# Research on the Dynamic Control Method of CFETR Multi-Purpose Overload Robot
## 4 Simulation Validation
### CMOR Error Compensation Effects  
To calculate the CMOR position error compensation effect, CMOR joint 3 is set to do sinusoidal motion as shown in Figure 11a, and CMOR can rotate left and right to the limit position. Set the end-effector with different loads (0-2000 kg) for ARSMC controller control performance simulation, and the results are shown in Figure 11b-d. The results show that the trajectory of joint angular error and position error in the simulation process is smooth and there is only damping oscillation at the beginning stage. The maximum tracking error of the joint angular displacement is less than 0.01 rad, and the maximum position error of the end-effector along the \(Z\)-axis is about 0.1 m. The absolute position  
Figure 10: Position errors of CMOR end-effectors under different loads (**a**) Position error of \(X\)-axis under different loads (**b**) Position error of \(Y\)-axis under different loads (**c**) Position error of \(Z\)-axis under different loads (**d**) Absolute position error of CMOR under different loads. Figure 9: Position errors of \(J_{3}\) joint and \(J_{4}\) joint under different loads (**a**) Position errors of \(J_{3}\) joint under different loads (**b**) Position errors of \(J_{4}\) joint under different loads. error of the end-effector is similar to the \(Z\)-axis position error, which shows that the position error of the end-effector mainly comes from the position error along the \(Z\)-axis caused by the self-weight of the CMOR flexible linkage and the end load. The CMOR workspace is uniformly divided into 8 parts along the \(Y\)-axis of the base coordinate system, and the CMOR position error compensation method is used for variable parameter error compensation. The compensation parameters in each gridded workspace under different end loads are calculated by the parameter identification method as shown in Table 3. The compensation parameters are brought into the ARMRC controller and recalculated, and the results are shown in Figure 12. After compensation, the end position error of CMOR along the \(Z\)-axis is less than 0.02 m, and the mean value of absolute position error is less than 0.025 m, which reduces the end position error by more than 4 times with obvious compensation effect. Figure 12b in the 0 s and 20 s position error is large, mainly due to the large variation of error values in this region and the sparse gridded workspace. The grid can be further refined to improve the position accuracy. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Location** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline Load & \(-1.278\times\) & \(-1.845\times\) & \(-1.989\times\) & \(-1.601\times\) & \(1.2377\times\) & \(1.824\times\) & \(1.9677\times\) & \(1.5654\times\) \\ (2000 kg) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) \\ Load & \(-7.5639\times\) & \(-1.1553\times\) & \(-1.2997\times\) & \(-1.0945\times\) & \(7.1556\times\) & \(1.1316\times\) & \(1.2758\times\) & \(1.0448\times\) \\ (1000 kg) & \(10^{-3}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-3}\) & \(10^{-2}\) & \(10^{-2}\) & \(10^{-2}\) \\ Load & \(-5.1178\times\) & \(-8.1092\times\) & \(-9.5541\times\) & \(-8.4212\times\) & \(4.5582\times\) & \(7.8585\times\) & \(9.3027\times\) & \(7.8615\times\) \\ (500 kg) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) \\ No load & \(-2.6475\times\) & \(-4.7373\times\) & \(-6.1861\times\) & \(-5.9613\times\) & \(2.0227\times\) & \(4.4708\times\) & \(5.9173\times\) & \(5.3341\times\) \\ \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) & \(10^{-3}\) \\ \hline \end{tabular}
\end{table} 
Table 3: Compensation value at the corresponding spatial position of \(J_{3}\) joint (rad).