| 11. |
- Andrén, Linus
(författare)
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Active suppression of vibration and noise in industrial applications
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, active control technology is about to emerge from the research labs into products in various areas. It has become an attractive method where passive techniques have low impact at low frequencies and adding active control to that part is often an attractive solution. The active control technique has been enabled by the rapid development of digital signal processors over the last decades. The focal point in this thesis is active vibration and noise suppression. Two different industrial applications have been subjected to active control to reduce unwanted disturbances. In cutting operations, active vibration suppression has been applied to both external turning and boring operations with successful results. Turning operations, and in particular boring operations, are typical examples of chatter prone machining. In order to implement active vibration control in boring operations a thourough investigation of the boring process has been made in the first two parts in this thesis. The following two parts of the thesis treat active vibration suppression in external turning operations and in boring operations. The second industrial application treats the noise in a fork-lift truck. In the final part of the thesis, active noise suppression has been implemented in the cabin of a fork-lift truck.
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| 12. |
- Andrén, Linus, et al.
(författare)
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Active Vibration Control of Boring Bar Vibrations
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The boring operation is a cumbersome manufacturing process plagued by noise and vibration-related problems. A deep internal boring operation in a workpiece is a classic example of chatter-prone machining. The manufacturing industry today is facing tougher tolerances of product surfaces and a desire to process hard-to-cut materials; vibrations must thus be kept to a minimum. An increase in productivity is also interesting from a manufacturing point of view. Penetrating deep and narrow cavities require that the dimensions of the boring bar are long and slender. As a result, the boring bar is inclined to vibrate due to the limited dynamic stiffness. Vibration affects the surface finish, leads to severe noise in the workshop and may also reduce tool life. This report presents an active control solution based on a standard boring bar with an embedded piezo ceramic actuator; this is placed in the area of the peak modal strain energy of the boring bar bending mode to be controlled. An accelerometer is also included in the design; this is mounted as close as possible to the cutting tool. Embedding the electronic parts not only protects them from the harsh environment in a lathe but also enable the design to be used on a general lathe as long as the mounting arrangements are relatively similar. Three different algorithms have been tested in the control system. Since the excitation source of the original vibrations, i.e. the chip formation process cannot be observed directly, the algorithms must be constructed on the basis of a feedback approach. Experimental results from boring operations show that the vibration level can be reduced by 40 dB at the resonance frequency of a fundamental boring bar bending mode; several of its harmonics can also be reduced significantly.
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| 13. |
- Andrén, Linus, et al.
(författare)
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Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations
- 2004
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Konferensbidrag (refereegranskat)abstract
- A classical example of chatter prone machining is the boring operation. Turning under conditions with high vibrations in the cutting tool deteriorates the surface finish and may cause tool breakage. Severe noise is also a consequence of the high vibration levels in the boring bar. Active control is one possible solution to the noise and vibration problem in boring operations. In boring operations the boring bar usually have vibration components in both the cutting speed and the cutting depth direction. The introduction of the control force in different angles in between the cutting speed and the cutting depth directions have been investigated. Furthermore, control path estimates produced when the active boring bar was not in contact with the workpiece and during continuous cutting operation are compared. Experimental results indicate that the control force should be introduced in the cutting speed direction. Although the vibrations are controlled in just the cutting speed direction the vibrations in the cutting depth direction are also reduced significantly.
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| 14. |
- Andrén, Linus, et al.
(författare)
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Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation
- 2004
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Ingår i: Mechanical systems and signal processing. - : Academic Press. - 0888-3270 .- 1096-1216. ; 18:4, s. 869-901
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Tidskriftsartikel (refereegranskat)abstract
- Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler-Bernoulli beam model.
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| 15. |
- Andrén, Linus, et al.
(författare)
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Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation : Correlation to structural Properties
- 2004
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Ingår i: Mechanical systems and signal processing. - : Academic Press, UK. - 0888-3270 .- 1096-1216. ; 18:4, s. 903-27
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Tidskriftsartikel (refereegranskat)abstract
- The internal turning operation has a history of being a cumbersome metal working process as vibration in boring operations is usually inevitable. In this article, the deflection shapes and/or mode shapes as well as the resonance frequencies of a boring bar have been put under scrutiny. Three methods have been used in order to investigate dynamic properties of a clamped boring bar: a theoretical Euler-Bernoulli beam model, an experimental modal analysis and an operating deflection shape analysis. \\ The results indicate a correlation between the shapes of the deflection shapes and/or mode shapes produced by the three different analysis methods. On the other hand, the orientation of the forced deflection shapes and/or mode shapes and the resonance frequencies demonstrates differences between the three methods. During continuous cutting, it is demonstrated that the bending motion of the first two resonance frequencies is to a large extent in the cutting speed direction.
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| 16. |
- Andrén, Linus, et al.
(författare)
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Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars
- 2003
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Konferensbidrag (refereegranskat)abstract
- Vibration and noise in boring operations are ubiquitous problems in the workshop. In boring operations, the boring bar is subjected to forces from both the cutting speed and the cutting depth direction. To solve the vibration problem using active techniques would normally require two actuators in order to enable the control of both directions. By mounting one actuator in between the cutting speed and the cutting depth direction it is possible to achieve an active control solution with one actuator. Using only one actuator not only simplifies the control algorithm and saves extra equipment but is also favourable in terms of modifications of the boring bar. The harsh environment in a lathe more or less requires that both sensors and actuators are embedded and sealed into the boring bar. Since the forces that are to be controlled are large, the space needed for the actuator is substantial. Thus using only one actuator will keep the modified boring bar stiffer than a two actuator design. Three boring bars with the actuator mounted at different angles between the cutting speed and the cutting depth directions have been tested. Results from cutting experiments show that the one actuator solution has good potentials to the vibration problem in boring operations.
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| 17. |
- Appelquist, Joakim, et al.
(författare)
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SMILE Revisited
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The mobile service "SMILE" supporting care of the elderly is evaluated from an economic as well as an work practice perspective.
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| 18. |
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Archives of ALGA, volume 1
- 2004
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Volume 1 contains 3 articles: Nail H. Ibragimov, Equivalence groups and invariants of linear and non-linear equations; Nail H. Ibragimov and Sergey V. Meleshko, Linearization of third-order ordinary differential equations; Nail H. Ibragimov, Gazanfer Ünal and Claes Jogreús, Group analysis of stochastic differential systems: Approximate symmetries and conservation laws.
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| 19. |
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Arkiven i forskningens tjänst
- 2003
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Begreppet "forskande lärande" ges en innebörd så som det utvecklades i skolprojektet MIS (Människan i samhällsomvandlingen).
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| 20. |
- Arman, Maria, et al.
(författare)
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Indications of change in life perspective among women with breast cancer admitted to complementary care
- 2001
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Ingår i: European Journal of Cancer Care. - OXFORD : BLACKWELL SCIENCE LTD. - 0961-5423 .- 1365-2354. ; 10:3, s. 192-200
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Tidskriftsartikel (refereegranskat)abstract
- In this study, qualitative content analysis was used in order to understand the reported changes of life perspective in interviews with 59 women with breast cancer who were admitted to complementary care. The aim of this research was to study women's perceived consequences as well as perceived causes of breast cancer and to explore aspects of importance to the women. The material was collected in semistructured interviews from women with breast cancer at different stages of the disease. The women received complementary care at an anthroposophic clinic in Sweden. Findings showed that these women's view of their relationships with others grew more valuable. Their self-confidence and experience of strength improved, and they regarded life as being more enriched. A change in their disposition towards becoming more fragile and low-spirited was experienced as a hardship by the women. Am interesting finding was that the patients described the aetiology of the disease from several interacting perspectives, which also affected their ideas of how to achieve wellbeing and health. The findings support the view that changes of both benefit and harm are present in the experience of breast cancer.
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