| 1. |
- Gustavsson, Ingvar, et al.
(författare)
-
Chapter 15 – The VISIR Open Lab Platform
- 2011
-
Ingår i: InternetAccessible Remote Laboratories. - : IGI Global. - 9781613501863 - 9781613501870 ; , s. 294-317
-
Bokkapitel (refereegranskat)abstract
- The VISIR Open Lab Platform designed at the Department of Electrical Engineering (AET), the Blekinge Institute of Technology (BTH), Sweden, is a platform for opening instructional laboratories for remote access 24/7 with preserved context. VISIR is an acronym for Virtual Instrument Systems in Reality. In VISIR laboratories, students perform physical experiments and laboratory work remotely. A unique interface gives them the feeling of “being there.” The platform software is published under a GPL license, and other universities, schools, et cetera, are invited use it to open their laboratories and to participate in further research and development. Apart from BTH, five universities in Europe have set up VISIR online laboratories for electrical experiments and the Indian Institute of Technology Madras in India will set up one soon. A VISIR community has been established. Common projects are initiated, and the sharing of learning material is being discussed. This chapter is a general introduction to VISIR and its possibilities.
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| 2. |
- Gustavsson, Ingvar, et al.
(författare)
-
The VISIR Open Lab Platform
- 2011
-
Ingår i: Internet Accessible Remote Laboratories. - : IGI Global. - 9781613501863 ; , s. 294-317
-
Bokkapitel (refereegranskat)abstract
- The VISIR Open Lab Platform designed at the Department of Electrical Engineering (AET), the Blekinge Institute of Technology (BTH), Sweden, is a platform for opening instructional laboratories for remote access 24/7 with preserved context. VISIR is an acronym for Virtual Instrument Systems in Reality. In VISIR laboratories, students perform physical experiments and laboratory work remotely. A unique interface gives them the feeling of “being there.” The platform software is published under a GPL license, and other universities, schools, etc., are invited use it to open their laboratories and to participate in further research and development. Apart from BTH, five universities in Europe have set up VISIR online laboratories for electrical experiments and the Indian Institute of Technology Madras in India will set up one soon. A VISIR community has been established. Common projects are initiated, and the sharing of learning material is being discussed. This chapter is a general introduction to VISIR and its possibilities.
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| 3. |
- Gustavsson, Ingvar, et al.
(författare)
-
A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid
- 2008
-
Konferensbidrag (refereegranskat)abstract
- The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created two online lab workbenches, one for electrical experiments and one for mechanical vibration experiments, mimicking and supplementing workbenches in traditional labo-ratories. Since some years, the workbenches are used concurrently with on-site ones in regular supervised lab sessions. The students are also free to use them on their own around the clock e.g. for preparation. The electronic workbench can be used simultane-ously by many students. The aim of a project known as VISIR (Virtual Systems in Reality) founded by ASB at the end of 2006, is disseminating the online lab workbenches using open source technologies. The goal is to create a template for a grid laboratory where the nodes are workbenches for electrical ex-periments, located at different universities. This paper focuses on standards, pedagogical aspects, and measurement procedure requirements.
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| 4. |
- Gustavsson, Ingvar, et al.
(författare)
-
A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid
- 2008
-
Ingår i: International Journal of Online Engineering. - 1868-1646 .- 1861-2121. ; 4:2, s. 12-16
-
Tidskriftsartikel (refereegranskat)abstract
- The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created two online lab workbenches; one for electrical experiments and one for mechanical vibration experiments, mimicking and supplementing workbenches in traditional laboratories. For several years now, the workbenches have been used concurrently with on-site ones in regular, supervised lab sessions. The students are encouraged to use them on a 24/7 basis for example, in preparation for supervised sessions. The electronic workbench can be used simultaneously by many students. The aim of a project known as VISIR (Virtual Systems in Reality) founded by ASB at the end of 2006, is to disseminate the online lab workbenches using open source technologies. The goal is to create a template for a grid laboratory where the nodes are workbenches for electrical experiments, located at different universities. This paper focuses on standards, pedagogical aspects, and measurement procedure requirements.
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| 5. |
- Gustavsson, Ingvar, et al.
(författare)
-
Gör ingenjörsutbildningen attraktiv genom att öka det experimentella inslaget
- 2008
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Många idéer till hur man skall få fler ungdomar att välja ingenjörsyrket har diskuterats och provats men tyvärr utan större framgång. En ny ingrediens kan vara att öka det experimentella inslaget, något som ändå måste göras av andra skäl, varav ett är hållbar utveckling. Det är känt att genom experiment kan man lära känna naturens principer. Ingenjörer är de yrkesutövare som konstruerar många av de nyttigheter som bär upp vår civilisation. Vi använder teorier/modeller som verktyg, men dessa räcker inte alltid, utan man måste få experimentera och bygga prototyper samt verifiera. Den allmänna meningen bland lärare och andra initierade bedömare har hittills varit att laborationer är nödvändiga men lite sägs om vad de förväntas ge. Få lärosäten producerar ingenjörer med dokumenterad erfarenhet av laborativt arbete. Lärandemål för laborationer har saknats men de senaste åren har sådana börjat definieras. Under senare decennier har undervisningsanslagen heller inte räknats upp i takt med studenttillströmningen. Eftersom laborativ undervisning är kostsam per student har lärosätena valt att reducera antalet laborationer, men Internets intåg ger nya möjligheter att öppna laboratorier för fjärrstyrning och låta studenter experimentera själva, utan risk att skada sig själva eller utrustningen. Studenter får således nya möjligheter att organisera sina studier i enlighet med vad Bolognaprocessen kräver och lärosäten kan utnyttja laboratorierna mera effektivt. Vi kan öka det experimentella inslaget i undervisningen. Internationellt samarbete både avseende läromedel och experimentell utrustning ser ut att ge möjlighet att sänka de löpande kostnaderna till den grad att det experimentella inslaget kan ökas väsentligt inom befintliga anslagsramar, även om den initiala kostnaden för den forskning som först krävs då inte är inräknad. Avdelningen för signalbehandling, ASB, vid BTH har öppnat övningslaboratorier för ellära och mekaniska vibrationsexperiment för fjärrstyrning. Båda används i reguljär undervisning sedan några år. Ett unikt användargränssnitt gör det möjligt att från valfriplats styra och manövrera experimentutrustning på samma sätt som i laboratorielokalerna. Studenterna får möjlighet att i förväg bekanta sig med instrumenten och utföra föreskrivna experiment enskilt eller tillsammans med andra. Dessa öppna laboratorier ger möjlighet att inkludera praktiska uppgifter i skriftliga tentamina, förutsatt att examination kan ske i datorsal, varvid erfarenhet av laborativt arbete enkelt kan examineras för varje enskild student. ASB har startat ett projekt VISIR (Virtual Systems in Reality) som handlar om att sprida BTH:s öppna laboratoriekoncept och formulera standarder inom området. Tillhörande programvara har publicerats som öppen källkod. BTH bjuder in andra lärosäten att delta i projektet och i dess vidareutveckling mot internationella standarder. Två internationella universitet har redan öppnat kopior av elläralaboratoriet och deltar aktivt i vidareutvecklingen. ASB har nyligen blivit inbjuden av ett universitet i Australien att delta ett projekt med titeln ”Enriching Student Learning Experience through International Collaboration in Remote Laboratories”. Detta beviljade projekt är ett resultat av nya pedagogiska möjligheter, som diskuteras i detta bidrag. ASB söker samarbete med pedagoger och andra forskare intresserade av experimentella inslag i ingenjörsutbildningen. Lärandemål för laborativt arbete, öppna laboratorier och internationellt samarbete kan bli ingredienser i en moderniserad och attraktiv ingenjörsutbildning.
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| 6. |
- Gustavsson, Ingvar, et al.
(författare)
-
Remote Operation and Control of Traditional Laboratory Equipment
- 2006
-
Ingår i: International Journal of Online Engineering. - 1868-1646 .- 1861-2121. ; 2:1, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- Physical experiments are indispensable for developing skills to deal with physical processes and instrumentation. The Internet provides new possibilities for universities and other teaching organizations to share laboratories and increase the number of lab sessions without incurring any increase in cost. Blekinge Institute of Technology in Sweden has opened a traditional electronics laboratory for remote operation and control 24/7; it is the first of its kind. The laboratory is equipped with a unique virtual interface enabling students to recognize on their own computer screen the desktop instruments and the breadboard they have already used in the local laboratory. The research is focused on what is perceived to be the greatest challenge, i.e. to give the student laboratory experience that is as genuine as possible despite the lack of direct contact with the actual lab hardware at the same time as it allows the teacher to use existing equipment and teaching material. The goal is to produce an open international standard.
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| 7. |
- Gustavsson, Ingvar, et al.
(författare)
-
Telemanipulator for Remote Wiring of Electrical Circuits
- 2008
-
Konferensbidrag (refereegranskat)abstract
- Nowadays, students want extended access to learning resources and increased freedom to organize their learning activities. Remote access to laboratories enables students to perform physical experiments on their own 24/7. It is easy to control most electronic instruments remotely but some kind of telemanipulator is often required. The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created an online lab workbench for electrical experiments, mimicking and supplementing workbenches in local laboratories. Students being at home can, for example, use the online workbench in order to prepare themselves for supervised lab sessions and/or participate in such sessions taking place in a local laboratory. A virtual breadboard is used to control a telemanipulator (switching matrix) performing the circuit wiring. Together with virtual front panels depicting the front panels of the desktop instruments, it gives distant students the impression that they are working in a real laboratory. This paper describes the virtual breadboard and switching matrix combination, which can be used in many switching applications.
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| 8. |
- Gustavsson, Ingvar, et al.
(författare)
-
The VISIR project – an Open Source Software Initiative for Distributed Online Laboratories
- 2007
-
Konferensbidrag (refereegranskat)abstract
- Blekinge Institute of Technology (BTH) in Sweden has started a project known as VISIR (Virtual Instrument Systems in Reality) together with National Instruments in USA and Axiom EduTech in Sweden to disseminate an online laboratory concept created at BTH using open source technologies in collaboration with other universities and organizations. The concept is about adding a remote operation option to traditional instructional laboratories to make them more accessible, irrespective of whether the students are on campus or mainly off campus. The BTH option is equipped with a unique interface enabling students to recognize on their own computer screen the instruments and other equipment most of them have previously used in the local laboratory. The first remote control option implemented is for an electronics laboratory and the second one is for a signal processing laboratory with emphasis on mechanical vibration experiments. The electronics lab option features remote circuit wiring using a virtual breadboard and a relay switching matrix combination. The goal is an international standard, enabling teams worldwide to expand and develop jointly this powerful approach into distributed online laboratories by using standardized software such as IVI (Interchangeable Virtual Instruments) and equipment platforms such as PXI (PCI eXtensions for Instrumentation) and LXI (LAN eXtensions for Instrumentation).
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| 9. |
- Åkesson, Henrik, et al.
(författare)
-
Remote Experimental Vibration Analysis of Mechanical Structures over the Internet
- 2005
-
Konferensbidrag (refereegranskat)abstract
- Experimental vibration analysis is of significant importance for e.g. the automobile and aircraft industry. It provides detailed information concerning the actual dynamic properties of vibration, structures, etc. Commonly, information from experimental vibration analysis is used in the development or modification of structures, processes, etc. to obtain for instance a required dynamic behaviour. It usually involves analysis methods such as; spectrum analysis, correlation analysis, experimental modal analysis and operating deflection shapes analysis (ODS). Large experience is generally required to obtain reliable results with these methods. The best way to acquire such experience is to spend many hours in a laboratory supervised by an expert teacher. However, in engineering education the experimental resources are limited and the traditional way of conducting vibration experiments is to participate in time limited scheduled lab sessions. Internet, however, provides the opportunity for engineering students to access the practical and theoretical knowledge advancement in experimental vibration analysis that is highly attractive for the industry. Laboratory exercises in, for example, experimental vibration analysis and signal processing courses, can now be performed remotely using real equipment. Advanced vibration experiments have been conducted over the Internet at Blekinge Institute of Technology, Sweden; the experiments have been carried out using experimental hardware located in a small closed laboratory. Exercises are adapted to on-campus students as well as distance learning engineers in continuing education programs. A new possibility to directly integrate vibration experiments into lectures given by expert teachers appears and after each lecture the students can repeat and elaborate on the experiments. Thus, enabling the students to carry out the experiments within a course at home using the time they require for sufficient comprehension. In this paper the remote experimental vibration analysis laboratory and its possibilities will be presented.
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| 10. |
- Åkesson, Henrik, et al.
(författare)
-
Vibration Analysis of Mechanical Structures over the Internet Integrated into Engineering Education
- 2006
-
Konferensbidrag (refereegranskat)abstract
- Experimental vibration analysis is one of the most important tools for analyzing dynamic properties of mechanical structures. The information from experimental vibration analysis is used in the development of products to obtain a required dynamic behavior, or for instance classify vibration problems in different public, industrial environments etc. In order to carry out such experiments with high quality, knowledge about different analysis methods is of great importance. Also a large experimental experience is required to obtain reliable results as in any field. In engineering education experiment using real mechanical structures and equipment is of significance for the learning process. In traditional university laboratories students conduct experiments under the supervision of an instructor. However, a trend towards decreasing investments to maintain these laboratories can be seen all over the world and instead an increase of simulations or theoretical experiments is replacing these hands on experiments due to cost. Blekinge Institute of Technology (BTH), Sweden provide the opportunity for engineering students to remotely access the practical and theoretical knowledge advancement in experimental vibration analysis that is highly attractive for the industry. Remote laboratory exercises are to day a reality at BTH and are a complement to on-campus laboratory experiments, increasing the availability of the instruments. Previously vibration experiments have been conducted over the Internet at BTH, using experimental hardware located in a small closed laboratory. A further step towards a more user-friendly interface has been developed, increasing the feeling of being in front of a real instrument instead of a virtual front panel. This paper presents a new remote vibration laboratory and how remote experimental vibration analysis has been integrated in the engineering education as a complement to ordinary lessons and experiments in traditional laboratories.
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| 11. |
- Adolfsson, Stefan, et al.
(författare)
-
A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding
- 1997
-
Konferensbidrag (refereegranskat)abstract
- This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.
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| 12. |
|
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| 13. |
- Adolfsson, Stefan, et al.
(författare)
-
On-line quality monitoring in short : circuit gas metal arc welding
- 1999
-
Ingår i: Welding Journal. - New York,N.Y. : American welding society. - 0043-2296. ; 78:2, s. 59S-73S
-
Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problems involved in the automatic monitoring of the weld quality produced by robotized short-arc welding. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), was used. The algorithm may similarly be viewed as a cumulative sum (CUSUM) type test, and is well-suited to detecting sudden minor changes in the monitored test statistic. The test statistic is based on the variance of the weld voltage, wherein it will be shown that the variance decreases when the welding process is not operating under optimal conditions. The performance of the algorithm is assessed through the use of experimental data. The results obtained from the algorithm show that it is possible to detect changes in weld quality automatically and on-line.
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| 14. |
- Adolfsson, Stefan, et al.
(författare)
-
Quality Monitoring in Robotised Welding using Sequential Probability Ratio test
- 1996
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive sequential probability ratio test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) type test. The test statistics is based upon the variance of the amplitude of the weld voltage. It is shown that the variance of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line
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| 15. |
- Andrén, Linus, et al.
(författare)
-
Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS
- 2003
-
Konferensbidrag (refereegranskat)abstract
- The boring operation is a cumbersome manufacturing process marred by noise and vibration related problems. The manufacturing industry is having trouble with these kinds of metal cutting operations. There exist several approaches to reduce the vibrations in cutting operations in general. Passive tuned dampers in boring bars have been commercially available for some time. An active solution is likely to be more robust to changes in the spectral content, where the passive counterpart have a small operable area, the active solution is able to adapt to these kinds of changes. Active vibration control in boring operations has been proven to be feasible. The algorithm used in the successful experiments was the feedback filtered X-LMS algorithm. This algorithm does however not guarantee a stable behavior, but incorporating a leakage factor will make the algorithm more robust. Power spectral density of boring bar vibration of real cutting experiments show that the leaky filtered X-LMS algorithm is a possible candidate to be a suitable control algorithm. Nyquist diagrams of the controller during operation show that the stability is increased significantly.
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| 16. |
- Andrén, Linus, et al.
(författare)
-
Active Control of Machine Tool Vibrations in External Turning Operations
- 2003
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - 0954-4054 .- 2041-2975. ; 217:6, s. 869-872
-
Tidskriftsartikel (refereegranskat)abstract
- Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezo ceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the anti vibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe provided the mounting arrangement is fairly similar.
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| 17. |
- Andrén, Linus, et al.
(författare)
-
Active Noise Control Experiments in a Fork-lift Truck Cabin
- 2004
-
Konferensbidrag (refereegranskat)abstract
- High comfort for the driver in working vehicles is an important feature as well as a demand from the drivers. Low noise level is an essential factor for the manufacturer to maintain a high standard and comfort of vehicles. In many cases the noise inside the cabin can be related to the engine orders. Hydraulic pumps and fans are also related to the engine but not necessarily integers of the engine order. Passive absorbers are not suitable for the lowest frequencies and one approach is to use an active noise control system to solve the noise problem at low frequencies. In the present experiment loudspeakers were mounted inside the cabin of a fork lift-truck to produce the secondary noise field. To sense the residual noise, microphones were installed close to the driver's head. The aim is to create a zone of reduced noise around the head. Since a large portion of the noise inside the cabin can be related to the engine, an active control system based on a feedforward solution is possible. Experimental results from a feedforward solution of active noise control in a fork-lift truck cabin show that the noise level in the low frequency region can be reduced significantly.
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| 18. |
- Andrén, Linus, et al.
(författare)
-
Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations
- 2004
-
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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| 19. |
- Andrén, Linus, et al.
(författare)
-
Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation
- 2004
-
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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| 20. |
- Andrén, Linus, et al.
(författare)
-
Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation : Correlation to structural Properties
- 2004
-
Ingår i: Mechanical systems and signal processing. - : Academic Press, UK. - 0888-3270 .- 1096-1216. ; 18:4, s. 903-27
-
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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| 21. |
- Andrén, Linus, et al.
(författare)
-
Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars
- 2003
-
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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| 22. |
- Andrén, Linus, et al.
(författare)
-
Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration
- 1999
-
Konferensbidrag (refereegranskat)abstract
- In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construction with integrated high magnetostrictive actuators was used. However, high magnetostrictive actuators generally have a non-linear behavior and it is a well known fact that non-linear properties in the forward path in an active control system is likely to degrade the robustness of the control system. A new generation embedded active tool holder shanks based on piezo ceramic actuators has been developed. Based on spectrum estimates, both coherence spectrum and frequency response function estimates has been calculated for both the old tool holder construction and the new generation active tool holder shank. From the results it follows that the phase delay is smaller and the linearity of the new generation active tool holder shank are superior compared to the old technology. The physical features and properties of the new generation active tool holders are superior to the old tool holder.
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| 23. |
- Bartunek, Josef Ström, et al.
(författare)
-
Adaptive Fingerprint Binarization by Frequency Domain Analysis
- 2006
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a new approach for fingerprint enhancement by using directional filters and binarization. A straightforward method for automatically tuning the size of local area is obtained by analyzing entire fingerprint image in the frequency domain. Hence, the algorithm will adjust adaptively to the local area of the fingerprint image, independent on the characteristics of the fingerprint sensor or the physical appearance of the fingerprints. Frequency analysis is carried out in the local areas to design directional filters. Experimental results are presented.
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| 24. |
- Bartunek, Josef Strom, et al.
(författare)
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Adaptive Fingerprint Image Enhancement with Emphasis on Preprocessing of Data
- 2013
-
Ingår i: IEEE Transactions on Image Processing. - : IEEE. - 1941-0042 .- 1057-7149. ; 22:2, s. 644-656
-
Tidskriftsartikel (refereegranskat)abstract
- This article proposes several improvements to an adaptive fingerprint enhancement method that is based on contextual filtering. The term adaptive implies that parameters of the method are automatically adjusted based on the input fingerprint image. Five processing blocks comprise the adaptive fingerprint enhancement method, where four of these blocks are updated in our proposed system. Hence, the proposed overall system is novel. The four updated processing blocks are; preprocessing, global analysis, local analysis and matched filtering. In the pre-processing and local analysis blocks, a nonlinear dynamic range adjustment method is used. In the global analysis and matched filtering blocks, different forms of order statistical filters are applied. These processing blocks yield an improved and new adaptive fingerprint image processing method. The performance of the updated processing blocks is presented in the evaluation part of this paper. The algorithm is evaluated towards the NIST developed NBIS software for fingerprint recognition on FVC databases.
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| 25. |
- Bartunek, Josef Ström, et al.
(författare)
-
Improved Adaptive Fingerprint Binarization
- 2008
-
Konferensbidrag (refereegranskat)abstract
- In this paper improvements to a previous work are presented. Removing the redundant artifacts in the fingerprint mask is introduced enhancing the final result. The proposed method is entirely adaptive process adjusting to each fingerprint without any further supervision of the user. Hence, the algorithm is insensitive to the characteristics of the fingerprint sensor and the various physical appearances of the fingerprints. Further, a detailed description of fingerprint mask generation not fully described in the previous work is presented. The improved experimental results are presented.
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| 26. |
- Bartunek, Josef Ström, et al.
(författare)
-
Neural Network based Minutiae Extraction from Skeletonized Fingerprints
- 2006
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Human fingerprints are rich in details denoted minutiae. In this paper a method of minutiae extraction from fingerprint skeletons is described. To identify the different shapes and types of minutiae a neural network is trained to work as a classifier. The proposed neural network is applied throughout the fingerprint skeleton to locate various minutiae. A scheme to speed up the process is also presented. Extracted minutiae can then be used as identification marks for automatic fingerprint matching.
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| 27. |
- Berg, Magnus, et al.
(författare)
-
A combined on-line PCA-ICA algorithm for blind source separation
- 2005
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Konferensbidrag (refereegranskat)abstract
- In this paper, we introduce and investigate a method combining principle component analysis (PCA) and independent component analysis (ICA) for blind source separation (BSS). A recursive method for the PCA is applied to meet the demands of a real-time application, and likewise a modified on-line version of the information maximization principle is used. The combined PCA-ICA algorithm, first reduces the dimension of the problem and then separates the signals. Evaluation of the proposed algorithm in a real room shows superior noise suppression capabilities compared to the use of PCA or ICA individually. The proposed algorithm achieves an impressive noise suppression/separation of up to 14 dB with only two microphones. Most importantly this is achieved with negligible distortion of the recovered signal. © 2005 IEEE.
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| 28. |
- Berggren, Magnus, et al.
(författare)
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Analysis of How the Noise Level Depends on Different Activities in a Child Day-Care Center
- 2008
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Konferensbidrag (refereegranskat)abstract
- In child day-care centers the noise level can rise to high levels and in some cases become so high that the people present risk hearing damage. The purpose of this investigation was to study how the noise level depends on the different activities during the day. The study was performed at a child day-care center and 6 children and 5 adult female teachers participated. The participants had a microphone attached next to the ear connected to a wearable digital recorder. A total of 32.5 hours of data was recorded. By listening tests the recorded data could be sorted by activity and by number of people present in the same room as the test subject. Activities were classified as belonging to one of the following: outdoor activity, indoor play, singing, storytelling and gathering. Further, by listening, the data was classified in small group/large group (3 or less/more than 3). The results show that the average noise level (LAeq) for outdoor activity was the highest and was measured to 88.1 dBA (average over 7h52min). Singing was 81.5 dBA (1h26min), indoor play 81.3 dBA (19h21min), storytelling 76.6 dBA (1h09min) and gathering 75.0 dBA (2h44min). The noise level difference between all activities except between singing and indoor play and gathering and storytelling could be verified using t-test (p<0.001). Further, the results showed that the average noise level was 86.6 dBA (14h11min) for the large group and 79.6 dBA (18h21min) for the small group. This difference, of 7.0 dB was statistically validated (p<0.001) using t-test.
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| 29. |
- Berggren, Magnus, et al.
(författare)
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Audio Processing Solution for Video Conference Based Aerobics
- 2010
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Ingår i: 2010 Digest of Technical Papers, International Conference on Consumer Electronics. - Las Vegas : IEEE. - 9781424443147 - 9781424443161 ; , s. 407-408
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Konferensbidrag (refereegranskat)abstract
- In this paper an audio processing solution for video conference based aerobics is presented. The proposed solution leaves the workout music unaltered by separating it from the speech and processing each signal separately. The speech signal processing is also performed at a lower sample rate, which saves computational power. Real time evaluation of the system shows that high quality music as well as a good two-way communication is maintained during the aerobic session.
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| 30. |
- Berggren, Magnus, et al.
(författare)
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Low-complexity network echo cancellation approach for systems equipped with external memory
- 2011
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Ingår i: IEEE Transactions on Audio, Speech, and Language Processing. - : IEEE. - 1558-7916 .- 1558-7924. ; 19:8, s. 2506-2515
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Tidskriftsartikel (refereegranskat)abstract
- Long delays and sparseness characterize impulse responses in telecommunication networks and a vast number of solutions for network echo cancellation have been proposed over the years. In this paper, an approach for detecting dispersive regions of a sparse impulse response and a proportionate normalized least mean square (PNLMS)-based selective updating approach are combined with an adaptive double-talk detector to form a complete solution for echo cancellation. The proposed solution has low computational complexity and is targeted for systems equipped with external memory.
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| 31. |
- Björklund, Svante, 1968-
(författare)
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Signal Processing for Radar with Array Antennas and for Radar with Micro-Doppler Measurements
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radar (RAdio Detection And Ranging) uses radio waves to detect the presence of a target and measure its position and other properties. This sensor has found many civilian and military applications due to advantages such as possible large surveillance areas and operation day and night and in all weather. The contributions of this thesis are within applied signal processing for radar in two somewhat separate research areas: 1) radar with array antennas and 2) radar with micro-Doppler measurements.Radar with array antennas: An array antenna consists of several small antennas in the same space as a single large antenna. Compared to a traditional single-antenna radar, an array antenna radar gives higher flexibility, higher capacity, several radar functions simultaneously and increased reliability, and makes new types of signal processing possible which give new functions and higher performance.The contributions on array antenna radar in this thesis are in three different problem areas. The first is High Resolution DOA (Direction Of Arrival) Estimation (HRDE) as applied to radar and using real measurement data. HRDE is useful in several applications, including radar applications, to give new functions and improve the performance. The second problem area is suppression of interference (clutter, direct path jamming and scattered jamming) which often is necessary in order to detect and localize the target. The thesis presents various results on interference signal properties, antenna geometry and subarray design, and on interference suppression methods. The third problem area is measurement techniques for which the thesis suggests two measurement designs, one for radar-like measurements and one for scattered signal measurements.Radar with micro-Doppler measurements: There is an increasing interest and need for safety, security and military surveillance at short distances. Tasks include detecting targets, such as humans, animals, cars, boats, small aircraft and consumer drones; classifying the target type and target activity; distinguishing between target individuals; and also predicting target intention. An approach is to employ micro-Doppler radar to perform these tasks. Micro-Doppler is created by the movement of internal parts of the target, like arms and legs of humans and animals, wheels of cars and rotors of drones.Using micro-Doppler, this thesis presents results on feature extraction for classification; on classification of targets types (humans, animals and man-made objects) and human gaits; and on information in micro-Doppler signatures for re-identification of the same human individual. It also demonstrates the ability to use different kinds of radars for micro-Doppler measurements. The main conclusion about micro-Doppler radar is that it should be possible to use for safety, security and military surveillance applications.
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| 32. |
- Borgh, Markus, 1983-, et al.
(författare)
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An improved adaptive gain equalizer for noise reduction with low speech distortion
- 2011
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Ingår i: EURASIP Journal on Audio, Speech, and Music Processing. - : Springer. - 1687-4714 .- 1687-4722. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- In high-quality conferencing systems, it is desired to perform noise reduction with as limited speech distortion as possible. Previous work, based on time varying amplification controlled by signal-to-noise ratio estimation in different frequency subbands, has shown promising results in this regard but can suffer from problems in situations with intense continuous speech. Further, the amount of noise reduction cannot exceed a certain level in order to avoid artifacts. This paper establishes the problems and proposes several improvements. The improved algorithm is evaluated with several different noise characteristics, and the results show that the algorithm provides even less speech distortion, better performance in a multi-speaker environment and improved noise suppression when speech is absent compared with previous work.
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| 33. |
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| 34. |
- Borgh, Markus, 1983-, et al.
(författare)
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The Effect of Own Voice on Noise Dosimeter Measurements : A Field Study in a Day-Care Environment, Including Adults and Children
- 2008
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Konferensbidrag (refereegranskat)abstract
- Noise dosimeters are valuable tools in assessing the individual noise dose in the workplace. At non-industrial work places with a high degree of communication, such measurements would include the wearer’s own voice which would be registered as noise. This may not always be desirable. The purpose of this investigation was to study the effect of the wearers own voice in noise dosimeter measurements, and especially the difference between children and adults as test subjects. The study took place at a day-care center and sixteen children and thirteen adult female preschool teachers participated. The participants wore a digital recorder during the day, which recorded the sound signal and vibrations originating from an accelerometer attached to the neck of the test subjects, for distinguishing of whether the subject was speaking or not. Thus, average A-weighted noise levels with and without the influence of the subjects own voice could be obtained. The Leq for the measurements with and without the own voice was 84.6 dBA and 72.2 dBA for the children, respectively, and 79.3 dBA and 70.0 dBA for adults. Student’s t-test showed a significant (p<0.01) difference of 12.4 dBA for children and 9.3 dBA for adults when comparing measurements including and excluding the own voice and also that the difference was significantly larger for children. Thus, the study conclude that the influence from the own voice implied an augmentation of the Leq value and that there is a significant difference between children and adults in how large this augmentation is.
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| 35. |
- Brandt, Anders, et al.
(författare)
-
Cyclostationary Analysis of Boring Bar Vibrations
- 2004
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Konferensbidrag (refereegranskat)abstract
- Internal turning or boring operation is a common metal working process that is usually associated with vibration problems. The vibration problems in internal turning considerably influence important factors such as surface quality, productivity, production costs, etc. In order to gain further understanding of the dynamic metal cutting process, an important early step is to thoroughly classify the vibrations. Boring bar vibrations have previously been proven to be nonstationary when analyzed with traditional methods. For vibrations originating in a combination of a rotating workpiece and random material inhomogeneities, it can be anticipated that the vibrations have cyclostationary properties. Methods for analysis of cyclostationary signals have rendered an increasing interest in the past decade, especially in the telecommunications field. However, very little has been published on the use of these methods in vibration applications. In this paper we show there is strong statistical evidence of cyclostationary behavior in vibrations on an operating boring bar. Methods for estimating the cyclic autocorrelation function and cyclic spectrum for sampled data are developed and results are compared. Some preliminary results from implementing these methods on operating boring bar vibrations are also presented.
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| 36. |
- Claesson, Ingvar, et al.
(författare)
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A Multi-DSP implementation of a Broadband Adaptive Beamformer for use in a Hands-free Mobile Radio Telephone
- 1991
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Ingår i: IEEE Transactions on Vehicular Technology. - New York : Institute of electrical and electronics engineers. - 0018-9545. ; 40:1, s. 194-202
-
Tidskriftsartikel (refereegranskat)abstract
- An implementation of a broadband adaptive array on a multiprocessor digital signal processing (DSP) system for use in a hands-free mobile radio telephone is described. This implementation of a five-microphone adaptive Griffiths-Jim array can handle FIR filters with up to 128 taps behind each microphone at a sampling rate of 8 kHz. The filter structure makes it possible to combine an adaptive array with a noise canceler. The near-field problem has been solved by using focusing, a speech-controlled adaptive algorithm, and a short hourglass. Preliminary measurements indicate a considerable potential for this technique in hands-free mobile telephony. The array gives a 20-30-dB suppression of a broadband jammer covering 300-1100 Hz, even with three reflecting walls surrounding the microphone.
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| 37. |
- Claesson, Ingvar, et al.
(författare)
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A Spatial Filtering Approach to Robust Adaptive Beamforming
- 1992
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Ingår i: IEEE Transactions on Antennas and Propagation. - New York : Institute of electrical and electronics engineers. - 0018-926X. ; 40:9, s. 1093-1096
-
Tidskriftsartikel (refereegranskat)abstract
- This communication treats the problem of controlling the superresolution in adaptive beamformers. A straightforward method is presented that works for both narrow-band and broad-band arrays. The method is based on forming the blocking matrix in a general sidelobe canceller (GSC) structure using a spatial FIR filter. The suppression of this spatial filter and the implicit noise of the leaky (LMS) algorithm together determine the beamformer.
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| 38. |
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| 39. |
- Claesson, Ingvar, et al.
(författare)
-
Active Control of Machine-Tool Vibration in a Lathe
- 1997
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Konferensbidrag (refereegranskat)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration is a frequent problem, which affects the result of the machining, in particular the surface finish. The tool life is also influenced by the vibrations. When the working environment is considered, noise is frequently introduced by dynamic motion between the cutting tool and the workpiece. By proper machine design, e.g. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control based on the filtered-x LMS-algorithm enables a reduction of the vibration with up to 40 dB at 1.5 kHz and simultaneously with approximately 40 dB at 3 kHz. A significant improvement of the workpiece surface was observed and a substantial improvement of the acoustic noise level was obtained with adaptive control.
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| 40. |
- Claesson, Ingvar, et al.
(författare)
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Adaptive Active Control of Machine-Tool Vibration In a Lathe
- 1998
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Ingår i: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 3:4, s. 155-162
-
Tidskriftsartikel (refereegranskat)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control of tool vibration in the cutting speed direction, based on the filtered-x LMS-algorithm, enables a reduction in vibration, by up to 40 dB at 1.5 kHz, and by approximately 40 dB at 3 kHz. It was also observed that the introduction of leakage in the filtered-x LMS-algorithm improved the stability properties of the feedback control system. A significant improvement in the workpiece surface was observed and a substantial improvement in the acoustic noise level was obtained with adaptive control.
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| 41. |
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| 42. |
- Claesson, Ingvar, et al.
(författare)
-
Cancellation of Humming GSM Mobile Telephone Noise
- 2003
-
Konferensbidrag (refereegranskat)abstract
- A sometimes annoying problem in the most internationally widespread cellular telephone system, the GSM system, is an interfering signal generated by the switching nature of TDMA cellular telephone system. A humming noise originating from the speech frames, equivalent to 160 samples of data corresponding to 20 ms at 8 kHz sampling rate is sometimes clearly audible. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are Notch Filtering, which is performed on a sample-per-sample basis, and Speech Frame Noise Cancellation, which is an alternative method employing correlators and subtraction, similar to Active Noise Control.
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| 43. |
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| 44. |
- Claesson, Ingvar, et al.
(författare)
-
Car Performance of an Adaptive Microphone Array
- 1992
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Konferensbidrag (refereegranskat)abstract
- Hands free input of mobile telephones is often almost impossible due to the noise situation in the car and the channel quality. The authors present a method to enhance the quality using an adaptive microphone array. Measurements show an improvement of the input with approximately 10 dB. Tape results are available for subjective evaluation.
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| 45. |
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| 46. |
- Claesson, Ingvar, et al.
(författare)
-
Device and a method for preventing or reducing vibrations in a cutting tool
- 2007
-
Patent (populärvet., debatt m.m.)abstract
- An arrangement for reducing vibrations in a tool holder (4) with a cutting tool (3) and has a vibration sensor on the tool holder (4) that is connected to a guide unit (11). The tool holder (4) has further two piezo-electric actuators 14 and 15.Under the influence of the vibration sensor (9), the guide unit (11) provides an electric alternating current that is actively guided over time so that the actuators movably affect the tool holder (4) to reduce the vibrations in this. To also be able to dampen transients in the tool holder (4) this is movably connected with a passive dampening arrangement that is independent of the guide unit (11) and that is based on the principle of a springing (8) suspended mass (7). The invention also relates to a method for reducing vibrations. The vibrations in the tool holder are sensed and a corresponding signal is provided to a guide unit that over time provides actively guided signals to the actuators. The tool holder is also passively influenced by a dampening arrangement that is independent of the guide unit.
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| 47. |
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| 48. |
- Claesson, Ingvar
(författare)
-
FFT i ett historiskt perspektiv
- 1997
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Konferensbidrag (refereegranskat)abstract
- Några nedslag i Fouriertransformens historia och FFT:ns ursprung från 1805 och framåt behandlas i denna populära betraktelse. Vi stannar upp ett slag hos Gauss, funderar över vad han gjort för oss ingenjörer och vi avslutar med en del praktiska konsekvenser och tips som är aktuella idag.
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| 49. |
- Claesson, Ingvar
(författare)
-
FFT i ett historiskt perspektiv
- 1997
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Ingår i: SVIB vibrationsnytt. - Täby : Svenska vibrationsföreningen (SVIB). - 0281-6830. ; 14/15:1, s. 11-15
-
Konferensbidrag (refereegranskat)
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| 50. |
- Claesson, Ingvar, et al.
(författare)
-
GSM TDMA Frame Rate Internal Active Noise Cancellation
- 2003
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Ingår i: International Journal of Acoustics and Vibration. - : Int. Inst. Acoustics and Vibration, USA. - 1027-5851 .- 2415-1408. ; 8:3, s. 159-166
-
Tidskriftsartikel (refereegranskat)abstract
- A common problem in the world's most widely-used cellular telephone system, the GSM system, is the interfering signal generated by the switching nature of TDMA cellular telephony in handheld and other terminals. Signals are sent as chunks of data, speech frames, equivalent to 160 samples of data corresponding to 20 ms at sampling rate of 8 kHz. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are 1) notch filtering, which is multiplicative in frequency, and 2) subtractive noise cancellation, which is an alternative method employing correlators. The latter solution is a straigtforward, although somewhat unorthodox, application of "in-wire" active noise control. Since subtraction is performed directly in the time domain, and we have access to the state of the mobile, it is also possible to consider a recurring pause in the interference caused by the idle frame in the transmission, when the mobile listens to other base stations communicating. More complex control algorithms, based on the state of the communication between the handset and the base station, can be utilised.
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