Hello,

In OpenModelica System Documentation Version 2009-11-09 for OpenModelica 1.5 figure 1.2 shows Translation stages from Modelica code to executing simulation. What is the difference between the jobs of Analyzer and Optimizer? More specifically, optimization, I understand, but what is meant by sorted equations?

Regards,
AC.

Thanks Frenkel TUD for your answers. My problem with $DER is that I want to use the description generated by Modelica optimizer from a C programing environment where I will use the variables generated by Modelica as the variables and there the '$' sign though being a just a silly prefix for a variable will create problem if used in a variable name.

Regards,
AC.

I am sorry if my question appears silly. Can I choose library/libraries in such a way as there will not be $DER terms? Till now I am selecting the whole 'Modelica' library while executing 'bltdump'. The command I am using is 'omc +s +d=bltdump filename.mo Modelica'. But in case of describing & optimizing linear electrical circuits is there any alternative/specific libraries using which the description may not be minimal state but will not contain $DER terms?

Regards,
AC.

I can give an example for my question. Suppose I have an R-L series circuit excited with a voltage source. One of the circuit eqns can be:

V=R*i+L*der(i), where i being the inductor current is a state variable. That case state variable 'i' is inside der( )  and also in normal form(with R) in the same eqn.

Or,the other way of writing this can be something like:

V1=R*i
V2=L*der(i)
V=V1+V2

So here 'i' is present in der in one eqn & in other eqn it is in its normal form(with R).

I have chosen R-L circuit just to describe the situation. My question is can I be assured that the optimizer will always take the first or the second way in case of any linear circuit? Or can I control the optimizer (by some command line parameters or some other way) to go for either of the two ways? Presence of state variable in the left hand side or right hand side of the equation in 'der' form or in normal form is not an issue for me now.

Regards,
AC.

Hello,

When we optimize a set of flattened equations using 'bltdump' command is it possible that for a linear electrical circuit, an optimized sorted equation can contain the same variable(say an inductor current or a capacitor voltage) both in normal form and inside derivative? I did not find it so. But I need the information for further processing of the set of equations.

Regards,
AC.

Hello,

While optimizing a set of flattened equations(generated from a linear electrical circuit of 4 capacitors in series with a sinusoidal voltage source), along with 'der( )' I got '$DER' in variable list. The variable list shows it is a 'DUMMY_DER'. What is its significance? Is it possible to predict from a circuit(linear) whether its optimized form will contain '$DER' in its variable list or not?

Regards,
AC

Hello,

While optimizing a set of flattened equations(generated from a linear electrical circuit of 4 capacitors in series with a sinusoidal voltage source), along with 'der( )' I got '$DER' in variable list. The variable list shows it is a 'DUMMY_DER'. What is its significance? Is it possible to predict from a circuit(linear) whether its optimized form will contain '$DER' in its variable list or not?

Regards,
AC

Hello,

When we optimize a set of flattened equations using 'bltdump' command is it possible that for a linear electrical circuit, an optimized sorted equation can contain the same variable(say an inductor current or a capacitor voltage) both in normal form and inside derivative? I did not find it so. But I need the information for further processing of the set of equations.

Regards,
AC.

Hello,

I am able to generate optimize sorted equations from a circuit description in .mo file by the command ".omc +s +d=bltdump filename.mo Modelica". But in the equations the coefficient values are not put. Can anyone tell me how to get the same set of equations(optimized, sorted) with the coefficient values(e.g, values of resistor, capacitor etc in an electrical circuit)?

Regards,
AC.

Hello,

Can I use OpenModelica to linearize a non linear circuits considering the fact that the operating point in question is such as the non linearity is not in a great extent? (Such as the current through a diode is high enough so that the Q point is far away from the X-axis ; so the non linearity is less; and there the diode can be replaced by a series resistance and a voltage source)

Regards,
Arka.

Thanks sjoelund.se, it works!!

Regards,
Arka.

Thanks sjoelund.se. From the command prompt in Windows I am able to invoke the omc (by command "omc") without using the OM shell, even I can flatten the code using the command  "omc circuit.mo Modelica".I have kept the circuit.mo file in the path ''C:\OpenModelica1.5.0\bin". But the command "omc +d=bltdump circuit.mo Modelica" again gives me the flattened equations. But I want the optimized sorted set of equations (after BLT transformation). Please indicate my mistake. May be I am missing some silly point.

Regards,
Arka

Thanks Adrian for the prompt reply. But the output that I am getting after this command is:

>> ./omc +d=bltdump circuit.mo
[1:1]: error: unexpected token: ./

Can anyone please tell how to tackle it?

Thanks,
Arka.

Hello,

By the command 'instantiateModel', it is possible to look at the flattened model after the translator stage. Like that is it possible by any command or by any other means to view the system description after the optimizer stage? I want to look at the optimized sorted equation of a model. Is it possible?

Regards,
Arka.