Michael Rygaard Hansen

• Losada-Floriano, Diego; Thygesen, Elin; Sanfilippo, Filippo; Hansen, Michael Rygaard & Fossum, Mariann (2026). Service Robots as Work Support for Health Personnel in Long-Term Care: Protocol for a Scoping Review. JMIR Research Protocols. 15, s. 89435–89435. doi: 10.2196/89435. Fulltekst i vitenarkiv Vis sammendrag

  Background Demographic shifts are increasing the global demand for long-term care services, coinciding with a worldwide shortage of health care personnel. Service robots, designed to perform tasks in both professional and personal use, are perceived as a potential solution to alleviate health care personnel’s workload and enhance the quality of care. However, the existing literature is fragmented and heterogeneous, with a limited emphasis on the role of service robots in supporting residents rather than health care personnel. Furthermore, there is a lack of consistent definitions of service robotic technologies and a scarcity of studies on implementation models and frameworks. Objective This scoping review aims to map and synthesize evidence regarding the implementation of service robots as work support for health care personnel in long-term care settings. Methods A comprehensive 3-step search will be conducted in Embase, MEDLINE, APA PsycInfo, CENTRAL, Scopus, and CINAHL, along with gray literature databases and institutional repositories. Eligible sources encompass empirical studies and gray literature involving service robots, health care personnel, residents aged 65 years or older, and stakeholders such as informal caregivers within institutional long-term care. Exclusions apply to studies on home care, medical or industrial robots, and nonrobotic technologies. Data will be extracted and analyzed using the Joanna Briggs Institute methodology, with findings presented in tables, diagrams, and narrative summaries to identify gaps and inform future research and implementation strategies. Results The project has been funded for a 4-year period starting in April 2025. This protocol was developed in October 2025 and subsequently registered in November 2025. A comprehensive search strategy was formulated and completely conducted on October 24, 2025. The screening of 4884 titles and abstracts was completed in December 2025, resulting in the retrieval of 64 (1.3%) full-text articles for eligibility assessment. Subsequent phases, including data extraction, analysis, evidence synthesis, and presentation of results, will be conducted sequentially. The scoping review is expected to be finalized by June 2026. Conclusions This scoping review is expected to delineate the extent and characteristics of the existing evidence on service robots as work support for health personnel in long-term care settings. It will highlight the key reported outcomes and challenges encountered in implementation studies, as well as the theoretical frameworks, models, and concepts applied to address these issues. Trial Registration Open Science Framework QWK58; https://osf.io/qwk58/ International Registered Report Identifier (IRRID) PRR1-10.2196/89435

• Fossum, Mariann; Sanfilippo, Filippo; Hansen, Michael Rygaard; Enerstvedt, Camilla & Thygesen, Elin (2026). Exploring the Role of Robotics in Nursing Homes: Insights from Healthcare Professionals - PubMed. Studies in Health Technology and Informatics. ISSN 0926-9630. doi: 10.3233/SHTI260712. Fulltekst i vitenarkiv Vis sammendrag

  This paper reports findings from a qualitative descriptive study exploring the potential use of service robots in nursing homes. Participants in three workshops expressed optimism and creativity regarding the role of robots in supporting a variety of tasks, including housekeeping, transportation, mo …

• Gøytil, Petter Hansen; Hansen, Michael Rygaard & Tvilde, Håkon Almelid (2025). Effective Bulk Modulus in Low-Pressure Pump-Controlled Hydraulic Cylinders. Actuators. 14(8). doi: 10.3390/act14080366. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, the effective bulk modulus of pump-controlled hydraulic cylinders is studied in the context of linear time-invariant modeling and control. Using an experimental test-rig, the minimum expected value of the effective bulk modulus is identified, and its impact on stability and achievable performance under feedback control is analyzed. A method for control design and analysis based on a single operating point, analogous to that of what is traditionally utilized in valve-controlled systems, is proposed and validated. It is shown that despite the drastic reduction in the minimum effective bulk modulus occurring in these systems compared to that of valve-controlled cylinders, adequate performance may be achieved under feedback control due to the presence of adequate damping. Two critical modeling aspects commonly neglected in the research literature on these systems are highlighted, and their importance is demonstrated. These results demonstrate the efficacy of linear time-invariant methods in pump-controlled cylinders, as well as the importance of making appropriate modeling decisions, and should therefore be of high relevance to both researchers and engineers working with pump-controlled cylinders.

• Sanfilippo, Filippo; Fossum, Mariann & Hansen, Michael Rygaard (2025). Redefining Care and Work Practices: The Role of Autonomy in the Future of Nursing Homes. I Paolis, Lucio Tommaso De; Arpaia, Pasquale & Sacco, Marco (Red.), Extended Reality. Springer. ISSN 9783031977817. s. 355–370. doi: 10.1007/978-3-031-97781-7_26. Fulltekst i vitenarkiv Vis sammendrag

  Nursing homes face increasing challenges due to workforce shortages, ageing populations, and rising care demands. This paper explores the dynamics of human-robot interaction (HRI) in nursing home environments, focusing on how autonomous robots engage with nurses and residents in nursing homes. We examine the role of trust-building and emotional engagement in caregiving scenarios, where patient well-being depends on effective HRI. The potential for autonomous systems to support decision-making while maintaining human oversight is investigated. Using the Autonomy Levels for Unmanned Systems (ALFUS) framework, we assess care robots’ autonomy in terms of mission complexity (MC), environmental complexity (EC), and external system independence (ESI). Additionally, the Autonomy and Technology Readiness Assessment (ATRA) method supports gradual capability enhancement, providing a roadmap to higher autonomy while ensuring safety and reliability. Based on this established methodology, we introduce the Nursing Home Interaction Framework (NHIF), a novel conceptual framework defining the roles of actors involved, to connect theoretical insights with real-world applications. This work highlights the significance of human-robot trust in elderly care scenarios and proposes directions for future research on collaborative decision-making in nursing home HRI.

• Zhao, Wei; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard & Andersen, Torben Ole (2025). Experimental assessment of energy consumption: a comparative study between motor-controlled and valve-controlled cylinders in knuckle boom crane operations. Frontiers in Mechanical Engineering. 11, s. 1–11. doi: 10.3389/fmech.2025.1535120. Fulltekst i vitenarkiv Vis sammendrag

  This paper experimentally assess the energy consumption of a laboratory knuckle boom crane utilizing two proposed two-motor-two-pump (2M2P) motor-controlled hydraulic cylinders (MCC) in comparison to two conventional valve-controlled hydraulic cylinders (VCC). Experimental results demonstrate that using the motor-controlled crane instead of the valve-controlled crane results in 60%–64% total energy savings. In conclusion, this study highlights the practical suitability of the 2M2P MCCs for real-world applications, showcasing their enhanced energy efficiency compared to conventional VCCs.

• Hagen, Daniel; Hansen, Katrine Als; Holmen, Jonas & Hansen, Michael Rygaard (2025). Real-Time Simulation-Based Control of an Electro-Hydraulic Flexible Manipulator. Actuators. 14(2). doi: 10.3390/act14020080. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents the modeling and control of a flexible single-boom crane manipulator using a high-fidelity real-time simulation model. The model incorporates both electro-hydraulic actuation and flexible-body dynamics, with the flexible boom represented via the lumped parameter method. A systematic tuning and validation procedure ensures that the model accurately replicates the physical system’s dynamics, achieving an eigenfrequency accuracy of approximately 97% and a piston-position deviation within 1.2% of the overall stroke length in final tests. The real-time simulation model is utilized in both open-loop and closed-loop control schemes to investigate whether simulated data can reduce dependency on sensor feedback compared to a benchmark controller. While the simulation-based controller alone does not match the fully sensor-based closed-loop accuracy, the simulation-based feedforward improves performance by 83% compared to the standard model-based velocity feedforward. Additionally, integrating the real-time simulation with sensor feedback enhances the benchmark controller’s performance by approximately 16%. These findings highlight the potential of combining real-time, nonlinear simulation with conventional sensor feedback to enhance the control of electro-hydraulic flexible manipulators.

• Sanfilippo, Filippo; Fossum, Mariann & Hansen, Michael Rygaard (2025). Redefining Care and Work Practices: The Role of Autonomy in the Future of Nursing Homes. I Paolis, Lucio Tommaso De; Arpaia, Pasquale & Sacco, Marco (Red.), Extended Reality. Springer. ISSN 9783031977718. s. 355–370. doi: 10.1007/978-3-031-97781-7_26. Fulltekst i vitenarkiv Vis sammendrag

  Nursing homes face increasing challenges due to workforce shortages, ageing populations, and rising care demands. This paper explores the dynamics of human-robot interaction (HRI) in nursing home environments, focusing on how autonomous robots engage with nurses and residents in nursing homes. We examine the role of trust-building and emotional engagement in caregiving scenarios, where patient well-being depends on effective HRI. The potential for autonomous systems to support decision-making while maintaining human oversight is investigated. Using the Autonomy Levels for Unmanned Systems (ALFUS) framework, we assess care robots’ autonomy in terms of mission complexity (MC), environmental complexity (EC), and external system independence (ESI). Additionally, the Autonomy and Technology Readiness Assessment (ATRA) method supports gradual capability enhancement, providing a roadmap to higher autonomy while ensuring safety and reliability. Based on this established methodology, we introduce the Nursing Home Interaction Framework (NHIF), a novel conceptual framework defining the roles of actors involved, to connect theoretical insights with real-world applications. This work highlights the significance of human-robot trust in elderly care scenarios and proposes directions for future research on collaborative decision-making in nursing home HRI.

• Zhao, Wei; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard & Andersen, Torben Ole (2024). Experimental Verification of a Two-Motor-Two-Pump Motor-Controlled Hydraulic Cylinder with Throttle-Free Passive Load-Holding Capability in Four-Quadrant Operations. Actuators. 13(9). doi: 10.3390/act13090372. Fulltekst i vitenarkiv Vis sammendrag

  Among various motor-controlled hydraulic cylinder (MCC) topologies, the two-motor-two-pump (2M2P) MCC distinguishes itself through several notable advantages, including precise cylinder pressure control and eliminating mode switch oscillations. Nevertheless, there are challenges remaining in fully realizing its operations across four quadrants and establishing an effective load-holding function within these operations. This study bridges this gap by implementing a 2M2P MCC prototype on a laboratory knuckle boom crane, enabling operation across all four quadrants. Experimental results indicate that position tracking errors remain within ±2.5 mm across three cases, which is well below 1% of the total cylinder travels in the experiments. Furthermore, smooth intersection of cylinder-bore-side and rod-side pressures is observed during transitions between quadrants. In conclusion, the proposed 2M2P MCC demonstrates seamless operation throughout all quadrants, with the load-holding function smoothly activating and deactivating in all four quadrants.

• Zhao, Wei; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard & Andersen, Torben Ole (2024). Mitigating Mode Switching Oscillation in a One-Motor-One-Pump Motor-Controlled Hydraulic Cylinder via System Pressure Control: Simulation Study. Energies. 17(24). doi: 10.3390/en17246334. Fulltekst i vitenarkiv Vis sammendrag

  This study focuses on a hydraulic cylinder that is directly connected to a fixed-displacement hydraulic pump driven by an electric servo motor. This particular setup is referred to as a one-motor-one-pump motor-controlled hydraulic cylinder (MCC). This paper presents a new approach to address mode switching oscillation (MSO) in MCCs by incorporating system pressure control capabilities. It conducts a detailed investigation into the factors that contribute to MSO in standard MCCs and thoroughly evaluates the effectiveness of the proposed system in mitigating MSO. The simulation results demonstrate the successful suppression of MSO. In conclusion, the proposed MCC with system pressure control capabilities is validated and, furthermore, it shows great potential for practical applications involving small loads and rapid retraction.

• Zhao, Wei; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard & Andersen, Torben Ole (2024). Enabling Passive Load-Holding Function and System Pressures Control in a One-Motor-One-Pump Motor-Controlled Hydraulic Cylinder: Simulation Study. Energies. 17(11). doi: 10.3390/en17112484. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with a hydraulic cylinder directly controlled by a variable speed motor-driven fixed-displacement pump. The considered configuration is referred to as a one-motor-one-pump (1M1P) motor-controlled hydraulic cylinder (MCC). A 1M1P MCC with a hydraulically driven passive load-holding function enabled by controlled system pressures is proposed. The proposed load-holding functionality works if there is a standstill command, a loss of power supply, or a hose rupture. Additionally, this paper conducts a comprehensive analysis of the proposed system’s operation and load-holding function across four quadrants. The simulation results demonstrate four-quadrant operation and good load-holding performance under the aforementioned scenarios. In conclusion, the proposed 1M1P MCC can be successfully used on practical applications characterized by overrunning loads and four quadrant operation.

• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2022). Online Deflection Compensation of a Flexible Hydraulic Loader Crane Using Neural Networks and Pressure Feedback. Robotics. 11(2). doi: 10.3390/robotics11020034. Fulltekst i vitenarkiv Vis sammendrag

  The deflection compensation of a hydraulically actuated loader crane is presented. Measurement data from the laboratory are used to design a neural network deflection estimator. Kinematic expressions are derived and used with the deflection estimator in a feedforward topology to compensate for the static deflection. A dynamic deflection compensator is implemented, using pressure feedback and an adaptive bandpass filter. Simulations are conducted to verify the performance of the control system. Experimental results showcase the effectiveness of both the static and dynamic deflection compensator while running closed-loop motion control, with a 90% decrease in static deflection.

• Gøytil, Petter Hansen; Padovani, Damiano & Hansen, Michael Rygaard (2022). Linear Time-Invariant Modelling of Electrohydraulic Cylinders. I -, IEEE (Red.), IEEE 2022 3rd International Conference on Electrical, Computer, Communications and Mechatronics Engineering (ICECCME). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781665470957. doi: 10.1109/ICECCME55909.2022.9988490. Fulltekst i vitenarkiv
• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2021). Novel Concept for Electro-Hydrostatic Actuators for Motion Control of Hydraulic Manipulators. Energies. 14(20). doi: 10.3390/en14206566. Fulltekst i vitenarkiv Vis sammendrag

  Abstract: Self-contained hydraulic cylinders have gained popularity in the recent years but have not been implemented for high power articulated hydraulic manipulators. This paper presents a novel concept for an electro-hydrostatic actuator applicable to large hydraulic manipulators. The actuator is designed and analyzed to comply with requirements such as load holding, overload handling, and differential flow compensation. The system is analyzed during four quadrant operation to investigate energy efficiency and regenerative capabilities. Numerical simulation is carried out using path control and 2DOF anti-swing of a hydraulic crane as a load case to illustrate a real world scenario. A comparison with traditional valve-controlled actuators is conducted, showing significantly improved efficiency and with similar dynamic response, as well as the possibility for regenerating energy.

• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2021). Anti-swing control of a hydraulic loader crane with a hanging load. Mechatronics (Oxford). ISSN 0957-4158. 77. doi: 10.1016/j.mechatronics.2021.102599. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to create the 2-DOF anti-swing controller. The anti-swing controller is added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angle during motion. Experiments are carried out to verify the performance of the anti-swing controller, showing good suppression of the payload angle in practice.

• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2021). Development of 3D anti-Swing control for hydraulic knuckle boom crane. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 42(3), s. 113–129. doi: 10.4173/mic.2021.3.2. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, 3D anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to model the system and create the 3D anti-swing controller. The anti-swing controller generates a set of tool point velocities which are added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angles during motion using the proposed anti-swing controller in addition to pressure feedback. Experiments are carried out to verify the performance of the anti-swing controller. Results show that the implemented pressure feedback is crucial for reaching stability, and with it the control system yields good suppression of the swing angles in practice.

• Moslått, Geir-Arne; Padovani, Damiano & Hansen, Michael Rygaard (2020). A Digital Twin for Lift Planning with Offshore Heave Compensated Cranes. Journal of Offshore Mechanics and Arctic Engineering. ISSN 0892-7219. 143(3). doi: 10.1115/1.4048881. Fulltekst i vitenarkiv
• Husveg, Rune; Husveg, Trygve; Teeffelen, Teeffelen van; Ottestad, Morten & Hansen, Michael Rygaard (2020). Variable step size p&o algorithms for coalescing pump/deoiling hydrocyclone produced water treatment system. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 41(1), s. 13–27. doi: 10.4173/MIC.2020.1.2. Fulltekst i vitenarkiv
• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2020). Development of Point-to-Point Path Control in Actuator Space for Hydraulic Knuckle Boom Crane. Actuators. 9(2). doi: 10.3390/act9020027. Fulltekst i vitenarkiv
• Jakobsen, Jannik Hartwig & Hansen, Michael Rygaard (2020). Steady state counterbalance valve modeling with the inuence of synthetic ester oils using CFD. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 41(2), s. 51–64. doi: 10.4173/MIC.2020.2.2. Fulltekst i vitenarkiv Vis sammendrag

  This study looks in details at the effects of synthetic esters being applied to a counterbalance valve from the perspective of a system engineer. There is limited literature on the subject of applied synthetic esters and as such limited unbiased sources for information. This creates reluctance against the use of these fluids in sectors and regions with no prior experience and knowledge of what to expect. This study expands the applied literature by investigating a commercially available valve using commercial oils, a basic synthetic ester, a fully saturated synthetic ester and a typical mineral oil type for benchmarking. The investigation is based on both computational fluid dynamics and experiments and is performed at 20, 40 and 60 deg. The product is a steady-state valve model including fluid dynamics and a parameter-dependent Coulomb friction. The CFD model reveals minimal oil type dependence in the resulting fluid dynamics model with flow forces and discharge coefficient being the same for mineral oil and esters. The experiments show that the esters primarily produce different levels of hysteresis with up to 40% less and 15% more hysteresis. The friction investigation showed that the relationship between hysteresis and pilot pressure was different for all oil types, and that the relationship between hysteresis and temperature was similar for all oil types. With full knowledge of mineral oil and the oil specific knowledge of the hysteresis and pilot pressure relationship at a single temperature, ester hysteresis was predicted with better than 88% accuracy across the three temperatures.

• Jakobsen, Jannik Hartwig & Hansen, Michael Rygaard (2020). CFD assisted steady-state modelling of restrictive counterbalance valves. International Journal of Fluid Power. ISSN 1439-9776. 21(1), s. 119–146. doi: 10.13052/ijfp1439-9776.2115. Fulltekst i vitenarkiv
• Gøytil, Petter Hansen; Padovani, Damiano & Hansen, Michael Rygaard (2020). A Novel Solution for the Elimination of Mode Switching in Pump-Controlled Single-Rod Cylinders. Actuators. 9(1). doi: 10.3390/act9010020. Fulltekst i vitenarkiv Vis sammendrag

  This paper concerns the stability issue of pump-controlled single-rod cylinders, known as mode switching. First, a review of the topic is provided. Thereafter, the most recently proposed solution for the elimination of mode switching is investigated and shown to result in unstable behavior under certain operating conditions. A theoretical analysis is provided demonstrating the underlying mechanisms of this behavior. Based on the analysis, a novel control strategy is proposed and investigated numerically. Proper operation and stability are demonstrated for a wide range of operating conditions, including situations under which the most recently proposed solution results in unstable behavior and loss of control over the actuator.

• Moslått, Geir-Arne & Hansen, Michael Rygaard (2020). Practice for determining friction in hydraulic winch systems. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 41(2), s. 109–120. doi: 10.4173/MIC.2020.2.6. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a method for estimating friction in hydraulic active heave compensated (AHC) offshore winches. The method is a two-step approach where the first step is to model the friction loss in the hydraulic motors based on data from the sub-supplier. The second step requires real-life testing, where the remaining friction losses in the winch system is identified and modeled. In this context, a practice is characterized by obtaining a friction loss estimation with the highest possible accuracy over the widest possible range of operating conditions with a limited amount of experimental work. The method benefits from the use of parametric models, sub-supplier data, and real-life measurements on a 150 t AHC crane from National Oilwell Varco Norway (NOVN). The work is an important part of developing a simulation model that can be used actively in virtual testing and verification of crane operations at NOVN. A friction loss model developed from the proposed method was implemented in a NOVN simulation model. Computed and measured hydraulic pressures showed deviations of less than 10% from measured results for a 150 t crane operating in AHC.

• Moslått, Geir-Arne; Hansen, Michael Rygaard & Padovani, Damiano (2020). Performance improvement of a hydraulic active/passive heave compensation winch using semi secondary motor control: Experimental and numerical verification. Energies. 13(10). doi: 10.3390/en13102671. Fulltekst i vitenarkiv
• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2020). Adaptive Feedforward Control of a Pressure Compensated Differential Cylinder. Applied Sciences. 10(21). doi: 10.3390/app10217847. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents the design, simulation and experimental verification of adaptive feedforward motion control for a hydraulic differential cylinder. The proposed solution is implemented on a hydraulic loader crane. Based on common adaptation methods, a typical electro-hydraulic motion control system has been extended with a novel adaptive feedforward controller that has two separate feedforward states, i.e, one for each direction of motion. Simulations show convergence of the feedforward states, as well as 23% reduction in root mean square (RMS) cylinder position error compared to a fixed gain feedforward controller. The experiments show an even more pronounced advantage of the proposed controller, with an 80% reduction in RMS cylinder position error, and that the separate feedforward states are able to adapt to model uncertainties in both directions of motion.

• Husveg, Rune; Husveg, Trygve; Teeffelen, Niels van; Ottestad, Morten & Hansen, Michael Rygaard (2019). Automatic operation and control of a novel coalescing centrifugal pump for improved oil/water separation. SPE Production & Operations. ISSN 1930-1855. 34(3), s. 508–519. doi: 10.2118/195591-PA. Fulltekst i vitenarkiv
• Moslått, Geir-Arne; Padovani, Damiano & Hansen, Michael Rygaard (2019). A Control Algorithm for Active/Passive Hydraulic Winches Used in Active Heave Compensation, ASME/BATH 2019 Symposium on Fluid Power and Motion Control. The American Society of Mechanical Engineers (ASME). ISSN 9780791859339. doi: 10.1115/FPMC2019-1710. Fulltekst i vitenarkiv
• Gøytil, Petter Hansen; Padovani, Damiano & Hansen, Michael Rygaard (2019). On the Energy Efficiency of Dual Prime Mover Pump-Controlled Hydraulic Cylinders, ASME/BATH 2019 Symposium on Fluid Power and Motion Control. The American Society of Mechanical Engineers (ASME). ISSN 9780791859339. doi: 10.1115/FPMC2019-1642. Fulltekst i vitenarkiv
• Husveg, Rune; Husveg, Trygve; Teeffelen, Niels van; Ottestad, Morten & Hansen, Michael Rygaard (2018). Improving Separation of Oil and Water With a Novel Coalescing Centrifugal Pump. SPE Production & Operations. ISSN 1930-1855. 33(04), s. 857–865. doi: 10.2118/188772-PA. Fulltekst i vitenarkiv
• Moslått, Geir-Arne; Hansen, Michael Rygaard & Karlsen, NS (2018). A model for torque losses in variable displacement axial piston motors. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 39(2), s. 107–114. doi: 10.4173/mic.2018.2.5. Fulltekst i vitenarkiv Vis sammendrag

  This paper includes a comparison of earlier presented models for torque losses in hydraulic motors and several proposed models that all rely on data typically available for a system engineer. The new models and the old ones are compared. The new models are all based on a model developed by Jeong 2007 with an expansion that include variable displacement. All of the new models yield very good accuracy down to approximately 50% of maximum displacement and down to approximately 15% of maximum speed. In these operational ranges the deviation in torque is less than 1%. The main purpose of the new models is to facilitate simulations of hydraulically actuated winches with a balance between accuracy and model complexity. This purpose is considered fulfilled with several of the proposed models.

• Gøytil, Petter Hansen; Hansen, Michael Rygaard & Hovland, Geir (2018). Iterative learning applied to hydraulic pressure control. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 39(1), s. 1–14. doi: 10.4173/mic.2018.1.1. Fulltekst i vitenarkiv
• Moslått, Geir-Arne & Hansen, Michael Rygaard (2018). Modeling of Friction Losses in Offshore Knuckle Boom Crane Winch System, 2018 Global Fluid Power Society PhD Symposium (GFPS). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781538647851. doi: 10.1109/GFPS.2018.8472316. Fulltekst i vitenarkiv
• Jakobsen, Jannik Hartwig & Hansen, Michael Rygaard (2018). Synthetic Esters and Dynamics of Pressure Compensated Proportional Directional Control Valves, BATH/ASME 2018 Symposium on Fluid Power and Motion Control. The American Society of Mechanical Engineers (ASME). ISSN 9780791851968. doi: 10.1115/FPMC2018-8933. Fulltekst i vitenarkiv
• Pawlus, Witold; Huynh, Khang & Hansen, Michael Rygaard (2017). Temperature Rise Estimation of Induction Motor Drives Based on Loadability Curves to Facilitate Design of Electric Powertrains. IEEE Transactions on Industrial Informatics. ISSN 1551-3203. 13(3), s. 985–994. doi: 10.1109/TII.2016.2641454. Fulltekst i vitenarkiv
• Pawlus, Witold; Birkeland, Jan Thomas; Huynh, Khang & Hansen, Michael Rygaard (2017). Identification and Experimental Validation of Induction Motor Thermal Model for Improved Drivetrain Design. IEEE transactions on industry applications. ISSN 0093-9994. 53(5), s. 4288–4297. doi: 10.1109/TIA.2017.2700283. Fulltekst i vitenarkiv Vis sammendrag

  The ability of an electric powertrain to perform according to mechanical specifications is equally important as assessing its thermal protection limits which are affected by its electrical and thermal properties. Although rated parameters (such as power, torque, etc.) are easily accessible in catalogs of equipment producers, more specific properties like mass/length of copper winding, heat dissipation factor, etc. are not available to customers. Therefore, an effective selection of drivetrain components is limited due to the lack of sufficient data and the need to consult critical design decisions with suppliers. To overcome this limitation, we propose a method to estimate temperature rise of motor drives based on popular loadability curves which are provided in catalogs. A simple first order thermal model is applied to represent heating/cooling phenomenon of motor drives. The parameters’ identification process is formulated as a nonlinear optimization problem and solved using commercial software products. Within the proposed approach it becomes possible to include the effect of reduced torque availability at low speeds in self-ventilated motors during design of electric actuation systems. Contrary to using a discrete set of permissible overload conditions from the catalogs, the current methodology allows for evaluating a temperature rise of a motor drive for any overload magnitude, duty cycle, and ambient temperature. This greatly improves flexibility of the design process and facilitates communication in a supplier-customer dialog. The discussed method is verified against reference overload recommendations, yielding the same thermal protection levels, and validated using the experimental results, producing identical motor temperature rise profiles as the ones measured on the laboratory test bench.

• Husveg, Rune; Husveg, Trygve; Teeffelen, Niels van; Ottestad, Morten & Hansen, Michael Rygaard (2017). Improving Separation of Oil and Water Using a Novel Coalescing Centrifugal Pump, SPE Abu Dhabi International Petroleum Exhibition & Conference. Society of Petroleum Engineers. ISSN 9781613995631. doi: 10.2118/188772-MS. Fulltekst i vitenarkiv
• Henriksen, Jan; Hansen, Michael Rygaard & Thrane, Fredrik Christopher (2017). Axial Load Capacity of Cold Formed Pipe Flange Connection. Journal of Pressure Vessel Technology. ISSN 0094-9930. 139(5). doi: 10.1115/1.4036853. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, a cold forming process is used where the connection between a pipe and a flange is created by means of radially expanding tool segments inside the pipe. The method is investigated with two purposes, to set up a robust procedure for the process that allows for connections to be made on site, and to set up finite element (FE) simulations that can capture the forces and deformations when pulling the pipe axially out of the flange. Experimental data and FE simulations are used to describe and understand the forces and deformations during the connection process. The rapid increase in radial stiffness experienced when the pipe comes in full circumferential contact with the flange is identified as the best end-of-process indicator. Also, experimental data and FE simulations are used to predict the axial load capacity of a pipe flange connection, and the FE model is utilized in designing the appropriate ridge height of the tool segments.

• Pawlus, Witold; Huynh, Khang & Hansen, Michael Rygaard (2016). Identification of induction motor thermal model for improved drivetrain design, Proceedings 2016 XXII International Conference on Electrical Machines (ICEM). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781509025381. s. 1776–1782. doi: 10.1109/ICELMACH.2016.7732764. Fulltekst i vitenarkiv
• Pawlus, Witold; Kandukuri, Surya Teja; Hovland, Geir; Choux, Martin Marie Hubert & Hansen, Michael Rygaard (2016). EKF-based estimation and control of electric drivetrain in offshore pipe racking machine, 2016 IEEE International Conference on Industrial Technology (ICIT). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781467380751. s. 153–158. doi: 10.1109/ICIT.2016.7474742. Fulltekst i vitenarkiv
• Pawlus, Witold; Choux, Martin Marie Hubert & Hansen, Michael Rygaard (2016). Hydraulic vs. electric: A review of actuation systems in offshore drilling equipment. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 37(1), s. 1–17. doi: 10.4173/mic.2016.1.1. Fulltekst i vitenarkiv
• Sørensen, Jesper Kirk; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2016). Novel concept for stabilising a hydraulic circuit containing counterbalance valve and pressure compensated flow supply. International Journal of Fluid Power. ISSN 1439-9776. 17(3), s. 153–162. doi: 10.1080/14399776.2016.1172446. Fulltekst i vitenarkiv
• Sørensen, Jesper Kirk; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2016). Numerical and experimental study of a novel concept for hydraulically controlled negative loads. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 37(4), s. 195–211. doi: 10.4173/mic.2016.4.1. Fulltekst i vitenarkiv
• Pawlus, Witold; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard; Choux, Martin Marie Hubert & Hovland, Geir (2016). Comparative analysis of numerical models of pipe handling equipment used in offshore drilling applications. AIP Conference Proceedings. ISSN 0094-243X. 1738. doi: 10.1063/1.4952158. Fulltekst i vitenarkiv
• Pawlus, Witold; Choux, Martin Marie Hubert; Hansen, Michael Rygaard & Hovland, Geir (2016). Load torque estimation method to design electric drivetrains for offshore pipe handling equipment. Journal of Offshore Mechanics and Arctic Engineering. ISSN 0892-7219. 138(4). doi: 10.1115/1.4032897. Fulltekst i vitenarkiv
• Pawlus, Witold; Hansen, Michael Rygaard; Choux, Martin Marie Hubert & Hovland, Geir (2016). Mitigation of Fatigue Damage and Vibration Severity of Electric Drivetrains by Systematic Selection of Motion Profiles. IEEE/ASME transactions on mechatronics. ISSN 1083-4435. 21(6), s. 2870–2880. doi: 10.1109/TMECH.2016.2573587. Fulltekst i vitenarkiv
• Henriksen, Jan; Nordhagen, Håkon Ottar; Hoang, Nguyen-Hieu; Hansen, Michael Rygaard & Thrane, Fredrik C. (2015). Numerical and experimental verification of new method for connecting pipe to flange by cold forming. Journal of Materials Processing Technology. ISSN 0924-0136. 220, s. 215–223. doi: 10.1016/j.jmatprotec.2015.01.018. Fulltekst i vitenarkiv Vis sammendrag

  In this paper a new method of connecting pipe to flange without welding is presented. This method is a cold forming process that is based on plastic expansion/deformation of the pipe into a modified standard flange by use of a cold forming tool. The method is patented by Quickflange Technology AS and represents a highly feasible alternative to welding. The successful use of the method requires the ability to predict dimensional and stress/strain characteristics of the pipe and flange after the connection process in order to evaluate the connectivity to the adjacent flange as well as the leak tightness. In addition the ability to predict the process force during the connection process is needed in order to control the process and design the hydraulically actuated cold forming tool. It is shown that it is possible to simulate this process using the finite element (FE) method and achieve a good accordance with experimental results. For this purpose a non-linear FE model of the flange, pipe and forming tool is developed and analyzed using Abaqus. Experimental work, including tensile material testing and Quickflange joining tests were carried out for material model calibration and Quickflange process model validation, respectively. The FE model results are in good accordance with experimental observations in terms of actuation force for the process, deformations and strains of pipe and flange during and after the process. It is concluded that the developed FE model is a useful tool for simulating the presented process within reasonable computational time as long as careful considerations are given to model complexity, material parameters, friction, and pipe geometry tolerances.

• Andersen, Torben Ole; Pedersen, Henrik C. & Hansen, Michael Rygaard (2015). Discrete learning control with application to hydraulic actuators. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 36(4), s. 215–224. doi: 10.4173/mic.2015.4.2. Fulltekst i vitenarkiv
• Kjelland, Magnus Berthelsen & Hansen, Michael Rygaard (2015). Offshore Wind Payload Transfer Using Flexible Mobile Crane. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 36(1), s. 1–9. doi: 10.4173/mic.2015.1.1. Fulltekst i vitenarkiv
• Kjelland, Magnus Berthelsen & Hansen, Michael Rygaard (2015). Using input shaping and pressure feedback to suppress oscillations in slewing motion of lightweight flexible hydraulic crane. International Journal of Fluid Power. ISSN 1439-9776. 16(3), s. 141–148. doi: 10.1080/14399776.2015.1089071. Fulltekst i vitenarkiv
• Pawlus, Witold; Hansen, Michael Rygaard; Hovland, Geir & Choux, Martin Marie Hubert (2015). Torque Peak Reduction and Overload Monitoring of Induction Motors in Offshore Drilling Operations, ACEMP 2015 Optim - Electromotion Joint Conference. IEEE Press. ISSN 9781467372404. s. 393–398. doi: 10.1109/OPTIM.2015.7426962. Fulltekst i vitenarkiv
• Sørensen, Jesper Kirk; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2015). Load independent velocity Control on boom motion using pressure Control valve. I Laamanen, Arto & Huhtala, Kalevi (Red.), The Fourteenth Scandinavian International Conference on Fluid Power, SICFP15. Proceedings. Tampere University of Technology. ISSN 9789521536588. doi: 10.1115/fpni2014-7853. Fulltekst i vitenarkiv
• Kabus, Simon; Hansen, Michael Rygaard & Mouritsen, Ole Østergaard (2014). A new quasi-static multi-degree of freedom tapered roller bearing model to accurately consider non-Hertzian contact pressures in time-domain simulations. Proceedings of the Institution of mechanical engineers. Proceedings part K, journal of multi-body dynamics. ISSN 1464-4193. 228(2), s. 111–125. doi: 10.1177/1464419313513446. Fulltekst i vitenarkiv
• Sørensen, Jesper Kirk; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2014). Boom Motion Control Using Pressure Control Valve, 8th FPNI Ph.D Symposium on Fluid Power, Proceedings. International symposium of product innovation management. ISSN 9780791845820. doi: 10.1115/FPNI2014-7853. Fulltekst i vitenarkiv
• Pawlus, Witold; Choux, Martin Marie Hubert; Hovland, Geir; Hansen, Michael Rygaard & Søren, Øydna (2014). Modeling and Simulation of An Offshore Pipe Handling Machine. I Kolaei, Alireza Rezania (Red.), The 55th Conference on Simulation and Modelling (SIMS 55) Proceedings. Linköping Electronic Conference Proceedings. ISSN 9789175193762. s. 277–284. doi: 10.1063/1.4952158. Fulltekst i vitenarkiv
• Langer, Thomas K.; Iversen, Torkil H.; Mouritsen, Ole Østergaard; Bak, Morten Kollerup & Hansen, Michael Rygaard (2014). A ride comfort tyre model for off-highway vehicles. International Journal of Vehicle Design. ISSN 0143-3369. 65(2/3), s. 222–240. doi: 10.1504/IJVD.2014.060773. Fulltekst i vitenarkiv Vis sammendrag

  re modelling is a major challenge when using time domain multibody simulation models to evaluate ride comfort on off-highway commercial vehicles. Further, parameters for these big tyres are difficult to obtain and thus, commercial car tyre models are difficult to apply. In this research work, a simple vertical tyre model for off-highway ride comfort evaluation is suggested. A displaced volume approach has been developed and combined with the slip theory to yield a tyre model that can be characterised by only three parameters. Full scale measurements on a dump truck have been carried out. Force responses from measurements are compared to the simulation results. Acceleration responses and the level of wholebody vibrations have also been compared.

• Bak, Morten Kollerup & Hansen, Michael Rygaard (2013). Analysis of offshore knuckle boom crane - part two: motion control. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 34(4), s. 175–181. doi: 10.4173/mic.2013.4.2. Fulltekst i vitenarkiv Vis sammendrag

  In this paper design of electro-hydraulic motion control systems for offshore knuckle boom cranes is discussed. The influence of the control valve bandwidth along with the ramp time for the control signal are investigated both analytically with simplified system models and numerically with an experimentally verified crane model. The results of both types of investigations are related to general design rules for selection of control valves and ramp times and the relevance of these design rules is discussed. Generally, they are useful but may be too conservative for offshore knuckle boom cranes. However, as demonstrated in the paper, the only proper way to determine this is to evaluate the motion control system design by means of simulation.

• Bak, Morten Kollerup & Hansen, Michael Rygaard (2013). Analysis of offshore knuckle boom crane - part one: modeling and parameter identification. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 34(4), s. 157–174. doi: 10.4173/mic.2013.4.1. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents an extensive model of a knuckle boom crane used for pipe handling on offshore drilling rigs. The mechanical system is modeled as a multi-body system and includes the structural flexibility and damping. The motion control system model includes the main components of the crane's electro-hydraulic actuation system. For this a novel black-box model for counterbalance valves is presented, which uses two different pressure ratios to compute the flow through the valve. Experimental data and parameter identification, based on both numerical optimization and manual tuning, are used to verify the crane model. The demonstrated modeling and parameter identification techniques target the system engineer and takes into account the limited access to component data normally encountered by engineers working with design of hydraulic systems.

• Bak, Morten Kollerup & Hansen, Michael Rygaard (2013). Model Based Design Optimization of Operational Reliability in Offshore Boom Cranes. International Journal of Fluid Power. ISSN 1439-9776. 14(3), s. 53–65. doi: 10.1080/14399776.2013.10801413. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a model based approach for design of reliable electro-hydraulic motion control systems for off-shore material handling cranes. The approach targets the system engineer and is based on steady-state computations, dynamic time domain simulation and numerical optimization. In general, the modelling takes into account the limited access to component data normally encountered by engineers working with system design. A system model is presented which includes the most important characteristics of both mechanical system and hydraulic components such as the directional control valve and the counterbalance valve. The model is used to optimize the performance of an initial design by minimizing oscillations, maximizing the load range and maintaining operational reliability.

• Sørensen, Søren Emil; Hansen, Michael Rygaard; Ebbesen, Morten Kjeld & Mouritsen, Ole Østergaard (2013). Non-linear optimization of track layouts in loop-sorting-systems. Automation in Construction. ISSN 0926-5805. 31(3), s. 19–30. doi: 10.1016/j.autcon.2012.11.031. Fulltekst i vitenarkiv Vis sammendrag

  Optimization used for enhancing geometric structures is well known. Applying obstacles to the shape optimization problem is on the other hand not very common. It requires a fast contact search algorithm and an exact continuous formulation to solve the problem robustly. This paper focuses on combining shape optimization problems with collision avoidance constraints by which a collision detection algorithm is presented. The presented method is tested against the commercial loop-sorting-system used for sorting of medium sized items. The objective is to minimize price and footprint of the system while maintaining its functionality. Contact constraints are in this context important to include as various obstacles may surround the loop-sorting-system.

• Kjelland, Magnus Berthelsen & Hansen, Michael Rygaard (2013). Numerical and Experiential Study of Motion Control Using Pressure Feedback. Linköping Electronic Conference Proceedings. ISSN 1650-3686. s. 337–343. doi: 10.3384/ecp1392a33. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with the inherent oscillatory nature of pressure compensated motion control of a hydraulic cylinder subjected to a negative load and suspended by means of an overcenter valve. A pressure feedback scheme that indirectly eliminates the oscillations is investigated. The indirect control scheme utilizes pressure feedback to electronically compensate the metering-out allowing for the removal of the compensator and, subsequently, elimination of the oscillations. The suggested electronic compensation scheme is implemented and examined in a single degree-of-freedom test rig actuated by means of a double acting hydraulic cylinder. The control scheme is compared with other control schemes and the importance of measurement filtering and controller cycle time are investigated.

• Langer, Thomas; Iversen, Thorkil K.; Mouritsen, Ole Østergaard; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2013). Suspension system performance optimization with discrete design variables. Structural And Multidisciplinary Optimization. ISSN 1615-147X. 47(4), s. 621–630. doi: 10.1007/s00158-013-0888-7. Fulltekst i vitenarkiv Vis sammendrag

  Suspension systems on commercial vehicles have become an important feature meeting the requirements from costumers and legislation. The performance of the suspension system is often limited by available catalogue components. Additionally the suspension performance is restricted by the travel speed which highly influences the ride comfort. In this article a suspension system for an articulated dump truck is optimized in sense of reducing elapsed time for two specified duty cycles without violating a certain comfort threshold level. The comfort threshold level is here defined as a whole-body vibration level calculated by ISO 2631-1. A three-dimensional multibody dynamics simulation model is applied to evaluate the suspension performance. A non-gradient optimization routine is used to find the best possible combination of continuous and discrete design variables including the optimum operational speed without violating a set of side constraints. The result shows that the comfort level converges to the comfort threshold level. Thus it is shown that the operational speed and hence the operator input influences the ride comfort level. Three catalogue components are identified by the optimization routine together with a set of continuous design variables and two operational speeds one for each load case. Thus the work demonstrates handling of human factors in optimization of a mechanical system with discrete and continuous design variables.

• Sørensen, Rasmus Mørk; Hansen, Michael Rygaard & Mouritsen, Ole Østergaard (2012). NUMERICAL AND EXPERIMENTAL STUDY OF HYDROSTATIC DISPLACEMENT MACHINE. International Journal of Fluid Power. ISSN 1439-9776. 13(2), s. 29–40. doi: 10.1080/14399776.2012.10781051. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a simulation tool to determine the structural deflections and corresponding leakage flow in a hydrostatic displacement motor. The simulation tool is applied to a new motor principle that is categorized as an extreme low-speed high-torque motor with dimensions that calls for attention to the volumetric efficiency. To counteract structural deflections the motor is equipped with compensation pressure volumes that may be used to limit the leakage flow across the end faces of the circular rotor. This leakage flow is investigated by solving Reynolds equation for the pressure distribution across both end faces. The fluid pressure is combined with structural calculations in a fluid structural interaction simulation, which evaluates the influence of structural deflections on the gaps and the leakage flow. The numerical work is validated by prototype tests. Both deflections and leakage flows are measured and compared with those from the simulations with good correlation. The deflections, and hence leakage flow, are reduced by the use of compensation pressure volumes, which is validated both numerically and experimentally.

• Kabus, Simon; Hansen, Michael Rygaard & Mouritsen, Ole Østergaard (2012). A New Quasi-Static Cylindrical Roller Bearing Model to Accurately Consider Non-Hertzian Contact Pressure in Time Domain Simulations. Journal of tribology. ISSN 0742-4787. 134(4). doi: 10.1115/1.4007219. Fulltekst i vitenarkiv Vis sammendrag

  The accuracy of the fatigue life calculations in rolling bearing simulations is highly dependent on the precision of the roller-raceway contact simulations. Several different methods exist to simulate these pressure distributions and in time domain bearing simulations, where many contacts need evaluation, the simple and time efficient methods are more popular, yielding erroneous life estimates. This paper presents a new six degree of freedom frictionless quasi-static time domain cylindrical roller bearing model that uses high precision elastic half-space theory to simulate the contact pressures. The potentially higher computational demand using the advanced contact calculations is addressed by preprocessing a series of contacts at different centerline approaches and roller tilt angles, which are used for interpolating contact results during time domain simulations. It is demonstrated that this new model allows for simulation of bearing misalignments, roller centrifugal forces, and flange contact induced roller tilt moments, and that the effect of these conditions is directly evaluated in a detailed fatigue life analysis. Finally, the stiffness of the bearing model is validated against existing experimental data with good correlation.

• Sørensen, Søren Emil; Hansen, Michael Rygaard; Ebbesen, Morten Kjeld & Mouritsen, Ole Østergaard (2012). Enhanced chain dynamics in loop-sorting-systems by means of layout optimization and a kinematic model of the polygon action. Structural And Multidisciplinary Optimization. ISSN 1615-147X. 45(6), s. 907–916. doi: 10.1007/s00158-011-0743-7. Fulltekst i vitenarkiv Vis sammendrag

  Poor dynamics owing to polygon action is a known concern in mechanical applications of closed articulated chains. In this paper a kinematic model of the polygon action in large chains of loop-sorting-systems is proposed. Through optimization techniques the chain dynamics is improved by minimizing the polygon action using a parametric model of the track layout as design variables. Three formulations of the kinematic polygon action are tested on an average sized planer tracks layout to find a superior model. Verification of the proposed optimization method is performed using a state-of-the-art multi-body simulation model of the chain dynamics.

• Langer, Thomas; Iversen, Thorkil K.; Andersen, Niels K.; Mouritsen, Ole Østergaard & Hansen, Michael Rygaard (2012). Reducing whole-body vibration exposure in backhoe loaders by education of operators. International Journal of Industrial Ergonomics. ISSN 0169-8141. 42(3), s. 304–311. doi: 10.1016/j.ergon.2012.03.001. Fulltekst i vitenarkiv Vis sammendrag

  Whole-body vibration is a health hazard for operators of construction machinery. The level of whole-body vibration exposure on the operator is governed by three different factors; performance of the suspension system of the machine, planning of the work and the skills of the operator. In this research work it is investigated whether there is a potential in bringing down the level of whole-body vibration exposure by educating operators of backhoe loaders. This is carried out by an experimental setup. Six experienced operators participated in the experiments carried out on two different sizes of backhoe loaders. Each operator had to complete three different tasks without any kind of instructions. Subsequently they got a short education on eco-driving and vibration avoidance and carried out the tasks once more. Time duration, whole-body vibration exposure and fuel consumption was registered before and after education. The result of the short education was an average reduction in the whole-body vibration exposure of 22.5%. And for all completed tasks expect one a considerably fuel saving was obtained too – up to 38%. This experiment demonstrates that education of the operator will improve the occupational health and save fuel. The results also indicate that these improvements can be obtained without reduction in productivity as the instructions become a habit for the operators. Thus it is profitable for the employer to educate the employees operating construction machinery. Relevance to industry: The findings of this work is highly relevant to the construction industry. It shows a great potential in reducing damaging vibration and at the same time reduce fuel consumption. It also emphasizes the need for better education of machine operators.

• Haastrup, Morten; Hansen, Michael Rygaard; Ebbesen, Morten Kjeld & Mouritsen, Ole Østergaard (2012). Modeling and Parameter Identification of Deflections in Planetary Stage of Wind Turbine Gearbox. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 33(1), s. 1–11. doi: 10.4173/mic.2012.1.1. Fulltekst i vitenarkiv Vis sammendrag

  The main focus of this paper is the experimental and numerical investigation of a 750kW wind turbine gearbox. A detailed model of the gearbox with main shaft has been created using MSC.Adams. Special focus has been put on modeling the planet carrier (PLC) in the gearbox. For this purpose experimental data from a drive train test set up has been analyzed using parameter identification to quantify misalignments. Based on the measurements a combination of main shaft misalignment and planet carrier deflection has been identified. A purely numerical model has been developed and it shows good accordance with the experimental data.

• Zhou, Lelai; Bai, Shaoping & Hansen, Michael Rygaard (2012). Integrated dimensional and drive-train design optimization of a light-weight anthropomorphic arm. Robotics and Autonomous Systems. ISSN 0921-8890. 60(1), s. 113–122. doi: 10.1016/j.robot.2011.09.004. Fulltekst i vitenarkiv Vis sammendrag

  An approach to minimize the mass of robotic manipulators is developed by integrated dimensional and drive-train optimization. The method addresses the influences of dimensions and characteristics of drive-trains in the design optimization. Constraints are formulated on the basis of kinematic performance and dynamic requirements, whereas the main objective is to minimize the total mass. Case studies are included to demonstrate the application of the optimization method in the design of assistive robots.

• Cibulka, Jaroslav; Ebbesen, Morten Kjeld; Hovland, Geir; Robbersmyr, Kjell G & Hansen, Michael Rygaard (2012). A Review on Approaches for Condition Based Maintenance in Applications with Induction Machines Located Offshore. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 33(2), s. 69–86. doi: 10.4173/mic.2012.2.4. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a review of different approaches for Condition Based Maintenance (CBM) of induction machines and drive trains in offshore applications. The paper contains an overview of common failure modes, monitoring techniques, approaches for diagnostics, and an overview of typical maintenance actions. Although many papers have been written in this area before, this paper puts an emphasis on recent developments and limits the scope to induction machines and drive trains applied in applications located offshore.

• Bak, Morten Kollerup; Hansen, Michael Rygaard & Nordhammer, Pål Andre (2012). A Method for Reliable Motion Control of Pressure Compensated Hydraulic Actuation with Counterbalance Valves, 2012 12th International Conference on Control, Automation and Systems, Proceedings. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9788993215045. s. 759–763. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with the robust handling of negative loads using counterbalance valves in hydraulically actuated equipment. Emphasis is on pressure compensated velocity control of a double acting cylinder. A linearized stability analysis of such a hydraulic circuit with hard quantities; cylinder volumes, cylinder area ratio and counterbalance valve pilot area ratio, is used prove to that without extra measures such a system will be unstable in a substantial part of the cylinder stroke. An alternative approach that guarantees stability while maintaining the counterbalance valve is put forward. The approach transfers the task of throttling the return flow from the counterbalance valve to the directional control valve. Thereby the remaining functionality of the multifunctional counterbalance valve is maintained. The practical implementation and limitation of the approach is discussed as well as the influence on overall performance.

• Iskandarani, Yousef; Karimi, Hamid Reza & Hansen, Michael Rygaard (2012). An Iterative Based Approach for Hysteresis Parameters Estimation in Magnetorheological Dampers. I R.R, Yager; Sgurev, V. & Hadjiski, M. (Red.), Proceedings of 2012 IEEE 6th International Conference Intelligent Systems. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781467327824. s. 439–444. doi: 10.1109/is.2012.6335174. Fulltekst i vitenarkiv Vis sammendrag

  The following work entails the problem of regenerating the hysteresis loop in the Magnetorheological (MR) dampers. The collected data from tests are not sufficient neither efficient for designing optimal controls compensating for the hysteresis in the dampers. This work presents an iterative based approach for estimating the hysteresis parameters, the method however can be generalized for different kind of dampers or actuators hence the hysteresis loop can be generalized using available test data. Some assumptions can be introduced in order to facilitate the underlines of the parameters estimation, one of the assumptions in this work is to use predetermined hysteresis parameters and regenerate the actual data using continuous state space model (SSM). The SSM can be based on verified models like Bouc- Wen, Lugre or Dahl models. In this work, Bouc-Wen model is used to generate the actual hysteresis data. The core of this work is to use the iterative approach based on Particle Swarm Optimization (PSO). The PSO algorithm is used along with other algorithms like the Root Mean Square (RMS) error which is used to evaluate the convergence of the results at each of the iterations for a defined number of iterations. The trade-off relation is the basis of evaluation when using the PSO based algorithm, dependency on initial guessing, number of iterations and desired estimation accuracy. However, the PSO algorithm tend to estimate the hysteresis parameters close enough to generate the actual hysteresis enabling a ground to develop similar algorithms for different kind of actuators or dampers. Keywords: Algorithm, Analysis, Estimation, Hysteresis phenomena, Hysteresis parameters, Magnetorheological damper, Particle Swarm Optimization

• Bak, Morten Kollerup; Hansen, Michael Rygaard & Nordhammer, Pål Andre (2012). Controlling the Slewing Motion of Hydraulically Actuated Cranes Using Sequentially Activation of Counterbalance Valves, 2012 12th International Conference on Control, Automation and Systems, Proceedings. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9788993215045. s. 773–778. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with the controlled motion of hydraulically actuated transmissions characterized by large inertias, backlash and several parallel coupled gearmotors. A method for controlled start and braking of such a transmission is put forward that utilizes sequential activation of the counterbalance valves of the hydraulic circuit. The method, which has been implemented into numerous high end offshore applications, is demonstrated by means of time domain simulations of a knuckle boom crane used for pipe handling in offshore drilling. The suggested activation method may yield higher load levels in the transmission but has the ability to reduce or eliminate the occurence of impact and loss of contact in the transmission.

• Haaø, Jørgen; Vangen, Steffen; Tyapin, Ilya; Choux, Martin Marie Hubert; Hovland, Geir & Hansen, Michael Rygaard (2012). The Effect of Friction in Passive and Active Heave Compensation of Crown Block Mounted Compensators. I Imsland, Lars Struen (Red.), 2012 IFAC Workshop on Automatic Control in Offshore Oil and Gas Production : Norwegian University of Science and Technology 31.5-1.6 2012. Elsevier. ISSN 9783902661999. doi: 10.3182/20120531-2-no-4020.00040. Fulltekst i vitenarkiv Vis sammendrag

  This paper studies the effects of friction model during passive and active heave compensation of offshore drilling equipment. The main purpose of heave compensation while drilling from vessels or semi-submersible platforms is to maintain the drilling operation unaffected by the wave induced motion. The investigated system is of an existing crown mounted compensator. A model of the system is developed which includes mechanics, hydraulics and pneumatics. The passive heave compensation scheme is described including force equalising hydraulic cylinders. In this paper the detrimental effect of friction on the heave compensation performance in both passive and active heave compensation is investigated and discussed.

• Kjelland, Magnus Berthelsen; Hansen, Michael Rygaard; Tyapin, Ilya & Hovland, Geir (2012). Tool-Point Control for a Redundant Heave Compensated Hydraulic Manipulator. I Imsland, Lars Struen (Red.), 2012 IFAC Workshop on Automatic Control in Offshore Oil and Gas Production : Norwegian University of Science and Technology 31.5-1.6 2012. Elsevier. ISSN 9783902661999. doi: 10.3182/20120531-2-no-4020.00034. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, theoretical and experimental implementation of heave compensation on a redundant hydraulically actuated manipulator with 3-dof has been carried out. The redundancy is solved using the pseudo-inverse Jacobian method. Techniques for minimizing velocities and avoiding mechanical joint saturations is implemented in the null space joint motion. Model based feed-forward, combined with a PI-controller handles the velocity control of each joint.A time domain simulation model has been developed, experimentally verified, and used for controller parameter tuning. Model verification and experimental results are obtained while the manipulator is exposed to wave disturbances created in a dry environment by means of a Stewart platform.

• Kjelland, Magnus Berthelsen & Hansen, Michael Rygaard (2012). Tool point tracking for redundant hydraulic actuated manipulator using velocity control. I Milani, Massimo; Montorsi, Luca & Paltrinieri, Fabrizio (Red.), Proceedings of the 7th FPNI PhD Symposium on Fluid Power 2012. Edizioni Technograf. ISSN 9788875590697. s. 767–781. Fulltekst i vitenarkiv Vis sammendrag

  Tool-point control has a number of desired effects when developing heave compensated manipulators, since it's the tool point itself or what it lifting that is to be compensated. Consider a three-linked redundant hydraulic manipulator. Introducing redundancy, the kinematic structure becomes more complex and difficult to solve, but is also brings with many positive properties. The redundancy is solved using the wellknown pseudo-inverse Jacobian method. Techniques for maximizing velocities and avoiding mechanical joint saturations are implemented in the null space joint motion. Model based feed-forward based on live measurements of the differential pressure over the servo-valves, combined with a PID controller, handles the velocity control for each joint. The different control strategies are all dynamically tested with varying reference trajectory and pressure levels. A dynamical model is created in using multibody dynamic, using commercial modeling software, where the controller is implemented and tested. Model verification, parameter estimation and experimental results are obtained while the manipulator are compensating disturbance created by a six-degrees of freedom, Stewart platform.

• Bak, Morten Kollerup & Hansen, Michael Rygaard (2012). Modeling, performance testing and parameter identification of pressure compensated proportional directional control valves. I Milani, Massimo; Montorsi, Luca & Paltrinieri, Fabrizio (Red.), Proceedings of the 7th FPNI PhD Symposium on Fluid Power 2012. Edizioni Technograf. ISSN 9788875590697. s. 889–908. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a practical approach for dynamic performance testing of pressure compensated proportional directional control valves and parameter identification for a proposed model of such types of valves. The performance test is based on the methods described in BS ISO 10770-1:2009, /1/. The proposed valve model is intended for time domain simulation of hydraulic-mechanical systems and uses a 2nd order model to describe the dynamics of the valve. As a case study a Sauer-Danfoss PVG32 is considered.

• Iskandarani, Yousef; Karimi, Hamid Reza & Hansen, Michael Rygaard (2012). An Iterative Based Approach to Parameter Estimation of Magnetorheological Damper Hysteresis Model Based on Particle Swarm Optimization. International Journal of Control Theory and Applications (IJCTA). ISSN 0974-5572. 5(1), s. 61–71. Fulltekst i vitenarkiv
• Sørensen, Rasmus Mørk; Hansen, Michael Rygaard & Mouritsen, Ole Østergaard (2012). Numerical and Experimental Study of Friction Loss in Hydrostatic Motor. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 33(3), s. 99–109. doi: 10.4173/mic.2012.3.2. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents a numerical and experimental study of the losses in a hydrostatic motor principle. The motor is designed so that the structural deflections and lubricating regimes between moving surfaces and, subsequently, the leakage and friction losses, can be controlled during operation. This is done by means of additional pressure volumes that influence the stator deflection. These pressures are referred to as compensation pressures and the main emphasis is on friction or torque loss modeling of the motor as a function of the compensation pressures and the high and low pressures related to the load torque. The torque loss modeling is identified as a Stribeck curve which depends on gap height. The asperity friction is decreasing exponentially with an increase in gap height. The parameters of the torque loss model are based on prototype measurements that include the structural deflections of the lubricating gap faces.

• Kjelland, Magnus Berthelsen; Hansen, Michael Rygaard; Tyapin, Ilya & Hovland, Geir (2012). Tool-Point Control of a Planar Hydraulically Actuated Manipulator with Compensation of Non-Actuated Degree of Freedom, 2012 12th International Conference on Control, Automation and Systems, Proceedings. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9788993215045. s. 672–677. Fulltekst i vitenarkiv Vis sammendrag

  The current work is on motion control of a hydraulically actuated manipulator with a view to handle offshore payload transfer between moving frames. The manipulator has redundant actuation and also, a non-actuated degree of freedom. The motion control has two targets: tool point control and compensation of the non-actuated degree of freedom. The redundancy is handled by means of pseudo-inverse kinematics while optimizing a cost function, avoiding mechanical joint limits. The compensation of the un-actuated degree of freedom employs LQR control, minimizing position and velocity error while maintaining the tracking reference for the tool-point. The proposed control scheme is implemented and experimentally validated in a practical system where the manipulator is mounted on a Stewart platform that allows for the simulation of wave induced heave motion as a disturbance.

• Ottestad, Morten; Nilsen, Nicolai & Hansen, Michael Rygaard (2012). Reducing the Static Friction in Hydraulic Cylinders by Maintaining Relative Velocity Between Piston and Cylinder, 2012 12th International Conference on Control, Automation and Systems, Proceedings. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9788993215045. s. 764–769. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with friction in hydraulic cylinders and it’s influence on the performance of hydralically actuated system. A method for the elimination of stiction in hydraulic cylinders is presented and experimentally verified. The method utilizes the rotational degree of freedom between the piston and the cylinder to add relative velocity at the contact surfaces between piston and cylinder when the main axial motion is zero. For modeling purposes an augmentation of the Stribeck friction force equation is introduced that reflects the influence of the added motion. The possible impact of stiction elimination on the performance of heave compensation equipment is discussed and examplified via time domain simulations.

• Bak, Morten Kollerup; Hansen, Michael Rygaard & Karimi, Hamid Reza (2011). Robust Tool Point Control for Offshore Knuckle Boom Crane. I Bittanti, Sergio (Red.), Proceedings of the 18th IFAC World Congress 2011. Elsevier. ISSN 9783902661937. Fulltekst i vitenarkiv Vis sammendrag

  This paper considers the design of an H∞ controller for tool point control of a hydraulically actuated knuckle boom crane. The paper describes the modelling of the crane's mechanical and hydraulic systems and a disturbance model. These are linearised and combined in a state-space model used for the controller design. The controller synthesis problem is to design (if possible) an admissible controller that solves the problem of robust regulation against step inputs with an H∞ constraint based on the internal model principle. Simulation results are given to show the effectiveness of the method.

• Zhou, Lelai; Bai, Shaoping & Hansen, Michael Rygaard (2011). Integrated Design Optimization of a 5-DOF Assistive Light-weight Anthropomorphic Arm, Advanced Robotics (ICAR), 2011 15th International Conference on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781457711589. s. 659–664. doi: 10.1109/icar.2011.6088552. Fulltekst i vitenarkiv Vis sammendrag

  An integrated dimensional and drive train optimization method was developed for light-weight robotic arm design. The method deals with the determination of optimal link lengths and the optimal selection of motors and gearboxes from commercially available components. Constraints are formulated on the basis of kinematic performance and dynamic requirements, whereas the main objective is to minimize the weight. The design of a human-like arm, which is 10 kg in weight with a load capacity of 5 kg, is described.

• Zhou, Lelai; Bai, Shaoping & Hansen, Michael Rygaard (2011). Design optimization on the drive train of a light-weight robotic arm. Mechatronics (Oxford). ISSN 0957-4158. 21(3), s. 560–569. doi: 10.1016/j.mechatronics.2011.02.004. Fulltekst i vitenarkiv
• Ottestad, Morten; Nilsen, Nico & Hansen, Michael Rygaard (2011). A Method for Friction Control in Hydraulic Cylinders. I Singh, Maneesh; N., Rao Raj B. K. & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 9780954130725. s. 817–823. Fulltekst i vitenarkiv Vis sammendrag

  This paper is concerned with friction in hydraulic cylinders and its influence on the performance of hydralically actuated system. A method for friction control is presented. The basic idea in the proposed method is that the absolute value of the relative velocity between piston and cylinder rather than just the longitudinal relative velocity determines to what degree the zero-velocity stiction is eliminated. A test rig has been designed that is capable of introducing a rotational motion of the piston without introducing additional shear forces, i.e., via a force couple. The results clearly show that the stiction part of the frictional force is eliminated when the rotational motion is controlled so that it appears simultaneously with zero relative velocity in longitudinal direction. The experimental data has made it possible to develop a friction model that describes the friction in a hydraulic cylinder that covers any combination of longitudinal and rotational relative velocity.

• Sørensen, Søren Emil; Hansen, Michael Rygaard; Ebbesen, Morten Kjeld & Mouritsen, Ole Østergaard (2011). Time domain simulation of large-scale material handling chains using an unconstrained formulation. Proceedings of the Institution of mechanical engineers. Proceedings part K, journal of multi-body dynamics. ISSN 1464-4193. 225(2), s. 95–110. doi: 10.1177/1464419311406952. Fulltekst i vitenarkiv Vis sammendrag

  This article presents a dynamic time domain simulation model of loop-sortation systems. Loop-sortation systems for sortation of medium-size items are designed as a closed chain of carts guided in a closed loop track with a view to meet customers’ requirements of capacity and space available. Loop-sortation systems are complex mechatronic systems which require the use of simulation models in order to analyse, predict, and improve the dynamic performance in a cost efficient way. The model utilizes theory for unconstrained rigid multibody dynamics where contact between carts and between cart and track are modelled through the use of force elements. To determine contact between the track and the chain of carts, a rapid and robust contact search formulation has been developed and implemented in the model. Comparisons of main forces of the chain model are made with experimental measurements on three different test layouts. Verification results show that the normalized root mean square deviations are generally less than 10  percent.

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• Sanfilippo, Filippo; Fossum, Mariann & Hansen, Michael Rygaard (2026). Redefining Care and Work Practices: The Role of Autonomy in the Future of Nursing Homes | Springer Nature Link. Springer. ISBN 9783031977817. doi: 10.1007/978-3-031-97781-7_26. Fulltekst i vitenarkiv Vis sammendrag

  Nursing homes face increasing challenges due to workforce shortages, ageing populations, and rising care demands. This paper explores the dynamics of human-robot interaction (HRI) in nursing home environments, focusing on how autonomous robots engage with nurses and...

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• Fossum, Mariann; Hansen, Michael Rygaard; Thygesen, Elin; Tørresen, Jim; Melkas, Helinä & Losada-Floriano, Diego (2026). SAKO project seminar. Fulltekst i vitenarkiv Vis sammendrag

  Seminar June 2026 for all participants involved in the project with invited presenters.

• Fossum, Mariann; Hansen, Michael Rygaard; Thygesen, Elin; Leifson, Ragni MacQueen; Giil, Elisabeth & Enerstvedt, Camilla [Vis alle 7 forfattere av denne artikkelen] (2026). SAKO Supplier Dialogue. doi: https:/www.uia.no/english/about-uia/centres-and-networks/centre-for-e-health/events/sako-supplier-dialouge.html. Fulltekst i vitenarkiv Vis sammendrag

  The University of Agder invites suppliers and technology providers to a dialogue meeting as part of the research project SAKO. The aim of the meeting is to explore potential technological solutions and collaboration related to the development of a service robot solution for use in nursing homes, with a particular focus on relieving staff from heavy and repetitive transport tasks in their daily work.

• Fossum, Mariann & Hansen, Michael Rygaard (2025). Lørdagsuniversitetet; Serviceroboter som Arbeidsstøtte i Kommunale helse- og Omsorgstjenester. Fulltekst i vitenarkiv Vis sammendrag

  Presentasjon på lørdagsuniversitetet

• Fossum, Mariann & Hansen, Michael Rygaard (2025). Hva kan serviceroboter bidra med i helsetjenesten? Fulltekst i vitenarkiv Vis sammendrag

  Presentasjon av SAKO prosjektet på Lørdagsuniversitetet i Risør.

• Bergsjø, Leonora Onarheim; Hagen, Daniel & Hansen, Michael Rygaard (2025). Hva om serviceroboter blir helsepersonells nye beste venn? doi: https:/www.uia.no/om-uia/senter-og-nettverk/senter-for-e-helse/arrangementer/arendalsuka_sako.html. Fulltekst i vitenarkiv
• Wathne, Joakim Holtskog; Hansen, Michael Rygaard & Zhou, Jing (2025). Benefits of Secondary Control over Primary Control for AHC Winches. Fulltekst i vitenarkiv
• Larson, Niclas; Fidje, Anders Støle; Hundeland, Per Sigurd; Hansen, Michael Rygaard; Ovedal-Hakestad, Siri & Erfjord, Ingvald [Vis alle 11 forfattere av denne artikkelen] (2022). Spøkelser etter avdøde størrelser hjemsøker KLæM 22. [Internet]. Apple Podcasts. Fulltekst i vitenarkiv Vis sammendrag

  I en annerledes episode av Spøkelser etter avdøde størrelser har Niclas Larson intervjuet foredragsholdere og deltakere i Konferanse for lærerutdannere i matematikk, KLæM 22. Dette har blitt satt sammen til en episode som rapporterer om noen av bidragene på konferansen og hva et par av deltakerne syntes om innholdet. Dessuten får vi igjen møte Andy the Candy, som var gjest i 10. episode sesong 1 – PhD student under cover.

• Gøytil, Petter Hansen; Hansen, Michael Rygaard & Padovani, Damiano (2022). Linear Time-Invariant Modelling of Electrohydraulic Cylinders. Fulltekst i vitenarkiv
• Henriksen, Jan; Hansen, Michael Rygaard & Thrane, Fredrik Christopher (2018). Experimentally and Numerically Verified Analytical Model for Prediction of Process Force in Novel Method for Pipe-to-Flange Joining. Fulltekst i vitenarkiv
• Husveg, Rune; Husveg, Trygve; Teeffelen, Niels van; Ottestad, Morten & Hansen, Michael Rygaard (2017). Improving Separation of Oil and Water Using a Novel Coalescing Centrifugal Pump. Fulltekst i vitenarkiv
• Husveg, Rune; Husveg, Trygve; Teeffelen, Niels van; Ottestad, Morten & Hansen, Michael Rygaard (2016). Performance of a Coalescing Multistage Centrifugal Produced Water Pump with Respect to Water Characteristics and Point of Operation. Fulltekst i vitenarkiv
• Pedersen, Henrik C.; Andersen, Torben Ole & Hansen, Michael Rygaard (2016). Guidelines for Properly Adjusting Pressure Feedback in Systems with Over-Centre Valves. Fulltekst i vitenarkiv
• Pawlus, Witold; Hansen, Michael Rygaard; Hovland, Geir & Choux, Martin Marie Hubert (2015). Torque Peak Reduction and Overload Monitoring of Induction Motors in Offshore Drilling Operations. Fulltekst i vitenarkiv
• Pawlus, Witold; Ebbesen, Morten Kjeld; Hansen, Michael Rygaard; Choux, Martin Marie Hubert & Hovland, Geir (2015). Comparative Analysis of Numerical Models of Pipe Handling Equipment Used in Offshore Drilling Applications. Fulltekst i vitenarkiv
• Henriksen, Jan & Hansen, Michael Rygaard (2013). FEM simulation of cold deforming pipe into flange. Fulltekst i vitenarkiv
• Moslått, Geir-Arne; Meisfjordskar, Anders; Hansen, Michael Rygaard & Padovani, Damiano (2020). Motion Control of Hydraulic Winch Using Variable Displacement Motors. Universitetet i Agder. ISSN 9788284270081. Fulltekst i vitenarkiv Vis sammendrag

  To compete in the open market of the offshore crane industry, it is imperative for the manufacturer to continuously improve crane operability. In this context, the crane operability is expressed by means of a so-called weather window. The weather window is computed from the crane characteristics in combination with that of the vessel and the payload to be handled. It returns a set of boundaries for when it is accepted to perform a planned lift, mainly in terms of current sea-state and wind. The most important crane operability characteristics that enter into the computation of the weather window are maximum wire velocity and load capacity. This thesis focuses on how to improve the operability of active heave compensated offshore cranes. Two ways of achieving that goal have been investigated, namely, an improved control strategy and the use of model-based lift planning. The system investigated is the hydraulic active/passive winch system used by National Oilwell Varco. A new control strategy for the system was developed, tested, and implemented. The new strategy utilizes that variable displacement of the hydraulic motors of the active system of the winch drive. The strategy, semi secondary control, gave significant benefits in terms of reduced peak-pressure, increased load capacity, increased wire-speed capacity, and smoother winch performance at low winch speed. The results were validated and verified through simulations and in-field measurements.

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