4344a73231
Simple swinging pendulum simulation with 1-DoF. The motion is integrated
using a symplectic method for just over 2-periods.
99 lines
2.9 KiB
C
99 lines
2.9 KiB
C
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration |
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\\ / A nd | Copyright (C) 2016 OpenFOAM Foundation
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\\/ M anipulation |
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-------------------------------------------------------------------------------
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License
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This file is part of OpenFOAM.
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OpenFOAM is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
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Application
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pendulum
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Description
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Simple swinging pendulum simulation with 1-DoF. The motion is integrated
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using a symplectic method for just over 2-periods.
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\*---------------------------------------------------------------------------*/
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#include "rigidBodyModel.H"
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#include "joints.H"
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using namespace Foam;
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using namespace RBD;
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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int main(int argc, char *argv[])
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{
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// Create a model for the pendulum
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rigidBodyModel pendulum;
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// Join a weight to the origin with a centre of mass -1m below the origin
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// by a hinge which rotates about the z-axis
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pendulum.join
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(
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0,
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Xt(vector(0, 0, 0)),
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joint::New(new joints::Rz(pendulum)),
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rigidBody::New("hinge", 1, vector(0, -1, 0), 0.02*I)
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);
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// Create the joint-space state fields
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scalarField q(pendulum.nDoF(), Zero);
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scalarField w(pendulum.nw(), Zero);
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scalarField qdot(pendulum.nDoF(), Zero);
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scalarField qddot(pendulum.nDoF(), Zero);
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scalarField tau(pendulum.nDoF(), Zero);
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// Set the angle of the pendulum to 0.3rad
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q[0] = 0.3;
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// Set the gravitational acceleration
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pendulum.g() = vector(0, -9.81, 0);
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// Integrate the motion of the pendulum for 4.1s (~2-periods) using a
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// symplectic method
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scalar deltaT = 0.01;
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for (scalar t=0; t<4.1; t+=deltaT)
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{
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qdot += 0.5*deltaT*qddot;
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q += deltaT*qdot;
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pendulum.forwardDynamics
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(
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q,
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w,
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qdot,
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tau,
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Field<spatialVector>(),
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qddot
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);
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qdot += 0.5*deltaT*qddot;
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Info<< "Time << " << t << "s, angle = " << q[0] << "rad" << endl;
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}
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Info<< "\nEnd\n" << endl;
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return 0;
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}
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// ************************************************************************* //
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