From A/Chassis, I am referring Req/1051~43 for Tire Force & Moment data from vehicle data set. When I checked these Lateral Forces at 4 corners during a constant radius, they were shown as sine-wave-like oscillation around zero-value with a sizeable magnitude equivalent to a given slip angles. (same for Fx, except values for z-axis) I believe this is caused from these F&M values are being reported with a global reference marker... not a vehicle-fixed marker like a CG. Any thought on this? And what to do if F&M data is wanted to be reported in vehicle orientation? (No source code of Req/Subroutine is open to public.)
They are REQ/1050 ~1053 under 'user defined' group as LR/RR/LF/RF Tire Force.
When these F&M is plotted by the '(dynamic) constant radius' event, they are seen as oscillating about their neutral positions corresponding to vehicle position in on a circle, esp Lateral Force. This may have not been obvious in other events.
I have checked "REQ/1150, USER(20,...)" request routine, and find that the forces and torques are calculated at the wheel center with respect to a coordinate system whose Z axis is aligned with GlobalZ, and X and Y are shadow vector of spindle axes on the road. This routine only reads and returns results from the Tire output array, so my guess is that the coordinate system selection is hard coded somewhere in ATire solver. I will contact our tire developer to see if there is a workaround for this.
Slee (BTW: would be nice to know where you are and whom you are working for): ever thought about using FTire? It gives you tire/forces and moments both in contact patch and spindle (no, they are *not* the same) in nearly every coordinate system you might think about.
Yuan, while the original question is being investigated, may I ask to investigate in which coordinate system these F&M are handled? For example, PAC2002 tire model is by ISO coordinate with a vehicle model of SAE vehicle coordinate in A/Chassis. Is an ISO tire model converted into SAE , simulated in SAE and reported in SAE, while SAE-based tire model is being used directly without conversion? Or everything is ISO-based nowadays?
Hi, In the PAC2002 tire model, the force calculations are done within the ISO coordinate system, but in the tire interface the forces are converted to the global coordinate system of the model and applied to the spindle. In Adams Tire, there are some basic request outputs, forces and torques can be requested in ISO or SAE coordinate systems. Please find the attached screenshot for more details.
For the original question, the tire forces are working as a GFORCE on the spindles. You could refer to this GFORCE in your custom request. Like in the picture below,
GFORCE(id, jflag, comp, rm), where id should be equal to the tire id, and rm should be equal to the reference marker id.