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Steering Wobble - Straight Line simulation.

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John.B

John.B

Automotive
May 11, 2024
7
Hello,

I have been working on a rigid chassis truck model (10x4 configuration) with Twin Steering. While doing straight-line simulations the steering starts to wobble violently after 5 seconds into the simulation.
I thought of adjusting the caster angle by changing the kingpin hardpoints, but I guess that's not a good practice since it's not parametrized like camber and toe.
What are some possible options that I can try out to resolve this issue?

(I'm using HHT solver for the simulation)

PFA Screenshot for reference.

Thanks,
John
 
 https://files.engineering.com/getfile.aspx?folder=71b1b21b-7e35-4639-8d3f-bdc19a6cca18&file=Screenshot_2024-08-08_112639.png
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Reduce your timestep a lot, to maybe .01 or .001 seconds. Secondly try a swept steer. Thirdly look at animations and check that nothing silly is happening.

Caster does increase steering damping, there's no particular reason not to change it. How much have you got?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Hi Greg

I was running with 4deg of caster, increasing it did really help in damping the wobble. Can't seem to understand why the simulation ran into an error the first time I tried it.
Also I didn't notice any wobble in swept steer.

Thanks,
John
 
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4 degrees is low but should be sufficient. did reducing dt help in the straight line sim? Swept steer is easier for the steering becuase the forces are increasing in a nice way and not setting off any physical or numerical rattles.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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No, I didn't notice any significant difference when I reduced the step time.

Thanks,
John
 
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