I am running full vehicle MBD analysis (NON-WIZARD) and facing some errors with Altair Driver. Please help!

Alex Mamic

I am trying to do some full vehicle MBD analysis for my Master degree. 

The object of my study is a Go-Kart model. I've created a CAD model of a Kart frame in SolidWorks and imported a STEP model of a Kart frame to MotionView in order to set up the model and perform MBD analysis. I've built up the kinematic model of a Kart and I've set up the non-wizard Altair Driver using the MV-8800 guide from help.altair website (https://2022.help.altair.com/2022.1/hwdesktop/mv/topics/tutorials/mv/tut_mv_8800_add_driver_2wheeler_t.htm).

But the analysis doesn't run. When I check my model I get a couple of errors such as: 

Unknown symbol BLANK...Error resolving entity Frame-cg under Model. [General]
Unknown symbol "att_b_veh.cg.x"...Math parser error evaluating Gyro location-x under Model-Altair Driver-Gyro. [General]
Unknown symbol "att_b_veh.cg.y"...Math parser error evaluating Gyro location-y under Model-Altair Driver-Gyro. [General]
Unknown symbol "att_b_veh.cg.z"...Math parser error evaluating Gyro location-z under Model-Altair Driver-Gyro. [General]

How can I fix them, what should I do? 

I haven't succeeded finding the solution in the forum section so I hope someone could help me here. Besides, I cannot export .XML file in order to examine the entities of the model. 

I'm attaching my MDL and STEP model files. If any other information needs to be provided, please let me know. 

P. S. .tir (tire sizing) files are not attachable to this topic. By now I've used basic TNO tire file and changed the tire size to 0.115 Unloaded Radius, 0.1 Rim and Tire Width and 0.06 Rim Radius. But I believe that the problem I'm facing is not connected to the .tir files. 

Jagadeesh R

Hi Alex,

Attached runnable model for your reference.

The mdl file which you shared is modified slightly to run with Altair driver and events.

     1] Frame body [main vehicle body]  and its cg is referred by driver to control the vehicle which need to be placed between two axles. Frame/vehicle body is required to select for driver attachment.

   2]  Frame to ground fixed joint is modified to perpendicular (1) and inline (2) joints to help to attain static during initial stage of event simulation. Altair driver will deactivate 1 & 2 after static simulation and run as per event requirement.

     3] Created wheel bodies at front and rear axle ends to attach with tires, (In your model, noticed fixed joints at tire rotating points.

4] Browse tires from installation just to run this attached model ".....\hwdesktop\hw\mdl\autoentities\properties\Tires\MF_SWIFT/TNO_mc120_85r10.tir".

     4] Rear drive line is rotating by using "rear axle rotational joint" created at center of rear axle which can be improved further by means of  creating half shafts and differentials.

Note:

1] Please refer example Sedan and Wizard car models to create and make use of of driveline, powertrain (attachments), tires bodies, mass and inertias, road ref marker position and direction to run with realistic data  and to compare the results wrt some reference.

2] Create entities like points, bodies, marker graphics using symmetry option to reduce the effort and also it will help to resolve the attachments and to select for tire entities.

 

thanks,

jagadeesh 

 

 

GTT Adam

Hi Alex,

If we open the MDL with a text editor, like notepad, we can see that the gyro definition only exists in one place.

The attachments for the vehicle body are causing issues, which in your case pertains to the "Frame" or b_NONE.

I can see that in the model, since graphics may be missing, that the mass and inertia for the Frame are not computing since the "Get Properties from Associated Graphics" are turned on.

I was able to clear the error messages by asserting the mass and inertia (uncheck the "Get Properties from Associated Graphics" and entering in any values) and also asserting a CM Marker that is between axles 1 and 2. In your case, I attached it to Point 0 as it looks to be at a good COG location. 

When I check the model, the gyro-related issues clear.

 

Hope this helps!

Adam Reid

Jagadeesh R

Hi Alex,

Attached runnable model for your reference.

The mdl file which you shared is modified slightly to run with Altair driver and events.

     1] Frame body [main vehicle body]  and its cg is referred by driver to control the vehicle which need to be placed between two axles. Frame/vehicle body is required to select for driver attachment.

   2]  Frame to ground fixed joint is modified to perpendicular (1) and inline (2) joints to help to attain static during initial stage of event simulation. Altair driver will deactivate 1 & 2 after static simulation and run as per event requirement.

     3] Created wheel bodies at front and rear axle ends to attach with tires, (In your model, noticed fixed joints at tire rotating points.

4] Browse tires from installation just to run this attached model ".....\hwdesktop\hw\mdl\autoentities\properties\Tires\MF_SWIFT/TNO_mc120_85r10.tir".

     4] Rear drive line is rotating by using "rear axle rotational joint" created at center of rear axle which can be improved further by means of  creating half shafts and differentials.

Note:

1] Please refer example Sedan and Wizard car models to create and make use of of driveline, powertrain (attachments), tires bodies, mass and inertias, road ref marker position and direction to run with realistic data  and to compare the results wrt some reference.

2] Create entities like points, bodies, marker graphics using symmetry option to reduce the effort and also it will help to resolve the attachments and to select for tire entities.

 

thanks,

jagadeesh 

 

 

Alex Mamic

Hi Adam and jagadeesh! 

Thank you very much for your help. 

The ideas you have mentioned are very helpful. The problem is solved

Actually, I figured out everything myself while my post was on moderation (it was my first publication), but glad you visited and contributed to the solution!