Offshore Crane Research Articles

Position Control of Heave Compensation for Offshore Cranes Based on a Particle Swarm Optimized Model Predictive Trajectory Path Controller

The wave compensation system can be very useful in several naval applications. It can greatly reduce the relative irregular motion between the two ships when replenishment operations are performed, or between the ship and the offshore platform, which is caused by the waves. It is widely used in offshore operations, offshore cargo transfer, oil and gas exploitation, deep-sea mining, the hoisting and recovery of submersibles, etc. However, when a crane is used in a ship or moving platform, due to the influence of the hull, the crane load movement is similar to a space ball pendulum, which causes the heave displacement to show significant nonlinear motion characteristics. Moreover, the time delay of the detection mechanism and control error could result in untimely compensation, which deteriorates the performance. Consequently, this paper proposes one advanced prediction compensation method, namely Particle Swarm Optimized Model Predictive Trajectory Path controller (PSO−MPTP), which can improve the heave compensation performance. This method, which is based on Model Predictive Control (MPC), is firstly applied to the position servo system and takes into account the heave prediction and control effects simultaneously. The heave displacement of the crane load could be predicted in multiple steps in advance and used as the input of the position loop of the compensation machine. The achieved simulations show that the proposed controller has better prediction ability, higher control accuracy, and stronger robustness.

Dynamic Analysis of Splash-zone Crossing Operation for a Subsea Template

Subsea templates are steel structures used to support subsea well components. Normally, offshore crane vessels are employed to install them to the target location on the seabed. Crossing the splash-zone during the lowering of a subsea template is considered the most critical phase during the installation due to slamming loads and needs to be studied to provide the operational weather criterion during the planning phase. In this study, dynamic response analysis has been carried out to evaluate the allowable sea states for the plash-zone crossing phase of the subsea templates. The numerical model of the lifting system, including the crane vessel and the subsea template, is firstly built in the state-of-the-art numerical program SIMA-SIMO. Then, dynamic analysis with time-domain simulations is carried out for the lifting system under various sea states. The disturbed wave field due to the shielding effects from the installation vessel is considered when calculating the hydrodynamic forces on the template. Statistical modelling of the dynamic responses from different wave realizations is used to estimate the extreme responses of various sea states. The application of the generalized extreme value distribution and Gumbel distribution in fitting the extreme responses is discussed. Moreover, the influence of the shielding effects from the vessel, as well as the influence of the changing size of the suction anchor on the hydrodynamic responses and the allowable sea states are studied.

An adaptive tracking control method for offshore cranes with unknown gravity parameters

The offshore crane system is a typical underactuated system which is installed on the ship and carried out the payload transportation in the offshore environment. The payload transportation for offshore cranes is extremely sensitive to the influence of the ship motion. High couplings also exist between the offshore crane state variables. These factors may lead to large payload swing, and the offshore crane control problem is very difficult. In addition, since some physical parameters of the offshore crane system are difficult to be measured, there usually exist parameter uncertainties, which may lead to positioning errors. In order to tackle the above problems, a new adaptive tracking control method for offshore crane system is proposed, which brings satisfactory tracking performance of the reference trajectories and realizes the control objectives of the payload accurate and fast transportation, the payload swing elimination, and the accurate gravity compensation. Unlike the traditional adaptive control method, an elaborately designed adaptive estimation update law is proposed, which is used to ensure the accurate online estimation for gravity-related parameters. By using Lyapunov stability theory, it is proved that the proposed adaptive tracking controller is effective. Simulations are included to further show the performance of the proposed method.

A time optimal trajectory planning method for offshore cranes with ship roll motions

With the fast development of the economy, marine activities are increasing. Due to the advantages of offshore cranes, they are widely used in marine production as effective transportation tools. As a matter of fact, the offshore crane works on the ship known as a typical noninnertial system, which is affected by the ship movement. To tackle this problem, we propose a time optimal trajectory planning method for the considered offshore crane. Specifically, to tackle the couplings between state variables, we show that the offshore crane system is differentially flat with the payload coordinates as the flat outputs. Based on this fact, the planning problems for the jib motion and the rope length are further converted into the planning problems for flat outputs. Then, in order to ensure the trackability of the planned trajectory and improve the safety, we consider a series of physical constraints including the jib luffing motion velocity and acceleration constraints, the rope length varying velocity and acceleration constraints, and the payload swing angle and angular velocity constraints, and then a time optimization problem is further formulated. By utilizing a bisection-based method, the optimal payload transportation time is obtained as well as the corresponding time optimal trajectories. As far as we know, it is the first time optimal trajectory planning method designed for offshore cranes to achieve the fast and accurate payload transportation as well as the payload swing elimination in earth-fixed frame. At last, the effectiveness of the proposed method is verified by simulation tests.

Online trajectory planning for three-dimensional offshore boom cranes

Efficient control of offshore cranes has attracted world-wide attention in recent years. However, due to the persistent ship roll/heave motion disturbances, it is very challenging to guarantee the transient performance for offshore cranes. To solve this problem, this paper proposes an online trajectory planning method for three-dimensional offshore cranes. Specifically, preliminary trajectories are first designed for different crane motions (e.g., boom luffing rotating, rope hoisting motions), following which the cargoes can be delivered to designated sites. After that, some online adjustment terms are integrated with the pre-defined trajectories, which serve to attenuate or eliminate the undesired cargo swing introduced by both the improper crane operations and the ship motion disturbances. Different from traditional off-line planning methods, the proposed method retains satisfactory robustness (in the sense of swing elimination) due to the extra incorporated terms. The proposed control concept can be extended to trajectory planning of similar underactuated systems.

Adaptive Neural Network-Based Tracking Control of Underactuated Offshore Ship-to-Ship Crane Systems Subject to Unknown Wave Motions Disturbances

As a typical underactuated mechanical system, offshore ship-mounted cranes are widely used to carry out the tasks of transferring cargos from one ship to another in the marine environment. Different from land-fixed cranes as well as traditional harbor cranes, offshore ship-to-ship crane systems work in two noninertial (ship) frames, while the target locations of the cargos are also inevitably influenced by the movements of the target ship. Besides, various external disturbances, which are caused by persistent sea waves, sea winds, or currents, etc., bring much more challenges to the control task of offshore ship-to-ship crane systems. To properly address these practical problems, in this article, we propose an increased adaptive neural network (NN)-based anti-swing tracking control strategy for such coordinated offshore crane systems, with a ship-motion prediction algorithm suggested to generate the target trajectories for cargos, and an adaptive NN proposed to deal with complicated unknown wave-induced disturbances. Bounded tracking performance is also guaranteed through a complete Lyapunov-based stability analysis. To the best of our knowledge, without any simplification of the original nonlinear dynamics, this article provides a high-performance adaptive control approach to deal with the anti-interference tracking control problem for offshore ship-to-ship crane systems, which are subjected to trajectories uncertainties as well as unknown wave motions disturbances. Furthermore, comparative hardware experimental results are presented to demonstrate the efficiency of the proposed control method.

Observer-based adaptive fuzzy control of underactuated offshore cranes for cargo stabilization with respect to ship decks

Offshore crane systems are widely employed to transport cargoes on vessels due to their outstanding flexibility. However, they always suffer from various disturbances in the special working environment, which will appear in not only the actuated part (jib and cable) but also the unactuated part (cargo). In particular, some platform parameters cannot be measured precisely. Additionally, the task scenarios of offshore cranes are divided into stabilizing cargoes with respect to the ground and the ship deck, respectively, i.e., in the earth-fixed (inertia) and ship-fixed (non-inertia) coordinate frame. However, existing methods focus on the former. To address the above problems, a nonlinear observer-based adaptive fuzzy controller is suggested to stabilize the cargo with respect to the ship deck, and the swing can be simultaneously suppressed. The closed-loop stability is theoretically guaranteed by Lyapunov methods. To our best knowledge, this is the first control scheme that can stabilize the cargo with respect to the ship deck for underactuated offshore cranes with uncertainties, input dead zones, and external disturbances. Finally, we employ some experiments to validate the effectiveness of the proposed control approach.

Nonlinear partially saturated control of a double pendulum offshore crane based on fractional-order disturbance observer

The stabilizing control of a double pendulum offshore crane in the presence of matched disturbances, unmatched disturbances and the actuator saturations is a challenging problem. To solve this problem, an anti-swing partially saturated control method is proposed. Specially, a Fractional-Order Disturbance Observer (FODO) is designed to compensate for the matched disturbances and a feedback stabilizing controller is proposed to regulate the hook and cargo to desired positions and suppress swings. Afterwards the closed-loop asymptotical stability is strictly proven. Extensive simulation results are given to demonstrate that the proposed controller could suppress the swing effectively without exceeding the actuator saturations and has strong robustness to various disturbances.

Experimental Study and Numerical Analysis of Crane Operability in Floating Crane Catamaran

Crane vessel is a floating structure equipped with accommodation facilities and one or more cranes to do work in the field. Crane vessel continue to be developed so that they can lift large structures and operate safely in certain environmental conditions. The work that is usually done by crane vessel is to lift heavy or light loads from land to ship, from ship to land, from ship to sea, from sea to ship, and from ship to ship. The process of moving loads carried out by a crane vessel usually called the lifting process. In carrying out its work, a crane vessel is limited by certain criteria for safety reasons. One of them is the criterion that limits the heave motion at the end of the crane boom and roll and pitch motion of the crane vessel. In this final project, an experimental study and numerical analysis of crane operability were carried out on catamaran hulled crane vessel. Experiments were carried out at the Balai Teknologi Hidrodinamika BPPT and numerical analysis using the MOSES software. According to the criteria used, namely Operational Limitations of Offshore Crane Vessels, cranes on floating crane catamaran have the highest operability when the vessel heading is 0 o to the direction of the incoming waves, which is up to H s 1.45 m.

Experimental investigation of offshore crane load during installation of a wind turbine jacket substructure in regular waves

Installation of offshore structures for harvesting energy or oil and gas industries is still burdensome because of the rough sea state. Unless a calm water condition prevailing, installing any substructure or floating structure at offshore sites is very difficult. Hence, there has been great potential for research to investigate offshore structures’ installation for normal and more energetic wave conditions. To understand and develop the methodology for the installation, the hydrodynamic response of the structure and impact received by the offshore crane is vital. In this context, the present study focuses on installing a heavy concrete jacket foundation sub-structure (Equivalent steel jacket) of an offshore wind energy structure. Due to the heavyweight and the temporary buoyancy tanks, the structure’s response during installation is different from the tubular steel structures predominantly used for jacket structures. In this work, the structure’s response in regular waves at different positions of upending is analysed. Also, the peak force received by the crane at different sea states is measured for different positions of upending. Finally, the forces to be expected while upending the jacket in waves is quantified, and a suitable weather window is suggested. Furthermore, the critical positions in upending are established.

Intelligent material distribution and optimization in the assembly process of large offshore crane lifting equipment

The constraint of the material distribution for offshore crane lifting equipment is complicated. Taking into account the characteristics of the material distribution problem of the general assembly of offshore lifting equipment, this paper proposes a scheduling method based on the improved Particle Swarm Optimization algorithm by considering vehicle material matching relationships. Firstly, this we establish a vehicle scheduling model for the final assembly logistics distribution process and then propose a two-stage hierarchical solution framework for minimizing the number of vehicles and the transportation distance. Secondly, the optimization aims to minimize the number of vehicles, we obtain the optimal solution by CPLEX Optimizer. The vehicle transportation distance is then optimized by the improved particle swarm optimization algorithm. The initial solution performance of the algorithm is improved by our heuristic rules. The discretization of the problem is achieved by coding, decoding and location updating methods according to the characteristics of the problem. Additionally, the updating mechanism of simulated annealing algorithm is introduced to update the location to avoid the algorithm falling into local optimum. Through case analysis and comparisons, the improved Particle Swarm Optimization based scheduling method proposed in this paper combined with the vehicle-material matching relationship can effectively improve the efficiency of the material distribution with better performance.

Offshore crane non-linear stochastic response: novel design and extreme response by a path integration

ABSTRACT In this paper, the novel pendulum tuned mass damper model has been suggested as a potential practical engineering modification to an existing offshore crane setup. A number of potential numerical singularities have been circumvented and substantial numerical model accuracy has been reached. Main application of this study would be extreme value statistics, in case of e.g. extreme weather conditions causing collision between vessel and payload. Next, extreme statistics of random vibrations has been studied in this paper for a suggested pendulum tuned mass damper model under white noise excitation. Restoring force has been modelled as the elastic non-linear, and numerical comparison has been performed with the linearised restoring force model case to see the force non-linearity effect on the vessel payload response statistics. The statistics of non-linear case has been studied by applying the path integration method, based on the Markov property of the coupled dynamic system.

Anti-sway control of offshore crane on surface vessel using global sliding mode control

ABSTRACT In this paper, the global sliding mode control technique is designed for anti-sway control of offshore crane mounted on surface vessel. The offshore cranes are responsible for moving containers from mega container ships to a smaller vessel. In this regard, after introducing the dynamics of the crane mounted on the surface vessel, the sliding surfaces and control laws are designed to maintain the stability of the system against external disturbances such as sea waves and wind induced movements. Furthermore, using the Lyapunov’s stability analysis, it is proven that the position/ velocity errors are converged to the origin. Finally, to determine the effectiveness of the proposed method, the simulation results of the global sliding mode control technique are compared to those of the continuous integral sliding mode control and proportional–integral–derivative approaches. The development of this procedure due to its high productivity and economic feasibility can be used as a new tool in the modern maritime industry.

Lumped, Constrained Cable Modeling With Explicit State-Space Formulation Using An Elastic Version of Baumgarte Stabilization

Abstract This paper presents a modeling approach for efficient simulation of slender structures, such as wires, cables and ropes. Lumped structural elements are connected using constraints. These are solved explicitly, using an elastic version of Baumgarte stabilization. This avoids singularities in the matrix inversions. The resulting explicit state-space formulation filters the higher order dynamics and can be solved using simple numerical integration methods. Constraints are demonstrated for modeling different aspects: Internal cable forces, one cable sliding along another cable and contact between cable and seabed. Also, a cable initialization routine is presented for rapid building of different interconnected cable geometries, ranging from cases in offshore crane operations to in-sea equipment such as seismic cables. Two case studies are presented to illustrate the effectiveness and the robustness of the proposed modeling approach; the first one being a test of two connected, sinking cables, and the last one being a larger case demonstrating the use of the cable library in an offshore seismic survey case.

A Robust Payload Control System Design for Offshore Cranes: Experimental Study

This paper presents a robust controller design of payload position control for an offshore crane facing disturbance and parametric uncertainties. The offshore operations with cranes while lifting and lowering a payload can be dangerous since safety and efficiency are affected by waves, wind and ocean currents. Such harsh sea conditions put the offshore crane and payload through unwanted disturbances and parametric uncertainties, which requires a robust control system to guarantee reliable performance of these systems. In this paper, we detail a controller designed based on uniformly ultimately bounded (UUB) theory, combined with the input-output linearization control technique (IOLC). The stability of the closed-loop system under the UUB conditions is analyzed using the energy-based Lyapunov function. To evaluate the control performance of the proposed controller, along with an IOLC and an integral sliding mode controller (ISMC), a comparison study is also conducted. The control performance and efficiency of the proposed controller are validated through experiments on an offshore crane model.

An Output Feedback Approach for Regulation of 5-DOF Offshore Cranes With Ship Yaw and Roll Perturbations

In practice, offshore cranes are effective transportation tools used on ships. Different from land-fixed cranes, offshore cranes work in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">noninertial</i> frame, which are usually affected by different disturbances. Therefore, the control problem of offshore cranes is much more <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">difficult</i> . Till now, only few control methods have been proposed for offshore cranes, which are usually designed for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">planar</i> offshore cranes, while the more practical three-dimensional (3-D) movements are <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ignored</i> . Considering these facts, in this article, we focus on the control problem of a 5 degrees of freedom (DOF) offshore crane in 3-D space with persistent ship yaw and roll perturbations and propose an effective <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">output feedback</i> control method. Specifically, we first present an elaborate coordinate transformation method to deal with ship perturbations. Then an energy-like function is constructed based on the transformed model, and then by designing some auxiliary signals, an output feedback method is designed with rigorous mathematical analysis to prove the closed-loop asymptotic stability results. As far as we know, the proposed method is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> control method designed for 5-DOF offshore cranes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any linearization, which <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">only</i> uses output signals. Finally, experimental results are included to verify the performance of the proposed method.

UUB 이론을 이용한 해상작업용 크레인의 부하위치제어계 설계

This paper introduces a payload position control system for an offshore crane to cope with uncertainties. On the sea, marine systems are exposed to various disturbances and uncertainties provoked by the vessel motion, hydrodynamic forces, etc. These factors deteriorate the safety and efficiency of work operations. To overcome these problems, we propose a novel control system design method based on UUB (Uniformly Ultimately Bounded) theory combined with the input-output linearization method. To guarantee the given state error bound by uniformly ultimately boundedness, the analysis of stability condition using the energy-based Lyapunov function is conducted. Then, the particle swarm optimization technique is used to obtain the optimal control gains of the control system. Finally, the control performance and effectiveness of the proposed control system are validated through a set of simulation tests.

Regenerative scheduling problem in engineer to order manufacturing: an economic assessment

The dynamic production scheduling is a very complex process that may arise from the occurrence of unpredictable situations such as the arrival of new orders besides the ones already accepted. As a consequence, companies may often encounter several difficulties to make decisions about the new orders acceptance and sequencing along with the production of the existing ones. With this recognition, a mathematical programming model for the regenerative scheduling problem with deterministic processing times is formulated in the present paper to evaluate the economic advantage of accepting a new order in an engineer to order (ETO) manufacturing organization. The real case of an Italian ETO company which produces hydraulic marine and offshore cranes is afterwards presented.

Modeling and Analysis of Offshore Crane Retrofitted With Cable-Driven Inverted Tetrahedron Mechanism

Crane operations might be very dangerous in rough sea conditions due to unexpected payload swing induced by ship excitations. In this paper, a novel Cable-Driven Inverted Tetrahedron Mechanism (CDITM) is presented to suppress the payload swing for sake of the workers' safety. The CDITM retrofitting on an offshore crane is simplified as a constrained pendulum with a moving base, and its equations of motion are obtained by Newton Euler Method. Next, three-dimensional dynamic analysis is performed using Matlab/Simulink, and the influence law of ship excitations, tagline tension, crane pose and CDITM configuration on the payload swing are investigated. Finally, through comparative experimental verification, it is found that the simulation tendencies of in-plane swing follows the experiment curves quite well, and the variations between the simulation and experiment results are acceptable. Thus the dynamic modeling and analysis of CDITM are verified. The theoretical and experimental results are fundamental and valuable for the engineering application of CDITM in the offshore industries.

Performance Improvement of a Hydraulic Active/Passive Heave Compensation Winch Using Semi Secondary Motor Control: Experimental and Numerical Verification

In this paper, a newly developed controller for active heave compensated offshore cranes is compared with state-of-the-art control methods. The comparison is divided into a numerical part on stability margins as well as operational windows and an experimental validation of the expected performance improvement based on a full-scale testing on site with a crane rated to 250 metric tons. Such a crane represents the typical target for the new control method using a combination of active and passive hydraulic actuation on the main winch. The active hydraulic actuation is a hydrostatic transmission with variable-displacement pumps and variable-displacement motors. The new controller employs feedforward control of the motors’ displacement so that the window of operation is increased and, simultaneously, oscillations in the system are markedly reduced.