Motion singularity in simulink

in simulink(simmech) I run my 6-link robot. this error appears: "The motion is singular (the mass matrix is singular). Check the mass properties and joint axes of the attached bodies." apparently my mass matrices are correct. mass of each link is "1" and inertia matrices are "eye(3)"

where does this error come from?

thank you in advance

Answer 1

[Guy Rouleau]

It is not the mass on each joint, but the configuration of the system. For example, a serial manipulator can get into a singular configuration when the axis of 2 revolutes are superposed.

Most robotics books explain this phenomenon.

This solution might help:

http://www.mathworks.com/support/solutions/en/data/1-2HCY5Z/index.html

[Siavash]

Thank you very much Guy, but I don't think this can be my problem.

I have simulated this motion in other simulation softwares, it didn't neither become singular in it nor it looks like a position in which it can become singular.

When I faced this error one thing that I tried was changing the Initial Conditions from zero...that did not work either

[Guy Rouleau]

In that case, I don't have enough information to guess anything else... I would need to see the model.