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Toe/Camber Issues with Trailing Arm Suspension

Logan Laing

Hello,

I am on a Baja SAE college team and am attempting to model the suspension for this year's vehicle in ADAMS Car. The plan is to use a trailing arm for rear suspension. I have attached the template file that I modeled. My problem is with the toe/camber for the wheel hub or wheel. When the 'Parallel Wheel Travel' Suspension Analysis is ran using the _MDI_SUSPENSION_TESTRIG, the toe/camber for the tire does match the appropriate motion of the trailing arm. The hub or tire delays the camber and toe change from the trailing arm motion, which would not happen with the real-life trailing arm as the hub is not allowed to pivot on the trailing arm.

I want the wheel/hub to be oriented with the plane made from the hardpoints UPTTAS, LTRTAS, and either UOAP or LOAP using the YX axis. What should I do to properly setup the toe/camber so that when the analysis is ran, the toe/camber is accurate to the model and can be used for design changes and updates?

 nexus.hexagon.com/.../_5F00_Rear_5F00_Suspension_5F00_Trailing_5F00_Arm.zip

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  • Have you tried to run the suspension test in kinematic mode? Does it behave the same?
    I don't see anything directly wrong with the template, but I don't know what bushing properties you have used. Or tire stiffness.

    There is no way that the tire and hub "delays" the motion, the simulation is quasi-static. So each step is a static equilibrium. But if your tires or bushings are too soft, you will get less motion of the WC compared to the road plate.

  • in reply to Jesper Slattengren

    I have not run it in kinematic mode. I did replace all the bushings in the model with joints. When I reran the test, I received this error:
    ---- START: ERROR ----

    Static equilibrium analysis has not been successful.

    The maximum number of iterations 25, has been reached.

    For the last attempted iteration:

    The equation with the largest error was model.rear_suspension_joints.gel_Upper_Tie_Rod Comp = 8 Error = 0.000000

    The variable receiving the largest increment was model.rear_suspension_joints.ger_Lower_Tie_Rod Comp = 10 Delta = 0.001482.

    ---- END: ERROR ----

    What does this mean?

  • in reply to Logan Laing

    This is what is happening. Before simulating the ACar model needs to be planted on the road, with no external forces "static equilibrium". If this fails simulation stops. As the message explains it has failed, but not by much Delta 0.001482. So, navigate to Settings > Solver > Equilibrium once there, tick "more" and press F1 to open the help. Try to understand up to "Imbalance" included. Open SimCompanon and search equilibrium and read some of the articles to get a better impression

    https://simcompanion.hexagon.com/customers/s/global-search/%40uri#q=static%20equilibrium&t=All&sort=relevancy

    My advice is the same as Jesper's: make sure you run a few suspension tests first, these are very fast and a reliable way of finding issues, making sure your model is robust. Otherwise finding issues with vehicle running will be much harder.

    hint: without seeing the model, I believe that making Maxit a bit larger 50-70 should suffice in this instance.

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  • in reply to Logan Laing

    This is what is happening. Before simulating the ACar model needs to be planted on the road, with no external forces "static equilibrium". If this fails simulation stops. As the message explains it has failed, but not by much Delta 0.001482. So, navigate to Settings > Solver > Equilibrium once there, tick "more" and press F1 to open the help. Try to understand up to "Imbalance" included. Open SimCompanon and search equilibrium and read some of the articles to get a better impression

    https://simcompanion.hexagon.com/customers/s/global-search/%40uri#q=static%20equilibrium&t=All&sort=relevancy

    My advice is the same as Jesper's: make sure you run a few suspension tests first, these are very fast and a reliable way of finding issues, making sure your model is robust. Otherwise finding issues with vehicle running will be much harder.

    hint: without seeing the model, I believe that making Maxit a bit larger 50-70 should suffice in this instance.

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