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
// All rights reserved.
//
// 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
// http://projectchrono.org/license-chrono.txt.
//
// =============================================================================
// 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_irrlicht/ChVisualSystemIrrlicht.h"
 
// Use the namespaces of Chrono
using namespace chrono;
using namespace chrono::irrlicht;
 
int main(int argc, char* argv[]) {
    GetLog() << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << "\n\n";
 
    // Create a physical system
    ChSystemNSC sys;
 
    // 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<ChMaterialSurfaceNSC>();
        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(ChVector<>(-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->SetWvel_par(ChVector<>(0, 0, -initial_angspeed));
        sphereBody->SetPos_dt(ChVector<>(initial_linspeed, 0, 0));
 
        // Add to the system
        sys.Add(sphereBody);
    }
 
    // 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<ChMaterialSurfaceNSC>();
        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(ChVector<>(-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->SetWvel_par(ChVector<>(0, 20, 0));
 
        // Add to the system
        sys.Add(sphereBody);
 
        // 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(ChVector<>(0, -1, 0));
    bin->SetBodyFixed(true);
    bin->SetCollide(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<ChMaterialSurfaceNSC>();
    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
    bin->GetCollisionModel()->ClearModel();
    utils::AddBoxGeometry(bin.get(), bin_mat, ChVector<>(20, 1, 20) / 2.0, ChVector<>(0, 0, 0), QUNIT, true,
                          bin_vis_mat);
    utils::AddBoxGeometry(bin.get(), bin_mat, ChVector<>(1, 2, 20.99) / 2.0, ChVector<>(-10, 1, 0), QUNIT, true,
                          bin_vis_mat);
    utils::AddBoxGeometry(bin.get(), bin_mat, ChVector<>(1, 2, 20.99) / 2.0, ChVector<>(10, 1, 0), QUNIT, true,
                          bin_vis_mat);
    utils::AddBoxGeometry(bin.get(), bin_mat, ChVector<>(20.99, 2, 1) / 2.0, ChVector<>(0, 1, -10), QUNIT, true,
                          bin_vis_mat);
    utils::AddBoxGeometry(bin.get(), bin_mat, ChVector<>(20.99, 2, 1) / 2.0, ChVector<>(0, 1, 10), QUNIT, true,
                          bin_vis_mat);
    bin->GetCollisionModel()->BuildModel();
 
    sys.Add(bin);
 
    // Create the Irrlicht visualization system
    auto vis = chrono_types::make_shared<ChVisualSystemIrrlicht>();
    vis->AttachSystem(&sys);
    vis->SetWindowSize(800, 600);
    vis->SetWindowTitle("Rolling and spinning friction");
    vis->Initialize();
    vis->AddLogo();
    vis->AddSkyBox();
    vis->AddCamera(ChVector<>(0, 14, -20));
    vis->AddLight(ChVector<>(30.f, 100.f, 30.f), 290, ChColor(0.7f, 0.7f, 0.7f));
    vis->AddLight(ChVector<>(-30.f, 100.f, -30.f), 190, ChColor(0.7f, 0.8f, 0.8f));
 
    // Modify some setting of the physical system for the simulation
    sys.SetSolverType(ChSolver::Type::APGD);
    sys.SetSolverMaxIterations(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;
}