# Detecting and Solving Tube Entanglement in Bin Picking Operations
## 5 Conclusions  
This paper proposes an algorithm for robotic bin picking of tube-shaped objects that handles occlusion and entanglement, for which there is little research, as well as a set of key definitions to tackle this challenge. The solution's main steps are generating a model of the tubes via point cloud analysis to determine which objects are occluded, using a physics engine to simulate various trajectories for post-grasp movement and performing force/torque analysis to detect and solve cases of entanglement. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Set A** & **Set B** \\ \hline \multirow{2}{*}{Total processing time, all cases} & Average & 7.38 s & 8.72 s \\ \cline{2-4}  & Std. deviation & 13.28 s & 14.59 s \\ \hline \multirow{2}{*}{Total processing time, cases without simulation} & Average & 4.13 s & 2.68 s \\ \cline{2-4}  & Std. deviation & 1.07 s & 0.73 s \\ \hline \multirow{2}{*}{Total processing time, cases with simulation} & Average & 48.99 s & 37.47 s \\ \cline{2-4}  & Std. deviation & 23.52 s & 14.95 s \\ \hline \multirow{2}{*}{Modeling time} & Average & 3.15 s & 2.11 s \\ \cline{2-4}  & Std. deviation & 0.81 s & 0.58 s \\ \hline \multirow{2}{*}{Planning time, all cases} & Average & 4.06 s & 6.46 s \\ \cline{2-4}  & Std. deviation & 13.15 s & 14.51 s \\ \hline \multirow{2}{*}{Planning time, cases without simulation} & Average & 0.84 s & 0.44 s \\ \cline{2-4}  & Std. deviation & 0.41 s & 0.23 s \\ \hline \multirow{2}{*}{Planning time, cases with simulation} & Average & 45.27 s & 35.11 s \\ \cline{2-4}  & Std. deviation & 23.55 s & 14.84 s \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Statistics for the execution times of different sets of phases. On 20 experiments conducted using seven rubber radiator hoses, the robot was able to completely empty the bin with a success rate of 80%, while successfully picking up tubes on the first try 93% of the time. The system resorted to simulation on 17% of the attempts with a success rate of 68%, thus illustrating that using a simulator to perform motion planning is a promising technique. Entanglement resolution was also useful and was used on 8% of the picks with a success rate of 27%. Therefore, this study shows that the proposed solution presents relevant contributions towards the development of accurate and efficient industrial systems capable of manipulating entangled objects. The work presented in this paper opens several lines for further research. Firstly, other sorts of tubes, with different lengths, radii, and shapes could be used to perform tests with the solution presented in this article, to better ascertain its efficiency and limitations. Secondly, to increase the attractiveness of this solution for deployment in industrial settings, it is important to reduce the execution time, namely for the motion planning phase with the simulator. Experiments can be conducted to test how much the simulation can be sped up without causing instabilities (which may lead to cases of objects clipping). Thirdly, to increase the probability of successfully picking a single tube at a time, more types of trajectories could be generated. In particular, one could determine which tubes are occluding a given tube and compute an escape trajectory based on the formers' spatial configuration. It should be noted that the amount of trajectory candidates should be kept reasonably low to prevent the cycle time from increasing significantly due to the time needed for evaluation via simulation. Finally, this solution could be extended to deal with objects that have a certain degree of flexibility, by configuring the physics engine used by the simulator and calibrating its parameters. This improvement would have a great impact in the robotics industry since very little research has been conducted regarding bin picking of flexible objects. Conceptualization, G.L., C.M.C., A.S., and G.V. ; methodology, G.L., C.M.C., A.S., and G.V. ; software, G.L. ; validation, G.L. ; formal analysis, G.L. ; investigation, G.L. ; resources, G.L., C.M.C., A.S., and G.V.