Could you help me AnyBody S/W?

Kinematic analysis failed in time step 0 : Failed to solve position constriants

Nice to meet you sir,

I make a model that inserted hip implant that dual mobility cup

I think, I should implement two joint. one is normal hip joint other is mobility joint(implant)

so, I made sag, joint, driver but, problem happened

when I load model than occur error "Reference of class AnySphericalJoint cannot refer to an object of class AnyKinLinear Evaluating constants.."

and when I Run inverse dynamics than occur "Kinematic analysis failed in time step 0 : Failed to solve position constriants" error

I don't know what I have to Fix and why this errors are occured

Hi Weedeng,

It seems like you are trying to refer to an AnyKinLinear as an AnySphericalJoint. When you see this error while loading the model, you should also get a link to the lines in the code where this problem is coming from. Could you please copy the line and a few lines above and below so we can see what exactly you have done?

Best regards

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Sir dschander

Hi thank for answer my question. I make squat model what implanted component on hip. start explain my model

first, load implant (femur implant, hip implant, mobile implant)

and change joint in โ€œhipexchange.anyโ€ for make new hip joint and driver


Conventional model has no problem. it just do exchange body, add two implant and connect both node using exist joint. conventional model use same joint with intact AMMR

Intact model = pelvis <-> femur connected
conventional implant model = pelvis implant <-> femur implant connected
the model I want to make = pelvis implant <-> mobile implant <-> femur implant

so, there need one more joint(for insert mobile implant). and behavior of mobile joint is all DOF unlocked, the motion is determined by the contact condition.

I was make Sag for mobile implant, and made two joint that connect femur implant-mobile implant and mobile implant-pelvis implant. but it dosenโ€™t work well

can you tell me where I have to fix and how I fix? Plz

Same problem here๏ผ

Here is my model,

and I got this error!

Since there is no marker on the mobile linear, the kinematics analysis failed. I was wondering if is there some way to solve this.

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Hi Sir. Did you success analysis brfore use marker? And do you make joint in dual mobility? if you did can you help me?

Hi Weedeng,

I am stuck here for a whole month, still trying to figure out the way to do that. But I'll keep in touch.

Best regards

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Ok. If I get how solve this problem I will tell you


It's a rather challenging model to do. AnyBody is an inverse dynamics modeling system and we generally solve for loads knowing kinematics. In your case the mobile bearing is completely unconstrained meaning that the system is kinematically indeterminate and this is why you see the error. In certain cases one could use an FDK solver to address questions like yours, but it might be very difficult.

  1. Do you really need the mobile bearing? What is your question of interest? If you are interested in the loads - you may fix and assume it not moving, having enough friction. If not - then try the next steps.

  2. For kinematic analyses (for example, MarkerTracking is a kinematic analysis) fix the bearing since the overall movement of the patient is not changing. You can only find movement of the bearing while performing an inverse dynamics using FDK.

  3. When you perform inverse dynamics you need to create a 6 dof constraint between, say, pelvis+cup and the bearing, where you set degrees of freedom to be force-dependent (and switch on the FDK solver in settings). Same for the head/bearing. You would also need to define all surface contacts elements and provide contact parameters. You will need some artificial stiffness on the FDK joints to prevent from components 'flying away' from each other.

  4. Try introducing FDK degrees of freedom 1 by 1 to gradually increase the complexity. And try to simplify your model as much as possible.

But if at all possible - I would consider not to model the mobile bearing.

Kind regards,


Thanks for your reply!! It has been very helpful/

As you said, it's really difficult, but I'm still trying... Thank you again for your thoughtful answers!

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