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[URDF] Edit loader to handle full inertia tensor.

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Previous URDF loader did not handle off-diagonal elements
in the URDF. This commit adds functionality to allow
the loading of an inertia matrix that has not already
been reduced to its principal components. It diagonalizes
the inertia matrix, tests that the values are real and
updates the inertial frame.
This commit is contained in:
Jeffrey Bingham 2016-09-10 18:05:14 -07:00
parent e5a8eb2425
commit 26a464bf0b
1 changed files with 52 additions and 12 deletions
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64
examples/Importers/ImportURDFDemo/BulletUrdfImporter.cpp
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@ -295,26 +295,66 @@ void BulletURDFImporter::getMassAndInertia(int linkIndex, btScalar& mass,btVect
if (linkPtr) if (linkPtr)
{ {
UrdfLink* link = *linkPtr; UrdfLink* link = *linkPtr;
btMatrix3x3 linkInertiaBasis;
btScalar linkMass, principalInertiaX, principalInertiaY, principalInertiaZ;
if (link->m_parentJoint==0 && m_data->m_urdfParser.getModel().m_overrideFixedBase) if (link->m_parentJoint==0 && m_data->m_urdfParser.getModel().m_overrideFixedBase)
{ {
mass = 0.f; linkMass = 0.f;
localInertiaDiagonal.setValue(0,0,0); principalInertiaX = 0.f;
principalInertiaY = 0.f;
principalInertiaZ = 0.f;
linkInertiaBasis.setIdentity();
} }
else else
{ {
mass = link->m_inertia.m_mass; linkMass = link->m_inertia.m_mass;
localInertiaDiagonal.setValue(link->m_inertia.m_ixx,link->m_inertia.m_iyy, if (link->m_inertia.m_ixy == 0.0 &&
link->m_inertia.m_izz); link->m_inertia.m_ixz == 0.0 &&
link->m_inertia.m_iyz == 0.0)
{
principalInertiaX = link->m_inertia.m_ixx;
principalInertiaY = link->m_inertia.m_iyy;
principalInertiaZ = link->m_inertia.m_izz;
linkInertiaBasis.setIdentity();
}
else
{
principalInertiaX = link->m_inertia.m_ixx;
btMatrix3x3 inertiaTensor(link->m_inertia.m_ixx, link->m_inertia.m_ixy, link->m_inertia.m_ixz,
link->m_inertia.m_ixy, link->m_inertia.m_iyy, link->m_inertia.m_iyz,
link->m_inertia.m_ixz, link->m_inertia.m_iyz, link->m_inertia.m_izz);
btScalar threshold = 1.0e-6;
int numIterations = 30;
inertiaTensor.diagonalize(linkInertiaBasis, threshold, numIterations);
principalInertiaX = inertiaTensor[0][0];
principalInertiaY = inertiaTensor[1][1];
principalInertiaZ = inertiaTensor[2][2];
}
} }
inertialFrame = link->m_inertia.m_linkLocalFrame; mass = linkMass;
if (principalInertiaX < 0 ||
principalInertiaX > (principalInertiaY + principalInertiaZ) ||
principalInertiaY < 0 ||
principalInertiaY > (principalInertiaX + principalInertiaZ) ||
principalInertiaZ < 0 ||
principalInertiaZ > (principalInertiaX + principalInertiaY))
{
b3Warning("Bad inertia tensor properties, setting inertia to zero for link: %s\n", link->m_name.c_str());
principalInertiaX = 0.f;
principalInertiaY = 0.f;
principalInertiaZ = 0.f;
linkInertiaBasis.setIdentity();
}
localInertiaDiagonal.setValue(principalInertiaX, principalInertiaY, principalInertiaZ);
inertialFrame.setOrigin(link->m_inertia.m_linkLocalFrame.getOrigin());
inertialFrame.setBasis(linkInertiaBasis * link->m_inertia.m_linkLocalFrame.getBasis());
} }
else else
{ {
mass = 1.f; mass = 1.f;
localInertiaDiagonal.setValue(1,1,1); localInertiaDiagonal.setValue(1,1,1);
inertialFrame.setIdentity(); inertialFrame.setIdentity();
} }
} }
bool BulletURDFImporter::getJointInfo(int urdfLinkIndex, btTransform& parent2joint, btTransform& linkTransformInWorld, btVector3& jointAxisInJointSpace, int& jointType, btScalar& jointLowerLimit, btScalar& jointUpperLimit, btScalar& jointDamping, btScalar& jointFriction) const bool BulletURDFImporter::getJointInfo(int urdfLinkIndex, btTransform& parent2joint, btTransform& linkTransformInWorld, btVector3& jointAxisInJointSpace, int& jointType, btScalar& jointLowerLimit, btScalar& jointUpperLimit, btScalar& jointDamping, btScalar& jointFriction) const