| 41. |
- Claesson, Ingvar, et al.
(författare)
-
Method and a device for vibration control
- 2004
-
Patent (populärvet., debatt m.m.)abstract
- A device for vibration control in a machine for internal turning uses a cutting tool supported by a tool holder, and has a control unit, a vibration sensor connectible to the control unit, and an actuator connectible to the control unit. The actuator has an active element, which converts an A.C. voltage supplied by the control unit to the actuator into dimensional changes. The active element is adapted to be embedded in the body of the tool holder, and is adapted to be embedded in such a manner that the dimensional changes impart bending to the body of the tool holder. A method for vibration control in internal turning and a tool holder for internal turning are provided.
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| 42. |
- Claesson, Ingvar, et al.
(författare)
-
Method and device for controlling a turning operation
- 2005
-
Patent (populärvet., debatt m.m.)abstract
- A device increases the surface smoothness of a turned surface. The device comprising a control system with a control unit and an actuator connectible to the control unit and connectible with a tool holder. The actuator in adapted to impart a vibrating motion in the lateral direction to the tool holder. A method will also increase the surface smoothness of a turned surface, comprising the step of controlling the vibrations of the tool holder during turning. The method also comprises the step of imparting a vibrating motion in the lateral direction to the tool holder. Moreover, a turning lathe and a turning tool holder which like the device are designed to generate vibrating motion in the lateral direction.
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| 43. |
- Claesson, Ingvar, et al.
(författare)
-
Method and device for vibration control
- 2008
-
Patent (populärvet., debatt m.m.)abstract
- A device and method for vibration control in a machine for cutting, said machine comprising a cutting tool supported by a tool holder. The device comprises a control unit and converting means which are connectible to the control unit and comprise a vibration sensor and an actuator. The actuator comprises an active element which converts an A.C. voltage supplied by the control unit to the actuator into dimensional changes. Said active element is adapted to be embedded in the body of the tool holder and in such manner that said dimensional changes impart bending to the body of the tool holder.
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| 44. |
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| 45. |
- Claesson, Ingvar, et al.
(författare)
-
Notch Filtering of Humming GSM Mobile Telephone Noise
- 2005
-
Konferensbidrag (refereegranskat)abstract
- A common problem in the world's most widespread cellular telephone system, the GSM system, is the interfering signal generated in TDMA cellular telephony. The infamous "bumblebee" is generated by the switching nature of TDMA cellular telephony, the radio circuits are switched on and off at a rate of approximately 217 Hz (GSM). This paper describes a study of two solutions for eliminating the humming noise with IIR notch filters. The simpler one is suitable for any exterior equipment. This method still suffers from a small residual of the noise, resulting from the IDLE slots of the sending mobile. The more advanced IIR structure for use within the mobile also eliminates this residual.
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| 46. |
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| 47. |
- Claesson, Ingvar, et al.
(författare)
-
Robust Control of Machine-Tool Vibration in a Lathe
- 1999
-
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, 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.
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| 48. |
- Claesson, Ingvar, et al.
(författare)
-
Wiener Solution for the Broadband Griffiths-Jim Beamformers
- 1990
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Konferensbidrag (refereegranskat)abstract
- The problem of finding the Wiener filters for a wideband adaptive beamformer is treated. Explicit expressions are given for the filters and the error power spectrum in the frequency domain. The expressions are simple to program and make it possible to investigate superresolution for wideband signals and to determine sufficient lengths of finite-impulse-response filters in adaptive arrays.
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| 49. |
- Cornelius, Per, et al.
(författare)
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A Spatially Constrained Subband Beamforming Algorithm for speech enhancement
- 2004
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Konferensbidrag (refereegranskat)abstract
- This paper discusses speech enhancement in an enclosed environment such as communication in a motorcycle helmet. A new constrained subband adaptive beamformer is proposed, which uses the concept of an earlier proposed calibrated beamformer mainly developed for a hands-free in-car environment. The highly non-stationary nature of the disturbing sound field encountered in an motorcycle helmet and the fact that the source is situated in the extreme nearfield of the array, causes the beamformer to produce an unwanted fluctuation in the output level. The spatially constrained beamformer proposed in this paper makes sure that the output maintains a constant gain, as long as the corresponding source originates from the desired location.
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| 50. |
- Cornelius, Per, et al.
(författare)
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Microphone array system for speech enhancement in a motorcycle helmet
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report a real case study of the sound environment within a helmet while driving motorcycle is investigated. A solution to perform speech enhancement is proposed for the purpose of mobile speech communication. A microphone array, mounted onto the face shield in front of the user's mouth, is used to capture the spatio-temporal properties of the acoustic wave ¯eld inside the helmet. The power of the spatially spread noise within the helmet is small when standing still while it may heavily exceed the power of the speech when driving at high speeds. This will result in dramatically reduced speech intelligibility in the communication channel. The highly dynamic noise level imposes a challenge for existing speech enhancement solutions. We propose a subband adaptive system for speech enhancement which consists of a soft constrained beamformer in cascade with a signal-to-noise ratio dependent single microphone solution. The beamformer make use of a calibration signal gathered in the actual environment from the speaker's position. This calibration procedure e±ciently captures the acoustical properties in the environment. Evaluation of the beamformer and the single microphone algorithm, both as either parts by them selves and as a cascaded structure, together with the optimal subband Wiener solution is presented. It is shown that a cascaded combination of the calibrated subband beamforming technique together with the single channel solution outperforms either one by it self, and provides near optimal results at all noise levels.
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