Browsing by Author "Bai, MSR"

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Active cancellation of noise in a car cabin using the zero spillover controller
(2000-08-31)
Bai, MSR
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Chen, HH
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機械工程學系
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Department of Mechanical Engineering
In active noise control problems, spillover will occur because of the Bode integral constraint if the performance sensors and measurement sensors are collocated, or if the control speakers and the noise sources are collocate, This paper is focused on the implementation of a multiple-channel zero-spillover ANC controller using a spatially feedforward structure for a car cabin. The plant model is realized by using a frequency-domain procedure. The linear-quadratic-Gaussian algorithm is used in controller design. Experiments are carried out to verify the proposed technique, where random noise and engine noise are chosen as the primary noise. The results indicate that the proposed controller yields a broadband attenuation for the random noise. The proposed method is also effective in attenuating the engine noise if an assumed model of the noise is incorporated into controller design. (C) 2000 Academic Press.
Adaptive order tracking technique using recursive least-square algorithm
(2002-10-01)
Bai, MSR
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Jeng, J
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Chen, CY
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機械工程學系
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Department of Mechanical Engineering
Order tracking technique is one of the important tools for diagnosis of rotating machinery Conventional methods of order tracking are primarily based on Fourier analysis with reference to shaft speed. Resampling is generally required in the fast Fourier transform (FFT)-based methods to compromise between time and frequency resolution for varying shaft speeds. Conventional methods suffer from a number of shortcomings. In particular smearing problems arise when closely spaced orders or crossing orders are present. Conventional methods also are ineffective for the applications involving multiple independent shaft speeds. This paper presents an adaptive order tracking technique based on the Recursive Least-Squares (RLS) algorithm to overcome the problems encountered in conventional methods. In the proposed method, the problem is treated as the tracking of frequency-varying bandpass signals. Order amplitudes can be calculated with high resolution by using the proposed method in real-time fashion. The RLS order tracking technique is applicable whether it is a single-axle or multi-axle system.
Background noise cancellation for hands-free communication system of car cabin using adaptive feedforward algorithms
(2003)
Wu, JD
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Lee, TH
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Bai, MSR
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機械工程學系
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Department of Mechanical Engineering
This paper describes the background noise attenuation for hands-free communication systems of car cabins using adaptive feedforward noise control algorithm. For hands-free telephone system, the quality of communication usually is effect by background noise such as engine noise and aerodynamic noise. In the present study, an active noise control (ANC) design for reducing car cabin periodic background noise from engine and broadband random noise using adaptive feedforward control are investigated. The control algorithm is based on the well-known filtered-x least mean square (FXLMS) with multi-sine synthesized reference signal and frequency counting technology is implemented on a digital signal processor (DSP) platform. Experimental results indicated that the proposed design was effective suppressing 15 dB in periodic engine noise and 2-3 dB in broadband random background noise.
Broadband spatially feedforward active noise control algorithms using a comb filter
(2003-01-01)
Bai, MSR
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Lai, JW
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機械工程學系
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Department of Mechanical Engineering
A controller composed of a nonrecursive filter and a recursive filter is used to approximate the ideal controller for a spatially feedforward duct ANC problem. The nonrecursive part represents the dynamics of the transducer, whereas the recursive part is in the form of a comb filter. The parameters of the comb filter are obtained from the impulse response of the controller by using the least-square method. The comb filter is then cascaded with the nonrecursive part implemented as either a fixed filter or an adaptive filter. In the latter approach, two types of LMS-based algorithms are used. The proposed algorithms are implemented on the platform of a digital signal processor Experimental results showed that the approximated controller attained 17 dB maximal attenuation in the frequency band 200similar to600 Hz.
Development and implementation of cross-talk cancellation system in spatial audio reproduction based on subband filtering
(2006-03-07)
Bai, MSR
;
Lee, CC
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機械工程學系
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Department of Mechanical Engineering
An integrated spatial audio system based on subband filtering and a panel speaker array is developed in this paper. This system is intended for a personal computer and is capable of rendering sound images positioned arbitrarily around a listener, synchronizing with the video image. The proposed system features the spatial audio technologies such as the head-related transfer function (HRTF), the reverberator, and the cross-talk cancellation system (CCS). Of particular importance in this paper is that inverse filtering with Tikhonov regularization technique is employed in designing the multi-channel filters to cancel the crosstalks. To ease the computation loading, the CCS is implemented for frequencies below 5.5 kHz by using a subband filtering approach. The system is implemented on a 5 x I panel speaker array. Experimental investigation indicated that the proposed system is effective in creating an immersive sound field, in complement with video rendering. (c) 2005 Elsevier Ltd. All rights reserved.
Development of an on-line diagnosis system for rotor vibration via model-based intelligent inference
(2000-01-01)
Bai, MSR
;
Hsiao, I
;
Tsai, HM
;
Lin, CT
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機械工程學系
An on-line fault detection and isolation technique is proposed for the diagnosis of rotating machinery. The architecture of the system consists of a feature generation module and a fault inference module. Lateral vibration data are used for calculating the system features. Both continuous-time and discrete-time parameter estimation algorithms are employed for generating the features. A neural fuzzy network is exploited for intelligent inference of faults based on the extracted features. The proposed method is implemented on a digital signal processor. Experiments carried out for a rotor kit and a centrifugal fan indicate the potential of the proposed techniques in predictive maintenance. (C) 2000 Acoustical Society of America. [S0001-4966(00)03201-X].
Development of panel loudspeaker system: Design, evaluation and enhancement
(2001-06-01)
Bai, MSR
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Huang, TL
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機械工程學系
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Department of Mechanical Engineering
Panel speakers are investigated in terms of structural vibration and acoustic radiation. A panel speaker primarily consists of a panel and an inertia exciter. Contrary to conventional speakers, flexural resonance is encouraged such that the panel vibrates as randomly as possible. Simulation tools are developed to facilitate system integration of panel speakers. In particular, electro-mechanical analogy, finite element analysis, and fast Fourier transform are employed to predict panel vibration and the acoustic radiation. Design procedures are also summarized. In order to compare the panel speakers with the conventional speakers, experimental investigations were undertaken to evaluate frequency response, directional response, sensitivity, efficiency, and harmonic distortion of both speakers. The results revealed that the panel speakers suffered from a problem of sensitivity and efficiency. To alleviate the problem, a woofer-using electronic compensation based on H-2 model matching principle is utilized to supplement the bass response. As indicated in the result, significant improvement over the panel speaker alone was achieved by using the combined panel-woofer system. (C) 2001 Acoustical Society of America.
DSP implementation of an active bearing mount for rotors using hybrid control
(2000-10-01)
Bai, MSR
;
Luo, WB
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機械工程學系
;
Department of Mechanical Engineering
An on-line active technique for suppressing rotor vibration is proposed Electromagnetic actuators are mounted on the housing of a ball bearing for generating counter forces to cancel the transverse vibrations due to imbalance, misalignment, and so forth. Controllers based on feedback structure, feedforward structure and hybrid structure are investigated. The multiple channel active control systems are implemented on the platform of a digital signal processor. Numerical simulation and experimental investigations indicate that the proposed methods are effective irt suppressing the periodic disturbances. In particular, the hybrid control by using feedback linear quadratic gaussian control and feedforward least mean square algorithm with synthetic reference achieves the best performance in terms of vibration attenuation and convergence speed. [S0739-3717(00)00904-1].
Estimation of sound power of baffled planar sources using radiation matrices
(2002-09-01)
Bai, MSR
;
Tsao, MC
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機械工程學系
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Department of Mechanical Engineering
A technique is presented in this paper for the analysis of acoustic radiation of baffled planar sources. This method is based on the concept of the radiation matrix which is a representation of the sound field radiated by complex sources. Both sound power and far-field pressure can be estimated using this method. Numerical simulation and experimental investigation were carried out to verify the proposed method. In comparison with the conventional pressure-based method ISO 3745. the proposed technique produced more accurate estimation of sound power. With comparable number of measuring positions as the conventional methods, the proposed approach does not require special measuring environments. Computation complexity can be significantly reduced if only dominant radiation modes in the low-frequency range are retained. Estimation of far-field pressure can also be obtained using the proposed method. (C) 2002 Acoustical Society of America.
Optimization and implementation of piezoelectric radiators using the genetic algorithm
(2003-06-01)
Bai, MSR
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Huang, CH
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機械工程學系
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Department of Mechanical Engineering
Very thin and small (45 mm x 35 mm x 0.35 mm) piezoelectric radiators have been developed in this research. The system is modeled by using the energy method in conjunction with the assumed-modes method. Electrical system, mechanical system, and acoustic loading have all been accounted for during the modeling stage. On the basis of the simulation model, the genetic algorithm (GA) is employed to optimize the overall configurations for a low resonance frequency and a large gain. The resulting designs are then implemented and evaluated experimentally. Performance indices for the experimental evaluation include the frequency response, the directional response, the sensitivity, and the efficiency. It is found in the experimental results that the piezoelectric radiators are able to produce comparable acoustical output with significantly less electrical input than the voice-coil panel speakers. (C) 2003 Acoustical Society of America.
Study of the acoustic feedback problem of active noise control by using the l(1) and l(2) vector space optimization approaches
(1997-08-01)
Bai, MSR
;
Wu, TY
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交大名義發表
;
機械工程學系
;
National Chiao Tung University
This study attempts to explore the acoustic feedback problem that is frequently encountered in feedforward active noise control (ANC) structure from the standpoint of control theories. The analysis is carried out on the basis of the Youla's parametrization and the l(1)-norm and l(2)-norm vector space optimization. The ANC problem is formulated as a model matching procedure and is solved via linear programming in the dual vector space. These methods alleviate the problems caused by the nonminimum phase (NMP) zeros of the cancellation path. The ANC algorithms are implemented by using a digital signal processor. Various types of noises were chosen for validating the developed algorithms. The proposed methods are also compared with the well-known filtered-u least-mean square (FULMS) method, The experimental results show that the acoustic feedback problem significantly degrades the performance and stability of the ANC system regardless which method is used. Insights into the difficulties due to acoustic feedback are addressed along the line of control theories. (C) 1997 Acoustical Society of America.
Synthesis of a robust broadband duct ANC system using convex programming approach
(2002-04-01)
Bai, MSR
;
Zeung, PS
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機械工程學系
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Department of Mechanical Engineering
A robust active controller using spatially feedforward structure is proposed for broadband attenuation of noise in ducts. To meet the requirements of performance and robust stability in the presence of plant uncertainties, an H-2 cost function and an H. constrain are employed in the synthesis of the controller. The design is then converted into a convex programming problem using Q-parametrization and frequency discretization. An optimal controller that satisfies the quadratic cost functions and linear inequality constraints can be found by sequential quadratic programming. The optimal controller was implemented via a digital signal processor (DSP) and verified by experiments. Experiment results showed that the system attained 16.5 dB maximal attenuation and 5.9 dB total attenuation in the frequency band 200-600 Hz. (C) 2002 Acoustical Society of America.
The system-on-chip design of a silicon micromachined condenser microphone array
(2004-07-01)
Bai, MSR
;
Huang, SW
;
機械工程學系
;
Department of Mechanical Engineering
A miniature condenser microphone array that combines array signal processing and micro-electro-mechanical systems (MEMS) technologies is presented. A linear dynamic model and a quasistatic analysis are presented. The array configuration serves two purposes: enhancement of the signal-to-noise ratio (SNR) and the directivity of sensor. A least-squares beamforming design based on the template resulting from the Multiple Signals Classification algorithm is proposed to achieve a directive beam pattern. To minimize the parasitic effects on the MEMS device, a system-on-chip design composed of a microphone module, a dc bias circuit, an impedance matching circuit, and array beamforming filters is proposed in the paper. The performance of the proposed design is evaluated in terms of the frequency response, SNR improvement, and directional response through numerical simulations and experiments. (C) 2004 Acoustical Society of America.