Search

Heave compensation systems are of great importance to the safety and efficiency of marine operations subject to irregular-wave excitation. While many efforts have been made to improve the displacement compensation control, only a few of researchers pay their attention on tension compensation control. This paper presents an adaptive robust integral sliding mode control (ARISMC) based on the back-stepping method to realize constant tension control of hybrid active-passive heave compensator (HAHC) applied to heavy deep-sea towing systems. The proposed ARISMC is intended to overcome the effects of parametric uncertainties, uncertain nonlinearities, and external disturbances in the electro-hydraulic system of HAHC. The stability of the whole system is proved using common Lyapunov method. To verify the effectiveness of the proposed controller, we carried out a number of simulations and experiments using the measured heave motion data under different sea conditions. The results demonstrate that the ARISMC controller presented in this paper has better advantages than the traditional PI controller in the accuracy and robustness of tension compensation.

For the purpose of researching the displacement control system of heave compensation for offshore drilling platform, a set of crane type active and passive combined heave compensation device are designed on the basis of the similarity principle. As it known that platform heaving will be caused by the wind, sea wave and ocean current when conducting the drilling operations on the offshore drilling platform, which then will disturb the drilling operation. Therefore, the compensation device must be adopted to keep the vertical relative motion between the drill string system and the drilling platform to zero during the operation. Meanwhile, to improve the real-time performance of the heave compensation, the control system is optimized by establishing the simulation model of the active-passive combined crane, and LS-SVM (Least Squares Support Vector Machine) is improved by the artificial immune algorithm to predict the motion trend of offshore platforms. Eventually, in order to acquire the best control scheme, the Proportion Integration Differentiation (PID), fuzzy PID, BP neural network PID control method are utilized to carry out the simulation analysis, and the BP neural network PID control is found to be the optimum. Experiments showed that after using the BP neural network PID control algorithm, the displacement compensation rate of hook for active-passive combined crane device is more than 90%, the performance of the heave compensation is better, and the control is in time.

Heave compensation systems are widely used to decouple the load motion from wave-induced vessel motion for the equipment handling on the ocean. Researches have been made to achieve successful compensation, yet few of them discusses the inherent constraints of the systems, such as bounded compensator's stroke and max actuator's velocity. This paper presents a solution for active heave compensation systems with such constraints by means of variable structure control. The controller's complexity on design procedures and effectiveness are compared with a trajectory planning control method which turns out that the variable structure controller is more suitable to apply to the active heave compensators. The back-stepping method is used to robustly stabilize this variable structure system and for the aim of a decrease on the high robust gain due to uncertain friction term, a modified decoupled friction observer is used which is also verified by both theoretical and experimental analyses. To compensate for the time delay of the motion reference unit (MRU), a heave prediction algorithm is used. The experimental results show that most heave motion can be compensated when the motion and its velocity are feasible, while no hit occurs otherwise.

Ploveće dizalice, koje prenose koristan teret tijekom izvođenja radova na otvorenom moru, moraju zadovoljiti rigorozne zahtjeve u pogledu učinkovitosti i sigurnosti u teškim uvjetima, dok ih iznenadno gibanje ploveće dizalice prouzročeno valovima, čini još težim. U radu se analizira dinamika ploveće dizalice i upoznaje s aktivnim sustavom za kompenzaciju dizanja i spuštanja broda (heave compensation system - HCS) s kojim se postiže pomicanje tereta nezavisno od gibanja broda prouzročenog valovima u uspravnom smjeru. Točnije, uvodi se virtualna tehnologija stvaranja prototipa za sustave plovećih dizalica s ciljem istraživanja stvarnog djelovanja HCS-a. Stvoren je virtualni mehanički model ploveće dizalice kako bi se analizirala dinamika dizalice. Uz to, konstruiran je aktivni HCS za potpogonjeni sustav ploveće dizalice. Za bitan dio HCS-a predlaže se zakon samopodesivog PID upravljanja zasnovan na poboljšanom genetskom algoritmu. Zajednička simulacija i eksperimentalni rezultati pokazuju da se pomicanje tereta zbog vertikalnog gibanja broda može značajno smanjiti u teškim morskim uvjetima., The floating cranes, which transfer payloads during offshore constructions, need meet rigorous demands for efficiency and safety in serious sea conditions while the unexpected motion of the floating crane caused by wave make it even harder. This paper analyses the dynamics of a floating crane and presents an active heave compensation system (HCS) to allow the payloads motion decoupled from the wave-induced ship motion in the vertical direction. Specifically, virtual prototyping technology is introduced for the floating crane systems to investigate the real behaviour of the HCS. A virtual mechanical model of the floating crane is created to analyse the dynamics of the floating crane. In addition, an active HCS is designed for the under actuated floating crane system. A self-adaptive PID control law based on improved genetic algorithm is proposed for the essential part of the HCS. The co-simulation and experiment results demonstrate that the payload motion due to the ship’s vertical motion can be reduced significantly in harsh sea conditions.