From 537d649e95d5de559786ae55a0f3bb83cffd1426 Mon Sep 17 00:00:00 2001 From: Yuval Tassa Date: Wed, 13 Dec 2023 13:21:43 -0800 Subject: [PATCH] Improvements to transmission documentation. PiperOrigin-RevId: 590694542 Change-Id: I9dc25655116c9300061095c2a2b701530bbbbeca --- doc/computation/index.rst | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/doc/computation/index.rst b/doc/computation/index.rst index 8afdb7cf..788cdd14 100644 --- a/doc/computation/index.rst +++ b/doc/computation/index.rst @@ -300,19 +300,22 @@ is attached; the possible attachment object types are :at:`joint`, :at:`tendon`, Slider-cranks can also be modeled explicitly by creating MuJoCo bodies and coupling them with equality constraints to the rest of the system, but that would be less efficient. -:at:`site` - :at:`site` transmission (without a :at:`refsite`, see below) and :at:`body` transmission targets have a fixed zero - length :math:`l_i(q) = 0`. They can therefore not be used to maintain a desired length, but can be used to apply - forces. Site transmissions correspond to applying a Cartsian force/torque at the site, and are useful for modeling - jets and propellors. :el:`body` transmissions correspond to applying forces at contact points belonging to a body, in +:at:`body` + :el:`body` transmission corresponds to applying forces at contact points belonging to a body, in order to model vacuum grippers and biomechanical adhesive appendages. For more information about adhesion, see the - :ref:`adhesion` actuator documentation. + :ref:`adhesion` actuator documentation. These transmission targets have a fixed zero length + :math:`l_i(q) = 0`. - If a :at:`site` transmission target is defined with the optional :at:`refsite` attribute, forces and torques are - applied in the frame of the reference site rather than the site's own frame. If a reference site is defined then - the length of the actuator is nonzero and corresponds to the pose difference of the two sites. This length can then - be controlled with a :el:`position` actuator, enabling Cartesian end-effector control. See the - :ref:`refsite` documentation for more details. +:at:`site` + Site transmissions correspond to applying a Cartsian force/torque in the frame of a site, and are useful for + modeling jets and propellors. When a :at:`refsite` is not defined (see below), these targets have a fixed zero + length :math:`l_i(q) = 0`. + + If a :at:`site` transmission is defined with the optional :at:`refsite` attribute, forces and torques are applied in + the frame of the reference site rather than the site's own frame. If a reference site is defined, the length of the + actuator is nonzero and corresponds to the pose difference of the two sites, projected onto a chosen direction in the + reference frame. This length can then be controlled with a :el:`position` actuator, allowing for Cartesian + end-effector control. See the :ref:`refsite` documentation for more details. .. _geActivation: