## 5 Conclusions  
This paper has shown the current state of the cooperative behaviours module developed at CERN for the CERNTAURO project, which was very convenient in the control of similar operations in underwater scenarios. This paper shows the synergies between both projects and the technical aspects that can be applied in radioactive and underwater scenarios. The cooperative behaviours module, integrated into the HRI, includes a mission plan software which enables the user to activate/deactivate the corresponding cooperative behaviours according to the state of the mission and unexpected situations that might arise. Experience in real interventions shows that, in order to guarantee the safety of human beings and machines, it is very convenient to have a human being in the loop who can supervise the execution of close-loop behaviours, having the ability to decide the state of the mission, the level of interaction (from manual to autonomous control), and the interaction mode (e.g., scripts, keyboards, master/slave, etc). The experiments shown in this paper cover very important aspects of the cooperative intervention, such as the tracking and object recognition module, the underwater results from the experiments' communication, validation of the system by recovering and transporting a pipe with two robots in the CERN LHC mockup, as well as the use and validation of the HRI cooperative module to recover a pipe in a simulated underwater training scenario. Current efforts are being made to apply the knowledge acquired from this experience to real underwater field experiments. Figure 26: Completion time for two operators during a simulated multi-robot grasping procedure using the grasping detection capabilities. This paper also presents a comparative analysis to solve recovery and transport of the pipe, first by using two expert operators and secondly by using one operator who uses the cooperative behaviours and the mission plan. The usability results show that the cooperative behaviours module enables a single operator to control the robot team in a safer way, being able to smoothly pick up and transport the pipe. Besides this, the experiments have been performed, first by using a teleoperated leader-follower technique and later by using a multi-robot grasping determination algorithm, which has shown the best results in terms of safety and efficiency. The system has been enhanced with a reliable vision-based tracking and recognition module that demonstrates very good reliability when facing metallic and underwater images, while an extension to the module in order to calculate the grasping points of the robot team has also been presented. Further work will focus on defining and evaluating more advanced techniques for multi-robot grasping executions, focusing on more realistic underwater scenarios. Conceptualization, M.D.C., R.M.P., A.M., and P.J.S. ; data curation, C.V.A., G.L., and D.C.B. ; formal analysis, M.D.C.; funding acquisition, A.M. and P.J.S. ; investigation, C.V.A. and G.L. ; methodology, M.D.C., R.M.P., and A.M.; project administration, M.D.C., A.M., and P.J.S. ; resources, M.D.C., A.M., and P.J.S. ; software, C.V.A., G.L., M.D.C., D.C.B., and R.M.P. ; supervision, M.D.C.; validation, C.V.A. and G.L. ; visualization, C.V.A. and R.M.P. ; writing--original draft, C.V.A., G.L., and R.M.P. ; writing--review and editing, C.V.A., G.L., and R.M.P. All authors have read and agreed to the published version of the manuscript. It has been partially funded by CERN, the Spanish Government, MECD Salvador Madariaga, GV, and UJI under the projects CERNTAURO, PROMETEO, NEPTUNO, BES-2015-073112, DPI2017-86372-C3 (TWINBOT), and CIRTESU (IDIFEDER/2018/013). This work has been performed jointly between the European Center for Nuclear Research (CERN PhD Program) and the Jaume I University of Castellon (UJI).