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Allow referencing links in nested models in LiftDrag #955

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Aug 10, 2021
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Allow referencing links in nested models in LiftDrag #955

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4167695
Allow referencing links in nested models in LiftDrag
azeey Jul 30, 2021
aa26825
Address reviewer feedback
azeey Aug 9, 2021
581fe58
Merge branch 'ign-gazebo5' into nested_references_for_systems
azeey Aug 9, 2021
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293 changes: 293 additions & 0 deletions examples/worlds/lift_drag_nested.sdf
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Original file line number Diff line number Diff line change
@@ -0,0 +1,293 @@
<?xml version="1.0" ?>
<!--
This is the same example as lift_drag.sdf but modified to show that links in
nested models can be references in the link_name parameter.

This file was adapted from osrf/gazebo/worlds/single_rotor_demo.world

Try sending commands:

ign topic -t "/model/lift_drag_demo_model/joint/rod_1_joint/cmd_force" -m ignition.msgs.Double -p "data: 0.7"

Listen to joint states:

ign topic -e -t /world/lift_drag/model/lift_drag_demo_model/joint_state

-->
<sdf version="1.8">
<world name="lift_drag">
<plugin
filename="ignition-gazebo-physics-system"
name="ignition::gazebo::systems::Physics">
</plugin>
<plugin
filename="ignition-gazebo-user-commands-system"
name="ignition::gazebo::systems::UserCommands">
</plugin>
<plugin
filename="ignition-gazebo-scene-broadcaster-system"
name="ignition::gazebo::systems::SceneBroadcaster">
</plugin>

<light type="directional" name="sun">
<cast_shadows>true</cast_shadows>
<pose>0 0 10 0 0 0</pose>
<diffuse>1 1 1 1</diffuse>
<specular>0.5 0.5 0.5 1</specular>
<attenuation>
<range>1000</range>
<constant>0.9</constant>
<linear>0.01</linear>
<quadratic>0.001</quadratic>
</attenuation>
<direction>-0.5 0.1 -0.9</direction>
</light>

<model name="ground_plane">
<static>true</static>
<link name="link">
<collision name="collision">
<geometry>
<plane>
<normal>0 0 1</normal>
<size>100 100</size>
</plane>
</geometry>
</collision>
<visual name="visual">
<geometry>
<plane>
<normal>0 0 1</normal>
<size>100 100</size>
</plane>
</geometry>
<material>
<ambient>0.8 0.8 0.8 1</ambient>
<diffuse>0.8 0.8 0.8 1</diffuse>
<specular>0.8 0.8 0.8 1</specular>
</material>
</visual>
</link>
</model>

<model name="lift_drag_demo_model">
<pose>0 0 0 0 0 0</pose>
<link name="body">
<pose>0.0 0 0.5 0 0 0</pose>
<inertial>
<pose>0.0 0.0 0.0 0.0 0.0 0.0</pose>
<inertia>
<ixx>1.8</ixx>
<ixy>0.0</ixy>
<ixz>0.0</ixz>
<iyy>1.8</iyy>
<iyz>0.0</iyz>
<izz>1.8</izz>
</inertia>
<mass>10.0</mass>
</inertial>
<collision name="collision">
<geometry>
<box>
<size>1 1 1</size>
</box>
</geometry>
<surface>
<friction>
<ode>
<mu>0.1</mu>
<mu2>0.1</mu2>
</ode>
</friction>
</surface>
</collision>
<visual name="visual">
<geometry>
<box>
<size>1 1 1</size>
</box>
</geometry>
<material>
<ambient>0.2 0.2 0.2 1.0</ambient>
<diffuse>.421 0.225 0.0 1.0</diffuse>
</material>
</visual>
</link>
<link name="rod_1">
<pose>0 0 1.25 0 0 0</pose>
<inertial>
<pose>0.0 0.0 0 0.0 0.0 0.0</pose>
<inertia>
<ixx>0.012</ixx>
<ixy>0.0</ixy>
<ixz>0.0</ixz>
<iyy>0.012</iyy>
<iyz>0.0</iyz>
<izz>0.0012</izz>
</inertia>
<mass>1.0</mass>
</inertial>
<collision name="collision">
<geometry>
<box>
<size>0.02 0.02 0.5</size>
</box>
</geometry>
</collision>
<visual name="visual">
<geometry>
<box>
<size>0.02 0.02 0.5</size>
</box>
</geometry>
<material>
<ambient>0.3 0.3 0.3 1.0</ambient>
<diffuse>.421 0.225 0.0 1.0</diffuse>
</material>
</visual>
</link>
<model name="blade_1">
<link name="link">
<pose>0 0 1.5 0.0 0 0</pose>
<inertial>
<pose>0.0 0.5 0 0.0 0.0 0.0</pose>
<inertia>
<ixx>0.0000465</ixx>
<ixy>0.0</ixy>
<ixz>0.0</ixz>
<iyy>0.0000006</iyy>
<iyz>0.0</iyz>
<izz>0.0000470</izz>
</inertia>
<mass>0.01</mass>
</inertial>
<collision name="collision">
<pose>0.0 0.5 0 0.0 0.0 0.0</pose>
<geometry>
<box>
<size>0.2 1.0 0.01</size>
</box>
</geometry>
</collision>
<visual name="visual">
<pose>0.0 0.5 0 0.0 0.0 0.0</pose>
<geometry>
<box>
<size>0.2 1.0 0.01</size>
</box>
</geometry>
<material>
<ambient>0.5 0.2 0.2 1.0</ambient>
<diffuse>.421 0.225 0.0 1.0</diffuse>
</material>
</visual>
</link>
</model>
<model name="blade_2">
<link name="link">
<pose>0 0 1.5 0.0 0 3.141593</pose>
<inertial>
<pose>0.0 0.5 0 0.0 0.0 0.0</pose>
<inertia>
<ixx>0.0000465</ixx>
<ixy>0.0</ixy>
<ixz>0.0</ixz>
<iyy>0.0000006</iyy>
<iyz>0.0</iyz>
<izz>0.0000470</izz>
</inertia>
<mass>0.01</mass>
</inertial>
<collision name="collision">
<pose>0.0 0.5 0 0.0 0.0 0.0</pose>
<geometry>
<box>
<size>0.2 1.0 0.01</size>
</box>
</geometry>
</collision>
<visual name="visual">
<pose>0.0 0.5 0 0.0 0.0 0</pose>
<geometry>
<box>
<size>0.2 1.0 0.01</size>
</box>
</geometry>
<material>
<ambient>0.2 0.5 0.2 1.0</ambient>
<diffuse>.421 0.225 0.0 1.0</diffuse>
</material>
</visual>
</link>
</model>
<joint name="rod_1_joint" type="revolute">
<parent>body</parent>
<child>rod_1</child>
<pose>0.0 0.0 0.0 0.0 0.0 0.0</pose>
<axis>
<limit>
<lower>-1e16</lower>
<upper>1e16</upper>
</limit>
<xyz>0.0 0.0 -1.0</xyz>
<dynamics>
<damping>0.0001</damping>
</dynamics>
</axis>
<physics>
<ode>
<cfm_damping>1</cfm_damping>
</ode>
</physics>
</joint>
<joint name="blade_1_joint" type="fixed">
<parent>rod_1</parent>
<child>blade_1</child>
<pose>0.0 0.0 0.0 0.0 0.0 0.0</pose>
</joint>
<joint name="blade_2_joint" type="fixed">
<parent>rod_1</parent>
<child>blade_2</child>
<pose>0.0 0.0 0.0 0.0 0.0 0.0</pose>
</joint>

<plugin
filename="ignition-gazebo-joint-state-publisher-system"
name="ignition::gazebo::systems::JointStatePublisher"></plugin>

<plugin
filename="ignition-gazebo-lift-drag-system"
name="ignition::gazebo::systems::LiftDrag">
<a0>0.1</a0>
<cla>0.1</cla>
<cda>0.001</cda>
<cma>0.0</cma>
<cp>0.0 0.5 0</cp>
<area>0.2</area>
<air_density>1.2041</air_density>
<forward>1 0 0</forward>
<upward>0 0 1</upward>
<link_name>blade_1::link</link_name>
</plugin>
<plugin
filename="ignition-gazebo-lift-drag-system"
name="ignition::gazebo::systems::LiftDrag">
<a0>0.1</a0>
<cla>0.1</cla>
<cda>0.001</cda>
<cma>0.0</cma>
<cp>0.0 0.5 0</cp>
<area>0.2</area>
<air_density>1.2041</air_density>
<forward>1 0 0</forward>
<upward>0 0 1</upward>
<link_name>blade_2::link</link_name>
</plugin>
<plugin
filename="ignition-gazebo-apply-joint-force-system"
name="ignition::gazebo::systems::ApplyJointForce">
<joint_name>rod_1_joint</joint_name>
</plugin>
</model>
</world>
</sdf>
47 changes: 41 additions & 6 deletions src/systems/lift_drag/LiftDrag.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@

#include "ignition/gazebo/components/AngularVelocity.hh"
#include "ignition/gazebo/components/Inertial.hh"
#include "ignition/gazebo/components/Joint.hh"
#include "ignition/gazebo/components/JointPosition.hh"
#include "ignition/gazebo/components/LinearVelocity.hh"
#include "ignition/gazebo/components/Link.hh"
Expand Down Expand Up @@ -172,33 +173,67 @@ void LiftDragPrivate::Load(const EntityComponentManager &_ecm,
{
sdf::ElementPtr elem = _sdf->GetElement("link_name");
auto linkName = elem->Get<std::string>();
this->linkEntity = this->model.LinkByName(_ecm, linkName);
auto entities =
entitiesFromScopedName(linkName, _ecm, this->model.Entity());

if (this->linkEntity == kNullEntity)
if (entities.empty())
{
ignerr << "Link with name[" << linkName << "] not found. "
<< "The LiftDrag will not generate forces\n";
this->validConfig = false;
return;
}
else if (entities.size() > 1)
{
ignwarn << "Multiple link entities with name[" << linkName << "] found. "
<< "Using the first one.\n";
}

this->linkEntity = *entities.begin();
if (!_ecm.EntityHasComponentType(this->linkEntity,
components::Link::typeId))
{
this->linkEntity = kNullEntity;
ignerr << "Entity with name[" << linkName << "] is not a link\n";
this->validConfig = false;
return;
}
}
else
{
ignerr << "The LiftDrag system requires the 'link_name' parameter\n";
this->validConfig = false;
return;
}


if (_sdf->HasElement("control_joint_name"))
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{
auto controlJointName = _sdf->Get<std::string>("control_joint_name");
this->controlJointEntity = this->model.JointByName(_ecm, controlJointName);
if (this->controlJointEntity == kNullEntity)
auto entities =
entitiesFromScopedName(controlJointName, _ecm, this->model.Entity());

if (entities.empty())
{
ignerr << "Joint with name[" << controlJointName << "] not found. "
<< "The LiftDrag will not generate forces\n";
this->validConfig = false;
return;
}
else if (entities.size() > 1)
{
ignerr << "Joint with name[" << controlJointName << "] does not exist.\n";
ignwarn << "Multiple joint entities with name[" << controlJointName
<< "] found. Using the first one.\n";
}
else

this->controlJointEntity = *entities.begin();
if (!_ecm.EntityHasComponentType(this->controlJointEntity,
components::Joint::typeId))
{
this->controlJointEntity = kNullEntity;
ignerr << "Entity with name[" << controlJointName << "] is not a joint\n";
this->validConfig = false;
return;
}
}

Expand Down
6 changes: 5 additions & 1 deletion src/systems/lift_drag/LiftDrag.hh
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Expand Up @@ -38,7 +38,9 @@ namespace systems
/// The following parameters are used by the system:
///
/// link_name : Name of the link affected by the group of lift/drag
/// properties.
/// properties. This can be a scoped name to reference links in
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/// nested models. \sa entitiesFromScopedName to learn more
/// about scoped names.
/// air_density : Density of the fluid this model is suspended in.
/// area : Surface area of the link.
/// a0 : The initial "alpha" or initial angle of attack. a0 is also
Expand All @@ -59,6 +61,8 @@ namespace systems
/// coefficient curve.
/// cda_stall : The ratio of coefficient of drag and alpha slope after
/// stall.
/// control_joint_name: Name of joint that actuates a control surface for this
/// lifting body (Optional)
class LiftDrag
: public System,
public ISystemConfigure,
Expand Down
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