## 3 Operational Criteria
### Mission Path Planning  
The landing point for the FPTLIR flight on-line and off-line missions is the lowest point along the ground line of the transmission line. It is important to consider potential electromagnetic interference from the phase lines under the ground lines when planning the mission path. This requires selecting safe vertical and horizontal flight trajectories and adjusting distances based on parameters such as transmission line height. The complete flight missions of the FPTLIR involves two mission intervals: an on-line interval (#1, 2, 3) and an off-line interval (#4, 5, 6). The on-line interval includes three zero-speed Points (#1), (#2), and (#3) where the robot hovers, and the off-line interval consists of three zero-speed Points (#4), (#5), and (#6). Figure 3 shows the operational path of the FPTLIR, which includes four path intervals within these mission intervals: vertical path interval on-line (VPON), horizontal path interval on-line (HPON), horizontal path interval off-line (HPOF), and vertical path interval off-line (VPOF).  
The FPTLIR takes off vertically from a secure ground Point (#1) and ascends to Point (#2), determined by the parameters of the currently inspected transmission line. At Point (#2), the vertical positional accuracy error is maintained within \(\pm\)0.1 m to ensure that the ground line remains safely positioned between the active walking wheel and the main pressure wheel. After briefly hovering, the FPTLIR continues to fly horizontally towards the ground line until it reaches Point (#3). At Point (#3), it is important to ensure that  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Transmission Line**} & \multirow{2}{*}{**Tower Height (m)**} & \multirow{2}{*}{**Vertical Clearance (m)**} & **Ground Wire Height** \\
**Voltage Level (kV)** & & & **from Ground (m)** \\ \hline
110 & 15–25 & 2–3 & 10–20 \\ \hline
220 & 30–40 & 3–4 & 20–30 \\ \hline
330 & 35–60 & 4–5 & 25–35 \\ \hline
550 & 45–75 & 5–6 & 30–40 \\ \hline
750 & 65–100 & 6–7 & 40–50 \\ \hline
1000 & 75–120 & 7–8 & 45–55 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Data on common transmission lines.  
Figure 3: The mission paths of FPTLIR.  
the ground line is aligned with the notch of the active travelling wheel and is slightly lower than the wheel. Therefore, the horizontal position error should be maintained within \(\pm\)0.04 m, which is equivalent to the width of the notch on the active travelling wheel. The FPTLIR flies down a very short distance and lands on the power line, after which it turns on the travelling system and starts walking along the power line for inspection work. Upon completion of the multi-stage inspection mission, the travelling system is switched off, and the flight system is activated. The FPTLIR will ascend a short distance, detach from the power lines, and hover at Point (#4). Afterward, the FPTLIR flies backward horizontally towards Point (#5). At this point, the position accuracy should be within \(\pm\)0.04 m to ensure landing in the safe landing zone. After a short hover period at this position, the FPTLIR descends vertically until reaching a secure landing spot at Point (#6), allowing for a maximum allowable error of \(-\)0.1 m. Among them, the flight distance during the stages of landing on and detaching from power lines is extremely short and the hovering time at Points (#2) and (#4) is very short, resulting in negligible energy consumption. Therefore, we will exclude the energy consumption analysis during these stages.