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Add two new attributes to weld constraints:

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- `anchor` determines the point of wrench application, in the frame of body2.
- `tfratio` scales applied torques relative to applied forces.
- Add visualisation of both anchor points to both weld and connect constraints.
- Add a test model showing how the new weld parameters behave.

PiperOrigin-RevId: 470021901
Change-Id: I3faba0e5dcab2e29ee81096f5ff71ff66d99758c
This commit is contained in:
Alessio Quaglino
2022-08-25 10:21:26 -07:00
committed by Copybara-Service
parent e2c3f04097
commit d26501c0f3
20 changed files with 491 additions and 248 deletions
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doc/APIreference.rst
+1 -1
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@@ -3163,7 +3163,7 @@ Numeric constants
+------------------+--------+----------------------------------------------------------------------------------------+
| mjMAXVFSNAME | 100 | The maximal number of characters in the name of each file in the virtual file system. |
+------------------+--------+----------------------------------------------------------------------------------------+
| mjNEQDATA | 7 | The maximal number of real-valued parameters used to define each equality constraint. |
| mjNEQDATA | 11 | The maximal number of real-valued parameters used to define each equality constraint. |
| | | Determines the size of mjModel.eq_data. This and the next five constants correspond to |
| | | array sizes which we have not fully settled. There may be reasons to increase them in |
| | | the future, so as to accommodate extra parameters needed for more elaborate |
doc/XMLreference.rst
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@@ -812,7 +812,9 @@ in the second column of the table have the following meaning:
| | | +-------------------------+-------------------------+-------------------------+ |
| | | | :at:`body2` | :at:`relpose` | :at:`active` | |
| | | +-------------------------+-------------------------+-------------------------+ |
| | | | :at:`solref` | :at:`solimp` | | |
| | | | :at:`solref` | :at:`solimp` | :at:`anchor` | |
| | | +-------------------------+-------------------------+-------------------------+ |
| | | | :at:`torquescale` | | | |
| | | +-------------------------+-------------------------+-------------------------+ |
+--------------------------+----+------------------------------------------------------------------------------------+
| |_2|:el:`joint` | \* | .. table:: |
@@ -4023,6 +4025,16 @@ of the other body, without any joint elements in the child body.
body1. If the quaternion part (i.e., last 4 components of the vector) are all zeros, as in the default setting, this
attribute is ignored and the relative pose is the one corresponding to the model reference pose in qpos0. The unusual
default is because all equality constraint types share the same default for their numeric parameters.
:at:`anchor`: :at-val:`real(3), "0 0 0"`
Coordinates of the weld point relative to body2. If :at:`relpose` is not specified, the meaning of
this parameter is the same as for connect constraints, except that is relative to body2. If :at:`relpose` is
specified, body1 will use the pose to compute its anchor point.
:at:`torquescale`: :at-val:`real, "1"`
Relative torque-to-force ratio. This ratio is used by the weld to scale how much it "cares" about rotational
displacements vs. translational displacements. Setting this value to 0 makes the :el:`weld` behave like a
:el:`connect` constraint. Note that this value has units of length and can therefore be interpreted as follows.
Imagining that the weld is implemented by a patch of glue sticking the two bodies together, :at:`torquescale` can be
interpreted as the diameter of this glue patch.
.. _equality-joint:
doc/changelog.rst
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@@ -15,8 +15,14 @@ General
- Added :ref:`adhesion actuators<adhesion>` mimicking vacuum grippers and adhesive biomechanical appendages.
- Added related `example model <https://github.com/deepmind/mujoco/tree/main/model/adhesion>`_ and video:
- Added :ref:`mj_jacSubtreeCom` for computing the translational Jacobian of the center-of-mass of a subtree.
- Added moment of inertia computation for concave meshes. This is currently activated by setting the compiler flag
:at:`exactmeshinertia` to ``true`` (defaults to ``false``). This default may change in the future.
- Added :at:`torquescale` and :at:`anchor` attributes to :el:`weld` constraints. :at:`torquescale` sets the
torque-to-force ratio exerted by the constraint, :at:`anchor` sets the point at which the weld wrench is
applied. See :ref:`weld <equality-weld>` for more details.
- Increased ``mjNEQDATA``, the row length of equality constraint parameters in ``mjModel.eq_data``, from 7 to 11.
- Added visualisation of anchor points for both :el:`connect` and :el:`weld` constraints (activated by the 'N' key in
``simulate``).
- Added `example model <https://github.com/deepmind/mujoco/tree/main/test/engine/testdata/weld.xml>`_ showing different
uses of new weld attributes.
- Joint and tendon ``limited`` attribute and actuator ``ctrllimited``, ``forcelimited`` and ``actlimited`` attributes
now default to ``auto`` rather than ``false``. Limits are automatically set to ``true`` if the corresponding range *is
defined* and ``false`` otherwise.
@@ -25,6 +31,8 @@ General
This is a minor breaking change. In models where a range was defined but :at:`limited` was unspecified, the target
element will now be limited. Explicitly set limited to ``false`` to revert to the previous behavior.
- Added moment of inertia computation for all well-formed meshes. This option is activated by setting the compiler
flag :at:`exactmeshinertia` to ``true`` (defaults to ``false``). This default may change in the future.
- Added parameter :at:`shellinertia` to :at:`geom`, for locating the inferred inertia on the boundary (shell).
Currently only meshes are supported.
- For meshes from which volumetric inertia is inferred, raise error if the orientation of mesh faces is not consistent.