Research and Development in Robotic Systems

Biomechanical Thresholds from Other Applications (KAN Study)

Humans and robots will be sharing work areas more and more frequently in the near future and often working together hand-in-hand. Rather than by protective barriers, new safety sensors or safe manipulators will assure human safety. Whenever a person comes into contact with a robot, a distinction must be made between desired contact and a collision to assess the risk. Generally, the biomechanical load on humans must be limited to a tolerable and safe level in both types of contact. The relevant standard DIN EN ISO 10218 is currently supplemented by ISO TS 15066 with the goal of stipulating clear specifications for safe design and set-up of work areas with human-robot collaboration.

Accident insurers require a clear differentiation of the classification of tolerable loads from current categories of injury severity S1 (reversible injuries) and S2 (irreversible injuries or death).

There is no clear definition from the perspective of occupational safety. As part of the Commission for Occupational Health and Safety and Standardization’s study “Biomechanical thresholds”, the Fraunhofer IFF researched and compiled current situation and further need for biomechanical thresholds for mechanical risk assessments of work areas with human-robot collaboration.

© Fraunhofer IFF
Classification of the new injury severity categories.

The findings of the study will be a solid basis for future studies and are already serving occupational safety experts and manufacturers as an important base of data for concrete problems in risk assessment. During the study, an extensive literature search compiled 1000 titles with information relevant to biomechanical thresholds in the context of this study. Custom tools and methods developed during the study were used to search the literature. A large number of stress-strain relationships were excerpted from the 1000 searched titles and entered in a database that exports informative datasheets with all important data. The database is being added to continuously and will serve as a publicly accessible reference work on critical loads in the future.

In addition to the literature search, recommendations for the definition of a new injury severity category S0 and the structuring of biomechanical load parameters or stress-strain relationships for occupational safety were also formulated in the study. The following proposed definition was formulated in collaboration with occupational safety experts and physicians: “The S0 injury severity category would only include superficial injuries that heal completely without any medical treatment. Skin breakage would not be per-mitted and would therefore be excluded from this category.” The category would be introduced above the absolutely harmless level H, the transition of which would correspond to the onset of pain on the S0 level.