How fast can an arm carry a printed part when the jaw force is capped as well as the joint torque?
research/robofab-jawcap
How fast can an arm carry a printed part when the jaw force is capped as well as the joint torque? On the robofab-armbang arm 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).
What it found
A follow-up to robofab-armbang: the time-optimal speed profile along the joint-space line is solved with an added cap on the per-jaw force bound (a quadratic constraint on the path acceleration), at 1.25–10× the static hold force, and compared with the fastest min-jerk move meeting the same two limits. Over nine arm and torque cases the time-optimal six-part total is 17–43% shorter, most when the cap is tightest, and at the tightest cap the torque limit no longer changes the time. Stylised: every parameter except the geometry is assumed, the caps are multiples of a friction hold force, the grip bound is not re-simulated above 40 m/s2, profiles overshoot the limits by up to 3%, and the path is fixed.
A figure from its own output
Paper, code and results
More in Robot manufacturing loops
- 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). - Does tuning the trapezoid's ramp fraction beyond a grid shrink the time-optimal carry's edge, and is it still positive?Golden-section tuning of the trapezoid's ramp fraction shrinks the time-optimal carry's edge to +0.05 to +0.28% (still positive in all 12 rows; 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.