| 21. |
- Björklund, Svante, 1968-
(författare)
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Signal Processing for Radar with Array Antennas and for Radar with Micro-Doppler Measurements
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radar (RAdio Detection And Ranging) uses radio waves to detect the presence of a target and measure its position and other properties. This sensor has found many civilian and military applications due to advantages such as possible large surveillance areas and operation day and night and in all weather. The contributions of this thesis are within applied signal processing for radar in two somewhat separate research areas: 1) radar with array antennas and 2) radar with micro-Doppler measurements.Radar with array antennas: An array antenna consists of several small antennas in the same space as a single large antenna. Compared to a traditional single-antenna radar, an array antenna radar gives higher flexibility, higher capacity, several radar functions simultaneously and increased reliability, and makes new types of signal processing possible which give new functions and higher performance.The contributions on array antenna radar in this thesis are in three different problem areas. The first is High Resolution DOA (Direction Of Arrival) Estimation (HRDE) as applied to radar and using real measurement data. HRDE is useful in several applications, including radar applications, to give new functions and improve the performance. The second problem area is suppression of interference (clutter, direct path jamming and scattered jamming) which often is necessary in order to detect and localize the target. The thesis presents various results on interference signal properties, antenna geometry and subarray design, and on interference suppression methods. The third problem area is measurement techniques for which the thesis suggests two measurement designs, one for radar-like measurements and one for scattered signal measurements.Radar with micro-Doppler measurements: There is an increasing interest and need for safety, security and military surveillance at short distances. Tasks include detecting targets, such as humans, animals, cars, boats, small aircraft and consumer drones; classifying the target type and target activity; distinguishing between target individuals; and also predicting target intention. An approach is to employ micro-Doppler radar to perform these tasks. Micro-Doppler is created by the movement of internal parts of the target, like arms and legs of humans and animals, wheels of cars and rotors of drones.Using micro-Doppler, this thesis presents results on feature extraction for classification; on classification of targets types (humans, animals and man-made objects) and human gaits; and on information in micro-Doppler signatures for re-identification of the same human individual. It also demonstrates the ability to use different kinds of radars for micro-Doppler measurements. The main conclusion about micro-Doppler radar is that it should be possible to use for safety, security and military surveillance applications.
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| 22. |
- Borgh, Markus, 1983-, et al.
(författare)
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An improved adaptive gain equalizer for noise reduction with low speech distortion
- 2011
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Ingår i: EURASIP Journal on Audio, Speech, and Music Processing. - : Springer. - 1687-4714 .- 1687-4722. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In high-quality conferencing systems, it is desired to perform noise reduction with as limited speech distortion as possible. Previous work, based on time varying amplification controlled by signal-to-noise ratio estimation in different frequency subbands, has shown promising results in this regard but can suffer from problems in situations with intense continuous speech. Further, the amount of noise reduction cannot exceed a certain level in order to avoid artifacts. This paper establishes the problems and proposes several improvements. The improved algorithm is evaluated with several different noise characteristics, and the results show that the algorithm provides even less speech distortion, better performance in a multi-speaker environment and improved noise suppression when speech is absent compared with previous work.
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| 23. |
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| 24. |
- Borgh, Markus, 1983-, et al.
(författare)
-
The Effect of Own Voice on Noise Dosimeter Measurements : A Field Study in a Day-Care Environment, Including Adults and Children
- 2008
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Konferensbidrag (refereegranskat)abstract
- Noise dosimeters are valuable tools in assessing the individual noise dose in the workplace. At non-industrial work places with a high degree of communication, such measurements would include the wearer’s own voice which would be registered as noise. This may not always be desirable. The purpose of this investigation was to study the effect of the wearers own voice in noise dosimeter measurements, and especially the difference between children and adults as test subjects. The study took place at a day-care center and sixteen children and thirteen adult female preschool teachers participated. The participants wore a digital recorder during the day, which recorded the sound signal and vibrations originating from an accelerometer attached to the neck of the test subjects, for distinguishing of whether the subject was speaking or not. Thus, average A-weighted noise levels with and without the influence of the subjects own voice could be obtained. The Leq for the measurements with and without the own voice was 84.6 dBA and 72.2 dBA for the children, respectively, and 79.3 dBA and 70.0 dBA for adults. Student’s t-test showed a significant (p<0.01) difference of 12.4 dBA for children and 9.3 dBA for adults when comparing measurements including and excluding the own voice and also that the difference was significantly larger for children. Thus, the study conclude that the influence from the own voice implied an augmentation of the Leq value and that there is a significant difference between children and adults in how large this augmentation is.
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| 25. |
- Brandt, Anders, et al.
(författare)
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Cyclostationary Analysis of Boring Bar Vibrations
- 2004
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Konferensbidrag (refereegranskat)abstract
- Internal turning or boring operation is a common metal working process that is usually associated with vibration problems. The vibration problems in internal turning considerably influence important factors such as surface quality, productivity, production costs, etc. In order to gain further understanding of the dynamic metal cutting process, an important early step is to thoroughly classify the vibrations. Boring bar vibrations have previously been proven to be nonstationary when analyzed with traditional methods. For vibrations originating in a combination of a rotating workpiece and random material inhomogeneities, it can be anticipated that the vibrations have cyclostationary properties. Methods for analysis of cyclostationary signals have rendered an increasing interest in the past decade, especially in the telecommunications field. However, very little has been published on the use of these methods in vibration applications. In this paper we show there is strong statistical evidence of cyclostationary behavior in vibrations on an operating boring bar. Methods for estimating the cyclic autocorrelation function and cyclic spectrum for sampled data are developed and results are compared. Some preliminary results from implementing these methods on operating boring bar vibrations are also presented.
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| 26. |
- Claesson, Ingvar, et al.
(författare)
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A Multi-DSP implementation of a Broadband Adaptive Beamformer for use in a Hands-free Mobile Radio Telephone
- 1991
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Ingår i: IEEE Transactions on Vehicular Technology. - New York : Institute of electrical and electronics engineers. - 0018-9545. ; 40:1, s. 194-202
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Tidskriftsartikel (refereegranskat)abstract
- An implementation of a broadband adaptive array on a multiprocessor digital signal processing (DSP) system for use in a hands-free mobile radio telephone is described. This implementation of a five-microphone adaptive Griffiths-Jim array can handle FIR filters with up to 128 taps behind each microphone at a sampling rate of 8 kHz. The filter structure makes it possible to combine an adaptive array with a noise canceler. The near-field problem has been solved by using focusing, a speech-controlled adaptive algorithm, and a short hourglass. Preliminary measurements indicate a considerable potential for this technique in hands-free mobile telephony. The array gives a 20-30-dB suppression of a broadband jammer covering 300-1100 Hz, even with three reflecting walls surrounding the microphone.
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| 27. |
- Claesson, Ingvar, et al.
(författare)
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A Spatial Filtering Approach to Robust Adaptive Beamforming
- 1992
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Ingår i: IEEE Transactions on Antennas and Propagation. - New York : Institute of electrical and electronics engineers. - 0018-926X. ; 40:9, s. 1093-1096
-
Tidskriftsartikel (refereegranskat)abstract
- This communication treats the problem of controlling the superresolution in adaptive beamformers. A straightforward method is presented that works for both narrow-band and broad-band arrays. The method is based on forming the blocking matrix in a general sidelobe canceller (GSC) structure using a spatial FIR filter. The suppression of this spatial filter and the implicit noise of the leaky (LMS) algorithm together determine the beamformer.
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| 28. |
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| 29. |
- Claesson, Ingvar, et al.
(författare)
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Active Control of Machine-Tool Vibration in a Lathe
- 1997
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Konferensbidrag (refereegranskat)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration is a frequent problem, which affects the result of the machining, in particular the surface finish. The tool life is also influenced by the vibrations. When the working environment is considered, noise is frequently introduced by dynamic motion between the cutting tool and the workpiece. By proper machine design, e.g. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control based on the filtered-x LMS-algorithm enables a reduction of the vibration with up to 40 dB at 1.5 kHz and simultaneously with approximately 40 dB at 3 kHz. A significant improvement of the workpiece surface was observed and a substantial improvement of the acoustic noise level was obtained with adaptive control.
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| 30. |
- Claesson, Ingvar, et al.
(författare)
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Adaptive Active Control of Machine-Tool Vibration In a Lathe
- 1998
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Ingår i: International Journal of Acoustics and Vibration. - 1027-5851 .- 2415-1408. ; 3:4, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control of tool vibration in the cutting speed direction, based on the filtered-x LMS-algorithm, enables a reduction in vibration, by up to 40 dB at 1.5 kHz, and by approximately 40 dB at 3 kHz. It was also observed that the introduction of leakage in the filtered-x LMS-algorithm improved the stability properties of the feedback control system. A significant improvement in the workpiece surface was observed and a substantial improvement in the acoustic noise level was obtained with adaptive control.
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