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Ball joint force analysis using wheel force transducer data

Hi everyone,

I’m part of the Baja SAE team at the University of Sherbrooke. Last semester, we were able to run our BAJA with a Wheel Force Transducer (WFT). Since we want to reduce the weight of our suspension subsystem, we’re looking for a way to use the data collected with our WFT test directly in Altair MotionSolve. The goal is to apply the measured wheel forces in our suspension model to calculate the resulting loads at the ball joint. It will be a great way to compare it to our hand calculation.

I’ve searched for tutorials or documentation explaining how to import WFT data into MotionSolve, but I haven’t found anything useful. Is there a course, guide, or example somewhere that covers this topic?

Thanks in advance!

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Accepted answers

GTT Adam

Hi @MarcAntoineCharette

Yes! You do not need to define inputs for the other 3 posts if you only have data for a single post.

However, since there are no constraints or forces applied to the other 3 posts, the wheels will sag. If it will effect your results, simply apply a fixed joint from the wheel hub to ground to keep them in place.

Hope this helps!

Adam Reid

GTT Adam

Hi @MarcAntoineCharette,

To measure a specific entity during the simulation, like the forces/moments acting on a Joint, simply create an Output:

After selecting the Output icon, a guide bar will appear at the top of the viewscreen (below in green) where you can initially define the Output. In this example, I have changed the type to Force, selection by Entity, set the Entity to Joint, and then picked the Lower Ball Joint. I also have the option to set a reference marker if I want the forces/moments recorded in a certain reference frame other than the Global Reference System.

After defining the Output, you can review the selections in the Entity Editor (below in yellow).

Once you simulate the event, the results can be plotted using HyperGraph and by loading in the results PLT file.

For more on Outputs, please review the Help Documentation link: https://help.altair.com/hwdesktop/hwx/topics/motionview/outputs_r.htm

Please make sure to review our Getting Started with MotionView/MotionSolve eLearning, as these topics are covered here in high levels of detail.

Hope this helps!

Adam Reid

image.png

All comments

GTT Adam

Hi @MarcAntoineCharette,

The process of applying loads captured by a wheel force transducer (WFT) is very simple using MotionView through the definition of a n-Post event.

After creating your vehicle model, a n-Post event can be applied from the Entity Browser as shown below:

The n-Post can be attached by the tires through tire jacks or at the spindle:

Tire Jacks:

Tire Spindles:

Vehicle body constraint methods can also be modified to either hard, soft, or free depending on the load case. The wheel signal type can also be set to displacement, acceleration, or force/moment.

In your case, you will set the vehicle constraint to hard and the signal type to forces/moments.

Next, you can set a post to modify. Shown below I have selected the Tire - Front - Left. Then, choose a CSV file that contains the Fx, Fy, Fz, Mx, My, and Mz data with respect to time for each input (x data, y data, etc.)

To see the proper format of the CSV file inputs, you can see examples in the instllation directory here:

C:\Program Files\Altair\2025.1\hwdesktop\hw\mdl\autoentities\properties\nPost

After you have defined forces/moments for all 4 posts, you can simulate your model.

Help documentation for the n-Post event can be found here: https://help.altair.com/hwdesktop/hwx/topics/motionview/n-post_event_r.htm

For more on MotionView/MotionSolve, and also vehicle dynamics specific material, please make sure to check out our eLearning hub for several insightful modules to help you master these incredible Altair products.

Hope this helps!

Adam Reid

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GTT Adam

Results GIF failed to attached the first time:

results.gif

MarcAntoineCharette

Hi Adam,

Thanks for your quick and detailed response. Would the procedure be the same if I want to test just one wheel at a time?

Thanks!

Marc

GTT Adam

Hi @MarcAntoineCharette

Yes! You do not need to define inputs for the other 3 posts if you only have data for a single post.

Hope this helps!

Adam Reid

MarcAntoineCharette

Hi @GTT Adam ,

Thanks to your clear explanation, I was able to run my files through the model. However, I’m still not entirely sure how to determine the loads at the ball joint and the tie rod.

Thanks!
Marc

GTT Adam

Hi @MarcAntoineCharette,

To measure a specific entity during the simulation, like the forces/moments acting on a Joint, simply create an Output:

After defining the Output, you can review the selections in the Entity Editor (below in yellow).

Once you simulate the event, the results can be plotted using HyperGraph and by loading in the results PLT file.

For more on Outputs, please review the Help Documentation link: https://help.altair.com/hwdesktop/hwx/topics/motionview/outputs_r.htm

Please make sure to review our Getting Started with MotionView/MotionSolve eLearning, as these topics are covered here in high levels of detail.

Hope this helps!

Adam Reid

image.png