Re: [ASCEND] connecting dynamic models in series

[John P. <joh...@an...>]

Hi DFE,

Thanks for your question about dynamic modelling with ASCEND. The 
'ode_id' syntax in ASCEND is something that also causes me annoyance, so 
you will be pleased to know that we have a student, Ksenija, working on 
improved syntax for DAE modelling in ASCEND.
http://ascend4.org/User:Ksenija

Your immediate option here, as a kludge, would be to create the chained 
first-order models in an array, and then to set the ode_id values using 
a FOR loop inside a method. Alternatively, you could set a constant for 
each chained submodel (:== operator) from which you could locally 
calculate the needed ode_id.

Our planned new syntax will eliminate this annoying step, hopefully we 
will have something better by September or so. As well as the new 
syntax, we are working to add generalised event 
handling/reinitialisation for DAE simulations, which will be helpful for 
step and ramp responses, etc. Currently, reinitialisations must be 
handled manually or via methods.

Please let me know if I need to expand on how to go about the suggested 
workaround.

Cheers
JP

On 19/06/12 17:20, Daikokuten Eudaemon wrote:
> Ascendians,
>
> There are two files attached to this message:  dfe_dyn_FO.a4c  and  
> dfe_dyn_FO_FO_InSeries.a4c. The  dfe_dyn_FO.a4c  models a first order 
> plant whereas the  dfe_dyn_FO_FO_InSeries.a4c  models two such plants 
> connected in series. What I find repelling about the  
> dfe_dyn_FO_FO_InSeries.a4c  is the fact that in the "METHOD on_load" 
> it contains the following two lines of code:
>
>     B2.dy_dt.ode_id := 2;
>     B2.y.ode_id := 2;
>
> I have been unable to integrate  dfe_dyn_FO_FO_InSeries.a4c  without 
> these two lines cited above. IMHO, this is just a kludge as these two 
> unfortunate lines simply manually coerce the dynamics of each of the 
> two first order plants into one system. Is there a more elegant way to 
> connect two (not to mention two hundred twenty two, for example)  
> dfe_dyn_FO.a4c  in series?
>
> Regards,
> DFE
>
>
>
>
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