With the use of simulation models, predicting and optimising the correct dynamic behaviour and parameters of a propulsion system of a ship can be performed cheap and safe. However, capturing the right dynamic behaviour is very difficult. Besides, building simulation models and determining the correct parameters is a time consuming process. With system identification, in- and output data of a controlled test are used to identify the parameters of the created grey box model structure, which reflects the underlying physical laws. A so called "fingerprint" is generated that imitates the behaviour of the system. The first attempt of system identification of a full-scale propulsion system showed promising results but asked for further research. This thesis further investigates if system identification is a suitable method to obtain the dynamic model- behaviour and parameters of a full-scale propulsion system in a short time, with the use of controlled tests. ... Read more

During the energy transition, a wind-assisted ship propulsion system has the potential for increasing energy efficiency according to the ship’s EEDI (Energy Efficiency Design Index) in the short term. However, it would not only make the diesel engine run in off-design condition, but its dynamic behavior due to time-varying wind and waves is still unknown. Hence, for a selected case used in this thesis, a Flettner rotor is chosen to be further evaluated on the system’s dynamic behavior under its favorable wind angle at Beaufort scale 6 and 7.

After modeling the wind-assisted ship propulsion system, it was linearized and normalized around its static operating point. This gives more insight into the system from a frequency-domain analysis via the Bode magnitude plots of engine speed, engine torque, and ship speed to the variation of true wind speed and wakefield induced by wave amplitude disturbance. In addition to the time-domain simulation for understanding the impact of the wind and wake disturbance on the system, the system response spectrum, which was proposed as an alternative approach for analyzing the system’s dynamic behavior, was derived by connecting wind and a derived wake spectrum to the Bode magnitude plots. Therefore, how the energy is conveyed from the marine environment to the system around its equilibrium can be tracked clearly.

Consequently, according to the selected case with a given controller, the results show that the fluctuation of true wind speed directly influences the ship speed, which in turn makes the engine torque be more sensitive to the variation of true wind speed in low-frequency regions. Besides, the engine speed resists to the variation of true wind speed very well due to the controller’s introduction. Although the Flettner rotor generates approximately 44% of thrust at Beaufort scale 7, the true wind speed disturbance does not result in a significant engine loading disturbance compared with the fluctuation of wakefield, which significantly influences the engine speed and torque. It was found that it is related to the frequency region where the wake spectrum overlaps with the system sensitivity function. Within this region, the controller has a relatively poor performance, and thus an engine operating cloud can be noticed in time-domain simulation. However, the ship speed is not influenced significantly by the wakefield disturbance because the frequency region of wake spectrum does not overlap with that of the transfer function where the ship speed is more sensitive to the variation of wakefield. Finally, the sensitivity study implies that a further increase of ship total mass and moment of inertia enlarge the engine speed and torque in the frequency region where the controller does not perform well.

In conclusion, based on the selected case under its favorable wind condition, the potential of the wind-assisted ship propulsion system is still promising. Furthermore, the linearised model is a useful additional tool, and the system response spectrum gives more insight into the system.
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The awareness of the climate change is increasing and the effect of air-pollution is irrefutable. To decrease the emissions of large ships the required amount of fuel has to be minimized. This is done by increasing the efficiency of the engine, decreasing the hull resistance or by lowering the cruise speed. Another interesting way of decreasing the emission is by using Wind Assisted Ship Propulsion (WASP). The Turbosail is a promising type of wind propulsion for this purpose introduced by Jacques Cousteau[4]. The Turbosail is an aspirated wing which is able to generate up to 3 times more lift compared to a non aspirated wing. A lot of research has been done in order to increase the performance of the Turbosail. But this research has mainly been done on the outside of the Turbosail and the suction area is often modelled as an area with a uniform flow. In this research a model has been made in order to give insight in the behaviour and sensitivity of the suction system of the Turbosail. First the model foundation is described. A lumped parameter approach is chosen and the structure of the model is described. The model of the fan is described and after this the total model is made using Matlab Simulink. This model is made such that the number of elements (the amount of parts that the Turbosail is divided in) can be easily varied. This is done in order to perform a convergence study. Followed by a mathematical verification with carefully chosen tests the model is considered as verified. To understand the sensitivity of different parameters of the system a parameter variation is performed. Different parameters are varied and their effects are simulated. This yields insight in the sensitivity of the system and can be used in order to optimize the energy efficiency of the total suction system. Finally two possible improved designs are simulated combined with their decrease in power consumption. These results can be used for future simulations and designs with the main purpose to decrease the energy consumption of the shipping industry. ... Read more

Dynamic model parameters (e.g. governor) are uncertain and hard to validate. A possible solution can be the usage of parameter identification techniques. So far parameter identification techniques have proved their potential in identifying model parameters on model scale, but this has never been applied on a full-scale propulsion system. During this thesis an attempt is made to estimate the dynamic model parameters of a Stan Tug 1205.
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Ventilation events are the result of masses of air being transported from the water surface along the hull, through the propeller plane. Previous research in literature has shown that ventilation induces large and sudden variations of the load on the propeller. The response of the propulsion system had not been documented before. This is a problem with practical and theoretical relevance as both operators and designers of ships and propulsion systems cannot predict the response of these systems to these significant and sudden variations of the propeller-load. The problem can manifest itself in different ways. A first example lies in a possible loss of propulsion and the damages that could incur. A second example lies in the possible installation of too much engine power to respond to unpredictable load-variations such as those incurred by ventilation events. Increased understanding of the relation between wave properties, -height and -frequency, and the response of a marine Diesel engine, -speed and -torque, subjected to wave-induced ventilation, is the goal of this thesis and leads to the main research question: How does a marine Diesel engine respond to off-design loads, and in particular to frequently varying loads resulting from propeller ventilation? It focuses on the response of the prime-mover to variations of the propeller-load imposed by ventilation events. The scope of this thesis covers a monohull coaster with a medium-speed marine Diesel engine moving forward in head seas. A model is proposed based on the description of immersion by Journée and Massie (2001) [19]. It consists of three sub-models that describe vessel-motion, the propeller and the prime-mover. The vessel-motion is described with a combination of potential-flow based methods and viscous theory. A quasi-static approach is proposed to describe the influence of ventilation on propeller-functioning. The prime-mover is modelled with a closed-cylinder process and an idealised first-order turbo-charger model that applies the exhaust-flow temperature of the closed-cylinder process to describe the charge-pressure. Three limits to this model lie in the application of vessel-motion data in a limited, positive domain, the application of 1st quadrant propeller data and the propeller envelope. This model uses input consisting of waves and the engine speed setpoint. The output consists of the rotational speed and produced torque of the prime-mover subjected to ventilation. Verification showed responses comparable to, and in the range and time frame of experimental results by Koushan (2007) [21]. Validation efforts lie beyond the scope of this thesis. Experiments by means of simulations have been performed for two engine speed setpoints and different wave-types describing head seas: Regular waves characterised by low frequencies, -characterised by high frequencies and -characterised by different wave amplitudes. A final experiment subjected the model to an adverse long-crested wave-spectrum for ocean waves. The research at hand found that the propeller immersion-ratio couples imposed waves and vessel-motions, to the inception of ventilation events. The quasi-static approach to model the influence of ventilation on propeller-functioning provided a reasonable estimate in verification, although further validation efforts are still required. The main research question led to the answer that: Frequently varying loads resulting from propeller ventilation can induce a significant shift in the operational point in the propellers open-water diagram and engines PV diagram and increase of the variations of engine speed and -torque. The final chapter also provides a number of pointers for a further validation effort, possible improvements to the proposed method and advice regarding further research. ... Read more

During offshore construction with a Semi-Submersible Crane Vessel (SSCV) the vessel is station keeping by means of Dynamic Positioning (DP). DP enables a vessel to keep position and heading by utilizing its own propulsion, while being exposed to the environmental forces caused by waves, wind and current. In a comparison study between offshore measurements and time-domain simulations, an increased vessel/thruster response for the offshore measurement was observed. The results revealed, that in operational environmental conditions, the measured vessel response shows increased oscillations in Surge, Sway & Yaw, with periods of approx. 3-5 min. The goal of this thesis was to determine the causes for such an increased dynamic vessel response, which are not captured in time-domain simulations. At present, numerical methods and time-domain simulations that assess the DP performance of a vessel (e.g. aNySIM) assume a quasi-static current of which the variation is only caused by the tides. One thesis is, that time-varying currents on a scale of 1 to 5 minutes can cause an increased vessel response. Furthermore, the DP System as it is used onboard is not captured in aNySIM simulations. This means that the characteristics of the DP System onboard are but not represented in full detail in time-domain simulations. Vortex Induced Motion (VIM) has previously been observed to affect multi column floaters. However, the influence on a SSCV during DP-operations has not yet been studied. In this thesis it was investigated whether the unexpected increased motions originate from time-varying currents, VIM or the DP System itself. A significant challenge was posed to find current measurement data with a small enough time step to confirm the presence of such time-varying currents. One 45 min current measurement with a sampling rate of 1Hz became available. This measurement shows that time-varying currents on a scale of 1 to 5 minutes exist and cannot be assumed to be quasi-static. More research is required to confirm their presence. However, with this limited available data it was shown that time-varying currents can cause an unexpected motion response of a SSCV during DP-operations.In order to obtain the DP System characteristics, a DP Response Amplitude Operator (RAO) assessment was conducted wherein the spring and damping terms were derived as demanded by the controller and as experienced by the vessel. This assessment showed that between 20% to 67% of the demanded critical damping is lost over the control loop of the DP System. These damping losses cause the vessel to overshoot and the damped natural period to decrease. To determine the effects of VIM, current load tests carried out on the hull of an SSCV have been investigated. It was determined that strong currents on column type floaters can cause fluctuating forces and moments that originate from vortex shedding. Further, with real-time simulations it was demonstrated, that also VIM causes an increased, previously unknown, motion response of a SSCV. Lastly, a method was developed to extrapolate the current load test results to velocities below 2kn. Subsequently, in time-domain simulations it was shown that for current velocities above 0.5kn, the vessel experienced forces and moments that caused it to fluctuate around its setpoint. ... Read more

During dynamic positioning operations, vessels typically run with an extra generator (spinning reserve) for redundancy purposes such that no single fault will cause the vessel to lose its position or heading. As a result, all other engines on the grid share the load equally to ensure that if a failure were to occur, the remaining healthy generators would be sufficient to satisfy the total power demand. As DP vessels operate on a split-bus mode, the redundancy requirement must be satisfied across both switchboards on the vessel. Past research has shown that significant fuel and maintenance savings can be made by eliminating the spinning reserve with a battery energy storage system. However, as Lithium-ion batteries are relatively expensive, efforts have been made in the past to attempt to incorporate a single battery system than can be connected to either switchboard in the event of a failure, however the analysis was conducted only for deep-water pipelaying operations. Shallow water operations are characteristic of large power surges in contrast to deep-water operations which has been the limiting constraint in ESS design and architecture. In this research, a solution was developed as a split battery design which is arranged such that the power surges can be handled by two independent units connected to one switchboard while a tertiary unit from the secondary switchboard can be independently connected to the one switchboard wherein a failure has occurred, hence acting as a spinning reserve. This allows all the battery units to be maintained at a low state of charge, which maximises the battery life. To complement the design, two power management system integration methods were pursued. Firstly, a rule-based monitoring system was developed which allowed the power management system to make generator start-stop decisions based on a back-looking principle of measuring power demand and power surge characteristics experienced by the battery. This resulted in fuel savings of 3.14 tonnes and a running hour reduction of 52.5 hours. The average engine loads improved on average 10-20\% in contrast to the current situation on the vessel and milder weather scenarios showing nearly a 30-40\% improvement.
And secondly, a neural network based machine learning approach was used to forecast the vessel loads for the day ahead using weather and route plan parameters.The results suggest that in contrast to the rule-based system, the forecast model overestimates or underestimates the load which causes the fuel savings and running hour reduction to be less than the former control strategy. The neural network training was conducted on a data sample of approximately 2 million data points which was found to be insufficient to capture all the dynamics. In the scenario that the model can be trained on several years of data, it could be possible to forecast the load with enough fidelity to allow a 38\% reduction in ESS sizing compared to the base case design used with the rule-based control system.

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Offshore operations are increasingly executed by vessels operating on dynamic positioning (DP) due to advantages it has for short operations, such as maintenance and crew transfer but also for track keeping operations and projects in deeper water. Currently, DP capability plots are used to indicate whether an operation can be performed, but this is based on static calculations and it does not consider the offsets that are found due to motions of the vessel, while the offsets can be critical in case a structure is present or if a certain accuracy of a station keeping operation is necessary. Currently, to determine the offsets of a vessel on DP, the system is modelled using a time domain approach. Multiple simulation runs are carried out to calculate the expected extreme offsets in a given time interval, which is known as the most probable maximum offset (MPM offset). This is a complex and time consuming process and therefore it is not always done in practice before an operation starts. In this research, a method is developed to estimate the surge MPM offsets of a vessel on DP due to the wave drift forces using a frequency domain approach, as this can lead to faster estimates. But two problems are faced: The first is that there is no mathematical model available describing a vessel on DP which can be used to accurately calculate the offsets in the frequency domain. The second problem is that there is no known relation between the offsets and the extreme behaviour, which leads to the MPM offsets. To find the MPM offsets, first of all a one-dimensional time domain model of a vessel on DP is made, considering only the surge degree of freedom. Next, to determine the surge offset response using a frequency domain approach, the differential equations of the system are linearised, which gives the transfer functions from the environmental forces to the surge offsets. This is used to estimate the surge offset response in the frequency domain. The accuracy of this method is determined by comparing the root mean square value (RMS) and the zero up crossing period to that of the time domain results. Then, two alternative methods are developed to calculate the MPM offsets from the surge offset response characteristics directly. The methods use the RMS and zero up crossing period of the surge offsets calculated in the frequency domain, to determine the extreme behaviour statistically without the use of multiple simulation runs. Using the linearised model of the vessel on DP, it is found that the surge offset response can be calculated within an accuracy of 4% of the results generated by the time domain simulations, based on the root mean square value and the zero crossing period. Therefore, an accurate estimate of the surge offsets is found using a frequency domain approach. Both alternative MPM offset calculation methods, using the surge offset results of the linearised model, give MPM offset estimates within approximately 10% of the results of the time domain simulation approach. Taking into account the strong variability found in the MPM offsets calculated by the time domain approach, the estimates from the frequency domain approach are regarded as good estimates.
It is concluded that the methods developed in this research can lead to faster and therefore timely MPM offset estimates to use for the safety and accuracy of operations. This can improve the way of working for many offshore operations where often no use is made of MPM offset estimates due to the disadvantages of the methods currently used in practice. It is recommended to extend the method developed in this research to three degrees of freedom, such that it can be implemented in practice. ... Read more

Allseas Engineering B.V. is an offshore contractor, focussed on offshore pipeline installation. Since the late 80's, Allseas has been working on the design and construction of the Pioneering Spirit, a heavy lift vessel designed for the single-lift installation and removal of offshore topsides. From 2019, it is scheduled to be able to single-lift install or remove jackets with the jacket lift system.

The jacket lift system is located at the aft of the vessel and consists of two 170 meter tilting lift beams, hinged around the stern. During a jacket removal, the jacket is cut-off at the bottom, hoisted from the tip of the beams, partially rotated, and then tilted inboard. In between the hoisting and tilting is the transition phase. At the interface between jacket and the tilting lift beams, jacket support structures are located. In this thesis, the behaviour of the free-hanging of the jacket and the loads on these support structures due to the mating with the jacket are researched.

Jacket removal operations will take place in open sea and are thus subjected to environmental actions. The jacket, suspended from the tip of the beams, is excited due to fluid acceleration and velocity causing inertia forces and predominantly drag forces on the slender members of the jacket, as well as the excitation of the vessel through the suspension point. These motions are calculated with two different approaches. A direct-time domain model is developed of the jacket as submerged pendulum. To accelerate model simulations, the jacket is modelled as one single cylinder with different equivalent diameters to account for the total of drag and inertia. The second model is a full geometrical time-domain model simulation in AQWA.

In the design sea state, simulations showed that the most probable maximum momentum of the jacket due to environmental excitation is 4.5 106 kg m/s, and the motions of the centre of gravity of the jacket are all within a range of 1 meter, for the single and double pendulum and the full model. The influence of the environmental actions on motions of the structure is concluded to be small. This suggest that the jacket mating loads are governed by the tilting velocity of the tilting lift beams and the motion of its tip. The jacket mating simulations are done in the full AQWA model approach.

Fenders are modelled to absorb energy during the jacket mating. A sensitivity analysis showed that the parameters that have most influence on the mating phase characteristics are the tilting velocity and the stiffness of the fender. From still water conditions it seems that by increasing or decreasing the tilting velocity, this can affect the number of re-bounces and the maximum deflection. With increasing sea state, the duration and intensity of the mating phase increases. The fender deflection will increase for increasing significant wave height. The wave period does not have a significant influence on the maximum fender force. The amount of re-bounces reduces significantly for higher damping coefficients, while its influence on maximum deflection decreases.

The maximum force on the jacket support structures caused by the static gravitational force by the jacket once it is fully tilted is approximately 10 times higher than the maximum occurring force exerted on one of the fenders. Therefore, this static gravitational force is critical for the design of the jacket support structure, not the force caused by the mating.
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Crew of small fast ships often experience exces- sive vertical accelerations when sailing in waves, leading to discomfort and injuries. In an attempt to avoid this, in good visibility experienced operators reduce speed voluntarily when they anticipate that the next vertical peak acceleration will be unacceptably large. However, at night and during excessive spray, the operator can hardly see the environment which makes it almost impossible to anticipate wave driven events. On top of that, this approach carries the risk of operator misjudgment due to loss of concentration or fatigue. In this paper, the potential of haptic feedback to support the operator in preventing dangerously large vertical accelerations is inves- tigated. A stochastic based approach was used in combination with a high end ship simulator to construct a haptic algorithm which gives a maximum advisable propeller speed setting based on an estimate of the current sea state. In order to test the effectiveness of this approach, a human-in-the-loop experiment was conducted using a within-subject design with 24 conveniently sampled participants. In this experiment the effect of haptic assistance is compared to manual control under both good and reduced visibility conditions. A key advantage of implemented haptic feedback algorithms is that the human remains in the control loop and can continuously decide to overrule the haptic advice. From the experiment it is found that the workload experienced by the operators is significantly decreased when using haptic feedback. However, no significant decrease in the number of excessive vertical accelerations was found using the current setup. A possible explanation for this result is the lack of motion cues and the inexperience of the participants. Therefore, it is recommended to extend the setup with a motion platform and conduct future experiments with experienced operators. ... Read more

The FRISC is a high speed craft of the Netherlands Navy which came into use in 2012. Because these vessels sail with speeds up to 45 knots in inshore waters, a large amount of focus and accurate path following is needed for safe navigation, and due to large accelerations, there is a high level of physical strain. These two factors cause a high (prolonged) mental and physical workload which can heighten mental and physical fatigue, resulting in higher risks due to reduced alertness and mental performance. With this in mind, the focal point of this thesis is to increase the safety of the FRISC during high speed navigation by increasing the path following performance and reducing the level of fatigue through lowering the workload. With extensive literature research a possible solution was found to increase the safe navigation. Namely, haptic feedback which will decrease the workload and increase the path following performance. With this in mind, the following research question arises:
To what extent can haptic feedback, implemented into the steering system of the FRISC, contribute to safe navigation during (nightly) high speed inshore navigation?
A FRISC operates with high speeds in inshore waters, following a well prepared detailed planned route. During such an operation the FRISC is subject to performance shaping factors, factors “which influence the likelihood of an error occurring” [1]. With the use of the literature, a possible solution for almost all the factors, related to the FRISC, were found. This solution is a haptic feedback system which will lower the workload and increase the path following performance. An active guidance system is developed with two types of controllers (waypoint controller and XTE controller) to “advise” the operator with the correct rudder angle, to follow a preplanned route during high speed inshore navigation. The contribution of this thesis is tested by the implementation of a haptic shared control, and by investigating the cross track error and the workload. The results of the investigation of the XTE were unambiguous. The XTE controller lowers the mean and median XTE values by 20% and the absolute maximum value is lowered by 37% compared to manual control. The waypoint controller resulted in higher XTE values which means that manual control has the preference above the waypoint controller based on the XTE. Furthermore, the participants indicated that the perceived workload was 37% and 44% lower with the use of the waypoint controller and XTE controller respectively. The physical workload was compared between the experience of the participants and the measured physical demand. This comparison resulted in the fact that the experience of the participants was not in line with the actual physical effort. The physical effort was the highest with the use of both controllers whereas the experience of the physical workload was the lowest. This was assumed to be less important than the perceived workload and therefore it did not influence the conclusion of haptic feedback lowering the workload. Altogether, it is stated that the use of the correct haptic shared control system could increase the safety of navigating during (nightly) high speed inshore navigation.
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Currently there are three methods of calculating the Dynamic Positioning capability of a vessel namely: static calculations, real-time time domain simulations and fast-time time domain simulations, although the outcome of the last two should be identical. In each of these methods a set of input variables is required to perform the calculations. These inputs are not always exactly known and are therefore sometimes estimated or taken from databases. It is not always clear how big the uncertainty in these estimated inputs is, and on top of that: how big the effect on the predicted DP capability is. To be able to quantify how certain a DP capability calculation is and which input data contribute most to the output uncertainty, in this thesis the input uncertainties for both static and fast-time dynamic calculations are investigated. Each method is subdivided in three different design stages which are: conceptual design, preliminary design and as built design. For the static calculations all three design stages are evaluated but for the fast-time dynamic simulations only the as built stage is considered.

The static calculation part of the analysis consists of determining the input uncertainties, the input sensitivities to the output and finally calculating the output uncertainty. The method used for this calculation assumes that either the relation between input and output is linear or can be linearised at the point of interest. The input uncertainties are calculated using historical data of the Bibby Wavemaster 1 which is the vessel used as case study throughout this thesis and is specifically designed for the purpose of servicing offshore wind farms. It is observed that the input uncertainties of the main dimensions of the vessel are clearly reducing when moving through the design stages. Furthermore it is concluded that the environmental coefficients of wind, waves and current are the most uncertain, even in the conceptual design stage where input parameters of the main dimensions of the vessel vary the most. When considering the sensitivity in the three design stages no big changes were observed, meaning that in all design stages the main dimensions of the vessel are most sensitive to the output. Finally the uncertainty in the output was evaluated were it was observed that for the as built stage still a standard deviation of 4% uncertainty of the output is present, resulting in a calculated 99.7% confidence interval of either 12% too high or too low.

In the dynamic calculation part only the as built stage is considered. Again the uncertain parameters are defined but due to the PID controller in the dynamic model some new input parameters are now present. The gains of this PID controller are assumed to be uncertain and are therefore taken into account during the dynamic uncertainty analysis. Due to a limitation in the aNySIM licence bought by Damen it is impossible to change the wave coefficients which causes their uncertainty not to be taken into account. Since the dynamic simulations are considered to have strong non linearities and possibly even discontinuities due to thruster saturation, the calculation method used for the static part is not applicable anymore. Therefore it is decided to use Monte Carlo simulations to quantify the uncertainty in dynamic DP calculations. Due to the large computational time required to perform large amounts of Monte Carlo simulations with aNySIM, a machine learning method is used to capture the dynamic behaviour of the vessel. A small number of simulations performed by aNySIM is required to train the model which are selected using the Sobol design of experiments technique. This technique optimises the choice of the simulation points to make sure the complete space of possible inputs is covered. By using the machine learning model to obtain an output of a dynamic simulation only a fraction of a second is required instead of 17 minutes when using aNySIM. By running the Monte Carlo simulation on the created machine learning model it was observed that the 97.7% confidence interval for offset can either be calculated up to 8.7% too low or too high whereas the prediction for heading up to 23.1% too low or too high when compared to the base case. It is concluded that using DP for the purpose of people transferring by means of a "Walk To Work" bridge, uncertainties should be taken into account to reduce both safety and contractual requirements risks.
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This Thesis is written to obtain the Master of Science degree of Maritime Technology at Delft University of Technology. It describes a research regarding with the calibration(parameter identification), validation and linearization of a ship propulsion system model. In the meantime, the Thesis is also one sub-project under the research program "Potential of Hardware-In-the-Loop Simulation in the Towing Tank" held by Dr.Ir.A.Vrijdag. HIL (Hardware-In-the-Loop) Simulation is widely used in Engineering Technology Field, and has been proved to be a very effective, highly-efficient, economical and environmental friendly strategy in the test and development of engineering control systems. The model scale ship tests nowadays, on the other hand, need to be improved and HIL Simulation provides an innovative & creative way, therefore it is reasonable to start the program and explore more in this field. ... Read more

The need for advanced ship propulsion control systems is constantly increasing as the demand for high vessel performance is growing at the same time. Speed trials are considered as an operation during which the vessel has to achieve the highest performance by attaining the agreed maximum ship speed. However, sometimes vessels have to sail in waves during speed trials. In such case, resistance and wake field disturbances act on the vessel’s propulsion plant causing fluctuations of the engine’s operating point in the engine operating envelope. When these fluctuations are large enough to reach the engine’s operating envelope limits, the propeller pitch control is activated to effectively protect the engine by reducing the propeller pitch. This decrease results in reduced average delivered power, reduced average generated thrust and finally in a drop of maximum average ship speed. This work focuses on investigating the possibilities to refine the existing control system by means of gain scheduling the Diesel engine speed governor. The ultimate goal is the re-sizing and re-orientating of the engine’s operating point fluctuations in the engine’s operating envelope, keeping the propeller pitch control deactivated and thus, the maximum average speed retained. First of all a linearised model of the ship propulsion system is derived which is used for the analysis of the Diesel engine’s operating point dynamic response in terms of engine torque and engine speed fluctuations in case of regular waves. More specifically, this thesis investigates the impact of the direction of the ship with respect to the waves, the Sea State and the system operating point on the dynamic response of the engine’s operating point in the engine’s operating envelope. Based on the analysis of the dynamic response of the engine’s operating point with respect to the three above mentioned factors and by making use of the linearised model, the refinement of the Diesel engine’s dynamic behavior is achieved. In the first place, a static solution is given with the derivation of suitable plots. The derived plots provide the opportunity for manual governor gains scheduling, depending on the wave induced disturbance. In the second place, a gains scheduling algorithm is obtained by combining the linearised ship propulsion model with an optimization algorithm. The developed algorithm, after being integrated in the non-linear simulation model of the ship propulsion system, is capable of dynamically scheduling the governor gains in case of regular and irregular waves. Both obtained solutions achieve the ultimate objective of this work. The fluctuations of the Diesel engine’s operating in the engine operating envelope are effectively re-sized and re-orientated. As a result the activation of the propeller pitch control is prevented and the average ship speed is retained. ... Read more

Experience-based decision making by crew plays a key role in the safe and effective execution of maritime operations. For yachts and naval vessels, common operations can be identified as helicopter operations (take-off and landing), launch and recovery of small craft and (dis)embarkment to and from these small craft. All of these operations are limited by wave-induced ship motions.

For these operations, experience-based decision making does however not always guarantee that the operations are carried out in the most safe and effective manner possible. Also, the level of comfort as experienced by a yacht-owner or guests can be directly affected by this type of decision making. With this in mind, Feadship aims to develop a Feadship Comfort System (FCS), which can contribute to the decision making process. One of the elements of this system is ought to be a waveradar. The aim of this thesis is to describe how the waveradar can be included effectively in the FCS, and how it can be used for the above mentioned operations.

The waveradar is in basis a common navigation radar that can perform measurements of the surface elevation in the direct surrounding of a vessel. These measurements can be used to predict the ship's motions up to approximately two minutes ahead in time. With this, windows of opportunity can be distinguished when operations can be carried out best. These windows depend on the corresponding limiting criteria that are set on the ship's motions. A major issue is however that sea trials have shown that the roll prediction is inaccurate.

Due to this problem, two methods are evaluated in this thesis to improve the accuracy of the roll prediction. These methods are set up such that they are practical in use and can be applied directly to the deterministic wave predictions from the waveradar. The first method is scaling the response based on the roll motion history, whereas the second method is based on scaling the roll damping. The latter is effectively linearising the viscous contribution to the roll damping.

As no data from sea-trials is present to compare these methods, a benchmark calculation is carried out based on Cummins approach. In these time-domain calculations, a linear and non-linear roll damping coefficient are taken into account, which are based on a decay test that is available at De Voogt Naval Architects (DVNA). This follows from model tests performed by MARIN.

Comparing both methods to this benchmark calculation showed that the method of scaled damping resulted in the best approximation, with a Pearson correlation coefficient of (only) 33 %. Also, in terms of the behaviour of the motion envelope, this method showed the closest approximation of the two methods. It is found that the way in which both methods influence the RAO of the roll motion has a great influence on the results found. More suitable methods that should provide a better approximation are suggested from this, such as a frequency dependent scaling of the roll damping. This is however not discussed further.

With the method of scaled damping, the practical application of the waveradar within the FCS is evaluated. For the common operations of yachts and naval vessels, limiting criteria on ship motions are obtained from literature or stated by the author. The majority of these criteria are RMS values, for which a method is suggested to use them real-time. In this method, the most probable maxima are obtained from the RMS criteria, which are then applied as real-time criteria. This showed impractically large results, which showed that this method does not suffice.

From this conclusion it follows that the analysis of the practical application of the waveradar is only carried out for the (dis)embarkment of small craft. From this, design considerations for the FCS are obtained, from which the main result is that heading suggestion is one of the most important tasks that the system needs to be capable of.

Finally, a performance monitor has been evaluated for yachts at anchor. This performance monitor displays the predicted Comfort Rating (CR) real time, which can be used by the yachts crew to evaluate the current anchor location. This is a specific desire of Feadship and is developed next to the other operations. For this application, heading suggestion is also one of the most important tasks that the FCS needs to be capable of.
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