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dc.contributor.advisorSkjetne, Roger
dc.contributor.advisorLarsen, Kjell
dc.contributor.authorUeland, Einar Skiftestad
dc.date.accessioned2021-09-22T07:57:21Z
dc.date.available2021-09-22T07:57:21Z
dc.date.issued2021
dc.identifier.isbn978-82-326-6727-7
dc.identifier.issn2703-8084
dc.identifier.urihttps://hdl.handle.net/11250/2780240
dc.description.abstractReal-time hybrid model testing (ReaTHM testing) is a method for emulating ocean structures that combines numerical methods with traditional hydrodynamic model testing. This is done by partitioning the ocean structure under consideration into numerical and physical substructures that are coupled in real-time through measurement and control interfaces, for high fidelity emulation of the original ocean structure. The method can be classified as an extension of traditional hydrodynamic model testing since it considers experimental testing of down-scaled models in basin laboratories, and as a subset of hybrid testing since it replaces parts of the down-scaled structure with numerical simulated models. The developments presented in this thesis is aimed at ReaTHM testing where the numerically computed load vector is calculated based on measurements of the experimental displacements and thereby actuated onto the physical substructure via a configuration of distributed cabled winches. The experimental platform, together with the actuators, thus constitutes a cable-driven parallel robot. This PhD project’s overall goal is to further improve the ReaTHM testing methodology as part of a research effort to make it a well documented, accepted, and valued practise that accurately identifies and predicts the behaviour of ocean structures in realistic marine environments. One of the major challenges in this regard is to ensure that load actuation is performed with minimal errors and without significant degradation of emulation performance. To this end, the focus of this work is to identify and mitigate issues associated with the actuation of the numerically calculated load vector onto the experimental test platform and to enable more accurate and robust load control. The thesis is organised as a collection of articles. The two conference articles identify and quantify sources of error in load actuation. They serve as the basis for the subsequent journal articles that address specific load actuation challenges and associated good practise control methods. In the first journal article, novel methods for determining each actuator’s appropriate target cable forces are proposed. These methods guarantee continuous differentiability of the resulting cable forces. The article also shows that an implementation of Newton’s method specialised for the resulting optimisation problem can be used for practical real-time applications. The results are beneficial for ReaTHM testing because of the method’s flexibility, and because it is expected that smoother cable force trajectories can be more accurately tracked. The second journal article proposes a procedure for optimal actuator placement that is particularly suitable for ReaTHM testing, for which no such guidelines exist at the time of writing. The third and final journal article demonstrates how position-controlled servo- motors connected to drums via clocksprings can be used for accurate actuator force control. Associated controllers that compensate for both delays and motion-induced forces are proposed. The study emphasises developments for ReaTHM testing by focusing on relevant use cases, force magnitudes, and frequency ranges. For development, problem identification, method validation, and demonstration, the work in this thesis is emphasised by extensive experimental testing. Experiments are presented using both a readily accessible 1 degree of freedom setup for basic testing and development and a more complex ReaTHM test setup of a moored barge in a basin laboratory in which the cabled winches are tasked with actuating loads in three degrees of freedom (surge, sway and yaw). The thesis does not use ReaTHM testing to determine realistic ocean structures’ behaviour, which is the intended end-use of the overall methodology. Instead, simpler test cases are considered to understand, develop, and improve control functions at a more fundamental level.en_US
dc.language.isoengen_US
dc.publisherNTNUen_US
dc.relation.ispartofseriesDoctoral theses at NTNU;2021:284
dc.relation.haspartArticle 1: Ueland, Einar Skiftestad; Skjetne, Roger. Effect of Time Delays and Sampling in Force Actuated Real-Time Hybrid Testing; A Case Study. I: OCEANS 2017 MTS/IEEE Anchorage. https://ieeexplore.ieee.org/document/8232196en_US
dc.relation.haspartArticle 2: Ueland, Einar Skiftestad; Skjetne, Roger; Vilsen, Stefan Arenfeldt. Force actuated real-tme hybrid model testing of a moored vessel: A case study investigating force errors. IFAC-PapersOnLine 2018 ;Volum 51.(29) s. 74-79 https://doi.org/10.1016/j.ifacol.2018.09.472en_US
dc.relation.haspartArticle 3: Ueland, Einar Skiftestad; Sauder, Thomas Michel; Skjetne, Roger. Optimal Force Allocation for Overconstrained Cable-Driven Parallel Robots: Continuously Differentiable Solutions With Assessment of Computational Efficiency. IEEE Transactions on Robotics https://doi.org/10.1109/TRO.2020.3020747en_US
dc.relation.haspartArticle 4: Ueland, Einar Skiftestad; Sauder, Thomas Michel; Skjetne, Roger. Optimal Actuator Placement for Real-Time Hybrid Model Testing Using Cable-Driven Parallel Robots. Journal of Marine Science and Engineering 2021 ;Volum 9.(2) https://doi.org/10.3390/jmse9020191 This is an open access article distributed under the Creative Commons Attribution License (CC BY 4.0)en_US
dc.relation.haspartArticle 5: Ueland, Einar Skiftestad; Sauder, Thomas Michel; Skjetne, Roger. Force Tracking Using Actuated Winches with Position-Controlled Motors for Use in Hydrodynamical Model Testing. IEEE Access 2021 ;Volum 9. s. 1-16en_US
dc.titleLoad Control for Real-time Hybrid Model Testing using Cable-Driven Parallel Robotsen_US
dc.typeDoctoral thesisen_US
dc.subject.nsiVDP::Technology: 500::Marine technology: 580en_US


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