Tymo, You are doing a dynamics analysis, more precisely “forward dynamics”. In this case, the motion of the system is dictated by its initial state (positions and velocities) and the set of applied forces. Forward dynamics analysis calculates the accelerations (think Newton’s second law a = F/m) and then integrates to find the new velocity and position.
In the examples you show, gravity is the only applied force so, as expected, the body’s acceleration will end up being the gravitational acceleration. The function SetPos_dtdt can be used for other types of analysis, for example inverse dynamics. --Radu From: [email protected] <[email protected]> On Behalf Of Tymo Sent: Wednesday, 16 November 2022 22:29 To: ProjectChrono <[email protected]> Subject: [chrono] G_acc overrides SetPos_dtdt. What's the point? There is a problem with SetPos_dtdt. coords_dtdt.pos seems to be overwritten with G_acc, so what is the point of SetPos_dtdt? ChSystemNSC sys; auto body = make_shared<ChBody>(); sys.AddBody(body); body->SetPos_dtdt(Vector(0, 1, 0)); cout << body->GetPos_dtdt().y() << endl;//1 sys.DoFrameDynamics(1); cout << body->GetPos_dtdt().y() << endl;//-9.81 value overwritten sys.Set_G_acc(Vector(0, 0, 0)); body->SetPos_dtdt(Vector(0, 1, 0)); cout << body->GetPos_dtdt().y() << endl;//1 sys.DoFrameDynamics(2); cout << body->GetPos_dtdt().y() << endl;//0 value overwritten again -- 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]>. To view this discussion on the web visit https://groups.google.com/d/msgid/projectchrono/e4fd6b97-06ae-4381-a12f-c45eef5a772an%40googlegroups.com<https://groups.google.com/d/msgid/projectchrono/e4fd6b97-06ae-4381-a12f-c45eef5a772an%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/PH0PR06MB8237EAC1F2AC7ED86C8BF372A7079%40PH0PR06MB8237.namprd06.prod.outlook.com.
