Offshore Crane Research Articles

Dynamic modeling and robust control of a multi-cable payload transfer system for offshore cranes subjected to random waves and wind loads

The payload often experiences unpredictable motion due to the combined effects of random waves and wind loads, significantly impacting the safety and efficiency of offshore operations. To expand the effective working window for offshore transfer operations, this study introduces a multi-cable payload transfer system (MPTS). Using a 45-ton offshore crane mounted on a multipurpose vessel from COSCO Shipping Group as a prototype, this study establishes a dynamic model of MPTS, considering the effects of vessel motion, crane actions, and wind loads. The payload remains in an unstable state due to external disturbances. Additionally, variations in payload specifications and mass lead to considerable uncertainties in the dynamic parameters of MPTS. To address these uncertainties, a second-order linear observer is developed. Subsequently, an improved computed torque controller is proposed, and the boundedness of the tracking errors is proven using the Lyapunov theory. The transfer process is divided into three distinct phases: lifting, slewing, and lowering. The feasibility of the transfer scheme is verified through high-fidelity simulations and prototype experiments. This research provides a solid theoretical foundation for the subsequent engineering application of MPTS.

Virtual prototype modeling and fuzzy control of the heave compensation system for a 500-ton deep-sea mining vessel

The unexpected heave motion of vessels generated by waves has always threatened the safe operation of mining vessels. The heave compensation system is a critical equipment for offshore cranes to ensure the safety and stability of the deep-sea mining vessel operation. Unfortunately, the nominal load of the mining vessel transporting minerals has become increasingly large, which has led to the dynamic performance of the heave compensation decline and a significant increase in energy consumption. To solve these problems, a semiactive heave compensation system and fuzzy logic-based controller are proposed in this paper. First, an active-passive hybrid heave compensation system is designed to reduce energy consumption greatly. The virtual prototype models of the proposed heave compensation system in a 500-ton deep-sea mining vessel are also built. Then, an adaptive tuning PID controller is developed based on the Transfer function of the heave compensation system and Mamdani-type fuzzy logic. Virtual prototype simulation results of AMESim-Simulink joint simulation illustrate that the accuracy of compensation for the four or six sea states reaches more than 90% with the proposed method and the power of the active compensation system is about 21% of the total power. Finally, the experimental results are included to demonstrate the effectiveness of the proposed semiactive heave compensation system.

Model experimental studies on active heave compensation control strategy for electric-driven offshore cranes

Ship-mounted heave compensation offshore cranes are indispensable for isolating connected payloads from the support vessel during lifting operations under harsh sea conditions. In this paper, an innovative adaptive robust control strategy is presented for the electric-driven active heave compensation (EDAHC) system, combining an equivalent model predictive control (EMPC) method with a bias proportional integral derivative (BPID) framework to effectively mitigate the adverse effects of wave-induced heave motions from the support vessel on the suspended payload. Building upon the inherent field-oriented control in the permanent magnet synchronous motor (PMSM), the BPID-based control structure is introduced, motivated by its prompt responsiveness and robust resistance against model discrepancies and irregular disturbances. Facilitated by a torque compensation mechanism, the EMPC-based control scheme, synthesized with an autoregressive integrated moving average (ARIMA)-based heave motion prediction algorithm, is subsequently developed to achieve nonlinear friction deadzone correction and adaptive regulation of BPID parameters, thereby ensuring optimal performance of the EDAHC system within specified state and input constraints. Comparative experimental tests conducted on a scaled EDAHC testbed validate the superior capabilities of the proposal in station-keeping, position tracking, constraint satisfaction, and robustness against parametric uncertainties.

Antiswing control of offshore cranes under ship rolling disturbances: an active disturbance rejection control based approach

Antiswing control of offshore cranes under ship rolling disturbances: an active disturbance rejection control based approach

Feasibility Study on Recovering Human-Occupied Vehicle with An Offshore Crane

Feasibility Study on Recovering Human-Occupied Vehicle with An Offshore Crane

Dynamic Modelling and Experimental Analysis of an Offshore Crane Payload Positioning System with a Parallel Cable-Driven Method

Dynamic Modelling and Experimental Analysis of an Offshore Crane Payload Positioning System with a Parallel Cable-Driven Method

Cascade NMPC-PID control strategy of active heave compensation system for ship-mounted offshore crane

In this paper, the problem associated with active heave motion compensation during heavy-lift operations performed by ship-mounted offshore cranes beneath rough marine environment is investigated. To effectively decouple the correlated motion of the suspended payload from the support vessel via the secondary regulated active heave compensation (SRAHC) system, a novel hierarchical control strategy is proposed by integrating a cascade control structure with an adaptive robust control scheme that incorporates a vertical motion forecast algorithm based on autoregressive integrated moving average (ARIMA) model, a conventional proportional-integral-derivative (PID) framework, and a nonlinear model predictive control (NMPC) method. The introduction of the cascade structure is motivated by its prompt error response against control lag and efficient system order reduction for computational burden alleviation, which forms a crucial foundation for the NMPC-based real-time regulation of PID gains, ensuring optimal evolution of the SRAHC system while improving its practical feasibility. Furthermore, the enhancements in heave compensation and trajectory tracking performance, noise resistance, constraint satisfaction, and engineering application potential of the proposal are demonstrated through a thorough comparative analysis conducted in a practical co-simulation research system.

A novel magnetorheological anti-swing system for offshore crane: System modeling and controller design

Constrained by the unique operational conditions and the swinging motion of the payload, offshore cranes exhibit low lifting efficiency and positioning accuracy during operation. In this paper, magnetorheological (MR) technology is applied in the realm of payload anti-swing and positioning of offshore cranes for the first time. The anti-swing system adopts a parallel mechanical configuration design, offering a simple structure that does not encroach upon the crane's working space and exhibits high levels of robustness. Based on the principle of robotics, the kinematic and dynamic model of anti-swing system is derived. Co-simulation analysis is conducted to assess the swing response of the crane's payload throughout the lifting and transfer process amidst irregular ocean waves. The findings demonstrate that the MR anti-swing system effectively mitigates payload swing, achieving an anti-swing effect of over 80%. With a similar anti-swing effect, the MR anti-swing system with time-varying current reduces energy consumption by 54% compared to the system with fixed current. Subsequently, experimental results from the physical prototype reveal that the anti-swing system can suppress payload swing by over 80% during cargo transfer processes. This underscores the capability of the MR anti-swing system to enhance payload transfer efficiency and positioning accuracy.

Constrained model predictive control for 3-D offshore boom cranes

Offshore boom cranes are complex nonlinear underactuated systems, whose control problems, when considering the 3-dimensional (3-D) model affected by ship-induced disturbances, are full of various challenges. In fact, it still remains an open problem to efficiently control the 3-D offshore boom cranes. Moreover, most existing works on offshore cranes concentrate upon designing the force/torque controller, whose performance degrades badly in the presence of friction. In this paper, considering the above issues, a novel model predictive control (MPC) method, which successfully considers the constraints of both input and output of the system, is proposed to achieve satisfactory control performance even under the effect of persistent ship roll and heave perturbations. Specifically, a discrete model is first obtained by some careful transformation and discretization on the unactuated dynamics equations, based on which a novel model predictive controller is constructed. To reduce the complexity of the system, the unactuated states and the accelerations of actuated states are considered as system states and control inputs respectively. After that, the requirements for the payload position accuracy and swing suppression as well as other system constraints, are taken into full account by converting them into input constraints to facilitate subsequent handling. At last, hardware experiments are implemented on a self-built testbed, with the obtained results clearly illustrating the effectiveness and robustness of the proposed method.

NMPC-PID control of secondary regulated active heave compensation system for offshore crane

In this paper, an offshore crane driven by a secondary controlled unit (SCU) which offers advantages in terms of high dynamic behavior and energy efficiency is investigated. To counteract the negative impact of the support vessel's heave motion on the station-keeping and trajectory tracking performance of heavy payload, an adaptive robust control scheme for the secondary regulated active heave compensation (AHC) system is proposed based on the combination of a nonlinear model predictive control (NMPC) strategy, a conventional proportional-integral-derivative (PID) control scheme and a vessel heave motion prediction algorithm. The motivation of utilizing the PID-based control structure is given by the excellent resistance against irregular external disturbances and robust capability to eliminate the uncertainties, with real-time tuning gains provided by the NMPC synthesized with the autoregressive integrated moving average (ARIMA) model to ensure optimal evolution that satisfies state and input constraints while accounting for model nonlinearities. Comparative simulation studies in the practical Simulink-based mechanical-electrical-hydraulic research system demonstrate the superior tracking and heave compensation performance, strong robustness, constraint satisfaction, and energy efficiency of the proposal.

Multi-cable anti-swing system for cranes subject to ship excitation and wind disturbance: Dynamic analysis and application in engineering

Offshore cranes generally have low working efficiency, high operating risk, and low lifting accuracy under rough sea conditions. In this study, a Multi-Cable Anti-Swing System (MCAS) is proposed in terms of a 45-ton crane of a 27,000-ton multipurpose vessel of COSCO Shipping Group as a design prototype, and it is adopted to investigate the dynamic characteristics of the MCAS for cranes within an offshore environment. The MCAS is simplified as a restricted-pendulum with ship-motion excitations, and a wind load is incorporated into the dynamic model of the MCAS. Moreover, the dynamic characteristics of the MCAS are simulated and analyzed using Matlab/Simulink, and the experiments were performed on the laboratory prototype of the crane equipped with the MCAS. As indicated by the crane operation data, the payload swing amplitude was reduced by 85% with the MCAS, which notably increased the lifting efficiency of offshore cranes. The results of this study will contribute to the in-depth optimization and engineering application of the MCAS onboard ships.

Modelling 3D dynamics of offshore lattice jib cranes by means of the rigid finite element method

Offshore cranes require particularly careful design due to the difficult environmental conditions in which they work. This paper presents a 3D model of the dynamics of an offshore crane with a truss jib formulated by means of the rigid finite element method. The inertial features of the truss members are assigned to nodes whose rotational and translational displacements are degrees of freedom. Flexible features of the truss members are modelled by massless and dimensionless spring–damping elements (sde). The computer programme developed on the basis of the model is verified and validated, and good correspondence of the authors’ own results with those obtained using commercial FEM package is achieved. Computer simulations are carried out for the light crane used on the wind platforms. The influence of the base movements (sea waves) on the system are also investigated. Lifting a load from a supply vessel and the load on the system during rotational movement of the crane are simulated too. Finally, conclusions concerning the influence of the movement conditions on the overload coefficient and deflections of the crane boom are formulated.

Dynamic Analysis of Full-Circle Swinging Hoisting Operation of a Large Revolving Offshore Crane Vessel under Different Wave Directions

Waves have an important influence on the motion performances of offshore crane vessels. The floating crane vessel in waves gives rise to the motion of the lifted object which is connected to the hoisting wire. Based on the geometric parameters of a revolving offshore crane vessel, combined with the specific process of the floating crane vessel at work, a model of the offshore crane vessel under full-circle swing hoisting has been established by OrcaFlex. With the change in wave direction, the dynamic response of the system is made and the impact force between the support vessel and the hanging object and the tension of the crane wire under different wave directions is obtained. At the same time, the minimum impact forces between the support vessel and the hanging object and the tension of the crane wire and their wave directions are obtained. According to the calculated result, the optimal design of the full-circle swing hoisting operation of large revolving offshore crane vessel has been determined.

Pay load Stabilization for Offshore Cranes: A Unified Controller Based on Flatness

Crane-based handling operations represent a vital part of today's maritime sector. To guarantee both safe and efficient payload handling with ship cranes, payload oscillations induced by the sea swell have to be damped. Approaches for payload stabilization usually consider either vertical position control (Active Heave Compensation, AHC) or sway reduction (Anti Sway Control, ASC). In this paper, a unified control scheme for spatial payload stabilization is proposed, utilizing the differential flatness of the crane system. The presented framework inverts the nonlinear payload dynamics by means of the flat mapping, thus facilitating controller design. Furthermore, the approach provides a systematic way to include the sea disturbance in the controller. Redundancy of the considered knuckle boom crane is exploited to track secondary control objectives. A related cost function weighting the crane's manipulability is derived and used in an optimization-based target selector. The controller design is evaluated in simulation for varying sea disturbances. The results suggest good AHC and ASC capabilities, where the payload's position error is reduced up to 60% for light to medium sea states.

Effect of Electrification on the Quantitative Reliability of an Offshore Crane Winch in Terms of Drive-Induced Torque Ripples

Effect of Electrification on the Quantitative Reliability of an Offshore Crane Winch in Terms of Drive-Induced Torque Ripples

Metodología para el análisis estructural de una cubierta principal de un buque FPSO soportando una grúa sobre orugas

Offshore cranes placed on the surface of Floating Production Storage and Offloading (FPSO) vessels affect the structural response of their main decks, which can alter the safe operation of the FPSO vessels. Generally, classification societies rules are used to predict the structural strength of the main deck of FPSO vessels. However, these classification societies rules are limited to estimate the variation of the structural performance of the main deck caused by the operation of offshore cranes under different hydrodynamic conditions. Here, we present a methodology to determine the alteration of the structural behavior of a main deck of FPSO vessel due to different operation conditions of a board offshore crane. This methodology considers the hydrodynamic response for two ultimate limit states: operating and storm conditions from 1000 m water depth in Gulf of Mexico with a return period of 10 and 100 years, respectively. The methodology includes finite element method (FEM) models of the main deck supporting an offshore crane to predict its structural response. The maximum von Mises stress of the main deck does not overcome its maximum permissible stress, which allows a safe operation of the FPSO crane. The proposed methodology can be used to estimate the structural behavior of main decks of FPSO vessels that are modified for supporting offshore cranes, regarding the hydrodynamic response for each FPSO under the operation and extreme conditions in its location. Thus, naval designers could select the better structural modifications of the main decks that decrease their costs of construction and maintenance.

Heave and horizontal displacement and anti-sway control of payload during ship-to-ship load transfer with an offshore crane on very rough sea conditions

Ship-to-ship load transfer with offshore cranes is challenging in rough sea conditions because of the difficulty in compensating for the increased position-velocity-acceleration errors and the restriction of the unloading area.This study proposes an efficient solution by integrating the combined vertical, horizontal, and anti-swing control system, experimentally validated mathematical hydraulic system and ship motions on irregular waves, the dynamic model of the crane, and an innovative control strategy. Particle Swarm Optimization-Proportional-Integrative-Derivate (PSO-PID) Trajectory Route Control System ensures safe unloading by advancing in the desired vertical position and speed route. The operation's horizontal positioning is realized even for very rough sea conditions with the support of the PID-controlled main and elbow boom. An extra added telescopic boom is used for anti-swing control with Particle Swarm Optimization Proportional-Derivative-Second Derivative (PSO-PDD2) control system.Simulations with different sea conditions were made and analyzed to verify the study's system model's effectiveness. The simulation results revealed that the system model is a valid and successful solution.

Heave reduction of payload through crane control based on deep reinforcement learning using dual offshore cranes

AbstractOffshore operation causes the dynamic motion of offshore cranes and payload by the ocean environment. The motion of the payload lowers the safety and efficiency of the work, which may increase the working time or cause accidents. Therefore, we design a control method for the crane using artificial intelligence to minimize the heave motion of the payload. Herein, reinforcement learning (RL), which calculates actions according to states, is applied. Furthermore, the deep deterministic policy gradient (DDPG) algorithm is used because the actions need to be determined in a continuous state. In the DDPG algorithm, the state is defined as the motion of the crane and speed of the wire rope, and the action is defined as the speed of the wire rope. In addition, the reward is calculated using the motion of the payload. In this study, the heave motion of the payload was reduced by developing an agent suitable for adjusting the length of the wire rope. The heave motion of the payload was compared in between the non-learning condition of the RL-based control and proportional integral differential (PID) control; and an average payload reduction rate of 30% was observed under RL-based control. The RL-based control performed better than the PID control under learned conditions.

A nonlinear optimal control approach for underactuated offshore cranes

ABSTRACT The article proposes a nonlinear optimal control approach for the model of boom cranes being mounted on vessels. The dynamic model of the boom cranes undergoes approximate linearisation with the use of Taylor series expansion around a temporary operating point which is recomputed at each iteration of the control method. For the approximately linearised model, an H-infinity feedback controller is designed. The linearisation procedure relies on the computation of the Jacobian matrices of the state-space model of the system. For the computation of the controller's feedback gains, an algebraic Riccati equation is solved at each time step of the control method. The new nonlinear optimal control approach achieves fast and accurate tracking for all state variables of the boom cranes, under moderate variations of the control inputs. The stability properties of the control scheme are proven through Lyapunov analysis.

Simulation Research on Ship-borne PMSM Speed Regulation Control System Based on Fuzzy PID Control

As the important actuator of ship-borne electromechanical equipment such as offshore cranes, the control system of Permanent-magnet synchronous motor (PMSM) is a complex system that features nonlinearity, time-varying parameters, and multi-variable coupling. Due to working in a swing environment, the ship-borne PMSM speed regulation control system is confronted with some problems, such as abrupt load change, external interference signals, motor parameters change, and given signals change frequently. To improve the control performance, this study designs the 2-dimensional Fuzzy PID controller and builds the control system simulation model with a double closed-loop structure in the MATLAB/Simulink. By comparing the control system under various simulation situations, the simulation findings demonstrate that the control system using the Fuzzy PID controller far outperforms the PID controller in terms of control indicators such as stability, tracking ability, and anti-disturbance ability, which can better adapt to working in swing environment.