| 1 | model DoubleMassVecLen |
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| 2 | import Modelica.Math.Vectors; |
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| 3 | |
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| 4 | Real[3] x1(start = {0, 0, 0}, each fixed = true); |
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| 5 | Real[3] x2(start = {len, 0, 0}, fixed = {true, true, false}); |
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| 6 | Real[3] v1(each start = 0, fixed = {true, true, true}); |
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| 7 | Real[3] v2(each start = 0, fixed = {true, true, false}); |
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| 8 | Real[3] fApplied1 = {0.0, 2.0, 0.0}, fApplied2 = {0.0, -2.0, 0.0}; |
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| 9 | Real fInternal (start = 0, fixed = false); |
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| 10 | Real[3] fInternalVec; |
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| 11 | Real[3] x1x2Unit; // Unit vector from x1 to x2 |
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| 12 | parameter Real m1 = 0.8, m2 = 1.2, len =2.5; |
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| 13 | Real lengthCheck; |
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| 14 | equation |
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| 15 | // Basic ODE |
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| 16 | der(x1) = v1; |
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| 17 | der(x2) = v2; |
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| 18 | der(v1) = (fApplied1 - fInternalVec) / m1; |
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| 19 | der(v2) = (fApplied2 + fInternalVec) / m2; |
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| 20 | fInternalVec = x1x2Unit * fInternal; |
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| 21 | |
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| 22 | // Computation of constraint information |
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| 23 | x1x2Unit = Vectors.normalize(x2 - x1); // Unit vector from x1 to x2 |
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| 24 | Vectors.length(x1 - x2) = len; |
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| 25 | lengthCheck = Vectors.length(x1 - x2); |
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| 26 | annotation(experiment(StartTime = 0, StopTime = 5, Tolerance = 1e-06, Interval = 0.006)); |
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| 27 | end DoubleMassVecLen; |
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