Does the strawberry gripper co-design survive the measured range of stem pull-off force?

research/codesign-agri-pulloff

Does the strawberry-gripper co-design of codesign-agri survive measured stem pull-off forces (3.17 N bending and pulling, 13.94 N pulling alone) instead of an assumed 3.5 N? Partly: the optimiser ranking holds in 8 of 10 cells, but the best achievable objective falls from 0.665 to 0.075 as the median pull-off rises from 3.17 to 13.94 N, and at 13.94 N no 40-evaluation run finds a gripper that picks anything

5 tests

What it found

codesign-agri drew stem pull-off force from a lognormal with an assumed median of 3.5 N, and codesign-agri-sweep varied it only from 1.75 to 7 N. Here the median is set to measured values reported by Rajendran et al. (2022) from Dimeas et al.: 3.17 N (a 1.78 mm peduncle detached by bending and pulling) and 13.94 N (2.17 mm, pulling alone), plus 6 and 10 N between them, with the grip-force bound at the parent’s 8 N or the published 10 N gripping limit. Random search, CMA-ES and Bayesian optimisation get 40 evaluations and 20 seeds on the same 600 fruit; a 400-evaluation Bayesian run (5 seeds) gives a reference optimum. At 3.5 N and 8 N the parent’s numbers are reproduced (0.574, 0.611, 0.635). Bayesian optimisation leads CMA-ES, which leads random search, in 8 of 10 cells. The reference optimum falls from 0.665 (3.17 N) to 0.502 (6 N), 0.249 (10 N) and 0.075 (13.94 N) at the 8 N bound; raising the bound to 10 N adds 0.03 to 0.04 at low pull-off and 0.04 at 10 N, and the best design moves from two fingers (low pull-off) to four (6 to 13.94 N). Limits: the bruise threshold, friction, ripeness law and prices are still assumed, the pull-off spread and ripeness factor are the parent’s, and only two measurements are available for the pull-off median.

A figure from its own output

Figure produced by research/codesign-agri-pulloff: pulloff — codesign-agri-pulloff/experiments/pulloff.png, written by the project's own experiment code.

Paper, code and results

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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.