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ODEJoint.cc
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/*
* Copyright (C) 2012 Open Source Robotics Foundation
*
* 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 <boost/bind/bind.hpp>
#include "gazebo/common/Exception.hh"
#include "gazebo/common/Console.hh"
#include "gazebo/common/Assert.hh"
#include "gazebo/physics/World.hh"
#include "gazebo/physics/Link.hh"
#include "gazebo/physics/PhysicsEngine.hh"
#include "gazebo/physics/ode/ODELink.hh"
#include "gazebo/physics/ode/ODEJoint.hh"
#include "gazebo/physics/GearboxJoint.hh"
#include "gazebo/physics/ScrewJoint.hh"
#include "gazebo/physics/JointWrench.hh"
// Needed for fixing issue 2430
#include "gazebo/physics/ode/ODEHingeJoint.hh"
using namespace gazebo;
using namespace physics;
//////////////////////////////////////////////////
ODEJoint::ODEJoint(BasePtr _parent)
: Joint(_parent)
{
this->jointId = nullptr;
this->implicitDampingState[0] = ODEJoint::NONE;
this->implicitDampingState[1] = ODEJoint::NONE;
this->stiffnessDampingInitialized = false;
this->feedback = nullptr;
this->currentKd[0] = 0;
this->currentKd[1] = 0;
this->currentKp[0] = 0;
this->currentKp[1] = 0;
this->forceApplied[0] = 0;
this->forceApplied[1] = 0;
this->useImplicitSpringDamper = false;
this->stopERP = 0.0;
this->stopCFM = 0.0;
this->angleOffset[0] = 0.0;
this->angleOffset[1] = 0.0;
}
//////////////////////////////////////////////////
ODEJoint::~ODEJoint()
{
this->Fini();
}
//////////////////////////////////////////////////
void ODEJoint::Fini()
{
this->applyDamping.reset();
if (this->feedback)
delete this->feedback;
this->feedback = nullptr;
this->Detach();
if (this->jointId)
dJointDestroy(this->jointId);
this->jointId = nullptr;
Joint::Fini();
}
//////////////////////////////////////////////////
void ODEJoint::Load(sdf::ElementPtr _sdf)
{
Joint::Load(_sdf);
if (this->sdf->HasElement("physics") &&
this->sdf->GetElement("physics")->HasElement("ode"))
{
sdf::ElementPtr elem = this->sdf->GetElement("physics")->GetElement("ode");
if (elem->HasElement("implicit_spring_damper"))
{
this->useImplicitSpringDamper = elem->Get<bool>("implicit_spring_damper");
}
// initializa both axis, \todo: make cfm, erp per axis
this->stopERP = elem->GetElement("limit")->Get<double>("erp");
for (unsigned int i = 0; i < this->DOF(); ++i)
this->SetParam("stop_erp", i, this->stopERP);
// initializa both axis, \todo: make cfm, erp per axis
this->stopCFM = elem->GetElement("limit")->Get<double>("cfm");
for (unsigned int i = 0; i < this->DOF(); ++i)
this->SetParam("stop_cfm", i, this->stopCFM);
if (elem->HasElement("suspension"))
{
this->SetParam(dParamSuspensionERP,
elem->GetElement("suspension")->Get<double>("erp"));
this->SetParam(dParamSuspensionCFM,
elem->GetElement("suspension")->Get<double>("cfm"));
}
if (elem->HasElement("fudge_factor"))
this->SetParam(dParamFudgeFactor,
elem->GetElement("fudge_factor")->Get<double>());
if (elem->HasElement("cfm"))
this->SetParam("cfm", 0, elem->Get<double>("cfm"));
if (elem->HasElement("erp"))
this->SetParam("erp", 0, elem->Get<double>("erp"));
if (elem->HasElement("bounce"))
this->SetParam(dParamBounce,
elem->GetElement("bounce")->Get<double>());
if (elem->HasElement("max_force"))
this->SetParam(dParamFMax,
elem->GetElement("max_force")->Get<double>());
if (elem->HasElement("velocity"))
this->SetParam(dParamVel,
elem->GetElement("velocity")->Get<double>());
}
}
//////////////////////////////////////////////////
LinkPtr ODEJoint::GetJointLink(unsigned int _index) const
{
LinkPtr result;
if (!this->jointId)
{
gzerr << "ODE Joint ID is invalid\n";
return result;
}
if (_index == 0 || _index == 1)
{
ODELinkPtr odeLink1 = boost::static_pointer_cast<ODELink>(this->childLink);
ODELinkPtr odeLink2 = boost::static_pointer_cast<ODELink>(this->parentLink);
if (odeLink1 != nullptr &&
dJointGetBody(this->jointId, _index) == odeLink1->GetODEId())
result = this->childLink;
else if (odeLink2)
result = this->parentLink;
}
return result;
}
//////////////////////////////////////////////////
bool ODEJoint::AreConnected(LinkPtr _one, LinkPtr _two) const
{
ODELinkPtr odeLink1 = boost::dynamic_pointer_cast<ODELink>(_one);
ODELinkPtr odeLink2 = boost::dynamic_pointer_cast<ODELink>(_two);
if (odeLink1 == nullptr || odeLink2 == nullptr)
gzthrow("ODEJoint requires ODE bodies\n");
return dAreConnected(odeLink1->GetODEId(), odeLink2->GetODEId());
}
//////////////////////////////////////////////////
// child classes where appropriate
double ODEJoint::GetParam(unsigned int /*parameter*/) const
{
return 0;
}
//////////////////////////////////////////////////
void ODEJoint::Attach(LinkPtr _parent, LinkPtr _child)
{
Joint::Attach(_parent, _child);
ODELinkPtr odechild = boost::dynamic_pointer_cast<ODELink>(this->childLink);
ODELinkPtr odeparent = boost::dynamic_pointer_cast<ODELink>(this->parentLink);
if (odechild == nullptr && odeparent == nullptr)
gzthrow("ODEJoint requires at least one ODE link\n");
if (!this->jointId)
gzerr << "ODE Joint ID is invalid\n";
if (this->HasType(Base::HINGE2_JOINT) &&
(odechild == nullptr || odeparent == nullptr))
gzthrow("ODEHinge2Joint cannot be connected to the world");
if (!odechild && odeparent)
{
dJointAttach(this->jointId, 0, odeparent->GetODEId());
}
else if (odechild && !odeparent)
{
dJointAttach(this->jointId, odechild->GetODEId(), 0);
}
else if (odechild && odeparent)
{
if (this->HasType(Base::HINGE2_JOINT))
dJointAttach(this->jointId, odeparent->GetODEId(), odechild->GetODEId());
else
dJointAttach(this->jointId, odechild->GetODEId(), odeparent->GetODEId());
}
}
//////////////////////////////////////////////////
void ODEJoint::Detach()
{
auto odeChild = boost::dynamic_pointer_cast<ODELink>(this->childLink);
auto odeParent = boost::dynamic_pointer_cast<ODELink>(this->parentLink);
Joint::Detach();
this->childLink.reset();
this->parentLink.reset();
// By the time we get here, links and ODEIds might have already been
// cleaned up
if ((odeParent == nullptr || odeParent->GetODEId() == nullptr) ||
(odeChild == nullptr || odeChild->GetODEId() == nullptr))
{
return;
}
if (this->jointId)
dJointAttach(this->jointId, 0, 0);
else
gzerr << "ODE Joint ID is invalid\n";
}
//////////////////////////////////////////////////
// where appropriate
void ODEJoint::SetParam(unsigned int /*parameter*/, double /*value*/)
{
if (this->childLink)
this->childLink->SetEnabled(true);
if (this->parentLink)
this->parentLink->SetEnabled(true);
}
//////////////////////////////////////////////////
void ODEJoint::SetERP(double _newERP)
{
this->SetParam(dParamSuspensionERP, _newERP);
}
//////////////////////////////////////////////////
double ODEJoint::GetERP()
{
return this->GetParam(dParamSuspensionERP);
}
//////////////////////////////////////////////////
void ODEJoint::SetCFM(double _newCFM)
{
this->SetParam(dParamSuspensionCFM, _newCFM);
}
//////////////////////////////////////////////////
double ODEJoint::GetCFM()
{
return this->GetParam(dParamSuspensionCFM);
}
//////////////////////////////////////////////////
dJointFeedback *ODEJoint::GetFeedback()
{
if (this->jointId)
return dJointGetFeedback(this->jointId);
else
gzerr << "ODE Joint ID is invalid\n";
return nullptr;
}
//////////////////////////////////////////////////
void ODEJoint::SetUpperLimit(const unsigned int _index, const double _limit)
{
Joint::SetUpperLimit(_index, _limit);
switch (_index)
{
case 0:
this->SetParam(dParamHiStop, _limit);
break;
case 1:
this->SetParam(dParamHiStop2, _limit);
break;
case 2:
this->SetParam(dParamHiStop3, _limit);
break;
default:
gzerr << "Invalid index[" << _index << "]\n";
};
}
//////////////////////////////////////////////////
void ODEJoint::SetLowerLimit(const unsigned int _index, const double _limit)
{
Joint::SetLowerLimit(_index, _limit);
switch (_index)
{
case 0:
this->SetParam(dParamLoStop, _limit);
break;
case 1:
this->SetParam(dParamLoStop2, _limit);
break;
case 2:
this->SetParam(dParamLoStop3, _limit);
break;
default:
gzerr << "Invalid index[" << _index << "]\n";
};
}
//////////////////////////////////////////////////
ignition::math::Vector3d ODEJoint::LinkForce(
const unsigned int _index) const
{
ignition::math::Vector3d result;
if (!this->jointId)
{
gzerr << "ODE Joint ID is invalid\n";
return result;
}
dJointFeedback *jointFeedback = dJointGetFeedback(this->jointId);
if (_index == 0)
result.Set(jointFeedback->f1[0], jointFeedback->f1[1],
jointFeedback->f1[2]);
else
result.Set(jointFeedback->f2[0], jointFeedback->f2[1],
jointFeedback->f2[2]);
return result;
}
//////////////////////////////////////////////////
ignition::math::Vector3d ODEJoint::LinkTorque(
const unsigned int _index) const
{
ignition::math::Vector3d result;
if (!this->jointId)
{
gzerr << "ODE Joint ID is invalid\n";
return result;
}
dJointFeedback *jointFeedback = dJointGetFeedback(this->jointId);
if (!jointFeedback)
{
gzerr << "Joint feedback uninitialized" << std::endl;
return result;
}
if (_index == 0)
result.Set(jointFeedback->t1[0], jointFeedback->t1[1],
jointFeedback->t1[2]);
else
result.Set(jointFeedback->t2[0], jointFeedback->t2[1],
jointFeedback->t2[2]);
return result;
}
//////////////////////////////////////////////////
void ODEJoint::SetAxis(const unsigned int _index,
const ignition::math::Vector3d &_axis)
{
}
//////////////////////////////////////////////////
bool ODEJoint::SetParam(const std::string &_key, unsigned int _index,
const boost::any &_value)
{
// Axis parameters for multi-axis joints use a group bitmask
// to identify the variable.
unsigned int group;
switch (_index)
{
case 0:
group = dParamGroup1;
break;
case 1:
group = dParamGroup2;
break;
case 2:
group = dParamGroup3;
break;
default:
gzerr << "Invalid index[" << _index << "]\n";
return false;
};
// try because boost::any_cast can throw
try
{
if (_key == "fudge_factor")
{
this->SetParam(dParamFudgeFactor, boost::any_cast<double>(_value));
}
else if (_key == "suspension_erp")
{
this->SetParam(dParamSuspensionERP, boost::any_cast<double>(_value));
}
else if (_key == "suspension_cfm")
{
this->SetParam(dParamSuspensionCFM, boost::any_cast<double>(_value));
}
else if (_key == "stop_erp")
{
this->SetParam(dParamStopERP | group, boost::any_cast<double>(_value));
}
else if (_key == "stop_cfm")
{
this->SetParam(dParamStopCFM | group, boost::any_cast<double>(_value));
}
else if (_key == "erp")
{
this->SetParam(dParamERP, boost::any_cast<double>(_value));
}
else if (_key == "cfm")
{
this->SetParam(dParamCFM, boost::any_cast<double>(_value));
}
else if (_key == "fmax")
{
this->SetParam(dParamFMax | group, boost::any_cast<double>(_value));
}
else if (_key == "friction")
{
// To represent Coulomb friction,
// set FMax to friction value
// set Vel to 0
this->SetParam(group | dParamFMax, boost::any_cast<double>(_value));
this->SetParam(group | dParamVel, 0.0);
}
else if (_key == "vel")
{
this->SetParam(dParamVel | group, boost::any_cast<double>(_value));
}
else if (_key == "hi_stop")
{
this->SetParam(dParamHiStop | group, boost::any_cast<double>(_value));
}
else if (_key == "lo_stop")
{
this->SetParam(dParamLoStop | group, boost::any_cast<double>(_value));
}
else if (_key == "thread_pitch")
{
ScrewJoint<ODEJoint>* screwJoint =
dynamic_cast<ScrewJoint<ODEJoint>* >(this);
if (screwJoint != nullptr)
{
screwJoint->SetThreadPitch(boost::any_cast<double>(_value));
}
else
{
gzerr << "Trying to set " << _key << " for non-screw joints."
<< std::endl;
return 0;
}
}
else if (_key == "gearbox_ratio")
{
GearboxJoint<ODEJoint>* gearboxJoint =
dynamic_cast<GearboxJoint<ODEJoint>* >(this);
if (gearboxJoint != nullptr)
{
gearboxJoint->SetGearboxRatio(boost::any_cast<double>(_value));
}
else
{
gzerr << "Trying to set " << _key << " for non-gearbox joints."
<< std::endl;
return 0;
}
}
else
{
gzerr << "Unable to handle joint attribute[" << _key << "]\n";
return false;
}
}
catch(const boost::bad_any_cast &e)
{
gzerr << "SetParam(" << _key << ")"
<< " boost any_cast error:" << e.what()
<< std::endl;
return false;
}
return true;
}
//////////////////////////////////////////////////
double ODEJoint::GetParam(const std::string &_key, unsigned int _index)
{
// Axis parameters for multi-axis joints use a group bitmask
// to identify the variable.
unsigned int group;
switch (_index)
{
case 0:
group = dParamGroup1;
break;
case 1:
group = dParamGroup2;
break;
case 2:
group = dParamGroup3;
break;
default:
gzerr << "Invalid index[" << _index << "]\n";
return false;
}
try
{
if (_key == "fudge_factor")
{
return this->GetParam(dParamFudgeFactor);
}
else if (_key == "suspension_erp")
{
return this->GetParam(dParamSuspensionERP);
}
else if (_key == "suspension_cfm")
{
return this->GetParam(dParamSuspensionCFM);
}
else if (_key == "stop_erp")
{
return this->GetParam(dParamStopERP | group);
}
else if (_key == "stop_cfm")
{
return this->GetParam(dParamStopCFM | group);
}
else if (_key == "erp")
{
return this->GetParam(dParamERP);
}
else if (_key == "cfm")
{
return this->GetParam(dParamCFM);
}
else if (_key == "fmax")
{
return this->GetParam(dParamFMax | group);
}
else if (_key == "friction")
{
return this->GetParam(dParamFMax | group);
}
else if (_key == "vel")
{
return this->GetParam(dParamVel | group);
}
else if (_key == "hi_stop")
{
return this->GetParam(dParamHiStop | group);
}
else if (_key == "lo_stop")
{
return this->GetParam(dParamLoStop | group);
}
else if (_key == "thread_pitch")
{
ScrewJoint<ODEJoint>* screwJoint =
dynamic_cast<ScrewJoint<ODEJoint>* >(this);
if (screwJoint != nullptr)
{
return screwJoint->GetThreadPitch();
}
else
{
gzerr << "Trying to get " << _key << " for non-screw joints."
<< std::endl;
return 0;
}
}
else if (_key == "gearbox_ratio")
{
GearboxJoint<ODEJoint>* gearboxJoint =
dynamic_cast<GearboxJoint<ODEJoint>* >(this);
if (gearboxJoint != nullptr)
{
return gearboxJoint->GetGearboxRatio();
}
else
{
gzerr << "Trying to get " << _key << " for non-gearbox joints."
<< std::endl;
return 0;
}
}
}
catch(common::Exception &e)
{
gzerr << "GetParam(" << _key << ") error:"
<< e.GetErrorStr()
<< std::endl;
return 0;
}
gzerr << "Unable to get joint attribute[" << _key << "]"
<< std::endl;
return 0;
}
//////////////////////////////////////////////////
void ODEJoint::Reset()
{
if (this->jointId)
dJointReset(this->jointId);
else
gzerr << "ODE Joint ID is invalid\n";
this->forceAppliedTime = common::Time::Zero;
Joint::Reset();
}
//////////////////////////////////////////////////
void ODEJoint::CacheForceTorque()
{
// Does nothing for now, will add when recovering pull request #1721
}
//////////////////////////////////////////////////
JointWrench ODEJoint::GetForceTorque(unsigned int /*_index*/)
{
// Note that:
// f2, t2 are the force torque measured on parent body's cg
// f1, t1 are the force torque measured on child body's cg
dJointFeedback *fb = this->GetFeedback();
if (fb)
{
// kind of backwards here, body1 (parent) corresponds go f2, t2
// and body2 (child) corresponds go f1, t1
this->wrench.body2Force.Set(fb->f1[0], fb->f1[1], fb->f1[2]);
this->wrench.body2Torque.Set(fb->t1[0], fb->t1[1], fb->t1[2]);
this->wrench.body1Force.Set(fb->f2[0], fb->f2[1], fb->f2[2]);
this->wrench.body1Torque.Set(fb->t2[0], fb->t2[1], fb->t2[2]);
// get force applied through SetForce
physics::JointWrench wrenchAppliedWorld;
if (this->HasType(physics::Base::HINGE_JOINT))
{
// rotate force into child link frame
// LocalAxis is the axis specified in parent link frame!!!
wrenchAppliedWorld.body2Torque =
this->GetForce(0u) * this->LocalAxis(0u);
// gzerr << "body2Torque [" << wrenchAppliedWorld.body2Torque
// << "] axis [" << this->LocalAxis(0u)
// << "]\n";
wrenchAppliedWorld.body1Torque = -wrenchAppliedWorld.body2Torque;
}
else if (this->HasType(physics::Base::SLIDER_JOINT))
{
// rotate force into child link frame
wrenchAppliedWorld.body2Force =
this->GetForce(0u) * this->LocalAxis(0u);
wrenchAppliedWorld.body1Force = -wrenchAppliedWorld.body2Force;
}
else if (this->HasType(physics::Base::FIXED_JOINT))
{
// no correction are necessary for fixed joint
}
else
{
/// \TODO: fix for multi-axis joints
gzerr << "force torque for joint type [" << this->GetType()
<< "] not implemented, returns false results!!\n";
}
// convert wrench from child cg location to child link frame
if (this->childLink)
{
ignition::math::Pose3d childPose = this->childLink->WorldPose();
// convert torque from about child CG to joint anchor location
// cg position specified in child link frame
ignition::math::Pose3d cgPose;
auto inertial = this->childLink->GetInertial();
if (inertial)
cgPose = inertial->Pose();
// anchorPose location of joint in child frame
// childMomentArm: from child CG to joint location in child link frame
// moment arm rotated into world frame (given feedback is in world frame)
ignition::math::Vector3d childMomentArm = childPose.Rot().RotateVector(
(this->anchorPose -
ignition::math::Pose3d(cgPose.Pos(),
ignition::math::Quaterniond::Identity)).Pos());
// gzerr << "anchor [" << anchorPose
// << "] iarm[" << this->childLink->GetInertial()->GetPose().Pos()
// << "] childMomentArm[" << childMomentArm
// << "] f1[" << this->wrench.body2Force
// << "] t1[" << this->wrench.body2Torque
// << "] fxp[" << this->wrench.body2Force.Cross(childMomentArm)
// << "]\n";
this->wrench.body2Torque += this->wrench.body2Force.Cross(childMomentArm);
// rotate resulting body2Force in world frame into link frame
this->wrench.body2Force = childPose.Rot().RotateVectorReverse(
-this->wrench.body2Force);
// rotate resulting body2Torque in world frame into link frame
this->wrench.body2Torque = childPose.Rot().RotateVectorReverse(
-this->wrench.body2Torque);
}
// convert torque from about parent CG to joint anchor location
if (this->parentLink)
{
// get child pose, or it's the inertial world if childLink is nullptr
ignition::math::Pose3d childPose;
if (this->childLink)
childPose = this->childLink->WorldPose();
else
gzerr << "missing child link, double check model.";
ignition::math::Pose3d parentPose = this->parentLink->WorldPose();
// if parent link exists, convert torque from about parent
// CG to joint anchor location
// parent cg specified in parent link frame
ignition::math::Pose3d cgPose;
auto inertial = this->parentLink->GetInertial();
if (inertial)
cgPose = inertial->Pose();
// get parent CG pose in child link frame
ignition::math::Pose3d parentCGInChildLink =
ignition::math::Pose3d(cgPose.Pos(),
ignition::math::Quaterniond::Identity) - (childPose - parentPose);
// paretnCGFrame in world frame
ignition::math::Pose3d parentCGInWorld = cgPose + parentPose;
// rotate momeent arms into world frame
ignition::math::Vector3d parentMomentArm =
parentCGInWorld.Rot().RotateVector(
(this->anchorPose - parentCGInChildLink).Pos());
// gzerr << "anchor [" << this->anchorPose
// << "] pcginc[" << parentCGInChildLink
// << "] iarm[" << cgPose
// << "] anc2pcg[" << this->anchorPose - parentCGInChildLink
// << "] parentMomentArm[" << parentMomentArm
// << "] f1[" << this->wrench.body1Force
// << "] t1[" << this->wrench.body1Torque
// << "] fxp[" << this->wrench.body1Force.Cross(parentMomentArm)
// << "]\n";
this->wrench.body1Torque +=
this->wrench.body1Force.Cross(parentMomentArm);
// rotate resulting body1Force in world frame into link frame
this->wrench.body1Force = parentPose.Rot().RotateVectorReverse(
-this->wrench.body1Force);
// rotate resulting body1Torque in world frame into link frame
this->wrench.body1Torque = parentPose.Rot().RotateVectorReverse(
-this->wrench.body1Torque);
if (!this->childLink)
{
gzlog << "Joint [" << this->GetScopedName()
<< "] with parent Link [" << this->parentLink->GetScopedName()
<< "] but no child Link. Child Link must be world.\n";
// if child link does not exist, use equal and opposite
this->wrench.body2Force = -this->wrench.body1Force;
this->wrench.body2Torque = -this->wrench.body1Torque;
// force/torque are in parent link frame, transform them into
// child link(world) frame.
auto parentToWorldTransform = this->parentLink->WorldPose();
this->wrench.body1Force =
parentToWorldTransform.Rot().RotateVector(
this->wrench.body1Force);
this->wrench.body1Torque =
parentToWorldTransform.Rot().RotateVector(
this->wrench.body1Torque);
}
}
else
{
if (!this->childLink)
{
gzerr << "Both parent and child links are invalid, abort.\n";
return JointWrench();
}
else
{
gzlog << "Joint [" << this->GetScopedName()
<< "] with child Link [" << this->childLink->GetScopedName()
<< "] but no parent Link. Parent Link must be world.\n";
// if parentLink does not exist, use equal opposite body1 wrench
this->wrench.body1Force = -this->wrench.body2Force;
this->wrench.body1Torque = -this->wrench.body2Torque;
// force/torque are in child link frame, transform them into
// parent link frame. Here, parent link is world, so zero transform.
auto childToWorldTransform = this->childLink->WorldPose();
this->wrench.body1Force =
childToWorldTransform.Rot().RotateVector(
this->wrench.body1Force);
this->wrench.body1Torque =
childToWorldTransform.Rot().RotateVector(
this->wrench.body1Torque);
}
}
this->wrench = this->wrench - wrenchAppliedWorld;
}
else
{
// forgot to set provide_feedback?
gzwarn << "GetForceTorque: forgot to set <provide_feedback>?\n";
}
return this->wrench;
}
//////////////////////////////////////////////////
bool ODEJoint::UsesImplicitSpringDamper()
{
return this->useImplicitSpringDamper;
}
//////////////////////////////////////////////////
void ODEJoint::UseImplicitSpringDamper(const bool _implicit)
{
this->useImplicitSpringDamper = _implicit;
}
//////////////////////////////////////////////////
void ODEJoint::ApplyImplicitStiffnessDamping()
{
// check if we are violating joint limits
if (this->DOF() > 2)
{
gzerr << "Incompatible joint type, DOF() = "
<< this->DOF() << " > 2\n";
return;
}
double dt = this->GetWorld()->Physics()->GetMaxStepSize();
for (unsigned int i = 0; i < this->DOF(); ++i)
{
double angle = this->Position(i);
double dAngle = 2.0 * this->GetVelocity(i) * dt;
angle += dAngle;
if ((ignition::math::equal(this->dissipationCoefficient[i], 0.0) &&
ignition::math::equal(this->stiffnessCoefficient[i], 0.0)) ||
angle >= this->upperLimit[i] ||
angle <= this->lowerLimit[i])
{
if (this->implicitDampingState[i] != ODEJoint::JOINT_LIMIT)
{
// We have hit the actual joint limit!
// turn off simulated damping by recovering cfm and erp,
// and recover joint limits
this->SetParam("stop_erp", i, this->stopERP);
this->SetParam("stop_cfm", i, this->stopCFM);
this->SetParam("hi_stop", i, this->upperLimit[i]);
this->SetParam("lo_stop", i, this->lowerLimit[i]);
this->SetParam("hi_stop", i, this->upperLimit[i]);
this->implicitDampingState[i] = ODEJoint::JOINT_LIMIT;
}
/* test to see if we can reduce jitter at joint limits
// apply spring damper explicitly if in joint limit
// this limits oscillations if spring is pushing joint
// into the limit.
{
double dampingForce = -fabs(this->dissipationCoefficient[i])
* this->GetVelocity(i);
double springForce = this->stiffnessCoefficient[i]
* (this->springReferencePosition[i] - this->Position(i));
this->SetForceImpl(i, dampingForce + springForce);
}
*/
}
else if (!ignition::math::equal(this->dissipationCoefficient[i], 0.0) ||
!ignition::math::equal(this->stiffnessCoefficient[i], 0.0))
{
double kd = fabs(this->dissipationCoefficient[i]);
double kp = this->stiffnessCoefficient[i];
/// \TODO: This bit of code involving adaptive damping
/// might be too complicated, add some more comments or simplify it.
if (this->dissipationCoefficient[i] < 0)
kd = this->ApplyAdaptiveDamping(i, kd);
// update if going into DAMPING_ACTIVE mode, or
// if current applied damping value is not the same as predicted.
if (this->implicitDampingState[i] != ODEJoint::DAMPING_ACTIVE ||
!ignition::math::equal(kd, this->currentKd[i]) ||
!ignition::math::equal(kp, this->currentKp[i]))
{
// save kp, kd applied for efficiency
this->currentKd[i] = kd;
this->currentKp[i] = kp;
// convert kp, kd to cfm, erp
double erp, cfm;
this->KpKdToCFMERP(dt, kp, kd, cfm, erp);
// add additional constraint row by fake hitting joint limit
// then, set erp and cfm to simulate viscous joint damping
this->SetParam("stop_erp", i, erp);
this->SetParam("stop_cfm", i, cfm);
this->SetParam("hi_stop", i, this->springReferencePosition[i]);
this->SetParam("lo_stop", i, this->springReferencePosition[i]);
this->SetParam("hi_stop", i, this->springReferencePosition[i]);
this->implicitDampingState[i] = ODEJoint::DAMPING_ACTIVE;
}
}
}
}
//////////////////////////////////////////////////
double ODEJoint::ApplyAdaptiveDamping(unsigned int _index,
const double _damping)
{
/// \TODO: hardcoded thresholds for now, make them params.
static double vThreshold = 0.01;
static double fThreshold = 1.0;
double f = this->GetForce(_index);
double v = this->GetVelocity(_index);
if (fabs(v) < vThreshold && fabs(f) > fThreshold)
{
// guess what the stable damping value might be based on v.
double tmpDStable = f / (v/fabs(v)*std::max(fabs(v), vThreshold));
// debug
// gzerr << "joint [" << this->GetName()
// << "] damping[" << _damping
// << "] f [" << f
// << "] v [" << v
// << "] f*v [" << f*v
// << "] f/v [" << tmpDStable
// << "] cur currentKd[" << _index
// << "] = [" << currentKd[_index] << "]\n";
// limit v(n+1)/v(n) to 2.0 by multiplying tmpDStable by 0.5
return std::max(_damping, 0.5*tmpDStable);
}
else
return _damping;
}
//////////////////////////////////////////////////
void ODEJoint::KpKdToCFMERP(const double _dt,
const double _kp, const double _kd,
double &_cfm, double &_erp)
{
/// \TODO: check for NaN cases
_erp = _dt * _kp / (_dt * _kp + _kd);
_cfm = 1.0 / (_dt * _kp + _kd);
}
//////////////////////////////////////////////////
void ODEJoint::CFMERPToKpKd(const double _dt,
const double _cfm, const double _erp,
double &_kp, double &_kd)
{
/// \TODO: check for NaN cases
_kp = _erp / (_dt * _cfm);
_kd = (1.0 - _erp) / _cfm;
}
//////////////////////////////////////////////////
void ODEJoint::SetDamping(unsigned int _index, double _damping)
{
if (_index < this->DOF())