Approximation Methods and Reference Values for Maximum Allowed Collaborative Operating Speeds in Quasi-Static and Transient Contact Cases

This paper presents and utilizes suitable measurement setups for quasi-static and transient contact situations to conduct force and pressure measurements. Presented at the example of lathe machine tending, two typical risk situations are defined that represent a collision with the hand and the shoulder. Empirical measurement studies are executed with a selected cobot to model the maximum allowed collaborative speed behavior. Various influencing factors, such as sensor sensitivity, workpiece mass, robot pose, and additional padding, are assessed regarding their effect on the allowed velocity. As a result, an approximation equation is proposed to calculate allowed cobot velocities for the quasi-static case, while suitable reference values for the transient contact are given. Since a prototypical cell is required to conduct the force and pressure measurements, a priori estimation of realistic allowed operating speeds is impaired, resulting in imprecise cycle time assessment. With the presented approach, realistic values can be obtained based on a minimum of input data to refine the data accuracy at the project’s beginning. This leads to higher data reliability to make sound return on investment decisions upfront.