Rolling and spinning friction example (demo_MBS_friction.cpp)

A benchmark that show the feature of spinning friction (aka 'drilling' friction) and rolling friction.

These types of frictions are useful for rolling objects like wheels, spheres etc. and can be optionally turned on.

This tutorial shows how to:

• enable rolling and spinning friction.
• impose initial velocity and angular velocity to objects.
// =============================================================================
// PROJECT CHRONO - http://projectchrono.org
//
// Copyright (c) 2014 projectchrono.org
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file at the top level of the distribution and at
//
// =============================================================================
// Authors: Alessandro Tasora
// =============================================================================
//
// Demo code about
// - using rolling friction (not only sliding and static friction, available in
// all objects by default)
// - optional sharing of some assets (visualization stuff)
//
// =============================================================================
#include "chrono/physics/ChSystemNSC.h"
#include "chrono/physics/ChBodyEasy.h"
#include "chrono/utils/ChUtilsCreators.h"
#include "chrono/core/ChRealtimeStep.h"
#include "chrono/assets/ChVisualSystem.h"
#ifdef CHRONO_IRRLICHT
#include "chrono_irrlicht/ChVisualSystemIrrlicht.h"
using namespace chrono::irrlicht;
#endif
#ifdef CHRONO_VSG
#include "chrono_vsg/ChVisualSystemVSG.h"
using namespace chrono::vsg3d;
#endif
using namespace chrono;
int main(int argc, char* argv[]) {
std::cout << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << std::endl;
// Create a physical system
// Create all the rigid bodies.
double mradius = 0.5;
// Create a shared visualization material.
auto sph_vis_mat = chrono_types::make_shared<ChVisualMaterial>();
sph_vis_mat->SetKdTexture(GetChronoDataFile("textures/bluewhite.png"));
// Create some spheres that roll horizontally, with increasing rolling friction values
for (int bi = 0; bi < 10; bi++) {
auto mat = chrono_types::make_shared<ChContactMaterialNSC>();
mat->SetFriction(0.4f);
mat->SetRollingFriction(((float)bi / 10) * 0.05f);
auto sphereBody = chrono_types::make_shared<ChBodyEasySphere>(mradius, // radius size
1000, // density
true, // visualization?
true, // collision?
mat); // contact material
// Set some properties
sphereBody->SetPos(ChVector3d(-7, mradius - 0.5, -5 + bi * mradius * 2.5));
sphereBody->GetVisualShape(0)->SetMaterial(0, sph_vis_mat);
// Set initial speed: rolling in horizontal direction
double initial_angspeed = 10;
double initial_linspeed = initial_angspeed * mradius;
sphereBody->SetAngVelParent(ChVector3d(0, 0, -initial_angspeed));
sphereBody->SetPosDt(ChVector3d(initial_linspeed, 0, 0));
// Add to the system
}
// Create some spheres that spin on place, for a 'drilling friction' case, with increasing spinning friction values
for (int bi = 0; bi < 10; bi++) {
auto mat = chrono_types::make_shared<ChContactMaterialNSC>();
mat->SetFriction(0.4f);
mat->SetSpinningFriction(((float)bi / 10) * 0.02f);
auto sphereBody = chrono_types::make_shared<ChBodyEasySphere>(mradius, // radius size
1000, // density
true, // visualization?
true, // collision?
mat); // contact material
// Set some properties
sphereBody->SetPos(ChVector3d(-8, 1 + mradius - 0.5, -5 + bi * mradius * 2.5));
sphereBody->GetVisualShape(0)->SetMaterial(0, sph_vis_mat);
// Set initial speed: spinning in vertical direction
sphereBody->SetAngVelParent(ChVector3d(0, 20, 0));
// Add to the system
// Notes:
// - setting nonzero spinning friction and/or setting nonzero rolling friction
// affects the speed of the solver (each contact eats 2x of CPU time repsect to the
// case of simple sliding/staic contact)
// - avoid using zero spinning friction with nonzero rolling friction.
}
// Create a container fixed to ground
auto bin = chrono_types::make_shared<ChBody>();
bin->SetPos(ChVector3d(0, -1, 0));
bin->SetFixed(true);
bin->EnableCollision(true);
// Set rolling and friction coefficients for the container.
// By default, the composite material will use the minimum value for an interacting collision pair.
auto bin_mat = chrono_types::make_shared<ChContactMaterialNSC>();
bin_mat->SetRollingFriction(1);
bin_mat->SetSpinningFriction(1);
// Create a shared visualization material.
auto bin_vis_mat = chrono_types::make_shared<ChVisualMaterial>();
bin_vis_mat->SetKdTexture(GetChronoDataFile("textures/blue.png"));
// Add collision geometry and visualization shapes for the floor and the 4 walls
utils::AddBoxGeometry(bin.get(), bin_mat, ChVector3d(20, 1, 20), ChVector3d(0, 0, 0), QUNIT, true, bin_vis_mat);
utils::AddBoxGeometry(bin.get(), bin_mat, ChVector3d(1, 2, 20.99), ChVector3d(-10, 1, 0), QUNIT, true, bin_vis_mat);
utils::AddBoxGeometry(bin.get(), bin_mat, ChVector3d(1, 2, 20.99), ChVector3d(10, 1, 0), QUNIT, true, bin_vis_mat);
utils::AddBoxGeometry(bin.get(), bin_mat, ChVector3d(20.99, 2, 1), ChVector3d(0, 1, -10), QUNIT, true, bin_vis_mat);
utils::AddBoxGeometry(bin.get(), bin_mat, ChVector3d(20.99, 2, 1), ChVector3d(0, 1, 10), QUNIT, true, bin_vis_mat);
// Create the run-time visualization system
#ifndef CHRONO_IRRLICHT
#endif
#ifndef CHRONO_VSG
if (vis_type == ChVisualSystem::Type::VSG)
#endif
std::shared_ptr<ChVisualSystem> vis;
switch (vis_type) {
#ifdef CHRONO_IRRLICHT
auto vis_irr = chrono_types::make_shared<ChVisualSystemIrrlicht>();
vis_irr->AttachSystem(&sys);
vis_irr->SetWindowSize(800, 600);
vis_irr->SetWindowTitle("Rolling and spinning friction");
vis_irr->Initialize();
vis_irr->AddLight(ChVector3d(30.f, 100.f, 30.f), 290, ChColor(0.7f, 0.7f, 0.7f));
vis_irr->AddLight(ChVector3d(-30.f, 100.f, -30.f), 190, ChColor(0.7f, 0.8f, 0.8f));
vis = vis_irr;
#endif
break;
}
default:
#ifdef CHRONO_VSG
auto vis_vsg = chrono_types::make_shared<ChVisualSystemVSG>();
vis_vsg->AttachSystem(&sys);
vis_vsg->SetWindowSize(ChVector2i(800, 600));
vis_vsg->SetWindowPosition(ChVector2i(100, 100));
vis_vsg->SetWindowTitle("VSG Rolling Friction");
vis_vsg->SetClearColor(ChColor(0.8f, 0.85f, 0.9f));
vis_vsg->SetOutputScreen(0);
vis_vsg->SetUseSkyBox(true); // use built-in path
vis_vsg->SetOutputScreen(0);
vis_vsg->SetCameraVertical(CameraVerticalDir::Y);
vis_vsg->SetCameraAngleDeg(40.0);
vis_vsg->SetLightIntensity(1.0f);
vis_vsg->SetLightDirection(1.5 * CH_PI_2, CH_PI_4);
vis_vsg->SetWireFrameMode(false);
vis_vsg->Initialize();
vis = vis_vsg;
#endif
break;
}
}
// Modify some setting of the physical system for the simulation
sys.GetSolver()->AsIterative()->SetMaxIterations(100);
// Simulation loop
double timestep = 0.005;
ChRealtimeStepTimer realtime_timer;
while (vis->Run()) {
vis->BeginScene();
vis->Render();
vis->EndScene();
sys.DoStepDynamics(timestep);
realtime_timer.Spin(timestep);
}
return 0;
}
std::string GetChronoDataFile(const std::string &filename)
Get the full path to the specified filename, given relative to the Chrono data directory (thread safe...
Definition: ChGlobal.cpp:37
void Add(std::shared_ptr< ChPhysicsItem > item)
Attach an arbitrary ChPhysicsItem (e.g.
Definition: ChSystem.cpp:196
virtual std::shared_ptr< ChSolver > GetSolver()
Access the solver currently associated with this system.
Definition: ChSystem.h:124
Type
Supported run-time visualization systems.
Definition: ChVisualSystem.h:36
const ChQuaterniond QUNIT(1., 0., 0., 0.)
Constant unit quaternion: {1, 0, 0, 0} , corresponds to no rotation (diagonal rotation matrix)
Definition: ChQuaternion.h:431
Namespace with classes for the Irrlicht module.
Definition: ChApiIrr.h:47
Class for a timer which attempts to enforce soft real-time.
Definition: ChRealtimeStep.h:25
Accelerated Projected Gradient Descent.
void Spin(double step)
Call this function INSIDE the simulation loop, just ONCE per loop (preferably as the last call in the...
Definition: ChRealtimeStep.h:34
Definition of a visual color.
Definition: ChColor.h:30
void SetSolverType(ChSolver::Type type)
Choose the solver type, to be used for the simultaneous solution of the constraints in dynamical simu...
Definition: ChSystem.cpp:249
int DoStepDynamics(double step_size)
Advance the dynamics simulation by a single time step of given length.
Definition: ChSystem.cpp:1632
Bullet-based collision detection system.
ChVector3< double > ChVector3d
Alias for double-precision vectors.
Definition: ChVector3.h:283
void AddBoxGeometry(ChBody *body, ChContactMaterialSharedPtr material, const ChVector3d &size, const ChVector3d &pos, const ChQuaterniond &rot, bool visualization, ChVisualMaterialSharedPtr vis_material)
Add a box collision shape and optionally a corresponding visualization asset to the specified body.
Definition: ChUtilsCreators.cpp:75
Main namespace for the Chrono package.
Definition: ChCamera.cpp:17
virtual void SetCollisionSystemType(ChCollisionSystem::Type type)
Set the collision detection system used by this Chrono system to the specified type.
Definition: ChSystem.cpp:324
Class for a physical system in which contact is modeled using a non-smooth (complementarity-based) me...
Definition: ChSystemNSC.h:29
Namespace with classes for the VSG module.
Definition: ChApiVSG.h:51
ChVector2< int > ChVector2i
Alias for integer vectors.
Definition: ChVector2.h:227