Collision Tests in Human-Robot Cooperation
Study of Constrained and Unconstrained Collisions during Human-Robot Collaboration with Human Subjects
In addition to the economic advantages it generates, human-robot collaboration in shared work areas also benefits humans ergonomically. Since humans may not be subject to any risk of injury from a collaborating robot, though, a risk assessment that primarily analyzes the risks for humans from a collision with a robot is essential.
A distinction is made between a constrained collision in which a human is pinned by the impact and an unconstrained collision in which a human is standing freely in space and is not pinned. Knowledge of the maximum forces in the event of an unconstrained collision is essential if the engineering of a collaborative work area is to eliminate constrained collisions. At present, it is only possible to measure constrained collisions reliably, however.
The Fraunhofer IFF completed a study on behalf of the Institute for Occupational Safety and Health IFA with the aim of developing a conversion function that converts the measured maximum forces of a constrained collision into the maximum forces of an unconstrained collision. The conversion function was calculated on the basis of an impact model and subsequently parameterized by collision tests with subjects. To this end, the Fraunhofer IFF developed a test setup with a pendulum that allows collision tests with human subjects, which were approved by an ethics commission.
The calculated impact model revealed that parameterization of the conversion function necessitates working with different high impact energies. Therefore, the pendulum swing has to be used to vary both the pendulum mass and the collision speed for the collision tests.
Each of the areas of the body selected was tested for both constrained and unconstrained collisions. A total of 19,000 individual measurements were taken. The evaluation of these measurements revealed that the impact model used reproduces the correlation of the maximum forces excellently for both collisions.