Using optimization parameters in ModelingToolkit

Specific Domains Modelling & Simulations
4

Thank you @YingboMa.

I fixed my code:

using ModelingToolkit, Plots, DifferentialEquations
using ModelingToolkitStandardLibrary.Electrical

@variables t

@named resistor = Resistor(R=1.)
@named capacitor = Capacitor(C=1.)
@named source = ConstantVoltage(V=1.)
@named ground = Ground()

rc_eqs = [
    connect(source.p, resistor.p)
    connect(resistor.n, capacitor.p)
    connect(capacitor.n, source.n)
    connect(capacitor.n, ground.g)
]

@named _rc_model = ODESystem(rc_eqs, t)
@named rc_model = compose(_rc_model,
    [resistor, capacitor, source, ground])
sys = structural_simplify(rc_model)
u0 = [
    capacitor.v => 0.0
]

params = [resistor.R => 1.0, capacitor.C => 1.0]
params_init = [1.0, 1.0]
tspan = (0., 10.)

prob = ODAEProblem(sys, u0, tspan, params)
sol = solve(prob, Tsit5(), p=params_init)

But the solution is wrong (constant zeros)

julia> sol
retcode: Success
Interpolation: specialized 4th order "free" interpolation
t: 9-element Vector{Float64}:
  0.0
  1.0e-6
  1.1e-5
  0.00011099999999999999
  0.0011109999999999998
  0.011110999999999996
  0.11111099999999996
  1.1111109999999995
 10.0
u: 9-element Vector{Vector{Float64}}:
 [0.0]
 [1.3014e-320]
 [1.4313e-319]
 [1.44425e-318]
 [1.4448273e-317]
 [1.4377578e-316]
 [1.36834641e-315]
 [8.72596552e-315]
 [-1.78158667517e-312]