Ride Control System Research Articles

Reducing wave impacts on high-speed catamarans through deployment of ride control: Analysis of full-scale measurements

Full-scale trials on a 98 m wave piercer catamaran were conducted in the North Sea and North Atlantic region. In order to examine, amongst other things, the effectiveness of the ride control system, the ship was deliberately operated in sea conditions likely to induce a large number of wave impact events. Primary ship motion and structural response parameters, such as angles, rates and accelerations, and strains at various locations were recorded. Slam and minor wave impact events were identified in the data records and analysed to determine the influence of wave headings, vessel speeds, sea states and ride control system activation on their occurrence rates and severity. The Empirical Mode Decomposition technique was used to remove both noise and the rigid body response from the acceleration signals. This was based on prior work by the authors and found to provide more reliable slam identification than traditional methods. A prediction of extreme slam occurrences was modelled using logistic regression. A key outcome of the study was the finding that the activation of ride control significantly reduces the probability of extreme slams occurring.

A novel CFD approach for the prediction of ride control system response on wave-piercing catamaran in calm water

Ride Control Systems (RCS) on high-speed vessels help improve passenger comfort and mitigate dynamic structural loads. Incat Tasmania Wave-Piercing Catamarans (WPC) use RCS consisting of a central T-foil, and a stern tab on each deli-hull. Previous towing tank studies on a 2.5 m model of a 112 m WPC have demonstrated significant reductions in motions with the use of a T-foil and stern tabs. To extend this work, this study examines the use of Computational Fluid Dynamics (CFD) to predict the ship's response with RCS implemented. The model-scale WPC was simulated in calm water conditions, traveling at 2.89 m/s (Fr∼0.6), with step responses applied at the T-foil and stern tabs, to determine the trim and sinkage. The T-foil was implemented in CFD using two methods: 1) Overset mesh; 2) Forcing function. By replacing the geometric mesh with a lift force coefficient and forcing function, the setup difficulty and computational cost were reduced. Only about 7% difference was observed between CFD and experiments, but no significant difference was found between the methods of overset mesh and forcing function. This has proven the ability of CFD to predict vessel responses to RCS step changes in calm water, and the simplified forcing function method is recommended.

An active oscillation reduction method for off-highway front loaders

Cabin vibration in construction machines is a known issue affecting both comfort and safety of the operators, and it also induces losses in machine productivity. The solution offered in commercial machines, known as the passive ride control, has the drawbacks of limited performance on a wide range of operating conditions and component costs, which has motivated research toward “active” alternatives that utilize electro-hydraulic systems without additional components. Nonetheless, the nonlinearities and the dynamic response of these systems constraint the performance of such alternatives, when compared to the commercial solution and therefore, their diffusion on the market. To address the challenges mentioned above, this article proposes an alternative hydraulic system layout to perform the ride control function based on connecting the boom lift actuators of the front-end loader in differential mode. This article describes the development of two active control strategies for this new ride control system that utilizes pressure and acceleration information to suppress cabin oscillations and presents the experimental tests on a full-size wheel loader. The results show a similar capability for reducing the oscillations achieved by the commercial solution and the one proposed in this research. In certain scenarios, the proposed formulation offers up to 10% of further improvement in terms of cabin oscillation reduction.

Influence of an active T-foil on motions and passenger comfort of a wave-piercing catamaran based on sea trials in oblique seas

In this paper the influence of a Ride-Control System (RCS) on the Response Amplitude Operator (RAO) of a full-scale high-speed catamaran was investigated using sea trials data. A T-foil and stern tabs were installed on a Wave-Piercing Catamaran (Incat Tasmania Hull 061) to improve ship motions and passenger comfort. More than 40 total effective hours of sea trials were conducted by the US Navy in 2004, encountering sea states 4–5 in the Atlantic Ocean near the United Kingdom. The reduction in Motion Sickness Incidence (MSI) was estimated in order to examine the effectiveness of the RCS in improving passenger comfort. By comparing the case of active RCS (T-foil plus stern tabs) with the case of active stern tabs only, it was found that the T-foil plays a vital role in the passenger comfort enhancement. Based on ISO recommended MSI calculation of a 2-h seaway, the percentage reduction in MSI was estimated, and hence the effectiveness of the T-foil deployment, along with the influence of speeds, headings, location on board and encountered wave height were analysed. A notable improvement in passenger comfort was observed in the real world bow quartering sea by deploying the RCS. An MSI reduction of 21% in high speeds (30–35 knots, [Formula: see text] 0.6) was observed, which was almost twice the MSI reduction (11%) in low speeds (15–20 knots, [Formula: see text] 0.3). However, in terms of MSI percentage reduction, the ability of T-foil in vessel motion control in oblique seas was found to be limited compared to the results in head seas.

FULL-SCALE MOTIONS OF A LARGE HIGH-SPEED CATAMARAN: THE INFLUENCE OF WAVE ENVIRONMENT, SPEED AND RIDE CONTROL SYSTEM

To assess the behaviour of large high-speed catamarans in severe seas, extensive full-scale trials were conducted by the U.S. Navy on an INCAT Tasmania built vessel in the North Sea and North Atlantic region. Systematic testing was done for different speeds, sea states and ride control settings at different headings. Collected data has been used to characterise the ship’s motions and seakeeping performance with respect to wave environment, vessel speed and ride control system. Motion response amplitude operators were derived and compared with results from a two-dimensional Green function time-domain strip theory seakeeping prediction method. An increase of motion response with increasing vessel speed and a decrease with the vessel moving from head to beam seas was found. In higher sea states and headings ahead of beam seas an increasing influence of the centre bow on pitch motion damping was found. Significant motion RAO reduction was also found when the ride control system was active. Its effectiveness increased at higher speeds and contributed to heave and pitch motion RAO reduction. Predicted motion magnitudes with the time domain seakeeping code were consistent with the measured motion responses, but maximum heave was predicted at a rather higher frequency than was evident in the trials.

RESPONSE OF A HIGH-SPEED WAVE-PIERCING CATAMARAN TO AN ACTIVE RIDE CONTROL SYSTEM

Ride control systems on high-seed vessels are an important design features for improving passenger comfort and reducing motion sickness and dynamic structural loads. To investigate the performance of ride control systems a 2.5m catamaran model based on the 112m INCAT catamaran was tested with an active centre bow mounted T-Foil and two active stern mounted trim tabs. The model was set-up for towing tank tests in calm water to measure the motions response to ride control step inputs. Heave and pitch response were measured when the model was excited by deflections of the T-Foil and the stern tab separately. Appropriate combinations of the control surface deflections were then determined to produce pure heave and pure pitch response. This forms the basis for setting the gains of the ride control system to implement different control algorithms in terms of the heave and pitch motions in encountered waves. A two degree of freedom rigid body analysis was undertaken to theoretically evaluate the experimental results and showed close agreement with the tank test responses. This work gives an insight into the motions control response and forms the basis for future investigations of optimal control algorithms.

LOW REYNOLDS NUMBER PERFORMANCE OF A MODEL SCALE T-FOIL

Submerged T-foils are an essential forward component of the ride control systems of high speed ferries. A model scale T-Foil for a 2.5m towing tank model of a 112m INCAT Tasmania high-speed wave-piercer catamaran has been tested for both static and dynamic lift performance. The tests were carried out using a closed-circuit water tunnel to investigate the lift and drag characteristics as well as frequency response of the T-Foil. The model T-Foil operates at a Reynolds number of approximately 105, has an aspect ratio of 3.6 and a planform which is strongly tapered from the inboard to outboard end. All of these factors, as well as strut and pivot interference, influence the steady lift curve slope ( of the model T-foil which was found to be 61% of the value for an ideal aerofoil with elliptic loading. The T-foil dynamic performance was limited primarily by the stepper motor drive system and connection linkage. At the frequency of maximum motion of the 2.5 m catamaran model (about 1.5Hz) the model T-foil has approximately 5% reduction of amplitude and 15 degrees of phase shift relative to the low frequency response. Only very small limitations arose due to the unsteady lift as predicted by the analysis of Theodorsen. It was concluded that the model scale T-foil performed adequately for application to simulation of a ride control system at model scale.

H2/H∞ Antivertical Controller Based on Particle Swarm Optimization (PSO) Using Active T-Foils and Trim Tabs for a Fast Catamaran

A wave-piercing catamaran (WPC) is a high-performance ship that has been developed in recent years. Compared to other common ships, the WPC has higher lateral stability, larger deck area, lower oil consumption, and higher speed. However, under rough seas and at high speeds, the coupled heave/pitch motions of the WPC can easily produce coupled oscillations that seriously affect its seaworthiness. To solve these problems, a ride control system was designed for the WPC in this study. This system comprises two T-foils, two trim tabs, and a catamaran motion controller. The H2/H∞ controller was designed based on memory-based particle swarm optimization to alleviate the coupled oscillation resulting from heave/pitch motions. Numerical simulations were conducted to validate the proposed method, and the results showed that the proposed motion controller could obviously improve the sea-keeping performance of a WPC.

Design of H∞ anti-vertical controller and optimal allocation rule for catamaran T-foil and trim tab

This paper proposes an H∞ robust control scheme for a wave-piercing catamaran (WPC) ride control system (RCS) in rough water. The control signal is assigned to the T-foils and trim tabs by an improved genetic algorithm. To reduce the vertical oscillation of a WPC in wave turbulence at high speeds, based on the uncertain parameters model of the coupled heave/pitch motion of a catamaran with an RCS, an H∞ robust controller is designed according to μ-synthesis theory. The RCS includes two T-foils and two trim tabs; the cooperation control is studied and an allocation rule based on the principle of minimum system driving energy is optimized by an improved genetic algorithm with pattern search algorithm. Finally, comparative simulations demonstrate that the proposed RCS has superior anti-heave/pitch performance and robustness.

A design of T-foil and trim tab for fast catamaran based on NSGA-II

This paper proposed an optimization design for a ride control system (RCS) for fast catamaran. The ship vertical motions are predicted by 2.5-D theory. The hydrodynamic characteristics of T-foil and trim tab are given, and the dynamic stability of the system is discussed. On this basis, the ride control system optimization model in regular and irregular waves is established for a specific catamaran. The optimal solution is obtained by using non-dominated sorting genetic algorithm-II (NSGA-II).

Design ride control system using two stern flaps based 3 DOF motion modeling for wave piercing catamarans with beam seas.

A ride control system (RCS) based linear quadratic regulator (LQR) and genetic algorithm (GA) design is presented, to reduce the heave, roll and pitch motion (three degrees of freedom motion (3 DOF motion)) of the wave piercing catamarans (WPC) in beam waves. A detailed 3 DOF ride control model which consists of the coupling and decoupling relationships between longitudinal and transverse motion is proposed for the WPC vessel. And the complex hydrodynamic coefficients and disturbances induced by beam waves are analyzed. Moreover, two stern flaps are designed for the system in the way of alternate flapping. In the controller design, the LQR method based on GA method is adopted to reduce the 3 DOF motion of the ship. Depending on the robust search mechanism and global optimum of GA, weighting parameters can be obtained to calculate the desired gain. Finally, the motion reduction and motion sickness incidence (MSI) results demonstrate the feasibility and effectiveness of the proposed controller, and the comfort of passengers and crews can also be improved.

An experimental investigation on slamming kinematics, impulse and energy transfer for high-speed catamarans equipped with Ride Control Systems

The operation of high-speed craft in large waves can produce significant vessel motions that lead to passenger discomfort and extreme loadings sustained by the hull structure during full bow immersion and wave slam impact. These large motions and loads can be significantly reduced by a Ride Control System (RCS). The influence of ride control algorithms on the motion and load response of a 112 m high-speed wave-piercing catamaran was previously investigated by the authors using a 2.5 m hydroelastic segmented model fitted with a ride control system. The present study extends this to investigate the influence of the control algorithms on the slamming kinematics, water entry impulse and energy transfer. The model ride control system comprised two transom stern tabs and a central T-Foil beneath the bow. In order to activate the model scale ride control system and surfaces in a closed loop system six ideal motion control feedback algorithms were developed: local motion, heave and pitch control, each in a linear and nonlinear application. These results were compared with the results with inactive but present control surfaces and with no control surfaces fitted. From these analyses it was found that the pitch control mode was most effective where in 60 mm model scale waves it significantly reduced the water entry impulse by 40% and the total strain energy by 90% when compared to a bare hull with no control surfaces fitted.

An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 2: Mitigation of Wave Impact Loads

High-speed craft frequently experience large wave impact loads due to their large motions and accelerations. One solution to reduce the severity of motion and impact loadings is the installation of ride control systems. Part 1 of this study investigates the influence of control algorithms on the motions of a 112-m highspeed catamaran using a 2.5-m model fitted with a ride control system. The present study extends this to investigate the influence of control algorithms on the loads and internal forces acting on a hydroelastic segmented catamaran model. As in Part 1, the model active control system consisted of a center bow T-Foil and two stern tabs. Six motion control feedback algorithms were used to activate the model-scale ride control system and surfaces in a closed loop system: local motion, heave, and pitch control, each in a linear and nonlinear application. The loads were further determined with a passive ride control system and without control surfaces fitted for direct comparison. The model was segmented into seven parts, connected by flexible links that replicate the first two natural frequencies and mode shapes of the 112-m INCAT vessel, enabling isolation and measurement of a center bow force and bending moments at two cross sections along the demi-hulls. The model was tested in regular head seas at different wave heights and frequencies. From these tests, it was found that the pitch control mode was most effective and in 60-mm model-scale waves it significantly reduced the peak slam force by 90% and the average slam induced bending moment by 75% when compared with a bare hull without ride controls fitted. This clearly demonstrates the effectiveness of a ride control system in reducing wave impact loads acting on high-speed catamaran vessels.

An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 2: Mitigation of Wave Impact Loads

High‐speed craft frequently experience large wave impact loads due to their large motions and accelerations. One solution to reduce the severity of motion and impact loadings is the installation of ride control systems. Part 1 of this study investigates the influence of control algorithms on the motions of a 112‐m highspeed catamaran using a 2.5‐m model fitted with a ride control system. The present study extends this to investigate the influence of control algorithms on the loads and internal forces acting on a hydroelastic segmented catamaran model. As in Part 1, the model active control system consisted of a center bow T‐Foil and two stern tabs. Six motion control feedback algorithms were used to activate the model‐scale ride control system and surfaces in a closed loop system: local motion, heave, and pitch control, each in a linear and nonlinear application. The loads were further determined with a passive ride control system and without control surfaces fitted for direct comparison. The model was segmented into seven parts, connected by flexible links that replicate the first two natural frequencies and mode shapes of the 112‐m INCAT vessel, enabling isolation and measurement of a center bow force and bending moments at two cross sections along the demi‐hulls. The model was tested in regular head seas at different wave heights and frequencies. From these tests, it was found that the pitch control mode was most effective and in 60‐mm model‐scale waves it significantly reduced the peak slam force by 90% and the average slam‐induced bending moment by 75% when compared with a bare hull without ride controls fitted. This clearly demonstrates the effectiveness of a ride control system in reducing wave impact loads acting on high‐speed catamaran vessels.

An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 1: Reduction of Ship Motions

Ride control systems are essential for comfort and operability of high-speed ships, but it remains an open question what is the optimum ride control method. To investigate the motions of a 112-m high-speed catamaran fitted with a ride control system, a 2.5-m model was tested in a towing tank. The model active control system comprised two transom stern tabs and a central T-Foil beneath the bow. Six ideal motion control feedback algorithms were used to activate the model scale ride control system and surfaces in a closed-loop control system: heave control, local motion control, and pitch control, each in a linear and nonlinear version. The responses were compared with the responses with inactive control surfaces and with no control surfaces fitted. The model was tested in head seas at different wave heights and frequencies and the heave and pitch response amplitude operators (RAOs), response phase operators, and acceleration response were measured. It was found that the passive ride control system reduced the peak heave and pitch motions only slightly. The heave and pitch motions were more strongly reduced by their respective control feedback. This was most evident with nonlinear pitch control, which reduced the maximum pitch RAO by around 50% and the vertical acceleration near the bow by about 40% in 60-mm waves (2.69 m at full scale). These reductions were influenced favorably by phase shifts in the model scale system, which effectively contributed both stiffness and damping in the control action.

An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 1: Reduction of Ship Motions

Ride control systems are essential for comfort and operability of high-speed ships, but it remains an open question what is the optimum ride control method. To investigate the motions of a 112-m high-speed catamaran fitted with a ride control system, a 2.5-m model was tested in a towing tank. The model active control system comprised two transom stern tabs and a central T-Foil beneath the bow. Six ideal motion control feedback algorithms were used to activate the model scale ride control system and surfaces in a closed-loop control system: heave control, local motion control, and pitch control, each in a linear and nonlinear version. The responses were compared with the responses with inactive control surfaces and with no control surfaces fitted. The model was tested in head seas at different wave heights and frequencies and the heave and pitch response amplitude operators (RAOs), response phase operators, and acceleration response were measured. It was found that the passive ride control system reduced the peak heave and pitch motions only slightly. The heave and pitch motions were more strongly reduced by their respective control feedback. This was most evident with nonlinear pitch control, which reduced the maximum pitch RAO by around 50% and the vertical acceleration near the bow by about 40% in 60-mm waves (2.69 m at full scale). These reductions were influenced favorably by phase shifts in the model scale system, which effectively contributed both stiffness and damping in the control action.

Low Reynolds Number Performance of a Model Scale T-Foil

"Submerged T-foils are an essential forward component of the ride control systems of high speed ferries. A model scale T-Foil for a 2.5m towing tank model of a 112m INCAT Tasmania high-speed wave-piercer catamaran has been tested for both static and dynamic lift performance. The tests were carried out using a closed-circuit water tunnel to investigate the lift and drag characteristics as well as frequency response of the T-Foil. The model T-Foil operates at a Reynolds number of approximately 105, has an aspect ratio of 3.6 and a planform which is strongly tapered from the inboard to outboard end. All of these factors, as well as strut and pivot interference, influence the steady lift curve slope of the model T-foil which was found to be 61% of the value for an ideal aerofoil with elliptic loading. The T-foil dynamic performance was limited primarily by the stepper motor drive system and connection linkage. At the frequency of maximum motion of the 2.5 m catamaran model (about 1.5Hz) the model T-foil has approximately 5% reduction of amplitude and 15 degrees of phase shift relative to the low frequency response. Only very small limitations arose due to the unsteady lift as predicted by the analysis of Theodorsen. It was concluded that the model scale T-foil performed adequately for application to simulation of a ride control system at model scale."

An insight into the slamming behaviour of large high-speed catamarans through full-scale measurements

The slamming behaviour of a large high-speed catamaran has been investigated through the analysis of full-scale trials data. The US Navy conducted the trials in the North Sea and North Atlantic region on a 98 m wave piercer catamaran, HSV-2 Swift, designed by Revolution Design Pty Ltd and built by Incat Tasmania. For varying wave headings, vessel speeds and sea states the data records were interrogated to identify slam events. An automatic slam identification algorithm was developed, considering the measured rate of change of stress in the ship’s structure coupled with the vessel’s pitch motion. This has allowed the slam occurrence rates to be found for a range of conditions and the influence of vessel speed, wave environment and heading to be determined. The slam events have been further characterised by assessing the relative vertical velocity at impact between the vessel and the wave. Since the ship was equipped with a ride control system, its influence on the slam occurrence rates has also been assessed.

Full-Scale Motions Of A Large High-Speed Catamaran: The Influence Of Wave Environment, Speed And Ride Control System

To assess the behaviour of large high-speed catamarans in severe seas, extensive full-scale trials were conducted by the U.S. Navy on an INCAT Tasmania built vessel in the North Sea and North Atlantic region. Systematic testing was done for different speeds, sea states and ride control settings at different headings. Collected data has been used to characterise the ship’s motions and seakeeping performance with respect to wave environment, vessel speed and ride control system. Motion response amplitude operators were derived and compared with results from a two-dimensional Green function time-domain strip theory seakeeping prediction method. An increase of motion response with increasing vessel speed and a decrease with the vessel moving from head to beam seas was found. In higher sea states and headings ahead of beam seas an increasing influence of the centre bow on pitch motion damping was found. Significant motion RAO reduction was also found when the ride control system was active. Its effectiveness increased at higher speeds and contributed to heave and pitch motion RAO reduction. Predicted motion magnitudes with the time domain seakeeping code were consistent with the measured motion responses, but maximum heave was predicted at a rather higher frequency than was evident in the trials.

A computational tool for the design of ride control systems for fast planing vessels

An effective method to reduce the violent motion behaviour of fast planing vessels in waves may be found in the application of active control devices in conjunction with advanced motion control systems. This study aims to develop a computational tool for the design and optimization of these ride control systems for high speed planing monohulls. Hydrodynamic characteristics of both transom flaps and interceptors are determined by systematic series of model test experiments in the towing tank of the Laboratory of Ship Hydromechanics at the Delft University of Technology. Transom flap results at downward deflection angles are validated with formulations found in literature. In addition, experiments at up angle flap positions have been performed to increase the range of application for motion control purposes. The hydrodynamic performance of the interceptors and transom flaps are compared in order to determine their efficiency. The experimental data was implemented in a nonlinear time domain mathematical model that can predict the seakeeping behaviour of fast monohulls. Simulations demonstrate the improvement in motion behaviour of a fast planing vessel with a ride control system sailing in head waves. 2011 - IOS Press and the authors. All rights reserved.