# Comparison of Single-Arm and Dual-Arm Collaborative Robots in Precision Assembly
## 3 Results and Discussion
### Speed and Acceleration  
The sequence of movements of both compared robots (single-arm and dual-arm) in relation to time is presented in Table 4.  
Figure 12: Percentage of individual assembly tasks for each robot arm for variant II. Figure 13: Percentage of tasks for variant II—dual-arm robot. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Task** & **RAM 1** & **RAM 2** & \begin{tabular}{c} **Pressing the** \\ **RAMs** \\ \end{tabular} & \
\begin{tabular}{c} **Processor** \\ **Movement** \\ \end{tabular} &
\begin{tabular}{c} **Free** \\ **Total** \\ \end{tabular} \\ \hline Left arm & 2.6 & - & - & 3.9 & 7.1 & 13.6 \\ Right arm & - & 2.4 & 2.1 & - & 9.1 & 13.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The time needed to perform individual assembly tasks by each arm of a dual-arm robot. The course of the actual TCP speeds of the gripper of a single-arm robot and two arms of a dual-arm robot is shown in Figure 14. The programmed speeds may differ from the real ones due to the kinematics of the robot or the length of the movement path and the inability to achieve the programmed speed on a given section of the path. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Single-Arm Robot**} & \multicolumn{4}{c}{**Dual-Arm Robot**} \\ \cline{2-5}  & \multicolumn{4}{c}{**Left Arm**} & \multicolumn{2}{c}{**Right Arm**} \\ \hline
**Time [s]** & **Sequence** & **Time [s]** & **Sequence** & **Time [s]** & **Sequence** \\ \hline
0 & start & 0 & start & 0 & start \\ \hline
0.72 & free movement & 0.768 & free movement & 2.784 & free movement \\ \hline
1.08 & working movement & 1.344 & working movement & 3.36 & working movement \\ \hline
2.112 & picking RAM1 & & & & \\ \hline
2.76 & free movement & 2.4 & picking RAM2 & 4.416 & picking RAM1 \\ \hline
3.144 & working movement & 3.48 & free movement & 5.544 & free movement \\ \hline
4.176 & inserting RAM1 & & & & \\ \hline
4.92 & free movement & 4.056 & working movement & 5.832 & working movement \\ \hline
5.328 & working movement & 5.112 & inserting RAM2 & 6.864 & inserting RAM1 \\ \hline
6.36 & picking RAM2 & 7.584 & free movement & 8.352 & free movement \\ \hline
7.032 & free movement & 7.8 & working movement & 8.64 & working \\ \hline
7.416 & working movement & 8.832 & picking processor & & movement \\ \hline
8.448 & inserting RAM2 & 11.04 & free movement & 8.664 &
\begin{tabular}{c} pressing RAM 1 \\ (corner 1) \\ \end{tabular} \\ \hline
9.912 & free movement & 11.208 & working movement & 8.904 & free movement \\ \hline
10.272 & working movement & & & & \\ \hline
10.32 & \begin{tabular}{c} pressing RAM 1 \\ (corner 1) \\ \end{tabular} & 12.24 & \
\begin{tabular}{c} inserting \\ processor \\ \end{tabular} & 9.168 &
\begin{tabular}{c} working \\ movement \\ \end{tabular} \\ \hline
11.064 & free movement & 13.632 & free movement & 9.84 & free movement \\ \hline
11.448 & working movement & & & & \\ \hline
11.496 &
\begin{tabular}{c} pressing RAM 1 \\ (corner 2) \\ \end{tabular} & & & & & \\ \hline
10.152 &
\begin{tabular}{c} pressing RAM 2 \\ (corner 1) \\ \end{tabular} & & & & & \\ \hline
11.784 & free movement & & & & \\ \hline
12.168 & working movement & & & & \\ \hline
12.216 &
\begin{tabular}{c} pressing RAM 2 \\ (corner 1) \\ \end{tabular} & & & & & \\ \hline
10.68 &
\begin{tabular}{c} pressing RAM 2 \\ (corner 2) \\ \end{tabular} & & & & & \\ \hline
12.936 & free movement & & & & \\ \hline
13.344 & working movement & & & & \\ \hline
13.368 &
\begin{tabular}{c} pressing RAM 2 \\ (corner 2) \\ \end{tabular} & & & & & \\ \hline
15.24 & free movement & & & & \\ \hline
15.552 & working movement & & & \\ \hline
16.608 & picking processor & & & \\ \hline
18.192 & free movement & & & \\ \hline
18.552 & working movement & & & \\ \hline
19.584 & inserting processor & & & \\ \hline
20.568 & free movement & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Robot movement sequences. ABB YuMi robots have no difficulty in achieving a maximum speed of 200 mm/s on programmed paths.