Volume 10 Issue 3 ( September 2023 )

Inverse dynamics model of the manipulator system combined with ship motions is required in order to size the electrical motor performance for ship-mounted subsystems. This study examines a sizing methodology by developing an integrated dynamical model of a two-DoF manipulator system mounted on the ship by using Lagrange-Euler method and simulating ship motions using ANSYS AQWA. Given the parameters of manipulator links and six-DoF ship motions, joint torques of a two-DoF manipulator and its electrical motors can be calculated by including the mechanical transmission. Under variations of wave direction with the JONSWAP spectrum applied, the results show that the ship motions significantly contribute to the mechanical and electrical manipulator torques, with the highest value at the 90o wave direction (beam sea) for the azimuth motor and at the 45o wave direction (quartering sea) for the elevation motor. The results can be used to size the motor torque specification by taking into account the random wave-induced ship motions and they can be extended to the development of a robust control system for the manipulator system.

Keywords: Electrical Motor, Two-DoF Manipulator, Inverse Dynamics, Lagrange-Euler, Hydrodynamics Response