joint - a connection between links.
Links in a mechanism are connected by joints. Joints are usually
movable, so that links may move relative to one others; however,
to allow mechanism to split and joint without breaking individual
links, a fixed joint can also be used to attach two links.
Joints are a subclass of connection, and are significantly more
complex: they can create dynamic equations arising from their motion;
can compute the relative pose between links based on the joint
position variables; contain compute a jacobian, transforming
joint to cartesian velocity; and have properties such as dry friction,
viscous friction, and inertia for each degree of freedom, used for
computing the equations of motion for a mechanism.
Joints may have any number of degrees of freedom (DOFs), but the number
of DOFs cannot change over time. (Well, it can, but I won't guaruntee
things will work right.) There are several built-in joint types:
fixed, prismatic, revolute, planar, and other. (Naturally, 'other'
joints don't do a whole lot right now.) Prismatic joints cause
a translation along the joint's z axis, while revolute joints
cause a rotation about z. planar joints rotate about z and
translate along x and y, while fixed joints do nothing at all.
joints may have limits along each degree of freedom, as indicated
by the limits[], min, and max members.
Many members of the joint class are exposed for use by user programs;
however, most of these should not actually be changed by users.
As with connections, the new operator should always be used to
create joints and the joints will be deleted by one of the parts
they're connected to, so the user doesn't need to retain a pointer
to the joint for memory management purposes.
![[more]](icon1.gif)
link* l0
synObject* owner