Does the MuJoCo feeding-arm result change when the lips have the ISO/TS 15066 face stiffness and the safe force comes from the standard?

What it found

osrobot-mjfeed assumed an 800 N/m lip and a 2 N comfort limit. This project re-runs the same MuJoCo feeding trial with the ISO/TS 15066 face effective spring constant (75 N/mm, 75,000 N/m) and the standard's face force limits (65 and 130 N; secondary sources disagree on which is quasi-static, so both are used). A 94× stiffer lip raises the blocked-arm impact peak about 2× (3.68 to 7.56 N at 0.10 m/s, 7.35 to 15.21 N at 0.20 m/s) and leaves the steady push unchanged. For the camera arm against a 30 mm sway (200 seeds), the share fed with peak contact within 2 N falls from 0.45 to 0.32 at 0.10 m/s, but within 65 N and 130 N it is 1.00 in every row; the worst peak is 53.3 N. So the assumed 2 N, not the physics, drove the earlier unsafe reading. Contact damping has no sourced value and is swept (blocked-arm peak 12.7 to 49.3 N from 100 to 1000 N·s/m at 0.20 m/s). Limits: the standard's tables were read only from secondary excerpts, lips are kinematic and cannot yield, pressure limits were not applied, tip mass, gains and sway remain assumed, no human model. Simulation only, not a safety case.

A figure from its own output

Paper, code and results

• README and method
• Experiments and results
• Tests

More in Open-source purpose-built robots

• How much force can a feeding-arm tip apply to a lip before the tissue bottoms out on bone?With tissue as a 5 to 20 mm layer bonded to bone at 4 to 45 kPa, the force that indents it 30 % is 0.05 to 9 N, 1.3 to 1000 times below the simulated 12.6 to 53 N trial forces, so the arm needs a newton-scale force cap, not 65 N (published bottom-effect corrections, no FE run)
• Is the feeding-arm tip's contact pressure computable at a measured face modulus?Published in-vivo face and lip moduli are 4 to 45 kPa, below the 0.05 to 5 MPa that osrobot-mjpress swept; at them a 4 mm tip at 53 N would sink 48 to 241 mm in a Hertz model, so the model is out of range and tip radius or depth, not 65 N, is the design question (closed-form, simulation forces)
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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.