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The key driving factors in using humans and robots in collaborative applications for assembly processes are to reduce assembly time, cost and to improve the human working environment from an ergonomic viewpoint. Currently, there are limited automated procedures in assembly operations in house construction because the traditional type of assembly process depends entirely on manpower. This is common in the assembly process in different industries since assembly is one of the most demanding and intense manufacturing processes, and it is difficult to automate. This paper presents a case study on the implementation of human-robot collaboration for window assembly by way of an offline robot programming simulation. A self-adaptive software architecture that runs on a real-time target machine is also proposed for robotic window assembly. The window assembly method that will be used in this study is called “Click-In” and is manufactured by Fixture System Sweden AB. Apart from robot simulations, detailed suggestions are given for building a pilot cell for robot window assembly. The case study presented in this paper has both economical and ergonomic goals. The economic goal is to reduce the assembly time which will lead to an increase in window production. By introducing human-robot collaboration, operators do not need to perform uncomfortable assembly operations—rather the robot will perform these un-ergonomic operations. The feasibility of both goals is verified with offline robot programming simulation.

Automation of the drilling process is a widely spread goal in the rock excavator industry. An intermediate step can be to assist a manual drilling process by informing the operator of the quality of the drilling. To reach the goals, it is thus imperative to have a high performance monitoring system based on physics involved in the drilling process. A necessity to develop such an information system, is insight into the physics involved in the drilling process. This can be gained by using combinations of simulations, lab tests and in-situ tests. Here, a 1D model representing Down The Hole (DTH) drilling is used. Such a model can be further developed to simulate good and bad performance of drilling. The resulting vibration responses, hydraulic pressure responses, etc. of the system can be analyzed with the purpose to identify possible sources of informative data which can be measured and recorded during a real world rock drilling operation. Here, a simplified 3D model of the DTH drilling system involving the bit, hammer and the drill string is also made and used together with boundary conditions constituting a simplified model of the rock. The aim here is to find a computationally efficient 3D modeling methodology to simulate the drilling for various conditions, due to various drilling parameter settings. The aim is to develop a 3D model that can be refined further and can be used extensively to understand the DTH drilling process in order to facilitate performance monitoring and in the end automized DTH drilling.

Optimizing the performance for down the hole (DTH) drills is becoming increasingly important. This is due to that the industry is becoming highly competitive and therefore there is an ever-increasing demand for improving the efficiency of the drilling process. To do this, it is important to have a robust monitoring system in place that should be based on in-depth knowledge of the underlying physics of the drilling system and process. Such a system will assist drillers in improving the perfor-mance e.g. by providing recommendations concerning the settings of the drilling. To understand the performance of the system, it is very important to understand the information that can be extracted from different drilling related quantities. In this work, information obtained from the pressure signals from the feed/holdback line, impact pressure line and rotation line together with vibration signals measured with the aid of accelerometers mounted at specific locations on the drill rig are discussed. For instance, spectral properties of these quantities for good and bad drilling cases are investigated. The results indicate correlations, to some extent, between the spectral properties and the quality of the drilling.

In order to reduce costly downtime, adequate condition monitoring of the automatic transmission components in heavy duty construction equipment is necessary. The transmission in such equipment enables to change the gear ratio automatically. Further, the bearings in an automatic transmission provide low friction support to its rotating parts and act as an interface separating stationary from rotating components. Wear or other bearing faults may lead to an increase in energy consumption as well as failure of other related components in the automatic transmission, and thus costly downtime. In this study, different sensor data (particularly vibration) was collected on the automatic transmission during controlled test cycles in an automatic transmission test rig to enable adequate condition monitoring. An analysis of the measured vibration data was carried out using signal processing methods. The results indicate that predictive maintenance information related to the automatic transmission bearings may be extracted from vibrations measured on an automatic transmission. This information may be used for early fault detection, thus improving uptime and availability of heavy duty construction equipment.

Improving uptime is paramount in the heavy duty construction equipment business. Failure ofcritical components in the heavy duty machine may lead to unnecessary stops and expensive downtime. The torque converter, a complex omponent of the driveline, transmits and multiplies torque from the engine to the gearbox, and its failure may not only lead to the machine standing still but may also lead to damage of other parts of the automatic transmission. For adequate condition monitoring of the torque converter, different sensor data are measured on a construction equipment machine during controlled driving sessions. Vibration has been measured on the torque converter. An initial investigation of the vibration measured on the torque converter has been carried out to identify its vibration properties in order to enable its health monitoring to prevent failure. Initial signal analysis of the data have been carried out using Order Power Spectrum and Order Modulation Spectrum methods. The results indicate that the torque converter vibration properties contain information relevant for early fault detection. Fastelaboratoriet - VINNEXC

With increasing complexities 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 code generated when a failure occurs. The axle is one of 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. Vibration is measured on the axle. Analysis of the data 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. In this way; 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. Fastelaboratoriet - VINNEXC

Godkänd; 2015; 20150303 (jlm) Fastelaboratoriet - VINNEXC

Godkänd; 2014; 20140819 (jlm)

Magnetic Resonance Imaging (MRI) scanner is one of the most important tools in clinical diagnostics. MRI scanners are associated by strong vibration which results in unpleasant and disturbing acoustic noise. The primary source of this vibration is the Lorentz force produced by fast switching of the currents inside the gradient coils of MRI scanners under a strong static magnetic field. During an MR-imaging scan the switching is controlled in order to spatially code the hydrogen nuclei that will generate the signal, which is reconstructed into anatomical images. Faster switching of the currents allows for shorter scan times and/or higher image resolutions. Consequently, the clinical quality has motivated the drive for shorter switching time and higher currents. This development, however, has also caused an undesired increase of MRI vibrations. The overall vibration phenomenon of an installed fully functional MRI scanner system becomes unique because of the installed location and ambiance. This vibration can potentially degrade the image quality and hence the diagnosis. Apart from the vibration produced, the associated annoying acoustic noise may not only affect the patients under examination and the clinical staff, but may also be transmitted to other parts of the building and causing discomfort for the personnel working there. In order to devise an effective isolation plan or improve an existing one both for vibration and acoustic noise it is important to study the noise and vibration transfer paths. This paper concerns an investigation of vibration transfer paths for vibration excited by an installed functional MRI scanner at a medical facility. The vibration transfer paths have been investigated experimentally. The obtained results are presented and discussed.

The remotely controlled laboratory setup for Active Noise Control (ANC) developed by Blekin-ge Institute of Technology, Sweden provides an efficient learning platform for the students to implement and learn ANC algorithms with real world physical system, hardware and signals. The initial laboratory prototype based on a Digital Signal Processor (DSP) TMS320C6713 from Texas Instruments (TI) was successfully tested with Filtered-x Least Mean Square (F-XLMS) algorithm applied to control noise in a ventilation duct. The resources of the DSP platform used in the remote laboratory setup enable testing and investigating substantially more challenging and computationally demanding algorithms. In this paper, we expand the horizon of the laboratory setup by testing more advanced and complicated single channel feed forward ANC algorithms. Filtered-x versions of algorithms such as the normalized least mean square (N-LMS), leaky least mean square (L-LMS), Filtered-U recursive least mean square (FURLMS) and recursive least square (RLS) algorithm etc. have been implemented utilizing the remote web based client provided in the remote laboratory. A comprehensive performance comparison of the aforementioned algorithms for the remote laboratory setup is presented to demonstrate the viability of the remote laboratory.

Remotely controlled laboratories in educational institutions are gaining popularity at an exponential rate due to the multidimensional benefits they provide. The Virtual Instrument Systems in Reality (VISIR) project by Blekinge Institute of Technology (BTH) Sweden has successfully implemented remotely controlled laboratories, with remotely controlled real instruments and experimental setups. Currently these laboratories provide students the opportunity to conduct experiments in the field of electronics, antenna theory and mechanical vibration measurements. In this paper a prototype system of a remotely controlled laboratory for active noise control (ANC) is introduced. The proposed lab will focus on addressing the problem of a ventilation duct noise. The laboratory is informative and to a great extent introduces a student to the general steps in ANC when it is suggested as a plausible solution for a noise problem. The student can perform an investigation concerning feasibility of active control, design, configuration and implementation of an active control system. The laboratory is based on a modern and relevant DSP platform with the corresponding software development environment controlled remotely. In addition, it may be utilized remotely both for lab assignments in acoustics courses and digital signal processing courses.

With the increaed numbers of nuclear facilities have been closed and are being or are going to be decommissioned, it is required to characterise the produced nuclear waste for its treatment by identification of the radionuclides and qualitatively determine them. Of the radionuclides related to these activities, the pure beta and alpha emitters have to be chemical separated from the matrix and other radionuclides before measurement. Although much effort has been carried out, the accurate determination of them is still a major challenge because of the complex matrix and high requirement in radiochemical separation of radionuclides. In order to improve and maintain the Nodic competence in analysis of radionculides in waste samples, a NKS B project on this topic was launched in 2009. During the first phase of the NKS-B RadWaste project (2009-2010), a good achivement has been reached on establishment of collaboration, identifing the requirements from the Nordic nuclear industries and optimizing and development of some analytical methods (Hou et al. NKS-222, 2010). In the year 2011, this project (NKS-B RadWaste2011) continued. The major achievements of this project in 2011 include: (1) development of a method for determination of long-lived 94Nb in the nuclear waste; (2) development of a sensitive method for measurement of 237Np using AMS; (3) improvement of analytical method for determinaiton of 99Tc using ICP-MS; (4) improvement of method for 14C measurement using LSC; and (5) Characterization of steel samples from Danish research reactor DK-3 for decommissioning. These progresses are summarized

In a narrow duct, a relatively simple single-channel feedforward ANC system may be used to attenuate noise propagating as plane waves. However, for ducts with larger dimensions the cut-on frequencies for one or several higher-order acoustic modes may be within the frequency range where ANC is applied. In such situations it is generally necessary to use a multiplechannel feedforward ANC system with several secondary sources, error sensors, and perhaps reference sensors. Such a system has a significantly higher complexity than a single-channel ANC system. In this paper another approach is described. Instead of using a multiple-channel feedforward ANC system on a duct of large dimension, the idea is to divide the duct into several more narrow parallel ducts. In this way the complexity of the ANC system may be reduced. In the experiments conducted for this paper, a duct was divided into two more narrow ducts. The noise propagating in each duct was controlled by a feedforward ANC system based on the leaky filtered-x LMS algorithm, where different reference- and error microphone configurations were used. The different configurations were compared to a configuration where the noise in respective narrow duct was controlled using a basic single-channel ANC system per duct. The results preliminary show that high attenuation of low-frequency noise in a duct of large dimension may be achieved using this approach.

The NKS-B RadWaste project was launched from June 2009. The ongoing decommisioning activities in Nordic coutries and current requirements and problems on the radiochemical analysis of decommissioning waste were discussed and overviewed. The radiochemical analytical methods used for determination of various radionculides in nuclear waste are reviewed, a book was written by the project partners Jukka Lehto and Xiaolin Hou on the chemistry and analysis of radionuclide to be published in 2010. A summary of the methods developed in Nordic laboratories is described in this report. The progresses on the development and optimization of analytical method in the Nordic labs under this project are presented.

Today mechanical ventilation systems are installed in many buildings to handle the ventilation. Such ventilation systems constitute a potential source of unwanted background noise in the buildings. In order to reduce the noise propagating through the ducts passive silencers are normally installed as a part of the ventilation system. However, the passive silencers are relatively ineffective in the low frequency range. A solution can be to use a combination of active noise control (ANC) and passive techniques where the ANC system extends the noise attenuation to include the low frequency noise. The construction of the ventilation systems can vary substantially between different buildings and may contain many different duct parts in different compositions etc. Hence, it may not be trivial to find a cost- and performance efficient installation of an ANC system in a ventilation system, e.g. to find a proper installation position of it and suitable passive silencers to combine it with, finding out if one or several ANC systems should be used, and so on. In order to make the design of a complete ventilation system (including one or several ANC systems) cost- and time efficient, an adequate mathematical model of the duct is required. The purpose of the model is to describe sound propagation in the duct. Such model can be built e.g. based on the two-port theory or by finite element method. In this paper initial investigations concerning modelling of standard duct parts were performed. Simulations were carried out to find parameters such as Noise Reduction etc., using both plane wave two-port theory and finite element modelling. The results of the simulations were compared with measurement results.

This paper is intended for people who are interested in using online remote laboratories in education. Blekinge Institute of Technology (BTH) have started a cooperation together with the Upper Secondary School, Katedralskolan, in Lund, Sweden. The purpose of the cooperation is to introduce remote laboratory environment for students at Katedralskolan. A remote laboratory (RL) in electronic is used as a complement to the traditional workbench. It is open 24/7 and the students can carry out laboratory assignments without any risks of damaging any equipment. When a student is familiar with the instruments and components in a laboratory assignment, and carried out parts of the experiments in the hands-on laboratory in school she/he may use the RL to finish the laboratory assignment. The students may also carry out additional experiments remote laboratory or use it to prepare for an exam.

In many different applications and buildings fans are used to remove unwanted and used air. These fans often generate broadband and tonal noise. Commonly, passive resistive silencers are used to attenuate noise generated by different types of fans installed in ventilation systems. Passive silencers tend to become bulky and impractical when designed for low frequency attenuation. However, active noise control (ANC) is a technique known for its ability to produce high levels of attenuation in the low frequency range, even with a relatively moderate sized ANC system. This paper presents an initial study performed to investigate the possibilities of applying ANC to a radial fan installed inside a box, an insulated box fan. The box is connected to a duct system and can for example be used as a waste air fan. The primary interest in this application, when the fan is used as a waste air fan, is to attenuate the noise generated on the suction side, since that side generates noise into a particular room. Investigations were carried out to determine where the ANC system should be installed, e.g. inside the box, in the duct connected to the box etc. Factors considered were for example, turbulence, standing waves, the type of noise generated by the fan (tonal, broadband, or a combination), and space limitations. The noise generated by the fan was found to be dominated by a tonal component, but also to have broadband energy in the low frequency range. Further, a feedforward ANC system was applied on the suction side, producing approximately 28 dB attenuation of the tonal component, and 5-10 dB attenuation of the broadband noise between 50 and 200 Hz.

Vibration problems during metal cutting occur frequently in the manufacturing industry. The vibration level depends on many different parameters such as the material type, the dimensions of the workpiece, the rigidity of tooling structure, the cutting data, and the operation mode. In milling, the cutting process subjects the tool to vibrations, and having a milling tool holder with a long overhang will most likely result in high vibration levels. As a consequence of these vibrations, the tool life is reduced, the surface finishing becomes poor, and disturbing sound appears. In this report, an investigation of the dynamic properties of a milling tool holder with moderate overhang has been carried out by means of experimental modal analysis and vibration analysis during the operating mode. Both the angular vibrations of the rotating tool and the vibrations of the machine tool structure were examined during milling. Also, vibration of the workpiece and the milling machine was examined during cutting. This re- port focuses on identifying the source/sources of the dominant milling vibration components and on determining which of these vibrations that are related to the structural dynamic properties of the milling tool holder.

To utilize the full noise attenuation potential of an active noise control (ANC) system applied to duct noise, it is important to be able to minimize the turbulence induced noise in the microphone signals. This is the second paper in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts, when applying ANC to ducts. Part I contains theoretical and experimental investigations of the influence of the turbulence induced noise on the filtered-x LMS algorithm used in the ANC system. Part II (the present paper) is concerned with design and investigations of microphone installations which produces a sufficient amount of turbulence suppression while also meeting industry requirements. These requirements are, for example, that the microphone installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s. Also published in IJAV. The authors wish to acknowledge IIAV to which the copyrights are transferred to, for approving publication in this database as well.

Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system. Part II is concerned with design and investigations of microphone installations for turbulence suppression and results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s. Also published in IJAV. The authors wish to acknowledge IIAV to which the copyrights are transferred to, for approving publication in this database as well.

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.

Low noise level is an essential feature when installing ventilation systems today. Since the passive silencers traditionally used to attenuate ventilation noise tend to become bulky, impractical, and expensive when designed for low frequency attenuation, other solutions for the reduction of the low frequency duct noise often present in ducts are of interest. Active noise control (ANC) is a well known method for attenuating low frequency noise and much research has been performed to successfully apply ANC to duct noise. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is of highest importance to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. The work presented in this report is concerned with analysis of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system, and design of microphone installations which produce sufficient turbulence suppression while also meeting industrial requirements. These requirements are, for example, that the installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation of duct noise achieved with ANC was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s.

The hydro power in Sweden today is facing higher demands on efficiency and reliability, while at the same time the hydro power stations today serve as a ”power reserve” and can be forced to several starts & stops each day. This demands a greater knowledge of the rotordynamical properties of the hydro power units, with for example higher accuracy in predicting the eigenfrequencies. When modelling a hydro power unit today, all bearings are usually modelled as purely radial which is not entirely true. In this thesis the influence of the combi-bearing is studied. The combi-bearing consists of a radial and an axial part - which, in comparison with the purely radial model, introduces a bending stiffness. The bending stiffness affects some of the eigenfrequencies of a hydro power unit and it is concluded that the frequencies with a corresponding eigenvector with large angular-amplitudes in the combi-bearing are affected the most. The combi-bearing is then allowed to have a misalignment in the foundation and the effects of this misalignment are studied. It is shown that a misalignment will cause a coupling between the vibration-modes, making it possible for a lateral excitation to generate an axial vibration and vice versa. The thesis consist of an analytical part where a model of the combibearing is achieved and of a numerical part where the results of the mentioned model are studied. Validerat; 20101217 (root)

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).

This paper presents a feedforward active noise control system combined with passive silencers for reducing acoustic noise propagating through ventilation ducts. It is investigated if the passive silencers can increase the noise attenuation potential of the active noise control system and experimental results are presented. The results show that installing a passive silencer results in less pronounced standing waves in the duct and hence to performance increase of the active noise control system. Evaluating measurements regarding the performance of the active noise control system have also been conducted in an acoustic laboratory according to an ISO-standard.

This paper is intended for people who are interested in creating online laboratories. 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 organisations. The VISIR open source distribution 2007 includes software for two implemented examples, one laboratory for low frequency electronics and one for signal processing. The distribution is modular and many modules can be used for other online laboratories. The goal is an international standard, enabling teams worldwide to expand and jointly develop this powerful approach into distributed online laboratories. Each laboratory is a client/server application controlled by an administrative system. These three parts are mainly written in Adobe Flash, C++, and PHP respectively. However, the hardware control module of the equipment server is written in LabVIEW. This paper describes the organisation of the software.

Ventilation systems installed in buildings usually generate low-frequency noise because the passive silencers commonly used to attenuate the ventilation noise are not effective in the low-frequency range. A method proven to effectively reduce low-frequency noise in a wide variety of applications is active noise control (ANC). A feedforward ANC system applied to duct noise normally uses a reference microphone, a control unit, a loudspeaker to generate the secondary noise created by the controller, and an error microphone. The secondary noise generated by the loudspeaker will travel both downstream canceling the primary noise, and upstream to the reference microphone, i.e. acoustic feedback. The acoustic feedback may result in performance reduction and stability problems of the control system. Common approaches to solve the feedback problem result in more complex controller structures and/or system configurations than the simple feedforward controller, e.g. introducing a feedback cancellation filter in the controller in parallel with the acoustic feedback path, or using a dual-microphone reference sensing system. This paper presents a simple approach to reduce the acoustic feedback by using a basic feedforward controller in combination with a passive silencer. Simulations show that efficient acoustic feedback cancellation is achieved by using a passive silencer. In the experimental setup another advantage with using a passive silencer is that the frequency response function of the forward path, which is to be estimated, is smoother, i.e. most of the dominant frequency peaks in the frequency response function when not using a passive silencer is reduced. This in turn results in an acoustic path that is less complex to estimate with high accuracy using an adaptive FIR filter steered with the LMS algorithm.

The boring bar is one of the most widely used type of tool holders in metal cutting operations. The turning process subjects the tool to vibrations, and cutting in deep workpiece cavities is likely to result in high vibration levels. The consequences of such vibration levels generally results in: reduced tool life, poor surface finishing and disturbing sound. Internal turning frequently requires a long and slender boring bar in order to machine inside a cavity, and the vibrations generally become highly correlated with one of the fundamental bending modes of the boring bar. Different methods can be applied to reduce the vibrations, the implementation of the most efficient and stable methods require in depth knowledge concerning the dynamic properties of the tooling system. Furthermore, the interface between the boring bar and the clamping house has a significant influence on the dynamic properties of the clamped boring bar. This report focuses on the dynamic properties of a boring bar that arise under different clamping conditions of the boring bar and are introduced by a clamping house (commonly used in the manufacturing industry). The dynamic properties of a boring bar (for different cases of boundary condition of the boring bar) are presented partly analytically but also experimentally.

Vibration problems occurring during internal turning operations in the manufacturing industry urge for adequate passive and/or active control techniques in order to increase the productivity of machine tools. Usually, passive solutions are based on either boring bars made partly in high Young's modulus non-ductile materials such as intered tungsten carbide or boring bars with tuned vibration absorbers adjusted to increase the dynamic stiffness in the frequency range of a certain resonance frequency of the boring bar. By utilizing an active boring bar with an embedded piezoceramic actuator and a suitable controller, the primary boring bar vibrations originating from the material deformation process may be suppressed with actuator-induced secondary "anti-" vibrations. In order to design an active boring bar, several issues have to be addressed, i.e., selecting the characteristics of the actuator, the actuator size, the position of the actuator in the boring bar, etc. This usually implies the manufacturing and testing of several prototypes of an active boring bar, and this is a time-consuming and costly procedure. Therefore, mathematical models of active boring bars incorporating the piezo-electric effect that enable the accurate prediction of their dynamic properties and responses are of great importance. This report addresses the development of a "3-D" finite element model of the system "boring bar-actuator-clamping house". The spatial dynamic properties of the active boring bar, i.e., its natural frequencies and mode shapes, as well as the transfer function between actuator voltage and boring bar acceleration are calculated based on the "3-D" FE model and compared to the corresponding experimentally obtained estimates. Two types of approximations of the Coulomb friction force, the arctangent and the bilinear models, are evaluated concerning modeling contact between the surface of the boring bar and the clamping house.

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.

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. Elektronik, ingenjörsutbildning, distanslaboratorium, signalbehandling, vibration Open Access Journal

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.

A request on ventilation systems today is the feature of a low noise level. A common method to attenuate ventilation noise is to use passive silencers. However, such silencers are not suitable for the lowest frequencies and one solution is to use active noise control (ANC) to increase the noise attenuation in the low frequency range. Normally when using a feedforward ANC system to attenuate duct noise, both the reference microphone and the error microphone are exposed to airflow. As the airflow excites the diaphragm of the microphones, the microphone signals become contaminated by uncorrelated pressure fluctuations that are not part of the sound propagating in the duct. By reducing the flow velocity around the microphones, these uncorrelated pressure fluctuations can be reduced and the noise reduction improved. One way to reduce the flow velocity around the microphones is to place the microphones in outer microphone boxes connected to the duct via a small slit. In this paper a new practical design for the reduction of flow velocity around the microphones is presented; the microphone installation is based on a T-duct, and therefore it makes maintenance and especially construction easier, compared to the microphone box with a slit. Furthermore, comparative results concerning the performance of an ANC system for the two different microphone installations, the T-duct configurations and the microphone boxes with varying slit width, are presented. The results show that the active noise control performance is almost equal when using the suggested microphone installation as compared to when using a microphone box with a slit.

This contribution presents a fixed point implementation for acoustical active noise control in hearing defenders. The well known filtered-x least mean squares structure is conformed to fixed point arithmetic and evaluated in real time. The measured performance of the implementation is 20dB to 30dB attenuation of broad band noise and ca 60dB for sinusoidal interference. The implementation uses a low power fixed point digital signal processor and is well suited for industry application.

Low noise level is an essential feature when installing ventilation systems nowadays. The traditional noise control approaches use passive silencers to attenuate the undesired ventilation noise. These silencers have a high attenuation over a broad frequency range. However, traditional passive silencers are ineffective at low frequencies and tend to be relatively large and bulky when they are used for low frequencies. An approach to improve the low frequency noise attenuation and to reduce the size of a low frequency silencer is active noise control (ANC). A problem when applying ANC to attenuate noise in ducts is that both the reference microphone and the error microphone are placed in an air flow. Accordingly, the microphones sense the sound propagating through the duct as well as the turbulent fluctuations generated by the wind passing over the microphones. The turbulent flow noise reduces the coherence between the reference microphone and the error microphone, resulting in reduced performance of a feedforward ANC system. For improving the performance it is important with as little corruption from turbulent flow noise as possible. The coherence can be improved by reducing the flow velocity around the microphones by using some kind of windscreen. This paper presents comparison results for microphone installations based on different windscreens for suppression of the turbulent wind noise. The presented measurements are carried out in the frequency range 0-400 Hz - the plane wave propagation region for the ducts in use - and for flow speeds up to 5,9 m/s. The results show that with appropriate screens and placement the attenuation and frequency range of attenuation can be significantly improved.

In metal cutting operations tool vibration is a frequent problem. Vibrations appear under the excitation applied by the material deformation process during the machining of a workpiece. In order to perform an internal turning or boring operation, e.g. in a pre-drilled hole in a workpiece, it is generally required that the boring bar should be long and slender; therefore it is easily subjected to vibrations. These vibrations will affect the result of machining, in particular the surface finish, and also the tool life may be reduced. As a result of tool vibration severe acoustic noise frequently occurs in the working environment. The vibration problem is to a large extent related to the boring bar low-order fundamental bending modes. In order to control boring bar vibrations in the primary cutting direction an analog and a digital feedback controllers have been used. In both approaches an active boring bar with a built-in actuator has been used. In order to measure the response of the active boring bar, accelerometers are mounted nearby the area, where the excitation force is applied due to material deformation process. This means that in either approach the boring bar vibrations are attenuated actively by the controlled secondary anti-vibrations induced by the actuator. The digital controller, based on the feedback filtered-x LMS-algorithm, manages to reduce the boring bar vibrations in the primary cutting direction by up to approximately 44 dB at the first bending resonance frequency. The analog controller, based on a flexible orthogonal gain and phase lag compensation, results in an attenuation of the boring bar vibrations in the primary cutting direction by up to approximately 40 dB at the first bending resonance frequency. Both controllers also suppress all the harmonics of the first bending resonance frequency. Vibration attenuation performances of the two controllers are compared and discussed.

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.

The problem of low- frequency lateral train-car vibration is an important issue surrounding the design of high-speed trains. Passive solutions such as stiffening the car chassis are impractical because of the weight increase. Semi-passive solutions, such as modifying the structural dynamics of the carboy through non-rigid coupling of heavy underfloor equipment does not come with a weight penalty, but do not sufficiently reduce the vibrations. However, computer simulations based on signals derived from a dynamic computer model of a train car indicates that the incorporation of a feedforward active control system, is likely to introduce a substantial reduction in the lateral vibration level. A simple controller structure is used and it is based on the multiple- input/single-output filtered-x LMS algorithm. Active control results illustrate an attenuation of the lateral train-car vibration by up to 14 dB.

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. In all cutting operations like turning, boring and milling vibrations are induced due to the deformation of the workpiece. This implies several disadvantages, economical as well as environmental. Many different solutions to minimize the problem have been developed but the fundamental problem is still there. The true nature of the vibrations, its causes, and implications were revealed in a doctor’s thesis in 1999, [1]. This has led to a break through in this research area. Since then, through recent research results at Blekinge Institute of Technology, a new approach to controlling vibrations in cutting operations in a lathe has been implemented in a product called Acticut®, developed by Active Control Sweden AB. This new method controls vibrations in the cutting direction using embedded sensors and actuators and a filtered-x LMS algorithm. This paper will discuss the application but also the algorithm and its main numerical properties to accomplish a good result, still maintaining its stability properties.

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. In all cutting operations like turning, boring and milling vibrations are induced due to the deformation of the workpiece. This implies several disadvantages, economical as well as environmental. Many different solutions to minimize the problem have been developed but the fundamental problem is still there. The true nature of the vibrations, its causes, and implications were revealed in a doctor’s thesis in 1999. This has led to a break through in this research area. Since then, through recent research results at Blekinge Institute of Technology, a new approach to controlling vibrations in cutting operations in a lathe has been implemented in a product called ActicutTM, developed by Active Control Sweden AB. This new method controls vibrations in the cutting direction.

Vibrations in internal turning or boring operations are usually a cumbersome part of the manufacturing process. The manufacturing industries are having problems with these kinds of cutting operations. When cutting in pre-drilled holes the cross sectional area of the boring bar is limited at the same time as it is long. Since a general boring bar is long and slender it is sensitive to external excitation and thereby inclined to vibrate. The vibration problem affects the surface finish in particular. The demand for smaller and smaller tolerances of the surface finish leads to that the manufacturing industry seeks for a solution to the boring bar vibration problem. The tool life is also likely to be influenced by the vibrations involved in a cutting operation. Another problem in boring operations is the high noise level in the cutting process. The noise level in the environment of the operators is today more and more regulated, especially in the western world. Active vibration control will reduce the amount of vibrations in the cutting operations. Since the noise is induced by the vibration of the boring bar, the noise level will also be reduced due to the cancellation of the noise source. Preliminary results show reduction of vibrations in the boring bar by up to 30dB.

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.

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.

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.

Internal turning or boring operations have a history of being a cumbersome manufacturing process. The manufacturing industries are facing tougher tolerances of their product surfaces and a desire to process hard to cut materials and therefore the vibrations must be kept to a minimum. An increase in the productivity is also interesting from a production point of view. When cutting in pre-drilled holes the boring bar is usually long and slender and is thereby inclined to vibrate destructively concerning the machining result. The knowledge of the vibrations involved in boring operations and active control of external turning operations, have given a good basis for the active control solution in boring operations. The active control solution is based on a standard boring bar with an embedded piezo ceramic actuator placed at the peak modal strain of the boring bar. An accelerometer is also included in the design, mounted as close as possible to the cutting tool. The control algorithm is a filtered X LMS algorithm built on a feedback approach since the original excitation, the cutting process, cannot be observed directly. Preliminary results show reduction of the vibration in the boring bar by up to 30dB.

In the general lathe the turning operation chatter or vibration is a frequent problem affecting 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 a general lathe the physical features and properties of an ctive control system usually limit their applicability. By using piezo ceramic actuators some constraints regarding the mechanical construction of the active tool holder can be circumvented. An active control solution for a general lathe application has been developed. It is based on a standard industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.

The problem of low-frequency lateral train-car vibration is an important issue surrounding the design of high-speed trains. Passive solutions such as stiffening the car chassis are impractical because of the weight increase. Semi-passive solutions, such as modifying the structural dynamics of the carbody through non-rigid coupling of heavy underfloor equipment does not incur a weight penalty, but does not sufficiently reduce the vibrations. However, computer simulations based on signals derived from a dynamic computer model of a train car indicates that the incorporation of a multiple-reference feedforward active control system, in addition to the semi-passive approach, is likely to effect a substantial reduction in the lateral vibration level. The complexity of the control system may be reduced by using a robust feedback-LMS controller. Results from computer simulations indicate that a feedback system would function as well as, and potentially better than, a feedforward system. The control results illustrate attenuation of the lateral train-car vibration of up to 15 dB.

In the turning operation chatter or vibration is a frequent problem affecting 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. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limit their applicability. An active control solution for a general lathe application has been developed. It is based on a standard Industry tool holder with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.

In the turning operation chatter or vibration is a common problem affecting 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. However, machine-tool vibration control systems are usually not applicable to a general lathe and turning operation. The physical features and properties of the mechanical constructions or solutions involved regarding the introduction of secondary vibration usually limt their applicability. An adaptive active control solution for a general lathe application has been developed. It is based on a standard industry tool holder shank with an embedded piezo ceramic actuator and an adaptive feedback controller. The adaptive controller is based on the well known filtered-x LMS-algorithm. It enables substantial reduction of the vibration level by up to 40 dB at 3.4 kHz.