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  • 1. Andrén, Linus
    et al.
    Håkansson, Lars
    Active Vibration Control of Boring Bar Vibrations2004Report (Other academic)
    Abstract [en]

    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.

  • 2. Andrén, Linus
    et al.
    Håkansson, Lars
    Brandt, Anders
    Claesson, Ingvar
    Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation2004In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 18, no 4, p. 869-901Article in journal (Refereed)
    Abstract [en]

    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.

  • 3. Andrén, Linus
    et al.
    Håkansson, Lars
    Brandt, Anders
    Claesson, Ingvar
    Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation: Correlation to structural Properties2004In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 18, no 4, p. 903-27Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS2003Conference paper (Refereed)
    Abstract [en]

    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.

  • 5. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Machine Tool Vibrations in External Turning Operations2003In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 217, no 6, p. 869-872Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations2004Conference paper (Refereed)
    Abstract [en]

    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.

  • 7. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars2003Conference paper (Refereed)
    Abstract [en]

    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.

  • 8. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration1999Conference paper (Refereed)
    Abstract [en]

    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.

  • 9. Claesson, Ingvar
    et al.
    Håkansson, Lars
    Active Control of Machine-Tool Vibration in a Lathe1997Conference paper (Refereed)
    Abstract [en]

    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.

  • 10. Claesson, Ingvar
    et al.
    Håkansson, Lars
    Adaptive Active Control of Machine-Tool Vibration In a Lathe1998In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 3, no 4, p. 155-162Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Claesson, Ingvar
    et al.
    Blekinge Institute of Technology, Department of Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, Department of Signal Processing.
    Lagö, Thomas L
    Robust Control of Machine-Tool Vibration in a Lathe1999Conference paper (Refereed)
    Abstract [en]

    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. 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 substantially by active control of the machine-tool vibration. Adaptive feedback control based on the filtered-x LMS-algorithm, enables a reduction of the vibration by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz. The active control performeds a broadband attenuation of the sound pressure level by up to 35 dB. However, the process of machining a workpiece usually involves a variety of cutting data which in turn are likely to cause substantial variations in the spectral properties of the tool vibrations. Hence, variations in the spectral properties originates from changes in the excitation of the tool holder and changes in the structural response of the tool holder. To handle the potential large variations in the spectral properties of tool vibration in the turning operation the robustness of the control system has to be improved. By applying the leaky version of the filtered-x LMS algorithm in the active control of machine tool vibration it was found that the robustness of the adaptive control system was improved substantially to large variations in the spectral properties of tool vibration.

  • 12.
    Claesson, Lena
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Displacement measurements versus time using a remote inclined plane laboratory2016In: Proceedings of 2016 13th International Conference on Remote Engineering and Virtual Instrumentation, REV 2016, IEEE Press, 2016, p. 355-356Conference paper (Refereed)
    Abstract [en]

    This paper describes a remote implementation of Galileos inclined plane experiment, focused on secondary school students. A remotely controlled inclined plane has been designed and implemented in the VISIR lab at Blekinge Institute of Technology (BTH), Sweden. In this demo session, it will be demonstrated how to perform measurements remotely in the remotely controlled Inclined Plane Laboratory. A web camera is used to show the experiment. Data concerning the distance a cube has slided down the inclined plane are collected. These data are stored in a file and can subsequently be analyzed by the students. The friction acting on the cube sliding down the inclined plane and its acceleration may for instance be investigated.

  • 13.
    Claesson, Lena
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Using an online remote laboratory for electrical experiments in uppersecondary education2011Conference paper (Refereed)
  • 14.
    Claesson, Lena
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Using an Online Remote Laboratory for Electrical Experiments inUpper Secondary Education2012In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 8, no S2, p. 24-30Article in journal (Refereed)
    Abstract [en]

    The use of remote laboratories in courses at university level has been reported in literature numerous times since the mid 90?s. In this article focus is on activities carried out by teachers and students, at the Upper Secondary School Level, using the remote laboratory VISIR (Virtual Instrument Systems in Reality). The Upper Secondary School, Katedralskolan in Lund, Sweden, cooperate with Blekinge Institute of Technology, Sweden, in a project that concerns the introduction of remote laboratory environment suitable for Upper Secondary School science courses. A remote laboratory in electronics has been introduced and is used as a complement to the traditional workbench in the hands-on laboratory. Significant results from the project are; 1) the great interest shown by the students for the remote experiments, 2) the students appreciation for the fact that it was not simulations but actual real experiments, 3) the remote laboratory is easy to implement for use by both teachers and students and 4) it can be used simultaneously by many students.

  • 15.
    Elisabeth, Källström
    et al.
    Volvo, SWE.
    John, Lindström
    Luleå tekniska Universitet, SWE.
    Lars, Håkansson
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Magnus, Karlberg
    Luleå tekniska Universitet, SWE.
    Renderstedt, Reza
    Volvo, SWE.
    Larsson, Jonas
    Volvo, SWE.
    Identification of vibration properties of heavy duty machine driveline parts as a base for adequate condition monitoring: Axle2016In: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics / [ed] Vogiatzis, K; Kouroussis, G; Crocker, M; Pawelczyk, M, INT INST ACOUSTICS & VIBRATION , 2016Conference paper (Refereed)
    Abstract [en]

    With increasing complexity in the heavy duty construction equipment, early fault detection of certain components in the machine becomes more and more challenging due to too many fault codes generated when a failure occurs. The axle is one such component. The axle transfers driving torque from the transmission to the wheels and axle failure may result in costly downtime of construction equipment. To reduce service cost and to improve uptime, adequate condition monitoring based on sensor data from the axle is considered by for instance measuring vibrations on the axle. Further, the analysis of the data collected has been has been carried out using adequate signal processing methods. The results indicate that the vibration properties of the axle are relevant for early fault detection of the axle. Thus, the health of the axle may be continuously monitored on-board using the vibration information and if the axle health starts to degrade a service and/or repair may be scheduled well in advance of a potential axle failure and in that way the downtime of a machine may be reduced and costly replacements and repairs avoided.

  • 16.
    Gertsovich, Irina
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Bartuněk, Josef Ström
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Nilsson, Mikael
    A novel methodology for the interoperability evaluation of an iris segmentation algorithm2013Conference paper (Refereed)
    Abstract [en]

    The performance of an iris recognition system depends greatly on how well the iris segmentation part of the system performs its task. The performance of an iris segmentation algorithm can be evaluated using different criteria and methods. Some of the methods evaluate the performance of the segmentation algorithm based on the performance of the whole iris recognition system. Other methods evaluate the performance of an iris segmentation subsystem independent of the performance of the system's other subsystems. To our knowledge there do not exist a generally accepted method or criteria for the evaluation of the standalone iris segmentation subsystem. This paper proposes a novel methodology to compare the performance of different iris segmentation algorithms, applied to different image datasets in a consistent way. The methodology employs the F1 score and an empirical cumulative distribution function. The implementation of the F1 score estimation, adapted to the iris segmentation task is described. Finally the application of the proposed methodology is demonstrated and discussed.

  • 17.
    Gothberg, Mattias
    et al.
    Atlas Copco, SWE.
    Enblom, Samuel
    Atlas Copco, SWE.
    Rantakokko, Renny
    Atlas Copco, SWE.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering. Blekinge Institute of Technology, Department of Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Signal Processing. Blekinge Inst Technol, Dept Appl Signal Proc, Karlskrona, Sweden..
    EFFICIENT MULTI CHANNEL VIBRATION MEASUREMENT-SYSTEMATIC APPROACH2016In: PROCEEDINGS OF THE 23RD INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: FROM ANCIENT TO MODERN ACOUSTICS / [ed] Vogiatzis, K Kouroussis, G Crocker, M Pawelczyk, M, INT INST ACOUSTICS & VIBRATION , 2016Conference paper (Refereed)
    Abstract [en]

    In Atlas Copco a wide range of machines is produced from surface drill rigs, exploration drill rigs, underground drill rigs both for mining and construction to underground loader and haulers for mines. Recently new rock excavation methods have developed in cooperation with large mining companies. The machines are produced in low volume and often customized although having a modular approach. Time for validation is limited due to machines available for test are planned for customer delivery. It is on regular basis needed to validate and investigate vibrational behavior of installations as power packs and drivelines to get loads for simulation, identify resonances, operational deflection shapes, and vibration and stress levels for life length estimations under operational conditions. The time for a 40-180 Channel measurement is now down the range of 13 days. To reduce the time it takes to perform measurement a systematic approach has been taken that includes mainly three areas. First the Bookkeeping of all information and data needed for the analysis and reporting is input before or during the measurement. Systematic Approach of how to setup sensors, handle cable and equipment, planning and measurement. This includes practical examples of how to. Finally it is very important to take steps to assure Quality early in the measurement and also avoiding disturbances in the sensor path. There will be practical examples of important disturbances to look out for and quality check to perform. It should also be noted that the measurements is regular measured in mines or start up halls under rpm sweeps or/and operating conditions of the machines.

  • 18. Gustavsson, Ingvar
    et al.
    Claesson, Lena
    Nilsson, Kristian
    Zackrisson, Johan
    Zubia, Javier Garcia
    Jayo, Unai Hernandez
    Håkansson, Lars
    Bartunek, Josef Ström
    Lagö, Thomas L
    Claesson, Ingvar
    The VISIR Open Lab Platform2011In: Internet Accessible Remote Laboratories: Scalable E-Learning Tools for Engineering and Science Disciplines / [ed] Azad, Abul K.M.; Auer, Michael E.; Harward, V. Judson, IGI Global , 2011, p. 294-317Chapter in book (Refereed)
    Abstract [en]

    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.

  • 19.
    Gustavsson, Ingvar
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Garcia-Zubia, J.
    Hernandez-Jayo, U.
    Nedic, Z
    Göl, Ö.
    MacHotka, J.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Pettersson, Mats
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    On objectives of instructional laboratories, individual assessment, and use of collaborative remote laboratories2009In: IEEE Transactions on Learning Technologies, ISSN 1939-1382, E-ISSN 1939-1382, Vol. 2, no 4, p. 263-274Article in journal (Refereed)
    Abstract [en]

    Three key issues should be addressed to enable universities to deliver engineers who have a solid documented laboratory experience enabling them to design goods and services complying with the requirements of a sustainable society. First, introduce learning objectives of engineering instructional laboratories in courses including laboratory components. Second, implement individual student assessment. Third, introduce free access to online experimental resources as a supplement to the equipment in traditional laboratories. Blekinge Institute of Technology (BTH) in Sweden and the University of South Australia (UniSA) have created online laboratory workbenches for electrical experiments that mimic traditional ones by combining virtual and physical reality. Online workbenches not only supplement traditional ones, but they can also be used for low-cost individual assessment. BTH has started a project disseminating the BTH workbench concept, The Virtual Instrument Systems in Reality (VISIR) Open Laboratory Platform, and invites other universities to set up replicas and participate in further development and standardization. Further, online workbenches offer additional learning possibilities. UniSA has started a project where students located in different countries can perform experiments together as a way to enhance the participants' intercultural competence. This paper discusses online laboratory workbenches and their role in an engineering education appropriate for a sustainable society.

  • 20. Gustavsson, Ingvar
    et al.
    Olsson, Thomas
    Åkesson, Henrik
    Håkansson, Lars
    A Remote Electronics Laboratory for Physical Experiments using Virtual Breadboards2005Conference paper (Refereed)
    Abstract [en]

    In traditional university laboratories students conduct experiments under the supervision of an instructor. A remotely-operated laboratory for undergraduate education in electrical engineering which emulates a traditional laboratory has been set up by Blekinge Institute of Technology (hereafter referred to as BTH), Ronneby, Sweden. The laboratory is a client/server application and the Internet is used as the communication infrastructure. Most remote laboratories elsewhere are used for fixed experiments but in the BTH laboratory students around the world can assemble circuits simultaneously from electronic components in much the same way as they do in a traditional laboratory. The teacher or a member of the laboratory staff mounts the components to be used in the lab sessions in a circuit assembly robot in the experiment server in Ronneby. Students use the mouse to connect some of the corresponding virtual components on a virtual breadboard displayed on the client PC. Students thus control the robot by means of the wiring on the virtual breadboard. Virtual instrument front panels are used to control and read the instruments by means of remote control. To avoid potentially serious student mistakes e.g. overloading a component the teacher can preset limits to the source voltages which are accessible to students. The teacher can also restrict student circuits by, for example, dictating minimum impedance in loops created with aid of the components provided. The number of nodes provided on the virtual breadboard is adequate for experiments in undergraduate education. The laboratory is always open and can be used by registered students and guest users alike. The time-sharing scheme used allows simultaneous access for up to 8 client PCs. A 56 kbit/s modem and MS Internet Explorer are all that are required. The client software can be downloaded from the laboratory web site at http://distanslabserver.its.bth.se/. This paper discusses the remotely operated laboratory at BTH; it focuses on the virtual breadboard.

  • 21. Gustavsson, Ingvar
    et al.
    Pettersson, Mats
    Håkansson, Lars
    Lagö, Thomas L
    Claesson, Ingvar
    Gör ingenjörsutbildningen attraktiv genom att öka det experimentella inslaget2008Conference paper (Other academic)
    Abstract [sv]

    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.

  • 22. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Bartunek, Josef Ström
    Nilsson, Kristian
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Telemanipulator for Remote Wiring of Electrical Circuits2008Conference paper (Refereed)
    Abstract [en]

    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.

  • 23. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Bartunek, Josef Ström
    Åkesson, Henrik
    Håkansson, Lars
    Lagö, Thomas L
    An Instructional Electronics Laboratory Opened for Remote Operation and Control2006Conference paper (Refereed)
    Abstract [en]

    Blekinge Institute of Technology in Sweden has opened a local instructional laboratory for undergraduate education in electrical and electronic engineering for remote operation and control 24/7 as a complement and a supplement to traditional laboratories. It is equipped with a unique virtual interface enabling students to recognize on their own computer screen the desktop instruments and the breadboard most of them have already used in the local laboratory. The open laboratory is used in regular courses in circuit analysis for distant learning students dispersed all over Sweden and for campus students as well. The research is focused on what is perceived to be the greatest challenge, to give students laboratory experience that is as genuine as possible despite the lack of direct contact with the actual lab hardware. The goal is to produce an open international standard in cooperation with universities and other organizations around the world.

  • 24. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Håkansson, Lars
    Distributed Laboratories Based on Open Source Technologies2007In: 2007-07-23 / [ed] Garcia-Zubia, L. Gomes and J., Bilbao: University of Deusto , 2007, p. 247-267Chapter in book (Refereed)
    Abstract [en]

    This chapter discusses the general principles of remote laboratories. It focuses on the experimental and hardware aspects of the innovation. Access methods, protocols, and new web technologies such as Web 2.0 have been covered elsewhere. A remote laboratory project was started in 1999 at Blekinge Institute of Technology (hereafter referred to as BTH) in Sweden to ascertain if it is feasible to design a remote electronics laboratory which could function as a supplement to local instructional laboratories and provide students with free access to experimental equipment. Today, there are two laboratories online, one for electronics and one for signal processing. These are used as examples in the ensuing discussion. The BTH Open Laboratory concept evolved over a number of years. Its object is to add a remote operation option to traditional instructional laboratories thereby making the latter more accessible. This option is equipped with a unique interface enabling students to recognize on their own computer screen the instruments and other equipment which most of them have used in the local laboratory. The research is focused on what is considered to be the greatest challenge in engineering education today, i.e. to give students a laboratory experience that is as genuine as possible without direct contact with the actual lab hardware while at the same time allowing teachers to use standard equipment and readily available learning material. The winners are not only students and teachers, but also universities, which will be able to share distributed laboratories. Finally, the chapter presents some ideas about standards for primarily distributed electronics laboratories based on IVI (Interchangeable Virtual Instruments).

  • 25. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    The VISIR project – an Open Source Software Initiative for Distributed Online Laboratories2007Conference paper (Refereed)
    Abstract [en]

    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).

  • 26. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Nilsson, Kristian
    Garcia-Zubia, Javier
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid2008Conference paper (Refereed)
    Abstract [en]

    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.

  • 27. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Nilsson, Kristian
    Garcia-Zubia, Javier
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid2008In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 4, no 2, p. 12-16Article in journal (Refereed)
    Abstract [en]

    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.

  • 28. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    A Flexible Remote Electronics Laboratory2005Conference paper (Refereed)
    Abstract [en]

    The Internet provides new possibilities for universities and other teaching organizations to share laboratories equipped with expensive instruments. A remotely operated electronics laboratory has been set up by Blekinge Institute of Technology in Sweden. The laboratory is a client/server application and the Internet is used as the communication infrastructure. In the new version presented in this paper security problems are solved and an authentic appearance of instruments and components are provided. Most remote electronics laboratories elsewhere offer fixed experiments but in this one, students can simultaneously assemble circuits and conduct experiments much like they do in a traditional university laboratory. The laboratory is always open and can be used by registered students and guest users around the world.

  • 29. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    Experimentera hemma med utrustningen i universitetens övningslaboratorier2006Conference paper (Other academic)
    Abstract [sv]

    Blekinge Tekniska Högskola, BTH, har öppnat ett övningslaboratorium för ellära och elektronik för fjärrstyrning och håller på att öppna ett fjärrstyrbart signalbehandlingslaboratorium för vibrationsanalys. Ett unikt användargränssnitt gör det möjligt att från valfri plats styra och manövrera experimentutrustningen på samma sätt som i laboratorielokalerna. Allt som behövs är Internetansluten PC med standardprogramvara. Denna forskning är inriktad mot vad som upplevs som den största utmaningen dvs. att ge studenterna en så genuin upplevelse som möjligt oaktat bristen på direkt kontakt med den fysikiska experimentutrustningen. BTH bjuder in andra lärosäten både nationellt och internationellt att delta i pedagogisk utvärdering av detta komplement till att experimentera i laboratoriesal och att delta i vidareutvecklingen mot en internationell standard.

  • 30. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Remote Operation and Control of Traditional Laboratory Equipment2006In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 2, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    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.

  • 31.
    Göthberg, Mattias
    et al.
    Atlas Copco, SWE.
    Enblom, Samuel
    Atlas Copco, SWE.
    Rantakokko, Renny
    Atlas Copco, SWE.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Efficient multi channel vibration measuremen: systematic approach2016In: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics, 2016Conference paper (Refereed)
    Abstract [en]

    In Atlas Copco a wide range of machines is produced from surface drill rigs, exploration drill rigs, underground drill rigs both for mining and construction to underground loader and haulers for mines. Recently new rock excavation methods have developed in cooperation with large mining companies. The machines are produced in low volume and often customized although having a modular approach. Time for validation is limited due to machines available for test are planned for customer delivery. It is on regular basis needed to validate and investigate vibrational behavior of installations as power packs and drivelines to get loads for simulation, identify resonances, operational deflection shapes, and vibration and stress levels for life length estimations under operational conditions. The time for a 40-180 Channel measurement is now down the range of 1-3 days. To reduce the time it takes to perform measurement a systematic approach has been taken that includes mainly three areas. First the Bookkeeping of all information and data needed for the analysis and reporting is input before or during the measurement. Systematic Approach of how to setup sensors, handle cable and equipment, planning and measurement. This includes practical examples of how to. Finally it is very important to take steps to assure Quality early in the measurement and also avoiding disturbances in the sensor path. There will be practical examples of important disturbances to look out for and quality check to perform. It should also be noted that the measurements is regular measured in mines or start up halls under rpm sweeps or/and operating conditions of the machines.

  • 32.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    The Fourier Transform in Sound and Vibration2015In: International Journal of Acoustics and Vibration, ISSN 1027-5851, ISSN 1027-5851, Vol. 20, no 4, p. 190-190Article in journal (Refereed)
  • 33. Håkansson, Lars
    et al.
    Brandt, Anders
    Lagö, Thomas L
    Claesson, Ingvar
    Modal Analysis and Operating Deflection Shapes of a Boring Bar2003Conference paper (Refereed)
    Abstract [en]

    In the manufacturing industry, the internal turning or boring operation is a common metal working process that is usually associated with vibration problems. Vibration in boring operations is usually inevitable. This necessitates extra care being taken in production planning and preparation. Thus, the vibration problems in internal turning considerably influence important factors such as productivity, production costs, etc. In order to gain further understanding of the dynamic behaviour of clamped boring bars in the metalcutting process experimental methods may be utilized. Two experimental methods have been used in order to investigate dynamic properties of a clamped boring bar: 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 two 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 two 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.

  • 34. Håkansson, Lars
    et al.
    Claesson, Ingvar
    A Solution to Control Path Differences in The Feedback Filtered-x LMS Control of Boring Bar Vibration2004Conference paper (Refereed)
    Abstract [en]

    The internal turning operation is a common metal working operation that is usually associated with vibration problems. Boring bar vibration affect the result of the machining, in particular the surface finish. Furthermore, the tool life is correlated with the amount of vibration and the acoustic noise introduced. The noise level is sometimes almost unbearable. Generally, the motion of a boring bar is greatest in the cutting speed direction, and related to one of the bars two fundamental bending modes. A self tuning solution that has a high potential to further reduce the vibration problems in internal turning is the adaptive active control of boring bar vibration based on the feedback filtered-x LMS algorithm and boring bars with embedded actuators. The filtered-x LMS requires an estimate of the control path. To obtain a practical estimation of the control path, to avoid internal turning with severe vibration levels, usually requires that the control path is estimated off-line, i.e. the boring bar is not in contact with the workpiece. However, the control path usually differs between continuous cutting operations and when the boring bar is not in contact with the workpiece, and a phase difference of approximately 90 degrees generally occurs at the resonance frequency to be controlled. This phase difference constitutes a severe problem concerning the feedback filtered-x LMS control. By using a short FIR-filter control path estimate sufficient phase accuracy is obtained to enable robust adaptive control of bar vibration, which attenuates the vibration level with up to approximately 40 dB.

  • 35. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Lagö, Thomas L
    Active Control of Machine Tool Chatter1999Conference paper (Refereed)
    Abstract [en]

    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. 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 by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz. The active control performed a broadband attenuation of the sound pressure level by up to 35 dB. A significant improvement of the workpiece surface was also observed.

  • 36. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Pettersson, Linus
    Embedded piezoceramic actuators in a tool holder shank for the active control of machine-tool vibration1999Conference paper (Refereed)
    Abstract [en]

    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 based on high magnetostrictive actuators. However, both the physical features and properties of a active tool holder construction based on high magnetostrictive actuators and the fact that this type of actuators generally have a non-linear behaviour highly reduce its applicability to the general lathe and turning operation. Therefor, a new generation embedded active tool holder shanks based on piezo ceramic actuators have 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. It is also obvious that physical features and properties of new generation embedded active tool holder shanks based on piezo ceramic actuators fits the general lathe application.

  • 37. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Pettersson, Linus
    Lagö, Thomas L
    Active Control Machine Tool Chatter Embedded Piezo Ceramic Actuators in Tool Holder Shank1999Conference paper (Refereed)
    Abstract [en]

    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. Adaptive feedback control based on the filtered-x LMS-algorithm, enables a reduction of the vibration by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz. The active control performed a broadband attenuation of the sound pressure level by up to 35 dB . A significant improvement of the workpiece surface was also observed. In the active control of tool vibration a tool holder construction based on integrated high magnetostrictive actuators was used. However, both the physical features and properties of an active tool holder construction based on high magnetostrictive actuators and the fact that this type of actuators generally have a non-linear behaviour highly reduce its applicability to the general lathe and turning operation. Therefor, a new generation embedded active tool holder shanks based on piezo ceramic actuators have 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. It is also obvious that physical features and properties of new generation embedded active tool holder shanks based on piezo ceramic actuators fits the general lathe application.

  • 38. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Pettersson, Linus
    Lagö, Thomas L
    Embedded Piezoceramic Actutaors in a Tool Holder Shank for the Active Control of Machine-tool Vibration1999Conference paper (Refereed)
    Abstract [en]

    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 based on high magnetostrictive actuators. However, both the physical features and properties of a active tool holder construction based on high magnetostrictive actuators and the fact that this type of actuators generally have a non-linear behaviour highly reduce its applicability to the general lathe and turning operation. Therefor, a new generation embedded active tool holder shanks based on piezo ceramic actuators have 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. It is also obvious that physical features and properties of new generation embedded active tool holder shanks based on piezo ceramic actuators fits the general lathe application.

  • 39. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Sturesson, Per-Olof
    Adaptive Feedback Control of Machine-Tool Vibration based on The Filtered-x LMS Algorithm1998In: Journal of Low Frequency Noise Vibration and Active Control, ISSN 0263-0923, Vol. 17, no 4, p. 199-213Article in journal (Refereed)
    Abstract [en]

    Adaptive feedback control of tool vibrations during metal cutting in a lathe has been investigated. The vibrations were controlled in the primary cutting direction and the control is based on the filtered-x LMS-algorithm. It was found that the adaptive feedback control can achieve a reduction of the tool vibrations with up to 35 dB at 1.7 kHz and simultaneously with approximately 30 dB at 3.1 kHz. A significant improvement of the workpiece surface was experienced together with a substantial reduction of the acoustic noise level with adaptive feedback control. Tool life is also expected to be extended and the material removal rate can probably be increased.

  • 40. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Sturesson, Per-Olof
    Lagö, Thomas L
    Active Control of Chatter in Turning: The Origine of Chatter1999Conference paper (Refereed)
    Abstract [en]

    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. 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. To achieve a further reduction of the dynamic motion between cutting tool and workpiece one solution is the active control of machine-tool vibration. However, to successfully apply active control of tool vibration in the external turning operation the response of the tool holder shank has to be investigated in order to enable the proper introduction of secondary vibration in the tool holder shank and to select a suitable controller. The investigation of the dynamic response of the tool holder shank relies on a stochastic approach while the structural dynamic properties have been evaluated by a normal mode analysis. This resulted in active control of tool vibration in a lathe that enables a reduction of the vibration by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz.

  • 41. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Ståhl, Jan-Eric
    Fix-Number Realization of Adaptive Control of Machine-Tool Vibration1998Conference paper (Refereed)
    Abstract [en]

    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. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. Dynamic motion between cutting tool and workpiece can be reduced substantially by active control of the machine-tool vibration based on the filtered-x LMS-algorithm. However, in the digital implementation of the filtered-x LMS-algorithm both the inputs and the internal algorithmic quantities are limited to a certain precision. The process of machining a workpiece is also likely to introduce large variations in the level of both input and output signals of the digital controller. The tool shank vibrations can generally be described as a superposition of narrow-band random processes at each modal frequency. Both the variation in signal level and the narrow-band character of the vibration are likely to be unfavorable a fix number realization of the filtered-x LMS-algorithm. The potential large dynamic range in the input signal may introduce coefficient bias and stalling of the convergence of the adaptive FIR filter. Furthermore, both the narrow-band character of the vibration and a large dynamic range in the input signal may result in overflow and thereby seriously degrade the performance of the control system. However, by the use of the leaky filtered-x LMS algorithm problems due to the limited numerical precision such as overflow will be reduced to a large extent.

  • 42. Håkansson, Lars
    et al.
    Claesson, Ingvar
    Ståhl, Jan-Eric
    Andersson, Mats
    Adaptiv reglering av verktygsvibrationer i svarvoperationen1998Conference paper (Refereed)
    Abstract [sv]

    I svarvoperationen är relativ dynamisk rörelse mellan verktyg och arbetsstycke ett vanligt förekommande problem. Rörelsen påverkar bearbetningsresultatet, speciellt arbetsstyckets yta, men även verktygets livslängd påverkas. Arbetsmiljöproblem som buller förekommer också på grund av vibrationer i svarvoperationen. Problemet kan delvis lösas med lämplig konstruktion som ökar styvheten i maskinstrukturen, vilken dock begränsas av den dynamiska styvheten i strukturen hos verktygshållare samt arbetsstycke. Med aktiv reglering av verktygshållarens respons, dvs. aktiv reglering av verktygsvibrationer, kan en ytterligare ökning av den dynamiska styvheten i det skärtekniska systemet erhållas. Regleringen av verktygsvibrationer har utförts med en återkopplad regulator som är baserad på den så kallade "filtered-x LMS"-algoritmen samt aktuatorer baserade på magnetostriktiv teknik. Verktygshållarens respons, verktygsvibrationerna, detekteras med en givare (accelerometer) som är monterad på verktygshållaren. Genom att introducera motvibrationer i verktygshållaren med en sekundär vibrationskälla, aktuator, via regulatorn som matas med de uppmätta vibrationerna, modifieras verktygshållarens respons. Med aktiv reglering av verktygsvibrationer uppmättes en reduktion av vibrationerna med ca 30 dB vid 1.7 kHz. Vidare erhölls en signifikant förbättring av arbetsstyckets yta och en avsevärd reducering av bullernivån erhölls.

  • 43. Håkansson, Lars
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Chapter 78 Machine Tool Noise, Vibration and Chatter Prediction and Control2005In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: To be published by by John Wiley & Sons , 2005Chapter in book (Other academic)
    Abstract [en]

    A frequent problem in the manufacturing industry today is the vibrations or chatter induced by metal cutting, e.g. turning, milling and boring operations. Vibrations in boring operations or internal turning operations, for example,are inevitable and constitute a major problem for the manufacturing industry. Tool vibrations in metal cutting affect the result of machining, particularly the surface finish. Furthermore, tool life is correlated with the degree of vibration and acoustic noise introduced. Generally, tool vibrations are related to a low-order bending mode of, for example, the tool holder shank in external turning, the boring bar in internal turning, spindle-cutter assembly in milling, etc. Tool chatter or vibration problems in internal turning or milling may be reduced, for example, by using boring bars and milling adapters with passive tuned dampers. These are usually manually tuned to increase the dynamic stiffness of the boring bar or milling adapter at one of the eigenfrequencies of its low-order bending modes. Active control approaches for the attenuation of the bending motion of boring bars, tool holder shanks and spindle-cutter assembly in milling have been developed; such approaches involve both adaptive and time-invariant feedback control. In addition, prediction and control methods for controlling cutting data to maintain stable cutting, i.e. to avoid cutting data resulting in chatter, have been developed.

  • 44. Håkansson, Lars
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Machine Tool Noise, Vibration and Chatter Prediction and Control2007In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: John Wiley & Sons , 2007Chapter in book (Other academic)
  • 45. Håkansson, Lars
    et al.
    Johansson, Sven
    Dahl, Mattias
    Sjösten, Per
    Claesson, Ingvar
    NOISE CANCELLING HEADSETS FOR SPEECH COMMUNICATION2002In: Noise Reduction in Speech Applications / [ed] Davis, Gillian M., Boca Raton, Florida: CRC Press , 2002, p. 305-327Chapter in book (Other academic)
    Abstract [en]

    Headsets for speech communication are used in a wide range of applications. The basic idea is to allow hands-free speech communication, leaving both hands available for other tasks. One typical headset application is aircraft pilot communication. The pilot must be able to communicate with personnel on the ground and at the same time use both hands to control the aircraft. Communication headsets usually consist of a pair of headphones and a microphone attached with an adjustable boom. Headphone design varies widely between different manufacturers and models. In its simplest form, the headphone has an open construction providing little or no attenuation of the environmental noise. In headsets designed for noisy environments, the headphones are mounted in ear cups with cushions that provide some attenuation. The microphone is primarily designed to pick up the speech signal, but if the headset is used in a noisy environment, the background noise will also be picked up and transmitted together with the speech. As a consequence, speech intelligibility at the receive end will be reduced, possibly to zero. To increase the speech-to-noise ratio, it is common to use a directional microphone that has a lower sensitivity to sound incident from other directions than the frontal direction. In addition to this, the microphone electronics are usually equipped with a gate function that completely shuts off the microphone signal if its level drops below a threshold value. The purpose of the gate is to open the channel for transmission only when a speech signal is present. Headsets are frequently used in noisy environments where they suffer from problems of speech intelligibility. Even if an ear-cup type headset is used, the attenuation is relatively poor for low frequencies. Low frequency noise has a masking effect on speech, which significantly reduces the speech intelligibility. Several cases have been reported in which the sound level of the communication signal was increased to hazardous levels by the user to overcome this low frequency masking effect [1,2]. Ear exposure to the communication system resulted in hearing damage, such as hearing loss, tinnitus and hyperacusis.

  • 46. Håkansson, Lars
    et al.
    Sturesson, Per-Olof
    Claesson, Ingvar
    Active Control of Machine-Tool Vibration1995Conference paper (Refereed)
    Abstract [en]

    A new adaptive technique is presented for the increase of the dynamic stiffness of the cutting tool in a lathe by active control of the tool vibration in the cutting speed direction. Due to the statistic properties of tool vibration that are induced by the stochastic behavior of chip formation process, the controller is based on the filtered-x LMS algorithm which controls an adaptive filter that is based on Wiener filter theory. Hence, the adaptation of the filtered-x LMS algorithm is gradient-based and it is based on a classical optimization technique, the method of steepest descent. In the cutting experiments a tool holder construction with integrated actuators, i.e. secondary sources was used. The cutting experiments shows that the adaptive technique presented in this paper enables an increase in the dynamic stiffness of the cutting tool, i.e. tool vibrations are suppressed.

  • 47. Johansson, Sven
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Aircraft Cabin Noise and Vibration Prediction and Active Control2007In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: John Wiley & Sons , 2007Chapter in book (Other academic)
  • 48. Johansson, Sven
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    AIRCRAFT CABIN NOISE AND VIBRATION PREDICTION AND ACTIVE CONTROL2005In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: To be published by John Wiley & Sons , 2005Chapter in book (Other academic)
    Abstract [en]

    The active control of noise and vibration in passenger aircraft cabins generally rely on adaptive multi channel feedforward control of disturbing acoustic cabin modes based on a set of control sources and error sensors with optimized locations, or on feedback control in active headsets or in quiet seats. The structural aircraft fuselage vibrations produced by the propulsion system and turbulence pressure fluctuations acting on the external fuselage generally excite the interior cabin sound field. Cabin noise in turboprop aircraft and jet aircraft with tail-mounted engines are usually dominated by tonal noise related to the fundamental blade passage frequency and the jet engine spool imbalance frequencies respectively. The jet noise -engine exhaust noise- and turbulent boundary layer noise, on the other hand, have broadband characteristics. The active control of tonal noise in aircraft is of global character and involves multi channel active noise control or multi channel active structural acoustic control. The locations of the secondary sources and error sensors are optimized for the acoustic noise attenuation over a range of flight conditions and are selected from a set of potential configurations. Generally, the active control systems for reducing the tonal cabin noise are based on variants of the multi channel Filtered-X LMS algorithm, and both time domain and frequency domain algorithms are used. Feedback control in active headsets or in silent seats addresses the broadband cabin noise.

  • 49. Johansson, Sven
    et al.
    Håkansson, Lars
    Persson, Per
    Claesson, Ingvar
    Active Control Methods for Reducing Lateral Vibrations in High-Speed Trains2002Conference paper (Refereed)
    Abstract [en]

    The problem of low-frequency lateral train-car vibration is an important issue surrounding the design of high-speed trains. Passive vibration control solutions such as stiffening the car chassis are impractical because of the weight increase, and modifying the structural dynamics of the carboy through nonrigid coupling of heavy underfloor equipment does not come with a weight penalty, but do not sufficiently reduce the vibrations. This paper addresses two simple active vibration control systems for reducing lateral vibrations: one feedforward system and one feedback. Computer simulations based on signals derived from a dynamic computer model of a train car indicates that the incorporation of an active control system, in addition to the passive approach, is likely to introduce an improved attenuation of the low-frequency lateral vibrations. Active control results illustrate an attenuation of the lateral train-car vibration by up to 14 dB.

  • 50. Johansson, Sven
    et al.
    Håkansson, Lars
    Persson, Per
    Claesson, Ingvar
    Active Control of Lateral Vibrations in a Railway Carriage2002In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 7, no 4, p. 195-210Article in journal (Refereed)
    Abstract [en]

    As trains are continually designed for higher and higher speeds the problems of railway carriage vibration are on the increase. Lateral vibrations in a railway carriage are noticeable to passengers if the vibration frequencies are lower than approximately 20 Hz. Below this frequency discomfort is a common problem for the passengers and below approximately 1 Hz motion sickness is a problem. The passive solution of stiffening the carriage chassis to shift the vibrational frequencies higher up results in inflated manufacturing and running costs, and opposes higher travel speeds due to increased weight. Semi-passive solutions such as modifying the structural dynamics of the carriage body by decoupling heavy underfloor equipment do not reduce the vibrations sufficiently. However, by appending a multi-reference feedforward active vibration control system, one way expect a substantial reduction in the lateral vibration level. Using a dynamic computer model of a railway carriage simulating the lateral vibration, and using as input bogie acceleration data measured on a running train, multiple-input/single-output coherence spectra were shown to constitute a suitable set of reference signals for an active control system. Control simulations based on the Feedforward Multiple-Input/Single-Output Filtered-x LMS Algorithm are carried out using different reference signal combinations. The control results indicate lateral vibration attenuation on the order of 15dB at the objective frequency of 10Hz.

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