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/* -------------------------------------------------------------------------- *
* Simbody(tm) *
* -------------------------------------------------------------------------- *
* This is part of the SimTK biosimulation toolkit originating from *
* Simbios, the NIH National Center for Physics-Based Simulation of *
* Biological Structures at Stanford, funded under the NIH Roadmap for *
* Medical Research, grant U54 GM072970. See https://simtk.org/home/simbody. *
* *
* Portions copyright (c) 2009-12 Stanford University and the Authors. *
* Authors: Michael Sherman *
* Contributors: *
* *
* Licensed under the Apache License, Version 2.0 (the "License"); you may *
* not use this file except in compliance with the License. You may obtain a *
* copy of the License at http://www.apache.org/licenses/LICENSE-2.0. *
* *
* Unless required by applicable law or agreed to in writing, software *
* distributed under the License is distributed on an "AS IS" BASIS, *
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. *
* See the License for the specific language governing permissions and *
* limitations under the License. *
* -------------------------------------------------------------------------- */
/**@file
* Test the Force::Thermostat force element.
*/
#include "SimTKsimbody.h"
#include "SimTKcommon/Testing.h"
#include <cstdio>
#include <exception>
#include <iostream>
using std::cout; using std::endl;
using namespace SimTK;
class ThermoReporter : public PeriodicEventReporter {
public:
ThermoReporter(const MultibodySystem& sys,
const Force::Thermostat& thermo,
const Force::LinearBushing& bushing1,
const Force::LinearBushing& bushing2,
Real dt)
: PeriodicEventReporter(dt), system(sys), thermo(thermo),
bushing1(bushing1), bushing2(bushing2) {}
void handleEvent(const State& state) const override {
printf("THERMO t=%g, stage %s, KE+PE=%g Ebath=%g CONSERVED=%g\n",
state.getTime(),
state.getSystemStage().getName().c_str(),
system.calcEnergy(state),
thermo.calcBathEnergy(state),
system.calcEnergy(state)
+ thermo.calcBathEnergy(state)
+ bushing1.getDissipatedEnergy(state)
+ bushing2.getDissipatedEnergy(state));
printf("TEMP=%g N=%d Power=%g Work=%g\n",
thermo.getCurrentTemperature(state),
thermo.getNumThermalDofs(state),
thermo.getExternalPower(state),
thermo.getExternalWork(state));
}
private:
const MultibodySystem& system;
const Force::Thermostat& thermo;
const Force::LinearBushing& bushing1;
const Force::LinearBushing& bushing2;
};
void testConservationOfEnergy() {
// Create the system.
MultibodySystem system;
SimbodyMatterSubsystem matter(system);
GeneralForceSubsystem forces(system);
Force::UniformGravity gravity(forces, matter, Vec3(0, -9.8, 0));
const Real Mass = 1;
const Vec3 HalfShape = Vec3(1,.5,.25)/2;
const Transform BodyAttach(Rotation(), Vec3(HalfShape[0],0,0));
Body::Rigid brickBody(MassProperties(Mass, Vec3(.1,.2,.3),
Mass*Inertia(1,1.1,1.2,0.01,0.02,0.03)));
//Body::Rigid brickBody(MassProperties(Mass, Vec3(0),
// Mass*UnitInertia::ellipsoid(HalfShape)));
brickBody.addDecoration(Transform(), DecorativeEllipsoid(HalfShape)
.setOpacity(0.25)
.setColor(Blue));
brickBody.addDecoration(BodyAttach,
DecorativeFrame(0.5).setColor(Red));
const int NBod=50;
MobilizedBody::Free brick1(matter.Ground(), Transform(),
brickBody, BodyAttach);
MobilizedBody::Free brick2(brick1, Transform(),
brickBody, BodyAttach);
MobilizedBody prev=brick2;
MobilizedBody body25;
for (int i=0; i<NBod; ++i) {
MobilizedBody::Ball next(prev, -1*BodyAttach.p(),
brickBody, BodyAttach);
if (i==25) body25=next;
//Force::TwoPointLinearSpring(forces,
// prev, Vec3(0), next, Vec3(0), 1000, 1);
prev=next;
}
Constraint::Ball(matter.Ground(), Vec3(0,1,0)-2*NBod/3*BodyAttach.p(),
prev, BodyAttach.p());
Constraint::Ball(matter.Ground(), Vec3(0,1,0)-1*NBod/3*BodyAttach.p(),
body25, BodyAttach.p());
Vec6 k1(1,100,1,100,100,100), c1(0);
Force::LinearBushing(forces, matter.Ground(), -2*NBod/3*BodyAttach.p(),
prev, BodyAttach.p(), k1, c1);
matter.Ground().addBodyDecoration(-2*NBod/3*BodyAttach.p(),
DecorativeFrame().setColor(Green));
Force::Thermostat thermo(forces, matter,
SimTK_BOLTZMANN_CONSTANT_MD,
5000,
.1);
Vec6 k(1,100,1,100,100,100), c(0);
Force::LinearBushing bushing1(forces, matter.Ground(), -1*NBod/3*BodyAttach.p(),
brick1, BodyAttach, k, c);
Force::LinearBushing bushing2(forces, brick1, Transform(),
brick2, BodyAttach, k, c);
matter.Ground().addBodyDecoration(-1*NBod/3*BodyAttach.p(),
DecorativeFrame().setColor(Green));
Visualizer viz(system);
Visualizer::Reporter* reporter = new Visualizer::Reporter(viz, 1./30);
viz.setBackgroundType(Visualizer::SolidColor);
system.addEventReporter(reporter);
ThermoReporter* thermoReport = new ThermoReporter
(system, thermo, bushing1, bushing2, 1./10);
system.addEventReporter(thermoReport);
// Initialize the system and state.
system.realizeTopology();
State state = system.getDefaultState();
viz.report(state);
printf("Default state -- hit ENTER\n");
cout << "t=" << state.getTime()
<< " q=" << brick1.getQAsVector(state) << brick2.getQAsVector(state)
<< " u=" << brick1.getUAsVector(state) << brick2.getUAsVector(state)
<< "\nnChains=" << thermo.getNumChains(state)
<< " T=" << thermo.getBathTemperature(state)
<< "\nt_relax=" << thermo.getRelaxationTime(state)
<< " kB=" << thermo.getBoltzmannsConstant()
<< endl;
getchar();
state.setTime(0);
system.realize(state, Stage::Acceleration);
Vector initU(state.getNU());
initU = Test::randVector(state.getNU());
state.updU()=initU;
RungeKuttaMersonIntegrator integ(system);
//integ.setMinimumStepSize(1e-1);
integ.setAccuracy(1e-2);
TimeStepper ts(system, integ);
ts.initialize(state);
const State& istate = integ.getState();
viz.report(integ.getState());
viz.zoomCameraToShowAllGeometry();
printf("After initialize -- hit ENTER\n");
cout << "t=" << integ.getTime()
<< "\nE=" << system.calcEnergy(istate)
<< "\nEbath=" << thermo.calcBathEnergy(istate)
<< endl;
thermoReport->handleEvent(istate);
getchar();
// Simulate it.
ts.stepTo(20.0);
viz.report(integ.getState());
viz.zoomCameraToShowAllGeometry();
printf("After simulation:\n");
cout << "t=" << integ.getTime()
<< "\nE=" << system.calcEnergy(istate)
<< "\nEbath=" << thermo.calcBathEnergy(istate)
<< "\nNsteps=" << integ.getNumStepsTaken()
<< endl;
thermoReport->handleEvent(istate);
}
int main() {
SimTK_START_TEST("TestThermostat");
SimTK_SUBTEST(testConservationOfEnergy);
SimTK_END_TEST();
}
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