Active Control of Finite Beam Volume Velocity using Shaped PVDF Sensor
Abstract:The radiated sound power of a planar structure is related to the structural volume velocity in the low frequency region. The volume veloctiy associated with a vibration structure is also related to the far-field pressure in the direction orthogonal to that structure. Thus, the minimization of the volume velocity appears as a good strategy for active control of sound radiation. This paper investigates the design of a volume velocity sensor and its integration into an active noise control system in the case of a flexural beam (1D structure). Based on a modal approach, the shape of a PVDF sensor is analytically determined in such a way that the output signal of the sensor is directly proportional to the volume velocity of a harmonically excited finite beam with arbitrary boundary conditions. A general expression of the PVDF sensor shape is obtained and is shown to depend only on the beam and sensor characteristics (material characteristics and boundary conditions). The shape of the sensor is independent of the type and position of the excitation and the control actuator considered. For simply supported or clamped boundary conditions, this type of shaped PVDF sensor detects only contributions from the odd (symmetric) modes, which arw the only ones with non-zero volume velocity and also the most effective radiators. For a cantilever beam, this sensor will detect all the modes since none of them has zero volume velocity. A piezoceramic actuator is used to minimize the output signal of the shaped PVDF sensor. The efficiency of this control strategy is demonstrated analytically for a simply-supported and cantilever beam. The far-field radiated acoustic power, the quadratic velocity as well as the radiation efficiency are extensively studied. The results show that such PVDF shaped sensor is very effective in controlling the sound radiation. Experimental implementation of such a PVDF volume velocity sensor as well as the active control using a feedforward harmonic adaptive LMS algorithm are presented and discussed.
Document Type: Research Article
Publication date: September 1, 1996
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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