# Connection between two MultiBody SystemModels **URL:** \ **Category:** Questions\ **Tags:** engineering, mathematica, system-modeler\ **Created:** [May 3, 2021, 5:24am UTC](https://community.wolfram.com/t/connection-between-two-multibody-systemmodels/18047 "2021-05-03T05:24:26Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![bogdanudrea](https://avatars.discourse-cdn.com/v4/letter/b/e19b73/32.png) [@bogdanudrea](https://community.wolfram.com/u/bogdanudrea)\ **Post date:** [May 3, 2021, 5:24am UTC](https://community.wolfram.com/t/connection-between-two-multibody-systemmodels/18047/1 "2021-05-03T05:24:26Z")
Dear Colleagues, I am trying to connect a set of SystemModels that I generated programmatically in Mathematica. I am interested in MultiBody models and I haven’t tried other types of models. I am failing gloriously and I have spent a good part of the day reading the online help pages and performing a lot of trial and error. Here’s a simplified example First model called “model1” ``` comp1 = {"c11" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c12" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape"} conn1 = {"c11.frame_b" \[DirectedEdge] "c12.frame_a"} ConnectSystemModelComponents["model1", comp1, conn1, GraphLayout -> None] ``` Second model called “model2” ``` comp2 = {"c21" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c22" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape"} conn2 = {"c21.frame_b" \[DirectedEdge] "c22.frame_a"} ConnectSystemModelComponents["model2", comp2, conn2, GraphLayout -> None] ``` Model’o’models - failure ``` (*"Model" found by trial error. Is it needed, is it correct? At least Mathematica don't complain about it*) compM = {"model1" \[Element] "Model", "model2" \[Element] "Model"} connM = {"model1.c11.frame_a" \[DirectedEdge] "model2.c21.frame_a"} ConnectSystemModelComponents["mdlOfMdls", compM, connM] ``` The error message is > ConnectSystemModelComponents::cnf: Connectors > {model1.c11.frame\_a,model2.c21.frame\_a} are not one of the expected > ones: {}. I have also tried ``` connM = {"c11.frame_a" \[DirectedEdge] "c21.frame_a"} ConnectSystemModelComponents["mdlOfMdls", compM, connM] ``` that gives a similar error message: > ConnectSystemModelComponents::cnf: Connectors > {c11.frame\_a,c21.frame\_a} are not one of the expected ones: {}. According to the Mathematica help page for **ConnectSystemModelComponents** at [https://reference.wolfram.com/language/ref/ConnectSystemModelComponents.html](https://reference.wolfram.com/language/ref/ConnectSystemModelComponents.html) > The compi can be a SystemModel object, a full model name string or a > shortened model name accepted by SystemModel. The error seems to come from the connectors of each model so the question is What type of connectors should I use? Last but not least, I have also tried something a bit more sophisticated by introducing a MultoBody Interface component ``` comp1 = {"c11" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c12" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "if1" \[Element] "Modelica.Mechanics.MultiBody.Interfaces.Frame_a"} conn1 = {"c11.frame_a" \[DirectedEdge] "if1", "c11.frame_b" \[DirectedEdge] "c12.frame_a"} ConnectSystemModelComponents["model1", comp1, conn1] comp2 = {"c21" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c22" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "if2" \[Element] "Modelica.Mechanics.MultiBody.Interfaces.Frame_a"} conn2 = {"c21.frame_a" \[DirectedEdge] "if2", "c21.frame_b" \[DirectedEdge] "c22.frame_a"} ConnectSystemModelComponents["model2", comp2, conn2] compM = {"model1" \[Element] "Model", "model2" \[Element] "Model"} connM = {"model1.if1" \[DirectedEdge] "model2.if2"} ConnectSystemModelComponents["mdlOfMdls", compM, connM] ``` That gives the same type of error. I have posted this question on StackExchange as well. Thank you. B ---
**Author:** ![neils](https://yyz1.discourse-cdn.com/wolfram/user_avatar/community.wolfram.com/neils/32/20595_2.png) [@neils](https://community.wolfram.com/u/neils)\ **Post date:** [May 3, 2021, 7:17am UTC](https://community.wolfram.com/t/connection-between-two-multibody-systemmodels/18047/2 "2021-05-03T07:17:09Z")
Bogdan, You need to have a connector on each of your mode1 and model2 models if you want to connect them together. For example ``` comp1 = {"c11" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c12" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "frame1" \[Element] "Modelica.Mechanics.MultiBody.Interfaces.Frame_a"} conn1 = {"c11.frame_b" \[DirectedEdge] "c12.frame_a", "c11.frame_a" \[DirectedEdge] "frame1"} ConnectSystemModelComponents["model1", comp1, conn1, GraphLayout -> None] comp2 = {"c21" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "c22" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape", "frame2" \[Element] "Modelica.Mechanics.MultiBody.Interfaces.Frame_a"} conn2 = {"c21.frame_b" \[DirectedEdge] "c22.frame_a", "c21.frame_a" \[DirectedEdge] "frame2"} ConnectSystemModelComponents["model2", comp2, conn2, GraphLayout -> None] ``` You can connect them as you tried except your syntax of ``` "model1" \[Element] "Model" ``` makes no sense. You need to name an instance of the models you created: ``` compM = {"aa" \[Element] "model1", "bb" \[Element] "model2"} connM = {"aa.frame1" \[DirectedEdge] "bb.frame2"} ConnectSystemModelComponents["mdlOfMdls", compM, connM] ``` One other note, If you intend to use the multibody elements, you MUST have a World element in the top level model. I hope this helps. Regards, Neil ---
**Author:** ![bogdanudrea](https://avatars.discourse-cdn.com/v4/letter/b/e19b73/32.png) [@bogdanudrea](https://community.wolfram.com/u/bogdanudrea)\ **Post date:** [May 3, 2021, 7:40am UTC](https://community.wolfram.com/t/connection-between-two-multibody-systemmodels/18047/3 "2021-05-03T07:40:40Z")
Neil, Thank you. Yes, it helps. I totally missed the fact that I have to instantiate the models that I created. The World component is at the top and not shown in this example. Best regards, B