## 5 Self-Insulation Performance Simulation Analysis  
The insulation performance of the flexible joint is the most crucial part along the mechanical arm. In order to examine the electric field strength distribution of the joint under a certain voltage level, this manuscript constructs a finite element model based on the simulation environment. The insulation materials and parameters are set for the mechanical arm components. The simulation diagrams of the potential and electric field distribution in different planes of the mechanical arm under the 220 kV voltage level are given in Figure 10. The material settings of the components are shown in Table 2. Among them, the center of the bottom surface of the groove of the moving platform and the fixed platform coincides with the center of the bottom surface of itself, and the four openings on the moving platform and the fixed platform are distributed on the platform surface with equal arc lengths. In this finite element simulation, the mesh density is controlled by the geometric shape of the robot. The minimum mesh size in this simulation model is about 0.005 m, the unit type is tetrahedral unit, and the solver is the built-in Newton iteration solver of COMSOL 6.0. The materials used in the simulation were selected based on the robotic arm's recommended specifications. The main structure was constructed using epoxy resin, while the driving tendons were made of polyester fiber. A comparison of their properties with several common materials is presented in Table 2. As shown, epoxy resin exhibits a favorable combination of bending strength, elastic modulus, and density, making it well-suited as a lightweight, self-insulating, and rigid structural material for the robotic arm. On the other hand, polyester fiber, with its relatively low bending strength but high tensile strength, is appropriate for tendon applications. In the finite element simulation of insulation performance, the influence of the insulating tendon material was negligible, and thus, the tendon section was temporarily omitted. In the selection of materials for the self-insulating rope-driven manipulator working in a live environment, after a comprehensive comparison of the performance of various resin-based materials, it was finally determined that epoxy resin was used as the main material of the manipulator and polyester resin was used as the driving rope material. Epoxy resin has a high tensile strength of 50-120 MPa and an excellent bending strength of 400-800 MPa, which can meet the requirements of the main body of the manipulator for structural strength and durability. At the same time, its elastic modulus of 2.5-4.5 GPa ensures rigidity while avoiding material brittleness. The low density of 1.1-1.4 g/cm\({}^{3}\) helps to achieve lightweight design, and the dielectric strength of 15-22 kV/mm ensures sufficient insulation performance. These performance indicators are significantly better than phenolic resin (30-60 MPa tensile, 100-300 MPa bending) and silicone (10-40 MPa tensile, 50-150 MPa bending) and can better meet the requirements of the main body of the manipulator for structural strength. At the same time, the elastic modulus of epoxy resin \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Tensile** & **Flexural** & **Elastic** & \multirow{2}{*}{**Density** **(g/cm\({}^{3}\))**} & **Dielectric** & \multirow{2}{*}{**Selection**} \\  & **Strength** & **Strength** & **Modulus** & **(g/cm\({}^{3}\))** & **(g/cm\({}^{3}\))** & **Strength** & **Selection** \\  & **(MPa)** & **(MPa)** & **(GPa)** & **(kV/mm)** & & \\ \hline Epoxy resin & 50–120 & 400–800 & 2.5–4.5 & 1.1–1.4 & 15–22 & \(\surd\) \\ Polyester resin & 40–90 & 180–400 & 2.0–3.5 & 1.2–1.4 & 10–15 & \(\surd\) \\ Phenolic resin & 30–60 & 100–300 & 2.0–3.0 & 1.3–1.5 & 10–15 & \(\times\) \\ Silicone & 10–40 & 50–150 & 1.0–2.0 & 1.1–1.3 & 15–25 & \(\times\) \\ Polyimide & 70–120 & 200–500 & 3.0–5.0 & 1.4–1.6 & 20–30 & \(\times\) \\ \hline \hline \end{tabular}
\end{table}