Constraints

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1

Hi,
I have a seated human model, It has 372 DOF, the constraints are 388 and active reactions are 314…Anyway, when I run the model and at the initialconditions stage I got the message below (even if the number of the constraints and the DOF are the same).

WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 432 independent constraints and 434 unknowns

  • attemps to continue (attempt no. 1)
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 5 unsolvable constraint(s) found
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 432 independent constraints and 434 unknowns

  • attemps to continue (attempt no. 2)
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 5 unsolvable constraint(s) found
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 432 independent constraints and 434 unknowns

  • attemps to continue (attempt no. 3)
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 2 unsolvable constraint(s) found
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 432 independent constraints and 434 unknowns

  • attemps to continue (attempt no. 4)
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 5 unsolvable constraint(s) found
    WARNING(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed : 432 independent constraints and 434 unknowns

  • attemps to continue (attempt no. 5)
    ERROR(OBJ.MCH.KIN1) : C:/Doc…ngs/a…1/D…p/D…l/Model.any : Study : Model is kinematically indeterminate : Position analysis failed

I tried to find out and solve this problem but nothing changed… so could you explain to me what does this exactly mean? what is exactly the problem?
how should I solve the problem? :slight_smile:

thank you in advance.

Regards,
Zayd

2

Hi Zayd,

There can be many reasons why the model does not solve kinematically.

The error message suggest that you are missing 2 drivers.

Usually would do the following:

[ol]
[li]out-comment the human part of the model and make sure the chair runs by itself.
[/li][li]replace all your human drivers by a set of jointdrivers taken from the freeposture model
[/li][li]make sure this model runs
[/li][li]swicth one driver at the time back to the original one and remove the joint driver that it replace, make sure to always have the model running.
[/li][/ol]

Please also note that it is not just the number of added constraints which count they must also be independent, you can not have two drivers that drive the same dof in the model.

Best regards
Søren

Best regards
Søren