fix: handle observed in remake_initializeprob

Author: AayushSabharwal

src/systems/nonlinear/initializesystem.jl

@@ -225,7 +225,7 @@ function SciMLBase.remake_initializeprob(sys::ODESystem, odefn, u0, t0, p)
         u0idxs = Int[]
         u0vals = []
         for sym in variable_symbols(oldinitprob)
-            if is_variable(sys, sym)
+            if is_variable(sys, sym) || has_observed_with_lhs(sys, sym)
                 u0 !== missing || continue
                 idx = variable_index(oldinitprob, sym)
                 push!(u0idxs, idx)
@@ -247,8 +247,16 @@ function SciMLBase.remake_initializeprob(sys::ODESystem, odefn, u0, t0, p)
                 end
             end
         end
-        newu0 = remake_buffer(oldinitprob.f.sys, state_values(oldinitprob), u0idxs, u0vals)
-        newp = remake_buffer(oldinitprob.f.sys, parameter_values(oldinitprob), pidxs, pvals)
+        if isempty(u0idxs)
+            newu0 = state_values(oldinitprob)
+        else
+            newu0 = remake_buffer(oldinitprob.f.sys, state_values(oldinitprob), u0idxs, u0vals)
+        end
+        if isempty(pidxs)
+            newp = parameter_values(oldinitprob)
+        else
+            newp = remake_buffer(oldinitprob.f.sys, parameter_values(oldinitprob), pidxs, pvals)
+        end
         initprob = remake(oldinitprob; u0 = newu0, p = newp)
         return initprob, odefn.update_initializeprob!, odefn.initializeprobmap,
         odefn.initializeprobpmap

test/initializationsystem.jl

@@ -877,3 +877,75 @@ end
     sol = solve(prob, Rodas5P())
     @test SciMLBase.successful_retcode(sol)
 end
+
+@testset "Issue#3205" begin
+    using ModelingToolkit
+    using ModelingToolkitStandardLibrary.Electrical
+    using ModelingToolkitStandardLibrary.Mechanical.Rotational
+    using ModelingToolkitStandardLibrary.Blocks
+    using ModelingToolkit: t_nounits as t
+    using SciMLBase
+
+    function dc_motor(R1=0.5)
+        R = R1 # [Ohm] armature resistance
+        L = 4.5e-3 # [H] armature inductance
+        k = 0.5 # [N.m/A] motor constant
+        J = 0.02 # [kg.m²] inertia
+        f = 0.01 # [N.m.s/rad] friction factor
+        tau_L_step = -0.3 # [N.m] amplitude of the load torque step
+
+        @named ground = Ground()
+        @named source = Voltage()
+        @named ref = Blocks.Step(height=0.2, start_time=0)
+        @named pi_controller = Blocks.LimPI(k=1.1, T=0.035, u_max=10, Ta=0.035)
+        @named feedback = Blocks.Feedback()
+        @named R1 = Resistor(R=R)
+        @named L1 = Inductor(L=L)
+        @named emf = EMF(k=k)
+        @named fixed = Fixed()
+        @named load = Torque()
+        @named load_step = Blocks.Step(height=tau_L_step, start_time=3)
+        @named inertia = Inertia(J=J)
+        @named friction = Damper(d=f)
+        @named speed_sensor = SpeedSensor()
+
+        connections = [connect(fixed.flange, emf.support, friction.flange_b)
+            connect(emf.flange, friction.flange_a, inertia.flange_a)
+            connect(inertia.flange_b, load.flange)
+            connect(inertia.flange_b, speed_sensor.flange)
+            connect(load_step.output, load.tau)
+            connect(ref.output, feedback.input1)
+            connect(speed_sensor.w, :y, feedback.input2)
+            connect(feedback.output, pi_controller.err_input)
+            connect(pi_controller.ctr_output, :u, source.V)
+            connect(source.p, R1.p)
+            connect(R1.n, L1.p)
+            connect(L1.n, emf.p)
+            connect(emf.n, source.n, ground.g)]
+
+        @named model = ODESystem(connections, t,
+            systems=[
+                ground,
+                ref,
+                pi_controller,
+                feedback,
+                source,
+                R1,
+                L1,
+                emf,
+                fixed,
+                load,
+                load_step,
+                inertia,
+                friction,
+                speed_sensor
+            ])
+    end
+
+    model = dc_motor()
+    sys = structural_simplify(model)
+
+    prob = ODEProblem(sys, [sys.L1.i => 0.0], (0, 6.0))
+
+    @test_nowarn remake(prob, p=prob.p)
+end