[ODE] degrees of freedom in a slider - other joint types
ancient at ludens.elte.hu
Thu Aug 31 12:04:35 MST 2006
Bram Stolk wrote:
>ODE's slider has one degree of freedom.
>So when considering this image:
>ODE would be the one on the left.
>Is there a way to get an additional degree of freedom, as
>for the slider on the right?
>By the way: the ODE manual erroneously depicts the
>slider on the right, which can confuse the reader.
Not completely on the same note, but I've been wondering if there are
any plans or at least requests to add more joint types to the ones
already present in ODE. I don't really think that adding more basic
joint types and thus features would hamper the usability of ODE,
although it may present ambiguous situations in choosing the right joint
I'm trying to use ODE for vehicle dynamics and currently I see two
methods of doing suspensions: the overly-simplified approach of using
the specialized Hinge2 joint (which is actually one example of an
"extra" joint I'm talking about) which is incorrect compared to a real
suspension in both kinetics and kinematics or model the whole suspension
with all the arms as separate bodies and connect them by the basic
joints, which is theoretically correct but a computational overkill
while most probably introducing severe numerical errors in the process
of solving the system due to bad mass ratios of the bodies involved. As
opposed to this, I believe we could use a so-called "distance
constraint" (a 1d joint) to represent a "massless" link attaching two
bodies with "ball" joints at its ends (essentially 1 control arm in a
suspension). This would not be completely "correct" as there is no such
thing as a massless joint, but the result would probably be much faster
to compute while hardly any less accurate..
So, I repeat, is there any interest to add more to the joint types in
ODE or should such attempts remain separate?
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