Safety system design in human-robot collaboration : Implementation for a demonstrator case in compliance with ISO/TS 15066

Sammanfattning: A close collaboration between humans and robots is one approach to achieve flexible production flows and a high degree of automation at the same time. In human-robot collaboration, both entities work alongside each other in a fenceless, shared environment. These workstations combine human flexibility, tactile sense and intelligence with robotic speed, endurance, and accuracy. This leads to improved ergonomic working conditions for the operator, better quality and higher efficiency. However, the widespread adoption of human-robot collaboration is limited by the current safety legislation. Robots are powerful machines and without spatial separation to the operator the risks drastically increase. The technical specification ISO/TS 15066 serves as a guideline for collaborative operations and supplements the international standard ISO 10218 for industrial robots. Because ISO/TS 15066 represents the first draft for a coming standard, companies have to gain knowledge in applying ISO/TS 15066. Currently, the guideline prohibits a collision with the head in transient contact. In this thesis work, a safety system is designed which is in compliance with ISO/TS 15066 and where certified safety technologies are used. Four theoretical safety system designs with a laser scanner as a presence sensing device and a collaborative robot, the KUKA lbr iiwa, are proposed. The system either stops the robot motion, reduces the robot’s speed and then triggers a stop or only activates a stop after a collision between the robot and the human occurred. In system 3 the size of the stop zone is decreased by combining the speed and separation monitoring principle with the power- and force-limiting safeguarding mode. The safety zones are static and are calculated according to the protective separation distance in ISO/TS 15066. A risk assessment is performed to reduce all risks to an acceptable level and lead to the final safety system design after three iterations. As a proof of concept the final safety system design is implemented for a demonstrator in a laboratory environment at Scania. With a feasibility study, the implementation differences between theory and praxis for the four proposed designs are identified and a feasible safety system behavior is developed. The robot reaction is realized through the safety configuration of the robot. There three ESM states are defined to use the internal safety functions of the robot and to integrate the laser scanner signal. The laser scanner is connected as a digital input to the discrete safety interface of the robot controller. To sum up, this thesis work describes the safety system design with all implementation details.