Skip to content

debug: linearize! on NonLinModel with non-zero operating points now works #239

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Sep 4, 2025
Merged

debug: linearize! on NonLinModel with non-zero operating points now works #239

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
37831a9
debug: use `linmodel.buffer` in `linearize!`
franckgaga Sep 4, 2025
d45ef86
debug: idem
franckgaga Sep 4, 2025
8d0dfb8
debug: idem
franckgaga Sep 4, 2025
345c605
test: `NonLinModel` linearization with non zero op. points
franckgaga Sep 4, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
29 changes: 16 additions & 13 deletions src/model/linearization.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -157,9 +157,9 @@ julia> linearize!(linmodel, model, x=[20.0], u=[0.0]); linmodel.A
```
"""
function linearize!(
linmodel::LinModel{NT}, model::SimModel;
linmodel::LinModel, model::SimModel;
x=(model.buffer.x.=model.x0.+model.xop), u=model.uop, d=model.dop
) where NT<:Real
)
nonlinmodel = model
buffer = nonlinmodel.buffer
# --- remove the operating points of the nonlinear model (typically zeros) ---
Expand All @@ -172,16 +172,19 @@ function linearize!(
# --- compute the nonlinear model output at operating points ---
x0next, y0 = linmodel.buffer.x, linmodel.buffer.y
h!(y0, nonlinmodel, x0, d0, model.p)
y = y0
y .= y0 .+ nonlinmodel.yop
y0 .+= nonlinmodel.yop
y = y0
# --- compute the nonlinear model next state at operating points ---
f!(x0next, k0, nonlinmodel, x0, u0, d0, model.p)
xnext = x0next
xnext .= x0next .+ nonlinmodel.fop .- nonlinmodel.xop
x0next .+= nonlinmodel.fop
xnext = x0next # xnext = f(x0,u0,d0) + fop - xop + xop = f(x0,u0,d0) + fop
# --- recompute x since it was modified in buffer.x ---
x0 .+= nonlinmodel.xop
x = x0
# --- modify the linear model operating points ---
linmodel.uop .= u
linmodel.yop .= y
linmodel.dop .= d
linmodel.yop .= y
linmodel.xop .= x
linmodel.fop .= xnext
# --- reset the state of the linear model ---
Expand All @@ -190,14 +193,14 @@ function linearize!(
end

"Call `linfunc!` function to compute the Jacobians of `model` at the linearization point."
function linearize_core!(linmodel::LinModel, model::SimModel, x0, u0, d0)
x0next, y0 = linmodel.buffer.x, linmodel.buffer.y
function linearize_core!(linmodel::LinModel, model::SimModel, x, u, d)
xnext, y = linmodel.buffer.x, linmodel.buffer.y
A, Bu, C, Bd, Dd = linmodel.A, linmodel.Bu, linmodel.C, linmodel.Bd, linmodel.Dd
cst_x = Constant(x0)
cst_u = Constant(u0)
cst_d = Constant(d0)
cst_x = Constant(x)
cst_u = Constant(u)
cst_d = Constant(d)
backend = model.jacobian
model.linfunc!(x0next, y0, A, Bu, C, Bd, Dd, backend, x0, u0, d0, cst_x, cst_u, cst_d)
model.linfunc!(xnext, y, A, Bu, C, Bd, Dd, backend, x, u, d, cst_x, cst_u, cst_d)
return nothing
end

Expand Down
16 changes: 16 additions & 0 deletions test/1_test_sim_model.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -371,6 +371,22 @@ end
h2!(y0, x0, _, _) = (y0 .= x0)
nonlinmodel4 = NonLinModel(f2!,h2!,Ts,1,1,1,0,solver=nothing,jacobian=AutoFiniteDiff())
@test_nowarn linearize(nonlinmodel4, x=[1], u=[2])

# test linearization with nonzero operating points in the NonLinModel object:
linmodel_op = LinModel(tf(2, [10, 1]),1)
linmodel_op = setop!(linmodel_op, uop=[10], yop=[20], xop=[-2], fop=[5])
f3!(xnext, x, u, _, p) = (xnext .= p.A*x .+ p.Bu*u)
h3!(y, x, _, p) = (y .= p.C*x)
nonlinmodel_op = NonLinModel(f3!, h3!, 1.0, 1, 1, 1, p=linmodel_op, solver=nothing)
nonlinmodel_op = setop!(linmodel_op, uop=[10], yop=[20], xop=[-2], fop=[5])
linmodel_op_2 = linearize(nonlinmodel_op)
@test linmodel_op.A ≈ linmodel_op_2.A
@test linmodel_op.Bu ≈ linmodel_op_2.Bu
@test linmodel_op.C ≈ linmodel_op_2.C
@test linmodel_op.uop ≈ linmodel_op_2.uop
@test linmodel_op.yop ≈ linmodel_op_2.yop
@test linmodel_op.xop ≈ linmodel_op_2.xop
@test linmodel_op.fop ≈ linmodel_op_2.fop
end

@testitem "NonLinModel real time simulations" setup=[SetupMPCtests] begin
Expand Down