1. |
- Eklund, Petter, 1989-, et al.
(författare)
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A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator
- 2014
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Ingår i: Machines. - Basel, Switzerland : Multidisciplinary Digital Publishing Institute. - 2075-1702.
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Tidskriftsartikel (refereegranskat)abstract
- The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage.
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2. |
- Hultman, Erik, et al.
(författare)
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Robotized Surface Mounting of Permanent Magnets
- 2014
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 2:4, s. 219-232
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Tidskriftsartikel (refereegranskat)abstract
- Using permanent magnets on a rotor can both simplify the design and increase the efficiency of electric machines compared to using electromagnets. A drawback, however, is the lack of existing automated assembly methods for large machines. This paper presents and motivates a method for robotized surface mounting of permanent magnets on electric machine rotors. The translator of the Uppsala University Wave Energy Converter generator is used as an example of a rotor. The robot cell layout, equipment design and assembly process are presented and validated through computer simulations and experiments with prototype equipment. A comparison with manual assembly indicates substantial cost savings and an improved work environment. By using the flexibility of industrial robots and a scalable equipment design, it is possible for this assembly method to be adjusted for other rotor geometries and sizes. Finally, there is a discussion on the work that remains to be done on improving and integrating the robot cell into a production line.
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3. |
- Hultman, Erik, et al.
(författare)
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Six-Degrees-of-Freedom (6-DOF) Work Object Positional Calibration Using a Robot-Held Proximity Sensor
- 2013
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 1:2, s. 63-80
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Tidskriftsartikel (refereegranskat)abstract
- Industrial automation has been recognized as a fundamental key to build and keep manufacturing industries in developed countries. In most automation tasks, knowing the exact position of the objects to handle is essential. This is often done using a positional calibration system, such as a camera-based vision system. In this article, an alternative six-degrees-of-freedom work object positional calibration method using a robot-held proximity sensor, is presented. A general trigonometry-based measurement and calculation procedure, which, step-by-step, adjusts a work object coordinate system to the actual work object position, is explained. For suitable robot tasks and work object geometries, the benefits with the presented method include its robustness, large work area and low investment cost. Some drawbacks can be longer cycle time and its limited capacity to handle unsorted and complicated objects. To validate the presented method, it was implemented in an experimental robot setup. In this robot cell, it was used to calibrate the position of a stator section work object, which is used in the Uppsala University Wave Energy Converter generator. Hereby the function of the positional calibration procedure was validated. Sufficient positioning accuracy for the stator winding task was achieved and theoretically validated based on the experiments.
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4. |
- Lejerskog, Erik, et al.
(författare)
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Detailed Study of Closed Stator Slots for a Direct-Driven Synchronous Permanent Magnet Linear Wave Energy Converter
- 2014
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 2:1, s. 73-86
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to analyze how a permanent magnet linear generator for wave power behaves when the stator slots are closed. The usual design of stator geometry is to use open slots to maintain a low magnetic leakage flux between the stator teeth. By doing this, harmonics are induced in the magnetic flux density in the air-gap due to slotting. The closed slots are designed to cause saturation, to keep the permeability low. This reduces the slot harmonics in the magnetic flux density, but will also increase the flux leakage between the stator teeth. An analytical model has been created to study the flux through the closed slots and the result compared with finite element simulations. The outcome shows a reduction of the cogging force and a reduction of the harmonics of the magnetic flux density in the air-gap. It also shows a small increase of the total magnetic flux entering the stator and an increased magnetic flux leakage through the closed slots.
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5. |
- Hultman, Erik
(författare)
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Introducing robotized stator cable winding to rotating electric machines
- 2022
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- Following environmental concerns and the rapid digitalization of our society, we are currently experiencing an extensive electrification and industrial revolution. High numbers of electric machines thus need to be assembled for varying applications, including vehicle propulsion and renewable energy conversion. Cable winding is an alternative stator winding technology for electric machines that has been utilized for such applications, so far in smaller series or in prototype machines. The presented work introduces the first concept for automated stator cable winding of rotating electric machines. This concept could enable higher production volumes of cable wound machines and a unique flexibility in handling different machines, in line with Industry 4.0. Robotized stator cable winding is evaluated here for five very different rotating machine designs, through simulations and analytical extrapolation of previous experimental winding results. Potential cycle time and assembly cost savings are indicated compared to manual and lower volume conventional automation, while it is not possible to compete in the present form with existing very high-volume conventional winding automation for smaller machines. Future experimental work is pointed out on handling larger winding cables and special machine designs, and on increased robustness and optimization.
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6. |
- Backman, Sofi, et al.
(författare)
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Continuous Control of an Underground Loader Using Deep Reinforcement Learning
- 2021
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Ingår i: Machines. - : MDPI. - 2075-1702. ; 9:10
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Tidskriftsartikel (refereegranskat)abstract
- The reinforcement learning control of an underground loader was investigated in a simulated environment by using a multi-agent deep neural network approach. At the start of each loading cycle, one agent selects the dig position from a depth camera image of a pile of fragmented rock. A second agent is responsible for continuous control of the vehicle, with the goal of filling the bucket at the selected loading point while avoiding collisions, getting stuck, or losing ground traction. This relies on motion and force sensors, as well as on a camera and lidar. Using a soft actor–critic algorithm, the agents learn policies for efficient bucket filling over many subsequent loading cycles, with a clear ability to adapt to the changing environment. The best results—on average, 75% of the max capacity—were obtained when including a penalty for energy usage in the reward.
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7. |
- Baum, Jens, et al.
(författare)
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Applications of Big Data analytics and Related Technologies in Maintenance - Literature-Based Research
- 2018
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 6:54, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Digitalisation is argued to increase the efficiency of maintenance activities in a production system. One consequence of digitalisation is data deluge; this allows data analytics methods and technologies to be used. However, the actual data analytical methods and technologies used may differ, thus leading to many scientific papers on this topic. The purpose of our contribution is to find and cluster scientific papers regarding the implemented approaches relevant for use in production maintenance. Our research is based on a broad, systematic literature review consisting of a two-step search approach combined with additional filtering and classification. Based on the search results, we evaluate and visualise the potential impact of data analytics on the subject of maintenance. The results of this study broadly summarise the research activities in production maintenance, whilst indicating that the impact of data analytics will grow further. Specific methodological approaches are clearly favored
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8. |
- Berbyuk, Viktor, 1953
(författare)
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Weight-Vibration Pareto Optimization of a Triple Mass Flywheel for Heavy-Duty Truck Powertrains
- 2020
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 8:3, 50, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced efficiency of heavy-duty truck powertrains with constraints imposed on noise, vibration, and harshness requires novel solutions for torsion vibrations attenuation. In the paper, the weight-vibration Pareto optimization problem for a novel vibration absorber, a triple mass flywheel, for application in heavy-duty truck powertrains is considered. Global sensitivity analysis and Pareto optimization method are used to design a novel vibration absorber. The optimization method attempts to minimize oscillations of the torque at the transmission input shaft as well as to minimize total mass inertia of the absorber. It is shown that there exists a Pareto front between the measure of the attenuation of oscillations of the torque and the total mass inertia of a triple mass flywheel. The optimized design parameters for the absorber are obtained that provide the best attenuation of oscillations of the torque at the transmission input shaft for dierent mean values of the engine driving torque. The analysis shows real evidence of the feasibility of the application of this concept of vibration absorbers in heavy-duty truck powertrains. It is also shown that optimized design parameters of a triple mass flywheel put this concept in a superior position in comparison with a dual mass flywheel.
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9. |
- Bergagård, Patrik, 1984, et al.
(författare)
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Calculating Restart States for Systems Modeled by Operations Using Supervisory Control Theory
- 2013
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 1:3, s. 116-141
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a supervisory control theory based offline method for calculating restart states in a manufacturing control system. Given these precalculated restart states, an operator can be given correct instructions for how to resynchronize the control system and the manufacturing resources during the online restart process. The proposed method enables restart after unforeseen errors. It is assumed that the control system is modeled by operations and that possible operation sequences emerge through dependencies between the operations. The paper shows how reexecution requirements may be included in the calculation to obtain a correct behavior for the restarted system. In addition, it is shown how to filter out restart states that require less effort for the operator during the online restart, and how to adapt the nominal production to always enable restart in desired restart states.
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10. |
- Dahl, Martin, 1984, et al.
(författare)
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Application of the sequence planner control framework to an intelligent automation system with a focus on error handling
- 2021
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Ingår i: Machines. - : MDPI AG. - 2075-1702. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Future automation systems are likely to include devices with a varying degree of autonomy, as well as advanced algorithms for perception and control. Human operators will be expected to work side by side with both collaborative robots performing assembly tasks and roaming robots that handle material transport. To maintain the flexibility provided by human operators when introducing such robots, these autonomous robots need to be intelligently coordinated, i.e., they need to be supported by an intelligent automation system. One challenge in developing intelligent automation systems is handling the large amount of possible error situations that can arise due to the volatile and sometimes unpredictable nature of the environment. Sequence Planner is a control framework that supports the development of intelligent automation systems. This paper describes Sequence Planner and tests its ability to handle errors that arise during execution of an intelligent automation system. An automation system, developed using Sequence Planner, is subjected to a number of scenarios where errors occur. The error scenarios and experimental results are presented along with a discussion of the experience gained in trying to achieve robust intelligent automation.
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