[MBDyn-users] total pin joint with angular velocity constraint

MBDyn users list mbdyn-users at mbdyn.org
Wed May 27 23:32:07 CEST 2020


Hello;

I am writing code for an MBDyn preprocessor for FreeCAD.  I am trying to
make a simulation for a slide crank usng total joints.  A picture of it is
here.

 https://github.com/mfasano727/MBDynFCwb/blob/media/screenshots/slidecrank.JPG

the input text is below. The error I get is

"Initial derivative failed because no pivot element could be found for
column 42 (TotalPinJoint(1): dof(6) Mz) aborting..."

Total pin joint 1 is for the crank.  I was trying to get it to revolve.  I
guess I am not applying the angular velocity keyword in the constraint
properly.  I hope you can help.

Thanks.


begin: data;
        problem: initial value;
end: data;

begin: initial value;
        initial time: 0.0;
        final time: 40.0;
        time step: 0.25;
        tolerance: 0.001;
        max iterations: 10;
        derivatives tolerance: 0.0;
end: initial value;

begin: control data;
        structural nodes: 3;
        joints: 4;
        rigid bodies: 3;
end: control data;

begin: nodes;
        structural: 1, dynamic,
                21.0, 9e-16, 2.6e-15,
                euler321, 0.0, 0.0,0.0,
                null,
                null;
        structural: 2, dynamic,
                88.0, -9e-16, 1.9e-15,
                euler321, 0.0, 0.0,0.0,
                null,
                null;
        structural: 3, dynamic,
                143.132543069545, -2.7e-15, 5.4e-15,
                euler321, 0.0, 0.0,0.0,
                null,
                null;
end: nodes;

begin: elements;
        body: 1, 1,
                23.036504591506368,
                null,
                diag, 253.25808965653337, 4544.629268369435,
4387.356614510845;
        body: 2, 2,
                48.036504591506336,
                null,
                diag, 513.6747563231997, 37922.441125809266,
37608.91847195068;
        body: 3, 3,
                44.91150459150636,
                null,
                diag, 1857.8165377775254, 3084.0319584803906,
3190.171919409456;
        joint: 1, total pin joint,
                1,
                        position, -21.0, -9e-16, -2.6e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                    position, null,
                    position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0, 1.0,
0.0,
                    rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0, 1.0,
0.0,
                position constraint,  active, active, active, null,
                orientation constraint,  active, angular velocity, active,
0., 1., 0., const, 1.;

        joint: 2, total joint,
                1,
                        position, 21.0, -9e-16, -2.6e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                2,
                        position, -46.0, 9e-16, -1.9e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                position constraint,  active, active, active, null,
                orientation constraint,  active, inactive, active, null;

        joint: 3, total joint,
                2,
                        position, 46.0, 9e-16, -1.9e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                3,
                        position, -9.132543069544994, 2.7e-15, -5.4e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                position constraint,  active, active, active, null,
                orientation constraint,  active, inactive, active, null;

        joint: 4, total pin joint,
                3,
                        position, -9.132543069544994, 2.7e-15, -5.4e-15,
                        position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                        rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0,
1.0, 0.0,
                    position, null,
                    position orientation, 1, 1.0, 0.0, 0.0,  2, 0.0, 1.0,
0.0,
                    rotation orientation, 1, 1.0, 0.0, 0.0,  2, 0.0, 1.0,
0.0,
                position constraint,  inactive, active, active, null,
                orientation constraint,  active, active, active, null;

end: elements;




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