Michael Rygaard Hansen

• 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 978-1-6654-7095-7. doi: 10.1109/ICECCME55909.2022.9988490.
• 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. ISSN 2218-6581. 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.

• 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.

• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2021). Novel Concept for Electro-Hydrostatic Actuators for Motion Control of Hydraulic Manipulators. Energies. ISSN 1996-1073. 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.

• Husveg, Rune; Husveg, Trygve; van Teeffelen, Teeffelen; 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.
• 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.
• 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.
• 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.
• 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. ISSN 1996-1073. 13(10). doi: 10.3390/en13102671. 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.
• Jensen, Konrad Johan; Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2020). Adaptive Feedforward Control of a Pressure Compensated Differential Cylinder. Applied Sciences. ISSN 2076-3417. 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.

• 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. ISSN 2076-0825. 9(2). doi: 10.3390/act9020027. 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. ISSN 2076-0825. 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.

• 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 978-0-7918-5933-9. doi: https:/doi.org/10.1115/FPMC2019-1642.
• 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 978-0-7918-5933-9. doi: https:/doi.org/10.1115/FPMC2019-1710.
• Husveg, Rune; Husveg, Trygve; van Teeffelen, Niels; 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.
• 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 978-0-7918-5196-8. doi: 10.1115/FPMC2018-8933.
• 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 conference proceedings. ISSN 978-1-5386-4785-1. doi: 10.1109/GFPS.2018.8472316.
• Husveg, Rune; Husveg, Trygve; van Teeffelen, Niels; 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.
• 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.
• 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.
• Husveg, Rune; Husveg, Trygve; van Teeffelen, Niels; 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 978-1-61399-563-1. doi: 10.2118/188772-MS.
• 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. 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; 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. 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.

• 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.
• 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.
• 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.
• 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.
• 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.
• 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 conference proceedings. ISSN 978-1-5090-2538-1. s. 1776–1782. doi: 10.1109/ICELMACH.2016.7732764.
• 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.
• 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.
• 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 978-1-4673-8075-1. s. 153–158. doi: 10.1109/ICIT.2016.7474742.
• 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.
• 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 978-1-4673-7240-4. s. 393–398. doi: 10.1109/OPTIM.2015.7426962.
• 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.
• 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.
• 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 978-952-15-3658-8. doi: 10.1115/fpni2014-7853.
• 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. 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.

• Pawlus, Witold; Choux, Martin Marie Hubert; Hovland, Geir; Hansen, Michael Rygaard & Søren, Øydna (2014). Modeling and Simulation of An Offshore Pipe Handling Machine. I Rezania Kolaei, Alireza (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.
• 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 978-0-7918-4582-0. doi: 10.1115/FPNI2014-7853.
• 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.
• 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. 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.

• 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. 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. 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.

• 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. 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. 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. 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.

• 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. 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. 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.

• 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. 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. 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.

• 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. 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.

• 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. 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.

• 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 conference proceedings. ISSN 978-89-93215-04-5. s. 759–763. 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.

• 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 conference proceedings. ISSN 978-89-93215-04-5. s. 773–778. 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.

• 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 978-88-7559-069-7. s. 767–781. 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 978-88-7559-069-7. s. 889–908. 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.

• 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 978-3-902661-99-9. doi: 10.3182/20120531-2-no-4020.00040. 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 978-3-902661-99-9. doi: 10.3182/20120531-2-no-4020.00034. 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.

• 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. 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.

• 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 conference proceedings. ISSN 978-1-4673-2782-4. s. 439–444. doi: 10.1109/is.2012.6335174. 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

• 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.
• 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. 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.

• 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.
• 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 conference proceedings. ISSN 978-89-93215-04-5. s. 672–677. 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 conference proceedings. ISSN 978-89-93215-04-5. s. 764–769. 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.

• 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 conference proceedings. ISSN 978-1-4577-1158-9. s. 659–664. doi: 10.1109/icar.2011.6088552. 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 & Rasmussen, John (2011). Modeling of Human Arm Energy Expenditure for Predicting Energy Optimal Trajectories. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 31(3), s. 91–101. doi: 10.4173/mic.2011.3.1. Vis sammendrag

  Human arm motion can inspire the trajectory planning of anthropomorphic robotic arms to achieve energy-efficient movements. An approach for predicting metabolic cost in the planar human arm motion by means of the biomechanical simulation is proposed in this work. Two biomechanical models, including an analytical model and a musculoskeletal model, are developed to implement the proposed approach. The analytical model is developed by modifying a human muscle expenditure model, in which the muscles are grouped as torque providers for computation efficiency. In the musculoskeletal model, the predication of metabolic cost is conducted on the basis of individual muscles. With the proposed approach, metabolic costs for parameterized target-reaching arm motions are calculated and utilized to identify optimal arm trajectories.

• Sørensen, Søren Emil; Hansen, Michael Rygaard; Ebbesen, Morten Kjeld & Mouritsen, Ole Østergaard (2011). Implicit Identification of Contact Parameters in a Continuous Chain Model. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 32(1), s. 1–15. doi: 10.4173/mic.2011.1.1. Vis sammendrag

  Accurate contact modeling is of great importance in the field of dynamic chain simulations. In this paper emphasis is on contact dynamics for a time-domain simulation model of large chains guided in a closed loop track. The chain model is based on theory for unconstrained rigid multibody dynamics where contact within the chain and with the track is defined through continuous point contacts using the contact indentation and rate as means. This paper presents an implicit method to determine contact parameters of the chain model through the use of none gradient optimization methods. The set of model parameters are estimated by minimizing the residual between simulated and measured results. The parameter identification is tested on four different formulations of the Hunt-Crossly hysteresis damping factor with the aim of recognizing a superior model.

• 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. 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.

• Haastrup, Morten; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2011). Modeling of Wind Turbine Gearbox Mounting. MIC Journal: Modeling, Identification and Control. ISSN 0332-7353. 32(4), s. 141–149. doi: 10.4173/mic.2011.4.2. Vis sammendrag

  In this paper three bushing models are evaluated to find a best practice in modeling the mounting of wind turbine gearboxes. Parameter identification on measurements has been used to determine the bushing parameters for dynamic simulation of a gearbox including main shaft. The stiffness of the main components of the gearbox has been calculated. The torsional stiffness of the main shaft, gearbox and the mounting of the gearbox are of same order of magnitude, and eigenfrequency analysis clearly reveals that the stiffness of the gearbox mounting is of importance when modeling full wind turbine drivetrains.

• 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 978-3-902661-93-7.
• Bak, Morten Kollerup; Hansen, Michael Rygaard & Nordhammer, Pål Andre (2011). Virtual Prototyping - Model of Offshore Knuckle Boom Crane. I Singh, Maneesh; Raj B. K. N., Rao & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 0-9541307-2-3. s. 1242–1252. Vis sammendrag

  This paper presents techniques for development of virtual prototypes of hydraulically actuated multibody systems, specifically an offshore knuckle boom crane is considered. Both a flexible and rigid body model of the mechanical system is established in order to demonstrate the importance of including the flexibility of the structural components. The virtual prototype also includes a model of the hydraulic system with pressure compensated proportional directional valves, counter balance valves, cylinders and motors with planetary gearboxes as the main components. Initial simulation results are presented and methods for validation of the virtual prototype are discussed along with its applications.

• Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2011). Tool Point Control of Material Handling Crane in Marine Operations. I Singh, Maneesh; Raj B. K. N., Rao & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 0-9541307-2-3. s. 1233–1241. Vis sammendrag

  In the current paper tool point control of hydraulically actuated manipulators is investigated. The considered application is a mobile loader crane. It is modeled as a planar mechanism with three degrees of freedom. In previous work a path planner has been developed that handles the redundancy by means of power consumption minimization while observing the different saturation phenomena associated with hydraulic actuation of mobile machinery. In this way a reference velocity is continuously computed and served to the controller that determines the optimal cylinder actuation. However, since one of the main competition parameters for mobile loader cranes is low weight it is clear that the deflection of the tool point caused by structural flexibility is something that cannot be ignored. In this paper this problem is handled by adding a correction procedure to the path planner that effectively reduces the trajectory error. The method calls for increased instrumentation in the shape of strain gauge measurements at a number of strategic points on the structure.

• Hansen, Michael Rygaard & Ottestad, Morten (2011). Friction Compensation in Hydraulic Cylinders. I Singh, Maneesh; Raj B. K. N., Rao & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 0-9541307-2-3. s. 1225–1232. Vis sammendrag

  This paper is concerned with friction compensation of hydraulic cylinders. A simplified model of an offshore drilling heave compensator is used as design study. The heave compensator includes the typical characteristics encountered in offshore motion control of hydraulically actuated equipment: wave induced heave motion, friction in one or more main hydraulic cylinders and a combination of fixed and heave motion references. A friction compensation scheme is proposed that estimates a friction force from cylinder travel and velocity feedback. Further, any main cylinder force variations caused by the passive compensation system is included in the active compensation force. The control element is a servohydraulic system consisting of two double acting hydraulic cylinders, a high response servo valve and a constant pressure supply. The servo valve inner position feedback loop is modeled as second order system and the compensation force feedback loop is managed by a PI-controller that computes the spool reference opening from the deviation in reference and actual compensation force. A special purpose time domain simulation model is used to examine the importance of friction estimation and valve bandwidth. A Stribeck function is used to simulate the actual friction of the main hydraulic cylinder.

• Henriksen, Jan; Bak, Morten Kollerup & Hansen, Michael Rygaard (2011). A Method for Finite Element Based Modeling of Flexible Components in Time Domain Simulation in Knuckle Boom Crane. I Singh, Maneesh; Raj B. K. N., Rao & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 0-9541307-2-3. s. 1215–1224. Vis sammendrag

  In this paper emphasis is on modeling of the flexibility of the different main structural components of an offshore knuckle boom crane. The modeling approach uses results from finite element analysis of the structural components to calibrate a multibody dynamic model of the crane. The calibration is a parameter identification that minimizes the deviation between the static and dynamic behavior of the finite element model of the beam like jibs of the crane with that of lumped beam models. The latter approach allows for an efficient simulation of tool point control schemes that takes into account all important structural deflections and vibrations.

• Ottestad, Morten; Nilsen, Nico & Hansen, Michael Rygaard (2011). A Method for Friction Control in Hydraulic Cylinders. I Singh, Maneesh; Raj B. K. N., Rao & Liyanage, Jayantha Prasanna (Red.), Proceedings of the 24th International Congress on Condition Monitoring and Diagnostics Engineering Management (COMADEM2011). COMADEM International. ISSN 0-9541307-2-3. s. 817–823. 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.

• 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.
• Sævik, Svein; Larsen, Carl Martin; Sten, Ronny & Hansen, Michael Rygaard (2010). Force Variations on Heave Compensating System for Ultra-Deepwater Drilling Risers. I Chen, Gang (Red.), 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) : Shanghai, China, June 6-11, 2010. The American Society of Mechanical Engineers (ASME). ISSN 978-0-7918-3873-0.
• Langer, Thomas; Christensen, Brian B; Mouritsen, Ole Østergaard & Hansen, Michael Rygaard (2010). Optimization of Front Axle Suspension System of Articulated Dump Truck. I Klodowski, Adam (Red.), The First Joint International Conference on Multibody System Dynamics [Recurs electrònic] : Lappeenranta, Finland, May 25 - 27, 2010. Lappeenranta University of Technology. ISSN 9789522147783. Vis sammendrag

  Manufacturers of construction machinery are challenged to accommodate legal requirements on the vibration exposure associated with their products. For such machines a crucial performance parameter is the whole body vibration level that the operator is subjected to. This paper presents results from ongoing research collaboration between Hydrema Produktion A/S, Aalborg University and the University of Agder on comfort improvement. The main goal of the research project is to improve ride comfort of articulated construction machinery by use of multibody simulation models. In this paper the application that has been subjected to comfort improvement is a two axle articulated dump truck. The comfort has been in terms of whole body vibration exposure and the overall improvement has been made possible by adding front axle suspension. However, a hydraulic stabilizing system between the tractor and trailer of the machine and the varying load distribution when turning the steering wheel has revealed a non-trivial task of sizing the new suspension system in an optimal way. Hydraulic accumulators and valves are used as suspension elements. The topology of the suspension frame is given together with a work cycle used to evaluate the whole body vibrations. By use of a multibody simulation model of the dump truck the whole body vibration exposure has been computed using the predefined work cycle as model input. The design parameters comprise the components of the hydraulic subsystem of the suspension, i.e., the size of the hydraulic accumulators and the initial gas pressure as well as the size of the damping orifices. The design criteria has been the comfort as evaluated from the typical work cycle with a number of side constraints such as availability of components, available space, collision avoidance and design rules given by the supplier of accumulators. A non-gradient optimization routine has been applied to determine the optimal design, i.e., the design with the best possible ride comfort in terms of whole body vibrations that does not violate any of the constraints. Some variables have been treated as discrete such as the accumulator volume. In general, the results have been encouraging and may be used directly as guidelines in both current and future design.

• Sørensen, Søren Emil; Hansen, Michael Rygaard & Ebbesen, Morten Kjeld (2010). An Experimentally Verified Model for Time Domain Simulation of Large Scale Material Handling Chains. I Klodowski, Adam (Red.), The First Joint International Conference on Multibody System Dynamics [Recurs electrònic] : Lappeenranta, Finland, May 25 - 27, 2010. Lappeenranta University of Technology. ISSN 9789522147783. Vis sammendrag

  A loop sorter system for sortation of medium size items is constructed as a closed chain of carts is running in a customer defined track. The complex mechatronic system makes the use of simulation models a vital tool in order to analyze and further improve the dynamic performance of the loop sorter. Theory in unconstrained rigid multibody dynamics is utilized to develop a time domain simulation model of the dynamics in the chain of carts. The contact between carts and between carts and track is modeled through the use of a penalty formulation. Two contact models of the wheel contacts are tested. A combination of analytic and numeric contact search algorithms is utilized to determine contact between the track and the wheels. Verification of the developed chain model is done by comparing experimental obtained data of forces in different contact points of the carts with corresponding data from conducted simulations. Data for the verification is obtained via a customized transducer cart on different loop sorter test layouts. The transducer cart is equipped to measure forces in all wheel contacts and forces in the links between the carts. Forces are measured for one lap on each test layout at the normal operation speed. Two different loop sorter layouts are used for verification of the presented multibody model. Accordance between measured and simulated data shows promising results. Forces in the joint between carts have a normal root mean square deviation that is less then 10%. Forces on the wheels also match the measured data well although the combination of static and impact contact makes it hard for the utilized contact models to compute forces correctly in both situations. Additional research on the wheel contact model may induce further improvements to the wheel contact forces.

• Ottestad, Morten; Haland, Kjell Olav & Hansen, Michael Rygaard (2010). A model based approach to design of passive and active heave compensation of crown mounted drilling equipment. Proceedings of the IASTED International Conference on Modelling, Identification, and Control (MIC). ISSN 1025-8973. s. 128–135. Vis sammendrag

  The current work is on passive and active heave compensation of offshore drilling equipment. The main purpose of heave compensation while drilling from vessels or semisubmersible platforms is to maintain the drilling operation unaffected by the wave induced motion. Specifically, this paper deals with the problem of bit-lift-off, i.e., the situation where the drillbit looses contact with the formation. The investigated system is of an existing crown mounted compensator and the passive heave compensation scheme is described including the usefulness of force equalizing cylinders. Also, an approach to the design of a controller for the active heave compensation system is put forward that is based on the sensor signals available. A detailed model of the crown mounted compensator is developed that includes mechanics, hydraulics and pneumatics. It is developed in the commercial modeling environment of SimulationX? and used together with a worst case scenario as evaluation tool for the proposed control scheme.

• Hansen, Michael Rygaard & Andersen, Torben Ole (2010). Controlling a negative loaded hydraulic cylinder using pressure feedback. Proceedings of the IASTED International Conference on Modelling, Identification, and Control (MIC). ISSN 1025-8973. s. 242–248. Vis sammendrag

  This paper is concerned with the inherent oscillatory nature of pressure compensated velocity control of a hydraulic cylinder subjected to a negative load and suspended by means of an over-center valve. Initially, a linearized stability analysis of such a hydraulic circuit is carried out clearly showing that without extra measures such a system will be unstable in a substantial part of the cylinder stroke. The stability criterion is expressed in hard quantities: Cylinder volumes, cylinder area ratio and overcenter valve pilot area ratio. A pressure feed back scheme that has as target to maintain the high pass filtered pressure gradient equal tozero is introduced. It yields lead compensation with a markedly improved performance. The sizing of the filter is described taking into account the bandwidth of the directional control valve. The suggested control scheme is implemented and examined in a non-linear time domain simulation model validating the linear stability analysis.

• Ebbesen, Morten Kjeld & Hansen, Michael Rygaard (2010). Correction Scheme for Tool Point Velocity Control of a Flexible Hydraulically Actuated Manipulator. Proceedings of the IASTED International Conference on Modelling, Identification, and Control (MIC). ISSN 1025-8973. s. 298–305. Vis sammendrag

  In the current paper tool point control of hydraulically actuated manipulators is investigated. The considered application is a mobile loader crane. It is modeled as a planar mechanism with three degrees of freedom. In previous work a path planner has been developed that handles the redundancy by means of power consumption minimization while observing the different saturation phenomena associated with hydraulic actuation of mobile machinery. In this way a reference velocity is continuously computed and served to the controller that determines the optimal cylinder actuation. However, since one of the main competition parameters for mobile loader cranes is low weight it is clear that the deflection of the tool point caused by structural flexibility is something that cannot be ignored. In this paper this problem is handled by adding a correction procedure to the path planner that effectively reduces the trajectory error. The method utilizes only two of the three degrees of freedom and emphasis is on vertical adjustment and the simulation results show highly encouraging results. The method calls for increased instrumentation in the shape of strain gauge measurements at a number of strategic points on the structure.

• Langer, Thomas; Hansen, Michael Rygaard & Mouritsen, Ole Østergaard (2010). A Tire Model for Off-Highway Vehicle Simulation on Short Wave Irregular Terrain. SAE technical paper series. ISSN 0148-7191. 1(1). Vis sammendrag

  Manufacturers of construction machinery are challenged in several ways concerning dynamic loads. Considering off-highway dump trucks that travel through high amplitude short wave irregular terrain with considerable speed two aspects concerning dynamics are important. The first is the legal requirements that prescribe the maximum limit on the vibration exposure on the operator which is a measure for ride comfort. The second is the importance of knowing the dynamic loading of the structural parts. In order to use the wide variety of computer-aided design tools to size and optimize mechanical joints, spring-damper elements and the welded structures it is crucial to have information on the time history of the loads. For trucks carrying payloads the most important load contribution is undoubtedly the reaction forces between terrain and tires. By use of virtual prototypes it is possible to evaluate accelerations of different machine parts and reaction forces in joints. Hence it is possible to find loads for sizing components and structures and prevent fatigue, and also the influence of design changes on ride comfort can be evaluated. This poses a non-trivial challenge: To be able to describe the tire ground interaction for big off-road tires on short wave irregular terrain. In this paper a simple tire model combining the well known slip theory and a displaced volume approach is presented. A non-gradient optimization routine is applied for parameter identification by minimizing the difference between simulated data and experimental data obtained from full vehicle testing. The experimental work is carried out by letting a dump truck pass a set of well defined obstacles. Based on the obtained agreement between simulated and measured results the tire model is considered suitable for describing the tire ground interaction and, subsequently, reliable for a model based evaluation of the dynamic loads.

• Pedersen, Mikkel Melters; Mouritsen, Ole Østergaard; Hansen, Michael Rygaard; Andersen, Jes & Wenderby, Jimmi (2010). Comparison of Post Weld Treatment of High Strength Steel Welded Joints in Medium Cycle Fatigue. Welding in the World. ISSN 0043-2288. 54(07.aug). Vis sammendrag

  This paper presents a comparison of three post-weld treatments for fatigue life improvement of welded joints. The objective is to determine the most suitable post-weld treatment for implementation in mass production of certain crane components manufactured from very high-strength steel. The processes investigated are: burr grinding, TIG dressing and ultrasonic impact treatment. The focus of this investigation is on the so-called medium cycle area, i.e. 10 000-500 000 cycles and very high stress ranges. In this area of fatigue design, the use of very high-strength steel becomes necessary, since the stress range can exceed the yield-strength of ordinary structural steel, especially when considering positive stress ratios (R > 0). Fatigue experiments and qualitative evaluation of the different post-weld treatments leads to the selection of TIG dressing. The process of implementing TIG dressing in mass production and some inherent initial problems are discussed. The treatment of a few critical welds leads to a significant increase in fatigue performance of the entire structure and the possibility for better utilization of very high-strength steel.

• Pedersen, Mikkel Melters; Mouritsen, Ole Østergaard; Hansen, Michael Rygaard; Andersen, J. & Wenderby, Jimmi (2010). COMPARISON OF POST-WELD TREATMENT OF HIGH-STRENGTH STEEL WELDED JOINTS IN MEDIUM CYCLE FATIGUE. Welding in the World. ISSN 0043-2288. 54(07.aug). Vis sammendrag

  This paper presents a comparison of three post-weld treatments for fatigue life improvement of welded joints. The objective is to determine the most suitable post-weld treatment for implementation in mass production of certain crane components manufactured from very high-strength steel. The processes investigated are: burr grinding, TIG dressing and ultrasonic impact treatment. The focus of this investigation is on the so-called medium cycle area, i.e. 10 000-500 000 cycles and very high stress ranges. In this area of fatigue design, the use of very high-strength steel becomes necessary, since the stress range can exceed the yield-strength of ordinary structural steel, especially when considering positive stress ratios (R > 0). Fatigue experiments and qualitative evaluation of the different post-weld treatments leads to the selection of TIG dressing. The process of implementing TIG dressing in mass production and some inherent initial problems are discussed. The treatment of a few critical welds leads to a significant increase in fatigue performance of the entire structure and the possibility for better utilization of very high-strength steel.

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• Gøytil, Petter Hansen; Hansen, Michael Rygaard & Padovani, Damiano (2022). Linear Time-Invariant Modelling of Electrohydraulic Cylinders.
• 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. [Internett]. Apple Podcasts. 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.

• 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.
• Husveg, Rune; Husveg, Trygve; van Teeffelen, Niels; Ottestad, Morten & Hansen, Michael Rygaard (2017). Improving Separation of Oil and Water Using a Novel Coalescing Centrifugal Pump.
• Pedersen, Henrik C.; Andersen, Torben Ole & Hansen, Michael Rygaard (2016). Guidelines for Properly Adjusting Pressure Feedback in Systems with Over-Centre Valves.
• Husveg, Rune; Husveg, Trygve; van Teeffelen, Niels; Ottestad, Morten & Hansen, Michael Rygaard (2016). Performance of a Coalescing Multistage Centrifugal Produced Water Pump with Respect to Water Characteristics and Point of Operation.
• 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.
• 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.
• Henriksen, Jan & Hansen, Michael Rygaard (2013). FEM simulation of cold deforming pipe into flange.
• Pedersen, Mikkel Melters; Mouritsen, Ole Østergaard; Hansen, Michael Rygaard & Andersen, Jes (2010). Experience with the Notch Stress Approach for Fatigue Assessment of Welded Joints. I Barsoum, Zuheir (Red.), Z. Barsoum and J. Samuelsson (ed.) Proc. of Swedish Conference on Lightweight Optimised Welded Structures, LOST. Royal Institute of Technology Aeronautical and Vehicle Engineering. ISSN 978-91-7415-608-9. s. 122–133. Vis sammendrag

  In this paper, fatigue assessment using the notch stress approach is discussed based on re-analysis of many fatigue test results and experience from practical application. Three topics are treated; evaluation of the fatigue strength for as-welded details (FAT225) in the notch stress system, problems regarding assessment of mild-SCF details and a novel proposal for extension of the notch stress approach for use with post-weld treated details.

• Moslått, Geir-Arne; Meisfjordskar, Anders; Hansen, Michael Rygaard & Padovani, Damiano (2020). Motion Control of Hydraulic Winch Using Variable Displacement Motors. Universitetet i Agder. ISSN 978-82-8427-008-1. Fulltekst i vitenarkiv

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