## 2 Design of the Joint Module
### Virtual Prototype Construction and Moment Simulation
In SolidWorks, the shape of each part was designed, and the densities of the components in the material configuration were set to the entity densities calculated in Table 3. The final 3D model was fabricated as an assembly and saved as an x_t file. When creating a new model in MSC Adams and choosing to import the generated x_t file, the 3D model is imported into the MSC Adams model as an entity. Figure 5 presents the 3D model of the self-driven AACMM. The 3D model imported into MSC Adams inherits the spatial location, entity volume, centroid coordinates, and custom density from the SolidWorks environment. The initial position of the model after it is imported into MSC Adams is the same as that in SolidWorks, but assembly relationships are no longer enforced, and the corresponding constraints between joints and the ground must be added according to the rotation relationships between joints. First, the Joint 1 input was fixed to the ground. We then attached a fixed hinge to the ground and added a rotating hinge for Joint 2. The axis of rotation was set to the center axis of the motor, and the remaining joints were connected using another fixed hinge, as shown in Figure 6a. For Joint 2, regarding MSC Adams hinge motion (joint motion), a column shape was selected for rotational motion. Figure 5: 3D model imported in MSC Adams View. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Part** & **Part Name** & **Part Mass** & **Volume (g)** & **Volume Ratio (\%)** & **Model Mass** & **Model Density** \\
**Index** & **Part Name** & **(g)** & **(cm\({}^{3}\))** & **Ratio (\%)** & **(g)** & **(g/cm\({}^{3}\))** \\ \hline A1-1 & Joint 1 input (including & & & 6627.71 & 42.52 & 5154 & \\  & Motor 1) & & & & & \\ A1-2 & Joint 1 output & 10,610 & 2544.69 & 16.33 & 1979 & 0.78 \\ A2-1 & Joint 2 input & & 3729.58 & 23.93 & 2900 & \\ A2-2 & Joint 2 output & & 2684.65 & 17.22 & 2089 & \\ \hline M2 & Motor 2 (including brake) & 2100 & 849.22 & 100 & 2100 & 2.47 \\ A2-A3 & Joint 2–3 link rod & 293 & 164.56 & 100 & 293 & 1.78 \\ \hline A3-1 & Joint 3 input (including & & & & & \\  & Motor 3) & & & & & \\ A4-1 & Joint 4 input & 7023 & 942.48 & 30.53 & 2144 & \\ A4-2 & Joint 4 output & & 1336.23 & 43.29 & 3040 & 2.28 \\ A4-2 & Joint 4 output & & 808.29 & 26.18 & 1839 & \\ \hline M4 & Motor 4 (including brake) & 1250 & 270 & 100 & 1250 & 4.63 \\ A4-A5 & Joint 4–5 link rod & 200 & 112.48 & 100 & 200 & 1.78 \\ \hline A5-1 & Joint 5 input (including & & & & & \\  & Motor 5) & 5290 & 628.32 & 56.37 & 2982 & \\ A6-1 & Joint 6 input & & 486.30 & 43.63 & 2308 & \\ \hline A6-2 & Joint 6 output & 1087 & 622.10 & 89.50 & 973 & \\ P & Probe & & 73.00 & 10.5 & 114 & 1.56 \\ \hline M6 & Motor 6 (including brake) & 700 & 121.64 & 100 & 700 & 5.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: 3D part mass distribution. The selected shape was then added to a rotating hinge, and the added drive property was edited to ensure constant angular acceleration. To accomplish this, the property type was set to acceleration, and the angular acceleration value was set as \(10^{\circ}\)/s\({}^{2}\) (0.1745 rad/s\({}^{2}\)). The rest joints were locked with fixed hinges, and the initial pose of the model simulation is shown in Figure 6b. We set the simulation time to 6.9 s, meaning Joint 2 will rotate from 0\({}^{\circ}\) to 240\({}^{\circ}\), and set the compensation to 100 steps to complete the simulation. The simulated moment curve is presented in Figure 7, where the maximum moment is 118.11 N\(\cdot\)m.  
The moment curves of the other joints were also obtained through MSC Adams simulation. The maximum values of the curves are listed in Table 4, and the maximum moment values that each joint can provide by Table 2 are listed in the last two columns of Table 4. Comparing and analyzing the data in Table 4, we conclude that the selected motor and reducer meet the system requirements. However, there are some discrepancies between design and simulation, and we believe there is still room for further structural optimizations and weight reduction.