In this paper, we consider the problem of collectively exploring unknown and dynamic environments with a decentralized heterogeneous multi-robot system consisting of multiple units of two variants of a miniature robot. The first variant-a wheeled ground unit-is at the core of a swarm of floor-mapping robots exhibiting scalability, robustness and flexibility. These properties are systematically tested and quantitatively evaluated in unstructured and dynamic environments, in the absence of any supporting infrastructure. The results of repeated sets of experiments show a consistent performance for all three features, as well as the possibility to inject units into the system while it is operating. Several units of the second variant-a wheg-based wall-climbing unit-are used to support the swarm of mapping robots when simultaneously exploring multiple floors by expanding the distributed communication channel necessary for the coordinated behavior among platforms. Although the occupancy-grid maps obtained can be large, they are fully distributed. Not a single robotic unit possesses the overall map, which is not required by our cooperative pathplanning strategy.

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Automated welding has been very effective in enhancing the quality and quantity of weld jobs along with improving the safety of the workers. Nevertheless, most existing welding robots are massive and immobile. Typically, the workpieces are transferred to the robots for welding. This makes it difficult for many welding applications that have large scale structures e.g. shipbuilding, construction, on-site repair work, etc. In these cases, the welding robot should be able to be transported to the work-pieces. The purpose of this paper is to explore and study various recent developments in portable welding robot designs. Based on this, several strategies of designing portable welding robot are classified and discussed.