One should prefer numbers, experiments, and real data over speculation!
Here's a picture that illustrates these ideas:
http://www.anderswallin.net/sandbox/trajectory.jpg
Note how the jerk-limited trajectory is slower than the
acceleration-limited one. The jounce-limited ("double jerk") is slower
still. Nevertheless these are often termed "time optimal" i.e. they
are as fast as possible given the constraints.
The spectra are fairly quiet from 200-600 Hz. My guess is the
mechanical resonances of a machine are all below this, so the
significant features of the spectra are a 2 to 3-fold lowering of the
peaks around 50 and 200 Hz (?)
This is from http://dx.doi.org/10.1007/s00170-011-3842-0
The math for exact-stop planning for jerk- or jounce-limited
trajectories is not that hard and appears in many papers.
The hard parts are:
- blending ("cutting corners" within a tolerance) and/or lookahead
(possibly many g-code lines per traj-period?)
- how to handle feed-override >100%.(I suspect a feed-override change
cannot be applied instantaneously)
- non-trivkins (I suspect a jerk/jounce-limited traj-planner needs
derivatives of the fwd/reverse kins?)
Anders
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