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/* -------------------------------------------------------------------------- *
* Simbody(tm) Example: IMU Tracking *
* -------------------------------------------------------------------------- *
* 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) 2014 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. *
* -------------------------------------------------------------------------- */
/* This example shows a simple example using the Assembler for inverse
kinematics tracking where the input source is orientation observations from
an attached IMU (Inertial Measurement Unit).
*/
#include "Simbody.h"
#include <cstdio>
#include <exception>
using std::cout; using std::endl;
using namespace SimTK;
typedef SimTK::Markers::MarkerIx MarkerIx;
typedef SimTK::Markers::ObservationIx MarkerObsIx;
typedef SimTK::OrientationSensors::OSensorIx IMUIx;
typedef SimTK::OrientationSensors::ObservationIx IMUObsIx;
int main() {
try
{ // Create the system.
MultibodySystem system;
SimbodyMatterSubsystem matter(system);
GeneralForceSubsystem forces(system);
Force::Gravity gravity(forces, matter, -YAxis, 9.81);
system.setUseUniformBackground(true);
// An identity Rotation represents an IMU aligned with the body frame.
const Rotation bodyAxesIMU;
const Rotation tiltedIMU(Pi/4, ZAxis);
const Rotation torsoIMUOri = bodyAxesIMU;
const Rotation headIMUOri = tiltedIMU;
const Real mass_torso = 20, mass_head = 2;
const Vec3 hdims_torso(1,4,2), hdims_head(.3,1,.6);
const Vec3 marker_head(hdims_head[0],hdims_head[1],0); // top front
Body::Rigid torsoBody(MassProperties(mass_torso, Vec3(0),
UnitInertia::brick(hdims_torso)));
torsoBody.addDecoration(DecorativeBrick(hdims_torso).setOpacity(.4));
torsoBody.addDecoration(torsoIMUOri,
DecorativeFrame(1).setColor(Green).setLineThickness(5));
Body::Rigid headBody(MassProperties(mass_head, Vec3(0),
UnitInertia::brick(hdims_head)));
headBody.addDecoration(DecorativeBrick(hdims_head)
.setOpacity(.4).setColor(Cyan));
headBody.addDecoration(headIMUOri,
DecorativeFrame(1).setColor(Green).setLineThickness(5));
headBody.addDecoration(marker_head,
DecorativePoint().setColor(Green));
MobilizedBody::Free torso(matter.Ground(), Vec3(0,hdims_torso[1],0),
torsoBody, Vec3(0,-hdims_torso[1],0));
MobilizedBody::Ball head(torso, Vec3(0,hdims_torso[1],0),
headBody, Vec3(0,-hdims_head[1],0));
// Initialize the system and state.
State state = system.realizeTopology();
const Real Accuracy = 1e-5;
Assembler ik(system);
ik.setAccuracy(Accuracy);
//ik.setForceNumericalGradient(true);
Markers* markers = new Markers();
OrientationSensors* imus = new OrientationSensors();
ik.adoptAssemblyGoal(markers);
ik.adoptAssemblyGoal(imus);
const IMUIx torsoIMU = imus->addOSensor(torso, torsoIMUOri);
const IMUIx headIMU = imus->addOSensor(head, headIMUOri);
const MarkerIx headMarker = markers->addMarker(head, marker_head);
ik.initialize(state);
const IMUObsIx torsoObsIx = imus->getObservationIxForOSensor(torsoIMU);
const IMUObsIx headObsIx = imus->getObservationIxForOSensor(headIMU);
const MarkerObsIx headMarkerObsIx =
markers->getObservationIxForMarker(headMarker);
// Try an initial assembly to an arbitrary pose.
imus->moveOneObservation(torsoObsIx,
Rotation(SimTK::BodyRotationSequence,
Pi/8, ZAxis, Pi/8, YAxis));
imus->moveOneObservation(headObsIx,
Rotation()); // keep aligned with Ground
markers->moveOneObservation(headMarkerObsIx,
Vec3(0, 12, 0));
for (OrientationSensors::OSensorIx mx(0);
mx < imus->getNumOSensors(); ++mx)
{
printf("mx=%d ox=%d err=%g\n",
(int)mx, (int)imus->getObservationIxForOSensor(mx),
imus->findCurrentOSensorError(mx));
}
Visualizer viz(system);
// Show initial configuration
viz.report(state);
cout << "Initial state. Type any character to continue:\n";
getchar();
printf("Using accuracy=%g\n", ik.getAccuracyInUse());
ik.assemble(state);
for (OrientationSensors::OSensorIx mx(0);
mx < imus->getNumOSensors(); ++mx)
{
printf("mx=%d ox=%d err=%g\n",
(int)mx, (int)imus->getObservationIxForOSensor(mx),
imus->findCurrentOSensorError(mx));
}
viz.report(state);
cout << "ASSEMBLED CONFIGURATION\n";
cout << "Type any character to start tracking:\n";
getchar();
const double startCPU = cpuTime(), startReal = realTime();
const int NSteps = 200;
for (int iters=0; iters <= NSteps; ++iters) {
const Real slow = std::sin(2*Pi*iters/100);
const Real fast = std::sin(10*Pi*iters/100);
Rotation torsoObs(SpaceRotationSequence,
(Pi/4)*slow, ZAxis,
(Pi/2)*slow, YAxis);
Rotation headObs((Pi/8)*fast, YAxis); // shake head
Vec3 markerObs(Vec3(0,12,0) + slow*Vec3(5,0,0));
imus->moveOneObservation(torsoObsIx, torsoObs);
imus->moveOneObservation(headObsIx, headObs);
markers->moveOneObservation(headMarkerObsIx, markerObs);
ik.track();
ik.updateFromInternalState(state);
viz.report(state);
}
cout << "TRACKED " << NSteps << " steps in "
<< cpuTime()-startCPU << " CPU s, "
<< realTime()-startReal << " REAL s\n";
cout << "DONE TRACKING ...\n";
viz.report(state);
cout << "Type any character to continue:\n";
getchar();
} catch (const std::exception& e) {
std::printf("EXCEPTION THROWN: %s\n", e.what());
exit(1);
} catch (...) {
std::printf("UNKNOWN EXCEPTION THROWN\n");
exit(1);
}
return 0;
}
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