Replacing Connect-Statement by equations???, I´m trying to understand Modelica ;-)
 RungeZipperer Jun 15 2009, 02:29 PM Post #1 Advanced Member Group: Members Posts: 59 Joined: 14-March 06 Member No.: 4 QUOTE(Roland @ Jun 15 2009, 02:39 PM) Therefore you can not connect the tau by hand.I should have known that. Thanks!QUOTE(Roland @ Jun 15 2009, 02:39 PM) Why? I can see no reason why you would have to avoid the connect statement.I´m trying to find a way to build a variable structure system. As far as I know this is not possible with Modelica at present. I just wanted to experiment with the language to go more into detail.
 Roland Jun 15 2009, 12:39 PM Post #2 Advanced Member Group: Members Posts: 30 Joined: 2-January 08 Member No.: 5,272 Hello RungeZipperer,QUOTE(RungeZipperer @ Jun 12 2009, 07:18 AM) What is so special about the connection?The connector "Modelica.Mechanics.Rotational.Interfaces.Flange_x" has the flow variable "tau" as member. In Modelica the sum of the flow variables of all connected connectors is automatically set to 0. In your case, the equation isCODEconstantTorque.flange.tau + inertia.flange_a.tau = 0;If you do not use the connect statement the sum is still set to 0 - the difference is just, that there is only one variable in the equation. E.g.:CODEconstantTorque1.flange.tau = 0;Therefore you can not connect the tau by hand.QUOTE(RungeZipperer @ Jun 12 2009, 07:18 AM) There must be a way to write equations instead of connect()!?Why? I can see no reason why you would have to avoid the connect statement.Regards,Roland
 RungeZipperer Jun 12 2009, 06:18 AM Post #3 Advanced Member Group: Members Posts: 59 Joined: 14-March 06 Member No.: 4 Hello,I´m just trying to understand some very basic characteristics of Modelica (and also Dymola). This is my first question (out of a few...):Look at this example. There is a constant torque connected to a inertia. I´ve used the connect(constantTorque.flange, inertia.flange_a) for the model on top and then I wanted to replace this by constantTorque1.flange.phi=inertia1.flange_a.phi; constantTorque1.flange.tau+inertia1.flange_a.tau=0;which is not possible. I can leave out one of these equations but I still get the error that "The Real part has 26 unknowns and 27 equations." What is so special about the connection? There must be a way to write equations instead of connect()!?Can you give me some hints?CODEmodel ConnectTest     annotation (Diagram);  Modelica.Mechanics.Rotational.Inertia inertia    annotation (extent=[0,50; 20,70]);  Modelica.Mechanics.Rotational.ConstantTorque constantTorque    annotation (extent=[-40,50; -20,70]);  Modelica.Mechanics.Rotational.Inertia inertia1    annotation (extent=[0,-20; 20,0]);  Modelica.Mechanics.Rotational.ConstantTorque constantTorque1    annotation (extent=[-40,-20; -20,0]);equation   connect(constantTorque.flange, inertia.flange_a)    annotation (points=[-20,60; 0,60], style(color=0, rgbcolor={0,0,0}));  constantTorque1.flange.phi=inertia1.flange_a.phi;//  constantTorque1.flange.tau+inertia1.flange_a.tau=0;end ConnectTest; Attached File(s)  ConnectTestTotal.mo ( 46.38k ) Number of downloads: 742

2 User(s) are reading this topic (2 Guests and 0 Anonymous Users)
0 Members:

 Lo-Fi Version Time is now: 20th June 2019 - 01:36 PM