Open
Description
Here is the full code to reproduce the error with @discrete_events not being able to see connector variables.
using ModelingToolkit, Plots, OrdinaryDiffEq
using ModelingToolkit: t_nounits as t, D_nounits as D
@connector Stream begin
q(t)
c_A(t)
c_B(t)
c_C(t)
end
@mtkmodel Influent begin
@components begin
out = Stream()
end
@parameters begin
qin = 4.0
c_Ain = 1.15
c_Bin = 0.3
c_Cin = 0.0
end
@equations begin
out.q ~ qin
out.c_A ~ c_Ain
out.c_B ~ c_Bin
out.c_C ~ c_Cin
end
end
@mtkmodel Effluent begin
@components begin
in = Stream()
end
@variables begin
q(t)
c_A(t)
c_B(t)
c_C(t)
end
@equations begin
q ~ in.q
c_A ~ in.c_A
c_B ~ in.c_B
c_C ~ in.c_C
end
end
@mtkmodel CSTR begin
@components begin
in1 = Stream()
in2 = Stream()
out = Stream()
readingsOut = Stream()
end
@variables begin
q(t)
c_A(t) = 0
c_B(t) = 0
c_C(t) = 0
end
@parameters begin
k = 0.01
V = 1000.0
end
begin
k_La = 500/6*atan(0.02*in2.q)
end
@equations begin
D(c_A) ~ in1.q/V*(in1.c_A - c_A) - k*c_A*c_B
D(c_B) ~ in1.q/V*(in1.c_B - c_B) - k*c_A*c_B + k_La/V*(in2.c_B - c_B)
D(c_C) ~ in1.q/V*(in1.c_C - c_C) + k*c_A*c_B
out.q ~ in1.q
out.c_A ~ c_A
out.c_B ~ c_B
out.c_C ~ c_C
readingsOut.c_B ~ c_B
end
end
@mtkmodel PI_Control_Valve begin
@components begin
readingsIn = Stream()
out = Stream()
end
@variables begin
I_err(t) = 0
u(t) = 0
# B(t) = 0 # Trying intermediate variable, doesn't work
end
@parameters begin
c_BSP = 0.32
K_b = 0.0
K_c = 9.0
K_I = 0.18
eventStart = 200
eventInterval = 30
s = 0 # No initial signal to open valve
τ_p = 5.25
c_Bmax = 0.61
end
@equations begin
D(I_err) ~ c_BSP - readingsIn.c_B
D(u) ~ (s - u)/τ_p
out.q ~ 10*u
out.c_B ~ c_Bmax
# B ~ readingsIn.c_B # Discrete events still can't see this variable
# D(B) ~ 0 # Discrete events can only see B if I do this, but then I can't do `B ~ readingsIn.c_B`
end
@continuous_events begin
[u ~ 1] => [s ~ u]
end
@discrete_events begin
(u > 1-1e-13) => [u ~ 1-1e-13]
# Discrete events can't see readingsIn.c_B or B
# If you replace readingsIn.c_B here with a number (1 for example), the code runs with no errors
((mod(t-eventStart,eventInterval) == 0) & (t >= eventStart)) => [s ~ K_b + K_c*(c_BSP - readingsIn.c_B) + K_I*I_err]
end
end
@mtkmodel CSTR_Model begin
@components begin
influent = Influent()
effluent = Effluent()
cstr = CSTR()
pi_control_valve = PI_Control_Valve()
end
@equations begin
connect(influent.out, cstr.in1)
connect(cstr.out, effluent.in)
connect(cstr.readingsOut, pi_control_valve.readingsIn)
connect(pi_control_valve.out, cstr.in2)
end
end
@mtkbuild cstr_Model = CSTR_Model()
prob = ODEProblem(cstr_Model, [], (0,2000), [])
# ERROR: UndefVarError: `pi_control_valve₊readingsIn₊c_B` not defined
sol = solve(prob, Tsit5(), tstops = [200:30:2000;])
plot(
sol.t, vcat(sol[1:3,:],sol[5,:]')',
title = "Concentration & Valve Pos. vs Time",
yaxis = ("Concentration (mol/L)",(0,1.01)),
xaxis = ("Time (min)",(0,2000*1.01)),
label = ["c_A" "c_B" "c_C" "u"]
)
Everything runs properly until you get to solve(), where you get the error message ERROR: UndefVarError: 'pi_control_valve₊readingsIn₊c_B' not defined. You can replace the readingsIn.c_B under @discrete_events with a number and the problem can be solved, so we know this is the issue.