Jyotirmoy and Ekansh, Just a couple more clarifications and details beyond what Dan already told you.
* None of the tire models from the family of “force element”-type models (i.e., derived from ChForceElementTire, including Pacejka, Fiala, TMeasy) carry any collision geometry and as such cannot be used on deformable terrain. This is without also considering that the range of applicability of these models is relatively limited to rigid, relatively flat surfaces. * These tire models can currently be used only in conjunction with a RigidTerrain (or with a custom terrain system which implements the necessary which implements the necessary functions for querying terrain height and normal at a given (x,y) location). * If you are interested in deformable terrain, the two options for appropriate tire models currently available in Chrono are rigid tire and an FEA tire. Beside the drawbacks of using an FEA tire that Dan already mentioned, keep in mind that appropriate data for such a tire model is not easy to obtain. * As a side note: the Chrono FEA tire models properly consider internal tire pressure (which is interpreted as a distributed load on the inward faces of the shell elements used to model them. TMeasy has an option (which I assume you use) of specifying internal tire pressure as a mechanism for estimating the actual TMeasy model parameters (in other words, the internal pressure is not an actual parameter of the TMeasy model). There are variants of the Pacejka model that account for internal tire pressure, but those are not in the Chrono implementations. * Finally, although that is probably irrelevant for your immediate needs, I hope we will have a model of deformable tire that can interact with deformable terrain at a computational cost much less than that of current FEA tires in the not-too-distant future. But that’s WIP. Regarding your question about reporting tire forces, note that there are two versions of the function ReportTireForce. See ChForceElementTire<https://github.com/projectchrono/chrono/blob/main/src/chrono_vehicle/wheeled_vehicle/tire/ChForceElementTire.h> (lines 36 & 42). One reports the resultant force and moment (expressed in the global reference frame) at the spindle COM; the other returns the tire force and moment expressed in the tire frame (which is also returned by this function). This is a change I made about a month ago. Update to the latest code if you have not done so already. --Radu From: [email protected] <[email protected]> On Behalf Of Ekansh Chaturvedi Sent: Wednesday, March 29, 2023 5:51 PM To: ProjectChrono <[email protected]> Subject: [chrono] Re: Query regarding creating tire file in Chrono Hello Dr. Negrut, Thank you for the reply. We are trying to simulate a terramechanics rig using the "CHTiretestrig" class functions. In the experiment, the output I'm looking for is the tire forces (which as far as I understand from ReportTireForces()is, the force at the spindle and not the contact patch forces?) and for input, I want to vary the inflation pressure and other tire parameters. This will help us to obtain the drawbar pull for different inputs in addition to inflation pressure, such as wheel speed, slip ratios etc. Specifically, studying tire behaviors on deformable terrain is a priority in this project. For this purpose, I used the TMeasytire model as it had a functionality of giving tire inflation pressure as input. Could you please give your thoughts on formulating this problem using the available libraries in chrono? We basically need a test rig mechanism, tire and deformable terrain. Please let us know your thoughts. Thank you, Sincerely, Jyotirmoy Mukherjee On Wednesday, March 29, 2023 at 4:05:14 PM UTC-4 Dan Negrut wrote: Ekansh - one can't use Pacejka or TMEasy with SCM or CRM or DEM (deformable terrains, that is). The only way to do that would be to use an FEA tire model. That would be though painstaking and would run very slowly. Is it a possibility to consider the terrain rigid? Then you are good to go with TMEasy. Dan On Tuesday, March 28, 2023 at 3:23:29 PM UTC-5 [email protected] wrote: Hi, Hope this email finds you well. We are using Chrono to conduct an on-rig analysis of different tires and we are pretty new to using Chrono. We are stuck while trying to create a custom tire file that takes tire inflation pressure in units of pressure, along with the other structural dimensions, as an input . It's been a month and we are still trying to figure that out. We have realized that we cannot waste time anymore on trying ourselves as the deadlines are coming close, and we need help. We would really appreciate it if you could help us out with this through a zoom meeting. Please share your availability and feel free to let us know if you have any questions or concerns. Thanks and regards, Sincerely, Ekansh Chaturvedi Graduate Student, Terramechanics, Multibody and Vehicle Systems Laboratory (TMVS), Computational Sciences Laboratory (CSL), Department of Mechanical Engineering Virginia Tech -- 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]<mailto:[email protected]>. 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