Getting error in full vehicle MBD simulation

Sudip_Chavan
Sudip_Chavan Altair Community Member
edited March 28 in Community Q&A

Greetings,

I've developed separate models for the front and rear suspensions of a half car, and successfully simulated each for KnC analysis individually. However, upon merging both models for a full vehicle simulation, the solver fails to find an equilibrium position at rest.

I've meticulously checked the positioning of the road reference markers relative to the tire entities, as well as verified the placement of all other markers involved in the wheel assembly. Despite confirming their correct placement, the solver still struggles to achieve equilibrium in the static position.

Attached are the log file and snapshots from the static simulation for your review.

 

Thanks and Regards,

Sudip Chavan

 

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Answers

  • GTT Adam
    GTT Adam
    Altair Employee
    edited March 28

    Hi Sudip,

    Based on the images shared, your model looks to have some connection issues. I would assume this may be from how you stitched these front and rear models together.

    I would recommend you try a new simulation where you simplify the model to isolate what may be causing the issue. One debug simulation I use frequently is one where you remove all of the driving elements (Driver model, FMU's, even autotires) to confirm the model assembly. Tip: make a copy of your parent model first before starting to strip away entities! I would then create a fixed joint to hold your chassis to ground and simulate the suspension sagging under gravity. I typically run this as a transient simulation so I can watch as the model may unravel. If the vehicle stays together and the suspension sags as expected, then the static simulation you are facing may be due to how you implemented the driving elements. Since this is a half+half model, I'm assuming you manually added the driver model and event into the assembly, so if the debug simulation works then we can isolate the issue to how you may have added in the driving elements. Please give this debug simulation a try and let me know how it turns out.

     

    Hope this helps!

    Adam Reid

  • Praful
    Praful
    Altair Employee
    edited March 28
    Adam Reid_21142 said:

    Hi Sudip,

    Based on the images shared, your model looks to have some connection issues. I would assume this may be from how you stitched these front and rear models together.

    I would recommend you try a new simulation where you simplify the model to isolate what may be causing the issue. One debug simulation I use frequently is one where you remove all of the driving elements (Driver model, FMU's, even autotires) to confirm the model assembly. Tip: make a copy of your parent model first before starting to strip away entities! I would then create a fixed joint to hold your chassis to ground and simulate the suspension sagging under gravity. I typically run this as a transient simulation so I can watch as the model may unravel. If the vehicle stays together and the suspension sags as expected, then the static simulation you are facing may be due to how you implemented the driving elements. Since this is a half+half model, I'm assuming you manually added the driver model and event into the assembly, so if the debug simulation works then we can isolate the issue to how you may have added in the driving elements. Please give this debug simulation a try and let me know how it turns out.

     

    Hope this helps!

    Adam Reid

    One typical mistake I have seen related to connections when merging front and rear suspension systems (usually the rear) the spring and the damper system attachment may refer to the wrong side bodies.

    e.g. the rear springs and dampers may refer to the front bodies such as subframe or knuckle instead of the rear.

    Could you check these systems and see if you find something odd. ?

    regards

    praful

  • Sudip_Chavan
    Sudip_Chavan Altair Community Member
    edited March 28
    Adam Reid_21142 said:

    Hi Sudip,

    Based on the images shared, your model looks to have some connection issues. I would assume this may be from how you stitched these front and rear models together.

    I would recommend you try a new simulation where you simplify the model to isolate what may be causing the issue. One debug simulation I use frequently is one where you remove all of the driving elements (Driver model, FMU's, even autotires) to confirm the model assembly. Tip: make a copy of your parent model first before starting to strip away entities! I would then create a fixed joint to hold your chassis to ground and simulate the suspension sagging under gravity. I typically run this as a transient simulation so I can watch as the model may unravel. If the vehicle stays together and the suspension sags as expected, then the static simulation you are facing may be due to how you implemented the driving elements. Since this is a half+half model, I'm assuming you manually added the driver model and event into the assembly, so if the debug simulation works then we can isolate the issue to how you may have added in the driving elements. Please give this debug simulation a try and let me know how it turns out.

     

    Hope this helps!

    Adam Reid

    Thanks a lot!
    I will give it a try and will let you know.

     

     

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