Lars Håkansson

Identification of dynamic properties of boring bar vibrations in a continuous boring operation

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, stai ...

RFI Suppression in Ultrawideband SAR Using an Adaptive Line Enhancer

In this letter, we propose an approach to suppress radio-frequency interference (RFI) in ultrawideband (UWB) low-frequency synthetic aperture radar (SAR). According to the proposal, RFI is suppressed by using an adaptive line enhancer controlled by the normalized least mean square algorithm. The approach is tested successfully on real UWB low-frequency SAR data. In order to keep the computational burden down, possible ways to integrate the RFI suppression approach into SAR imaging algorithms are also suggested.

Adaptive feedback control of machine-tool vibration based on the filtered-x LMS-algorithm

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.

Analog versus Digital Control of Boring Bar Vibration

In workshops where metal cutting is performed, the machining processes frequently introduces productivity degrading vibration problems and annoying sound, sometimes almost at unbearable levels. Besides producing disturbing noise, the vibrations affect the surface finish of the workpiece and the tool life. Two different approaches based on feedback control are investigated, both applied for the control of an active boring bar. The first approach is based on a digital adaptive feedback controller; the feedback filtered-X LMS algorithm. The second approach is based on an analog controller; a feedback controller with gain and phase orthogonally adjustable, thus flexible for the control of systems with different dynamic properties. Based on open loop frequency response function estimates, robustness and stability of both the digital and the analog feedback control system are discussed. A comparison of the two controllers concerning their boring bar vibration attenuation performance shows that the analog controller attenuates the vibration in same order of magnitude as the digital controller which is approximately by up to 40 dB.

Displacement measurements versus time using a remote inclined plane laboratory

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.

Enhancement of remotely controlled laboratory for Active Noise Control and acoustic experiments

The latest important developments in the remotely controlled Active Noise Control (ANC) and Acoustics laboratory at Blekinge Institute of Technology (BTH), Sweden, are introduced. The remotely controlled laboratory is based on the Virtual Instruments Systems in Reality (VISIR) concept, and concerns multi-channel measurement and control of the sound field in a heating ventilation and air conditioning (HVAC) duct. Originally the ventilation duct was equipped with a fixed number of microphones at fixed spatial locations in the duct. A microphone positioning system has been designed and implemented. It enables control of the spatial positions of a number of microphones inside the HVAC duct using a suitable web interface for controlling stepper motors via a National Instruments (NI) PXI system. With the new developments, the spatial number of selectable positions for the microphones have been extended substantially. The new microphone positioning control system is presented and to enhance the user interaction with the laboratory equipment, an audio and visual system is also proposed.

Remotely controlled laboratory setup for Active Noise Control and acoustic experiments

This paper presents a remotely controlled educational experiments setup for Active Noise Control (ANC) and acoustic experiments. The experiments setup is based on the Virtual Instruments Systems in Reality (VISIR) open source platform, National Instruments LabVIEW software and a Digital Signal Processor TMS320C6713 from Texas Instruments. The software development and equipment are controlled remotely form a client PC using a standard web browser. The proposed laboratory setup focuses on ANC experiments applied to noise in a ventilation duct. The laboratory setup will enable students to test and investigate properties and behaviour of adaptive algorithms in reality as compared to more confined simulations usually carried out in Matlab etc. The general steps in ANC, such as the feasibility of active control, designing, testing and debugging ANC algorithms, configuration and implementation of an active control system, are all covered. In addition students will be able to study the effect of analog to digital converters (ADC), anti-aliasing filters, digital to analog converters (DAC) and reconstruction filters using digital signal processing in reality, etc. The laboratory setup is suitable for a wide range of courses such as sound related experiments in upper secondary school physics, digital signal processing, adaptive signal processing, and acoustics at university level.

Expert Competence in Remote Diagnostics - Industrial Interests, Educational Goals, Flipped Classroom & Laboratory Settings

The manufacturing industry are dependent of engineering expertise. Currently the ability to supply the industry with engineering graduates and staff that have an up-to-date and relevant competences might be considered as a challenge for the society. In this paper an education approach is presented where academia - industry - research institutes cooperate around the development and implementation of master level courses. The methods applied to reach the educational goals, concerning expert competence within remote diagnostics, have been on site and remote lectures given by engineering, medical and metrology experts. The pedagogical approach utilized has been flipped classroom. The main results show that academic courses developed in cooperation with industry requires flexibility, time and effort from the involved partners. The evaluation interviews indicate that student are satisfied with the courses and pedagogical approach but suggests more reconciliation meetings for course development. Labs early in the course was considered good, and division of labs at the system and the component level. However further long-term studies of evaluation of impact is necessary.

Performing active noise control and acoustic experiments using real test setup via the Internet

In In this demo session, it will be shown how to perform Active Noise Control (ANC) and various important Acoustic experiments remotely on the remotely controlled ANC laboratory developed by Blekinge Institute of Technology, Sweden. An important consideration in ANC is the active controls performance dependence on the spatial position of the reference and error sensors, etc. This will be highlighted particularly. This feature is recently implemented using stepper motors which can be controlled via the Internet. It will be demonstrated how to write and upload active noise control algorithms e.g. Filtered-X Least Mean Square (FXLMS) to a digital signal processors (DSP) board. For the acoustic experiments various interesting acoustic properties such as waveforms, speed of sound, mode shapes and sound pressure spectra may be measured. A short guide about the measurements and PowerPoint presentation will be provided during the demo to facilitate for the users. The Lab setup and the equipment will be shown to the user using Skype and a web camera.

Development and implementation of an advanced remotely controlled vibration laboratory

Currently an advanced remotely controlled vibration laboratory is developed and implemented at Blekinge Institute of Technology, Karlskrona, Sweden. The new developments in the laboratory setup will provide users to carry out vibration measurements on a cantilever beam system with remotely adjustable dynamic properties and to estimate dynamic characteristics of it. The dynamic properties of the cantilever beam are remotely modified by attaching structural parts such as a block of mass, a spring mass system and a non-linear spring. In the development of this remote-lab, a number of different approaches were adopted for the production of well-defined experiments. Also, the new prototype laboratory is designed based on finite elements modeling (FEM) and LABVIEW. The test object, attachment mechanism for sub structures, relevant experiments, and proper interface for managing the lab via Internet and many other things have been considered.