Longitudinal slip not being updated in demo_VEH_TireTestRig_CRM

[Dan Fenn]

I'm putting together a simulation based on the demo_VEH_TireTestRig_CRM demo, and I'm trying to log the slip. I've noticed that even when I run the unmodified demo that ships with Chrono, the longitudinal slip isn't being calculated. The plots are all 0s. It seems that `CalculateKinematics()` is potentially not being called, but I'm not certain of that.

Any thoughts/help?

Dan

[Radu Serban]

Hi Dan,

 

This is because we do not have an efficient, robust, and general method for extracting terrain height and normal from CRM simulations. ChTire::CalculateKinematics relies on that information in order to calculate a tire frame and then the various quantities (such longitudinal slip and slip angle). By the way, the same is true for DEM terrains.

 

These tire kinematic values must be obtained outside of the tire code, using additional information about the concrete terrain type and geometry.  Having said that, this type of additional information is actually available in the setup of a ChTireTestRig (where we know the terrain is always flat and horizontal, regardless of its type).  I pushed changes to ChTireTestRig to calculate the longitudinal slip, slip angle, and camber angle.  Look at how I modified the two demos (including the one for CRM terrain) to extract and plot these values: use the functions on the rig object and not those on the tire.

 

--Radu

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