In order to improve the operation safety of launch and recapture,the deep sea remotely operated vehicle(ROV) usually has to equip with heave compensation system under rough sea states. The semi-active heave compensation method based on the servo-valve controlled asymmetric servo-cylinder is investigated in this study. Firstly,the semi-active heave compensation system,which is very similar to the actual one,is introduced about the system configuration and working principle. Considered the effect of the elast...