Active Heave Compensation Research Articles

Research on Heave Compensation System Based on Switched Reluctance Motor

Aiming at the requirements of the marine work platform for real-time control, time-varying speed and the time-varying torque control of the motor-driven active heave compensation device, this paper introduces a composite control strategy based on the switched reluctance motor (SRM)-driven active heave compensation device. As for the compensation error caused by the time lag in the real-time system, the model prediction trajectory algorithm is used to predict the compensation displacement obtained using the dynamic model. The next time, the control parameters are then provided for the SRM control system in advance to reduce the compensation error. The SRM control strategy selects a double closed-loop compound control strategy of Back Propagation (BP) fuzzy neural network Proportion Integration Differentiation (PID) control. Its outer speed loop uses a fuzzy controller to quickly track a wide range of speed changes. The torque inner loop uses BP neural network adaptive PID control. This helps to reduce torque ripple and to ensure that the electromagnetic torque output of the SRM remains stable. Finally, the system feasibility is verified by setting different wave parameters. The simulation results show that the simulation conditions can reach 97.5% and 96.4% under the 3 and 4 wave levels, respectively. The simulation effect is satisfying, which verifies the feasibility of the proposed scheme.

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.

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.

Research on Three-Closed-Loop ADRC Position Compensation Strategy Based on Winch-Type Heave Compensation System with a Secondary Component

To mitigate the interference of waves on an offshore operation ship, heave compensation systems find widespread application. The performance of heave compensation systems significantly influences the efficiency and safety of maritime operations. This study established a mathematical model for a winch-based active heave compensation system. It introduced a three-loop active disturbance rejection control (ADRC) strategy that encompasses piston position control, winch speed control, and load-displacement control to enable the real-time estimation and compensation of system disturbances, thereby enhancing the performance of the heave compensation system. To assess the effectiveness of this control strategy, this study employed Matlab/Simulink and AMESim to construct a co-simulation model and conducted a comparative analysis with traditional proportional integral derivative (PID) control systems. The research findings indicate that the three-loop ADRC position control strategy consistently delivered superior compensation performance across various operational scenarios.

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.

Cascade Control of Active Heave Compensation Nonlinear System for Marine Crane

During the rough marine environment, heave compensation is used to offset the heave motion of the vessel when a marine crane lifts and lands the load. Thus, load motion and vessel motion are realized decoupled. In previous studies, the interference items such as hydraulic cylinder friction, underwater drag force and nonlinear friction in the active heave compensation system of a marine hydraulic crane are compensated as a concentrated interference force to be estimated. In this paper, we disassembled the interference items; the disturbance observer and adaptive rate are designed to estimate unmodeled disturbance force and system uncertain parameters, respectively; and we designed an active heave compensator with the adaptive nonlinear cascade controller which has the disturbance observer (DOB-ANCC). For the heave compensation of load displacement, this paper derived the control law of the nonlinear system model based on the backstepping method. The outer loop control is displacement control and the inner loop control is pressure control. The simulation verifies the effectiveness of the control strategy proposed in this paper and the availability of heave displacement compensation for a marine crane hoisting load. The compensation efficiency of the designed controller (DOB-ANCC) for the heave motion of the load can reach more than 95%, and the maximum displacement tracking error of the controller can reach ± 0.035 m.

A Prediction Method of Ship Motion Based on LSTM Neural Network with Variable Step-Variable Sampling Frequency Characteristics

In active heave compensation, in order to realize the smooth control of the heave compensation platform, it is necessary to use the ship motion measurement system to accurately obtain the ship displacement signal, invert the ship displacement signal, and then control the expansion and contraction of the electric cylinder so that the compensation platform remains horizontal. The ship displacement measurement system generally adopts the second integral of the acceleration sensor to obtain the ship displacement signal. During the acquisition process of the ship displacement signal, the quadratic integration process of the acceleration, and the communication process of the output control command, there is a processing lag which makes the error accumulate, resulting in a delay in the measurement of the ship motion. In order to collect the ship motion more accurately and control the heave compensation platform more precisely, this paper proposes a ship motion prediction method based on a variable step-variable sampling frequency characteristic LSTM (Long Short-Term Memory) neural network. First, we use the autocorrelation function algorithm to calculate the inherent delay of the lag in the process of signal acquisition by the measurement system. Secondly, the LSTM neural network is used to predict the inherent delay step of the lagging ship displacement signal. During the prediction process, it is found that the difference in the sampling frequency of the displacement signal will lead to a change in the step of the inherent delay—experiment in the laboratory to verify. By controlling the motion platform to simulate the motion of the ship and using the ship motion measurement system and the laser sensor system to measure the displacement signal of the motion platform synchronously, it is verified that the ship motion measurement system does have an inherent delay. Thirdly, on a sailing ship, ship displacement signals are collected by setting multiple sets of ship motion measurement systems. Finally, multiple sets of sampling frequency and multiple steps are set, and the ship motion is predicted based on the variable step-variable sampling frequency LSTM neural network. It is verified that the prediction accuracy is related to the sampling frequency of the signal collector and the prediction step of the LSTM neural network, which improves the prediction accuracy of the model and the timeliness of ship motion acquisition.

Predictive Control of a Heaving Compensation System Based on Machine Learning Prediction Algorithm

Floating structures have become a major part of offshore structure communities as offshore engineering moves from shallow waters to deeper ones. Floating installation ships or platforms are widely used in these engineering operations. Unexpected wave-induced motions affect floating structures, especially in harsh sea conditions. Horizontal motions on the sea surface can be offset by a dynamic positioning system, and heave motions can be controlled by a heave compensation system. Active heave compensation (AHC) systems are applied to control vertical heave motions and improve safety and efficiency. Predictive control based on machine learning prediction algorithms further improves the performance of active heave compensation control systems. This study proposes a predictive control strategy for an active heave compensation system with a machine learning prediction algorithm to minimise the heave motion of crane payload. A predictive active compensation model is presented to verify the proposed predictive control strategy, and proportion–integration–differentiation control with predictive control is adopted. The reliability of back propagation neural network (BPNN) and long short-term memory recurrent neural network (LSTM RNN) prediction algorithms is proven. The influence of the predictive error on compensation performance is analysed by comparing predictive feedforward cases with actual-data feedforward cases. Predictive feedforward control with regular and irregular wave conditions is discussed, and the possible strategies are examined. After implementing the proposed predictive control strategy based on a machine learning algorithm in an active heave compensation system, the heave motion of the payload is reduced considerably. This investigation is expected to contribute to the motion control strategy of floating structures.

Experimental Research on Integrated Disassembly Equipment of Super Large Offshore Oilfield Facilities

Based on the key module-lifting arm system, based on the principle of similarity and the hydrodynamic experimental method of a multi-dimension vibration test platform, an experimental platform for dismantling equipment is designed and built. Subsequently, the motion control model of the six-degrees-of-freedom platform is established. The three-ring control model of a servo electric cylinder is established, and the active heave compensation control of a servo electric cylinder is realized by combining position control theory. Based on the co-simulation of ADAMS and Simulink, the co-simulation system of the integrated dismantling equipment experimental platform is designed and built, and the simulation system is tested and verified. Finally, simulation and experimental verification are carried out based on the experimental platform and co-simulation system. The results show that the heave compensation rate reaches 58.3% in third-class sea conditions, 61.2% in fourth-class sea conditions, and 62.4% in fifth-class sea conditions. The integrated dismantling scheme of super large offshore oilfield facilities is feasible but, in order to ensure the safety and reliability of the operation, a heave compensation system needs to be added. The error between the simulation results and the experimental results is about 15%. Based on the analysis of external interference factors in the experiment, the error results are within a reasonable range, which proves that the experimental platform, the co-simulation system of the experimental platform, and the heave compensation strategy are accurate and effective. This study, for the first time in China, provides an effective experimental platform and co-simulation platform for the design and optimization of the integrated dismantling equipment of super large offshore oilfield facilities and lays a good research foundation for the construction and engineering demonstration of subsequent equipment.

Operability analysis of control system for ROV launch-and-recovery from autonomous surface vessel

The launch and recovery of equipment such as remotely operated vehicles (ROVs) is a critical task that defines the operability limits of many marine operations. This paper considers the analysis of control systems that are designed to maximize the operability limits for launch and recovery of a ROV from a small unmanned surface vessel (USV). We use numerical simulation for the analysis, where the method combines recent approaches for wave compensating dynamic positioning, active heave compensation, and positioning control of the ROV with multi-body dynamic simulation of the surface vessel and ROV, including hydrodynamic forces and dynamic interactions from wires that depend on the ROV depth and moonpool. The results show that the choice of control algorithms and their tuning parameters has a significant effect on the system’s operability, and should be carefully designed and tuned to optimize the operability limits for any given sea state, weather and operational setup. The results show that numerical analysis with a system’s simulation is an effective tool to verify operability and its sensitivity to various parameters for the given ROV recovery application.

Modeling and Adaptive Boundary Robust Control of Active Heave Compensation Systems

Heave compensation systems are essential for operations’ safety, reliability, and efficiency in harsh offshore environments. This paper investigates the vibration suppression problem of a type of deep-sea robot with the length of time variation and harsh operating environments for active heave compensation systems, where hydraulic heave compensators implement actuators with input nonlinearity, model coupling, and unknown nonlinear disturbances. A robust adaptive output feedback control scheme based on the backstepping control method is designed to eliminate deep-ocean robot vibration, where the adaptive law handles the system parameter uncertainty. Meanwhile, a nonlinear disturbance observer (NDO) is introduced to overcome the effects of random disturbances and model coupling. In addition, the stability of the whole system is proved according to Lyapunov’s theory, and the scheme is shown to be feasible by theoretical analysis. Finally, a comparative simulation study was conducted to validate the effectiveness of the proposed controller.

Dynamic Analysis of Active Heave Compensation System for Marine Winch under the Impact of Irregular Waves

The six-degree-of-freedom (6 DOF) motion of the mother ship, especially the heave motion, brings difficulties to offshore operations and even causes safety accidents. To ensure the reliability of the launch and recovery system when the active heave compensation (AHC) function works, its dynamic characteristics are analyzed. Firstly, the dynamic model of the launch and recovery system with a rigid rope is constructed, and the mathematical simulation of the launch and recovery system without the AHC function under the excitation of irregular waves is completed. Secondly, a flexible rope based on the finite element method is established, and the dynamic responses of the launch and recovery system with AHC function under different conditions are compared with those without AHC function. The simulation results demonstrate that the dynamic responses of the system are related to the load, the underwater penetration, and the sea condition. In detail, the increase of the load leads to an increase in the dynamic response of the system. In essence, the underwater penetration affects the dynamic response of the system by affecting the activity of load acceleration. Therefore, a short rope is preferred in the maritime operations. Moreover, the harsh sea condition usually causes an undesirable effect of AHC function. In summary, the overall work is conductive to the modeling of the launch and recovery system, as well as the development of AHC technology so as to improve the quality of offshore operations in the future.

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.

Modeling and simulation analysis of active heave compensation control system for electric-driven marine winch under excitation of irregular waves

The six-degree-of-freedom (6 DOF) motion of the mother-ship, which is caused by wave fluctuation, makes offshore operations difficult. To solve this problem, various heave compensation systems were proposed, as well as the law of wave motion. These heave compensation systems included passive heave compensation system, semi-active heave compensation system, and active heave compensation (AHC) system. However, the empirical formula of wave motion is not suitable for practical offshore operations, and rare AHC systems take the characteristic of compensation into consideration. To study the compensation characteristic of the AHC system based on electric-driven marine winch in the actual sea condition and improve the accuracy of compensation, this work uses the measured data of wave motion, and deduces the motion equations of multi-axial driving system. By substituting the above elements into the AHC system and designing the sliding mode controller (SMC), the simulation results show the ideal compensation effect of the system. By comparing with experimental results, it is concluded that the driving system operates in according with the specified states, and the compensation performance of system is effective. The overall work is conductive to the research on AHC system, as well as the exploitation of marine resources.

Reliability and Risk Analysis of an Active Heave Compensation Drawworks

Reliability and Risk Analysis of an Active Heave Compensation Drawworks

Study on a novel two-part underwater towed system for near-surface towed vehicle test

A new underwater two-part towed system is proposed and studied for the test of near-surface towed vehicles. The near-surface towed vehicle is towed by submarines or the large displacement unmanned undersea vehicle, and plays the role of the communication relay with the onshore station. To deal with the influence of the harsh wave environment and create a stable test platform, a fuzzy-PID control method and an active heave compensation device are applied in the towed system. The mathematical model of the two-part towed system is built. In the model, the nonlinear aspects are considered, such as the interaction of the multi-body, the flexibility of the cable, the wave force, the heave compensation. Based on the model, the simulation results indicate that the Fuzzy-PID control method can significantly reduce the depth fluctuation of the towed vehicle under different sea state. Besides, it is also demonstrated that the active heave compensation device can obviously improve the stability performance of the two-part towed system by greatly reducing the depth fluctuation of the ballast, and create a very stable test environment similar to the submarine or large underwater vehicle.

Adaptive Control Based on Neural Network and Beetle Antennae Search Algorithm for an Active Heave Compensation System

Adaptive Control Based on Neural Network and Beetle Antennae Search Algorithm for an Active Heave Compensation System

Modeling of Active Heave Compensation System for Seafloor Drill

Aiming at the influences of wave in the process of launch & recovery of the seafloor drill, a velocity sensor is used to gather the data of the heave motion of ship, and a mathematical model of active heave compensation hydraulic serve control system for seafloor drill is established. The simulation of this model based on PID control is performed. The results show that the heave motion compensation control of seafloor drill using PID control makes the tracking accuracy more than 90%. This will improves the reliability and security of the seafloor drill in the process of launch and recovery.

Hierarchical NMPC–ISMC of active heave motion compensation system for TMS–ROV recovery

This study reveals the operating risk of cable breaking when the TMS–ROV recovery is carried out beneath rough ocean waves. To release the negative impact of the support vessels vertical heave motion on the station-keeping and position tracking performance of TMS, a robust hierarchical control scheme for a hydraulic-driven winch-based active heave compensation (AHC) system is proposed based on the combination of a nonlinear model predictive control (NMPC) strategy, an integral sliding mode control (ISMC) scheme and a vessel heave motion prediction algorithm. The motivation of utilizing the ISMC-based internal level combined with the integral state transformation technique is given by the robust capability to eliminate the uncertainties, which provides the nominal model for NMPC-based external level to guarantee the optimal evolution satisfying the state and input constraints and resisting the dynamical hysteresis caused by the employed extremely long cable length for deep-sea operation. Comparative simulation studies contribute to the analysis of the surge in cable tension during the TMS–ROV recovery and demonstrate the superior tracking and heave compensation performance, strong robustness and constraint satisfaction of the proposal.

A comparative study of different active heave compensation approaches

Heave compensation is a vital part of various marine and offshore operations. It is used in various applications, including the transfer of cargo between two vessels in the open ocean, installation of topsides of an offshore structure, offshore drilling and for surveillance, reconnaissance and monitoring. These applications typically involve a load suspended from a hydraulically powered winch that is connected to a vessel that is undergoing dynamic motion in the ocean environment. The goal in these applications is to design a winch controller to keep the load at a regulated height by rejecting the net heave motion of the winch arising from ship motions at sea. In this study, we analyze and compare the performance of various control algorithms in stabilizing a suspended load while the vessel is subjected to changing sea conditions. The KCS container ship is chosen as the vessel undergoing dynamic motion in the ocean. The negative of the net heave motion at the winch is provided as a reference signal to track. Various control strategies like Proportional-Derivative (PD) Control, Model Predictive Control (MPC), Linear Quadratic Integral Control (LQI), and Sliding Mode Control (SMC) are implemented and tuned for effective heave compensation. The performance of the controllers is compared with respect to heave compensation, disturbance rejection and noise attenuation.