Mobile Robot Base Placement for Assembly Systems: Survey, Measures and Task Clustering

Increasing fluctuations in demand and individualised products require changeability in manufacturing and assembly systems. Line-less mobile assembly systems (LMAS) represent a paradigm aimed at producing large products in small lot sizes. One enabler for LMAS is the automated planning and evaluation of spatial configurations of assembly resources regarding the executability of the assembly tasks. Criteria for executability are the reachability and manipulability measures of the assembly resource. To overcome extensive simulations and case-studies, faster solutions for executability evaluations are necessary. This paper surveys methods of base placement of robots, for utilisation in online assembly configuration planning. Based on the survey, research gaps are identified. A task clustering algorithm for preselection of spatially distributed task sets into task sequences executable from discrete base placements is presented. Clustering overcomes the often applied assumption that the set of given tasks has to be reachable from one discrete base placement.