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/* -------------------------------------------------------------------------- *
* Simbody(tm) Example: SimplePlanarMechanism *
* -------------------------------------------------------------------------- *
* 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) 2012-13 Stanford University and the Authors. *
* Authors: Michael Sherman *
* Contributors: Andreas Scholz *
* *
* 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. *
* -------------------------------------------------------------------------- */
#include "Simbody.h"
using namespace SimTK;
// This very simple example builds a 3-body planar mechanism that does
// nothing but rock back and forth for 10 seconds. Note that Simbody always
// works in 3D; this mechanism is planar because of the alignment of its
// joints not because it uses any special 2D features. The mechanism looks
// like this:
// @
// @--------+--------@
// Y | | \
// | | | \
// | | | \
// /-----X * * *
// /
// Z
//
// It consists of a central T-shaped body pinned to ground, and
// two pendulum bodies pinned to either side of the T. The @'s above represent
// pin joints rotating about the Z axes. Each body's mass is concentrated into
// point masses shown by *'s above. Gravity is in the -Y direction.
//
// We'll add a joint stop on the left arm to limit its range of motion.
//
// This is the Simbody equivalent of a mechanism Andreas Scholz used to
// demonstrate features of the MOBILE code from Andrs Kecskemthy's lab.
int main() {
try { // catch errors if any
// Create the system, with subsystems for the bodies and some forces.
MultibodySystem system;
SimbodyMatterSubsystem matter(system);
GeneralForceSubsystem forces(system);
Force::Gravity gravity(forces, matter, -YAxis, 9.8);
// Describe a body with a point mass at (0, -3, 0) and draw a sphere there.
Real mass = 3; Vec3 pos(0,-3,0);
Body::Rigid bodyInfo(MassProperties(mass, pos, UnitInertia::pointMassAt(pos)));
bodyInfo.addDecoration(pos, DecorativeSphere(.2).setOpacity(.5));
// Create the tree of mobilized bodies, reusing the above body description.
MobilizedBody::Pin bodyT (matter.Ground(), Vec3(0), bodyInfo, Vec3(0));
MobilizedBody::Pin leftArm(bodyT, Vec3(-2, 0, 0), bodyInfo, Vec3(0));
MobilizedBody::Pin rtArm (bodyT, Vec3(2, 0, 0), bodyInfo, Vec3(0));
// Add a joint stop to the left arm restricting it to q in [0,Pi/5].
Force::MobilityLinearStop stop(forces, leftArm, MobilizerQIndex(0),
10000, // stiffness
0.5, // dissipation coefficient
0*Pi, // lower stop
Pi/5); // upper stop
// Ask for visualization every 1/30 second.
system.setUseUniformBackground(true); // turn off floor
system.addEventReporter(new Visualizer::Reporter(system, 1./30));
// Initialize the system and state.
State state = system.realizeTopology();
leftArm.setAngle(state, Pi/5);
// Simulate for 10 seconds.
RungeKuttaMersonIntegrator integ(system);
TimeStepper ts(system, integ);
ts.initialize(state);
ts.stepTo(10);
} catch (const std::exception& e) {
std::cout << "ERROR: " << e.what() << std::endl;
return 1;
}
return 0;
}
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