tutorial_demo_crank.html

// =============================================================================

// 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

//

//  - constraints and 'motor' objects

//  - using IRRLICHT as a realtime 3D viewer of a slider-crank mechanism

//    simulated with Chrono.

//  - using the real-time step.

//

// This is just a possible method of integration of Chrono + Irrlicht;

// many others are possible.

//

// =============================================================================


#include "chrono/core/ChRealtimeStep.h"

#include "chrono/physics/ChSystemNSC.h"

#include "chrono/physics/ChLinkMotorRotationSpeed.h"


#include "chrono_irrlicht/ChVisualSystemIrrlicht.h"


// Use the namespaces of Chrono

using namespace chrono;

using namespace chrono::irrlicht;


int main(int argc, char* argv[]) {

    std::cout << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << std::endl;


    //

    // HERE YOU CREATE THE MECHANICAL SYSTEM OF CHRONO...

    //


    // 1- Create a Chrono physical system: all bodies and constraints

    //    will be handled by this ChSystemNSC object.


    ChSystemNSC sys;


    // 2- Create the rigid bodies of the slider-crank mechanical system

    //   (a crank, a rod, a truss), maybe setting position/mass/inertias of

    //   their center of mass (COG) etc.


    // ..the truss

    auto my_body_A = chrono_types::make_shared<ChBody>();

    sys.AddBody(my_body_A);

    my_body_A->SetFixed(true);  // truss does not move!

    my_body_A->SetName("Ground-Truss");


    // ..the crank

    auto my_body_B = chrono_types::make_shared<ChBody>();

    sys.AddBody(my_body_B);

    my_body_B->SetPos(ChVector3d(1, 0, 0));  // position of COG of crank

    my_body_B->SetMass(2);

    my_body_B->SetName("Crank");


    // ..the rod

    auto my_body_C = chrono_types::make_shared<ChBody>();

    sys.AddBody(my_body_C);

    my_body_C->SetPos(ChVector3d(4, 0, 0));  // position of COG of rod

    my_body_C->SetMass(3);

    my_body_C->SetName("Rod");


    // 3- Create constraints: the mechanical joints between the rigid bodies.


    // .. a revolute joint between crank and rod

    auto my_link_BC = chrono_types::make_shared<ChLinkLockRevolute>();

    my_link_BC->SetName("RevJointCrankRod");

    my_link_BC->Initialize(my_body_B, my_body_C, ChFrame<>(ChVector3d(2, 0, 0)));

    sys.AddLink(my_link_BC);


    // .. a slider joint between rod and truss

    auto my_link_CA = chrono_types::make_shared<ChLinkLockPointLine>();

    my_link_CA->SetName("TransJointRodGround");

    my_link_CA->Initialize(my_body_C, my_body_A, ChFrame<>(ChVector3d(6, 0, 0)));

    sys.AddLink(my_link_CA);


    // .. a motor between crank and truss

    auto my_link_AB = chrono_types::make_shared<ChLinkMotorRotationSpeed>();

    my_link_AB->Initialize(my_body_A, my_body_B, ChFrame<>(ChVector3d(0, 0, 0)));

    my_link_AB->SetName("RotationalMotor");

    sys.AddLink(my_link_AB);

    auto my_speed_function = chrono_types::make_shared<ChFunctionConst>(CH_PI);  // speed w=3.145 rad/sec

    my_link_AB->SetSpeedFunction(my_speed_function);


    // 4- Create the Irrlicht visualization system

    auto vis = chrono_types::make_shared<ChVisualSystemIrrlicht>();

    vis->AttachSystem(&sys);

    vis->SetWindowSize(800, 600);

    vis->SetWindowTitle("Simple slider-crank example");

    vis->Initialize();

    vis->AddLogo();

    vis->AddSkyBox();

    vis->AddCamera(ChVector3d(0, 0, -6));

    vis->AddTypicalLights();


    // Simulation loop


    // Timer for enforcing soft real-time

    ChRealtimeStepTimer realtime_timer;

    double time_step = 0.01;


    // bool removed = false;


    while (vis->Run()) {

        // Irrlicht must prepare frame to draw

        vis->BeginScene();


        // Irrlicht now draws simple lines in 3D world representing a

        // skeleton of the mechanism, in this instant:

        //

        // .. draw items belonging to Irrlicht scene, if any

        vis->Render();

        // .. draw a grid

        tools::drawGrid(vis.get(), 0.5, 0.5);

        // .. draw GUI items belonging to Irrlicht screen, if any

        vis->GetGUIEnvironment()->drawAll();


        // .. draw the rod (from joint BC to joint CA)

        tools::drawSegment(vis.get(), my_link_BC->GetMarker1()->GetAbsCoordsys().pos,

                           my_link_CA->GetMarker1()->GetAbsCoordsys().pos, ChColor(0, 1, 0));

        // .. draw the crank (from joint AB to joint BC)

        tools::drawSegment(vis.get(), my_link_AB->GetFrame2Abs().GetCoordsys().pos,

                           my_link_BC->GetMarker1()->GetAbsCoordsys().pos, ChColor(1, 0, 0));

        // .. draw a small circle at crank origin

        tools::drawCircle(vis.get(), 0.1, ChCoordsys<>(ChVector3d(0, 0, 0), QUNIT));


        /* test: delete a link after 10 seconds

        if (sys.GetChTime() >10 && (!removed))

        {

                sys.RemoveLink(my_link_AB);

                removed = true;

        }*/


        // ADVANCE SYSTEM STATE BY ONE STEP

        sys.DoStepDynamics(time_step);

        // Enforce soft real-time

        realtime_timer.Spin(time_step);


        // Irrlicht must finish drawing the frame

        vis->EndScene();

    }


    return 0;

}