| 901. |
- Winberg, Mathias, et al.
(författare)
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A Feasibility Study of Applying Active Noise Control to a Fork-lift
- 2003
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Konferensbidrag (refereegranskat)abstract
- Modern fork-lift trucks incorporate a wide range of sophisticated passive techniques to reduce the noise inside the cabin. By the use of active noise control technologies it may be possible to even further reduce the noise level in total but also to attenuate certain tonal components, thereby improving the comfort for the truck driver. The paper discusses the noise situation inside the truck cabin as well as the active noise control strategy for a practical fork-lift truck installation. A feedforward control approach is used, along with several possible reference signals, forming a multiple reference controller.
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| 902. |
- Winberg, Mathias, et al.
(författare)
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Active Control of Engine Induced Noise in a Naval Application
- 2001
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Konferensbidrag (refereegranskat)abstract
- Engine induced sound and vibration levels in boats for professional and leisure use is in many cases unacceptably high in term of comfort and the environment. Classical methods for passive treatment are normally less effective due to the low frequency content and often leads to an increase in weight. This contradicts the requirements for lower weight for increased speed. More efficient vibration damping methods must therefore be found. With active engine mounts, it is possible to achieve a decrease in the vibrations even when the hull is not very stiff. This is especially important in marine applications since the engines are mounted on weak and light structures. The AVIIS project aims at investigating the effects of a combined passive/active engine mount for use in boats. A Storebro 36 Royal Cruiser with two Volvo Penta engines has been used in the project. An ASAC (Active Structure Acoustic Control) approach has been used. The sound level in the cabin will be minimized by controlling the vibrations in the hull, in this way the active engine mounts only isolates the vibrations that couples good to the sound radiated. This paper will present the key results from the tests with the combined passive/active engine mounts on board the boat.
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| 903. |
- Winberg, Mathias, et al.
(författare)
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Active Control of Engine Vibrations in a Collins Class Submarine
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Submarine manufacturers invest considerable effort and money in improving the attenuation of noise radiated by submarines into the water. A number of different noise sources contribute to the total acoustic signature on an advanced submarine, such as the Collins Class. This report focuses on the problem associated with low order harmonics generated by the main diesel engines, transmitted through the engine mounts into the hull, and subsequently radiating into the water. The diesel engine mount consists of a two stage isolation system with a large intermediate mass, weighing approximately $500$ kg. Each engine is attached to the hull by eight mounts. The main intention of the work described here is to experimentally investigate the use of active vibration control to minimize the vibratory energy of the intermediate mass in all six degrees of freedom, thereby also minimizing the vibratory energy transmitted to the hull. This approach involves the use of seven inertial actuators, mounted on the intermediate mass, to produce the cancelling vibration field. A test rig, similar to one of the diesel engine mounts on the actual submarine, was constructed in the laboratory at The University of Adelaide and used for the real-time active control experiments described here. Several different set-ups were evaluated using primary vibrations with the same absolute levels and frequency content as measured on board a Collins class submarine. The controller used in the real-time experiments is based on the filtered X-LMS algorithm, which is a feed-forward algorithm working in the time domain.It is demonstrated here that active vibration control of the intermediate mass of the existing diesel engine mounts is a practical way of reducing the 1.0, 1.5 and 2.0 engine order components in the noise spectrum radiated as a result of vibration transmission through the engine mounts.
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| 904. |
- Winberg, Mathias, et al.
(författare)
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An Active Headset Based on Hybrid Active Noise Control Technology
- 2001
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Konferensbidrag (refereegranskat)abstract
- In helicopters, the low frequency noise generated by the rotors and engines often masks and jeopardizes safe communication. In addition, pilots are likely to su?er from damage to their hearing due to the high sound levels in the headset produced to overcome the noise caused by increased speaker levels. A feasible approach is to reduce the low frequency noise by using active techniques combined with a method for reducing the noise in the intercom microphone signal, with lower speaker levels as a result. Helicopter noise consists of tonal components embedded in broadband noise. In order to achieve an e?cient attenuation of the primary noise inside the headset, a combination of a digital feedforward controller and an analog feedback controller is employed. Spectral Subtraction is used to suppress the background noise in speech signals. This paper evaluates a combination of the two techniques and their application to real data.
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| 905. |
- Winberg, Mathias, et al.
(författare)
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CONTROL APPROACHES FOR ACTIVE NOISE AND VIBRATION CONTROL IN A NAVAL APPLICATION
- 2000
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Konferensbidrag (refereegranskat)abstract
- Engine induced sound and vibration levels in commercial and leisure boats is in many cases unacceptably high in terms of passenger comfort and environmental noise. Classical methods of passive treatment are generally less effective due to the low frequency noise content, and often lead to an increase in structural weight. This than contradicts the low weight requirements for increased travel speed. More efficient vibration damping methods must therefore be found. With active engine mounts, it is possible to achieve a decrease in the vibrations even when the hull is not very stiff. This is especially important in marine applications since the engines are mounted on weak and light structures. The AVIIS (Active Vibration Isolation In Ships) project aims at investigating the effects of a combined passive/active engine mount for use in boats. A Storebro 36 Royal Cruiser with two Volvo Penta engines has been used in the project. This paper presents a comparison between a local vibration control at each engine mount contra a more global acoustic control, a ASAC (Active Structure Acoustic Control) approach. The advantage of acoustic control is that only the vibrations that couple strongly to the sound radiated will be attenuated. This also leads to a decrease in power consumption, which is important in a vessel. The calculations are based on real data from the Storebro boat.
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| 906. |
- Winberg, Mathias, et al.
(författare)
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INERTIAL MASS ACTUATORS, UNDERSTANDING AND TUNING
- 2004
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Konferensbidrag (refereegranskat)abstract
- The actuators, the error sensors and the control system are central components in active noise and vibration control systems. The actuators produce the secondary forces acting on the structure while the error sensors measure the quantity to be minimized. Inertial mass actuators are used frequently in a variety of applications, e.g. boat engine mounts and airplane fuselages. To tune the inertial mass actuator to fit a certain application or just to understand the manufactures specification it is important to have an understanding of the construction of the actuator and the equations describing it. This paper presents a mathematical model of the mechanical and electrical system for the inertial mass actuator. A mobility analogy is introduced in order to determine how the inertial mass and the spring constant of the suspension effect the resonance frequency of the actuator as well as the output force. Does the mobility of the structure, the actuator is mounted on, effect the produced output force in relationship to the rated force of the actuator? Practical measurement results are presented in order to determine the resonance frequency and output force of an inertial mass actuator manufactured by Metravib in France.
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| 907. |
- Winter, Jeff
(författare)
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Law, knowledge and mobility in local planning
- 2004
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Konferensbidrag (refereegranskat)abstract
- Interpretation of the law is important in the administrative decision-making process in local municipal planning, which is a co-operative process. Local mobility also plays an important role. A study of work practice highlights the need to take this into account when designing support for decision-making processes.
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| 908. |
- Wohlin, Claes, et al.
(författare)
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An evaluation of checklist-based reading for entity-relationship diagrams
- 2003
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Konferensbidrag (refereegranskat)abstract
- Software inspections have attracted much attention over the last 25 years. It is a method for static analysis of artifacts during software development. However, few studies look at inspections of entity-relationship diagrams (ER diagrams), and in particular an evaluation of the number of defects, number of false-positives and the types of defects that are found by most reviewers. ER-diagrams are commonly used in the design of databases, which makes them an important modelling concept for many large software systems. We present a large empirical study (486 subjects) where checklists were used for an inspection. The goodness in the evaluation is judged based on the type of defects the reviewers identify and the relationship between the detection of real defects and false positives. It is concluded that checklist-based inspections of entity-relationship diagrams is worthwhile.
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| 909. |
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| 910. |
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