# RoboTwin Metaverse Platform for Robotic Random Bin Picking
## 4 Results
### RoboTwin System  
#### 4.1.1 Physics Engines  
In the experiments, we used a robot equipped with a vacuum gripper to pick up and place standard weights of varying masses to assess the effectiveness of Equation (4). The experiments were conducted using the variables outlined in Section 3.1 and the values listed in Table 1 following the procedure described herein. We first picked up a weight of mass \(m\), activated the vacuum gripper with the maximum allowable air pressure \(p\) (i.e., 160 kpa as listed in Table 1), and then attached the weight to the gripper. We then gradually decreased the pressure until the weight dropped due to insufficient pressure, and recorded the corresponding \(p\) value. This recorded value indicates the minimum pressure required to hold an object of that specific mass. We repeated this process with weights of increasing mass \(m\) and compared the results from the real gripper to those from the simulator using the physics engines. The results from the aforementioned experiment are provided in Figure 3, where the solid blue line are values obtained from the gripper with measured pressure, while the \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline \(\alpha\) & 0 \\  & (Push the object toward the Suction Pad) \\ \hline \(m\) & 0.5–4 kg \\ \hline \(p\) & 10–160 kpa \\ \hline \(d\) & 0.04 m \\ \hline \(\mu\) & 1 \\  & (Suction pad must be parallel to the ground) \\ \hline \(t\) & [1, 4] (Safety factor introduced by authors in [14] \\  & to account for the orientation of gripper) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experiment parameters. Figure 2: The FOVision system consists of an edge computing unit, a 3D camera, and a lighting unit developed by ITRI. green and orange solid lines are the predicted values from the simulator using \(t\) values of 1 and 4, respectively. Note that \(t=1\) indicates no safety factor employed, whereas \(t=4\) indicates the safety factor is four times that of no safety factor applied. According to the experiment conducted on the real gripper and provided in Figure 3, when the mass is 1 kg, the gripper is not able to hold the standard weight if the air pressure provided falls below 25 kpa. However, from the simulations using a \(t=1\), this standard weight falls with 7.8 kpa or lower, and when \(t=4,31\) kpa or lower as calculated from Equation (4). This indicates that the simulator's predictions are not accurate enough, and more realistic factors need to be considered. Such factors include the friction and deformation of the gripper and the workpiece. Additionally, the safety factor \(t\) may need to be adjusted to a higher value to account for these factors. Overall, these results indicate the importance of verifying the simulator's predictions with real-world experiments to ensure the accuracy and reliability of the picking system. As discussed in Section 3, there exists a gap between simulation and real-world results. To fulfill this gap, we optimized the results by adding parameters for tuning through the LMMSE algorithm. Optimizing the scalars in Equation (4) gives us \(a=1.619\) and \(b=10.400\) for \(t=1\) and \(a=0.405\) and \(b=10.400\) for \(t=4\), respectively, which reduces the mentioned error and provides comparable results. As shown in Figure 4, the dashed green and orange lines are the corrected prediction using the LMMSE. Note that this correction leads to the overlapping of both green and orange dashed lines, even with different \(a\) and \(b\) values. The loss provided in the description of Figure 4 was calculated using the MSE between the measured and the respective simulated pressure values. The predicted values with \(t=1\) yield a lower error rate than the predicted values with \(t=4\) in terms of their deviation from the real measured pressure, but both can achieve an even lower error rate through LMMSE. A detail worth noting is that the real measured pressure recorded was read directly from an analog pressure valve, so the recorded \(p\) value may not be precise.