For the shared mobility service providers, it is essential to have an economic operation and therefore, it is necessary to maximise their fleet utilisation. Of influence on the latter is the availability of the spare parts. The topics for which spare part forecasting research is already performed are different in several ways compared to the field of free-floating shared vehicles. The many different users with each different driving skill, wear and tear by operation, events as vandalism and traffic accidents and constantly standing out on the street result in sudden failures of parts. Three different forecast models are presented in this paper. The effect of including demand generating factors in the forecast approach is analysed. The methods show that a better forecast performance can be achieved while including demand generating factors into the analysis. The forecast accuracy can be further improved and some suggestions for improvement are given in the paper.

The demand for renewable energy is growing, due to a growing awareness among people about the effect of burning fossil fuels on the environment. Governments have signed climate agreements and are obliged to decrease their level of exhaust gasses. This change in attitude regarding the environment led to an upcoming market for renewables. A significant part of the demand for renewable energy is covered by the wind industry, both on- and offshore. Especially the offshore wind market holds huge potential, due to stable wind conditions and growth opportunities. A side effect of the evolving industry is that turbines are increasing in size and are being installed in deeper water depths. It is expected that the methods of installation, currently used in the offshore wind market, will no longer be suitable for the installation of new generation turbines. In this research, installation of offshore wind turbine towers using a heavy lift vessel (HLV) is opted as an alternative to the current installation methods (jack-up installation). The major benefits of floating installation, when compared to jack-up installation, are the independency on both soil conditions and jacking operations. A challenge of floating installation, however, is the introduction of vessel motions resulting in excitation of the tower. The main objective of this research is to find the most efficient way to control the motions of the tower during installation using a HLV. To fulfill this objective, first, a conceptual design study has been conducted, which focused on developing concepts for the safe installation of offshore wind turbine towers using a HLV. Safe installation was assumed if the displacements of the tower bottom maintain within limits, as specified in a list of design requirements and criteria. Before examining any concept in more detail, the response of the tower and the effect of applying a form of motion compensation has been examined in a general way. To test the response of the tower in the crane in a general way, with and without motion compensation, the tower in the crane has been represented by a double pendulum system with a moving support point. Then, using the numeric model, the response of the tower in the crane has been computed for certain sea-states in both frequency- and time domain and for both the free hanging- and the motion compensated case. The motion compensation system has been represented by a virtual spring damper system, of which, by changing the simulation parameters, the optimal configuration (position, stiffness and damping) has been determined that minimizes the tower response. From the results, it can be concluded that a significant reduction of the tower bottom displacements can be achieved under the application of an active motion compensation system, the requirements for safe installation, however, are not yet fulfilled.

In the competitive offshore wind installation market, contractors like DEME strive to optimize operations. This thesis centers on the optimization of the support vessel fleet composition, which consist of a num- ber of walk to work vessels, and are a crucial part of inter-array cable installation. By fine-tuning this composition, operational expenses can be reduced by 10-20% to current industry practices. The cable installation process involves a complex set of operations, each necessitating a crew to be present on the foundations. Support vessels play a central role in routing of these crews and their equip- ment to these foundations.This thesis introduces an innovative approach that integrates operational scheduling and crew routing into a single formulation for optimizing the fleet of walk-to-work vessels. This hybrid model combines elements of a continuous-time rich multi-visit multi-period Vehicle Routing Problem with a time-varying Resource Constrained Project Scheduling Problem. It also factors in the substantial impact of weather conditions on offshore operations by accounting for variable weather win- dows in each scheduling period. The formulated model is rigorously verified and validated to ensure it closely mirrors real-world sup- port vessel behavior. Although it slightly underestimates fuel consumption, this discrepancy is deemed acceptable given its minor role in the overall objective. Sensitivity analyses highlight the critical impor- tance of accurate performance data for the cable laying vessel, which significantly influences the model’s outcomes. However, the model is found to be most effective for modeling a single cable string compris- ing 6-8 turbines, with scalability issues arising when attempting to expand beyond this scope. A focused case study delves into the impact of various weather conditions and inter-array distances on the optimal vessel composition. The study evaluates two types of walk-to-work vessels, individually and in combination. Results reveal that, under the assumption of zero downtime, the industry norm of chartering cheaper vessels is cost-effective, while the pricier vessel results in a 10% costlier solu- tion. As weather conditions worsen, a composition of costlier vessels proves more cost-effective over the scheduling horizon. Such conditions are to be expected in far offshore locations, especially on the cheaper vessels, which have lower workability limits. The study identifies potential cost reductions of up to 25%, with even marginal downtime conditions yielding 10-20% reductions to the industry standard. Moreover, delays imposed on the cable laying vessel are significantly reduced when utilizing a compo- sition that includes at least as one of the more expensive vessels. In summary, this thesis establishes a foundation for optimizing support vessels in offshore wind installa- tion. The presented model introduces a novel framework, combining multi-visit routing with time-varying resource scheduling, while considering shared vehicles and coupled routing and scheduling over a multi- period horizon. For regions prone to harsh weather conditions, such as those further offshore and during winter months, it is advised to utilize more expensive vessels that have higher workability limits and bet- ter performance figures. Additionally, there appears to be limited justification for simultaneous use of multiple vessels during the cable installation, as the added costs do not seem to outweigh the marginal improvements in installation duration. Future research should focus on refining solution methods for the proposed formulation and incorporating crew transfer vessels into the fleet composition.

Due to the global climate change there is a increasing demand for transportation on renewable fuels. An increasing trend in electric propulsion can already be seen in the automotive industry and this is now also gaining popularity in the maritime sector. Due to limited capacity if the onboard battery, especially electric ferries are becoming more popular, because of the relative short sailing distances. The first electric ferry became operational in 2015 in Norway and since than a hand full of electric vessels was developed. An electric vessel requires a charging mechanism to charge while unloading and loading passengers in the port. Besides, generally also a mooring mechanism is necessary. This enables the vessel to turn off the propeller while charging which limits the energy demand while charging. Various systems have been developed already. However, these are not standardized solutions but all one of a kind systems designed for a specific vessel or fleet. Which of these is the best solution is not easy to determine and strongly depends on the vessel characteristics and the operating environment. To supply the expected increasing demand for electric vessels, a guideline is developed which will help the engineer to find a suitable charging and mooring mechanism and to decrease the selection time for this system. The will provide Damen a strategic advantage towards other shipyards in vessel tenders since both the development costs and delivery time is lower. This guideline is developed based on the knowledge gained during a case study for a 81m Ropax ferry, sailing in the surroundings of Vancouver Island. For the case study an engineering design method was selected from literature and applied to this case, for which Damen had a hard time finding a charging and mooring mechanism. First thought was to combine both into one mechanism, but this is difficult due to conflicting functionalities of both systems. Due to the limited time available for the research, the design of the mooring mechanism is not taken into account for the case study. Setting the requirements for the charging mechanism is complex due to the range of different fields of interest that should be taken into account. However, the requirements of these various aspects are often related in some way to one another. This makes it easy to lose sight of the structure of all requirements. Comparing the functions that the charging mechanism should fulfill within these requirements and the existing charging mechanisms, it can be concluded that no suitable system is available yet. The gap between these is defined as a set of three functions; to compensate the tidal difference, deal with misalignments between the vessel and the shore and to provide flexibility for vessel motions. A new design was made which covers this gap. Additional research was done to ensure sufficient flexibility from the power cable, since this proved to be critical in the state of the art systems. From the knowledge gained during this case study, the guideline is developed. The guideline provides insight in the influential factors while selecting an mechanism. This should offer the engineer a structure to set the requirements and ensures that no aspect is left out of the requirements. An overview with the already existing mechanisms is provided which should be consulted multiple times during the process, to check whether a suitable systems exist, if the requirements should are too tight or if the project is not profitable at all. The structure of the requirements is designed such, that the relative easy requirements are set first. This prevents from doing demanding calculations or going on expensive business trips, while it could have been seen earlier that a project is not feasible or profitable at least. The guideline is validated while selecting a charging mechanism for a different type of vessel. This validation proved to decrease the selection time for a charging mechanism significantly compared to previous projects within Damen. After the test, a charging system was found which is preferred for the vessel. This charger is now further discussed with the supplier of the system.

Wind power is the fastest-growing energy source and the offshore wind industry is expected to grow by over 80 GW through 2024. There is a need to reduce all associated costs to be competitive in a market that might be fully subsidy-free soon. Adapting a predictive or condition-based maintenance strategy can help in reducing O&M costs, as it accounts for more than 30% of the lifetime costs in offshore turbines.This master thesis focuses on developing a novel gearbox condition monitoring technique using raw Supervisory Control And Data Acquisition (SCADA) data from an offshore wind farm. The developed approach attempts to leverage the use of physics of failure technique and artificial neural network models for continuous monitoring of gearbox condition. Utilizing SCADA data for monitoring and fault detection can help in eliminating retrofitting additional expensive sensors such as an online oil monitoring system, vibration monitoring systems and so on for the same purpose.Firstly, a physics of failure methodology is implemented to monitor turbines on a farm level. Using Failure Mode, Effects Analysis (FMEA), the operating regimes under which gears and bearings can potentially get damaged are ascertained. A correlation between the damage operating conditions and the root cause of failure is analyzed using boxplots. In particular, a correlation between operating conditions and, the unusual and unexplained White Etching Cracks or axial cracking failure that occur frequently in the high-speed shaft bearings is studied. Additionally, this methodology is also used to complement the Artificial Neural Network model developed for anomaly detection.Finally, an Artificial Neural Network (ANN) based on a Recurrent Neural Network (RNN) is developed for fault detection. The model is trained on data when the turbine was operating normally, to predict gear bearing and gearbox lubrication oil temperatures. A stacked Gated Recurrent Unit (GRU), a type of RNN model with two hidden layers resulted in predictions with the lowest mean squared error (0.14640퐶) and with good generalization. The difference/residual between the measured and ANN predicted temperatures are used to flag anomalies. The ANN-based condition monitoring method is validated through case studies using real data from wind turbines. The results from the case studies indicate that the RNNbased fault detection method can detect a failure in the wind turbine gearbox components as early as 3-6 months before it fails.

With the increasing focus on project planning in engineer-to-order(ETO) companies, tracking the progress of the design phase of a project is essential for effective planning. Such progress tracking currently is done through the regular feedback of discipline leads, which are intrinsically subjective. The information thus collected is then plotted in the form of so-called S-curves, to represent the progress over the course of the project. The present method tracks progress of the manufacturing engineering phase based on how much mass is designed with respect to the design weight of the equipment. This so-called mass curves are used and fitted to an S-curve and represent the tracked progress. It is shown that the fitted mass curves represent the progress of the engineering phase with a systematic average error of 25 days. Additionally, mass data retrieved from completed projects are used to predict the S-curves shape of the ongoing project. The weighted average of tracked and Predicted S-curves is then used in a Monte Carlo simulation in order to estimate the progress of the ongoing project. The method was found to have a tracking accuracy of 0:6 4%, which translates into an uncertainty on the project duration and therefore on the equipment delivery date, by 2 weeks. This uncertainty is found to be the upper bound of typical grace periods agreed with most clients. The present results might offer a new outlook on progress tracking on the progress tracking of manufacturing engineering activities. Further research shall be conducted to address the progress of earlier engineering phases equally.

To overcome the problem of wave-induced vessel motions on the crane tip, technologies have been developed to compensate for these motions. Most vessels nowadays, are equipped with dynamic positioning systems, these systems reduce the yaw, surge and sway movement of the vessel. This leaves, the motions roll, pitch and heave uncompensated. To reduce these motions, two main elements of motion compensation can be identified, consisting of heave compensation and anti load swing compensation. Existing technologies, like active and passive heave compensation tackle one of these elements. Other methods like the Stewart platform can compensate for both the heave motion and the load swing of the crane by stabilizing a platform on which the crane is mounted. In existing literature, not much work has been done to incorporate both the heave compensation and anti-swing control procedures in a combined control method. It would be much simpler if the crane could compensate the heave and payload swing by using only the crane's actuators. This thesis, studies the mechanical feasibility of a motion compensated knuckle boom crane, compensating for the wave-induced vessel motions by controlling the available actuators in such a manner, that the crane tip stays stationary. A typical knuckle boom crane has three actuated degrees of freedom, consisting of the slewing, boom luffing and jib luffing angle. To study such a system, a numerical model is developed that combines the multi body dynamics of the knuckle boom crane with models for the hydraulic actuation of the crane and incorporates the full six degree of freedom vessel motions. The actuated degrees of freedom are controlled using three separate proportional integral controllers. The desired trajectories for the controllers are calculated using the geometric relations of the crane, based on the assumption that the desired crane tip coordinate in the global axis system is known. Using the numerical model, insight is gained in the natural frequencies, forces/moments on the system, the necessary hydraulic properties and motion compensation performance. From the simulation results, it can be concluded that the cylinder forces and slewing torques increase when the motion compensation is turned on, compared to an uncompensated crane. Comparing the simulation results, to the Barge Master T40 crane, it can be concluded that cylinder forces, cylinder sizes, stroke velocities and power requirements are in line with requirements that can be achieved with existing technology. The main limitation, is expected to be the rated torque of the slewing motor, when the crane is positioned parallel to the vessel. In this position the main contributor to the motion compensation is the slewing motor. Using the proposed concept, motion compensation performance comparable to the existing Barge Master T40 is achieved. From the presented simulation scenarios, results indicate that the operational parameters and motion compensation performance of the system are feasible and competitive compared with existing technology.

In the construction industry, it is common to predict manufacturing times of structural elements based on the experience of shop managers. With the increasing use of Building Information Models (BIM) and data analysis in manufacturing processes an opportunity for improving the accuracy of predicted manufacturing times arises. This research proposes a general prediction model based on physical properties of structural elements extracted from BIM, along with manufacturing times of manufactured elements. The proposed Support Vector Regression Model Tree (SVRMT) is tested in both hypothetical and real case scenarios. Through validation in real case scenarios, the SVRMT prediction model turned out to be a significant improvement in terms of prediction accuracy, compared to the current experience based approach.

Globalization is heaving its impact on many field. For the field of warehousing this development, in combination with the actual shortage of labor, means that many warehouse owners are forced to reduce their warehouse costs in order to stay competitive with warehouses in low-wage countries. On the other side the warehouse owners are pulled by recent technical innovations, which have reduced the drawbacks of automation. One of these recent innovations, is the mobile fulfillment unit-to-unit order picking system, which is presented in this paper. To make this system more affordable and hence to increase the competitiveness of warehouses in western Europe, research is required optimizing each of the system parts. This research focuses on the order processing part of the system, which has changed considerably compared to existing mobile fulfillment order picking systems. In this system units are brought to two sides of a stationary order picker, who then transfers products from one unit to another unit. The order processing problem covers the sequencing of the unit visits at the order picking station, the batching of these units and the determination of the products that should be transferred. Using insights from literature, several approaches are proposed to each of the problem parts. Each of these approaches is then tested and validated. Combining the approaches for each problem part leads to solutions addressing the full problem. All these solutions are tested against each other using a data set of one day of an existing warehouse. The tests are executed for multiple different order picking station configuration and for multiple data set sizes. This leads to an overview of the effectiveness of each of these solutions in terms of computational time and the reduced number of AGV visits. From the results several conclusions can be drawn concerning the optimal solution for a specific warehouse. For an example warehouse in the Netherlands, a significant reduction of 25% can be obtained, regarding the number of visits, compared to the baseline approach. Which means the required number of AGVs can be lower, the investment costs for this system can be reduced and hence the competitiveness for this warehouse can be increased by implementing one of solutions presented in this paper.

Fatigue assessment of offshore structures has always been an important area of study due to a large number of cyclic loading acting on the structure. Traditionally, offshore structures are simulated in time-dependent dynamic analysis to calculate the stress response at critical locations of the structure. Sorting of relevant stress cycles is done using a suitable cycle counting algorithm (usually rainflow counting) and then an appropriate S-N curve and Miner’s cumulative rule are used to estimate the total fatigue damage at these critical locations. Offshore structures are usually designed for a minimum fatigue life of 20 years, which takes a lot of computational time in FEM. If loads are converted to an equivalent frequency domain and the structure is analyzed in frequency dependent dynamic analysis, computational time can be reduced. This will help engineers perform faster optimizations on new structural developments. For frequency analysis, using Dirlik’s semi-empirical method, a good estimation of fatigue damage are achieved according to literature. Application of Dirlik’s method on various structures has been validated by comparing the damage values with equivalent rainflow counting method. Unlike rainflow counting algorithm, Dirlik’s method calculates probability density function of the stress ranges with empirical formulae and uses S-N curve and Miner’s rule to estimate total fatigue damage. Dirlik’s method is easy to understand, easy to program and estimate fatigue damage with good accuracy. This might also help us in calculating fatigue damage in the stinger, due to bow deflection. To fully understand the method of dynamic frequency analysis with Dirlik’s method, the objective of the research is to study its feasibility on simple models by conducting simulations in FEM and to establish the fatigue calculation procedure. Two models are selected in this research, a cantilever beam and a simple frame model (for tubular joints). Simulation on both the models are conducted in frequency analysis and fatigue estimation is done using Dirlik’s method. To verify the estimated damage values, equivalent time-dependent analyses are also conducted with rainflow counting method. Comparable fatigue damage results are achieved for cantilever beam but, for frame model, results obtained could not be compared due to issue found by conducting detailed analysis. Although, the overall objective of the research is not fully complete, results and observations found in this research will be helpful for conducting additional simulations with different strategies to verify the frame model. With this research, a firm basis is developed which could motivate the company to further investigate the method.

Floating offshore wind turbines offer opportunities to harvest wind energy at deep-water locations, where the construction of fixed-base turbines is infeasible. The dynamic power cables, which interconnect turbines and transport the generated electricity, are under large dynamic stresses due to the environmental loads and the motion of the floating platform. Limited knowledge about the structural behaviour of these cables is available, which is why there is need for new analysis and design methods. This MSc thesis presents a method for the preliminary design optimization of the dynamic power cable configuration. A parametric model of a dynamic power cable is built in the commercial software package OrcaFlex, from which motions, loads and fatigue on the cable can be calculated. Following that, a radial basis function model-based optimization algorithm is applied to find the optimal cable configuration for an arbitrary environmental scenario. The key performance indicator here is fatigue damage on the copper conductor, which is expected to be critical due to the cyclic loading on the cable and the poor mechanical properties of copper. Experiments are carried out to test the optimization model’s validity in terms of convergence, robustness and efficiency. The final method is capable of consistently finding a near-optimal dynamic power cable configuration design within reasonable time. Additionally, findings are presented about the fatigue behaviour of the DPC, what causes the fatigue damage and how to mitigate the effects.

Industrial electric motors are at the heart of almost every industry. They are a 47 billion USD market in 2020 and consume 70% of all industrial electricity. They are generally paired with a gearbox and load, which is referred to as an electric gearmotor system. Being so essential means that it is important to avoid failures, 98% of 300 researched companies by ITIC reported a cost of 100.000 USD every hour of downtime. To detect failures a technology called fault detection and diagnosis (FDD) is used, which is a method to foresee failures or faults in a system that deteriorates over time through evaluating the state of the system. It is an extensively academically research subject, however, has hardly been adopted in industrial settings where electric gearmotor systems are applied. Thus, a FDD model was developed to provide insight, knowledge, and a practical example into the necessities of an industrial FDD model. This was achieved through conducting an analysis on the state-of-the-art of FDD in industrial settings and conducting a literature review on FDD. Based on an analysis of the conclusions a hybrid diagnostics model was developed. For the fault detection a model-based solution was used, it compared the predicted torque to the measured torque of a motor to create a health indication value. If this value crosses a pre-determined threshold an alarm would go off. For fault identification a decision tree machine learning algorithm is used to identify: blockage, bearing, gear or random failure in a system. To verify and validate the hybrid diagnostics model it was applied to a client of SEW Eurodrive where data was available of a known system. The system had a fault detection accuracy as high as 94% and could classify failures with an accuracy of 93%.

An unfamiliar subject to the contemporary connecting options for cranes on pontoons is removability; Various difficulties and obstructions related to the heavy-duty nature of the equipment lead to a limited amount of practiced conventional connecting options for this purpose, which all have the absence of removability in common. Furthermore, the consideration of various types of efficiencies and performance aspects has not been common practice within this field. The aim of developing a removable and efficient crane-to-pontoon connection system is therefore set. An initial literature research is performed in order to obtain a variety of connecting options which have the potential of forming the basis of a new removable connection system, optimized for crane-to-pontoon configurations. Subsequently, creating a unique rating system, specifically for crane-to-pontoon connection systems, led to a substantiated selection process for the most feasible option among the potential connecting options. The turnbuckle option obtained the highest ranking and was therefore selected to proceed the design process with. Developing the turnbuckle option into a complete connection system and accomplishing all defined aims led to an encounter with various engineering challenges. An integral design process led to the discovery of a proficient combination of components, which overcome the challenges and provide satisfaction with respect to the aims of the project. The parameters of the developed conceptual design are finally quantified in order to prove feasibility and efficiency. Applicable design parameters are found which pass the safety requirements, while minimizing the material consumption. With these parameters, the removable design is compared to conventional real case connection systems in terms of cost-efficiency, which resulted in the observation that multiple millions of euros in long-term savings are anticipated per deployed crane due to the removability feature.

In contrast to traditional power cables for bottom-founded offshore wind turbines, power cables for floating wind turbines penetrate the water column and are exposed to cyclic loading. Due to the dynamic nature of the cable loading, the cables are prone to fatigue failure. Since the evaluation of the fatigue life of complex structures, like power cables, has to deal with a certain degree of uncertainty, fatigue safety factors are introduced. These factors ensure a desired probability of failure based on the degree of uncertainty present in the modeling of the fatigue life. Limited experience in the evaluation of the fatigue life of dynamic power cables is found in the literature, and no sources have been found attempting to calibrate the prescribed fatigue safety factor. Currently, a fatigue safety factor of 10 is advised. This implies that there is much room for reduction in the uncertainties, meaning that there is a potential for making the cables cheaper and more reliable, which will in turn make floating wind energy more competitive with other (renewable) energy sources. Due to the lack of available literature, comparisons with umbilicals and flexible risers are made. Different methods for the evaluation of fatigue safety factors for flexible risers are evaluated, and judged on how applicable they are to use on dynamic power cables. It is found that a reliability based approach is most suitable for this purpose. A case study is carried out for a presently relevant scenario to put the proposed method into practice. It is concluded that for a safety class corresponding to a required maximum probability of failure of 10-3 in the last operational year, a fatigue safety factor of 3.5 is needed. This safety factor is required for the wave-load induced fatigue, as opposed to the seabed induced fatigue, to which the dynamic power cable is less vulnerable nearby the touch-down zone.  The main parameter driving the uncertainty in the fatigue analysis is the sensitivity of the local stress analysis, which is in line with what has been found for similar studies for the oil & gas industry. In order to bring down the cost of dynamic power cables, and make them more reliable, more accurate local stress analysis models need to be developed, being validated against test data, in order to reduce the standard deviation of the local stress computation.

Fatigue lifetime has proven to be a leading design parameter for naval vessels. In the field of fatigue analysis and design of welded joints, two overall methods are distinguished: the temporal and spectral approach. Using empirical models, the spectral approach is typically preferred due to its efficiency, even though damage estimates are conservative. With the temporal approach, nonlinear effects can be captured, providing higher accuracy at the cost of additional computation time. Within this framework, an improvement of the spectral approach was pursued, focusing on incorporating the mean stress effect. Past efforts to include mean stress corrections were continued by focusing on applying the Walker correction. Nonlinear effects on the mean stress response were investigated and were found to be quite small for the case of a pontoon vessel. This enabled the use of the still water bending moment as a single input to the spectral mean stress model. By using Walker in the spectral mean stress correction, an overall reduction of conservatism of 21% was achieved. Future research should focus on testing new wave cases, applying additional fatigue models and investigating the effects for hull shapes of naval vessels.