## 6 Conclusions  
This article proposes a new type of marine automatic derusting robot, which aims to solve the problems of low efficiency and high operation risk in traditional derusting. To improve the overall modeling accuracy, the dynamic model, including ship excitation and external disturbance, is deduced. The controllable workspace of CDPDR is analyzed, and the results show that the size or rotation angle of the motion platform are closely related to the controllable workspace. For CDPDR of this configuration, it should be possible to reduce the size of the motion platform and increase the controllable workspace. Moreover, the cable tension is optimized based on the least variance method, and the optimized cable tension changes smoothly and continuously. To improve the robustness and accuracy of trajectory tracking, an ANF-TSMC control strategy is designed. Furthermore, CDPDR is simulated and analyzed for two different scenarios. In the condition without wave excitation, the maximum trajectory error is 4 mm, and the maximum angle error is 0.6\({}^{\circ}\). The final trajectory error is 3.8 mm, and the final angle error is 0.5\({}^{\circ}\). In the condition with wave excitation, the maximum trajectory error is 3 cm, and the maximum angle error is 1\({}^{\circ}\). The final trajectory error is 6 mm, and the final angle error is 0.6\({}^{\circ}\). The results show that the control strategy has the characteristics of high control accuracy, finite-time convergence and strong robustness. The research result can provide a theoretical basis for engineering application of CDPDR in the field of ship maintenance.  
In addition, before carrying out the prototype experiment, it should be noted that the dynamic model established herein does not consider cable mass and elasticity. Although it has little effect on the overall modeling accuracy, there are still errors compared to the actual working conditions. In addition, this article does not establish a model of the nonlinear motion of the ship, which is still different from the actual working conditions. In the future work, the above issues will be further studied. The prototype of CDPDR will be established, and the proposed strategy and prototype performance will be fully verified in practical scenarios.  
Conceptualization and methodology, J.L., Y.C., S.W., G.H. and Y.S.; software, J.L. and Y.C.; validation, J.L., Y.C. and S.W.; writing--original draft preparation, J.L.; writing--review and editing, J.L., Y.C., W.L. and S.W.; supervision, S.W., G.H. and Y.S.; funding acquisition, S.W. All authors have read and agreed to the published version of the manuscript.  
This work was financially supported by the National Key Research and Development Program of China (Project No. 2018 YFC0309003), the National Natural Science Foundation of China (Project No. 52101396), and the China Fundamental Research Funds for the Central Universities (Project No. 3132022207, 3132022341). [PERSON] was supported by the China Scholarship Council for 18 months study at Georgia Institute of Technology.  
Not applicable.  
Figure 13: (a) Trajectory tracking without wave excitation; (b) Trajectory tracking with wave excitation.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data available on request due to restrictions, e.g., privacy or ethical. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to research group policy.  
**Conflicts of Interest:** The authors declare no conflict of interest.