Time-domain simulation of a composite electro-hydraulic heave compensation system for the underwater tethered platform

A composite electro-hydraulic heave compensation system that can work under two modes, i. e., the passive mode and the semi-active mode, based on an asymmetric servocylinder controlled by a servo-valve is investigated in this paper. Firstly, this composite heave compensation system, which is scaled according to the principle of similarity from its prototype system, is introduced about the system configuration and its working procedure. Based on the transfer function of the electro-hydraulic system and the nonlinear relationship between input voltage and output velocity of the asymmetrical cylinder, a piece-wise feedforward controller is obtained to improve the dynamic performance. The two modes of this composite heave compensation system are then built and simulated in the AMESim environment, lastly, the scaled ship have motion is reproduced, the resonance zone and the compensation efficiency is discussed. The simulation results show the effectiveness of the system.