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DetachableJoint: allow physics constraint properties to be set #754

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@srmainwaring srmainwaring commented Jun 30, 2025 •
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🎉 New feature

Allow the joint constraint physics parameters constraint force mixing (cfm) and error reduction parameter (erp) to be set via Features. Here the parameters only apply to dynamically created joints in the dartsim engine, although the features are declared generally.

The parameters are not documented in the dartsim manual and must be inspected in the source code. They appear to be defined similarly to the parameters with the same name in ODE https://ode.org/wiki/index.php/Manual#Soft_constraint_and_Constraint_Force_Mixing_(CFM).

The parameters allow finer control over the simulation of the weld joints created using the detachable joint system. This is relevant when creating closed kinematic chains, where in some cases the constraint forces and error reduction iterations must be increased in order for the model to maintain integrity (i.e. prevent joints flying apart).

In dartsim these parameters are declared as class variables for DyanamicJointConstraints, so setting them on one detachable joint affects all others. Other physics engines may treat this differently.

Related:

Summary

  • Add a new feature SetDynamicJointConstraintPropertiesFeature
  • Like AttachFixedJoint this is a Link feature (the weld constraints belong to the link).

Test it

Checklist

  • Signed all commits for DCO
  • Added tests
  • Added example and/or tutorial
  • Updated documentation (as needed)
  • Updated migration guide (as needed)
  • Consider updating Python bindings (if the library has them)
  • codecheck passed (See contributing)
  • All tests passed (See test coverage)
  • While waiting for a review on your PR, please help review another open pull request to support the maintainers
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@github-actions github-actions bot added the 🏛️ ionic Gazebo Ionic label Jun 30, 2025
This was referenced Jun 30, 2025
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srmainwaring added a commit to srmainwaring/SITL_Models that referenced this pull request Jun 30, 2025
@srmainwaring
Helicopter: set physics params in detachable joints
5e23757 
- Use gazebosim/gz-physics#754
- Use gazebosim/gz-sim#2960

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
ahcorde
ahcorde requested changes Jul 1, 2025
View reviewed changes
@github-project-automation github-project-automation bot moved this from Inbox to In review in Core development Jul 1, 2025
srmainwaring added a commit to srmainwaring/SITL_Models that referenced this pull request Jul 3, 2025
@srmainwaring
Helicopter: add models for rotor head and helicopter
9f24003 
RotorHead
- Adjust pose of model in world
- Add further links and joints.
- Add lever coupling links and joints.
- Simplify collisions.
- Compose ball joint from 2 revolute joints.
- Simplify collisions for linkages.
- Ensure all ball joints have 3DoF
- Add servo linkage visuals.
- Limit movement of lever joints.
- Lever coupling top joints are revolute, not ball.
- Add guide rod and retainer to prevent lower swashplate rotation.
- Update friction and damping.
- Recompute ball joint inertials.
- Add servos and rods.
- Update joint damping.
- Update link and joint names.
- Align swashplate joints.
- Replace collision guide with joints.
- Add rotor blades.
- Add lift-drag plugins.
- Correct joint orientations.
- Reorient servo links.
- Reduce mass of rotor head.
- Adjust rotor lift-drag.
- Rename rotor head model
- Add ccw version of rotor head.
- Update orientation in ccw rotor head.
- Velocity controllers were not using force and PIDs
- Update PIDs for joint and position controllers.
- Fit lift-drag coefficients to NACA0012 profile.
- Add blade visuals for CW and CCW rotors.
- Move servo2 to be near centre of rotor head.
- Remove debug info.
- Remove debug colours of servo rods and joints.
- Add credit for visuals

Helicopter
- Add helicopter model in world.
- Add tail rotor.
- Add stabiliser bars and wheels.
- Add ArduPilot plugin.
- Swap servo_1 and servo_3 to be consistent with AP ordering.
- Adjust CoG.
- Adjust IMU position to main rotor.
- Add separate model and config files.
- Use standalone model for helicopter.
- Place on runway model.
- Rename helicopter world
- Update to SDF version 1.11
- Add intermeshing dual rotor example.
- Add meshes.
- Increase friction on stabilizers.
- Correct orientation of tail rotor blade visual and collision.
- Correct dual heli control elements.
- Increase mass of base link for dual heli.
- Add params for dual transverse helicopter.
- Add gimbal for testing attitude control.
- Allow blades to flap on rotor heads
- This is essential for correct operation.
- Blades hinge at blade grips with range +/- 8 deg.
- Adjust blade flapping damping and spring constant.
- Remove oscillation / resonance when rolling at higher collective.
- Reduce blade hinge spring stiffness.
- Set ball joint properties
- Use gazebosim/gz-physics#753
- Set physics params in detachable joints
- Use gazebosim/gz-physics#754
- Use gazebosim/gz-sim#2960
- Adjust flapping hinge position
- Move hinge towards rotor hub.
- This position gives a flapping lag of about 80 deg behind the blade pitch.
- Retune ATC_RAT PIDs for flapping blades.
- Add visuals for frame and rotors
- Add mesh visuals based on TRex-450.
- Remove stabilising links and wheels.
- Reposition tail rotor to match rescaled model.
- Update rotor velocity command topic.
- Add config for the ros_gz bridge
- Retune model for adjusted CoM and tail position
- Add credit for visuals

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
srmainwaring added a commit to srmainwaring/SITL_Models that referenced this pull request Jul 3, 2025
@srmainwaring
Helicopter: add models for rotor head and helicopter
58b9e68 
RotorHead
- Adjust pose of model in world
- Add further links and joints.
- Add lever coupling links and joints.
- Simplify collisions.
- Compose ball joint from 2 revolute joints.
- Simplify collisions for linkages.
- Ensure all ball joints have 3DoF
- Add servo linkage visuals.
- Limit movement of lever joints.
- Lever coupling top joints are revolute, not ball.
- Add guide rod and retainer to prevent lower swashplate rotation.
- Update friction and damping.
- Recompute ball joint inertials.
- Add servos and rods.
- Update joint damping.
- Update link and joint names.
- Align swashplate joints.
- Replace collision guide with joints.
- Add rotor blades.
- Add lift-drag plugins.
- Correct joint orientations.
- Reorient servo links.
- Reduce mass of rotor head.
- Adjust rotor lift-drag.
- Rename rotor head model
- Add ccw version of rotor head.
- Update orientation in ccw rotor head.
- Velocity controllers were not using force and PIDs
- Update PIDs for joint and position controllers.
- Fit lift-drag coefficients to NACA0012 profile.
- Add blade visuals for CW and CCW rotors.
- Move servo2 to be near centre of rotor head.
- Remove debug info.
- Remove debug colours of servo rods and joints.
- Add credit for visuals

Helicopter
- Add helicopter model in world.
- Add tail rotor.
- Add stabiliser bars and wheels.
- Add ArduPilot plugin.
- Swap servo_1 and servo_3 to be consistent with AP ordering.
- Adjust CoG.
- Adjust IMU position to main rotor.
- Add separate model and config files.
- Use standalone model for helicopter.
- Place on runway model.
- Rename helicopter world
- Update to SDF version 1.11
- Add intermeshing dual rotor example.
- Add meshes.
- Increase friction on stabilizers.
- Correct orientation of tail rotor blade visual and collision.
- Correct dual heli control elements.
- Increase mass of base link for dual heli.
- Add params for dual transverse helicopter.
- Add gimbal for testing attitude control.
- Allow blades to flap on rotor heads
- This is essential for correct operation.
- Blades hinge at blade grips with range +/- 8 deg.
- Adjust blade flapping damping and spring constant.
- Remove oscillation / resonance when rolling at higher collective.
- Reduce blade hinge spring stiffness.
- Set ball joint properties
- Use gazebosim/gz-physics#753
- Set physics params in detachable joints
- Use gazebosim/gz-physics#754
- Use gazebosim/gz-sim#2960
- Adjust flapping hinge position
- Move hinge towards rotor hub.
- This position gives a flapping lag of about 80 deg behind the blade pitch.
- Retune ATC_RAT PIDs for flapping blades.
- Add visuals for frame and rotors
- Add mesh visuals based on TRex-450.
- Remove stabilising links and wheels.
- Reposition tail rotor to match rescaled model.
- Update rotor velocity command topic.
- Add config for the ros_gz bridge
- Retune model for adjusted CoM and tail position
- Add credit for visuals

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
srmainwaring added a commit to srmainwaring/SITL_Models that referenced this pull request Jul 3, 2025
@srmainwaring
Helicopter: set physics params in detachable joints
cac1e9f 
- Use gazebosim/gz-physics#754
- Use gazebosim/gz-sim#2960

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
srmainwaring added a commit to srmainwaring/SITL_Models that referenced this pull request Jul 3, 2025
@srmainwaring
Helicopter: set physics params in detachable joints
6ef39ac 
- Use gazebosim/gz-physics#754
- Use gazebosim/gz-sim#2960

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
@srmainwaring srmainwaring mentioned this pull request Jul 3, 2025
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@iche033
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iche033 commented Jul 9, 2025

cc @scpeters in case you have opinions on these APIs.

There are some merge conflicts that need to be resolved otherwise looks good to me.

@srmainwaring
DetachableJoint: allow physics constraint properties to be set
8252e2f 
- Allow the constraint force mixing and error reduction parameters to be set on detachable joints.

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
@srmainwaring
DetachableJoint: correct formatting
03b126c 
Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>
@srmainwaring srmainwaring force-pushed the prs/8/pr-detachable-joint-properties branch from 169b173 to 03b126c Compare July 10, 2025 10:11
@srmainwaring
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There are some merge conflicts that need to be resolved otherwise looks good to me.

Resolved in 03b126c

@iche033
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iche033 commented Jul 10, 2025

@osrf-jenkins run tests please

scpeters
scpeters reviewed Jul 24, 2025
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include/gz/physics/FixedJoint.hh
{
/// \brief Set dynamic joint constraint properties.
public: template <typename PolicyT, typename FeaturesT>
class Link : public virtual Feature::Link<PolicyT, FeaturesT>
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from an API perspective, it seems odd that this is a Link API and not a Joint API. I can see from the implementation that it is more convenient this way, but I think it would be cleaner as a Joint method

if it's not currently possible, we should open an issue about that

scpeters
scpeters reviewed Jul 24, 2025
View reviewed changes
dartsim/src/JointFeatures.cc
void JointFeatures::SetConstraintForceMixing(const Identity &_childID,
double _value)
{
auto linkInfo = this->ReferenceInterface<LinkInfo>(_childID);
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if we pass a joint ID instead of the child link ID, I think we could extract the child LinkInfo using the same approach as in DetachJoint

@azeey azeey added this to the Jetty Release milestone Jul 28, 2025
@azeey azeey removed this from the Jetty Release milestone Aug 11, 2025
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@ahcorde ahcorde ahcorde requested changes

@iche033 iche033 iche033 approved these changes

@azeey azeey Awaiting requested review from azeey azeey is a code owner

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