an ny-by-1-by-N1-by-... -by-Nm array,
where ny is the number of
outputs in the linearized system. |
u | Input offsets used for linearization, returned as an nu-by-1-by-N1-by-... -by-Nm array,
where nu is the number of
inputs in the linearized system. |
dx | Derivative offsets for continuous time systems, or updated
state values for discrete-time systems, returned as an nx-by-1-by-N1-by-... -by-Nm array. |
For instance, suppose that your model has three inputs, two
outputs, and four states. If you linearize your model using a 5-by-6
array of operating points, offsets
contains arrays
with the following dimensions:
offsets.x
— 4-by-1-by-5-by-6offsets.y
— 2-by-1-by-5-by-6offsets.u
— 3-by-1-by-5-by-6offsets.dx
— 4-by-1-by-5-by-6
To configure an LPV System block,
you can use the fields of offsets
directly. For
an example, see Approximate Nonlinear Behavior Using Array of LTI Systems.
Version History
Introduced in R2016b
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