深水钻井立管反冲控制算法研究

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

This article investigates the finite‐time recoil control problem of deepwater drilling riser systems with nonlinear friction force, tension force and saturation input. For the friction force, a new approximation model based on radial basis function neural networks is presented, which not only can ensure a better approximation effect than the sine‐function type and exponential‐polynomial‐function type computational models, but also can be easily used for control design. Different from the existing linear optimal control methods, a neural‐network‐based adaptive backstepping control method is proposed to deal with the nonlinear friction and tension forces, which can achieve better recoil control responses. An auxiliary system combining with the change of coordinates is employed to compensate the saturation input effect. To prolong the average release interval of control input while preserving satisfied control performance, a new switched event‐triggered control (ETC) scheme is developed, in which the triggering conditions are switched between the fixed and relative thresholds based on the strength of control signal. With the event‐triggered controller, the practical finite‐time stability condition of recoil control system is derived and the Zeno behavior is avoided. Numerical results are given to show the advantages of the proposed methods in handling the model nonlinearities, finite‐time stability and ETC performance of riser‐tension systems.

No abstract available

No abstract available

No abstract available

No abstract available

This paper considers the delayed recoil control problem of deepwater riser systems by a non-small delay approach. A velocity feedback controller with interval-like time-varying input delay is proposed to attain the suppression effect of the frictional disturbance on recoil responses. The main difference from the existing results lies in two aspects: a delayed static output feedback controller is designed with partially measurable velocity information, and a non-small delay method instead of small delay method is attempted for solving the control problem. Some interval-delay-dependent criteria of $H_{\infty}$ performance analysis and control design are derived. Simulation results are given to verify the effectiveness and advantages of the delayed recoil control method.

This paper deals with the recoil suppression problem of a deepwater drilling riser system via active H∞ control using both current and delayed states. First, based on the three degrees of freedom spring-mass-damping model of the riser system, an incremental dynamic equation of the system subject to the platform heave motion and the friction force induced by drilling discharge mud and seawater is established. Then, to reject recoil movements of the riser, a delayed state feedback H∞ controller with delayed states as well as current states is designed. The existence conditions and the design method of the delayed H∞ recoil controllers are presented. Third, the effects of the introduced time-delays on the recoil control of the riser are analyzed, and the design of optimal artificial time-delays is formulated as the minimum value problem of a series of quintic algebraic polynomials, which are related to the weights of average response amplitudes, steady-state errors, and the control force. Lastly, simulation results are provided to demonstrate the effectiveness of delay-free and delayed H∞ recoil control schemes for the riser. It is shown that (i) under the delayed H∞ controllers, the recoil responses of the riser can be controlled significantly; (ii) the decay rate of the recoil response under the delay-free H∞ controller is slightly faster than the one under the delayed H∞ controllers. However, the former requires more control cost than the latter; (iii) compared with the delayed H∞ controller with the existing linear quadratic optimal controller, the control cost by the former is larger than that by the latter. However, the steady-state errors of the riser under the latter are slightly smaller than that under the former; (iv) the introduced time-delays with proper size play positive role of suppressing recoil response of the system, and the corresponding delayed H∞ controller series provide more options for recoil control of the riser.

No abstract available

No abstract available

This paper investigates the recoil control of the deepwater drilling riser system with nonlinear tension force and energy-bounded friction force under the circumstances of limited network resources and unreliable communication. Different from the existing linearization modeling method, a triangle-based polytope modeling method is applied to the nonlinear riser system. Based on the polytope model, to improve resource utilization and accommodate random data loss and communication delay, an asynchronous gain-scheduled control strategy under a hybrid event-triggered scheme is proposed. An asynchronous linear parameter-varying system that blends input delay and impulsive update equation is presented to model the nonlinear networked recoil control system, where the asynchronous deviation bounds of scheduling parameters are calculated. Resorting to the Lyapunov–Krasovskii functional method, some solvable conditions of disturbance attenuation analysis and recoil control design are derived such that the resulting networked system is exponentially mean-square stable with prescribed H _∞ performance. The obtained numerical results verified that the proposed nonlinear networked control method can achieve a better recoil response of the riser system with less transmission data compared with the linear control method. 针对受非线性张紧力和能量有界摩擦力影响的深水钻井隔水系统, 本文研究了其在网络资源有限和不可靠通信情况下的反冲控制问题. 不同于现有的线性化建模方法, 本文将基于三角形的多面体建模方法应用于非线性隔水管系统. 基于该多面体模型, 为提高资源利用率并容许随机数据丢失和通信时延的发生, 提出混合事件触发方案下一种异步增益调度控制策略. 将非线性网络化反冲控制系统建模为带有输入时延和和脉冲更新方程的异步线性参变系统, 并给出调度参数的异步偏差界计算方法. 运用Lyapunov–Krasovskii泛函方法, 提出干扰抑制分析和反冲控制器设计的一些可解条件. 这些条件可以保证最终的网络化系统指数均方稳定且具有指定的 H _∞性能. 数值分析结果证实, 在使用较少通信数据的情况下, 相比线性控制, 所提非线性网络化控制能获得更好的反冲响应.

How to effectively control the recoil response after an emergency disconnection is one of the core technical problems in ensuring the safe and reliable operation of a deepwater drilling riser. Currently, the theoretical analysis is based on a discretization model or numerical simulation, which ignores the continuity of the riser system and the coupling effects of load acting on the riser. To address this problem further, in this paper, we establish a mechanical model and control equation with infinite degree of freedom for riser recoil response, where the heave motion of the floating drilling platform, seawater damping, and the viscous resistance of drilling fluid discharge were taken into account. In addition, the correctness of the model and solving approach are verified against the Orcaflex software. On this basis, the influence of wave period, wave height, initial phase angle, and tension coefficient on the recoil characteristics are discussed. The success of riser emergency disconnection is related to the clearance between the lower marine riser package (LMRP) and the blowout preventer (BOP) and the axial force distribution of the riser. The influence of the above-mentioned factors on the riser recoil response is also complicated. On the basis of the assumptions put forward and the model established, some quantitative conclusions are drawn. This study is of reference significance for safety control of riser emergency disconnection operation.

No abstract available

No abstract available

This article uses the deepwater drilling riser equipped on a specific ocean drilling vessel as an example to establish a dynamic analysis model of the riser, and analyzes the lateral deformation characteristics of the riser under different working conditions and examines the impact of various factors on the lateral displacement of the riser. Research shows that under normal connection modes, maximum deformation occurs at the upper-middle section of the riser. Under suspended evacuation modes, the lateral deformation of the riser exhibits a trend of initially increasing and then decreasing. Ocean current velocity is one of the primary influencing factors on the lateral vibration characteristics of the riser.

No abstract available

No abstract available

No abstract available

This paper presents an adaptive boundary control design for flexible riser systems with external disturbances and boundary position constraint. An integral barrier Lyapunov function (iBLF) is used to solve the boundary position constraint problem. Since the iBLF directly constrains the boundary position, this relaxes the conservative restriction on the state constraint of conventional BLF control. A new auxiliary signal is designed to offset the effect of the coupling term that cannot be eliminated. Compared to time triggering, the controller and actuator communicate less when using event triggering. Therefore, an event-triggered control scheme is designed to achieve effective suppression of riser vibration by introducing a relative threshold strategy. The Lyapunov stability theory is used to demonstrate that the flexible riser system is finally constrained. The efficiency of the control strategy is then further verified by numerical simulations. Note to Practitioners—This paper investigates the control problem of flexible riser systems with external disturbances. Since the riser needs to consider the uninterrupted marine distribution disturbance and external disturbance, the riser will inevitably distort and vibrate. So the stability of the ship is extremely challenging. The riser is regarded as an Euler-Bernoulli beam construction because of its small diameter and lengthy length. Using Hamilton’s principle, the riser is represented as a fourth-order partial differential equation and two ordinary differential equations. In contrast to the logarithmic BLF and tangent BLF, the integral BLF has direct constraints on the boundary positions, which relaxes the conservative restrictions on state constraints imposed by conventional BLF control. Event-triggered control has attracted the interest of many flexible system control researchers due to its benefits in preserving communication, cost and other resources, and is widely used in practical engineering fields. The complexity and uncertainty attributed to the PDE system itself makes the design of event-triggered strategies more difficult. Based on the original ODE event triggering, it discusses the PDE-based event-triggered strategy of flexible riser systems.

This paper investigates the dynamic event-triggered boundary control of cyber-physical flexible riser systems under spoofing attacks. It aims to dampen vibrations resulting from riser pipe deformation, alleviate the communication load, and curtail the influence of such attacks. Firstly, a novel dynamic event-triggered boundary controller is constructed by utilizing external disturbances and event-triggering strategies. This controller overcomes the complex spatio-temporal coupling phenomena in riser systems and suppresses vibrations. Secondly, a controller is developed to minimize the impact of false data injection on the cyber-physical flexible riser system due to uncertain spoofing attacks. Finally, the stability of the system is mathematically analyzed to prevent the occurrence of Zeno phenomena. The simulation results further validate the effectiveness of the proposed method. Note to Practitioners—Cyber-physical flexible risers play an important role in various marine engineering and industrial fields, such as underwater oil and gas extraction, deep-sea resource exploitation, and seabed exploration. A challenge within these domains is the effective mitigation of cyber-physical riser vibrations amidst spoofing attacks, a problem that has yet to be resolved. This paper introduces a novel dynamic event-triggered boundary control strategy aimed at dampening vibrations induced by riser deformations, reducing communication overhead, and attenuating the effects of spoofing attacks. Based on PDEs, the proposed control strategy offers a solution for the regulation of flexible riser systems in forthcoming engineering endeavors.

No abstract available

With the burgeoning growth of the maritime economy, marine risers have emerged as reliable and convenient conduits for the transport of oil and natural gas. However, these risers are vulnerable to vibrational disturbances, which can adversely impact system performance and induce fatigue damage. Therefore, effective vibration control strategies are required to address this issue. This study introduces an innovative adaptive quantized fault-tolerant control strategy designed to attenuate vibrations in a three-dimensional (3-D) riser-vessel system against the effects of actuator faults, unknown control direction, and external disturbances. Different from previous findings, the suggested controller can directly counteract the nonlinear component stemming from actuator faults and handle the nonlinear decomposition inherent to the quantizer, without the necessity for upper-limit estimation. Furthermore, to tackle the input saturation, control laws are formulated using the hyperbolic tangent operator. Finally, the proposed controller’s effectiveness and robustness are validated through thorough Lyapunov analysis and numerical simulations, affirming the system’s uniformly bounded stability.

A novel adaptive constraint control approach is proposed for flexible riser systems characterized by uncertain parameters and external disturbances, aimed at achieving the desired transient performance. By combining Hamilton’s principle with partial differential equations (PDEs), the physical model is transformed into a dynamic model. Considering the boundary position constraint, a boundary controller is built using the tangent barrier Lyapunov function (BLF) to mitigate vibrations. In order to ensure the convergence of the boundary position error at a predetermined rate, the control approach incorporates a performance function to attain the necessary transient performance. An auxiliary term is defined to counteract the impact of coupling terms that remain during the decoupling process of PDEs. Finally, the above scheme is further validated through MATLAB simulations.

The operational environment for deep-sea oil and gas extraction is characterized by its complexity and dynamic nature, rendering it susceptible to emergencies such as typhoons and tsunamis, which can precipitate significant safety incidents. This paper addresses the critical need for rapid disconnection of subsea pipelines and safe evacuation of floating platforms during such contingencies. We innovatively propose a fast-response deep-water testing positioning column electro-hydraulic system, complemented by a fuzzy PID control. A comprehensive joint simulation model is constructed to rigorously analyze the stability of the positioning column’s electro-hydraulic control system. Through a series of terrestrial experiments incorporating diverse test signals, we further validate the dynamic performance stability and anti-interference capabilities of the electro-hydraulic control system. Our findings indicate that the designed riser control module electro-hydraulic system ensures the stable operation of the positioning column during oil and gas extraction processes. Specifically, during step signal tracking, the fuzzy PID control achieves a peak time of 8.3 s, a regulation time of 8.8 s, and an overshoot of 7%. For sinusoidal signal tracking, the amplitude ratio of the fuzzy PID control’s tracking curve is 1.01, with an overshoot of 1%, and the control system error is consistently maintained within ±1 mm. These results underscore the superior dynamic performance of the proposed fuzzy PID control strategy. This research not only provides a robust theoretical foundation and empirical data for the development of riser control module electro-hydraulic systems in deep-water testing but also delineates future research directions in this critical domain.

No abstract available

For the flexible riser systems modeled with partial differential equations (PDEs), this article explores the boundary control problem in depth for the first time using a dynamic event-triggered mechanism (DETM). Given the intrinsic time-space coupling characteristic inherent in PDE computations, implementing a state-dependent DETM for PDE-based flexible risers presents a significant challenge. To overcome this difficulty, a novel dynamic event-triggered control method is introduced for flexible riser systems, focusing on optimizing available control inputs. In order to save computational costs from the controller to the actuator, a dynamic event-triggered adaptive boundary controller is designed to effectively reduce boundary position vibrations. Additionally, considering external disturbances, an adaptive bounded compensation term is incorporated to counteract the influence of external disturbances on the system. Addressing boundary position constraints, a new integral barrier Lyapunov function (iBLF) tailored specifically for flexible riser systems is introduced, thereby alleviating conservatism in the controller design of flexible risers modeled by PDEs. At last, the validity of the proposed method is demonstrated through a simulation example.

In this paper, vibration control of a flexible marine riser with uncertain parameters subjected to distributed disturbance and boundary disturbance is studied. The existing vibration control algorithms have the problems of relying on the accurate mathematical model of the system, complex control laws, and need to measure multiple states of the system, which cannot effectively deal with the uncertainty of model parameters and external disturbances. To effectively suppress the vibration of a marine flexible riser system with uncertain parameters, an adaptive fuzzy backstepping control algorithm was designed. First, the backstepping method and Lyapunov function are used to analyze the subsystem and design the virtual control law. On this basis, an adaptive fuzzy system was designed. The fuzzy system was used to approach the unknown nonlinear term in the design process of the control law and the uniform boundedness of the system was proved by the Lyapunov stability theory. The designed control algorithm has a simple structure, and it can effectively restrain the riser vibration and improve the control rate. Finally, the numerical simulation results show that the designed control algorithm is effective in suppressing the vibration of flexible risers and the control effect is better than previous PID control and robust adaptive control.

No abstract available

This paper develops an adaptive fault-tolerant boundary control scheme for riser-vessel systems to deal with actuator failure and structural failure, simultaneously. The marine riser-vessel system dynamics is modeled by a fourth-order partial-ordinary differential equation. An adaptive fault-tolerant boundary control framework is proposed, which together with the designed adaptive update law guarantees the uniformly ultimately boundedness of the closed-loop system. The simulation results show that the developed fault-tolerant control method can still make the system state converge in a small area of zero in the presence of actuator failure and structural failure.

In this article, we propose a new adaptive fuzzy fault-tolerant control (FTC) for a three-dimensional riser-vessel system with unknown backlash nonlinearity. A model for the smooth inverse dynamics of the backlash is introduced; then, the control input is divided into an expected input and a compensation error. Considering the imprecision of system modeling and unknown external disturbances, we employ a fuzzy adaptive technology to achieve compensation. By incorporating the actuator fault term and backlash error, the adaptive FTC is developed to resolve loss faults in the actuator and compensate for the unknown backlash to some extent. The direct Lyapunov method is used to demonstrate the system’s bounded stability. Finally, simulation results demonstrate the effectiveness of the derived scheme.

In this paper, an adaptive neural network controller is proposed for vibration suppression of a multisectional riser system with unknown boundary disturbance, time‐varying asymmetric output constraint, and input nonlinearity. The considered riser system is composed of a continuous connection of several different pipes, and its dynamic models are represented by a set of multiple continuously connected partial differential equations (PDEs) and an ordinary differential equation (ODE) at the top boundary. Considering input nonlinearity, external disturbance, and system uncertainty, radial basis function (RBF) neural networks are adopted to eliminate the effect of these uncertain terms. Besides, a barrier Lyapunov function is employed to guarantee the restrictions. With the proposed boundary control, the stability of the closed‐loop system is proved and simulations are given to illustrate the well performance of the proposed control strategy.

 When flexible risers in the ocean are subjected to various environmental loads in the ocean, vibration will inevitably occur. Due to the nonlinearity and uncertainty of the actual riser system, it is impossible to obtain an accurate mathematical model of the riser system. The existing control algorithms designed based on the precise model of the riser system cannot meet the actual control requirements. A flexible riser boundary control method based on fuzzy control algorithm is proposed to suppress the vibration of marine flexible riser systems with uncertain models. Firstly, the dynamic models of existing marine flexible risers were studied. In response to the uncertainty of the riser system model, the control experience was transformed into an automatic control strategy in the form of fuzzy language control rules to improve the adaptability of the controller. Then, combining boundary control technology with fuzzy control, a boundary controller is constructed to stabilize the riser in a small neighborhood of its original position and reduce fatigue damage to the riser. Finally, the effectiveness of the designed fuzzy boundary control algorithm was verified through MATLAB simulation results, and the vibration suppression effect of the algorithm on the vertical tube was better than that of traditional PD control.

In this paper, a boundary control with barrier term is proposed for a typical three-dimensional flexible riser system by integrating backstepping technique with barrier Lyapunov functions. The proposed boundary control does not depend on the exact value of interference and can effectively restrain the vibration of the riser and constrain the angle between the riser and the platform. The proposed control has a small amount of calculation and strong robustness, and can effectively restrain the riser vibration when the environmental disturbance changes. In addition, based on the proposed boundary control method, the stability of the closed loop system in space and time is proved by Lyapunov stability theorem when the initial conditions are satisfied. Numerical simulation shows the effectiveness and superiority of the controller.

Recently, with the development of the marine economy, marine risers have garnered increasing attention as they present facile and reliable methods for oil and gas transportation. However, these risers are susceptible to vibrations, which can lead to system performance degradation and fatigue damage. Therefore, effective vibration control strategies are required to address this issue. In this study, a novel adaptive fault-tolerant control (FTC) strategy is adopted to suppress the vibrations of a 3-D riser-vessel system against the effects of actuator failures, backlash-like hysteresis, and external disturbances. A barrier-based Lyapunov function is merged to eliminate the time-varying output constraints of the system. Adaptive FTC laws with projection mapping operators are designed to compensate for parameter uncertainties and consider input nonlinearities to improve system robustness. Finally, a rigorous Lyapunov analysis and numerical simulations are performed to verify the validity of the proposed controller and guarantee uniformly bounded stability of the system.

For tackling the vibration suppression problem for a flexible riser system with external disturbance, input saturation, and output constraint, this article is constructed. A boundary iterative learning control is constructed together with Lyapunov’s theory and backstepping technology. The output constraint is largely solved by employing a barrier Lyapunov function. External disturbance is handled as the iteration goes on. Under the control of the designed method, the output is limited to a given region, and the system is proved to be closed-loop stable with the assistance of Lyapunov’s theorem of stability. Ultimately, the result of the simulation indicates that the method is effective and has a good control effect.

In this paper, a class of flexible riser systems modeled by partial differential equations (PDEs) with the backlash is considered. The backlash is formulated as the addition of a linear input and a interference-like term, then an new auxiliary item is introduced to compensate for the impact of this backlash. In addition, the constraint problem for the position and the velocity is also taken into consideration. To solve this constrain problem, the logarithmic barrier Lyapunov function is employed. For the flexible riser system, two kinds of adaptive controllers are proposed under the following two cases. One controller is designed when only the parameter of backlash is unknown. On the basis of this result, the other controller is presented when some system parameters cannot be measured through actual measurement. Then, combing the theory of Lyapunov stability, the two controllers can guarantee the boundedness of all signals in the closed-loop flexible riser system. Further, both the position and the velocity satisfy their corresponding constraint condition. Finally, the simulation example verifies that the proposed control method is effective.

In this article, vibration abatement problems of a riser system with system uncertainty, input deadzone, and output constraint are considered. For obtaining better control precision, a boundary control law is constructed by employing the backstepping method and Lyapunov’s theory. The output constraint is guaranteed by utilizing a barrier Lyapunov function. Adaptive neural networks are designed to cope with the uncertainty of the riser and compensate for the effect caused by the asymmetric deadzone nonlinearity. With the designed controller, the output constraint is satisfied, and the system stability is guaranteed through Lyapunov synthesis. In the end, numerical simulation results are provided to display the performance of the developed adaptive neural network boundary control law.

In this study, an adaptive robust control technique for an uncertain riser-vessel system in a three-dimensional space is developed. A projection mapping technique and a hyperbolic tangent function are exploited to construct novel adaptive robust controllers based on adaptive laws dynamically updated online to restrain the vibration, tackle parametric uncertainties, compensate for the unknown upper bound of disturbances, and ensure robustness of the coupled system. Lyapunov’s method is adopted to analyze and demonstrate the bounded stability of the closed-loop system. Simulation results are provided to validate the feasibility and effectiveness of the proposed approach.

This article addresses the problem for vibration suppression of a multiple-sectioned marine riser system subject to time-varying external disturbances and asymmetric output constraint. Under the assumption that continuity constraint, multiple-sectioned marine riser’s dynamics are described by some continuously connected partial differential equations (PDEs) coupled with an ordinary differential equation (ODE). We only employ boundary control mechanism that suppresses system’s vibration displacements and compensate the influence of external disturbances. A novel and improved disturbance observer is proposed to estimate unknown boundary disturbance and two different barrier Lyapunov functions are constructed to prevent the time-varying constraint violation. Based on the backstepping technology and Lyapunov-based control, a boundary controller is presented to accomplish the control objectives. Moreover, the uniform boundedness and stability of the closed-loop system are rigorously guaranteed. Finally, simulation results are provided to illustrate the effectiveness of the designed control scheme.

To suppress the vibration of a flexible riser system with input saturation and uncertain parameters under the influence of unknown external disturbances, an adaptive fuzzy backstepping boundary control algorithm was designed. First, the backstepping method and Lyapunov function are used to analyze the subsystem and design the virtual control law. On this basis, the adaptive fuzzy system was designed to approximate the unknown nonlinear term in the design process, and the smooth hyperbolic tangent function and the auxiliary system based on Nussbaum function were introduced to limit control input. The stability and uniform boundedness of the closed-loop control system are proved by the Lyapunov stability theory without simplifying or discretizing the infinite dimensional dynamic model. Finally, the effectiveness of the proposed control algorithm is verified by comparing the control effect with proportional–integral–derivative control and the previous adaptive backstepping control by MATLAB simulation. The simulation results show that the proposed control algorithm can overcome the uncertainty of system parameters and effectively suppress the riser vibration under input constraints, and its control effect is better than proportional–integral–derivative control and adaptive backstepping control.

In this study, we develop an adaptive neural network based boundary control method for a flexible marine riser system with unknown nonlinear disturbances and output constraints to suppress vibrations. We begin with describing the dynamic behavior of the riser system using a distributed parameter system with partial differential equations. To compensate for the effect of nonlinear disturbances, we construct a neural network based boundary controller using a radial basis neural network to reduce vibrations. Under the proposed boundary controller, the state of the riser is guaranteed to be uniformly bounded based on the Lyapunov method. The proposed methodology provides a way to integrate neural networks into boundary control for other flexible robotic manipulator systems. Finally, numerical simulations are given to demonstrate the effectiveness of the proposed control method.

In this paper, we aim to reduce the vibration of an asymmetric output constraint multiple-sectioned marine riser system having external time-varying disturbances. The riser system’s dynamics can be described by a number of successively connected partial differential equations (PDEs) and an ordinary differential equation (ODE) additional with assuming continuity constraints condition. We build a novel disturbance observer to evaluate boundary disturbance that are unknown and meanwhile barrier Lyapunov functions are employed to guard against the violation of time-varying constraint. Stem from Lyapunov-based control coped with the back-stepping technology, a boundary controller is put forward to realize the control objectives. In addition, the closed-loop system’s stability and uniform boundedness are strictly guaranteed. In the end, simulations verifies the validity of the designed control scheme.

Addressing safety challenges of drilling riser systems caused by platform drift in deepwater operations, this paper establishes a multi-body coupled dynamic model of deepwater dry tree cylindrical platform-drilling riser-subsea wellhead system considering combined wind, wave, and current effects based on three-dimensional potential flow theory combined with frequency-domain and time-domain computational methods. Taking the KP18-1 oilfield dry tree cylindrical platform in the South China Sea as the research object, platform motion response characteristics and drilling riser system dynamic behavior were systematically analyzed. Through quasi-static analysis, the nonlinear influence of platform drift on riser bending deformation was revealed: at 10% water depth offset, maximum stress reaches 855.1 MPa exceeding safe limits, with peak bending moment occurring at 6% offset before decreasing due to local buckling instability causing load path reconstruction. Dynamic analysis shows that platform natural periods (23-29.64 s) are well separated from wave periods (3-13 s), with horizontal motion dominated by low-frequency slow drift (period >80s) while heave response corresponds to platform natural period (12-18s). High stress regions shift from the telescopic joint under normal operating conditions (1-10 year return period) to the tapered stress joint under extreme conditions (100-1000 year return period). A collaborative configuration method for tensioner stroke (12.5 m, 3000 kN, recommended 45 ft) and telescopic joint stroke (8.1 m calculated, full extension 22 m) was proposed with quantitative design guidelines. Fatigue assessment based on VIV-parametric excitation coupled vibration model and Palmgren-Miner cumulative damage theory identifies critical hotspots at BOP connection (8.3 years), telescopic joint (10.5 years), and tensioner pup joint (11.8 years), with annual damage rate of 0.08-0.12 and predicted system life of approximately 20 years. The research results provide theoretical basis and engineering guidance for parameter matching optimization and fatigue life management of tensioner-expansion joint systems in deepwater drilling operations.

No abstract available

No abstract available

No abstract available

No abstract available

For deepwater jack-up wellhead platforms, a tensioner-based design scheme for tensioning the riser pipe is proposed. Based on the displacement and stress response of the riser pipe, three riser pipe sizes and corresponding tension forces were selected. Furthermore, a coupled analysis model was established between the tensioned riser pipe and the jack-up platform. Under a 550-ton tension force, the impact of three riser pipe models on the overall performance of the deepwater mobile wellhead platform was analyzed. The results indicate that the tensioned riser pipe can reduce the first two natural frequencies of the platform and mitigate the dynamic amplification effect of wave loads. As the riser pipe diameter increases, the proportion of wave loads on the riser pipe body relative to the total platform load rises, along with the load transmitted to the platform hull. While providing stiffness to the platform, the tensioned riser pipe adversely affects horizontal displacement and leg strength, with the impact becoming more pronounced as the riser pipe diameter increases. In summary, the 914×40mm tensioned riser pipe design demonstrates potential feasibility, but further optimization is required for riser strength at the mud surface, overall platform stiffness, and leg chord strength.

No abstract available

No abstract available

This article investigates the boundary stabilization of a flexible marine riser system that takes rotational inertia into account. This system is described using a nonlinear partial differential equation under the nonlinear controls. Specifically, we focus on applying nonlinear boundary feedback control forces and torques at the top end of the riser. Utilizing measurements of boundary velocity and angular velocity, we devise nonlinear feedback mechanisms aimed at mitigating vibrations within the flexible marine riser system. Our approach encompasses a broad range of nonlinear feedback scenarios. To establish the well-posedness of the resulting closed-loop system, we employ the nonlinear semigroup method. Furthermore, we leverage the integral multiplier technique to demonstrate that the stability characteristics of the closed-loop system are dictated by a dissipative ordinary differential equation. As the nonlinear feedback functions exhibit distinct growth patterns in proximity to the origin, we identify three primary types of decay behaviors. These are subsequently estimated through solutions of the ordinary differential equation and validated through numerical simulations.

No abstract available

No abstract available

We study the problem of stabilization to zero stationary state of nonlinear fourth‐order wave equation with nonlinear damping term modelling dynamics of marine riser by feedback control terms that employ finitely many Fourier modes. Additionally, we demonstrate that the corresponding equation with linear damping, which represents the dynamics of pipes conveying fluids, can be exponentially stabilized by a feedback controller employing a finite number of Fourier modes.

No abstract available

No abstract available

No abstract available

No abstract available

The aim of this paper is to develop a boundary control for the vibration reduction of a flexible marine riser system in the presence of parametric uncertainties and system states obtained inaccurately. To this end, an adaptive output feedback boundary control is proposed to suppress the riser's vibration fusing with observer-based backstepping, high-gain observers and robust adaptive control theory. In addition, the parameter adaptive laws are designed to compensate for the system parametric uncertainties, and the disturbance observer is introduced to mitigate the effects of external environmental disturbance. The uniformly bounded stability of the closed-loop system is achieved through rigorous Lyapunov analysis without any discretisation or simplification of the dynamics in the time and space, and the state observer error is ensured to exponentially converge to zero as time grows to infinity. In the end, the simulation and comparison studies are carried out to illustrate the performance of the proposed control under the proper choice of the design parameters.

No abstract available

No abstract available

ABSTRACT In this work, we study a viscoelastic flexible marine riser problem with vessel dynamics subject to a distributed disturbance. The dynamic of the problem is modelled as a viscoelastic Euler–Bernoulli beam structure. Based on the multiplier method and some ideas introduced by N.-E. Tatar (J. Contemp. Math. Anal., 48(6):285–296, 2013), we shall suppress the riser's vibration in a certain manner that we will determine. In fact, we prove uniform stability of the system for a large class of relaxation functions. Moreover, the relationship between the behaviour of the relaxation function and the decay rate of the energy is established. This improves earlier work where a control on the top of the structure has been imposed and the ocean disturbance was ignored.

No abstract available

No abstract available

No abstract available

This paper discusses an instability phenomenon sometimes observed on drillships when latching or unlatching a long riser to the well head while the drawworks is operating in the active heave compensation (AHC) mode. The paper starts with presenting field data clearly showing an incident of instability. Next, it focuses on the physical causes or conditions for instabilities to occur. The root cause is identified to be an inherent and poorly dampened bending mode of the entire drillship. This mode has a natural frequency equal to the vibration frequency observed during the instability event. Two additional causes are also discussed in some details: the complex dynamics of the riser and the dynamics of the drawworks and its control system when run in the AHC mode. The dynamics of all 3 systems are coupled to give an analytic formula for the decay rate of the ship vibration mode. This formula is used for predicting the conditions when the decay rate is negative, and instability can occur. The paper also includes results from an advanced simulation model. The results from this model confirm the predictions from the analytic analysis. Finally, various proposals for solving the instability problem are briefly discussed.

No abstract available