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

Model Simulation

We construct an empty model and then add nodes and branches to model. See Construction of Models for more detailed information about model construction.

using Jusdl

# Construction of an empty model
t0 = 0.     # Start time
dt = 0.01   # Sampling interval
tf = 10.    # Final time
model = Model(clock=Clock(t0, dt, tf))

# Adding nodes to model
addnode!(model, SinewaveGenerator(), label=:gen)
addnode!(model, Writer(), label=:writer)

# Adding branches to model
addbranch!(model, :gen => :writer)

In 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.

In addition to simulation time settings(which have set through model clock during the model construction above), 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 = true

At this point, the model is ready for simulation.

sim = simulate!(model, simdir=simdir, logtofile=logtofile, reportsim=reportsim)
Simulation(state:done, retcode:success, path:/tmp/Simulation-0f38c6bc-b5bb-4d6d-ac7f-511227a46371)

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 10568
drwxr-xr-x 2 sari sari     4096 May  8 01:34 .
drwxrwxrwt 1 root root 10764288 May  8 01:34 ..
-rw-r--r-- 1 sari sari    15236 May  8 01:34 c3268c39-7fb8-4830-8afb-d91057476abe.jld2
-rw-r--r-- 1 sari sari    21831 May  8 01:34 report.jld2
-rw-r--r-- 1 sari sari     1043 May  8 01:34 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: 2020-05-08T01:34:32.064 Started simulation...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.096 Inspecting model...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.096 Done.
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.096 Initializing the model...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.137 Done...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.138 Running the simulation...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.229 Done...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.229 Terminating the simulation...
└ @ Jusdl /home/sari/.julia/dev/Jusdl/src/utilities/utils.jl:5
┌ Info: 2020-05-08T01:34:32.248 Done.
└ @ Jusdl /home/sari/.julia/dev/Jusdl/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-0f38c6bc-b5bb-4d6d-ac7f-511227a46371"
  "model/callbacks" => nothing
  "model/name"      => ""
  "model/clock"     => Clock(t:10.0, dt:0.01, tf:10.0, paused:false, isrunning:…
  "model/id"        => "02e290a5-bbeb-4ea4-89f9-091309ec84f0"
  "components/"     => SinewaveGenerator(amp:1.0, freq:1.0, phase:0.0, offset:0…
  "path"            => "/tmp/Simulation-0f38c6bc-b5bb-4d6d-ac7f-511227a46371"
  "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="")

A Larger Model Simulation

Consider a larger model whose block diagram is given below

model

The script below illustrates the construction and simulation of this model

using Jusdl
using Plots

# Construction of the model
model = Model()
addnode!(model, SinewaveGenerator(frequency=2), label=:gen1)
addnode!(model, Gain(gain=1), label=:gain1)
addnode!(model, Adder((+,+)), label=:adder1)
addnode!(model, SinewaveGenerator(frequency=3), label=:gen2)
addnode!(model, Adder((+, +, -)), label=:adder2)
addnode!(model, Gain(gain=1), label=:gain2)
addnode!(model, Writer(), label=:writer)
addnode!(model, Gain(gain=1), label=:gain3)
addbranch!(model, :gen1 => :gain1, 1 => 1)
addbranch!(model, :gain1 => :adder1, 1 => 1)
addbranch!(model, :adder1 => :adder2, 1 => 1)
addbranch!(model, :gen2 => :adder1, 1 => 2)
addbranch!(model, :gen2 => :adder2, 1 => 2)
addbranch!(model, :adder2 => :gain2, 1 => 1)
addbranch!(model, :gain2 => :writer, 1 => 1)
addbranch!(model, :gain2 => :gain3, 1 => 1)
addbranch!(model, :gain3 => :adder2, 1 => 3)

# 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: 2020-05-08T01:34:46.524 Started simulation...
[ Info: 2020-05-08T01:34:46.524 Inspecting model...
┌ Info: 	The model has algrebraic loops:[[5, 6, 8]]
└ 		Trying to break these loops...
[ Info: 	Loop [5, 6, 8] is broken
[ Info: 2020-05-08T01:34:46.684 Done.
[ Info: 2020-05-08T01:34:46.684 Initializing the model...
[ Info: 2020-05-08T01:34:46.879 Done...
[ Info: 2020-05-08T01:34:46.879 Running the simulation...
[ Info: 2020-05-08T01:34:47.143 Done...
[ Info: 2020-05-08T01:34:47.143 Terminating the simulation...
[ Info: 2020-05-08T01:34:47.146 Done.