Hello,
I have found some behavior that I don't understand. I made a simulation
with a box and a sphere in it. When I applied an angular velocity to the
box, the box's velocity decelerated by a factor of 4 every time the scene
would iterate.
I've included my code below. I find it really odd that the box is
decelerating, despite the fact that I set the angular acceleration of the
box to 0.
I'm very curious to understand what is happening.
Thanks,
Andy
#include "chrono/physics/ChBody.h"
#include "chrono/physics/ChSystemNSC.h"
#include "chrono_irrlicht/ChVisualSystemIrrlicht.h"
#include "chrono/assets/ChVisualMaterial.h"
#include "chrono/assets/ChColor.h"
#include "chrono/core/ChCoordsys.h"
#include "chrono/core/ChTypes.h"
#include "chrono/geometry/ChSphere.h"
#include "chrono/core/ChRotation.h"
int main()
{
double sphere_radius = 1.25;
// Make a red Sphere and a Green Box
auto vis_mat_red =
chrono_types::make_shared<chrono::ChVisualMaterial>();
vis_mat_red->SetDiffuseColor(chrono::ChColor(1.0f, 0.0f, 0.0f));
auto vis_mat_green =
chrono_types::make_shared<chrono::ChVisualMaterial>();
vis_mat_green->SetDiffuseColor(chrono::ChColor(0.0f, 1.0f, 0.0f));
auto vis_sphere =
chrono_types::make_shared<chrono::ChVisualShapeSphere>(sphere_radius);
vis_sphere->AddMaterial(vis_mat_red);
auto vis_box = chrono_types::make_shared<chrono::ChVisualShapeBox>(2.1,
1.3, 1.8);
vis_box->AddMaterial(vis_mat_green);
auto visual_model_sphere =
chrono_types::make_shared<::chrono::ChVisualModel>();
visual_model_sphere->AddShape(vis_sphere, chrono::ChFramed());
// Set Some Physical Properties of the sphere.
auto the_sphere_body = std::make_shared<chrono::ChBody>();
the_sphere_body->SetMass(6.0);
the_sphere_body->SetInertia(chrono::ChVector3d(1.0, 1.0, 1.0));
the_sphere_body->SetPos(chrono::ChVector3d(0, 0, 0));
auto visual_model_box =
chrono_types::make_shared<::chrono::ChVisualModel>();
visual_model_box->AddShape(vis_box, chrono::ChFramed());
auto the_box_body = std::make_shared<chrono::ChBody>();
// the_box_body->SetMass(5.0);
chrono::ChFramed box_frame(chrono::ChVector3d(4.0, 2.3, 1.778), 0);
//Set the physical properties of the box.
the_box_body->SetCoordsys(chrono::ChCoordsys(box_frame.GetCoordsys()));
the_box_body->SetRotDt(chrono::QuatFromAngleX(5));
the_box_body->SetRotDt2(chrono::ChQuaterniond(0, 0, 0, 0));
the_box_body->SetInertia(chrono::ChMatrix33d(2.0));
// the_box_body->SetLinVel(chrono::ChVector3d(-1,0,0));
the_sphere_body->AddVisualModel(visual_model_sphere);
the_box_body->AddVisualModel(visual_model_box);
auto sys = chrono::ChSystemNSC();
sys.Add(the_sphere_body);
sys.Add(the_box_body);
sys.SetGravitationalAcceleration(0.0);
auto vis_system =
chrono_types::make_shared<chrono::irrlicht::ChVisualSystemIrrlicht>();
vis_system->AttachSystem(&sys);
vis_system->SetWindowSize(800, 600);
vis_system->SetWindowTitle("I made a Demo!!!");
vis_system->Initialize();
vis_system->AddLogo();
vis_system->AddSkyBox();
vis_system->AddCamera(chrono::ChVector3d(-2, 4, -2));
vis_system->AddTypicalLights();
std::size_t counter = 0;
std::cout << "Box angular Velocity is " <<
the_box_body->GetAngVelLocal() << std::endl;
while (vis_system->Run())
{
vis_system->BeginScene();
vis_system->Render();
chrono::irrlicht::tools::drawGrid(vis_system.get(), 0.5, 0.5, 12,
12,
chrono::ChCoordsys<>(chrono::ChVector3d(0, 0, 0),
chrono::QuatFromAngleX(chrono::CH_PI_2)),
chrono::ChColor(0.31f, 0.43f,
0.43f), true);
vis_system->EndScene();
sys.DoStepDynamics(0.01);
if (counter < 10)
{
std::cout << "Box angular Velocity is " <<
the_box_body->GetAngVelLocal() << std::endl;
++counter;
}
}
return 0;
}
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