diff --git a/doc/computation.rst b/doc/computation.rst index 22b87ee5..99f6d336 100644 --- a/doc/computation.rst +++ b/doc/computation.rst @@ -108,7 +108,7 @@ optimization algorithms. Inverse dynamics and optimization ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The objective of inverse dynamics it to recover the applied force and contact force given the position, velocity and +The objective of inverse dynamics is to recover the applied force and contact force given the position, velocity and acceleration of the multi-joint system. With hard contacts this computation is impossible. Consider pushing against a wall without moving. The contact force cannot be recovered from the kinematics, unless of course we consider the material deformations - in which case we need a soft contact model. Inverse dynamics are trivial to compute with @@ -291,7 +291,7 @@ is attached; the possible attachment object types are :at:`joint`, :at:`tendon`, :ref:`adhesion` actuator documentation. 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 the site's own frame. If a reference site is defined then + 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 :at:`refsite` documentation in :ref:`actuator` reference for more details.