Assigning coordinate frames
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To be able to determine the spatial relationship or transformation, respectively, between the links of a manipulator, local coordinate frames have to assigned to them first. There are several rules that have to be observed when assigning coordinate frames following the Denavit-Hartenberg convention.
Notation
The notation of the links and joints is shown in the figure below. A manipulator consists of links that are connected with
joints. The links correspond to the rigid parts of an arm and the joints are the flexible connections between them. A joint is always assigned to the proximate link. So a link
is connected with its joint
to the end of link
. The proximate link
is then mounted to the end of
via its joint
. The first link
is mounted on the base via joint
and the end of the last link
corresponds to the end-effector.