Dynamic speed and separation monitoring for collaborative robot applications – Concepts and performance

Speed and separation monitoring (SSM) allows safeguarding the operator in collaborative robot applications by maintaining a certain minimum separation distance during operation. A continuous adaptation of the robot velocity in response to relative operator and robot motion can be employed to improve the efficiency of SSM-type applications. The present paper presents two approaches for obtaining a robot velocity limit for this adaptation, considering the separation distance as well as the direction of robot motion. Using a collaborative machine tending task as an example, the impact of these approaches on application productivity was assessed in physical trials and compared to that of conventional safeguarding methods, i.e. zone-based supervision and safeguarding by physical barriers. The trials confirmed that the continuous speed adaptation has a notable productivity benefit over the state of industrial practice. Major factors that influence the particular benefit, such as the frequency and timing of operator presence near the robot, have been identified and investigated. Before these concepts can be applied in industry, machinery safety requirements must be satisfied; at present, this depends particularly on the availability of sufficiently reliable information on the human position, which is not provided by safety sensors today.