Experimental Study On Key Problems Of Wave Heave Compensation Hydraulic Platform

The dissertation focuses on building a wave compensation hydraulic platform which has the generalized heave motion compensation function. The generalized heave motion amplitude of platform will decline more than the deck's generalized heave motion by hydraulic system. So there will be a local zone on the ship, which can overcome the impact of ship movement (rolling, pitching and heaving) and keep the relative balance of the ships. Thereby, the system can enhance work efficiency and the safety of jobs , such as landing platform of shipborne helicopters, cargo replenishment between ships, missilery replenishment of warship, and abyssal mining.The research is carried out by theory analysis, computer simulation and model test in the dissertation. The main problems that will be solved in this paper are as the following:Scheme design of the heave compensation platform system is completed by using the electro-hydraulic proportional technique after seakeeping capability testing, arranged for afterward research.Data acquisition,pretreatment and usability enhancing of ship movement. This paper builds up a processing scheme of acceleration signal integral based on frequency domain integral of FFT time-frenquency transforming blending filter technique and polynomial trend eliminating. We solve the problem of acceleration signal transform to displacement signal, which is not available by time domain integral, and condenses the integral time consuming, and establishes the basement for afterward research.The mathematic model of the heave compensation experimental system is established in the paper. A differential equation and an NARMAX model are set up according to system identification theory and combining with experimental data. This paper applies a two-way recursive identification algorithm based on equal dimension new information and inverse matrix calculation to determine the parameters of the optimal NARMAX model only by littleness arithmetic labor. After force analysis and Joint Modeling for moving mechanism of the system, we get displacement-force mathematical relation of the system.Using time series analysis to forecast generalized heave motion, a real-time multi-step prediction algorithm based on auto-regressive model (AR model), a real-time multi-step prediction algorithm based on auto-regressive moving average model (ARMA model) and a real-time multi-step prediction algorithm based on nonlinear polynomial auto-regressive model (PAR model) are analyzed and compared .A multiplex controller, combining feedforward and feedback control strategy, can improve the compensating precision of the heave compensation system. The displacement coordination control strategy can suppress the inconsistent forces that result from the inconsistent movements of the cylinders. The force feedback control strategy is advantaged for attenuation of oscillations and coordination of forces. A predictive control scheme can effectively solve the big delay problem of the heave compensation system.