Browsing by Subject "active noise control"

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Access status: Open Access ,
Active noise and vibration control system design considerations
(Wydawnictwa AGH, 2007) Hansen, Colin H.; Qiu, Xiaojun; Petersen, Cornelis; Howard, Carl Q.; Singh, Sarabjeet
When designing active control systems to reduce noise radiated by vibrating surfaces, there are many variables that need to be optimised to achieve the maximum possible system performance. There are also a number of hardware and software aspects that must be considered and accounted for when a laboratory system is adapted for operation in an industrial or commercial environment. There needs to be some sort of hierarchy in the approach to optimising the many variables which include type, locations and numbers of control sources, quality of the reference signal for feedforward systems, software structure and algorithm considerations and hardware architecture considerations. This paper discuses a number of issues associated with the implementation of active noise and vibration control systems that have been the subject of investigation at The University of Adelaide.
Access status: Open Access ,
Feed-forward compensation for nonlinearity of vibrating plate as the sound source for active noise control
(2011) Mazur, Krzysztof; Pawełczyk, Marek
Active Noise Control (ANC) systems are usually designed in the feed-forward structure with adaptive linear control filters. However, performance of such systems, when a vibrating plate is used as the secondary source, may be poor due to significant non-linearity of the plate response. The linear systems are then unable to cope with higher harmonics generated by the nonlinearity. One solution to this problem is to apply a nonlinear ANC algorithm. However, it adds additional complexity to this layer. It is particularly severe for multichannel systems, where the algorithms are complex by themselves, and making them nonlinear may significantly reduce their scalability. In this paper, another approach is proposed. Multiple actuators are mounted on a single plate, in order to effectively excite more vibration modes and generate a higher acoustic power, than in case of a single actuator. The response of the vibrating plate as the sound source is then linearized with a set of nonlinear finite impulse response filters, operating individually for each actuator. The Filtered-x LMS algorithm is adopted to update parameters of the nonlinear filters. The control system is experimentally verified and obtained results are reported.
Access status: Open Access ,
Feed-forward equalization of sound radiation from a vibrating plate
(2012) Mazur, Krzysztof; Pawełczyk, Marek
In this paper an adaptive single input - multiple output feed-forward system for sound radiation from a vibrating plate is investigated. Finite impulse response filters are used to generate control signals for each actuator based on the common input signal. The filters are updated with the Filtered-x LMS algorithm in order to minimize the instantaneous squared value of the difference between the sound pressure measured at the specified point in the acoustic field, and the desired signal being the input signal filtered by the assumed secondary path transfer function model. Performance of the system is experimentally verified and obtained results are reported.
Access status: Open Access ,
Gain-scheduled state-feedback control for active cancellation of multisine disturbances with time-varying frequencies
(2011) Heins, Wiebke; Ballesteros, Pablo; Bohn, Christian
The paper presents a discrete-time LTV controller for the rejection of harmonic disturbances with time-verying based on a state-augmented observer-based state-feedback controller with a time-verying internal model and a scheduled state-feed back gain. The control design method is based on quadratic stability for LPV systems. The design is carried out in discrete time and the controller can easily be implemented on real-time hardware.
Access status: Open Access ,
Model - based active noise control of a piezoelectric structure
(Wydawnictwa AGH, 2007) Nestorović, Tamara; Lef?vre, Jean; Gabbert, Urlich
Methods of active noise and vibration control involve different techniques which combine electroacoustics with integration of active materials and controller into a complex active structural system in order to enable radiation of an anti-phased field for cancellation or attenuation of an original noise in a specific domain. This paper presents a model-based controller design procedure for the active noise attenuation of a piezoelectric structure surrounded by the acoustic fluid. Model development is based on a finite element method approach, which takes into consideration the electro-mechanical-acoustic effects. A FEM-based state-space model obtained after appropriate transformations and modal reduction is used for the controller design. The aim of the control, suppression of the acoustic fluid pressure in a prescribed point or field, is achieved using an optimal LQ controller designed based on a developed state-space model. The controller design involves also a novel approach, with included additional dynamics for the noise control in the presence of periodic excitations. The effects of the suggested method are tested on a smart acoustic box consisting of an aluminium plate with attached piezoelectric patches, surrounded by the acoustic fluid (air) inside the wooden box. The air pressure reduction at a selected point inside the box is observed in the controlled case.
Access status: Open Access ,
Model identification for active noise control in the presence of primary noise
(Wydawnictwa AGH, 2005) Kasprzyk, Jerzy
A problem of electro-acoustic plant identification for active noise control is discussed. It is assumed that data from identification experiment are contaminated by a primary noise that should be attenuated later. Three examples of such a noise are considered: sine (discrete spectrum), noise generated by a motor (narrowband time-varying spectrum) and broadband noise (pseudorandom). It is shown that thanks to preprocessing the data by disturbance adjusting filtration (DAF) it is possible to improve the results significantly when the data are contaminated by a narrowband primary noise. DAF is the procedure of selective filtration in frequency domain consisting in removing from the spectra all lines for frequencies corresponding to the noise. The results of real-world experiments carried on in a laboratory enclosure show the accuracy of estimated frequency responses obtained in the proposed approach. The procedure is efficient when multisine signals are used to excite the plant.
Access status: Open Access ,
Multi-channel virtual-microphone feedback minimum-variance active noise control system
(Wydawnictwa AGH, 2009) Pawełczyk, Marek
Classical active noise control systems are designed to minimise, in a sense, the residual signal at the microphone providing information about acoustic noise and secondary sound interference. The secondary sound operates at the same time on the acoustic noise at other positions including user ears. In the worst case this can result in sound reinforcement at those positions. In many applications placing another microphone directly at the ears is not accepted. It is then justified to make efforts to design a dedicated system. The purpose is to minimise the mean-square value of the noise at the desired location while performing measurements of sound interference results at another location. This can be done by employing the general idea of Vrtual-Microphone Control systems. However, for many active noise control applications the use of a single pair of microphone and loudspeaker does not suffice to obtain satisfactory performance, i.e. generate a zone of quiet of acceptable dimensions. Moreover, for some applications, presence of an obstacle, e.g. the head in an active headrest system, constitutes a barrier for the zone of quiet at one side to propagate to the other side. Therefore, more microphones and loudspeakers are often necessary. In the most general case a coupling between subsequent pairs should be taken into account resulting in a multi-channel system. In previous papers of the author adaptive systems have been designed and analysed. In this paper a fixed parameter multi-channel Virtual-Microphone Control system, optimal in the mean- square sense, is designed. It includes non-minimum phase property of the system channels. Both the case of more inputs than outputs as well as the case of more outputs than inputs are considered. Factorization techniques have been used for the design. The system is verified by successfully controlling noise for the active headrest system.
Access status: Open Access ,
The active noise control issues related to the noise generated by the power transformers
(Wydawnictwa AGH, 2005) Zawieska, Wiktor Marek
The paper presents vibroacoustic tests of power transformers with regard to active reduction of their noise. Basic sources of vibroacoustic energy are determined and a system of active reduction of noise (ANC) emitted by power transformers, developed by CIOP-PIB, is presented. Moreover, the results of preliminary tests of the system in real conditions are presented.