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fixed urdf<->rcs inconsistency for mimic joints #36

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fixed urdf<->rcs inconsistency for mimic joints #36

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561351a
fixed urdf<->rcs inconsistency for mimic joints
Jun 2, 2021
e932296
Merge remote-tracking branch 'origin/master' into mimic_fix
Jun 18, 2021
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33 changes: 33 additions & 0 deletions src/RcsCore/Rcs_URDFParser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -538,6 +538,12 @@ RcsJoint* parseJointURDF(xmlNode* node)
MatNd_setElementsTo(jnt->couplingFactors, 1.0);
getXMLNodePropertyDouble(mimicNode, "multiplier", jnt->couplingFactors->ele);

// Offset is optional (default: 0.0)
// We temporarily write the offset into the q_init field which will be overwritten
// with the correct value later on
jnt->q_init = 0.0;
getXMLNodePropertyDouble(mimicNode, "offset", &jnt->q_init);

RLOG(5, "Joint \"%s\" coupled to \"%s\" with factor %lf",
jnt->name, jnt->coupledJointName, *jnt->couplingFactors->ele);
}
Expand Down Expand Up @@ -1049,6 +1055,33 @@ RcsBody* RcsGraph_rootBodyFromURDFFile(const char* filename,
RCHECK_MSG(root, "Couldn't find root link in URFD model - did you "
"define a cyclic model?");

// Correct q_init of mimic joints
// Here, we assume that the offset that is read from the urdf file is stored in the q_init field.
// Urdf mimic joint computation: q = c*q_master + o (c = coupling factor, o = offset)
// Rcs mimic joint computation: q = q_init + c*(q_master - q_master_init)
// Hence, we can use the Rcs computation if we set q_init to: q_init = c*q_master_init - o
RCSBODY_TRAVERSE_BODIES(root)
{
RCSBODY_TRAVERSE_JOINTS(BODY)
{
if(JNT->coupledJointName != NULL)
{
RcsJoint* master = NULL;
for(uint idx = 0; idx < numJnts; idx++)
{
if(STREQ(jntVec[idx]->name, JNT->coupledJointName))
{
master = jntVec[idx];
break;
}
}
RCHECK(master != NULL);
RCHECK(JNT->couplingFactors->size == 1);
JNT->q_init = JNT->couplingFactors->ele[0]*master->q_init + JNT->q_init;
}
}
}

// Clean up
xmlFreeDoc(doc);
RFREE(bdyVec);
Expand Down
7 changes: 7 additions & 0 deletions src/RcsCore/Rcs_graph.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3022,6 +3022,13 @@ void RcsGraph_makeJointsConsistent(RcsGraph* self)
double q0 = RcsJoint_computeSlaveJointAngle(JNT, master->q0);
double q_init = RcsJoint_computeSlaveJointAngle(JNT, master->q_init);

if(q_min > q_max)
{
double tmp = q_min;
q_min = q_max;
q_max = tmp;
}

bool hasRange = false;

if ((JNT->q_min!=0.0) || (JNT->q_max!=0.0) || (JNT->q0!=0.0))
Expand Down