| 1. |
- Abrahamsson, Johan, 1977-, et al.
(författare)
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High-Speed Kinetic Energy Buffer : Optimization of Composite Shell and Magnetic Bearings
- 2014
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Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 61:6, s. 3012-3021
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.
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| 2. |
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| 3. |
- Castellucci, Valeria, et al.
(författare)
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Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:4, s. 3272-3291
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Tidskriftsartikel (refereegranskat)abstract
- The power production of the linear generator wave energy converter developed at Uppsala University is affected by variations of mean sea level. The reason is that these variations change the distance between the point absorber located on the surface and the linear generator located on the seabed. This shifts the average position of the translator with respect to the center of the stator, thereby reducing the generator output power. A device mounted on the point absorber that compensates for tides of small range by regulating the length of the connection line between the buoy at the surface and the linear generator has been constructed and tested. This paper describes the electro-mechanical, measurement, communication and control systems installed on the buoy and shows the results obtained before its connection to the generator. The adjustment of the line was achieved through a linear actuator, which shortens the line during low tides and vice versa. The motor that drives the mechanical device was activated remotely via SMS. The measurement system that was mounted on the buoy consisted of current and voltage sensors, accelerometers, strain gauges and inductive and laser sensors. The data collected were transferred via Internet to a Dropbox server. As described within the paper, after the calibration of the sensors, the buoy was assembled and tested in the waters of Lysekil harbor, a few kilometers from the Uppsala University research site. Moreover, the performance of the sensors, the motion of the mechanical device, the power consumption, the current control strategy and the communication system are discussed.
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| 4. |
- Hedlund, Magnus, 1986-, et al.
(författare)
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Fast Optimization Methodology for Press-fitted Composite Hollow Cylinder Flywheel Energy Storage
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Ingår i: Composite structures. - 0263-8223 .- 1879-1085.
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Tidskriftsartikel (refereegranskat)abstract
- An optimization strategy for a hollow flywheel energy storage is presented. Several press-fitted shells of anisotropic materials (such as carbon composites) are studied by an analytical model based on a plane stress assumption. The optimization target is stored energy. The optimizer constraints (which were evaluated at full and zero charge level, respectively) were based on strain-based models for fatigue life of composites, and stress-based fatigue life models for high-strength aluminum. A compiled library was built within the scope of this work, and used to run a robust global grid-search optimizing method. The analytical model was compared against a finite element method solution, and the (single-core) library was seen to be at least 5 orders of magnitude faster.
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| 5. |
- Hedlund, Magnus, 1986-, et al.
(författare)
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Reluctance Machine for a Hollow Cylinder Flywheel
- 2017
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- A hollow cylinder flywheel rotor with a novel outer rotor switched reluctance machine (SRM) mounted on the interior rim is presented, with measurements, numerical analysis and analytical models. Practical experiences from the construction process are also discussed. The flywheel rotor does not have a shaft and spokes and is predicted to store 181 Wh/kg at ultimate tensile strength (UTS) according to simulations. The novel SRM is an axial flux machine, chosen due to its robustness and tolerance for high strain. The computed maximum tip speed of the motor at UTS is 1050 m/s . A small-scale proof-of-concept electric machine prototype has been constructed, and the machine inductance has been estimated from measurements of voltage and current and compared against results from analytical models and finite element analysis (FEA). The prototype measurements were used to simulate operation during maximal speed for a comparison towards other high-speed electric machines, in terms of tip speed and power. The mechanical design of the flywheel was performed with an analytical formulation assuming planar stress in concentric shells of orthotropic (unidirectionally circumferentially wound) carbon composites. The analytical approach was verified with 3D FEA in terms of stress and strain.
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| 6. |
- Hedlund, Magnus, 1986-, et al.
(författare)
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Spin-down Losses and Vibration Analysis of a Flywheel Energy Storage System
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Ingår i: Energies. - 1996-1073.
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Tidskriftsartikel (refereegranskat)abstract
- An integrated flywheel prototype designed to store 868 W h at 30 000 rpm with a novel radial flux core-less electric machine was constructed. The rotor was suspended contactlessly on active radial magnetic bearings and passive axial magnetic bearings. This paper describes the system in detail. The rotor was found to be weakly damped (even at standstill) and the magnetic bearings were used to specifically compensate particular eigenfrequencies. The levitation system was then used to experimentally evaluate the vibrations of the rotor, and compared to FEM studies. Spin-down tests were conducted to evaluate levitation system performance.
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| 7. |
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| 8. |
- Kamf, Tobias, 1987-
(författare)
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A Method for Calibrating Work-Piece Orientation : Using a Dual-Axis MEMS Inclinometer
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Ingår i: Robotics and Computer-Integrated Manufacturing. - 0736-5845 .- 1879-2537.
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Tidskriftsartikel (refereegranskat)abstract
- An accelerometer based alignment system designed to align robotic tools and work-pieces in a Cartesian coordinate system is presented, with potential applications within the automated production industry. An overview of the underlying theory, used hardware, micro-controller implementation and performed experiments is presented. The developed theoretical model and prototype hardware is veried against both simulations and experiments, evaluating their performance and practical limitations. For a set of 2000 random initial misalignments with an amplitude in the range of 0° to 10°, the system achieved an alignment accuracy with a 3-sigma bound of 0.023° in the XY plane and 0.14° along the Z-axis. On average the used robot needed 20.86 s to align the used tool to stated accuracy.
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| 9. |
- Kamf, Tobias, et al.
(författare)
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Automated Mounting of Pole-Shoe Wedges in Linear Wave Power Generators-Using Industrial Robotics and Proximity Sensors
- 2017
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- A system for automatic mounting of high tolerance wedges inside a wave power linear generator is proposed. As for any renewable energy concept utilising numerous smaller generation units, minimising the production cost per unit is vital for commercialization. The linear generator in question uses self-locking wedges, which are challenging to mount using industrial robots due to the high tolerances used, and because of the fact that any angular error remaining after calibration risks damaging the equipment. Using two types of probes, mechanical touch probes and inductive proximity sensors, combined with a flexible robot tool and iterative calibration routines, an automatic mounting system that overcomes the challenges of high tolerance wedge mounting is presented. The system is experimentally verified to work at mounting speeds of up to 50mms(-1), and calibration accuracies of 0.25mm and 0.1 degrees are achieved. The use of a flexible robot tool, able to move freely in one Cartesian plane, was found to be essential for making the system work.
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| 10. |
- Kamf, Tobias
(författare)
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Automated Production Technologies and Measurement Systems for Ferrite Magnetized Linear Generators
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The interest in breaking the historical dependence on fossil energy and begin moving towards more renewable energy sources is rising worldwide. This is largely due to uncertainties in the future supply of fossil fuels and the rising concerns about humanity’s role in the currently ongoing climate changes. One renewable energy source is ocean waves and Uppsala University has since the early 2000s been performing active research in this area. The Uppsala wave energy concept is centered on developing linear generators coupled to point absorbing buoys, with the generator situated on the seabed and connected to the buoy on the sea surface via a steel wire. The motion of the buoy then transfers energy to the generator, where it is converted into electricity and sent to shore for delivery into the electrical grid.This thesis will mainly focus on the development and evaluation of technologies used to automate the manufacturing of the translator, a central part of the linear generator, using industrial robotics. The translator is a 3 m high and 0.8 m wide three sided structure with an aluminum pipe at its center. The structure consists of alternating layers of steel plates (pole-shoes) and ferrite magnets, with a total of 72 layers per side. To perform experiments on translator assembly and production, a robot cell (centered on an IRB6650S industrial robot) complimented with relevant tools, equipment and security measures, has been designed and constructed. The mounting of the pole-shoes on the central pipe, using the industrial robot, proved to be the most challenging task to solve. However, by implementing a precise work-piece orientation calibration system, combined with selective compliance robot tools, the task could be performed with mounting speeds of up to 50 mm/s. Although progress has been made, much work still remains before fully automated translator assembly is a reality.A secondary topic of this thesis is the development of stand-alone measurement systems to be used in the linear generator, once it has been deployed on the seabed. The main requirements of such a measurement system is robustness, resistance to electrical noise, and power efficiency. If possible the system should also be portable and easy to use. This was solved by developing a custom measurement circuit, based on industry standard 4–20 mA current signals, combined with a portable submersible logging unit. The latest iteration of the system is small enough to be deployed and retrieved by one person, and can collect data for 10 weeks before running out of batteries. Future work in this area should focus on increasing the usability of the system.The third and final topic of this thesis is a short discussion of an engineering approach to kinetic energy storage, in the form of high-speed composite flywheels, and the design of two different prototypes of such flywheels. Both designs gave important insights to the research group, but a few crucial design faults unfortunately made it impossible to evaluate the full potential of the two designs.
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