## 1 Introduction  
With the trend of economic globalization, more and more ships are used for the development of marine business. The sea contains a variety of different marine organisms and compounds, which can be adsorbed to the outer surface of the ship and corrode the hull [1]. Long-term corrosion will increase the sailing resistance of the ship, and consequently affect the navigation efficiency of the ship. Additionally, the corrosion thinning of the hull changes the form of stress on it, causing stress concentration. Therefore, it is important to carry out destrusing regularly. At present, ship derusting is mainly completed by manual labor or robot, such as chemical, ultra-high pressure pure water jet and wall-climbing robots [2; 3; 4]. Manual derusting is faced with high operational risk, limited operation scope and low work efficiency. Although wall climbing robots might improve automation and work efficiency, they have shortcomings, such as high cost and weak ability to cross obstacles. Therefore, it is necessary to develop an automatic, economical and efficient derusting robot. Cable-driven parallel robots (CDPRs) are a relatively new type of robot that uses cables to realize the pose control of the motion platform [5]. Since they have advantages of a large workspace, simple structure and low cost, CDPRs are widely used in aerospace, medical and marine fields [6; 7; 8; 9]. The August Design Company [10] developed 6-DOF CDPRs for sports event broadcast; the motion platform can move at a speed of 13 m/s. China's Xidian University [11] proposed the Five-hundred-meter Aperture Spherical Telescope (FAST), which was completed and put into operation in 2016. [PERSON] [12] proposed a floating cable-driven marine platform, which used the Stewart-Gough parallel manipulator as a support structure. [PERSON] and [PERSON] [13] proposed a 6-DOF parallel marine manipulator, and the influence of cable layouts on the dynamic performance and workspace of the parallel robotic marine platform (PRMP) was analyzed. It can be seen that CDPRs have been widely used. Inspired by the aforementioned successful applications, this article combines CDPRs and derusting equipment to design a new type of cable-driven parallel derusting robot (CDPDR). The CDPR is used to move the position of the derusting equipment to the operating area. The derusting equipment is mainly composed of a water gun and a bucket, where the bucket is used to store chemical derusting reagents, which are sprayed to the working surface by the water gun. Finally, the derusting operation is completed by chemical reagents combined with a high-pressure water jet. Establishing an accurate dynamic model for the CDPR is the basis of control, and it has become a hot topic for researchers. Typical dynamic modeling methods include the Newton-Euler method, Lagrange method, virtual work method and Kane method [14; 15; 16; 17]. [PERSON] [18] established a dynamic model of a fully constrained CDPRs by the Newton-Euler method, and applied it to the rehabilitation training of human joints. [PERSON] [19] used the Lagrange method and the zero-space method to derive the dynamic model of the plane cable-driven manipulator, which took into account the cable rigidity and the inertia of the winch. [PERSON] [20] applied the Newton-Euler method to establish the dynamic model of a cable-driven parallel platform for underwater camera stabilization, and conducted in-depth research on the influence of external disturbances, such as waves. However, most existing research has been focused on traditional CDPRs installed on a fixed base, while the influence of the base motions on the CDPRs has largely been ignored. In this article, a dynamic model of CDPDR with the ship's base motions is established based on the Newton-Euler method. Since the ship's base motions are time varying and nonlinear, the modeling process in this article is more challenging and complicated, compared to traditional research.