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German Larrain committed 3fb8c91

robot.dh: fixed and improved docstrings.

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ars/model/robot/dh.py

-"""Denavit-Hartenberg related code
+r"""This module contains Denavit-Hartenberg related code.
+
+For a serial chain of links (defined by D-H parameters), matrix `T` defines the
+pose (position and orientation) of the end effector with respect to the base,
+based in the joints' `n` coordinates.
+
+.. math::
+
+	T = \operatorname{}^{0}A_1 \cdot \operatorname{}^{1}A_2 \cdots \operatorname{}^{n - 1}A_n
 
 """
 from ars.utils.mathematical import sin, cos
 	* :attr:`angle`: a.k.a. :math:`\theta`
 
 	On the other hand, :attr:`convention` stores which convention for the
-	parameters is used. There are two: standard (``'s'``) and Craig's modified
-	(``'m'``). By default the former is used.
+	parameters is used. There are two: standard (``'s'``, default) and Craig's
+	modified (``'m'``).
 
 	>>> (length, offset, twist, angle) = (0.0, 0.0, 0.0, 0.0)
 	>>> DHLink(*(length, offset, twist, angle))
 	###########################################################################
 
 	def calc_transform(self):
-		r"""Calculate the corresponding transformation matrix.
+		r"""Calculate link homogeneous transformation matrix.
 
-		This matrix, designated by :math:`\operatorname{}^{n - 1}T_n`, is useful
+		This matrix, designated as :math:`\operatorname{}^{n - 1}T_n`, is useful
 		to transform points from frame `n` to `n-1`. For the standard
 		convention:
 
 		source:
 		http://en.wikipedia.org/wiki/Denavit%E2%80%93Hartenberg_parameters#Denavit-Hartenberg_matrix
 
+		:return: 4x4 matrix
 		:rtype: tuple of tuples
 
 		"""