Research On The Design And Control Of Heave Compensation Systems For Offshore Operations

The accuracy,safety and efficiency of the offshore operation must be guaranteed due to the hash sea conditions.The offshore platforms are excited by irregular waves,which generate heave motion.The heave motion has an adverse effect on the overall hoisting structure and the precise positioning of the payload.The heave compensation system can decouple the load motion from the heave motion of the vessel,and compensate the irregular heave motion of the load.The heave compensation system is usually divided into passive heave compensation system,active heave compensation system and active passive hybrid heave compensation system.Passive heave compensation system do not need external energy input,but they are usually with low compensation accuracy and large time lag.Active heave compensation systems have high compensation accuracy but sufer from low energy efficiency.Therefore,the active passive hybrid heave compensation system is researched in this study.The details are as follows:In chapter 1,the research background and status of electro-hydraulic heave compensation systems were described.The development and application of heave compensation systems were described in detail.The working principle,advantages and disadvantages of various heave compensation systems are introduced.Finally,the main research contents of this study were given based on the review of heave compensation systems.In chapter 2,a heave motion predictor was proposed.A parametric predictive model is established by employing the nonlinear tracking differentiator and FFT,which captures the characteristics of the heave motion.Then a novel Variational Bayesian based strong tracking Kalman filter was designed to cope with the model uncertainties,and obtain the accurate process and measurement noise matrices.The estimated heave motion state will be used to calculate the parameters of the predictive model.The simulation was conducted based on real heave motion measured by MRU.The results showed that the proposed predictor has a good prediction performance.In chapter 3,a passive heave compensation system based on accumulators was designed.The dynamic model of the passive compensation system was established.The main parameters of the system were calculated.The parameters that affect the performance of the system were simulated and analyzed in Matlab and AMESim.In chapter 4,the electro-hydraulic system of the active passive hybrid heave compensation system was designed,and the mathematical model of the system was established.In the active part,the valve and pump combined control method was adopted,so that the electro-hydraulic system can ensure the high tracking performance and high energy efficiency at the same time.The adaptive robust position controller and the adaptive robust pressure controller were designed respectively.Finally,the electro-hydraulic system model of the heave compensation system was built based on the AMESim and Matlab joint simulation flat.The control accuracy of the designed algorithm was verified.And the effect of the predictive control strategy combined with the heave predictor used in the heave motion compensation system was verified.In chapter 5,the major research work of the study was summarized.And then,suggestions for further study on this subject were presented.