Towards Safe Robot Use with Edged or Pointed Objects: A Surrogate Study Assembling a Human Hand Injury Protection Database

TL;DR

This work addresses the lack of injury data for edged and pointed contacts in physical human-robot interaction by constructing an initial hand-injury protection database using pig dew claws and chicken drumsticks as surrogates. It details a drop-testing methodology across wedge, edge, and sheet geometries, capturing injury types and corresponding forces, and demonstrates risk-reduction applications through two validation tasks (screwdriving and electronics handling) guided by an optimized low effective mass at contact. Key findings indicate that safe interaction with edged tools is feasible when the robot's effective mass and contact velocity are carefully controlled, with velocities around 0.5 m/s or lower generally preventing open injuries in the tested surrogates. The work lays the groundwork for a globally coordinated, comprehensive injury database to support safe pHRI across edged and pointed geometries, urging collaboration to expand data and validate against human tissues.

Abstract

The use of pointed or edged tools or objects is one of the most challenging aspects of today's application of physical human-robot interaction (pHRI). One reason for this is that the severity of harm caused by such edged or pointed impactors is less well studied than for blunt impactors. Consequently, the standards specify well-reasoned force and pressure thresholds for blunt impactors and advise avoiding any edges and corners in contacts. Nevertheless, pointed or edged impactor geometries cannot be completely ruled out in real pHRI applications. For example, to allow edged or pointed tools such as screwdrivers near human operators, the knowledge of injury severity needs to be extended so that robot integrators can perform well-reasoned, time-efficient risk assessments. In this paper, we provide the initial datasets on injury prevention for the human hand based on drop tests with surrogates for the human hand, namely pig claws and chicken drumsticks. We then demonstrate the ease and efficiency of robot use using the dataset for contact on two examples. Finally, our experiments provide a set of injuries that may also be expected for human subjects under certain robot mass-velocity constellations in collisions. To extend this work, testing on human samples and a collaborative effort from research institutes worldwide is needed to create a comprehensive human injury avoidance database for any pHRI scenario and thus for safe pHRI applications including edged and pointed geometries.

Figures (9)

• Figure 1: Using the generalized hand injury protection database for a constrained contact with a sharp edge can allow a reasonable risk assessment for contacts with a Phillips head, provide permissible mass-velocity combinations for safe impact scenarios, and allow deployment of safe velocity-scaling based on the computable effective robot mass.
• Figure 2: MRI scan and cross-section of the different experiment specimen as compared to the human hand Micheau_2015, key tissue types indicated for different specimen.
• Figure 3: Observable features representing injury types occurring upon impacting the pig dew claw and chicken drumstick.
• Figure 4: Impact drop testing and subject placement: Drop test device (i), mass unit with impactor and specimen (ii) and the applied impactors and prepared specimen, pig (P) and chicken (C) with three distinct impact locations (1-3 from distal to proximal).
• Figure 5: Experimental Flowchart.