Systematic Investigation of Influences on the Repeatability of Vertically Articulated Robot Arms

Vertically articulated robot arms (VAR) are highly flexible and cost-effective robots, representing the largest market share of industrial robots. Due to their kinematic structure, they are highly flexible but suffer from low repeatability. As a result, VARs are rarely used for precision assembly tasks, as expensive and complex compensation mechanisms are required. To enable these applications, a deeper understanding of the influences on their repeatability is required. Existing research largely analyzes the influencing factors in isolation, however, comprehensive systematic studies are lacking. Therefore, this work investigates a systematic analysis of the influences on the repeatability of VAR. To this end, a comprehensive experimental design was created and repeatability experiments were carried out using a KUKA-LWR4+. Influencing variables considered include, among others, the robot’s pose, thermal effects, backlash and external moments. Finally, practical recommendations for the use of VAR in repeatability critical processes are given.