hexaeder / blocksystems.jl Goto Github PK

if the removed superflous state equations contain explicit algebraic states in their rhs this will throw an error

Newbie to this library. I'm wondering if there's a way to define the transfer function of a second order harmonic oscillator using this library?

• shorter output for very big systems
• prob. overload show(io::IO, ::MIME"text/plain", ::T)

Hey,

When I calculate the derivative of an input i(t) BlockSystem automatically reduces the derivative idi(t). I think we should have a look at this! I have set up an MWE, which simply contains a block that squares the input and a derivative block:

using Pkg
Pkg.activate(@__DIR__)

using ModelingToolkit
using BlockSystems

@parameters t
dt = Differential(t)

@parameters x(t) i(t)
@variables x2(t) o(t) ii(t) idi(t)

square_block = IOBlock([x2 ~ x^2], [x], [x2], name = :square_block) 
derivative_block = IOBlock([o ~ idi, ii ~ i, dt(ii) ~ idi], [i], [o, idi, ii], name = :derivative_block)

test = IOSystem([square_block.x2 => derivative_block.i], 
                [square_block, derivative_block],
                outputs=[derivative_block.o], 
                name = :test)

connect_system(test, verbose=true)

This results in the following error. The internal states are incorrectly reduced which you can quickly see in the debugger.

ERROR: ArgumentError: inputs must be parameters
  (Set(inputs) ⊆ Set(parameters(odes))) == false
   ├ (Set(inputs)) = Set(Term{Real, Base.ImmutableDict{DataType, Any}}[x(t)])
   └ (Set(parameters(odes))) = Set{Any}()

But there is a workaround by explicitly using the derivative idi(t) and the internal state ii(t) so that it is not reduced. It works but becomes very messy once the IOSystem becomes bigger!

test = IOSystem([square_block.x2 => derivative_block.i], 
                [square_block, derivative_block],
                outputs=[derivative_block.o, derivative_block.idi, derivative_block.ii], 
                name = :test)

This issue is used to trigger TagBot; feel free to unsubscribe.

If you haven't already, you should update your TagBot.yml to include issue comment triggers.
Please see this post on Discourse for instructions and more details.

If you'd like for me to do this for you, comment TagBot fix on this issue.
I'll open a PR within a few hours, please be patient!