On Thu, Aug 15, 2013 at 12:55:38PM +0100, andy pugh wrote:
> I seem to recall discussion of using the kinematics module to perform
> a discrete differentiation to determine the trajectory speed. (which
> would allow velocity limits to be respected in non-trivial multi-axis
> kins). Is this implemented anywhere?
I think this is the Inverse Jacobian, and is implemented in genhexkins but
unused by linuxcnc.
http://en.wikipedia.org/wiki/Jacobian_matrix_and_determinant
The Jacobian at a point is not itself enough to figure out how to apply
joint velocity constraints, because those constraints vary all along the
course of the move. A single move, even a linear one, can take the
machine from a place where joint J0 would require a velocity limit, into
a region where the F-number gives the velocity limit, and then into a
region where joint J1 gives the tighest velocity constraint (crossing
the center of the work volume of a delta, for instance). However,
computing the jacobian at many points along a planned move may be one
ingredient of applying joint velocity constraints to trajectory
planning.
Jeff
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