Construction and Simulation of a Simple Model
In this tutorial, we will simulate a very simple model consisting of a generator and a writer as shown in the block diagram shown below.
Model Simulation
Let us construct the model first. See Model Construction for more detailed information about model construction.
using Causal
# Describe the model
@defmodel model begin
@nodes begin
gen = SinewaveGenerator()
writer = Writer()
end
@branches begin
gen => writer
end
endIn this simple model, we have a single output sinusoidal wave generator gen and a writer. In the script above, we constructed the components, connected them together and constructed the model.
We can specify simulation settings such as whether a simulation log file is be to constructed, model components are to be saved in a file, etc.
simdir = "/tmp"
logtofile = true
reportsim = trueAt this point, the model is ready for simulation.
t0 = 0. # Start time
dt = 0.01 # Sampling interval
tf = 10. # Final time
sim = simulate!(model, t0, dt, tf, simdir=simdir, logtofile=logtofile, reportsim=reportsim)Simulation(state:done, retcode:success, path:/tmp/Simulation-edfb5169-79f9-4c73-8440-6f85256ae59c)
Investigation of Simulation
First, let us observe Simulation instance sim. We start with the directory in which all simulation files are saved.
foreach(println, readlines(`ls -al $(sim.path)`))total 128 drwxr-xr-x 2 sari sari 4096 Aug 24 10:44 . drwxrwxrwt 109 root root 77824 Aug 24 10:44 .. -rw-r--r-- 1 sari sari 15236 Aug 24 10:44 63bcbe07-edd1-4dc5-a8fe-75bdb0c91724 -rw-r--r-- 1 sari sari 22051 Aug 24 10:44 report.jld2 -rw-r--r-- 1 sari sari 1061 Aug 24 10:44 simlog.log
The simulation directory includes a log file simlog.log which helps the user monitor simulation steps.
# Print the contents of log file
open(joinpath(sim.path, "simlog.log"), "r") do file
for line in readlines(file)
println(line)
end
end┌ Info: 2020-08-24T10:44:28.509 Started simulation... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.548 Inspecting model... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.564 Done. └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.564 Initializing the model... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.595 Done... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.595 Running the simulation... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.857 Done... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.857 Terminating the simulation... └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5 ┌ Info: 2020-08-24T10:44:28.924 Done. └ @ Causal /home/sari/.julia/dev/Causal/src/utilities/utils.jl:5
report.jld2 file, which includes the information about the simulation and model components, can be read back after the simulation.
julia> using FileIO, JLD2
julia> filecontent = load(joinpath(sim.path, "report.jld2"))
Dict{String,Any} with 9 entries:
"retcode" => :success
"name" => "Simulation-edfb5169-79f9-4c73-8440-6f85256ae59c"
"model/callbacks" => nothing
"model/name" => ""
"model/clock" => Clock(t:10.0, dt:0.01, tf:10.0, paused:false, isrunning:…
"model/id" => "26066427-9dce-41ef-9222-23064309ac83"
"components/" => SinewaveGenerator(amp:1.0, freq:1.0, phase:0.0, offset:0…
"path" => "/tmp/Simulation-edfb5169-79f9-4c73-8440-6f85256ae59c"
"state" => :done
julia> clock = filecontent["model/clock"]
Clock(t:10.0, dt:0.01, tf:10.0, paused:false, isrunning:false)Analysis of Simulation Data
After the simulation, the data saved in simulation data files, i.e. in the files of writers, can be read back any offline data analysis can be performed.
# Read the simulation data
t, x = read(getnode(model, :writer).component)
# Plot the data
using Plots
plot(t, x, xlabel="t", ylabel="x", label="")qt.qpa.screen: QXcbConnection: Could not connect to display Could not connect to any X display. connect: Connection refused GKS: can't connect to GKS socket application GKS: Open failed in routine OPEN_WS GKS: GKS not in proper state. GKS must be either in the state WSOP or WSAC in routine ACTIVATE_WS
A Larger Model Simulation
Consider a larger model whose block diagram is given below
The script below illustrates the construction and simulation of this model
using Causal
using Plots
# Construct the model
@defmodel model begin
@nodes begin
gen1 = SinewaveGenerator(frequency=2.)
gain1 = Gain()
adder1 = Adder(signs=(+,+))
gen2 = SinewaveGenerator(frequency=3.)
adder2 = Adder(signs=(+,+,-))
gain2 = Gain()
writer = Writer()
gain3 = Gain()
end
@branches begin
gen1[1] => gain1[1]
gain1[1] => adder1[1]
adder1[1] => adder2[1]
gen2[1] => adder1[2]
gen2[1] => adder2[2]
adder2[1] => gain2[1]
gain2[1] => writer[1]
gain2[1] => gain3[1]
gain3[1] => adder2[3]
end
end
# Simulation of the model
simulate!(model, withbar=false)
# Reading and plotting the simulation data
t, x = read(getnode(model, :writer).component)
plot(t, x)[ Info: 2020-08-24T10:44:43.576 Started simulation... [ Info: 2020-08-24T10:44:43.576 Inspecting model... ┌ Info: The model has algrebraic loops:[[5, 6, 8]] └ Trying to break these loops... [ Info: Loop [5, 6, 8] is broken [ Info: 2020-08-24T10:44:43.801 Done. [ Info: 2020-08-24T10:44:43.801 Initializing the model... [ Info: 2020-08-24T10:44:44.028 Done... [ Info: 2020-08-24T10:44:44.028 Running the simulation... [ Info: 2020-08-24T10:44:44.31 Done... [ Info: 2020-08-24T10:44:44.31 Terminating the simulation... [ Info: 2020-08-24T10:44:44.361 Done. qt.qpa.screen: QXcbConnection: Could not connect to display Could not connect to any X display. connect: Connection refused GKS: can't connect to GKS socket application GKS: Open failed in routine OPEN_WS GKS: GKS not in proper state. GKS must be either in the state WSOP or WSAC in routine ACTIVATE_WS
