# On the Control and Validation of the PARA-SILSROB Surgical Parallel Robot
## 4 Discussion
Furthermore, the repeatability and accuracy of the robot were tested using two measurement systems presented in detail in [56], demonstrating that the robot had good repeatability and accuracy for its first iteration. Additionally, while the robot was in operation, the user had the capability to visually confirm and adjust the pose of the robot and its modules within the surgical field, which allowed for real-time correction until the desired poses were achieved. The two testing stages of the robot, which were conducted by medical experts, with one using a surgical kit and the other using a human phantom with 3D-printed esophagus, were used to evaluate the robotic system's usability across various criteria: comfort, responsiveness, accuracy, injury risks for the patient, maintenance, and procedure timing. In terms of comfort, there was no significant negative feedback provided, where the surgeons were asked at the end of the tests to provide a value between 0 and 10 (where 0 represented a high level of discomfort and 10 represented a high level of comfort) for the comfort experienced during the use of the system. The majority assigned values between 8 and 10. However, it was suggested that a dedicated master console be developed that aligns more closely with the manual manipulation of instruments to facilitate a more intuitive interaction between the master and slave systems. Regarding the system responsiveness, it had a value of 5 milliseconds, which is below the human reaction time (200-300 milliseconds) and accuracy; no substantial issues were reported due to the visual nature of the control system. Nonetheless, the motion scalability (accessible via the GUI) was frequently used. The safety features of the robotic system also underwent rigorous testing. These features include automatic retraction of the surgical instruments, emergency stop procedures, motion-scaling capabilities, and software limits (designed to prevent singular configurations). The automatic retraction procedure for the instruments was implemented during the initial phase of \begin{table}
\begin{tabular}{c c} \hline \hline
**Velocity Vector Component** & **RMSE Value** \\ \hline \(\dot{X}_{E}\) & 0.011591 \\ \(\dot{Y}_{E}\) & 0.017855 \\ \(\dot{Z}_{E}\) & 0.068058 \\ \(\dot{\psi}\) & 0.049791 \\ \(\dot{\theta}\) & 0.030903 \\ \(\dot{\varphi}\) & 0.022791 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Medical protocol used to perform the experimental tests with the PARA-SILSROB in the laboratory. robot testing using the laparoscopic kit. This process involves displaying an error message on the graphical interface, which requires the surgeon to confirm by pressing a button (customizable to the surgeon's preferences) on either of the two 3D Space Mouse devices on the master console. Once the button is pressed and the surgeon confirms the initiation of the process, the instrument tips are moved to the home position. Upon reaching this position, the surgeon confirms it by pressing the same button again. After this confirmation, the instruments are automatically retracted from the intraoperative field. For the emergency stop procedure, a dedicated button is provided on the engineer's graphical interface, which decelerates the robot's motors to zero, thus preventing a sudden halt. Additionally, motion scaling is limited by the software, with the system's maximum velocity and acceleration set at 25 mm/s and 50 mm/s\({}^{2}\), respectively. These speed and acceleration settings can be adjusted according to the surgeon's preferences during the pre-planning stage. A final safety measure restricts the motion range of each robot arm to prevent the system from reaching singularity positions or exceeding the end of the stroke. These constraints are encoded in the control system's source program, with additional safety measures that include displaying warnings on the surgeon's graphical interface when the robot approaches these critical positions. One challenge identified during testing was the initial learning curve associated with setting up the robot.