# High-Speed Autonomous Robotic Assembly Using In-Hand Manipulation and Re-Grasping
## 7 Experimental Results
### Public Demonstration  
The suggested system was validated by a competitive public demonstration held at COEX, Seoul, Korea in December 2019. The public demonstration was held as the one of the selection processes of competitive research funding provided by the Korean Ministry of Science, ICT and Future Planning. Out of four teams that submitted the proposals, two teams were selected for the first phase, and one team was selected after the public demonstration and funded for the second phase of the research. The demonstration was divided into three stages with different difficulties, and at each stage the referees decided the target shape and initial block formation. Once the timer started, each team began assembling the blocks autonomously, and the total score was determined by whether the system provided correct assembly plans on display, how many blocks were successfully picked up and placed correctly, if the target shape was successfully assembled and the total time spent for the assembly. In the case of failure, each team could request the referee reset the block formation for restart, with a time penalty. Each stage \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Target Shape** & & & & \\ \hline Total number of assembly solutions & 240 & 39 & 13 & 79 \\ Time to find all the solutions (ms) & 3.5 & 1.0 & 0.47 & 1.58 \\ Time for checking all the solutions (ms) & 908.9 & 557.6 & 56.69 & 78.57 \\ Number of non-re-grasp solutions & 3 & 3 & 1 & 0 \\ Cost of the first non-re-grasp solutions & 620 & 620 & 590 & - \\ Time to find the first non-re-grasp solution (ms) & 40.2 & 18.6 & 56.65 & - \\ Best cost of non-re-grasp solutions & 620 & 620 & 590 & - \\ Average cost of non-grasp solutions & 768 & 780 & 590 & - \\ Time spent for re-grasp searching (ms) & - & - & - & 4.04 \\ \hline
**Total planning time (ms)** & **43.7** & **19.6** & **57.12** & **82.54** \\ \hline Average time spent for grasping blocks (s) & 1.92 & 1.87 & 1.84 & 1.97 \\ Average time spent for moving blocks (s) & 3.59 & 3.47 & 2.94 & 3.26 \\ Average time spent for returning (s) & 2.98 & 2.39 & 2.80 & 2.54 \\ Extra time spent for re-grasping (s) & - & - & - & 14 \\ \hline
**Total assembly time (s)** & **64** & **62** & **59** & **66** \\ \hline
**Total path length (m)** & **17.17** & **16.36** & **16.94** & **18.43** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of lab experiment results. Figure 15: Automatic assembly experiments in the lab setup: (**a**) \(3\times 3\times 3\) cube; (**b**) pyramid shape; (**c**) bridge shape; and (**d**) bathtub shape. used two different sets of target shapes and initial block formations, and the best score of the two runs was recorded as the stage score. To make the system as reliable as possible, we used lower maximum acceleration and velocity parameters for the manipulator motion control, and added more delay for block pickup and perception transitions by 0.5 s. In addition, we added the pre-positioning moves, which moved blocks with ambiguous orientation and tall blocks that could collide with gripper during pickup motion to the re-grasp position before motion planning. Finally, to handle the worst cases where the initial block formation was extremely close to the assembled target shape, we added an additional \"plowing\" motion that moved away the assembled blocks away from the blocks to be picked up. Even with those conservative settings, we achieved the official assembly time of 1 min 38 s at the third stage, which is more than three times faster than the other team's third stage assembly time exceeding 5 min. Figure 16 shows a number of block assembly sequences at the public demonstration setup for hard assembly cases with upright blocks and Table 2 shows the detailed analysis of them. One of the four shapes, the tower shape, had a very large number of assembly solutions, which made the full grasp search take a fairly long 6497.59 ms to complete. Using the first feasible solution decreased the search time by more than a factor of 100 and made the total motion planning time less than 100 ms.