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/* -------------------------------------------------------------------------- *
* Simbody(tm) Example: Cable Path *
* -------------------------------------------------------------------------- *
* 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) 2012 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. *
* -------------------------------------------------------------------------- */
/* Simbody ExampleCablePath
This example shows how to use a CableTrackerSubsystem to follow the motion of
a cable that connects two bodies and passes around obstacles. We'll then
create a force element that generates spring forces that result from the
stretching and stretching rate of the cable. */
#include "Simbody.h"
#include <cassert>
#include <iostream>
using std::cout; using std::endl;
using namespace SimTK;
// This gets called periodically to dump out interesting things about
// the cables and the system as a whole. It also saves states so that we
// can play back at the end.
static Array_<State> saveStates;
class ShowStuff : public PeriodicEventReporter {
public:
ShowStuff(const MultibodySystem& mbs,
const CableSpring& cable1, Real interval)
: PeriodicEventReporter(interval),
mbs(mbs), cable1(cable1) {}
static void showHeading(std::ostream& o) {
printf("%8s %10s %10s %10s %10s %10s %10s %10s %10s %12s\n",
"time", "length", "rate", "integ-rate", "unitpow", "tension", "disswork",
"KE", "PE", "KE+PE-W");
}
/** This is the implementation of the EventReporter virtual. **/
void handleEvent(const State& state) const override {
const CablePath& path1 = cable1.getCablePath();
printf("%8g %10.4g %10.4g %10.4g %10.4g %10.4g %10.4g %10.4g %10.4g %12.6g CPU=%g\n",
state.getTime(),
path1.getCableLength(state),
path1.getCableLengthDot(state),
path1.getIntegratedCableLengthDot(state),
path1.calcCablePower(state, 1), // unit power
cable1.getTension(state),
cable1.getDissipatedEnergy(state),
mbs.calcKineticEnergy(state),
mbs.calcPotentialEnergy(state),
mbs.calcEnergy(state)
+ cable1.getDissipatedEnergy(state),
cpuTime());
saveStates.push_back(state);
}
private:
const MultibodySystem& mbs;
CableSpring cable1;
};
int main() {
try {
// Create the system.
MultibodySystem system;
SimbodyMatterSubsystem matter(system);
CableTrackerSubsystem cables(system);
GeneralForceSubsystem forces(system);
system.setUseUniformBackground(true); // no ground plane in display
Force::UniformGravity gravity(forces, matter, Vec3(0, -9.8, 0));
//Force::GlobalDamper(forces, matter, 5);
Body::Rigid someBody(MassProperties(1.0, Vec3(0), Inertia(1)));
const Real Rad = 1.5;
someBody.addDecoration(Transform(),
DecorativeSphere(Rad).setOpacity(.75).setResolution(4));
Body::Rigid biggerBody(MassProperties(1.0, Vec3(0), Inertia(1)));
const Real BiggerRad = .5;
biggerBody.addDecoration(Transform(),
DecorativeSphere(BiggerRad).setOpacity(.75).setResolution(4));
const Vec3 radii(2,1.5,1.7);
Body::Rigid ellipsoidBody(MassProperties(1.0, Vec3(0),
UnitInertia::ellipsoid(radii)));
//ellipsoidBody.addDecoration(Transform(),
// DecorativeEllipsoid(radii).setOpacity(.9).setResolution(4)
// .setColor(Orange));
const Real CylRad = .25, HalfLen = .5;
Body::Rigid cylinderBody(MassProperties(1.0, Vec3(0),
1.*UnitInertia::cylinderAlongX(Rad,HalfLen)));
cylinderBody.addDecoration(Rotation(-Pi/2,ZAxis),
DecorativeCylinder(CylRad,HalfLen).setOpacity(.75)
.setResolution(4).setColor(Orange));
Body::Rigid fancyBody = biggerBody; // NOT USING ELLIPSOID
MobilizedBody Ground = matter.Ground();
MobilizedBody::Free body1(Ground, Transform(Vec3(0)),
ellipsoidBody, Transform(Vec3(0)));
CablePath path1(cables, Ground, Vec3(-5,0,-.5),
Ground, Vec3(5,0,-.5));
CablePath path2(cables, Ground, Vec3(-5,0,.5),
Ground, Vec3(5,0,.5));
CableSpring cable1(forces, path1, 15000., 10, 0.1);
CableSpring cable2(forces, path2, 15000., 10, 0.1);
CableObstacle::Surface theBall1(path1, body1, Vec3(0),
ContactGeometry::Ellipsoid(radii));
//ContactGeometry::Sphere(Rad));
theBall1.setContactPointHints(Vec3(-.5,-1.5,-.5),Vec3(.5,-1.5,-.5));
CableObstacle::Surface theBall2(path2, body1, Vec3(0),
ContactGeometry::Ellipsoid(radii));
//ContactGeometry::Sphere(Rad));
theBall2.setContactPointHints(Vec3(-.5,-1.5,.5),Vec3(.5,-1.5,.5));
Visualizer viz(system);
viz.setShowFrameNumber(true);
system.addEventReporter(new Visualizer::Reporter(viz, 0.1*1./30));
system.addEventReporter(new ShowStuff(system, cable1, 0.1*0.1));
// Initialize the system and state.
system.realizeTopology();
State state = system.getDefaultState();
body1.setQToFitTranslation(state, Vec3(0,.9,0));
body1.setUToFitAngularVelocity(state, 0*.25*Vec3(1,4,1));
system.realize(state, Stage::Position);
viz.report(state);
cout << "path1 init length=" << path1.getCableLength(state) << endl;
cout << "Hit ENTER ...";
getchar();
path1.setIntegratedCableLengthDot(state, path1.getCableLength(state));
// Simulate it.
saveStates.clear(); saveStates.reserve(2000);
RungeKuttaMersonIntegrator integ(system);
//CPodesIntegrator integ(system);
integ.setAccuracy(1e-3);
TimeStepper ts(system, integ);
ts.initialize(state);
ShowStuff::showHeading(cout);
const Real finalTime = 5;
const double startTime = realTime(), startCPU = cpuTime();
ts.stepTo(finalTime);
cout << "DONE with " << finalTime
<< "s simulated in " << realTime()-startTime
<< "s elapsed, " << cpuTime()-startCPU << "s CPU.\n";
while (true) {
cout << "Hit ENTER FOR REPLAY, Q to quit ...";
const char ch = getchar();
if (ch=='q' || ch=='Q') break;
for (unsigned i=0; i < saveStates.size(); ++i)
viz.report(saveStates[i]);
}
} catch (const std::exception& e) {
cout << "EXCEPTION: " << e.what() << "\n";
}
}
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