](namespaceignition_1_1gazebo_1_1components.html#aceca47c8f0c6d6434967dbde52c48111)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Sensor, class CameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a camera sensor, sdf::Camera, information.
More...

using  |  [ CanonicalLink
](namespaceignition_1_1gazebo_1_1components.html#a419e623437c49f59760c868334e7e42e)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
, class CanonicalLinkTag >
|  A component that identifies an entity as being a canonical link.  More...

using  |  [ CastShadows
](namespaceignition_1_1gazebo_1_1components.html#ada3e87c57fb688f93c78a080c3f6fb54)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
bool, class CastShadowsTag >
|  A component used to indicate that an entity casts shadows e.g. visual
entities.  More...

using  |  [ CenterOfVolume
](namespaceignition_1_1gazebo_1_1components.html#ac84839bcd9971a9dc22fad309d0513f0)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class CenterOfVolumeTag >
|  A component for an entity's center of volume. Units are in meters. The
Vector3 value indicates center of volume of an entity. The position of the
center of volume is relative to the pose of the parent entity.  More...

using  |  [ ChildLinkName
](namespaceignition_1_1gazebo_1_1components.html#abfcd47dc3830f37422e2ed24a50cf632)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class ChildLinkNameTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
|  A component used to indicate that a model is childlinkname (i.e. not


ignition::gazebo::components::IGN_GAZEBO_REGISTER_COMPONENT  |  (  |
"ign_gazebo_components.VisibilityFlags"  |  ,
---|---|---|---
|  |  [ VisibilityFlags
](namespaceignition_1_1gazebo_1_1components.html#aa20d145f223c92d7e45ca336fc89602d)
|
|  )  |  |

This component holds an entity's visibility mask (camera sensor entities)


Repositories


Sorry, something went wrong.


Don't complicate things unnecessarily... Think in the potential energy of the
mass with respect to the floor, at a height h, before the it starts falling.
One instant before the mass reaches floor level, that energy would have been
converted in KE of two sorts...

You have just to equate the initial energy with the final energy and solve for
v...


Pick a username


using [ JointVelocityReset
](namespaceignition_1_1gazebo_1_1components.html#a645f164faa613233611b2abd7e07d198)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::vector ](http://en.cppreference.com/w/cpp/container/vector.html)
<double>, class JointVelocityResetTag, [ serializers::VectorDoubleSerializer
](classignition_1_1gazebo_1_1serializers_1_1VectorDoubleSerializer.html) >
---

Joint velocities in SI units (rad/s for revolute, m/s for prismatic).


("ign_gazebo_components.Model", Model) using ModelSdf
|  A component that holds the model's SDF DOM.  More...

|  [ IGN_GAZEBO_REGISTER_COMPONENT
](namespaceignition_1_1gazebo_1_1components.html#a1a1edcb6ddc0390352ed428472697c79)
("ign_gazebo_components.Sensor", Sensor) using SensorTopic
|  Name of the transport topic where a sensor is publishing its data. For
sensors that publish on more than one topic, this will usually be the prefix
common to all topics of that sensor.  More...

|  [ IGN_GAZEBO_REGISTER_COMPONENT
](namespaceignition_1_1gazebo_1_1components.html#a3bf43832018e3cca41c4724036563dc0)
("ign_gazebo_components.WorldPose", WorldPose) using TrajectoryPose
|  A component type that contains pose, [ ignition::math::Pose3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a507d73d4a494a03691fb87691dd07215)
, information within a trajectory.  More...

|  [ IGN_GAZEBO_REGISTER_COMPONENT
](namespaceignition_1_1gazebo_1_1components.html#af96571affb1535b992753370876da0be)
("ign_gazebo_components.Collision", Collision) using CollisionElement
|  A component that holds the sdf::Collision object.  More...

|  [ IGN_GAZEBO_REGISTER_COMPONENT
](namespaceignition_1_1gazebo_1_1components.html#a0abdc3a92820b06204ee5cccce81276e)
("ign_gazebo_components.Actor", Actor) using AnimationTime
|  Time in seconds within animation being currently played.  More...

|  [ IGN_GAZEBO_REGISTER_COMPONENT
](namespaceignition_1_1gazebo_1_1components.html#a5b23724d0a0b898560b7beb678e51e0c)
("ign_gazebo_components.AnimationTime", AnimationTime) using AnimationName
|  Name of animation being currently played.  More...

##  Detailed Description


ignition::gazebo::components::IGN_GAZEBO_REGISTER_COMPONENT  |  (  |
"ign_gazebo_components.Model"  |  ,
---|---|---|---
|  |  [ Model
](namespaceignition_1_1gazebo_1_1components.html#a81c45336dd134e03c5a29b34beb293db)
|
|  )  |  |

A component that holds the model's SDF DOM.


#  Setting Velocity on Joints and Links


* [ Pricing ](/pricing)


The drop seems to be smaller but it seems to persist:


##  ◆  Sensor


Author


Another thing to consider is the object properties, like weight. Once the
object is detached, it will be subject to gravity again. So if it's very heavy
and the speed isn't that high, it would fall to the ground pretty quickly,
maybe the linear velocity won't be noticed as much then, as the gravity force
pulling it causes it to change too much?

---

All reactions


  * Aug 16, 2018
Introductory Physics Homework Help


##  ◆  DetachableJoint


[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=80&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler)


No one assigned


using [ AngularAcceleration
](namespaceignition_1_1gazebo_1_1components.html#a363a90fb093035bb960259560c80eb2d)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class AngularAccelerationTag>
---

A component type that contains angular acceleration of an entity represented
by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


using [ Altimeter
](namespaceignition_1_1gazebo_1_1components.html#aa7e9d6effc513c37e4236cbcc527204f)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class AltimeterTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains an altimeter sensor, sdf::Altimeter,
information.


  *   * __ Thread starter  EzequielSeattle
  * __ Start date  Oct 19, 2014
  * __ Tags
     [ Disc ](/tags/disc/) [ Velocity ](/tags/velocity/)


> is it the same object as [ here ](https://github.com/JenniferBuehler/gazebo-
> pkgs/blob/f4700ea772e4757ed6a0ebffb50a288dd131dcf4/gazebo_grasp_plugin/src/GazeboGraspGripper.cpp#L183)
> ?


  * [ Code  ](/JenniferBuehler/gazebo-pkgs)
  * [ Issues  9  ](/JenniferBuehler/gazebo-pkgs/issues)
  * [ Pull requests  0  ](/JenniferBuehler/gazebo-pkgs/pulls)
  * [ Actions  ](/JenniferBuehler/gazebo-pkgs/actions)
  * [ Projects  0  ](/JenniferBuehler/gazebo-pkgs/projects)
  * [ Wiki  ](/JenniferBuehler/gazebo-pkgs/wiki)
  * [ Security  ](/JenniferBuehler/gazebo-pkgs/security)
  * [ Insights  ](/JenniferBuehler/gazebo-pkgs/pulse)


##  ◆  IGN_GAZEBO_REGISTER_COMPONENT()  [5/9]


* Oct 21, 2014


using [ Inertial
](namespaceignition_1_1gazebo_1_1components.html#a01fe24873c5a974980e9fbc682dce41f)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Inertiald
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a37a9eeb96bfbfde10aa4345c92f7fde8)
, class InertialTag, [ serializers::InertialSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a680f3b18509d582dc7c0b353cfcfd90e)
>
---

This component holds an entity's inertial.


[ Physics news ](https://phys.org/physics-news/) on Phys.org


Hmmmmm I think I may just have found something which I noticed with


|  This component holds the filepath to the source from which an entity is
created. For example, it can be used to store the file path of a model's
SDFormat file.  More...

using  |  [ Static
](namespaceignition_1_1gazebo_1_1components.html#ab33648dd6e2b315da9ebc3c7825517f1)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
bool, class StaticTag >
|  A component used to indicate that a model is static (i.e. not moveable).
More...

using  |  [ Temperature
](namespaceignition_1_1gazebo_1_1components.html#ae89e126606b1edb03a5ee73e96b909c4)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Temperature
](https://ignitionrobotics.org/api/math/6.8/classignition_1_1math_1_1Temperature.html)
, class TemperatureTag >
|  A component that stores temperature data in Kelvin.  More...

using  |  [ ThermalCamera
](namespaceignition_1_1gazebo_1_1components.html#a2b4aea244b0e9f1d277c04c1ae865bfb)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Sensor, class ThermalCameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a Thermal camera sensor, sdf::Sensor,
information.  More...

using  |  [ ThreadPitch
](namespaceignition_1_1gazebo_1_1components.html#a5d971354591252162a5d84e5f5452da7)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
double, class ThreadPitchTag >
|  A component used to store the thread pitch of a screw joint.  More...

using  |  [ Transparency
](namespaceignition_1_1gazebo_1_1components.html#a24040ee76defbcd4b56dc98d48bd0f2a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
float, class TransparencyTag >
|  A component used to indicate an entity's transparency value e.g. visual
entities. Value is in the range from 0 (opaque) to 1 (transparent).  More...


Sorry, something went wrong.


ignition::gazebo::components::IGN_GAZEBO_REGISTER_COMPONENT  |  (  |
"ign_gazebo_components.AnimationTime"  |  ,
---|---|---|---
|  |  AnimationTime  |
|  )  |  |

Name of animation being currently played.


##  ◆  JointVelocity


EzequielSeattle  __


[ Need help with this question on Springs ](/threads/need-help-with-this-
question-on-springs.1060621/)


We read every piece of feedback, and take your input very seriously.


  * PID gains need to be tuned per object
  * Can under shoot or over shoot the target velocity
  * It takes multiple updates to reach the target velocity


* [ Bio/Chem Homework Help ](https://www.physicsforums.com/forums/biology-and-chemistry-homework-help.157/)


A length of thread is wrapped many times around a steel disc of mass M and
radius R, which is free to rotate around a fixed, frictionless, horizontal
axle. The end of the thread is connected to a small object of mass m. If this
small mass is held at rest and then released, how fast is it moving after it
has fallen through a vertical distance h? Express in terms of M, R, m, g, and
h. Make sure this makes sense in extreme limits of M >> m and M << m.


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Feb 3, 2019  •


* Oct 19, 2014


##  ◆  Material


[ Log in ](/login/)


__ Homework Helper


Copy link


Which seems to coincide with line 259 in ` GazeboGraspFix.cpp ` :


I've just tested this again. The velocity values while the object is moving
actually make sense (using the test setup with the Jaco mentioned above):


A component that contains the second joint axis for joints with two axes. This
is a simple wrapper around sdf::JointAxis.


using [ SlipComplianceCmd
](namespaceignition_1_1gazebo_1_1components.html#aa1dd4ff5d4c154f728c465d49b41a2fd)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::vector ](http://en.cppreference.com/w/cpp/container/vector.html)
<double>, class SlipComplianceCmdTag>
---

A component type that contains the slip compliance parameters to be set on a
collision. The 0 and 1 index values correspond to the slip compliance
parameters in friction direction 1 (fdir1) and friction direction 2 (fdir2)
respectively.


##  ◆  Model


If you have also installed+compiled my grasp-execution-pkgs, then you can test
easily on the Jaco like this:


In summary: For M >> m, the velocity will end up quite small. For m >> M, the
velocity will end up quite large. Seems intuitive. Am I on the right track?You
are on the right track. K_rot_m is the rotational kinetic energy of the mass
with respect to the floor, at a height h before the it starts falling.


Author


#  Setting Velocity on Joints


using [ ChildLinkName
](namespaceignition_1_1gazebo_1_1components.html#abfcd47dc3830f37422e2ed24a50cf632)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class ChildLinkNameTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
---

A component used to indicate that a model is childlinkname (i.e. not
moveable).


##  ◆  Volume


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Mar 5, 2019


Sorry, something went wrong.


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Feb 26, 2019


[ Register ](/login/register)


and right afterwards it starts to fall down:


##  ◆  AngularVelocityCmd


* Oct 19, 2014


[ Moment of inertia of a disc using rods as differential elements
](/threads/moment-of-inertia-of-a-disc-using-rods-as-differential-
elements.1003147/)


##  ◆  Actor


Navigation


{{ message }}


using [ Camera
](namespaceignition_1_1gazebo_1_1components.html#aceca47c8f0c6d6434967dbde52c48111)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class CameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains a camera sensor, sdf::Camera, information.


    [Msg] Velocity for link link (collision name cube1::link::collision): 0.01772 -0.008722 -0.113658, absolute val 0.115361
    [Msg] Velocity for link link (collision name cube1::link::collision): -0.033747 -0.115394 -0.134026, absolute val 0.180049
    [Msg] Velocity for link link (collision name cube1::link::collision): -0.03044 -0.101856 -1.0324, absolute val 1.03786


Author


Setting up a joint motor requires requires two calls. The first call sets the
key ` vel ` to the velocity the joint should travel at. It is meters per
second for prismatic joints and radians per second for all others. The other
call sets the key ` fmax ` . It is the maximum force or torque a joint motor
may apply during a time step. Set it larger than the force required to be at
the target velocity at the next time step. Set it smaller to apply a force
over many time steps until the velocity is reached. Stop applying force by
setting ` fmax ` back to zero.


Views


* [ Insights  Schrödinger’s Cat and the Qbit ](/threads/schroedingers-cat-and-the-qbit.1061433/ "Schrödinger’s Cat and the Qbit")


Everywhere  Threads  This forum  This thread


    // If we have an item and were commanded to release it
    _ecm.RequestRemoveEntity(this->dataPtr->joint);
    this->dataPtr->joint = kNullEntity;
    this->dataPtr->jointCreated = false;
    igndbg << "Remove joint between gripper and "
      << this->dataPtr->childItem
      << std::endl << "at time step " << _info.simTime.count() << std::endl;
  }
}
IGNITION_ADD_PLUGIN(
  mbzirc::SuctionGripperPlugin,
  ignition::gazebo::System,
  mbzirc::SuctionGripperPlugin::ISystemConfigure,
  mbzirc::SuctionGripperPlugin::ISystemPreUpdate)


using [ CanonicalLink
](namespaceignition_1_1gazebo_1_1components.html#a419e623437c49f59760c868334e7e42e)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
, class CanonicalLinkTag>
---

A component that identifies an entity as being a canonical link.


##  Homework Statement


  * Supported on all physics engines
  * Object feels the force that accellerates it
  * Does not need to lock other degrees of freedom


using [ LinearVelocity
](namespaceignition_1_1gazebo_1_1components.html#afd2bd1db481a4000cd85efe241bbf60a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class LinearVelocityTag>
---

A component type that contains linear velocity of an entity represented by [
ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


[ ![@sven-
hoek](https://avatars.githubusercontent.com/u/15048669?s=80&u=1184c86424c64f25eb98710ad8c40e72cc3fb679&v=4)
](/sven-hoek)


using [ NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
= [ std::add_lvalue_reference
](http://en.cppreference.com/w/cpp/types/add_reference.html) <void>
---

Convenient type to be used by components that don't wrap any data. I.e. they
act as tags and their presence is enough to infer something about the entity.


  2. Don't know if directly related to the issue, but currently I just pick a box up from the ground and let it go while moving to a more upright position. The absolute linvel as from your output is close to 0 when in the lower (pick up) position, goes up to ~0.3-0.35, but stays at ~0.25 when in the upright position. I realized that there is some jittering visible when zooming in.
Unfortunately, Franka Emika didn't provide a proper model for simulation,
therefore I tried to setup one myself (wanted to provide it for the Franka
Community, too, but haven't posted it in the forum yet). So the inertia values
are rather guesstimated and I wonder now, if the links of the collision model
might be too close together to end up in a jittering control behaviour. I'm
still getting to know ROS/Gazebo, so I don't know if this might be part of
this problem.


Sorry, something went wrong.


[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=80&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler)


##  ◆  ContactSensor


It persists when I reduce the release tolerance:(


Author


using [ ParentLinkName
](namespaceignition_1_1gazebo_1_1components.html#ac23e1c3d38fe3720591dc93885fbf8a6)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class ParentLinkNameTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
---

Holds the name of the entity's parent link.


Copy link


[ __ What's new  ](/whats-new/ "What's new") [ __ Search  ](/search/ "Search")


* Oct 21, 2014


##  ◆  Scene


Owner


using [ Pose
](namespaceignition_1_1gazebo_1_1components.html#ae94648628ab828a5d51ad780ea55bc7c)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
ignition::math::Pose3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a507d73d4a494a03691fb87691dd07215)
, class PoseTag>
---

A component type that contains pose, [ ignition::math::Pose3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a507d73d4a494a03691fb87691dd07215)
, information.


Replies


DetachableJointTag, [ serializers::DetachableJointInfoSerializer
](classignition_1_1gazebo_1_1serializers_1_1DetachableJointInfoSerializer.html)
>
|  A component that identifies an entity as being a detachable joint. It also
contains additional information about the joint.  More...

using  |  [ ExternalWorldWrenchCmd
](namespaceignition_1_1gazebo_1_1components.html#abe045fbc985d6dc5d6e01ff02fad96d7)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
msgs::Wrench
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Wrench.html)
, class ExternalWorldWrenchCmdTag, [ serializers::MsgSerializer
](classignition_1_1gazebo_1_1serializers_1_1MsgSerializer.html) >
|  A component type that contains the external wrench to be applied on an
entity expressed in the world frame and represented by [
ignition::msgs::Wrench
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Wrench.html)
. Currently this is used for applying wrenches on links. Although the
msg::Wrench type has a force_offset member, the value is currently ignored.
Instead, the force is applied at the link origin. The wrench uses SI units (N
for force and Nâ m for torque).  More...

using  |  [ Geometry
](namespaceignition_1_1gazebo_1_1components.html#a328ff3e2ce4d1cd4df6115390f2ece4e)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Geometry, class GeometryTag, [ serializers::GeometrySerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a12b083c5faaa8bc89d0113037c3cbf75)
>
|  This component holds an entity's geometry.  More...

using  |  [ GpuLidar
](namespaceignition_1_1gazebo_1_1components.html#addd750b2c6d8d2c32390572b3337ed19)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Sensor, class GpuLidarTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a GPU Lidar sensor, sdf::Lidar, information.
More...

using  |  [ Gravity


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websites correctly.
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](https://www.google.com/chrome/) .


The heavier the disk is, the faster it rotates. That is what your final
formula means. How can that be true?


2024 © Physics Forums, All Rights Reserved


##  ◆  JointVelocityReset


##  The Attempt at a Solution


edited


using [ Actuators
](namespaceignition_1_1gazebo_1_1components.html#a0f945cf498a7361223925d9790ab824f)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
msgs::Actuators
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Actuators.html)
, class ActuatorsTag, [ serializers::MsgSerializer
](classignition_1_1gazebo_1_1serializers_1_1MsgSerializer.html) >
---

A component type that contains a [ msgs::Actuators
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Actuators.html)
message. This is used for example, to communicate between the
MulticopterMotorModel and MulticopterVelocityControl systems.


##  1\. How do you calculate the velocity of a hanging object attached to a
disc?


= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
, class LinkTag >
|  A component that identifies an entity as being a link.  More...

using  |  [ LogicalAudioSource
](namespaceignition_1_1gazebo_1_1components.html#a9c543a6519b10ed43f788e75fe2d45a1)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
logical_audio::Source
](structignition_1_1gazebo_1_1logical__audio_1_1Source.html) , class
LogicalAudioSourceTag, [ serializers::LogicalAudioSourceSerializer
](classignition_1_1gazebo_1_1serializers_1_1LogicalAudioSourceSerializer.html)
>
|  A component that contains a logical audio source, which is represented by [
logical_audio::Source
](structignition_1_1gazebo_1_1logical__audio_1_1Source.html "Properties of a
logical audio source. A source also has a pose, which can be stored as a
component of...") .  More...

using  |  [ LogicalAudioSourcePlayInfo
](namespaceignition_1_1gazebo_1_1components.html#a5a0201d548660923d00701e4bac58a4a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
logical_audio::SourcePlayInfo
](structignition_1_1gazebo_1_1logical__audio_1_1SourcePlayInfo.html) , class
LogicalAudioSourcePlayInfoTag, [
serializers::LogicalAudioSourcePlayInfoSerializer
](classignition_1_1gazebo_1_1serializers_1_1LogicalAudioSourcePlayInfoSerializer.html)
>
|  A component that contains a logical audio source's playing information,
which is represented by [ logical_audio::SourcePlayInfo
](structignition_1_1gazebo_1_1logical__audio_1_1SourcePlayInfo.html "A
source's playing information. Useful for keeping track of when to start/stop
playing a source...") .  More...

using  |  [ LogicalCamera
](namespaceignition_1_1gazebo_1_1components.html#a3cdf41667d71e17216a5c59019a43ad7)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::ElementPtr, class LogicalCameraTag >
|  TODO(anyone) Substitute with sdf::LogicalCamera once that exists? This is


    * [ Topics ](/topics)
    * [ Trending ](/trending)
    * [ Collections ](/collections)


[ Rotational Movement of a Disc ](/threads/rotational-movement-of-a-
disc.969334/)


  * Can reach target velocity in a single update
  * Object feels the force that accellerates it
  * The exact required force is used, no under or overshooting the target velocity


##  ◆  ChildLinkName


Search


    [Msg] Velocity for link link (collision name cube1::link::collision): 0.000155 -2.5e-05 -0.00053, absolute val 0.000552371
    [Msg] Velocity for link link (collision name cube1::link::collision): -0.000159 -5.9e-05 0.000483, absolute val 0.000511539
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.000165 -4.4e-05 -0.000527, absolute val 0.000553946
    [Msg] Velocity for link link (collision name cube1::link::collision): -0.000162 5e-05 0.000531, absolute val 0.000557578
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.000849 0.000197 -0.003541, absolute val 0.00364716
    [Msg] GazeboGraspFix: Detaching cube1::link::collision from gripper JacoArm1.
    [Msg] PRE-DETACH Velocity for link link (collision name cube1::link::collision): 1.7e-05 -6e-06 8e-06, absolute val 1.92592e-05
    [Msg] POST-DETACH Velocity for link link (collision name cube1::link::collision): 1.7e-05 -6e-06 8e-06, absolute val 1.92592e-05


You can release the cube with this:


using [ LogicalAudioSourcePlayInfo
](namespaceignition_1_1gazebo_1_1components.html#a5a0201d548660923d00701e4bac58a4a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
logical_audio::SourcePlayInfo
](structignition_1_1gazebo_1_1logical__audio_1_1SourcePlayInfo.html) , class
LogicalAudioSourcePlayInfoTag, [
serializers::LogicalAudioSourcePlayInfoSerializer
](classignition_1_1gazebo_1_1serializers_1_1LogicalAudioSourcePlayInfoSerializer.html)
>
---

A component that contains a logical audio source's playing information, which
is represented by [ logical_audio::SourcePlayInfo
](structignition_1_1gazebo_1_1logical__audio_1_1SourcePlayInfo.html "A
source's playing information. Useful for keeping track of when to start/stop
playing a source...") .


##  ◆  ExternalWorldWrenchCmd


* [ Help with science project to launch a projectile ](/threads/help-with-science-project-to-launch-a-projectile.1057257/ "Help with science project to launch a projectile")


##  ◆  ParentEntity


##  Typedef Documentation


[ ![Physics Forums: Science Discussion, Homework Help,
Articles](https://www.physicsforums.com/styles/physicsforums/xenforo/logo.png)
![Physics Forums: Science Discussion, Homework Help,
Articles](https://www.physicsforums.com/styles/physicsforums/xenforo/logosmall.png)
](/)


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Mar 4, 2019


New issue


[ haruspex  ](/members/haruspex.334404/)


A component type that contains linear acceleration of an entity in the world
frame represented by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


using [ MagneticField
](namespaceignition_1_1gazebo_1_1components.html#a783cc4e30941b927b2df716133801f58)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class MagneticFieldTag>
---

Stores the 3D magnetic field in teslas.


It's quite possible I haven't considered this. Detachment is handled [ here
](https://github.com/JenniferBuehler/gazebo-
pkgs/blob/f4700ea772e4757ed6a0ebffb50a288dd131dcf4/gazebo_grasp_plugin/src/GazeboGraspGripper.cpp#L167)
\- ignore the ` USE_MODEL_ATTACH ` flag, I should remove that some time, it
was for testing. I'm not explicitly resetting velocity, but it could be that
detaching a joint from another joint with ` Joint::Detach() ` causes this. The
` fixedJoint ` is a fake joint which is added to connect the object to the
gripper while the object is attached. It would of course be possible to store
the velocity before detachment and restore it after, as a simple solution (if
detaching is the cause of the issue at all).


using [ AirPressureSensor
](namespaceignition_1_1gazebo_1_1components.html#a558e71094f07d5febe3293830a234d36)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class AirPressureSensorTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains an air pressure sensor, sdf::AirPressure,
information.


##  ◆  IGN_GAZEBO_REGISTER_COMPONENT()  [8/9]


**[ sven-hoek ](/sven-hoek) ** commented  Mar 5, 2019


Projects


[ Sign in
](/login?return_to=https%3A%2F%2Fgithub.com%2FJenniferBuehler%2Fgazebo-
pkgs%2Fissues%2F26)


ignition::gazebo::components Namespace Reference


###  Setting Velocity Using PID Controllers


##  ◆  Lidar


Sorry, something went wrong.


Copy link


  * May 16, 2021
Introductory Physics Homework Help


* [ Forums ](https://www.physicsforums.com/)


##  3\. Can the velocity of a hanging object attached to a disc be affected by
the angle at which it is hanging?


Velocity on joints can be set instantaneously using [ ` Joint::SetVelocity() `
](http://osrf-
distributions.s3.amazonaws.com/gazebo/api/7.1.0/classgazebo_1_1physics_1_1Joint.html#ae32987acf99308e4aca7f2c399f3e731)
. The velocity is achieved by moving the child link. Notice at first the top
link (child) on the gray (leftmost) joint moves while the bottom link is
stationary. The momentum of the top link causes the whole gray object to move
when the joint limit is hit.


[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=80&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler)


using [ Temperature
](namespaceignition_1_1gazebo_1_1components.html#ae89e126606b1edb03a5ee73e96b909c4)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Temperature
](https://ignitionrobotics.org/api/math/6.8/classignition_1_1math_1_1Temperature.html)
, class TemperatureTag>
---

A component that stores temperature data in Kelvin.


##  ◆  Atmosphere


##  ◆  Inertial


  * Sep 3, 2021
Introductory Physics Homework Help


* [ Insights Blog ](https://www.physicsforums.com/insights/)


##  ◆  SelfCollide


**[ sven-hoek ](/sven-hoek) ** commented  Feb 21, 2019


##  ◆  Actuators


Views


##  2\. What is the significance of the radius of the disc in calculating the
velocity?


**[ sven-hoek ](/sven-hoek) ** commented  Feb 7, 2019


##  ◆  Wind


##  ◆  IGN_GAZEBO_REGISTER_COMPONENT()  [7/9]


##  Function Documentation


Thanks for testing this!
It makes sense when this happens as the gripper open, as the conditions
change. Though I would have thought the properties are not affected with self-
collisions, and technically the object becomes part of the robot, but maybe
it's not considered the same for self-collisions.
This will require some more detailed looking into. It looks like in 1-2 weeks
I'll have some time freed up, so then I can look into this more.

---

👍  1  sven-hoek reacted with thumbs up emoji


[ JenniferBuehler ](/JenniferBuehler) /  **[ gazebo-pkgs
](/JenniferBuehler/gazebo-pkgs) ** Public


Sorry, something went wrong.


Replies


Linear velocity on links can be set with [ ` Link::SetLinearVel() `
](http://osrf-
distributions.s3.amazonaws.com/gazebo/api/7.1.0/classgazebo_1_1physics_1_1Link.html#a110267b99cacd79cd377ca8619956645)
. Angular velocity on links can be set with [ ` Link::SetAngularVel() `
](http://osrf-
distributions.s3.amazonaws.com/gazebo/api/7.1.0/classgazebo_1_1physics_1_1Link.html#a996d99f2897ebca28979b24b7f23faa1)
. Both accept a [ three dimensional vector ](http://osrf-
distributions.s3.amazonaws.com/gazebo/api/7.1.0/classgazebo_1_1math_1_1Vector3.html)
with the target linear velocity. The velocity must be expressed in the world
frame in meters per second or radians per second.


A component type that contains linear velocity seed of an entity in the world
frame represented by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
. This seed can used to generate linear velocities by applying transformations
and adding noise.


gzserver throws the lookup error at runtime, when it loads the grasp fix
plugin. That could mean that either libgazebo_grasp_fix.so isn't linked up
properly with libgazebo_version_helpers.so (but I dont' think so otherwise
you'd have the problem with the Jaco too), or libgazebo_version_helpers.so are
not in the LD_LIBRARY_PATH, or something like that (and also then, it's weird
that you don't get that with Jaco).


* Oct 22, 2014


` rosrun grasp_execution_jaco_tutorial grasp_cube_test --ungrasp `


The component wraps a [ std::vector
](http://en.cppreference.com/w/cpp/container/vector.html "STL class. ") of
size equal to the degrees of freedom of the joint.


, class LevelTag >
|  This component identifies an entity as being a level.  More...

using  |  [ LevelBuffer
](namespaceignition_1_1gazebo_1_1components.html#ab21374dd5c7bd20f14096e38d4d24bbb)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
double, class LevelBufferTag >
|  A component that holds the buffer setting of a level's geometry.  More...

using  |  [ LevelEntityNames
](namespaceignition_1_1gazebo_1_1components.html#a62ca4c8f340e8085bb727b2961b62712)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::set ](http://en.cppreference.com/w/cpp/container/set.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) >,
class LevelEntityNamesTag, [ serializers::LevelEntityNamesSerializer
](classignition_1_1gazebo_1_1serializers_1_1LevelEntityNamesSerializer.html) >
|  A component that holds a list of names of entities to be loaded in a level.
More...

using  |  [ Lidar
](namespaceignition_1_1gazebo_1_1components.html#a1193dc9d783301fd047378cbf8037278)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Sensor, class LidarTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a Lidar sensor, sdf::Lidar, information.
More...

using  |  [ Light
](namespaceignition_1_1gazebo_1_1components.html#ace2004cd1adcacef8cc16a5dd636af1a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Light, class LightTag, [ serializers::LightSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a9c3b4b9cfa738abf3ca2b304aa0cde37)
>
|  This component contains light source information. For more information on
lights, see [ SDF's Light element
](http://sdformat.org/spec?ver=1.6&elem=light) .  More...

using  |  [ LinearAcceleration
](namespaceignition_1_1gazebo_1_1components.html#acff53e757937857410e7fbb259c04549)


Yes, the velocity of a hanging object attached to a disc is directly
influenced by the angle at which it is hanging. The higher the angle, the
longer the distance the object must travel in a circular motion, resulting in
a higher velocity.


.  More...

using  |  [ AngularVelocityCmd
](namespaceignition_1_1gazebo_1_1components.html#a017199549e1159d49d0cd84b84323238)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class AngularVelocityCmdTag >
|  A component type that contains the commanded angular velocity of an entity,
in its own frame, represented by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.  More...

using  |  [ Atmosphere
](namespaceignition_1_1gazebo_1_1components.html#a26e63d8c7b48701791f78f0eacf9a345)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Atmosphere, class AtmosphereTag, [ serializers::AtmosphereSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a10a3b14186c2193df377c7245134bed2)
>
|  This component holds atmosphere properties of the world.  More...

using  |  [ AxisAlignedBox
](namespaceignition_1_1gazebo_1_1components.html#a1df47dd662e811de578a58bcb3fd29c0)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
ignition::math::AxisAlignedBox
](https://ignitionrobotics.org/api/math/6.8/classignition_1_1math_1_1AxisAlignedBox.html)
, class AxisAlignedBoxTag, [ serializers::AxisAlignedBoxSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a1c9a4c135632322e20e854fa73b90ed0)
>
|  A component type that contains axis aligned box, [
ignition::math::AxisAlignedBox
](https://ignitionrobotics.org/api/math/6.8/classignition_1_1math_1_1AxisAlignedBox.html)
, information. The axis aligned box is created from collisions in the entity.
More...

using  |  [ BatterySoC
](namespaceignition_1_1gazebo_1_1components.html#a68c8513c2b876f38fd80b17d518ec34e)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
float, class BatterySoCTag >
using  |  [ Camera


#  Setting Velocity on Links And Joints


[ ![@sven-
hoek](https://avatars.githubusercontent.com/u/15048669?s=80&u=1184c86424c64f25eb98710ad8c40e72cc3fb679&v=4)
](/sven-hoek)


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Mar 4, 2019


A component type that contains angular acceleration of an entity in the world
frame represented by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


Can you confirm this is similar on your setup, using the new versions of all
my packages? (all on master branches)

---

All reactions


](namespaceignition_1_1gazebo_1_1components.html#a4a6e54d44c9a0180ca734b18052f2042)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class PhysicsEnginePluginTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
|  Holds the physics engine shared library.  More...

using  |  [ Pose
](namespaceignition_1_1gazebo_1_1components.html#ae94648628ab828a5d51ad780ea55bc7c)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
ignition::math::Pose3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a507d73d4a494a03691fb87691dd07215)
, class PoseTag >
|  A component type that contains pose, [ ignition::math::Pose3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a507d73d4a494a03691fb87691dd07215)
, information.  More...

using  |  [ RenderEngineGuiPlugin
](namespaceignition_1_1gazebo_1_1components.html#a094e0772b8b4f571a9004c7fe27a19d8)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class RenderEngineGuiPluginTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
|  Holds the render engine gui shared library.  More...

using  |  [ RenderEngineServerPlugin
](namespaceignition_1_1gazebo_1_1components.html#ae3b67196b2a5db46df7764eb01d46386)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class RenderEngineServerPluginTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
|  Holds the render engine server shared library.  More...

using  |  [ RgbdCamera
](namespaceignition_1_1gazebo_1_1components.html#aebb9d09c6424f9fae6e63dca1f5d875d)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Sensor, class RgbdCameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a RGBD camera sensor, sdf::Camera,


](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
|  A component type that contains a magnetometer sensor, sdf::Magnetometer,
information.  More...

using  |  [ Material
](namespaceignition_1_1gazebo_1_1components.html#aa9957518360de83ea27ec05fd832684a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) <
sdf::Material, class MaterialTag, [ serializers::MaterialSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a5a885dc39b33287985b4b17edff55c48)
>
|  This component holds an entity's material.  More...

using  |  [ Model
](namespaceignition_1_1gazebo_1_1components.html#a81c45336dd134e03c5a29b34beb293db)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
, class ModelTag >
|  A component that identifies an entity as being a model.  More...

using  |  [ Name
](namespaceignition_1_1gazebo_1_1components.html#a501c2b6aeb7302e017055ef1a442faab)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class NameTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
|  This component holds an entity's name. The component has no concept of
scoped names nor does it care about uniqueness.  More...

using  |  [ NoData
](namespaceignition_1_1gazebo_1_1components.html#a1bc8946395bec54053d52820e79c5ad3)
= [ std::add_lvalue_reference
](http://en.cppreference.com/w/cpp/types/add_reference.html) < void >
|  Convenient type to be used by components that don't wrap any data. I.e.
they act as tags and their presence is enough to infer something about the
entity.  More...

using  |  [ ParentEntity
](namespaceignition_1_1gazebo_1_1components.html#a6e4fc60b44eb0e0cf7fdfee1f1b93b86)


[ Sign up
](/signup?ref_cta=Sign+up&ref_loc=header+logged+out&ref_page=%2F%3Cuser-
name%3E%2F%3Crepo-
name%3E%2Fvoltron%2Fissues_fragments%2Fissue_layout&source=header-
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[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=40&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler) [ JenniferBuehler ](/JenniferBuehler) mentioned this issue
Mar 5, 2019


using [ VisibilityFlags
](namespaceignition_1_1gazebo_1_1components.html#aa20d145f223c92d7e45ca336fc89602d)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<uint32_t, class VisibilityFlagsTag>
---

This component holds an entity's visibility flags (visual entities)


Owner


Open


The plugin seems to work pretty well but I was checking what happened, when
the gripper opens while in motion. It seems that the gripped object's velocity
is reset and falls straight down by gravity.
For example in situations, where the simulated robot is supposed to throw an
object, it would be important, that the gripped object keeps its velocity.

---

The text was updated successfully, but these errors were encountered:


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##  ◆  IGN_GAZEBO_REGISTER_COMPONENT()  [2/9]


The controllers will output forces and torques that should be applied to the
link to correct for the current error.


Copy link


  * ODE only (default physics engine used by gazebo)
  * When using to set a link's velocity all other degrees of freedom are locked


##  ◆  ContactSensorData


[ sven-hoek ](/sven-hoek) opened this issue  Feb 3, 2019  · 30 comments


**[ sven-hoek ](/sven-hoek) ** commented  Mar 4, 2019  •


using [ Lidar
](namespaceignition_1_1gazebo_1_1components.html#a1193dc9d783301fd047378cbf8037278)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class LidarTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains a Lidar sensor, sdf::Lidar, information.


**[ sven-hoek ](/sven-hoek) ** commented  Feb 5, 2019


Sorry, something went wrong.


##  ◆  PhysicsEnginePlugin


gzserver: symbol lookup error: /home/franka2/marcus_ws/devel/lib/libgazebo_grasp_fix.so: undefined symbol: _ZN6gazebo10GetPhysicsERKN5boost10shared_ptrINS_7physics5WorldEEE


##  ◆  LogicalAudioSourcePlayInfo


[ Sign up for free ](/join?source=comment-repo) **to join this conversation on
GitHub** . Already have an account? [ Sign in to comment
](/login?return_to=https%3A%2F%2Fgithub.com%2FJenniferBuehler%2Fgazebo-
pkgs%2Fissues%2F26)


Ok, I created a new workspace with your jaco packages and got similar,
reasonable results:


Password


using [ ExternalWorldWrenchCmd
](namespaceignition_1_1gazebo_1_1components.html#abe045fbc985d6dc5d6e01ff02fad96d7)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
msgs::Wrench
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Wrench.html)
, class ExternalWorldWrenchCmdTag, [ serializers::MsgSerializer
](classignition_1_1gazebo_1_1serializers_1_1MsgSerializer.html) >
---

A component type that contains the external wrench to be applied on an entity
expressed in the world frame and represented by [ ignition::msgs::Wrench
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Wrench.html)
. Currently this is used for applying wrenches on links. Although the
msg::Wrench type has a force_offset member, the value is currently ignored.
Instead, the force is applied at the link origin. The wrench uses SI units (N
for force and Nâ m for torque).


Yeah, they are: [ https://github.com/sven-hoek/franka_ros
](https://github.com/sven-hoek/franka_ros)
Just run ` roslaunch franka_gazebo franka_gazebo ` . The plugin is included on
the bottom of ` franka_description/robots/hand.xacro ` .


Name


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Feb 25, 2019  •


Cancel  Create saved search


##  ◆  IGN_GAZEBO_REGISTER_COMPONENT()  [9/9]


  * __
  * #4


[ ![@sven-
hoek](https://avatars.githubusercontent.com/u/15048669?s=80&u=1184c86424c64f25eb98710ad8c40e72cc3fb679&v=4)
](/sven-hoek)


#  Examples


__ Search titles only  __


[ JenniferBuehler ](/JenniferBuehler) added a commit that referenced this
issue  Feb 25, 2019


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Cancel  Submit feedback


ignition::gazebo::components::IGN_GAZEBO_REGISTER_COMPONENT  |  (  |
"ign_gazebo_components.Level"  |  ,
---|---|---|---
|  |  [ Level
](namespaceignition_1_1gazebo_1_1components.html#a4b54dd89230043e9339d2ce92fc3078c)
|
|  )  |  |

This component identifies an entity as being a default level.


##  ◆  Transparency


It was a minor change in the gazebo_grasp_plugin CMakeLists.txt which changed
this.


In any case, you need to set the velocity to the _link_ of your object (the
root link of all the object parts). If it doesn't have an easy to recognize
name in your SDF/URDF, then maybe give it one for testing, and make sure this
is the link you are setting the velocity to.
See also [ this tutorial ](http://gazebosim.org/tutorials?tut=set_velocity)
(section "Set Link Velocity Instantaneously").


Hmmm... maybe the velocity of links which are attached to a moving joint are
not updated, though I would have thought so. Sorry I'm being so slow on
testing this, I had too much work to get done, and tomorrow I'm going away for
a week. I still have this on my radar, and eventually I will get to test this.
Meanwhile, let me know if you find out more.


  * __
  * #5


To see all available qualifiers, see our [ documentation
](https://docs.github.com/search-github/github-code-search/understanding-
github-code-search-syntax) .


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Mar 4, 2019


Author


#  Calculating the velocity of a hanging object attached to a disc


None yet


###  Set Joint Velocity Using Joint Motors


Component<math::Vector3d, class WorldAngularAccelerationTag>


For


    [Msg] Velocity for link link (collision name cube1::link::collision): -4e-06 -1e-06 -0, absolute val 3.93345e-06
    [Msg] Velocity for link link (collision name cube1::link::collision): 1.1e-05 -5e-06 0.000106, absolute val 0.00010672
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.264903 0.357312 0.281031, absolute val 0.52614
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.33405 0.20541 0.289578, absolute val 0.487481
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.322413 -0.186705 0.287224, absolute val 0.470432
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.32949 -0.188507 0.267178, absolute val 0.464201
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.209733 -0.202451 0.193545, absolute val 0.349906


* [ The ReadME Project  GitHub community articles  ](/readme)


[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=80&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler)


##  ◆  JointPositionReset


##  API Reference


##  ◆  LinearVelocity


Hmmmm ok that's something that needs closer looking into, seems very strange.
If you increase the release tolerance (even if it's so high it will never be
released) and fully open the hand, does this steep drop still happen at some
point?


One other random try would also be to try a different physics engine (e.g. `
gazebo -e bullet ` ) to see if that's the same there.

---

All reactions


By:


using [ Static
](namespaceignition_1_1gazebo_1_1components.html#ab33648dd6e2b315da9ebc3c7825517f1)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<bool, class StaticTag>
---

A component used to indicate that a model is static (i.e. not moveable).


* [ Height of a stable droplet on a perfectly wetting surface ](/threads/height-of-a-stable-droplet-on-a-perfectly-wetting-surface.1057037/ "Height of a stable droplet on a perfectly wetting surface")


  * Jul 16, 2023
Introductory Physics Homework Help


[ Collision between asteroids ](/threads/collision-between-asteroids.1055903/)


I tried setting an arbitrary velocity at the end of ` GazeboGraspFix::Load() `
and it works without any problems. I then added an arbitrary force or velocity
after the detachment process inside ` GazeboGraspFix::OnUpdate() ` and both
also worked. This means at least, that the velocity won't be reset after this
step.
So, even though the object has a velocity right before the detachment, they
are too small to be seen or realistic. For example, I mostly got velocities
like ` (0.002224 -0.000124 0.003645) ` but sometimes something like `
(-0.01131 0.124148 0.007077) ` , which is still small but at least in
y-direction not negligible small. Maybe just noise, though.
If I find the time, I will see, whether I find a better way to get the
velocity. It seems weird, though, that the velocity is that low, which would
make some sense if it were in relation to the gripper, whereas the name `
WorldLinearVel() ` suggests, that it's in relation to the world frame.

---

All reactions


          // Hard coded gains. Tune these for your own application!
          double linear_p = 100.0;
          double linear_i = 0.0;
          double linear_d = 0.0;
          double linear_imax = 123456789.0;
          double angular_p = 100.0;
          double angular_i = 0.0;
          double angular_d = 0.0;
          double angular_imax = 123456789.0;


I appreciate every bit of work and help that you put into this and right now
this is also not my main work, so I'm also kinda slow on this. But I just
plotted the velocity of the link of the object and of the gripper (inside
Gazebo).
2 things are really weird:


using [ RgbdCamera
](namespaceignition_1_1gazebo_1_1components.html#aebb9d09c6424f9fae6e63dca1f5d875d)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class RgbdCameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains a RGBD camera sensor, sdf::Camera, information.


EzequielSeattle  __


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##  ◆  LinearVelocityCmd


using [ Actor
](namespaceignition_1_1gazebo_1_1components.html#ae68d27c14dc6e79c4c0d2e4f1124ad59)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Actor, class ActorTag, [ serializers::ActorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#afa3a1d25225b2c00e0a21a5a816c28a6)
>
---

This component contains actor source information. For more information on
actors, see [ SDF's Actor element
](http://sdformat.org/spec?ver=1.6&elem=actor) .


A component type that contains angular velocity of an entity in the world
frame represented by [ ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


Owner


    [Msg] Velocity for link link (collision name cube1::link::collision): 0.000127 0.000334 0.000235, absolute val 0.000427883
    [Msg] Velocity for link link (collision name cube1::link::collision): 8.7e-05 0.000283 0.000201, absolute val 0.000358163
    [Msg] Velocity for link link (collision name cube1::link::collision): 8e-05 -0.000419 -0.000735, absolute val 0.000849296
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.000143 -0.000386 -0.000534, absolute val 0.000674358
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.257508 0.367559 0.279731, absolute val 0.528828
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.289677 0.319544 0.284859, absolute val 0.51688
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.314252 0.273718 0.287556, absolute val 0.506325
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.329963 0.231457 0.289894, absolute val 0.496474
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.323467 0.037872 0.289916, absolute val 0.436023
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.313703 -0.123585 0.290164, absolute val 0.444835
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.315365 -0.171255 0.29009, absolute val 0.46145
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.319376 -0.182716 0.288207, absolute val 0.467386
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.324368 -0.188044 0.286177, absolute val 0.47167
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.329308 -0.189511 0.282151, absolute val 0.473252
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.327746 -0.18948 0.274998, absolute val 0.467915
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.329393 -0.188287 0.267562, absolute val 0.464264
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.331628 -0.186817 0.260241, absolute val 0.461089
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.242179 -0.202395 0.220052, absolute val 0.384756
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.214991 -0.204539 0.201868, absolute val 0.358899
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.208103 -0.201454 0.190138, absolute val 0.346472
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.206403 -0.196861 0.180527, absolute val 0.33756
    [Msg] Velocity for link link (collision name cube1::link::collision): 0.20569 -0.191597 0.17143, absolute val 0.329251


**[ sven-hoek ](/sven-hoek) ** commented  Feb 4, 2019  •


**Have a question about this project?** Sign up for a free GitHub account to
open an issue and contact its maintainers and the community.


##  ◆  CastShadows


Copy link


  EventManager &/*_eventMgr*/)
{
  if(_sdf->HasElement("parent_link"))
  {
    this->dataPtr->linkName = _sdf->Get<std::string>("parent_link");
  }
  else
  {
    ignerr << "Please specify a link name" << std::endl;
    return;
  }
  Model model(_entity);
  this->dataPtr->gripperEntity = model.LinkByName(_ecm, this->dataPtr->linkName);
  if (this->dataPtr->gripperEntity == kNullEntity)
  {
    ignerr << "Could not find link named "
      << this->dataPtr->linkName << std::endl;
    return;
  }
  if(_sdf->HasElement("contact_sensor_topic_prefix"))
  {
    auto prefix = _sdf->Get<std::string>("contact_sensor_topic_prefix");
    std::function<void(const ignition::msgs::Contacts &)> callback_01 =
      std::bind(&SuctionGripperPrivate::OnContact, this->dataPtr.get(), 0, 1,
        std::placeholders::_1);
    this->dataPtr->node.Subscribe(prefix + "/contact_sensor_01", callback_01);
    std::function<void(const ignition::msgs::Contacts &)> callback_11 =
      std::bind(&SuctionGripperPrivate::OnContact, this->dataPtr.get(), 1, 1,
        std::placeholders::_1);
    this->dataPtr->node.Subscribe(prefix + "/contact_sensor_11", callback_11);
    std::function<void(const ignition::msgs::Contacts &)> callback_21 =
      std::bind(&SuctionGripperPrivate::OnContact, this->dataPtr.get(), 2, 1,
        std::placeholders::_1);
    this->dataPtr->node.Subscribe(prefix + "/contact_sensor_21", callback_21);
    std::function<void(const ignition::msgs::Contacts &)> callback_10 =
      std::bind(&SuctionGripperPrivate::OnContact, this->dataPtr.get(), 1, 0,
        std::placeholders::_1);
    this->dataPtr->node.Subscribe(prefix + "/contact_sensor_10", callback_10);
    std::function<void(const ignition::msgs::Contacts &)> callback_12 =
      std::bind(&SuctionGripperPrivate::OnContact, this->dataPtr.get(), 1, 2,


  * Nov 20, 2021
Introductory Physics Homework Help


Search or jump to...


##  ◆  LogicalCamera


Replies


[ Edit
](https://github.com/osrf/gazebo_tutorials/blob/master/set_velocity/tutorial_7.md)
Version: 7.0


__ Homework Helper


using [ AngularVelocity
](namespaceignition_1_1gazebo_1_1components.html#a8765830e03d589bc062533bb6b1cd640)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class AngularVelocityTag>
---

A component type that contains angular velocity of an entity represented by [
ignition::math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
.


**[ sven-hoek ](/sven-hoek) ** commented  Feb 3, 2019


using [ ParentEntity
](namespaceignition_1_1gazebo_1_1components.html#a6e4fc60b44eb0e0cf7fdfee1f1b93b86)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
Entity ](namespaceignition_1_1gazebo.html#ad83694d867b0e3a9446b535b5dfd208d) ,
class ParentEntityTag>
---

This component holds an entity's parent entity.


[ ](https://github.com "GitHub") © 2024 GitHub, Inc.


* [ Precalculus Homework Help ](https://www.physicsforums.com/forums/precalculus-mathematics-homework-help.155/)


Closed


which doesn't include gazebo_version_helpers ! Though that still wouldn't
explain why it works with the Jaco, how puzzling...


The units of measurement used for the velocity of a hanging object attached to
a disc are meters per second (m/s) or kilometers per hour (km/h), depending on
the specific application and context.


###  Similar threads


Sorry, something went wrong.


##  ◆  AngularVelocity


  1. Set Instantaneous Velocity
  2. Configure a joint motor (ODE only)
  3. Create a PID controller


Author


##  ◆  RgbdCamera


Owner


##  ◆  SourceFilePath


The object is not constrained to the velocity permanently. Forces or torques
may change the speed of the object after the velocity is set. It must be set
every time step to keep the object at a constant velocity forever.


In general the velocity cannot be achieved instantaneously with a PID
controller. It must exist and be active for multiple updates to achive the
target velocity.


##  ◆  Level


using [ ContactSensorData
](namespaceignition_1_1gazebo_1_1components.html#a530ec3805091c8129b601d35b751338f)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
msgs::Contacts
](https://ignitionrobotics.org/api/msgs/6.2/classignition_1_1msgs_1_1Contacts.html)
, class ContactSensorDataTag, [ serializers::MsgSerializer
](classignition_1_1gazebo_1_1serializers_1_1MsgSerializer.html) >
---

A component type that contains a list of contacts.


using [ JointForce
](namespaceignition_1_1gazebo_1_1components.html#a1dc573543b67913400b084bde0f69112)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::vector ](http://en.cppreference.com/w/cpp/container/vector.html)
<double>, class JointForceTag, [ serializers::VectorDoubleSerializer
](classignition_1_1gazebo_1_1serializers_1_1VectorDoubleSerializer.html) >
---

Force applied to a joint in SI units (Nm for revolute, N for prismatic).


    * [ Actions  Automate any workflow  ](/features/actions)
    * [ Packages  Host and manage packages  ](/features/packages)
    * [ Security  Find and fix vulnerabilities  ](/features/security)
    * [ Codespaces  Instant dev environments  ](/features/codespaces)
    * [ Copilot  Write better code with AI  ](/features/copilot)
    * [ Code review  Manage code changes  ](/features/code-review)
    * [ Issues  Plan and track work  ](/features/issues)
    * [ Discussions  Collaborate outside of code  ](/features/discussions)


` roslaunch grasp_execution_jaco_tutorial
jaco_on_table_gazebo_objects_controlled.launch load_grasp_fix:=true `


[
![@JenniferBuehler](https://avatars.githubusercontent.com/u/12842634?s=80&u=c4f3910a93a4f048638fcf101ad78f41d509d516&v=4)
](/JenniferBuehler)


Open


using [ Gravity
](namespaceignition_1_1gazebo_1_1components.html#aa2703540998ff2cc7c6ec4859ecbe882)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
math::Vector3d
](https://ignitionrobotics.org/api/math/6.8/namespaceignition_1_1math.html#a1f05093f5ee1a9ecdd54476792e4c206)
, class GravityTag>
---

Store the gravity acceleration.


**[ sven-hoek ](/sven-hoek) ** commented  Feb 5, 2019


        std::placeholders::_1);
    this->dataPtr->node.Subscribe(prefix + "/contact_sensor_12", callback_12);
    this->dataPtr->contactPublisherCenter =
      this->dataPtr->node.Advertise<msgs::Boolean>(prefix + "/contacts/center");
    this->dataPtr->contactPublisherLeft =
      this->dataPtr->node.Advertise<msgs::Boolean>(prefix + "/contacts/left");
    this->dataPtr->contactPublisherRight =
      this->dataPtr->node.Advertise<msgs::Boolean>(prefix + "/contacts/right");
    this->dataPtr->contactPublisherTop =
      this->dataPtr->node.Advertise<msgs::Boolean>(prefix + "/contacts/top");
    this->dataPtr->contactPublisherBottom =
      this->dataPtr->node.Advertise<msgs::Boolean>(prefix + "/contacts/bottom");
  }
  else
  {
    ignerr << "Please specify a contact_sensor_topic_prefix" << std::endl;
    return;
  }
  if(_sdf->HasElement("command_topic"))
  {
    auto topic = _sdf->Get<std::string>("command_topic");
    this->dataPtr->node.Subscribe(
      topic,
      &SuctionGripperPrivate::OnCmd,
      this->dataPtr.get());
  }
  else
  {
    ignerr << "Please specify a command_topic" << std::endl;
    return;
  }
}
//////////////////////////////////////////////////
void SuctionGripperPlugin::PreUpdate(const UpdateInfo &_info,
  EntityComponentManager &_ecm)
{
  if (_info.paused) return;
  std::lock_guard<std::mutex> lock(this->dataPtr->mtx);
  msgs::Boolean contact;
  // If the gripper is engaged and holding an object, return contacts as true


Sorry, something went wrong.


##  ◆  VisibilityFlags


Another method of setting velocity is to use a [ PID controller
](https://en.wikipedia.org/wiki/PID_controller) to apply forces and torques.
It works on all physics engines, but requires tuning constants specifically
for the object being moved. Unlike the joint motor method, the other degrees
of freedom are not locked while the forces are being applied.


**[ JenniferBuehler ](/JenniferBuehler) ** commented  Mar 5, 2019


Views


using [ Atmosphere
](namespaceignition_1_1gazebo_1_1components.html#a26e63d8c7b48701791f78f0eacf9a345)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Atmosphere, class AtmosphereTag, [ serializers::AtmosphereSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a10a3b14186c2193df377c7245134bed2)
>
---

This component holds atmosphere properties of the world.


##  ◆  JointPosition


1. The velocity drops to a very small value right before detaching:


* Object doesn't "feel" a force accellerating it


using [ RenderEngineServerPlugin
](namespaceignition_1_1gazebo_1_1components.html#ae3b67196b2a5db46df7764eb01d46386)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html) < [
std::string ](http://en.cppreference.com/w/cpp/string/basic_string.html) ,
class RenderEngineServerPluginTag, [ serializers::StringSerializer
](classignition_1_1gazebo_1_1serializers_1_1StringSerializer.html) >
---

Holds the render engine server shared library.


**[ sven-hoek ](/sven-hoek) ** commented  Mar 4, 2019


##  Classes

---
class  |  [ BaseComponent
](classignition_1_1gazebo_1_1components_1_1BaseComponent.html)
|  Base class for all components. [ More...
](classignition_1_1gazebo_1_1components_1_1BaseComponent.html#details)

class  |  [ Component
](classignition_1_1gazebo_1_1components_1_1Component.html)
|  A component type that wraps any data type. The intention is for this class
to be used to create simple components while avoiding a lot of boilerplate
code. The Identifier must be a unique type so that type aliases can be used to
create new components. However the type does not need to be defined anywhere
eg. [ More...
](classignition_1_1gazebo_1_1components_1_1Component.html#details)

class  |  [ Component< NoData, Identifier, Serializer >
](classignition_1_1gazebo_1_1components_1_1Component_3_01NoData_00_01Identifier_00_01Serializer_01_4.html)
|  Specialization for components that don't wrap any data. This class to be
used to create simple components that represent just a "tag", while avoiding a
lot of boilerplate code. The Identifier must be a unique type so that type
aliases can be used to create new components. However the type does not need
to be defined anywhere eg. [ More...
](classignition_1_1gazebo_1_1components_1_1Component_3_01NoData_00_01Identifier_00_01Serializer_01_4.html#details)

class  |  [ ComponentDescriptor
](classignition_1_1gazebo_1_1components_1_1ComponentDescriptor.html)
|  A class for an object responsible for creating components. [ More...
](classignition_1_1gazebo_1_1components_1_1ComponentDescriptor.html#details)

class  |  [ ComponentDescriptorBase
](classignition_1_1gazebo_1_1components_1_1ComponentDescriptorBase.html)
|  A base class for an object responsible for creating components. [ More...
](classignition_1_1gazebo_1_1components_1_1ComponentDescriptorBase.html#details)

struct  |  [ DetachableJointInfo
](structignition_1_1gazebo_1_1components_1_1DetachableJointInfo.html)
|  Data structure to hold information about the parent and child links
connected by a detachable joint. [ More...


using [ DepthCamera
](namespaceignition_1_1gazebo_1_1components.html#a94b10caa2b07ce3ae68a959153d9312f)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Sensor, class DepthCameraTag, [ serializers::SensorSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a28b4f8b3bfa52760faec77e3c30686eb)
>
---

A component type that contains a depth camera sensor, sdf::Camera,
information.


* [ GitHub Sponsors  Fund open source developers  ](/sponsors)


EzequielSeattle  __


NTW


##  ◆  WorldPoseCmd


Yes, it's the same object/scope and yes, it does have velocity before. My
object is just a box, so there is only one link, which is the parent of ` obj
` . Using ` GetLink() ` unfortunately didn't change anything. I checked, if
it's really the right link.
I lowered the execution speed a lot by lowering the step size/limiting the
real time update rate and also reduced the gravity a lot. At the point of
releasing the object, it just stops abruptly.


using [ Transparency
](namespaceignition_1_1gazebo_1_1components.html#a24040ee76defbcd4b56dc98d48bd0f2a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<float, class TransparencyTag>
---

A component used to indicate an entity's transparency value e.g. visual
entities. Value is in the range from 0 (opaque) to 1 (transparent).


voko


Sorry, something went wrong.


Owner


Each degree of freedom (x, y, z, roll, pitch, yaw) must have it's own PID
controller. Fewer controllers can be used if it is permissable for the link to
move freely on some degrees of freedom. For example, setting a translational
velocity while allowing the object to rotate requries only 3 PID controllers:
x, y, z.


Like I said, I'm also mostly working on a different project but trying to make
a little progress on this issue from time to time. I'm trying to get this
running for other users who want to do throwing experiments using
reinforcement learning.
I checked, if the jittering was caused by the constant collisions of the
adjacent links by disabling the collision model for the robot links except the
gripper, but it didn't seem to change much. If I have the time, I will check
it more deeply and think of other problems that might cause issues.

---

All reactions


##  ◆  AirPressureSensor


None yet


using [ Scene
](namespaceignition_1_1gazebo_1_1components.html#ae140b2511ab1ae7f13da83718932277b)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Scene, class SceneTag, [ serializers::SceneSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a9cf98d87ce8737d589472da92b26f9f7)
>
---

This component holds scene properties of the world.


**Disadvantages**


edited


Linear velocity can be set by creating a prismatic joint between the world and
the link to be moved. Then a joint moter can be configured as described above.
The link will not rotate or move off the prismatic joint axis until the joint
is detached.


using [ Material
](namespaceignition_1_1gazebo_1_1components.html#aa9957518360de83ea27ec05fd832684a)
= [ Component ](classignition_1_1gazebo_1_1components_1_1Component.html)
<sdf::Material, class MaterialTag, [ serializers::MaterialSerializer
](namespaceignition_1_1gazebo_1_1serializers.html#a5a885dc39b33287985b4b17edff55c48)
>
---

This component holds an entity's material.


\\([2.025, 2.475]\\)

3


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A conversion from [ geometry_msgs/Twist
](http://docs.ros.org/en/melodic/api/geometry_msgs/html/msg/Twist.html)
messages to Ackermann inputs is provided.

Note


**[ harderthan ](/harderthan) ** commented  Dec 14, 2021


* [ tricycle ](/questions/scope:all/sort:activity-desc/tags:tricycle/page:1/)


You signed in with another tab or window. [ Reload ]() to refresh your
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Asked: ** 2022-05-10 20:59:10 -0500  **


* [ gazebo_plugin ](/questions/scope:all/sort:activity-desc/tags:gazebo_plugin/page:1/)


Copy link


**[ samehmohamed88 ](/samehmohamed88) ** commented  Jan 29, 2022


[ i am trying to load my depth cam model in gazebo,and it is falling down
immediately ](/question/28120/i-am-trying-to-load-my-depth-cam-model-in-
gazeboand-it-is-falling-down-immediately/)


[ @harderthan ](https://github.com/harderthan) please don't create a separate
repository with code copied.
The way to contribute changes and get feedback is to first fork this repo and
add a new package.


1. ` /tf  ` and ` /tf_static  `


* Open Source


[ __ tags ](/tags/) [ __ users ](/users/) [ __ badges ](/badges/)


Perform the validation tests described in  Interface Control Validation Test
and [ record a rosbag ](http://wiki.ros.org/rosbag/Commandline#rosbag_record)
of all of your topics. The linear and angular velocities of the three trial
runs recorded should be noted here:


Hello.


Name


I believe there is a bug in the tricycle plugin. I'm testing the ROS2 Galactic
version of the plugin: [ https://github.com/ros-simulation/gaz...
](https://github.com/ros-
simulation/gazebo_ros_pkgs/blob/galactic/gazebo_plugins/src/gazebo_ros_tricycle_drive.cpp)
which I believe is quite similar to the ROS1 version. For this test, I'm using
the demo of the Tricycle plugin:


Already on GitHub? [ Sign in ](/login?return_to=%2Fros-
controls%2Fros2_controllers%2Fissues%2Fnew%2Fchoose) to your account


The platform outputs a latched [ tf2_msgs/TFMessage
](http://docs.ros.org/en/jade/api/tf2_msgs/html/msg/TFMessage.html) message on
the ROS standard ` /tf_static  ` topic. This should include any fixed frames
of ROS enabled devices/sensors that are available on your platform.

|


` [ Remove resource checking not ported ros1 code ( ](/StoglRobotics-
forks/ros2_controllers/commit/2491482e8f814e63a0511a124effa6fb726b54f1 "Remove
resource checking not ported ros1 code \(#264\)") [ ros-controls#264
](https://github.com/ros-controls/ros2_controllers/issues/264) [ )
](/StoglRobotics-
forks/ros2_controllers/commit/2491482e8f814e63a0511a124effa6fb726b54f1 "Remove
resource checking not ported ros1 code \(#264\)") `


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Jump to bottom


> For ROS1 ackermann, the implementation seemed off.


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**[ DiuLaMaX ](/DiuLaMaX) ** commented  Dec 8, 2022


**[ tomlogan501 ](/tomlogan501) ** commented  Nov 8, 2021


Follow


[ ![@samehmohamed88](https://avatars.githubusercontent.com/u/2354387?s=40&v=4)
](/samehmohamed88) [ samehmohamed88 ](/samehmohamed88) mentioned this issue
Jan 26, 2022


{{ message }}


  * [ API Overview ](api_overview.html)
  * [ API Endpoints ](api_endpoints.html)


Sorry, something went wrong.


[ Streaming camera frames to python script ](/question/29259/streaming-camera-
frames-to-python-script/)


#  Search code, repositories, users, issues, pull requests...


[ ALL ](/questions/scope:all/sort:activity-desc/page:1/) [ UNANSWERED
](/questions/scope:unanswered/sort:answers-asc/page:1/)


##  Interface Control Validation Test  Â¶


* [ Simulation ](simulation.html)


3. ` /platform/odom  `


Member


Include my email address so I can be contacted


Copy link


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[ **asked 2022-05-10 20:59:10 -0500  ** ](/questions/28111/revisions/)


* [ Pricing ](/pricing)


Query


[ @Timple ](https://github.com/Timple) Reallly thank you for the feedback! I
didn't know it.


Contributor


The OEM platform outputs [ nav_msgs/Odometry
](http://docs.ros.org/en/noetic/api/nav_msgs/html/msg/Odometry.html) messages
on the ` /platform/odom  ` topic, at a minimum rate of **10 Hz** .

|


[ ![_images/onav_interface_control.png](_images/onav_interface_control.png)
](_images/onav_interface_control.png)


Seen: **360 times**


Sorry, something went wrong.


To see all available qualifiers, see our [ documentation
](https://docs.github.com/search-github/github-code-search/understanding-
github-code-search-syntax) .


[ OutdoorNav Software User Manual ](index.html) [
![](_static/clearpathlogo.png) ](http://www.clearpathrobotics.com/)


A URDF is supplied to CPR by the customer, in which the ` base_link  `
coordinate frame is defined according to the [ REP-105 base-link
](https://www.ros.org/reps/rep-0105.html#base-link) ROS standard.

|


[ ![@DiuLaMaX](https://avatars.githubusercontent.com/u/53355440?s=80&v=4)
](/DiuLaMaX)


Application Programming Interface


Angular Z [rad/s]


[ edit ](/questions/28111/edit/) [ retag ](/s/questions/28111/retag/) flag
offensive  [ close ](/questions/28111/close/) merge  delete


* [ Safety ](safety.html)


[ #345 ](https://github.com/ros-controls/ros2_controllers/pull/345)

---

All reactions


[ Waiting for service /gazebo/spawn_urdf_model. Gazebo doesn't find my model
](/question/28688/waiting-for-service-gazebospawn_urdf_model-gazebo-doesnt-
find-my-model/)


Pick a username


And, I couldn't find the information about 'front-wheel drive'.
Do you mean ` four_wheel_steering_controller ` ?

---

All reactions


Hello,


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We read every piece of feedback, and take your input very seriously.


###  Footer navigation


Do you know if there was any discussion about adding an Ackermann controller?
I'm not sure how I should contribute. Does it make sense to read and implement
all [ this design_drafts ](https://github.com/ros-
controls/roadmap/tree/master/design_drafts) ?


##  Footer


**[ bmagyar ](/bmagyar) ** commented  Jul 17, 2022


Here's my suggestion for a chain of PRs once you have most things working
(applicable to any of the controllers above):


[ enhancement  ](/ros-controls/ros2_controllers/labels/enhancement)


**[ tonynajjar ](/tonynajjar) ** commented  Jul 15, 2022


##  Related questions


[
![@tomlogan501](https://avatars.githubusercontent.com/u/56969577?s=40&u=d6c511541218546edacd2375c5495ab413dad6ba&v=4)
](/tomlogan501) [ tomlogan501 ](/tomlogan501) added the [ enhancement ](/ros-
controls/ros2_controllers/labels/enhancement) label  Nov 8, 2021


Be carefull with 'just' porting from ROS1.
For ROS1 ackermann, the implementation seemed [ off ](https://github.com/ros-
controls/ros_controllers/issues/412) .


Copy link


Member


Contents


If the platform computer is running a version of ROS2:


Open


  * Basic package structure implementing a controller that does nothing in particular, should have plugin, main header file, main cpp file, cmake properly set up, a load-controller test (see other controllers), no parameters, no subscriber or publisher
  * Add all basic subscribers and publishers, doing the least amount of activity, add basic controller documentation (see other controllers)
  * Add the implementation of the controller, subscriber callbacks and publishing to topics, add basic functional tests
  * Expose parameters and add tests that rely on setting parameters
  * Add any more tests that were not added yet
  * Add any new features by implementing the new functionality, adding parameter(s) for it and appropriate tests without changing the default behaviour _unless_ you have a very good reason to do so


[ @bmagyar ](https://github.com/bmagyar) What is the current status of
migrating Ackermann_steering_controller from ROS1 to ROS2?

---

All reactions


####  TODO


Trial #1: Linear x:  , Angular z:


[ ros-controls ](/ros-controls) /  **[ ros2_controllers ](/ros-
controls/ros2_controllers) ** Public


Please note: Gazebo requires javascript to work properly, please enable
javascript in your browser, [ here is how
](https://www.google.com/support/bin/answer.py?answer=23852)


No branches or pull requests


you can try ros2_control instead gazebo_control config, Check it out of here:
[ https://github.com/ros-controls/ros2_... ](https://github.com/ros-
controls/ros2_controllers/blob/humble/tricycle_controller/config/tricycle_drive_controller.yaml)


Projects


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None yet


The platform odometry output has less than Â±5% orientation error.

|


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Appendix A: UGV Integration


* [ gazebo-11 ](/questions/scope:all/sort:activity-desc/tags:gazebo-11/page:1/)


[ ![andrestoga gravatar
image](//www.gravatar.com/avatar/c71cc5d30f6bd0bbcd734161e7abc3c6?s=32&d=identicon&r=PG)
](/users/2914/andrestoga/)


Copy link


[ @DiuLaMaX ](https://github.com/DiuLaMaX) [ @hishambaharom
](https://github.com/hishambaharom) it's waiting for you guys to put the work
in ;)

---

All reactions


**[ hishambaharom ](/hishambaharom) ** commented  Dec 12, 2022


[ ![@samehmohamed88](https://avatars.githubusercontent.com/u/2354387?s=52&v=4)
](/samehmohamed88) [
![@bmagyar](https://avatars.githubusercontent.com/u/3524577?s=52&v=4)
](/bmagyar) [
![@Timple](https://avatars.githubusercontent.com/u/5036851?s=52&v=4)
](/Timple) [
![@harderthan](https://avatars.githubusercontent.com/u/13160765?s=52&v=4)
](/harderthan) [
![@tonynajjar](https://avatars.githubusercontent.com/u/14879660?s=52&v=4)
](/tonynajjar) [
![@DiuLaMaX](https://avatars.githubusercontent.com/u/53355440?s=52&v=4)
](/DiuLaMaX) [
![@tomlogan501](https://avatars.githubusercontent.com/u/56969577?s=52&v=4)
](/tomlogan501) [
![@hishambaharom](https://avatars.githubusercontent.com/u/113874406?s=52&v=4)
](/hishambaharom)


[ enhancement  ](/ros-controls/ros2_controllers/labels/enhancement)


Also support for front-wheel drive seems to be missing, but that might be a
new feature request.

---

All reactions


  *[
              2022-05-10 20:59:10 -0500
             ]: 2022-05-10 20:59:10 -0500
  *[
              2023-07-20 21:41:31 -0500
             ]: 2023-07-20 21:41:31 -0500
  *[
        2022-05-10 20:59:10 -0500
       ]: 2022-05-10 20:59:10 -0500
  *[
        2024-04-15 20:16:00 -0500
       ]: 2024-04-15 20:16:00 -0500


Sorry, something went wrong.


When in doubt, check the diff_drive_controller although it's not in a great
shape so if you have better ideas for some things, feel free to be smarter.
Also take a look at our contribution guidelines: [
http://control.ros.org/contributing.html
](http://control.ros.org/contributing.html)

---

👍  4  harderthan, samehmohamed88, jlblancoc, and aarjan222 reacted with thumbs
up emoji


##  Question Tools


6. raw NavSatFix data from a GPS unit (if possible).


* Product


4.5

3


Tricycle drive plugin: Impossible to control linear and angular speed at the
same time


[ ![ gravatar image]() ]() [ ]() (  2024-04-15 20:16:00 -0500  )  edit


* [ Navigation ](navigation.html)


\\(((v_{max} - v_{min})/2) \cdot [0.9, 1.1]\\)


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* [ FAQ ](faq.html)


add a comment


Development


[ @bmagyar ](https://github.com/bmagyar) are you getting the notifications on
this PR? Could you advise on how to proceed?


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    * [ Trending ](/trending)
    * [ Collections ](/collections)


The platform computer is on the 192.168.131.xxx subnet (ideally in the range
1-4).

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Trial #3: Linear x:  , Angular z:

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New issue


Example Linear X Band [m/s]

---|---|---

1


The platform outputs [ std_msgs/Bool
](http://docs.ros.org/en/noetic/api/std_msgs/html/msg/Bool.html) messages on
the ` /platform/emergency_stop  ` topic, at a minimum rate of **5 Hz** .

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      * [ Ackermann Steering Controller ](../../ackermann_steering_controller/doc/userdoc.html)
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      * [ Differential Drive Controller ](../../diff_drive_controller/doc/userdoc.html)
      * [ Steering Controllers Library ](../../steering_controllers_library/doc/userdoc.html)
      * Tricycle Controller
        * Velocity commands
        * Other features
        * Parameters
      * [ Tricycle Steering Controller ](../../tricycle_steering_controller/doc/userdoc.html)
    * [ Controllers for Manipulators and Other Robots ](../../doc/controllers_index.html#controllers-for-manipulators-and-other-robots)
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__ [ ROS2_Control: Rolling ](../../../../index.html)
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  * [ ros2_controllers ](../../doc/controllers_index.html)
  * tricycle_controller
  * [ Edit on GitHub ](https://github.com/ros-controls/ros2_controllers/blob/master/tricycle_controller/doc/userdoc.rst)
* * *
**You're reading the documentation for a development version. For the latest
released version, please have a look at[ Iron
](../../../../../iron/doc/ros2_controllers/tricycle_controller/doc/userdoc.html)
. **
#  tricycle_controller  
Controller for mobile robots with a single double-actuated wheel, including
traction and steering. An example is a tricycle robot with the actuated wheel


No one assigned


[ Physics::Joint::Position() returning incorrect values for small angles
](/question/26781/physicsjointposition-returning-incorrect-values-for-small-
angles/)


[ [SOLVED] Gazebo 11 under WSL (Windows Subsystem for Linux)
](/question/24751/solved-gazebo-11-under-wsl-windows-subsystem-for-linux/)


Timeout in milliseconds, after which input command on ` cmd_vel  ` topic is
considered staled.
Default: 500
publish_ackermann_command (bool)

Publish limited commands.
Default: false
velocity_rolling_window_size (int)

Size of the rolling window for calculation of mean velocity use in odometry.
Default: 10
Constraints:
>   * greater than 0
>
>
use_stamped_vel (bool)

Use stamp from input velocity message to calculate how old the command
actually is.
Default: true
traction.max_velocity (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.min_velocity (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.max_acceleration (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.min_acceleration (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.max_deceleration (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.min_deceleration (double)

Default: std::numeric_limits<double>::quiet_NaN()
traction.max_jerk (double)


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[ andrestoga ](/users/2914/andrestoga/)
20  ●  8  ●  9  ●  10


I create [ ackermann-steering-controller-ros2 repository
](https://github.com/harderthan/ackermann-steering-controller-ros2) and
implement a migration for ros1 [ ackermann_steering_controller
](https://github.com/ros-controls/ros_controllers/tree/noetic-
devel/ackermann_steering_controller)


I recorded a video of the behavior which you can see in the following Youtube
video:


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[ Error Code 23 Msg: FrameAttachedToGraph error ](/question/27002/error-
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#  ackermann_steering_controller  
This controller implements the kinematics with two axes and four wheels, where
the wheels on one axis are fixed (traction/drive) wheels, and the wheels on
the other axis are steerable.
The controller expects to have two commanding joints for traction, one for
each fixed wheel and two commanding joints for steering, one for each wheel.
For more details on controller’s execution and interfaces check the [ Steering
Controller Library
](../../steering_controllers_library/doc/userdoc.html#steering-controllers-
library-userdoc) .
##  Parameters  
This controller uses the [ generate_parameter_library
](https://github.com/PickNikRobotics/generate_parameter_library) to handle its
parameters.
For an exemplary parameterization see the ` test  ` folder of the controller’s
package.
Additionally to the parameters of the [ Steering Controller Library
](../../steering_controllers_library/doc/userdoc.html#parameters) , this
controller adds the following parameters:
front_wheel_track (double)

Front wheel track length. For details see: [
https://en.wikipedia.org/wiki/Wheelbase
](https://en.wikipedia.org/wiki/Wheelbase)
Default: 0.0
rear_wheel_track (double)

Rear wheel track length. For details see: [
https://en.wikipedia.org/wiki/Wheelbase
](https://en.wikipedia.org/wiki/Wheelbase)
Default: 0.0
wheelbase (double)

Distance between front and rear wheels. For details see: [
https://en.wikipedia.org/wiki/Wheelbase
](https://en.wikipedia.org/wiki/Wheelbase)
Default: 0.0
front_wheels_radius (double)

Front wheels radius.
Default: 0.0
rear_wheels_radius (double)

Rear wheels radius.
Default: 0.0


**[ bmagyar ](/bmagyar) ** commented  Dec 17, 2021  •


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Consult the [ Platform API  ](api_endpoints.html#topics-platform-api) for
detailed information on the published/subscribed platform topics.


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](/tonynajjar)


  * Trouble shooting to build
  * Add the Odometry/Velocity Calculation on ackermann_steering_controller.cpp
  * Add test codes for ackermann_steering_controller.cpp
  * Update Odometry.hpp and .cpp
  * Update documents (remarks, descriptions, etc.)
  * Add Test Code
  * PR


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Appendix B: CPR Hardware


` [ 2491482 ](/StoglRobotics-
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##  Comments


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Sort by »  [ oldest  ](/question/28111/tricycle-drive-plugin-impossible-to-
control-linear-and-angular-speed-at-the-same-time/?sort=oldest#sort-top) [
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Simulation


Hi,
I create just this topic to keep track of the transfert of those controllers
from ROS1 to ROS2.
We can discuss the main changes and the benefit to do so (new architecture,
cyclic, ...)

---

The text was updated successfully, but these errors were encountered:


* 👍  4 reactions


As you can see in the video, it is impossible to control a tricycle robot in
linear speed and angular position at the same time.


[ @bmagyar ](https://github.com/bmagyar) when the
ackermann_steering_controller support on ros2 humble

---

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#  Interface Control Requirements  Â¶


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##  Interface Control Checklist  Â¶


The platform outputs [ tf2_msgs/TFMessage
](http://docs.ros.org/en/jade/api/tf2_msgs/html/msg/TFMessage.html) messages
on the ROS standard ` /tf  ` topic, at a minimum rate of **30 Hz** .

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Has any further work been done on this issue? I also need to implement a car-
like steering controller for my current project.

---

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**[ bmagyar ](/bmagyar) ** commented  Dec 13, 2022


##  1  Answer


[ ![Gazebo logo](/upfiles/gazebo_logo_1.png) ](/questions/)


5. ` /platform/emergency_stop  ` (if available)


[ https://youtu.be/cjPqbctgsDY ](https://youtu.be/cjPqbctgsDY)


The platform computer has a velocity controller that tracks the input velocity
and outputs the resulting platform velocity on the ` /platform/cmd_vel  `
topic.

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Trial #2: Linear x:  , Angular z:


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The platform odometry output has less than Â±5% linear position error.

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