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Tracked Vehicle Sliding

I'm working with a tracked vehicle on the deck of a ship, and noticed that the vehicle slid around. With a little more research, I found that all tracked vehicles seem prone to sliding on a tilted surface.

For example, open the M1A2 tank from the 2018b samples. Set the grid material to Ground and set the x or y inclination to 3 degrees. When you hit Run, the tank starts to slide down the incline.

Is there a setting that needs to be adjusted to prevent this? I need to be able to drive tracked vehicles around and stop on inclined surfaces without slipping.

The tracks on M1A2 are set to have the same material as Wheel, which has a slip of 1e-4 s/kg while in contact with Ground. Try making a new materials table, and clone the Wheel material to a new "Track" material. Set the slip on that to be lower - in some basic testing, I've found that the M1A2 does not slip anymore if the slip is as low as 1e-5 s/kg on the linear axes. This number might change based on your mechanism.

See the attached gif for a demonstration.


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The documentation that refers to contact material starts at the page:User Guides > Mechanical Engineer Guide > Contact Materials

More specifically, for tuning a particular contact materials, go to:User Guides > Mechanical Engineer Guide > Contact Materials > Editing Contact Material Properties

Here is few more details for the slip:When this value is 0.0, we say that the contact implements dry friction. The force of friction is exactly what is expected according to the model chosen. 

When the slip is not zero, we say that the contact implements wet friction or viscous friction. Increasing the slip has a tendency to add some slippery in the contact and so the vehicle may slides.The effect of the slip is proportional to the mass of the object: the heavier and object is, the smaller the slip should be.

We recommend to start tuning the contact property with a slip equal to zero. Then, the slip can be increased by small increments to help a vehicle to steer or, in rare cases, to stabilize the simulation.

Vortex Studio - Support team 

CM Labs Simulations, Inc.
p: +1 514 287-1166 

Thanks all - these recommendations have solved the problem. The fact that the effect of contact slip is proportional to mass is extremely helpful. 

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