Date: Mar 2, 2013 3:44 AM
Author: Marco Gabiccini
Subject: Strange behavior of System Modeler

Hi all,

I have just started studying WSM and the Modelica language by implementing the simple pendulum model (class) es. described on p.33 of Peter Fritzson's book Introduction to "Modeling and Simulation of Technical and Physical Systems with Modelica". The code (pendulum equation written as a DAE) is:

model DAEExample "DAEExample"
constant Real PI=3.14159265358979;
parameter Real m=1,g=9.81,l=0.5;
output Real F;
output Real x(start=0.5),y(start=0);
output Real vx,vy;
equation
m*der(vx)=-x/l*F;
m*der(vy)=-y/l*F - m*g;
der(x)=vx;
der(y)=vy;
x^2 + y^2=l^2;
end DAEExample;

I run the example in WSM and I get totally meaningless results.
The solver is the default one (DASSL) which, I think, is the right one for handling DAEs.

Any ideas?

Thanks,

Marco

Marco Gabiccini, PhD
Assistant Professor of Applied Mechanics and Robotics
Dept. of Mechanical, Nuclear and Production Engineering
University of Pisa
Via Diotisalvi 2, 56122 Pisa PI
Italy
Phone: +39-050-221.80.77
Fax: +39-050-221.80.65
Homepage: http://www.dimnp.unipi.it/gabiccini-m/