Analysis of Interlaboratory Safety Related Tests in Power and Force Limited Collaborative Robots

Abstract

The use of collaborative robots in the industrial domain has significantly grown in the last years, allowing humans to operate in the same workspace occupied by robots without any physical barriers. Understandably, the safety of the human operator has been a major concern both for researchers and regulatory bodies. The power and force limited modality of robots is of particular interest in that sense, being used in order to bound the energy of eventual collisions when a close physical interaction with humans is necessary. Such an interaction modality allows the robotic system to operate without the use of barriers, but a measurement of the force and pressure occurring due to a contact must be provided as part of the risk assessment. However, the precise procedure to follow in order to reliably provide such measures is still unclear for users and system integrators willing to self-assess the safety of their own collaborative robotic system. In this work, the repeatability and reliability of such testing procedures and measures are analyzed with an interlaboratory comparison approach, with the aim to establish the degree of variability possibly encountered when performing the same test under slightly different conditions.

Consistency Analysis and Suggestions of Collision Measurement in Human–robot Collaboration Safety Evaluation, 1-13.

“…Reference [33] conducted experiments on a generic abstraction of a collaborative pick and place task in the laboratory, approved that the exerted force during contact with a human is highly depended on the end effector velocity and the robot configuration, which can partially be explained by the variation of the determinant of the Jacobian matrix for different robot configurations. Reference [34] pointed out that variability occurs in robot velocity, the distance between the robot base and impact location, and the total stiffness of the measurement system. Reference [35] studied the effect of robot pose on peak impact force, considering two different positions for the collision, at the centre of the reference cube according to [36] and -5 cm from its outer side, lower peak forces were obtained at the outer edge.…”

Physical Ergonomics Monitoring in Human–Robot Collaboration: A Standard-Based Approach for Hand-Guiding Applications

“…All those measures can be complemented by providing wearable sensors for the targeted monitoring of the operator [14]. In the power and force-limiting operating mode a contact is rare but acceptable, but it must be guaranteed that it will not hurt the operator in any way, so the issue of human-robot contact must be properly addressed; the well-established approach is test-based and relies on the reproduction of the contact situation, replacing the human body part with so-called "biofidelic" sensors and reproducing the characteristics of the human body [15]. In hand-guiding (HG) mode, the robot moves according to human inputs; thus, it is worth considering ergonomics as more crucial than safety-strictly intended here as the prevention or mitigation of accidents.…”

An Online Toolkit for Applications Featuring Collaborative Robots Across Different Domains

“…These validation protocols build on an emerging testing approach for the validation of human-robot contact in different scenarios. Due to the importance of these issues in the viewpoint of HRC implementations, the COVR research group devoted great effort to the analysis of those testing procedures [41], resulting in reliable and comprehensive validation protocols that deal with several human-robot contact scenarios.…”