Medical/biomechanical requirements

Diagram

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Diagrammatic representation of the collision process between upper arm and impacting robot part
Source: IFA

In response to an initiative by the then expert committee for machine construction, production systems and steel construction work, the IFA conducted a project in which it developed medical/biomechanical and work organization requirements for workplaces involving collaborative robots. They supplement and detail the requirements of the standards, and have been compiled in BG/BGIA Recommendations (now: Recommendations for Hazard Identification of the Accident Insurers, EGUs). Technical Specification (TS) 15066 supplementing ISO 10218-2 and a national DGUV informative publication (DGUV Information), which are based upon the recommendations and extend them, are currently at the draft stage.

Background

Risks of collision between robots and human beings cannot be ruled out in processes intentionally involving human-robot collaboration. The task was therefore to limit the biomechanical strain effects resulting from any collision to the extent that the persons affected are subjected only to minor, tolerable severity of strain. Depending upon the collision risk identified by the risk assessment of a specific work application involving a collaborative robot, either the pain threshold (the transition from the sense of pressure to the sense of pain) or the onset of injury (swelling, minor haematoma) serves to define the severity of strain. The defined permissible severity of strain upon the body can be expressed by the limit values of related strain criteria.

Preliminary guideline limit values for the strain criteria of "impact force", "clamp/pinch force" and "pressure/surface pressure" were defined for all regions of a simple body model. For this purpose, the IFA surveyed the literature and databases for data on injuries caused by external mechanical stresses. In DGUV Project FP 317 , concerning creation of a human pain threshold map, force and pressure limits were determined in cooperation with the medical faculty of the Johannes Gutenberg University in Mainz. The limits were determined for quasi-static application and with stress presented by a small plunger with angular geometry. The method yielded significant pressure limits for the current documents (refer to the pain threshold map).

The results of the studies are compiled in the BG/BGIA recommendations for the design of workplaces involving collaborative robots, and in the drafts of Technical Specification (TS) 15066 and of a DGUV informative publication. The documents provide comprehensive support for application of the safety requirements during risk assessments performed in companies.

Based upon the safety requirements and upon the medical and biomechanical requirements contained in the documents, workplaces involving collaborative robots can be set up and tested in such a way that the potential mechanical stress upon persons resulting from a collision does not exceed an acceptable/tolerable level. The required occupational safety of the persons involved is thus assured.

For risk assessments and measurements in industry, the IFA has developed KDMG-KOLROBOT, a force/pressure measurement system faithful to the human body in its mechanical characteristics (see Test apparatus).

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Contact

Dr Michael Huelke

Division 5: Accident prevention, Product safety

Tel: +49 2241 231-2644
Fax: +49 2241 231-2234