Hi Radu, Thank you for all the information you've shared so far and the fixes you've provided. However I am still having some issues.
For this project, I will be using deformable (primarily SCM) terrain, so the rigid tire makes the most sense. As you suggested I am now using the smooth contact model (with a MINRES solver). The below plot shows the output of the slip angle over time, which should be a smooth sinusoidal function with about half the frequency. The longitudinal slip appears correct, but it seems there may be a bug with the newly added slip angle calculation. Additionally, I tried doing a run with an FEA tire, and there was no slip output. I believe this is the same issue as before, where the `CalculateKinematics` is not getting called. And as one last comment, when running the FEA simulation with the BARZILAIBORWEIN solver, there was a helpful exception thrown which informed be to use the MINRES solver. When I earlier tried running the FEA simulation with a nonsmooth contact formulation, there was a segmentation fault. I believe this is because the assert that would catch it was disabled as a result of me compiling in release mode, then it attempted to deference a nullptr. If possible, it would be more user friendly to throw a similar exception when a nonsmooth contact solver is used. Please let me know your thoughts and if I can be of any assistance in making changes. James [image: Screenshot_20230131_114903.png] On Monday, January 23, 2023 at 5:12:39 PM UTC-5 Radu Serban wrote: > James, > > > > A rigid tire is appropriate only in very specific situations (e.g., on > soft deformable terrain). In some demos we also use such tires on rigid > terrain, but those are just that – demos. Do not read too much into tire > kinematics properties from a rigid tire model. Instead, like you already > did, switch to a proper tire model (TMeasy, Pac02, Pac89, Fiala). > > Having said that, I pushed a change to the code to also invoke > CalculateKinematics for a ChRigidTire. You will notice that the outputs > can be quite noisy – this is because the tire-terrain interaction is done > here through frictional contact between two rigid bodies. If you really > want to use that tire model, you should use a ChSystemSMC (smooth contact > formulation). > > > > --Radu > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *James Baxter > *Sent:* Sunday, 22 January 2023 02:45 > *To:* ProjectChrono <[email protected]> > *Subject:* Re: [chrono] Re: High frequency noise in virtual tire test rig > > > > Looking into it further, I found that the flat line for slip angle and > longitudinal slip is indeed a bug in Chrono's code rather than my own. With > the new 8.0.0 release, only some tires call `CalculateKinematics`, which is > responsible for updating those values. In the above, I was using > HMMWV_RigidTire, which does not update those values. This appears to be the > relevant commit: c9167c87e32c54e1936c9d90e12c50793ebde1e0 > <https://github.com/projectchrono/chrono/commit/c9167c87e32c54e1936c9d90e12c50793ebde1e0> > . > > > > You can see that the virtual function, `Synchronize` is only being being > overridden by several tire models, and Rigid Tire is not one of them. I > assume this is a bug and not intentional behavior? > > > > Due to this, I switched to the TMeasyTire, and it is working as intended. > Additionally, the changes to reduce noise seem to have worked: > > > > TMeasy on 7.0.3: > > > > TMeasy on 8.0.0: > > > > > > > > > > On Wednesday, January 18, 2023 at 12:15:41 PM UTC-5 James Baxter wrote: > > Hi Radu and Rainer, > > > > Thank you for pushing some changes for me to test, and sorry for the > delayed response. The fix (I am using the 8.0.0 release tag) definitely > smoothed out noise on one of the plots (longitudinal slip, slip angle, > camber_angle), but I was expecting a sinusoidal shape for the slip angle > rather than a flat line. The tire force seems to still have about the same > degree of noise. See the below plots. > > > > I'll play around with it some more this week and let you know if the > results make sense. > > > > Also, I encountered an error with the renderer (likely due to me using it > in an odd way) and opened a PR: > https://github.com/projectchrono/chrono/pull/435 > > > > On Monday, December 19, 2022 at 12:30:31 PM UTC-5 Radu Serban wrote: > > James, > > Rainer’s fix worked in an indirect way. I pushed some changes that should > address the issue you reported. Please let me know if the results are now > more as you expect them. > > --Radu > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *[email protected] > *Sent:* Friday, 16 December 2022 08:51 > *To:* ProjectChrono <[email protected]> > *Subject:* [chrono] Re: High frequency noise in virtual tire test rig > > > > Hi James, > > > > the HMMWV wheel had inertia parameters, which were too low in this > context. They have been replaced by estimated values based on physics. > > Please pull the last chrono changes and try again. > > > > Best > > > > Rainer > > James Baxter schrieb am Montag, 12. Dezember 2022 um 03:20:55 UTC+1: > > bumping this back to the top since I haven't received any response yet and > am still facing this issue. > > On Monday, November 28, 2022 at 10:25:41 AM UTC-5 James Baxter wrote: > > When plotting the output data from the virtual tire test rig ( > https://api.projectchrono.org/7.0.0/wheeled_rig.html#wheeled_rig_tire), I > observe high frequency noise on the outputs. See the attached plots. > > > > Is this to be expected? Can it be mitigated through different solver > settings? > > > > All solver / timestep settings are unchanged from the demo file showing > how to use the test rig: > > - BARZILAIBORWEIN solver > > - 150 max iterations > > - 4.0 max penetration recovery speed > > - step_size 1e-3 > > - tire_step_size 1e-4 > > > > Thanks, > > James > > [image: Image removed by sender.][image: Image removed by sender.] > > > > > > -- > You received this message because you are subscribed to the Google Groups > "ProjectChrono" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/projectchrono/e52e6334-9ec7-4a7b-a093-c6085e66839cn%40googlegroups.com > > <https://groups.google.com/d/msgid/projectchrono/e52e6334-9ec7-4a7b-a093-c6085e66839cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "ProjectChrono" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/projectchrono/0fa54311-ad17-44e2-941c-8c0f0ce41b77n%40googlegroups.com > > <https://groups.google.com/d/msgid/projectchrono/0fa54311-ad17-44e2-941c-8c0f0ce41b77n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. 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