## 2 Design of the Joint Module
### Virtual Prototype Construction and Moment Simulation  
Virtual prototyping technology is a novel computer-aided engineering technology that enables design analysis through simulations of all or part of the physical prototype functions on the platform [33]. In this study, SolidWorks 2015 3D CAD software was used for modeling, and MSC Adams was used to establish a virtual prototype of the self-driven AACMM. The moment curves of the joints were obtained through computer simulations of machine motion, and the selections listed above were verified. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Joint/Parameter** & **Joint 1** & **Joint 2** & **Joint 3** & **Joint 4** & **Joint 5** & **Joint 6** & **Probe** \\ \hline Total mass (g) & 5555 & 6586 & 6043 & 4448 & 4034 & 3344 & 1087 \\ Centroid distance (mm) & 140 & 450 & 130 & 380 & 100 & 150 & - \\ Angular acceleration (\({}^{\circ}\)/s\({}^{2}\)) & 10 & 10 & 20 & 20 & 30 & 30 & - \\ Maximum inertia moment (N-m) & 20.04 & 18.17 & 6.46 & 6.37 & 0.20 & 0.16 & - \\ Maximum load moment by gravity (N-m) & 0.00 & 136.31 & 38.49 & 38.49 & 1.60 & 1.60 & - \\ Peak moment (N-m) & 20.04 & 154.48 & 44.95 & 44.86 & 1.94 & 1.90 & - \\ Deceleration ratio & 120 & 120 & 100 & 100 & 50 & 50 & - \\ Minimum moment required for motor (N-m) & 0.17 & 1.29 & 0.45 & 0.45 & 0.04 & 0.04 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of motor torsion estimation [31]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Joint 1/Joint 2**} & **Joint 3/Joint 4** & **Joint 5/Joint 6** \\ \hline \multirow{4}{*}{Motor} & Rated moment & \multirow{2}{*}{1.6} & \multirow{2}{*}{0.5} & \multirow{2}{*}{0.1} \\  & (N-m) & & & & \\ Mass (g) & 1800 & 1050 & 500 \\ \hline \multirow{4}{*}{Harmonic reducer} & Mass (g) & 1240 & 560 & 380 \\  & Peak moment & \multirow{2}{*}{159} & \multirow{2}{*}{51} & \multirow{2}{*}{17} \\  & (start/stop) (N-m) & & & & \\ Maximum moment & \multirow{2}{*}{289} & \multirow{2}{*}{104} & \multirow{2}{*}{33} \\  & (instant) (N-m) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Primary parameters for the motor and reducer. By combining the pitching and rolling joint configurations in Figure 2 with the primary parameters in Table 1, a 3D model was designed in SolidWorks. A distribution diagram of each part is presented in Figure 3. For the convenience of MSC Adams simulation, an effective merging of the parts to create a model of the self-driven AACMM was performed. 1. The cylindrical radii of the rotating parts of the joints in the model were set to the ideal cylindrical radii. 2. The output portion of Joint 1 was merged with the input portion of Joint 2, the output portion of Joint 3 was merged with the input portion of Joint 4, and the output portion of Joint 5 was merged with the input portion of Joint 6. 3. Joints 1 and 2 (excluding Motor 2) constituted a union with uniform density. The masses of the input and output parts of Joints 1 and 2 were distributed proportionally to their proportions of the total volume of the union. 4. Joints 3 (not including the front connecting rod) and 4 (excluding Motor 4) constituted a union with uniform density. The masses of the input and output parts were also distributed according to their volume proportions. 5. Joints 5 and 6 were treated the same as Joints 3 and 4. 6. The output portion of Joint 6 and the measuring head constituted a union with uniform density. Again, the component mass was distributed according to the volume proportions. The components of the 3D model following mass distribution are listed in Table 3. The angle ranges and hinge relationships of Joints 1 and 2, 3 and 4, and 5 and 6 are presented in Figure 4.  
Figure 4: Schematic diagram of the angle ranges and hinge relationships of each joint, they should be listed as: (**a**) Description of what is joints 1 and 2, (**b**) Description of what is Joints 3 and 4, (**c**) Description of what is joints 5 and 6. Figure 3: 3D model of the self-driven AACMM.