Constraint reduction for dynamic simulation

A non-transitory computer storage device encoded with a computer program, the computer program comprising instructions that when executed by data processing apparatus perform operations comprising:

• translating kinematic information from a kinematic model into dynamic information for a dynamic model, the dynamic information defining degree of freedom relationships at one or more joints where a plurality of bodies connect, wherein translating comprises;
• identifying a first plurality of bodies in a mechanical model including at least one grounded body and at least one free body, each of the bodies in the first plurality of bodies being related to at least one other body in the plurality of bodies by at least one constraint that removes or limits at least one degree of freedom for that body in relation to another body;
• merging the bodies in the first plurality of bodies into a minimum number of rigid groups needed for a dynamic simulation where the minimum number of rigid groups includes at least one grounded group and at least one mobile group, including;
• grounding a first body in the plurality of bodies;
• solving constraints between the first body and a second moving body in the plurality of bodies, wherein solving constraints comprises determining how many degrees of freedom the second body has and how the second body can move without violating constraints, and wherein solving constraints includes determining that the second body has zero degrees of freedom or that the second body's degrees of freedom are superfluous;
• and
• responsive to determining that the second body has zero degrees of freedom or that the second body's degrees of freedom are superfluous, merging the first body and the second body;
• and
• removing constraints that relate bodies within a group from each of the rigid groups;
• and
• performing a dynamic simulation including applying one or more loads and one or more motion histories to the dynamic model.

A system comprising:

• a display for presenting a target display window to a user;
• one or more user interfaces configured to receive input from the user;
• and
• data processing apparatus operable to perform operations comprising:
• translating kinematic information from a kinematic model into dynamic information for a dynamic model, the dynamic information defining degree of freedom relationships at one or more joints where a plurality of bodies connect, wherein translating comprises:
• identifying a first plurality of bodies in a mechanical model including at least one grounded body and at least one free body, each of the bodies in the first plurality of bodies being related to at least one other body in the plurality of bodies by at least one constraint that removes or limits at least one degree of freedom for that body in relation to another body;
• merging the bodies in the first plurality of bodies into a minimum number of rigid groups needed for a dynamic simulation where the minimum number of rigid groups includes at least one grounded group and at least one mobile group, including:
• grounding a first body in the plurality of bodies;
• solving constraints between the first body and a second moving body in the plurality of bodies, wherein solving constraints comprises determining how many degrees of freedom the second body has and how the second body can move without violating constraints, and wherein solving constraints includes determining that the second body has zero degrees of freedom or that the second body's degrees of freedom are superfluous;
• and
• responsive to determining that the second body has zero degrees of freedom or that the second body's degrees of freedom are superfluous, merging the first body and the second body;
• and
• removing constraints that relate bodies within a group from each of the rigid groups;
• and
• performing a dynamic simulation including applying one or more loads and one or more motion histories to the dynamic model.