## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Manufacturer**} & \multicolumn{2}{c}{**Cobalt Robotics**} & \multirow{2}{*}{**OTSAW**} & \multicolumn{2}{c}{**KNIGHT -SCOPE**} & \multirow{2}{*}{**ZMP**} & \multirow{2}{*}{**RAD**} & \multirow{2}{*}{**SMP**} \\ \hline Model & COBALT & O-R2 & K5 & PATORO & ROAMEO & S5.2 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Dimension \\ (m) \\ \end{tabular} } & Length & 0.533 & 0.38 & 0.914 & 0.8 & 1.8 & 1.42 \\  & Width & 0.533 & 0.4 & 0.851 & 0.654 & 1.2 & 0.78 \\  & Height & 1.549 & 1.15 & 1.588 & 1.089 & 1.9 & 1.32 \\ \hline \multicolumn{2}{c}{Weight (kg)} & 68 & 15 & 181 & 99 & 440 & 110 \\ \hline \multicolumn{2}{c}{Terrain capacity} & Indoor & Indoor & In/Outdoor & Outdoor & Outdoor & Outdoor \\ \hline \multicolumn{2}{c}{Speed (km/h)} & Avg. & 3.2 & & & 9 & 4 \\  & Max. & 9.7 & & 4.8 & 6 & 12.1 & 6 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Power \\ system \\ \end{tabular} } & Type & LIB & & & LIB & LIB \\  & Size & & 20 (Ah) & & & 3.1 (kWh) & 200 (Ah) \\ \cline{1-1}  & Charging & & & & & 5.12 (kWh) \\ \cline{1-1}  & time (h) & & 9 & & 9.6 & 4 (fast) \\ \cline{1-1}  & Operating & & & & 28.7 & 12–16 \\ \cline{1-1}  & time (h) & & 10 & & (stand-by) & (patrol) \\ \cline{1-1}  & Range (km) & & & & & 24 \\ \hline \multicolumn{2}{c}{References} & [1; 2; 3] & [4] & [5; 6; 7] & [8] & [9] & [10; 11] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of current security robot models. Figure 1: Size and appearance of current security robot models. COBALT, O-R2, K5, PATORO, ROAMEO, and S5.2 (from left to right). methods for deterring crime. Within the physical security field, we identified a niche that is not covered by existing battery-powered robots. We propose that an alternative power source that suits the needs of security robots performing long-duration missions would be a hydrogen fuel cell. Thanks to its quick refueling in a few minutes, they need not leave off and use shift work any longer. Therefore, a single unit would be sufficient in most scenarios. By combining fuel cells with batteries, we developed a hybrid power system (HPS) for use in security robots with versatile capabilities. It is expected that in the developed HPS, the fuel cell can compensate for the insufficient energy density of the battery, and the battery can compensate for the slow transient response and relatively high power-generation cost of the fuel cell. Furthermore, if an abnormality occurs in either of these two power sources, although limited in performance, it is possible for each source to supply power to the load independently, leading to an increase in the operational reliability of the HPS. This paper is intended to present our best practices for developing a HPS for application in security robots, with a focus on the early specification development phase. The remainder of this paper is organized as follows. In Section 2, we comprehensively compare several HPS structures and select the best configuration for our security robot. In Section 3, we determine component specifications based on the main development goals of our security robot. In Section 4, we present a simulator that allows us to verify whether the determined specifications are valid. In Section 5, we simulate a few critical operating conditions. Finally, we conclude this paper in Section 6.