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# Untitled

a guest Feb 19th, 2019 57 Never
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1. deqns = {Subscript[m, 1] x1''[
2.   t] == ([Lambda]1[t]/Subscript[l, 1]) x1[
3.    t] - ([Lambda]2[t]/Subscript[l, 2]) (x2[t] - x1[t]),
4.   Subscript[m, 1] y1''[
5.   t] == ([Lambda]1[t]/Subscript[l, 1]) y1[
6.    t] - ([Lambda]2[t]/Subscript[l, 2]) (y2[t] - y1[t]) -
7.   Subscript[m, 1] g,
8.   Subscript[m, 2] x2''[
9.   t] == ([Lambda]2[t]/Subscript[l, 2]) (x2[t] - x1[t]),
10.   Subscript[m, 2] y2''[
11.   t] == ([Lambda]2[t]/Subscript[l, 2]) (y2[t] - y1[t]) -
12.   Subscript[m, 2] g};
13.
14. aeqns = {x1[t]^2 + y1[t]^2 ==
15.   Subscript[l, 1]^2, (x2[t] - x1[t])^2 + (y2[t] - y1[t])^2 ==
16.   Subscript[l, 2]^2};
17.
18. ics = {x1[0] == 1, y1[0] == 0, y1'[0] == 0, x2[0] == 1, y2[0] == -1,
19.   y2'[0] == 0};
20.
21. params = {g -> 9.81, Subscript[m, 1] -> 1, Subscript[m, 2] -> 1,
22.   Subscript[l, 1] -> 1, Subscript[l, 2] -> 1};
23.
24. soldp = First[
25.   NDSolve[{deqns, aeqns, ics} /. params, {x1, y1, x2,
26.   y2, [Lambda]1, [Lambda]2}, {t, 0, 15000},
27.   Method -> {"IndexReduction" -> {"Pantelides",
28.     "ConstraintMethod" -> "Projection"}}]];
29.
30. SmoothDensityHistogram[
31.   Map[Function[Evaluate[{x2[#], y2[#]} /. soldp]],
32.    Range[0, 15000, 0.025]], Mesh -> 5,
33.   PlotRange -> {{-2, 2}, {-2, 0.1}}]
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