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Pr liftdrag coefficients (#690)
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* liftdrag_plugin code cleanup

* Add cd_alpha0, cm_alpha0 and cd_delta

* Remove sweep correction: already covered by velocity in Lift-Drag plane

* Deprecate controlJointRadToCL and a0

* Rename deprecated XML tags

* Make cm post-stall behavior symmetric around cm_alpha0

* Fix: post-stall drag (pitch-down stall) not properly accounted for

* Correct docstring of cp

* Plane: rename elevon to aileron, to align with mixer file. Give elements unique name.

* Plane: use new aero parameters

Co-authored-by: Pieter-Jan Dewitte <[email protected]>
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@pjdewitte
pjdewitte and Pieter-Jan Dewitte authored Jan 25, 2021
1 parent 4048ae6 commit 38224fb
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Showing 10 changed files with 198 additions and 180 deletions.
31 changes: 18 additions & 13 deletions include/liftdrag_plugin/liftdrag_plugin.h
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Expand Up @@ -72,7 +72,7 @@ namespace gazebo
/// where q (dynamic pressure) = 0.5 * rho * v^2
protected: double cma;

/// \brief angle of attack when airfoil stalls
/// \brief angle of attack when airfoil stalls, relative to alpha0
protected: double alphaStall;

/// \brief Cl-alpha rate after stall
Expand All @@ -84,9 +84,6 @@ namespace gazebo
/// \brief Cm-alpha rate after stall
protected: double cmaStall;

/// \breif Coefficient of Moment / control surface deflection angle slope
protected: double cm_delta;

/// \brief: \TODO: make a stall velocity curve
protected: double velocityStall;

Expand All @@ -104,16 +101,19 @@ namespace gazebo
/// \brief effective planeform surface area
protected: double area;

/// \brief angle of sweep
protected: double sweep;

/// \brief initial angle of attack
/// \brief angle of attack at which the lift is zero
protected: double alpha0;

/// \brief angle of attack
/// \brief Cd at zero lift (zero-lift drag coefficient)
protected: double cd_alpha0;

/// \brief Cm at zero lift (zero-lift moment coefficient)
protected: double cm_alpha0;

/// \brief angle of attack, relative to alpha0
protected: double alpha;

/// \brief center of pressure in link local coordinates
/// \brief center of pressure relative to the center of gravity of the link, in link local orientation
protected: ignition::math::Vector3d cp;

/// \brief Normally, this is taken as a direction parallel to the chord
Expand All @@ -132,9 +132,14 @@ namespace gazebo
/// this lifting body
protected: physics::JointPtr controlJoint;

/// \brief how much to change CL per radian of control surface joint
/// value.
protected: double controlJointRadToCL;
/// \brief How much to change CL per radian of control surface deflection
protected: double cl_delta;

/// \brief How much to change CD per radian of control surface deflection
protected: double cd_delta;

/// \brief How much to change CM per radian of control surface deflection
protected: double cm_delta;

/// \brief SDF for this plugin;
protected: sdf::ElementPtr sdf;
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4 changes: 2 additions & 2 deletions models/matrice_100/matrice_100.sdf.jinja
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Expand Up @@ -190,7 +190,7 @@
</joint>

<!--<plugin name="rotor_{{n}}_top_blade" filename="libLiftDragPlugin.so">-->
<!--<a0>{{rtr_a0}}</a0>-->
<!--<alpha0>{{rtr_a0}}</alpha0>-->
<!--<cla>{{rtr_cla}}</cla>-->
<!--<cda>{{rtr_cda}}</cda>-->
<!--<cma>{{rtr_cma}}</cma>-->
Expand All @@ -207,7 +207,7 @@
<!--</plugin>-->

<!--<plugin name="rotor_{{n}}_bottom_blade" filename="libLiftDragPlugin.so">-->
<!--<a0>{{rtr_a0}}</a0>-->
<!--<alpha0>{{rtr_a0}}</alpha0>-->
<!--<cla>{{rtr_cla}}</cla>-->
<!--<cda>{{rtr_cda}}</cda>-->
<!--<cma>{{rtr_cma}}</cma>-->
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2 changes: 1 addition & 1 deletion models/parachute_small/model.sdf
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Expand Up @@ -40,7 +40,7 @@
</link>

<plugin name="parachute_drag" filename="libLiftDragPlugin.so">
<a0>0</a0>
<alpha0>0</alpha0>
<cla>0</cla>
<cda>1.114</cda> <!-- Such that Cd = 1.75 at alpha = 90deg (= upright parachute) -->
<cma>0</cma>
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96 changes: 56 additions & 40 deletions models/plane/plane.sdf.jinja
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Expand Up @@ -187,7 +187,7 @@
</axis>
</joint>

<link name="left_elevon">
<link name="left_aileron">
<inertial>
<mass>0.00000001</mass>
<inertia>
Expand All @@ -200,7 +200,7 @@
</inertia>
<pose>0 0.3 0 0.00 0 0.0</pose>
</inertial>
<visual name='left_elevon_visual'>
<visual name='left_aileron_visual'>
<pose>0.07 0.0 -0.08 0.00 0 0.0</pose>
<geometry>
<mesh>
Expand All @@ -216,7 +216,7 @@
</material>
</visual>
</link>
<link name="right_elevon">
<link name="right_aileron">
<inertial>
<mass>0.00000001</mass>
<inertia>
Expand All @@ -229,7 +229,7 @@
</inertia>
<pose>0 -0.3 0 0.00 0 0.0</pose>
</inertial>
<visual name='right_elevon_visual'>
<visual name='right_aileron_visual'>
<pose>0.07 0.0 -0.08 0.00 0 0.0</pose>
<geometry>
<mesh>
Expand Down Expand Up @@ -361,9 +361,9 @@
</material>
</visual>
</link>
<joint name='left_elevon_joint' type='revolute'>
<joint name='left_aileron_joint' type='revolute'>
<parent>base_link</parent>
<child>left_elevon</child>
<child>left_aileron</child>
<pose>-0.07 0.4 0.08 0.00 0 0.0</pose>
<axis>
<xyz>0 1 0</xyz>
Expand All @@ -382,9 +382,9 @@
</ode>
</physics>
</joint>
<joint name='right_elevon_joint' type='revolute'>
<joint name='right_aileron_joint' type='revolute'>
<parent>base_link</parent>
<child>right_elevon</child>
<child>right_aileron</child>
<pose>-0.07 -0.4 0.08 0.00 0 0.0</pose>
<axis>
<xyz>0 1 0</xyz>
Expand Down Expand Up @@ -496,11 +496,13 @@
<child>gps::link</child>
<parent>base_link</parent>
</joint>
<plugin name="left_wing" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<plugin name="left_wing_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>-0.009519322</alpha0>
<cd_alpha0>0.003</cd_alpha0>
<cm_alpha0>0.002072715</cm_alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
<cda>0.35</cda>
<cma>0.02</cma>
<alpha_stall>0.3391428111</alpha_stall>
<cla_stall>-3.85</cla_stall>
<cda_stall>-0.9233984055</cda_stall>
Expand All @@ -512,17 +514,21 @@
<upward>0 0 1</upward>
<link_name>base_link</link_name>
<control_joint_name>
left_elevon_joint
left_aileron_joint
</control_joint_name>
<control_joint_rad_to_cl>-0.5</control_joint_rad_to_cl>
<cl_delta>-0.5</cl_delta>
<cd_delta>0.05</cd_delta>
<cm_delta>0.005</cm_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="right_wing" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<plugin name="right_wing_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>-0.009519322</alpha0>
<cd_alpha0>0.003</cd_alpha0>
<cm_alpha0>0.002072715</cm_alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
<cda>0.35</cda>
<cma>0.02</cma>
<alpha_stall>0.3391428111</alpha_stall>
<cla_stall>-3.85</cla_stall>
<cda_stall>-0.9233984055</cda_stall>
Expand All @@ -534,17 +540,21 @@
<upward>0 0 1</upward>
<link_name>base_link</link_name>
<control_joint_name>
right_elevon_joint
right_aileron_joint
</control_joint_name>
<control_joint_rad_to_cl>-0.5</control_joint_rad_to_cl>
<cl_delta>-0.5</cl_delta>
<cd_delta>0.05</cd_delta>
<cm_delta>0.005</cm_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="left_flap" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<plugin name="left_flap_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>-0.009519322</alpha0>
<cd_alpha0>0.003</cd_alpha0>
<cm_alpha0>0.002072715</cm_alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
<cda>0.35</cda>
<cma>0.02</cma>
<alpha_stall>0.3391428111</alpha_stall>
<cla_stall>-3.85</cla_stall>
<cda_stall>-0.9233984055</cda_stall>
Expand All @@ -558,15 +568,19 @@
<control_joint_name>
left_flap_joint
</control_joint_name>
<control_joint_rad_to_cl>-0.5</control_joint_rad_to_cl>
<cl_delta>-0.5</cl_delta>
<cd_delta>0.05</cd_delta>
<cm_delta>0.005</cm_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="right_flap" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<plugin name="right_flap_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>-0.009519322</alpha0>
<cd_alpha0>0.003</cd_alpha0>
<cm_alpha0>0.002072715</cm_alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
<cda>0.35</cda>
<cma>0.02</cma>
<alpha_stall>0.3391428111</alpha_stall>
<cla_stall>-3.85</cla_stall>
<cda_stall>-0.9233984055</cda_stall>
Expand All @@ -580,12 +594,14 @@
<control_joint_name>
right_flap_joint
</control_joint_name>
<control_joint_rad_to_cl>-0.5</control_joint_rad_to_cl>
<cl_delta>-0.5</cl_delta>
<cd_delta>0.05</cd_delta>
<cm_delta>0.005</cm_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="elevator" filename="libLiftDragPlugin.so">
<a0>-0.2</a0>
<plugin name="elevator_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>-0.2</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
Expand All @@ -602,12 +618,12 @@
<control_joint_name>
elevator_joint
</control_joint_name>
<control_joint_rad_to_cl>-4.0</control_joint_rad_to_cl>
<cl_delta>-4.0</cl_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="rudder" filename="libLiftDragPlugin.so">
<a0>0.0</a0>
<plugin name="rudder_liftdrag" filename="libLiftDragPlugin.so">
<alpha0>0.0</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
Expand All @@ -624,7 +640,7 @@
<control_joint_name>
rudder_joint
</control_joint_name>
<control_joint_rad_to_cl>4.0</control_joint_rad_to_cl>
<cl_delta>4.0</cl_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
Expand Down Expand Up @@ -719,23 +735,23 @@
<joint_control_type>velocity</joint_control_type>
<joint_name>rotor_puller_joint</joint_name>
</channel>
<channel name="left_elevon">
<channel name="left_aileron">
<input_index>5</input_index>
<input_offset>0</input_offset>
<input_scaling>1</input_scaling>
<zero_position_disarmed>0</zero_position_disarmed>
<zero_position_armed>0</zero_position_armed>
<joint_control_type>position_kinematic</joint_control_type>
<joint_name>left_elevon_joint</joint_name>
<joint_name>left_aileron_joint</joint_name>
</channel>
<channel name="right_elevon">
<channel name="right_aileron">
<input_index>6</input_index>
<input_offset>0</input_offset>
<input_scaling>1</input_scaling>
<zero_position_disarmed>0</zero_position_disarmed>
<zero_position_armed>0</zero_position_armed>
<joint_control_type>position_kinematic</joint_control_type>
<joint_name>right_elevon_joint</joint_name>
<joint_name>right_aileron_joint</joint_name>
</channel>
<channel name="elevator">
<input_index>7</input_index>
Expand Down
14 changes: 7 additions & 7 deletions models/standard_vtol/standard_vtol.sdf.jinja
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Expand Up @@ -723,7 +723,7 @@
<parent>base_link</parent>
</joint>
<plugin name="left_wing_lift" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<alpha0>0.05984281113</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
Expand All @@ -740,12 +740,12 @@
<control_joint_name>
left_elevon_joint
</control_joint_name>
<control_joint_rad_to_cl>-1.0</control_joint_rad_to_cl>
<cl_delta>-1.0</cl_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="right_wing_lift" filename="libLiftDragPlugin.so">
<a0>0.05984281113</a0>
<alpha0>0.05984281113</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
Expand All @@ -762,12 +762,12 @@
<control_joint_name>
right_elevon_joint
</control_joint_name>
<control_joint_rad_to_cl>-1.0</control_joint_rad_to_cl>
<cl_delta>-1.0</cl_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="elevator_lift" filename="libLiftDragPlugin.so">
<a0>-0.2</a0>
<alpha0>-0.2</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0</cma>
Expand All @@ -784,12 +784,12 @@
<control_joint_name>
elevator_joint
</control_joint_name>
<control_joint_rad_to_cl>-12.0</control_joint_rad_to_cl>
<cl_delta>-12.0</cl_delta>
<robotNamespace></robotNamespace>
<windSubTopic>world_wind</windSubTopic>
</plugin>
<plugin name="rudder_lift" filename="libLiftDragPlugin.so">
<a0>0.0</a0>
<alpha0>0.0</alpha0>
<cla>4.752798721</cla>
<cda>0.6417112299</cda>
<cma>0.0.</cma>
Expand Down
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