How much carry time does a time-optimal move save over min-jerk, and what does it cost the jaws?
research/robofab-armbang
How much carry time does a time-optimal move save over min-jerk, and what does it cost the jaws? On the robofab-armaccel arm the six-part total falls by 21 to 29% while the jaw-force bound rises 1.2 to 2.4 times (stylised, assumed parameters).
What it found
A follow-up to robofab-armaccel: the same planar two-link arm carries the six free parts of the toy gripper along the same joint-space line, once with min-jerk and once with the time-optimal speed profile under an assumed joint torque limit. Over nine arm and torque cases the six-part total time falls by 21–29%, but the per-jaw force bound rises 1.2–2.4×. Stylised: every parameter except the geometry is assumed, the grip bound is not re-simulated above 40 m/s2, and the path is fixed.
A figure from its own output
Paper, code and results
More in Robot manufacturing loops
- How fast can an arm carry a printed part when the jaw force is capped as well as the joint torque?How fast can an arm carry a printed part when the jaw force is capped as well as the joint torque? On the
robofab-armbangarm the time-optimal move still beats min-jerk by 17 to 43% under caps of 1.25 to 10 times the static hold force, and a tight cap makes the torque limit irrelevant (stylised, assumed parameters). - Does a joint-speed limit erase the time-optimal carry's advantage over min-jerk?Does a joint-speed limit erase the time-optimal carry's advantage over min-jerk? On the
robofab-jawcaparm it grows it: 28 to 46% shorter under speed limits of 6 to 1 rad/s, tending to the 47% set by the min-jerk profile shape (stylised, assumed parameters). - Is the time-optimal carry's speed-limited advantage just the min-jerk profile's shape?Is the time-optimal carry's speed-limited advantage just the min-jerk shape? Against a tuned trapezoidal-velocity move it is only 0.4 to 2.9% at speed limits of 2 and 1 rad/s (46% over min-jerk), and 8.7 to 22.5% with no speed limit (stylised, assumed parameters).
- How much of the time-optimal carry's edge survives a jerk-limited (S-curve) profile?Does rounding the trapezoid's corners (a jerk-limited S-curve) change the time-optimal carry's edge? An S-curve is never faster than the trapezoid and costs 0.0 to 2.0% (half-jerk) or 0.0 to 7.0% (full-jerk) at speed limits of 2 and 1 rad/s, but 1.4 to 33.7% with no speed limit (stylised, assumed parameters).
- At tight joint-speed limits, is the time-optimal carry's edge over a trapezoid real or an artefact of the ramp grid?Checks
robofab-scurveon a finer ramp grid: sampling a 0.2% ramp is needed or the trapezoid wrongly beats the time-optimal solver; with it the time-optimal edge at 2 and 1 rad/s is −0.3 to +0.9%, below the solver's own ~0.5% node-count error (stylised, negative on the old figure). - Once the solver is converged, is the time-optimal carry's edge over a tuned trapezoid still positive in all twelve speed-limited rows?Re-solves the time-optimal carry at 400, 1600 and 6400 nodes in all 12 speed-limited rows of
robofab-scurvefine: once converged the edge over a tuned trapezoid is positive everywhere, +0.1 to +0.9% (stylised).
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.