## 3 Experiments
The task was executed successfully for all 15 subjects, demonstrating that the system was capable of delivering medicine while making sure that it had been taken. The third set of experiments was intended to investigate whether the proposed system could achieve a more even disinfection effect in the presence of various kinds of objects in the environment. To provide a comparison, experiments were carried out utilizing the conventional method. This involved solely driving the mobile platform of the robot manipulator along a predetermined path for disinfection without engaging the robotic arm. In contrast, via the algorithm for environmental disinfection in Section 2.3 with the desired irradiation intensity value set at 22 mJ/cm [41], the proposed system would further maneuver the robotic arm to follow the contour of the object. Figure 15 shows an experimental scene in which five UVC dose cards (UVC 254 Tri Card, Intellego Technologies,  
Figure 14: Experiment 2: (a) medicine delivery and (b) medicine taking. Figure 13: Results for Experiment 1: (a) distance between the subject and robotic arm and (b) approaching speed of the robotic arm. Sweden) used for irradiation intensity measurement were placed on several pieces of furniture in the smart ward. Table 1 lists the UVC dose readings on the five cards after both systems completed the disinfection process. Under the condition that almost the same amount of irradiation power was emitted from the UVC lamps for both systems, all the readings for the proposed system were larger than those of the conventional one, and they were all close to 22 mJ/cm, implying that the proposed system indeed achieved a more even disinfection effect. To evaluate how much possible infection risk might be reduced by replacing human personnel with the proposed system, we let the proposed system execute the tasks of temperature measurement and medicine delivery ten times, during which the robot navigated around the fever station, nursing station, and isolation ward. The whole process took about 85 s. The average risk infection index \(R_{c}\), defined in Section 2.4, was computed to be 0.38 by using (10) according to the traveled distances that were within a contact distance of 1.5 m and their corresponding contact time. Compared to the basic reproductive number \(R_{0}\) for COVID-19 at 5.7 [40], it showed a high potential for reducing infection risk by introducing robots for contagious diseases. The questionnaire was conducted after the experiments to obtain subjects' feedback. The questions, listed in Table 2, were designed based on the system usability scale (SUS) [22], which is frequently used for evaluating human-machine systems. There were ten questions to be answered with a 5-item Likert scale [42]. The answers were collected and analyzed to yield a final SUS score, with a higher one indicating that the subject favors the selection more. For temperature measurement, the proposed system was compared with that of the fixed device commonly used in our society. In a traditional setup, subjects were required to approach the device closely to measure their temperature themselves. For medicine delivery, it was compared with the case of the medicine being delivered to the door of the isolation ward for the subjects to pick up. The average SUS scores for temperature measurement and medicine delivery were 90 vs. 74 and 83 vs. 58, respectively, indicating the subjects preferred the proposed system more. The detailed average scores for each question are shown in Figure 16, where the experimental group is with the proposed system and the control group is with the comparison system. From the follow-up interview, most \begin{table}
\begin{tabular}{c c c} \hline
**Dose Card** & **Proposed System** & **Conventional System** \\ \hline
1 & 20 & 0 \\
2 & 25 & 10 \\
3 & 20 & 5 \\
4 & 25 & 15 \\
5 & 20 & 10 \\ \hline \end{tabular}
\end{table} 
Table 1: Readings of UVC dose cards (mJ/cm\({}^{2}\)). Figure 15: Experiment 3: five UVC dose cards are placed on the furniture in the smart ward.