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/* -------------------------------------------------------------------------- *
* 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. *
* -------------------------------------------------------------------------- */
/* Implementation of URDFReader class. */
#include "Simbody.h"
#include "URDFReader.h"
#include <utility>
#include <string>
#include <vector>
#include <map>
#include <iostream>
using std::cout; using std::endl;
using namespace SimTK;
//==============================================================================
// AUXILIARY FUNCTIONS FOR XML READING
//==============================================================================
// Convert the given pose in x,y,z,thetax,thetay,thetaz format to a Simbody
// Transform. The rotation angles are interpreted as a body-fixed sequence,
// meaning we rotation about x, then about the new y, then about the now twice-
// rotated z.
/*static*/ Transform URDF::origin2Transform(const Vec3& xyz, const Vec3& rpy) {
Transform frame(Rotation(SimTK::BodyRotationSequence,
rpy[0], XAxis, rpy[1], YAxis, rpy[2], ZAxis),
xyz);
return frame;
}
// Convert a Simbody transform to a pose in x,y,z,thetax,thetay,thetaz format.
/*static*/ Vec6 URDF::transform2Pose(const Transform& X_AB) {
Vec6 pose;
pose.updSubVec<3>(0) = X_AB.p(); // position vector
pose.updSubVec<3>(3) = X_AB.R().convertRotationToBodyFixedXYZ();
return pose;
}
// If the given element contains an <origin> element, return it as a Transform.
// Otherwise return the identity Transform. If there is more than one <origin>
// element, only the first one is processed.
/*static*/ Transform URDF::getOrigin(Xml::Element element) {
Xml::Element org = element.getOptionalElement("origin");
if (!org.isValid()) return Transform();
const Vec3 xyz = org.getOptionalAttributeValueAs<Vec3>("xyz",Vec3(0));
const Vec3 rpy = org.getOptionalAttributeValueAs<Vec3>("rpy",Vec3(0));
return origin2Transform(xyz,rpy);
}
// Look for an <inertial> element within the given element (which is probably
// a link but we don't care). If found, parse and transform to link (body)
// frame. Otherwise return unit mass and inertia. Result is returned as a
// Simbody MassProperties element containing mass, center of mass location,
// and unit inertia about body origin.
/*static*/ MassProperties URDF::getMassProperties(Xml::Element link) {
Xml::Element inertial = link.getOptionalElement("inertial");
if (!inertial.isValid())
return MassProperties(1,Vec3(0),UnitInertia(1,1,1));
Xml::Element massElt = inertial.getOptionalElement("mass");
const Real mass = massElt.isValid()
? massElt.getRequiredAttributeValueAs<Real>("value")
: Real(1);
Transform X_LI = getOrigin(inertial); // identity if not provided
const Vec3 com_L = X_LI.p(); // vector from Lo to com, exp. in L
Xml::Element inertia = inertial.getOptionalElement("inertia");
if (mass==0 || !inertia.isValid())
return MassProperties(mass,com_L,UnitInertia(1,1,1));
// Get mass-weighted central inertia, expressed in I frame.
Inertia Ic_I(inertia.getOptionalAttributeValueAs<Real>("ixx", 1.),
inertia.getOptionalAttributeValueAs<Real>("iyy", 1.),
inertia.getOptionalAttributeValueAs<Real>("izz", 1.),
inertia.getOptionalAttributeValueAs<Real>("ixy", 0.),
inertia.getOptionalAttributeValueAs<Real>("ixz", 0.),
inertia.getOptionalAttributeValueAs<Real>("iyz", 0.));
// Re-express the central inertia from the I frame to the L frame.
Inertia Ic_L = Ic_I.reexpress(~X_LI.R()); // Ic_L=R_LI*Ic_I*R_IL
// Shift to L frame origin.
Inertia Io_L = Ic_L.shiftFromMassCenter(-com_L, mass);
return MassProperties(mass, com_L, Io_L); // converts to unit inertia
}
//==============================================================================
// IMPLEMENTATIONS OF URDF CLASSES
//==============================================================================
int URDFLinks::addLink(const URDFLinkInfo& info) {
if (name2index.find(info.name) != name2index.end())
throw std::runtime_error("URDFLinks::addLink(): Link name '"
+ info.name + " was used more than once.");
const int lx = (int)linkByIndex.size();
linkByIndex.push_back(info);
name2index[info.name] = lx;
return lx;
}
int URDFJoints::addJoint(const URDFJointInfo& info) {
if(name2index.find(info.name) != name2index.end())
throw std::runtime_error(
"URDFJoints::addJoint(): Joint name '" + info.name
+ "' was used more than once.");
const int jx = (int)jointByIndex.size();
jointByIndex.push_back(info);
name2index[info.name] = jx;
return jx;
}
void URDFRobot::readRobot(Xml::Element robotElt) {
name = robotElt.getRequiredAttributeValue("name");
X_WM = URDF::getOrigin(robotElt);
Array_<Xml::Element> linkElts = robotElt.getAllElements("link");
Array_<Xml::Element> jointElts = robotElt.getAllElements("joint");
printf("Reading robot '%s' with ground + %d links, %d joints.\n",
name.c_str(), linkElts.size(), jointElts.size());
// Create a World link, then read in the real links.
URDFLinkInfo worldLink("world");
worldLink.massProps = MassProperties(Infinity,Vec3(0),UnitInertia(1));
links.addLink(worldLink);
for (unsigned i=0; i < linkElts.size(); ++i) {
Xml::Element elt = linkElts[i];
URDFLinkInfo linfo(elt.getRequiredAttributeValue("name"));
linfo.mustBeBaseLink = elt.getOptionalElementValueAs<bool>
("must_be_base_link", false);
linfo.selfCollide = elt.getOptionalElementValueAs<bool>
("self_collide", false);
linfo.element = elt;
linfo.massProps = URDF::getMassProperties(elt);
links.addLink(linfo);
}
// Read in the joints.
for (unsigned i=0; i < jointElts.size(); ++i) {
Xml::Element elt = jointElts[i];
const std::string name = elt.getRequiredAttributeValue("name");
const std::string type = elt.getRequiredAttributeValue("type");
URDFJointInfo jinfo(name,type);
jinfo.mustBreakLoopHere = elt.getOptionalElementValueAs<bool>
("must_be_loop_joint", false);
jinfo.element = elt;
std::string child, parent;
Xml::Element cElt = elt.getRequiredElement("child");
child = cElt.getRequiredAttributeValue("link");
Xml::Element pElt = elt.getRequiredElement("parent");
parent = pElt.getRequiredAttributeValue("link");
assert(links.hasLink(parent) && links.hasLink(child));
assert(child != parent);
jinfo.parent = parent;
jinfo.child = child;
jinfo.X_CB = Transform(); // joint frame on child body
jinfo.X_PA = URDF::getOrigin(elt); // joint frame on parent body
Xml::Element limit = elt.getOptionalElement("limit");
if (limit.isValid()) {
jinfo.effort =
limit.getOptionalAttributeValueAs<Real>("effort", Infinity);
jinfo.lower =
limit.getOptionalAttributeValueAs<Real>("lower", -Infinity);
jinfo.upper =
limit.getOptionalAttributeValueAs<Real>("upper", Infinity);
jinfo.velocity =
limit.getOptionalAttributeValueAs<Real>("velocity", Infinity);
if (jinfo.lower > jinfo.upper)
throw std::runtime_error(
"URDFRobot::readRobot(): Joint name '" + name
+ "' had lower limit " + String(jinfo.lower)
+ " > upper limit " + String(jinfo.upper) + ".");
}
joints.addJoint(jinfo);
}
}
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